Phospholipase

D

signaling

orchestration

by

and

small

GTPases

Hydrolysis

of

phosphatidylcholine

by

phospholipase

D

-LRB-

PLD

-RRB-

leads

to

the

generation

of

the

versatile

lipid

second

messenger

phosphatidic

acid

-LRB-

PA

-RRB-

which

is

involved

in

fundamental

cellular

processes

including

membrane

trafficking

actin

cytoskeleton

remodeling

cell

proliferation

and

cell

survival

PLD

activity

can

be

dramatically

stimulated

by

a

large

number

of

cell

surface

receptors

and

is

elaborately

regulated

by

intracellular

factors

including

protein

kinase

C

isoforms

small

GTPases

of

the

ARF

Rho

and

Ras

families

and

particularly

by

the

phosphoinositide

phosphatidylinositol

-LRB-

-RRB-

is

well

known

as

substrate

for

the

generation

of

second

messengers

by

phospholipase

C

but

is

now

also

understood

to

recruit

and/or

activate

a

variety

of

actin

regulatory

proteins

ion

channels

and

other

signaling

proteins

including

PLD

by

direct

interaction

The

synthesis

of

by

phosphoinositide

-LRB-

-RRB-

isoforms

is

tightly

regulated

by

small

GTPases

and

interestingly

by

PA

as

well

and

the

concerted

formation

of

and

PA

has

been

shown

to

mediate

receptor-regulated

cellular

events

This

review

highlights

the

regulation

of

PLD

by

membrane

receptors

and

describes

how

the

close

encounter

of

PLD

and

isoforms

with

small

GTPases

permits

the

execution

of

specific

cellular

functions

Introduction

The

activation

of

membrane

receptors

by

hormones

and

growth

factors

results

in

the

localized

generation

of

intracellular

second

messengers

The

hydrolysis

of

membrane

phospholipids

and

the

generation

of

biologically

active

products

play

important

roles

in

the

regulation

of

cell

function

and

cell

fate

Well

known

is

the

activation

of

phosphoinositide-specific

phospholipase

C

-LRB-

PLC

-RRB-

isoforms

which

hydrolyze

phosphatidylinositol

-LRB-

-RRB-

a

membrane

phospholipid

found

in

all

eukaryotic

cells

-LRB-

Schmidt

et

al.

-RRB-

Stimulation

of

PLC

isoforms

plays

a

major

role

in

many

early

and

late

cellular

responses

to

receptor

activation

including

smooth

muscle

contraction

secretion

and

neuronal

signaling

as

well

as

fertilization

cell

growth

and

differentiation

-LRB-

Berridge

Nishizuka

-RRB-

Phospholipase

D

-LRB-

PLD

-RRB-

was

first

described

years

ago

as

a

distinct

phospholipid-specific

phosphodiesterase

activity

in

cabbage

leaves

-LRB-

Hanahan

and

Chaikoff

-RRB-

This

pioneering

research

indicated

that

PLD

hydrolyzes

phosphatidylcholine

to

yield

phosphatidic

acid

-LRB-

PA

-RRB-

and

choline

The

recognition

that

PLD

is

rapidly

and

dramatically

activated

in

response

to

extracellular

stimuli

in

cultured

animal

cells

now

years

ago

-LRB-

Bocckino

et

al.

Cockcroft

-RRB-

has

brought

PLD

signaling

to

the

very

forefront

of

current

biological

and

biomedical

research

Meanwhile

phosphatidylcholine-hydrolyzing

PLD

has

been

identified

in

bacteria

protozoa

fungi

plants

and

animals

and

due

to

this

widespread

distribution

is

assumed

to

be

involved

in

the

regulation

of

fundamental

cellular

functions

Indeed

it

has

now

been

established

that

activation

of

PLD

and

the

generation

of

PA

by

a

vast

number

of

membrane

receptors

modulate

such

a

wide

array

of

cellular

responses

as

calcium

mobilization

secretion

superoxide

production

endocytosis

exocytosis

vesicle

trafficking

glucose

transport

rearrangements

of

the

actin

cytoskeleton

mitogenesis

and

survival

-LRB-

Cockcroft

Exton

Jenkins

and

Frohman

Liscovitch

et

al.

-RRB-

is

a

critical

cofactor

for

PLD

and

profoundly

affects

the

activity

membrane

localization

and

receptor

activation

of

both

PLD

isoforms

and

-LRB-

Brown

et

al.

Hodgkin

et

al.

Liscovitch

et

al.

Pertile

et

al.

Schmidt

et

al.

-RRB-

Thus

reduction

of

cellular

levels

for

instance

via

scavenging

of

by

the

actin-binding

protein

fodrin

-LRB-

Lukowski

et

al.

-RRB-

or

via

forced

hydrolysis

by

the

phosphatase

synaptojanin

-LRB-

Chung

et

al.

-RRB-

has

been

shown

to

inhibit

PLD

activity

Vice

versa

the

synthesis

of

by

phosphoinositide

-LRB-

-RRB-

isoforms

can

be

directly

stimulated

by

the

PLD

product

PA

-LRB-

Jenkins

et

al.

Moritz

et

al.

-RRB-

and

this

regulation

has

also

been

confirmed

to

occur

at

the

whole

cell

level

-LRB-

Divecha

et

al.

Jones

et

al.

Skippen

et

al.

-RRB-

It

is

now

hypothesized

that

the

reciprocal

stimulation

of

PLD

and

enzymes

enables

rapid

feed-forward

stimulation

loops

for

a

localized

and

explosive

generation

of

PA

and

which

may

then

govern

the

recruitment

and

activation

of

proteins

to

execute

specific

cellular

tasks

especially

membrane

trafficking

and

changes

in

the

organization

of

the

actin

cytoskeleton

The

activity

and

localization

of

both

PLD

and

are

under

control

of

GTPases

of

the

Arf

and

Rho

families

which

are

well-defined

regulators

of

membrane

transport

and

actin-reorganization

processes

The

reciprocal

stimulation

of

and

PLD

and

the

regulation

of

these

enzymes

by

ARF

and

Rho

GTPases

point

to

concerted

mechanisms

in

cellular

actions

involving

acute

localized

and

PA

synthesis

-LRB-

Fig.

-RRB-

This

review

will

focus

on

the

regulation

of

PLD

enzymes

by

membrane

receptors

and

monomeric

GTPases

and

on

how

PLD

signaling

is

organized

and

connected

by

metabolism

Fig.

and

cellular

roles

of

PLD

and

Regulation

of

PLD

and

by

ARF

and

Rho

family

GTPases

is

essentially

involved

in

the

regulation

of

intracellular

vesicle

trafficking

and

actin

cytoskeleton

reorganization

Both

PLD

and

are

stimulated

by

cell

surface

receptors

and

by

conventional

PKC

isoforms

and

the

latter

can

become

activated

after

receptor-induced

hydrolysis

of

by

PLC.

Positive

feed-forward

regulation

is

achieved

by

stimulation

of

PLD

by

and

of

by

PLD-derived

PA.

Activation

of

ARF-GAPs

by

accelerates

the

inactivation

of

ARF

proteins

and

may

terminate

a

round

of

PA

and

synthesis

Phosphatidic

acid

and

PLD

isoforms

Most

cellular

responses

following

PLD

activation

are

probably

mediated

by

the

immediate

reaction

product

PA.

PA

is

a

multifunctional

lipid

that

can

be

further

metabolized

to

the

bioactive

lipids

lysophosphatidic

acid

-LRB-

LPA

-RRB-

and

diacylglycerol

-LRB-

DAG

-RRB-

can

by

itself

alter

membrane

curvature

and

can

serve

as

a

protein

attachment

site

and

affect

both

cellular

localization

and

activity

of

various

proteins

including

kinase

protein

phosphatase

sphingosine

kinase

and

mTOR

-LRB-

mammalian

target

of

rapamycin

-RRB-

a

key

regulator

of

cell

growth

and

proliferation

-LRB-

Jenkins

and

Frohman

-RRB-

PLD

enzymes

can

catalyze

a

transphosphatidylation

reaction

in

which

the

phosphatidyl

moiety

of

phosphatidylcholine

is

accepted

by

primary

alcohols

thereby

producing

stable

phosphatidylalcohol

instead

of

PA.

This

transphosphatidylation

reaction

is

widely

applied

to

measure

PLD

activity

in

biological

samples

and

quenching

of

PA

synthesis

by

primary

alcohols

has

proven

extremely

helpful

to

identify

the

involvement

of

PLD

enzymes

in

cell

physiology

In

this

way

a

role

for

PLD

has

been

demonstrated

in

a

variety

of

signaling

processes

such

as

activation

of

phosphoinositide

-LRB-

-RRB-

and

protein

-LRB-

Akt

-RRB-

kinases

calcium

mobilization

cytoskeleton

remodeling

endocytosis

exocytosis

membrane

trafficking

superoxide

production

glucose

transport

cell

migration

cell

proliferation

and

survival

signaling

-LRB-

Exton

Foster

and

Xu

-RRB-

There

are

two

mammalian

PLD

genes

and

has

a

low

basal

activity

and

is

extensively

regulated

by

conventional

protein

kinase

C

-LRB-

PKCα

β

γ

-RRB-

isozymes

and

small

GTPases

of

the

ARF

-LRB-

-RRB-

and

Rho

-LRB-

RhoA

-RRB-

families

-LRB-

Henage

et

al.

-RRB-

has

a

higher

basal

activity

than

but

has

been

shown

to

respond

to

ARF

and

PKC

as

well

-LRB-

Chen

and

Exton

-RRB-

is

recognized

to

be

the

most

important

cofactor

for

PLD

and

both

PLD

isoforms

are

absolutely

dependent

on

for

activity

Experiments

utilizing

inactive

PLD

mutants

and

RNA

interference

have

discriminated

isoform-specific

PLD

functions

and

showed

that

is

involved

in

agonist-induced

secretion

actin

organization

and

cell

adhesion

and

migration

-LRB-

Exton

Iyer

et

al.

Kim

et

al.

Vitale

et

al.

-RRB-

and

in

endocytosis

and

recycling

of

membrane

receptors

-LRB-

Du

et

al.

Koch

et

al.

Padrón

et

al.

-RRB-

The

PLD

isoforms

both

with

two

splice

variants

share

an

amino-acid

sequence

identity

-LRB-

Colley

et

al.

Hammond

et

al.

Steed

et

al.

-RRB-

The

catalytic

core

of

both

PLD

enzymes

are

composed

of

four

conserved

domains

-LRB-

domain

I-IV

-RRB-

and

the

HKD

motifs

in

the

domains

II

and

IV

probably

associate

together

to

form

a

catalytic

centre

-LRB-

Xie

et

al.

-RRB-

is

characterized

by

a

acid

loop

region

following

domain

II

which

has

been

proposed

to

function

as

a

negative

regulatory

element

-LRB-

Sung

et

al.

-RRB-

and

further

possess

N-terminal

PH

-LRB-

pleckstrin

homology

-RRB-

and

PX

-LRB-

phox

homology

-RRB-

domains

binds

to

the

PH

domain

-LRB-

Hodgkin

et

al.

-RRB-

but

also

to

a

polybasic

binding

motif

within

the

catalytic

core

-LRB-

Sciorra

et

al.

-RRB-

and

interaction

of

with

both

domains

has

been

suggested

to

be

involved

in

membrane

targeting

of

PLD

as

well

as

stimulation

of

PLD

catalytic

activity

-LRB-

Du

et

al.

Hodgkin

et

al.

Sciorra

et

al.

-RRB-

The

PX

domain

of

has

been

reported

to

preferentially

bind

to

phosphatidylinositol-3,4,5-trisphosphate

-LRB-

-RRB-

-LRB-

Lee

et

al.

Stahelin

et

al.

-RRB-

but

interaction

with

has

been

observed

as

well

-LRB-

Du

et

al.

-RRB-

Recently

it

was

shown

that

the

PX

domain

of

PLD

has

GTPase-activating

protein

-LRB-

GAP

-RRB-

activity

towards

dynamin

and

that

PLD

supports

EGF

receptor

endocytosis

-LRB-

Lee

et

al.

-RRB-

The

PH

and

PX

domains

probably

contribute

to

the

proper

localization

of

the

PLD

enzymes

within

cells

In

line

with

a

role

for

PLD

enzymes

in

different

cellular

tasks

and

show

a

diverse

subcellular

distribution

is

found

throughout

the

cell

but

primarily

localizes

to

perinuclear

endosomes

and

the

Golgi

apparatus

-LRB-

Brown

et

al.

Freyberg

et

al.

Hughes

and

Parker

-RRB-

is

almost

exclusively

present

at

the

plasma

membrane

in

lipid

raft

fractions

-LRB-

Czarny

et

al.

-RRB-

The

localization

of

does

not

seem

to

be

static

and

regulated

translocation

and

recycling

of

the

enzyme

between

cellular

compartments

may

be

crucial

to

its

proper

functioning

In

an

elegant

study

coordinated

subcellular

targeting

of

the

lipid

binding

motifs

has

been

demonstrated

to

drive

this

subcellular

cycling

of

-LRB-

Du

et

al.

-RRB-

Upon

stimulation

was

found

to

translocate

from

the

intracellular

compartments

to

the

plasma

membrane

and

this

process

was

probably

dependent

on

the

polybasic

binding

site

The

PH

domain

then

facilitated

entry

of

into

lipid

rafts

a

step

critical

for

internalization

of

the

enzyme

whereafter

interaction

of

the

PX

domain

with

may

control

the

efficient

return

of

to

the

endosomes

and

isoforms

is

an

essential

and

versatile

factor

in

cellular

signaling

Hydrolysis

of

by

PLC

into

the

second

messengers

-LRB-

-RRB-

and

DAG

is

a

general

and

well-defined

answer

of

cells

in

response

to

stimulation

of

many

membrane

receptors

-LRB-

Schmidt

et

al.

-RRB-

Phosphorylation

of

by

results

in

the

rapid

accumulation

of

which

recruits

and

activates

mediators

involved

in

actin

remodeling

mitogenesis

and

survival

-LRB-

Vanhaesebroeck

et

al.

-RRB-

But

it

is

now

recognized

that

as

well

as

other

phosphoinositides

are

signaling

molecules

by

themselves

and

can

by

binding

to

unique

phosphoinositide-binding

sequences

such

as

the

PH

and

PX

domains

affect

the

activity

and

subcellular

localization

of

many

proteins

including

many

actin

regulatory

proteins

a

wide

range

of

ion

channels

and

PLD

-LRB-

Niggli

Suh

and

Hille

Yin

and

Janmey

-RRB-

In

this

way

can

modulate

a

remarkable

variety

of

cellular

processes

including

cortical

actin

organization

membrane

ruffling

vesicle

trafficking

gene

expression

cell

migration

and

cell

survival

-LRB-

Ling

et

al.

Oude

Weernink

et

al.

Toker

-RRB-

Subsequent

dephosphorylation

of

by

inositol

polyphosphate

such

as

synaptojanin

is

believed

to

terminate

local

signaling

for

instance

in

the

process

of

vesicle

trafficking

-LRB-

Majerus

et

al.

-RRB-

To

execute

this

variety

of

functions

may

be

organized

in

discrete

functional

pools

within

cells

but

the

existence

of

clusters

in

the

plasma

membrane

is

currently

under

debate

Using

green

fluorescent

protein-tagged

PH

domains

or

antibodies

to

visualize

the

lipid

was

found

to

concentrate

in

highly

dynamic

actin-rich

regions

-LRB-

Tall

et

al.

-RRB-

and

lipid

rafts

-LRB-

Laux

et

al.

Parmryd

et

al.

-RRB-

in

the

plasma

membrane

feeding

the

idea

that

spatially

organized

synthesis

regulates

actin

polymerization

and

other

cellular

processes

The

localization

of

in

rafts

is

supported

by

biochemical

data

-LRB-

Pike

and

Casey

-RRB-

however

specific

clustering

has

been

disputed

-LRB-

van

Rheenen

et

al.

-RRB-

is

generated

after

phosphorylation

of

by

In

mammals

cDNAs

encoding

three

isoforms

of

-LRB-

designated

Iα

Iβ

and

Iγ

-RRB-

with

alternative

splice

variants

have

been

cloned

and

characterized

-LRB-

Ishihara

et

al.

Loijens

and

Anderson

-RRB-

Sequence

analysis

has

shown

that

enzymes

are

related

to

enzymes

but

that

they

share

no

identity

with

most

other

lipid

-LRB-

and

-RRB-

or

protein

kinases

The

sequence

similarity

between

the

and

is

clustered

in

the

catalytic

core

of

the

kinases

-LRB-

Anderson

et

al.

Hinchliffe

et

al.

-RRB-

An

activation

loop

spanning

the

catalytic

domain

has

been

shown

to

determine

both

substrate

specificity

and

subcellular

targeting

of

which

can

be

swapped

by

substitution

of

a

single

amino

acid

within

this

loop

-LRB-

Kunz

et

al.

-RRB-

In

murine

two

dimerization

domains

were

identified

which

may

contribute

to

the

proper

subcellular

localization

and

functioning

of

the

enzyme

-LRB-

Galiano

et

al.

-RRB-

The

identification

of

three

isoforms

raised

the

expectation

of

a

differential

regulation

of

the

enzymes

by

cellular

signal

transduction

components

but

up

to

now

the

regulatory

properties

of

Iβ

and

Iγ

appear

to

be

remarkably

similar

All

isoforms

are

stimulated

by

PA

are

extensively

regulated

by

ARF

and

Rho

GTPases

and

inhibited

by

protein

kinase

A

-LRB-

PKA

-RRB-

and

PI-stimulated

autophosphorylation

-LRB-

Oude

Weernink

et

al.

-RRB-

Nevertheless

evidence

has

been

provided

that

isoforms

may

selectively

control

functional

pools

which

may

support

particular

processes

in

different

cell

types

Thus

actin

reorganization

down-stream

of

in

platelets

specifically

involves

murine

-LRB-

Tolias

et

al.

-RRB-

Human

was

found

to

localize

in

membrane

ruffles

and

the

LIM

protein

Ajuba

has

been

identified

to

interact

with

and

stimulate

in

leading-edge

membrane

ruffles

in

migrating

cells

-LRB-

Kisseleva

et

al.

-RRB-

Human

PIPK-Iβ

was

detected

primarily

in

cytosolic

vesicular

structures

-LRB-

Doughman

et

al.

-RRB-

and

may

synthesize

the

pool

involved

in

constitutive

endocytosis

-LRB-

Padrón

et

al.

-RRB-

The

long-splice

variant

of

is

enriched

in

neurons

and

is

implicated

in

the

regulation

of

clathrin

coat

recruitment

actin

dynamics

-LRB-

Wenk

et

al.

-RRB-

and

focal

adhesion

formation

-LRB-

Di

Paolo

et

al.

Ling

et

al.

-RRB-

In

contrast

short

seems

to

be

the

major

producer

of

the

pool

that

supports

receptor-induced

generation

-LRB-

Wang

et

al.

-RRB-

The

execution

of

specific

processes

is

very

probably

achieved

by

an

orchestration

of

appropriate

signaling

partners

within

discrete

subcellular

microdomains

and

PLD-derived

PA

as

well

as

the

PLD

enzymes

by

themselves

can

contribute

to

this

organization

Indeed

both

and

interact

with

and

recruits

to

a

submembraneous

vesicular

compartment

-LRB-

Divecha

et

al.

-RRB-

PA

was

shown

to

stimulate

splice

variants

and

the

subsequent

formation

of

to

drive

the

initial

stages

of

integrin-mediated

cellular

adhesion

-LRB-

Powner

et

al.

-RRB-

In

many

processes

the

temporal

activation

and

correct

localization

of

PLD

and

isoforms

by

monomeric

GTPases

appears

crucial

to

achieve

the

spatially

organized

production

of

and

PA

-LRB-

Santarius

et

al.

-RRB-

ARF

GTPases

and

membrane

traffic

Although

the

direct

interaction

site

on

PLD

for

ARF

has

not

yet

been

unequivocally

defined

it

is

well

established

that

ARF

proteins

particularly

and

activate

both

PLD

enzymes

but

especially

-LRB-

Hammond

et

al.

-RRB-

ARF

GTPases

regulate

intracellular

vesicle

trafficking

and

actin

remodeling

is

localized

to

the

Golgi

complex

and

is

required

for

proper

Golgi

structure

and

function

The

use

of

primary

alcohols

has

also

pointed

to

a

role

for

PLD

in

vesicle

transport

to

Golgi

-LRB-

Bi

et

al.

Ktistakis

et

al.

-RRB-

PLD

activity

has

been

shown

to

stimulate

the

release

of

nascent

secretory

vesicles

from

the

trans-Golgi

network

-LRB-

Chen

et

al.

-RRB-

and

to

be

required

for

maintaining

the

structural

integrity

and

function

of

the

Golgi

apparatus

but

the

precise

role

for

PLD

in

vesicle

formation

is

still

controversial

is

also

a

direct

effector

of

and

an

mutant

that

selectively

activates

but

not

PLD

activity

demonstrated

that

both

PLD-derived

PA

and

direct

activation

of

by

contribute

to

increased

synthesis

-LRB-

Skippen

et

al.

-RRB-

In

permeabilized

cells

has

been

shown

to

restore

secretion

by

promoting

synthesis

-LRB-

Fensome

et

al.

-RRB-

and

activation

-LRB-

Jones

et

al.

-RRB-

and

recruitment

to

the

Golgi

complex

-LRB-

Godi

et

al.

-RRB-

appears

to

be

critical

in

Golgi

functioning

regulates

vesicular

transport

secretion

and

cortical

actin

reorganization

activates

PLD

and

PA

has

been

implicated

in

the

mediation

of

the

effects

of

in

vesicular

trafficking

events

A

critical

role

for

in

exocytosis

has

been

established

in

different

cell

types

including

neurons

-LRB-

Humeau

et

al.

-RRB-

neuroendocrine

cells

-LRB-

Vitale

et

al.

-RRB-

and

pancreatic

β

cells

-LRB-

Hughes

et

al.

-RRB-

has

recently

emerged

as

a

mediator

of

ARF-dependent

internalization

of

the

μ-opioid

receptor

-LRB-

Koch

et

al.

-RRB-

and

both

PLD

isoforms

have

been

implicated

in

macrophage

phagocytosis

-LRB-

Corrotte

et

al.

Iyer

et

al.

-RRB-

In

addition

colocalizes

and

interacts

with

and

is

directly

activated

by

at

the

plasma

membrane

-LRB-

Honda

et

al.

-RRB-

and

and

colocalize

on

the

plasma

membrane

and

on

endosomal

structures

-LRB-

Brown

et

al.

-RRB-

turnover

at

the

plasma

membrane

is

apparently

involved

in

regulated

secretion

-LRB-

Aikawa

and

Martin

Brown

et

al.

Lawrence

and

Birnbaum

-RRB-

Focal

and

transient

accumulation

of

by

is

required

for

phagocytosis

as

well

-LRB-

Botelho

et

al.

Coppolino

et

al.

Wong

and

Isberg

-RRB-

and

hydrolysis

probably

dictates

the

remodeling

of

actin

necessary

for

completion

of

phagocytosis

-LRB-

Scott

et

al.

-RRB-

The

synthesis

of

is

essential

for

priming

the

exocytotic

apparatus

and

the

recruitment

and

activation

of

by

seems

the

primary

mechanism

for

the

functional

integration

of

into

the

exocytotic

pathway

-LRB-

Vitale

et

al.

Waselle

et

al.

-RRB-

Thus

cytolytic

granule

secretion

mediated

by

was

shown

to

involve

membrane

targeting

and

activation

of

both

and

PLD

-LRB-

Galandrini

et

al.

-RRB-

also

recruits

additional

proteins

for

instance

the

endocytic

proteins

epsin

and

to

initiate

clathrin-coat

formation

preceding

endocytosis

-LRB-

Ford

et

al.

Itoh

et

al.

Padrón

et

al.

-RRB-

and

CAPS

-LRB-

Grishanin

et

al.

-RRB-

to

initiate

dense-core

vesicle

exocytosis

Direct

activation

of

by

has

been

shown

to

stimulate

clathrin-coat

recruitment

to

synaptic

membranes

to

allow

synaptic

vesicle

recycling

-LRB-

Krauss

et

al.

-RRB-

PLD-derived

PA

may

directly

contribute

to

vesicle

fusion

in

a

biophysical

manner

as

PLD

cleaves

the

non-fusogenic

lipid

PC

to

form

the

fusogenic

lipid

PA.

But

PA

also

takes

a

function

as

an

essential

cofactor

for

and

disruption

of

Golgi

membranes

-LRB-

Sweeney

et

al.

-RRB-

blockade

of

clathrin-coat

assembly

-LRB-

Arneson

et

al.

-RRB-

and

inhibition

of

secretion

-LRB-

Way

et

al.

-RRB-

after

quenching

of

PA

production

could

be

attributed

to

inhibited

synthesis

Thus

both

PLD

and

synthesis

seem

necessary

for

membrane

trafficking

aspects

in

the

endo

and

exocytotic

machinery

But

PLD

and

also

mediate

other

processes

down-stream

of

Epidermal

growth

factor

-LRB-

EGF

-RRB-

induced

membrane

ruffling

requires

translocation

to

the

ruffles

and

local

production

This

leads

to

the

recruitment

of

and

PLD-derived

PA

and

may

then

synergistically

activate

-LRB-

Honda

et

al.

-RRB-

The

relationship

between

ARF

and

is

also

bidirectional

as

phosphoinositides

can

regulate

ARF

activity

by

binding

and

activating

both

ARF-specific

guanine

nucleotide

exchange

factors

-LRB-

ARF-GEFs

-RRB-

-LRB-

Klarlund

et

al.

Paris

et

al.

-RRB-

and

ARF-GTPase-activating

proteins

-LRB-

ARF-GAPs

-RRB-

-LRB-

Kam

et

al.

Nie

et

al.

-RRB-

via

their

PH

domains

The

fact

that

ARF-GAPs

bind

with

high

affinity

and

specificity

offers

an

attractive

feed-back

mechanism

for

terminating

ARF

activation

after

a

cycle

of

ARF-induced

synthesis

Rho

GTPases

and

actin

dynamics

PA

formation

especially

by

has

been

reported

to

induce

stress

fibre

formation

in

specific

cell

types

-LRB-

Cross

et

al.

Ha

and

Exton

Kam

and

Exton

Porcelli

et

al.

-RRB-

Rho

proteins

in

particular

RhoA

and

which

control

actin

cytoskeleton

reorganization

exclusively

activate

by

direct

interaction

with

its

C-terminus

-LRB-

Exton

Powner

and

Wakelam

-RRB-

Thus

PLD

stimulation

by

RhoA

may

happen

by

direct

interaction

but

may

involve

indirect

Rho-dependent

mechanisms

as

well

Inactivation

of

Rho

GTPases

with

Clostridium

difficile

toxin

B

or

Clostridium

botulinum

exoenzyme

reduced

cellular

levels

resulting

in

inhibiton

of

receptor-mediated

hydrolysis

by

PLC

-LRB-

Schmidt

et

al.

-RRB-

as

well

as

diminished

PLD

stimulation

-LRB-

Schmidt

et

al.

-RRB-

As

the

inhibition

of

PLD

signaling

after

Rho

inactivation

could

be

largely

rescued

by

the

addition

of

Rho

proteins

do

seem

to

affect

PLD

via

regulation

-LRB-

Schmidt

et

al.

d

-RRB-

is

well-known

to

associate

with

and

regulate

the

activity

of

a

plethora

of

actin-binding

proteins

that

organize

actin

dynamics

-LRB-

Hilpela

et

al.

Yin

and

Janmey

-RRB-

and

PA

and

may

act

in

concert

to

mediate

Rho-dependent

actin

cytoskeleton

remodeling

isoforms

are

like

PLD

under

direct

control

of

Rho

GTPases

isoforms

are

markedly

stimulated

by

RhoA

and

-LRB-

Chong

et

al.

Hartwig

et

al.

Oude

Weernink

et

al.

-RRB-

and

physically

associate

with

both

RhoA

-LRB-

Ren

et

al.

-RRB-

and

-LRB-

Tolias

et

al.

-RRB-

but

not

with

-LRB-

Oude

Weernink

et

al.

van

Hennik

et

al.

-RRB-

isoforms

are

now

seen

as

critical

mediators

of

RhoA

and

actin

organization

and

remodeling

-LRB-

Doughman

et

al.

Shibasaki

et

al.

Tolias

et

al.

-RRB-

The

established

Rho

effector

Rho-kinase

a

serine/threonine

kinase

is

apparently

involved

in

Rho-dependent

regulation

of

both

PLD

-LRB-

Schmidt

et

al.

-RRB-

and

activities

-LRB-

Oude

Weernink

et

al.

-RRB-

and

was

found

to

play

an

essential

role

as

down-stream

effector

of

Rho

and

Rho-kinase

in

neurite

remodeling

-LRB-

van

Horck

et

al.

Yamazaki

et

al.

-RRB-

and

platelet

cytoskeleton

assembly

-LRB-

Gratacap

et

al.

Yang

et

al.

-RRB-

But

Rho

may

also

directly

signal

to

independently

of

Rho-kinase

as

RhoA-induced

activation

of

ERM

-LRB-

ezrin

radixin

moesin

-RRB-

proteins

that

cross-link

actin

filaments

to

plasma

membranes

was

found

to

be

mediated

by

but

not

by

Rho-kinase

-LRB-

Matsui

et

al.

-RRB-

PLD

and

were

also

demonstrated

to

collectively

mediate

Rho-induced

changes

in

the

actin

cytoskeleton

Thus

myogenic

differentiation

induced

by

arginine-vasopressin

which

involves

actin

fiber

formation

is

mediated

by

Rho

proteins

and

and

involves

PLD-induced

synthesis

along

the

actin

fibers

-LRB-

Komati

et

al.

-RRB-

These

findings

suggest

that

PLD

and

enzymes

may

co-operate

down-stream

of

Rho

in

processes

that

depend

on

actin

organization

Another

Rho

effector

PKC-related

protein

kinase

N

-LRB-

PKN

-RRB-

also

directly

interacts

with

PLD

-LRB-

Oishi

et

al.

-RRB-

and

mediates

PLD

activation

by

the

receptor

-LRB-

Parmentier

et

al.

-RRB-

Interestingly

components

of

the

actin

regulatory

machinery

β-actin

and

α-actinin

have

been

found

to

directly

associate

with

and

inhibit

the

activity

of

PLD

isoforms

-LRB-

Lee

et

al.

Park

et

al.

-RRB-

PLD

also

binds

to

and

is

stimulated

by

filamentous

F-actin

and

in

particular

may

act

as

a

signal

transduction

component

responsive

to

dynamic

changes

of

the

actin

cytoskeleton

-LRB-

Kusner

et

al.

-RRB-

PKN

interacts

with

α-actinin

and

PKN

may

modulate

PLD

signaling

by

reversing

the

inhibitory

effect

of

α-actinin

on

and

by

direct

interaction

with

Regulation

of

PLD

and

by

membrane

receptors

In

line

with

the

critical

role

of

PA

in

cellular

processes

the

enzymatic

activity

of

PLD

is

tightly

regulated

by

a

variety

of

hormones

neurotransmitters

and

growth

factors

Regulation

of

PLD

enzymes

by

membrane

receptors

including

G

protein-coupled

receptors

-LRB-

GPCRs

-RRB-

and

receptor

tyrosine

kinases

-LRB-

RTKs

-RRB-

is

complex

and

mediated

by

several

cytosolic

factors

including

PKC

as

well

as

ARF

Rho

and

Ras

GTPases

-LRB-

Exton

Liscovitch

et

al.

López

De

Jesús

et

al.

Powner

and

Wakelam

-RRB-

Most

receptors

that

stimulate

PLD

also

increase

PLC

activity

leading

to

activation

of

the

PLD

regulator

PKC

and

it

was

assumed

that

PLD

activation

might

be

secondary

to

PLC

activation

A

physical

association

between

PLD

with

PKC

isoforms

has

been

reported

resulting

in

strong

activation

of

in

vitro

activity

and

the

major

interaction

site

was

identified

within

the

N-terminus

of

-LRB-

Park

et

al.

-RRB-

Indeed

inhibition

of

PKC

was

shown

to

reduce

receptor-induced

PLD

responses

and

mutants

unresponsive

to

PKC

did

respond

poorly

to

activation

of

GPCRs

-LRB-

Zhang

et

al.

-RRB-

or

to

active

Gαq

proteins

-LRB-

Xie

et

al.

-RRB-

However

stimulation

of

PLD

in

several

receptor

systems

including

muscarinic

and

receptors

was

actually

PKC-independent

-LRB-

Balboa

and

Insel

Muthalif

et

al.

Rümenapp

et

al.

Schmidt

et

al.

-RRB-

suggesting

that

PLD

stimulation

must

not

necessarily

be

secondary

to

PLC

stimulation

Brefeldin

A

an

inhibitor

of

certain

ARF-GEFs

reduced

receptor

signaling

to

PLD

in

several

cell

types

indicating

that

ARF

proteins

participate

in

receptor-mediated

PLD

stimulation

-LRB-

Fensome

et

al.

Mitchell

et

al.

Rümenapp

et

al.

Shome

et

al.

-RRB-

Likewise

sequestration

of

ARF-GEFs

by

the

ARF-related

protein

ARP

inhibited

muscarinic

receptor

signaling

to

PLD

-LRB-

Schürmann

et

al.

-RRB-

Clostridial

toxins

and

enzymes

that

specifically

inactivate

Rho

proteins

and

expression

of

inactive

Rho

mutants

have

been

used

to

identify

the

role

of

Rho

in

signaling

to

PLD

Thus

Rho

proteins

were

found

to

be

involved

in

PLD

stimulation

by

GPCRs

-LRB-

muscarinic

bradykinin

and

LPA

-RRB-

RTKs

-LRB-

PDGF

EGF

-RRB-

and

immunoglobulin

-LRB-

FcεRI

-RRB-

receptors

-LRB-

Hess

et

al.

Ojio

et

al.

Schmidt

et

al.

-RRB-

Stimulation

of

PLD

by

GPCRs

was

shown

to

be

mediated

by

both

pertussis

toxin

-LRB-

PTX

-RRB-

insensitive

-LRB-

Gosau

et

al.

Schmidt

et

al.

-RRB-

and

PTX-sensitive

-LRB-

Cummings

et

al.

Fensome

et

al.

-RRB-

heterotrimeric

G

proteins

family

proteins

can

stimulate

PLD

-LRB-

Plonk

et

al.

-RRB-

and

RGS

-LRB-

regulators

of

G

protein

signaling

-RRB-

proteins

that

act

as

α

subunit-specific

GAPs

have

been

used

to

position

in

PLD

activation

by

the

muscarinic

-LRB-

Rümenapp

et

al.

-RRB-

the

-LRB-

Fahimi-Vahid

et

al.

-RRB-

and

the

sensing

receptor

-LRB-

Huang

et

al.

-RRB-

as

well

as

mechanical

force

-LRB-

Ziembicki

et

al.

-RRB-

As

forskolin

and

cAMP

were

shown

to

cause

activation

of

PLD

via

PKA

and

-LRB-

Ginsberg

et

al.

Yoon

et

al.

-RRB-

or

alternatively

via

the

cAMP-activated

GEF

for

Ras-like

GTPases

Epac

and

R-Ras

-LRB-

López

De

Jesús

et

al.

-RRB-

Gs

proteins

also

mediate

stimulation

of

PLD

PLD

activation

is

also

controlled

by

βγ-subunits

possibly

via

Src

and/or

-LRB-

Le

Stunff

et

al.

Ushio-Fukai

et

al.

-RRB-

but

Gβγ

can

also

directly

interact

with

and

inhibit

PLD

-LRB-

Preininger

et

al.

-RRB-

As

the

precise

mechanism

of

PLD

stimulation

in

intact

cells

was

only

poorly

understood

during

the

last

years

our

laboratory

in

Essen

has

focused

on

the

regulation

of

PLD

activity

by

membrane

receptors

In

cells

signaling

to

PLD

by

a

typical

GPCR

the

muscarinic

receptor

and

an

RTK

the

EGF

receptor

was

studied

and

shown

to

be

executed

by

several

distinct

pathways

-LRB-

Fig.

-RRB-

In

addition

by

expressing

inactive

PLD

mutants

the

muscarinic

and

the

EGF

receptors

were

found

to

signal

to

individual

PLD

isozymes

and

to

selectively

stimulate

and

respectively

-LRB-

Han

et

al.

-RRB-

The

muscarinic

receptor

stimulates

both

PLC

and

PLD

via

PTX-insensitive

mechanisms

-LRB-

Offermanns

et

al.

Peralta

et

al.

Schmidt

et

al.

-RRB-

Interestingly

stimulation

of

PLD

by

the

agonist

carbachol

was

not

affected

by

PKC

inhibitors

suggesting

that

activation

of

PLD

by

the

muscarinic

receptor

was

rather

independent

of

PLC

-LRB-

Rümenapp

et

al.

Schmidt

et

al.

-RRB-

Expression

of

α-subunits

of

G

proteins

and

of

specific

RGS

proteins

was

used

to

identify

the

G

proteins

involved

in

these

pathways

and

demonstrated

that

whereas

the

receptor

signals

to

PLC

via

Gq

proteins

activation

of

PLD

is

mediated

by

family

proteins

-LRB-

Rümenapp

et

al.

-RRB-

PLD

activation

by

the

receptor

but

not

by

the

EGF

receptor

was

further

found

to

be

under

control

of

ARF

-LRB-

Rümenapp

et

al.

-RRB-

as

well

as

Rho

proteins

particularly

RhoA

-LRB-

Schmidt

et

al.

d

-RRB-

Likewise

regulation

of

mTOR

by

LPA

but

not

PDGF

involved

activation

by

Rho

GTPases

-LRB-

Kam

and

Exton

-RRB-

Both

and

RhoA

were

found

to

become

activated

after

receptor

activation

-LRB-

Keller

et

al.

Rümenapp

et

al.

-RRB-

and

a

role

for

Rho-kinase

in

RhoA-controlled

PLD

stimulation

could

be

demonstrated

-LRB-

Schmidt

et

al.

-RRB-

In

further

studies

it

was

shown

that

activation

of

PLD

by

RhoA

and

Rho-kinase

is

mediated

by

and

the

tyrosine

kinase

whereas

activation

by

is

mediated

by

and

the

Arf-GEF

ARNO

-LRB-

Han

et

al.

-RRB-

In

cardiomyocytes

Rho

proteins

were

shown

to

affect

signaling

to

PLD

by

both

and

thrombin

apparently

by

controlling

synthesis

whereas

ARF

selectively

affects

signaling

by

the

receptor

-LRB-

Fahimi-Vahid

et

al.

-RRB-

Fig.

of

PLD

by

the

muscarinic

receptor

and

receptor

tyrosine

kinases

in

cells

In

human

embryonic

kidney

-LRB-

-RRB-

cells

signaling

to

PLD

by

the

muscarinic

receptor

and

by

typical

RTKs

-LRB-

EGF

PDGF

insulin

-RRB-

is

organized

into

rather

discrete

pathways

and

channeled

by

particular

heterotrimeric

G

proteins

and

small

GTPases

-LRB-

orange

-RRB-

specific

GEF

proteins

-LRB-

pink

-RRB-

and

further

signaling

components

-LRB-

green

-RRB-

AC

adenylyl

cyclase

ROCK

Rho-kinase

PLD

can

directly

interact

with

RalA

and

a

Ras/Ral

signaling

cascade

was

shown

to

regulate

PLD

responses

In

cells

Ras

and

RalA

but

not

Rho

proteins

were

located

in

RTK

signaling

to

PLD

and

this

Ras/Ral-dependent

signaling

cascade

was

found

to

be

dependent

on

PKC-α

and

a

Ral-specific

GEF

-LRB-

Fig.

-RRB-

-LRB-

Schmidt

et

al.

Voss

et

al.

-RRB-

RalA

apparently

co-operates

with

ARF

-LRB-

Kim

et

al.

Xu

et

al.

-RRB-

and

Rho

proteins

-LRB-

Frankel

et

al.

Wilde

et

al.

-RRB-

to

achieve

full

PLD

activation

Likewise

Ras

proteins

were

found

to

modulate

PLD

responses

by

PDGF

-LRB-

Lucas

et

al.

-RRB-

and

RalA

to

affect

EGF

receptor

signaling

to

PLD

-LRB-

Lu

et

al.

-RRB-

It

was

recently

shown

that

direct

activation

of

Ras-related

R-Ras

by

Epac

is

involved

in

PLD

stimulation

by

the

muscarinic

receptor

apparently

by

coupling

to

Gs

proteins

-LRB-

López

de

Jesús

et

al.

-RRB-

but

a

contribution

of

Ral

proteins

to

GPCR-induced

PLD

activation

has

not

been

found

-LRB-

Meacci

et

al.

-RRB-

Collectively

these

data

demonstrate

that

heterotrimeric

G

proteins

as

well

as

small

GTPases

co-ordinate

PLD

activation

by

specific

membrane

receptors

in

particular

cell

types

and

these

mechanisms

probably

contribute

to

the

organization

of

agonist-induced

PA

production

for

the

execution

of

diverse

cellular

signaling

tasks

In

addition

the

synthesis

of

can

be

directly

stimulated

by

GPCRs

-LRB-

thrombin

LPA

muscarinic

-RRB-

as

well

as

RTKs

-LRB-

Cochet

et

al.

Nolan

and

Lapetina

Pike

and

Eakes

-RRB-

Receptor

activation

leads

to

increased

association

of

with

the

actin

cytoskeleton

-LRB-

Grondin

et

al.

Payrastre

et

al.

-RRB-

and

receptor-induced

stimulation

and

cytoskeletal

association

of

may

be

directly

involved

in

actin

cytoskeletal

regulation

and

initialize

the

assembly

of

enzymes

into

signaling

complexes

GPCR-induced

stimulation

of

synthesis

was

found

to

be

mediated

by

pertussis

toxin-sensitive

Gi

proteins

-LRB-

Schmidt

et

al.

Stephens

et

al.

-RRB-

but

also

by

and

Gq

proteins

-LRB-

Oude

Weernink

et

al.

-RRB-

Enhanced

synthesis

is

also

caused

by

conventional

PKC

isoforms

which

may

increase

activity

by

stimulating

dephosphorylation

by

the

okadaic

acid-sensitive

protein

phosphatase

-LRB-

Park

et

al.

-RRB-

Concluding

remarks

In

the

last

decade

PLD

has

taken

a

firm

position

as

all-round

player

in

cellular

signaling

events

It

is

now

appreciated

that

PLD

and

act

together

to

execute

several

important

cellular

functions

including

vesicle

transport

cytoskeleton

dynamics

and

cell

adhesion

Because

of

the

reciprocal

stimulation

of

their

activities

it

seems

inappropriate

to

generally

assign

a

conventional

upstairs-downstairs

relationship

to

PLD

and

isozymes

The

localized

generation

of

the

lipid

messengers

by

PLD

and

PA

and

is

clearly

co-ordinated

by

small

GTPases

of

the

ARF

Rho

and

Ras

families

The

following

picture

emerges

of

how

PLD

and

may

co-operate

to

execute

their

cellular

tasks

Particular

small

GTPases

activated

by

membrane

receptors

or

cellular

factors

bind

to

and

recruit

the

enzyme

to

specific

cellular

compartments

Subsequent

activation

of

catalytic

activity

triggers

the

localized

generation

of

which

now

serves

as

an

anchor

for

specific

proteins

including

PLD

enzymes

The

sequestered

PLD

is

activated

by

and

the

GTPases

and

PLD-derived

PA

now

among

other

tasks

contributes

to

the

activation

of

This

feed-forward

regulation

loop

depends

on

both

and

PLD

and

quenching

of

PA

formation

-LRB-

by

primary

alcohols

-RRB-

or

reduction

of

levels

-LRB-

by

PLC-mediated

hydrolysis

or

dephosphorylation

by

phosphatases

-RRB-

can

interrupt

the

snowball

from

rolling

dephosphorylation

may

be

important

in

the

cell

as

a

decisive

mechanism

to

terminate

the

localized

reactions

before

a

cellular

avalanche

develops

Attractive

candidates

are

further

specific

GEFs

and

GAPs

for

the

GTPases

some

of

which

have

been

shown

to

be

directly

regulated

by

inactivation

of

the

organizing

GTPase

may

then

provide

the

final

turn-off

signal

B I O O O O B O O O O O O O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O B O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O B O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O

phospholipase d
phosphatidic acid
pip2
arf
rho
ras


Women with Depression -- `` You Ca n't Tell by Looking '' ™ Introduction Perinatal depression , a mood disorder that occurs during pregnancy or the first year postpartum , affects 10 -- 15 % of women and up to 28 % of women living in poverty . A previous history of depression , either preconceptionally or during the interconception period , is the strongest predictor that a woman will suffer from perinatal depression . Perinatal depression can adversely affect not only the woman , but also her fetus or infant , and has been linked with prematurity , difficulties with maternal-infant bonding and infant behavior problems later in life . If a woman has a known history of depression , she can be counseled preconceptionally about her increased risk of experiencing a subsequent episode during the perinatal years and thus take an active role in recognizing signs and symptoms of depression and accessing treatment as early as possible should an episode occur . The earlier treatment is sought for perinatal depression , the greater the chance for improved outcomes . Background Depression is currently the leading cause of disease-related disability among women worldwide -LSB- 1 -RSB- . Depression can cause moodiness , irritability , changes in sleep patterns , sexual interest or appetite , and an inability to carry on with daily activities . In the most severe cases depression can cause thoughts of harming others or oneself or suicide . Prevalence rates of perinatal depression , which occurs during pregnancy or at some point within the first postpartum year , are similar to those in the general population , affecting 10 -- 15 % of women and up to 28 % of women living in poverty -LSB- 2 , 3 -RSB- . Some studies suggest that a woman 's risk of becoming depressed during the early postpartum period is approximately three times that of women in the general population -LSB- 4 -RSB- . Depression may affect how a woman is able to relate and respond to her infant and if untreated , may lead to thoughts of harming the infant or infanticide . In addition , depression can have significant effects on prenatal care-seeking behavior -LSB- 5 -RSB- , substance abuse -LSB- 6 -RSB- , and infant/child mental health -LSB- 7 -- 9 -RSB- and nutrition -LSB- 10 -RSB- . Depression has also been associated with low birthweight -LSB- 11 -RSB- and premature delivery -LSB- 12 -RSB- . Approximately 50 % of women with perinatal depression remain undiagnosed when they are screened based on clinical observations alone -LSB- 13 -RSB- . Perhaps the strongest argument for routine screening of all pregnant and postpartum women is the fact that you ca n't tell simply by looking that a woman is depressed . However , there are some women who may be at increased risk for perinatal depression , including women living in poverty , those in abusive relationships , and women with a prior history of depression -LSB- 14 -RSB- . In fact , it is thought that having a history of depression is the strongest predictor that a woman will suffer from an episode of major depression during pregnancy or the postpartum period -LSB- 15 , 16 -RSB- . Women with other mental disorders are at risk as well . For example , women with bipolar disorder also have an increased risk of experiencing postpartum depression , and some studies suggest an increased risk for a much more serious illness , postpartum psychosis -LSB- 17 -RSB- . Due to the predictive value of a history of depression , it is vital that women with a history of depression be counseled about the relationship between pregnancy and depression prior to conception . One method to incorporate depression screening & counseling into preconception care Counseling about depression should become a routine part of preconception care . Health care providers who have contact with women during the preconception period can assist women in becoming aware of how pregnancy and depression can affect one another . By controlling depression prior to conception , just as one would with an illness such as diabetes or epilepsy , a woman 's chances for healthy perinatal outcomes may improve -LSB- 18 -RSB- . The Wisconsin Association for Perinatal Care -LRB- WAPC -RRB- is a 35-year-old statewide , non-profit organization dedicated to the improvement of healthy outcomes for women , infants and their families . Since 1989 , WAPC has been working toward infusing depression screening and counseling into preconception care by encouraging health care providers to ask women and their partners about their histories with depression and other mental illnesses prior to conception . One tool that has been developed by WAPC is an information sheet entitled Women with Depression that answers four basic questions : How does depression affect pregnancy ? How does pregnancy affect depression ? How could medications for depression affect the pregnancy ? What can you do before pregnancy ? Case examples The following are two case examples illustrating the impact of depression on pregnancy and the positive effects of being educated prior to a subsequent depressive episode . Although these women were not educated about perinatal depression prior to their first pregnancies , these examples illustrate the importance of depression counseling in the interconception period as well . These cases demonstrate that addressing the questions in Women with Depression can provide an anticipatory contextual framework on which to develop a plan of care . Case example # 1 Sara began experiencing symptoms of depression six months after giving birth to her first child . She had no prior history of depression and had received no counseling prior to conception about the symptoms and presentation of perinatal depression . Sara waited approximately six months before seeking help , but encountered numerous barriers to accessing care . She did eventually get into treatment and attended 15 sessions of interpersonal therapy . Through both her therapy and additional self-education , Sara became quite informed about the effects and consequences of postpartum depression . Approximately six months after giving birth to her second child , Sara began experiencing depression again . This time , Sara sought treatment within one week of the presentation of symptoms . In addition to being able to recognize the signs of depression earlier , as reported by both her and her husband , Sara also remarked on how much easier it was to access treatment , as she knew how to `` navigate the system . '' She knew what type of therapy worked for her and was able to resolve her depression in only seven sessions . Case example # 2 Melanie had a history of anxiety and depression prior to conception , but was never diagnosed or treated . Melanie experienced extreme continuous sleep disturbances almost immediately after the birth of her first child . When this problem had not resolved itself within two months , Melanie sought treatment . She was initially reticent about taking medications because she was breastfeeding her infant , but at nine months postpartum , Melanie began a regimen of paroxetine , which finally resolved the depression . After Melanie 's second birth , she felt slight anxiety about the possibility of suffering from postpartum depression again , but this time had a plan of action in place . When she began having trouble sleeping at two months postpartum , she immediately contacted her therapist and began treatment . She was once again hesitant about taking medication , but at nine months postpartum , began taking paroxetine on the recommendation of her care provider . Although she waited to begin medications with the second depressive episode , Melanie reported having `` a kind of comfort knowing I was on paroxetine before and it did n't hurt my baby . '' Benefits of preconception counseling for women with a history of depression The benefits of counseling women about depression prior to conception are numerous . By treating depression as a chronic condition and by actively managing depression prior to conception , a woman 's chances of being prepared for a depressive episode during the perinatal period greatly increase . In a recent meta-analysis of psychosocial and psychological interventions to reduce the risk of postpartum depression there was no statistically significant effect on the prevention of postpartum depression -LSB- 19 -RSB- . In the absence of preventive treatment , then , understanding postpartum depression could allow families to anticipate possible consequences of maternal depression so they could take steps to help assure healthy outcomes -LSB- 20 -RSB- . By fully disclosing the increased risk of depression if she chooses to become pregnant , a woman can make informed decisions about planning for a family -LSB- 21 -RSB- . If the woman is taking antidepressant medication , she can discuss the impact of those medications on her future pregnancy and breastfeeding . By working with her health care provider , steps can be taken to change the medication or dose if necessary . One of the most devastating effects of perinatal depression is that it occurs at a time when most women feel they should be experiencing joy . By educating women prior to pregnancy or birth about the high prevalence of perinatal depression , they may be better prepared for an episode , should it occur . Women with a history of depression especially should have a plan of action in place in the event of perinatal depression . Women who have suffered from depression once may be more likely to recognize the signs and symptoms of a subsequent episode whether or not the first episode occurred preconceptionally or postpartum . This may be especially true if they are counseled about the possibility of a subsequent episode occurring . Women are not the only ones who can be counseled about the interaction between pregnancy and depression . Loved ones often do not know how to help women suffering from perinatal depression and can not understand why the woman is depressed . By counseling significant others and family members , they , too , can become better prepared and in addition , can help recognize signs of severe depression and assist with accessing treatment . Seeking treatment may present fewer challenges to women who have been successfully treated and counseled about depression as well . Women with a history of depression can be counseled about seeking treatment at the earliest possible sign of depression , rather than waiting , as so often happens in primary episodes . The earlier treatment can be sought , the better the outcomes -LSB- 22 -RSB- . Stigma may be reduced as well if women are counseled ahead of time , making them more open to seeking treatment and more comfortable with their treatment decisions . Conclusions Testimonials from affected women suggest that counseling women with a history of depression leads to improved outcomes should they suffer from a subsequent episode during the perinatal period . Women may be more likely to recognize the signs of depression , more likely to seek treatment earlier and will know what treatment options work for them . Due to an earlier recognition of depression , treatment may have a shorter duration as well . In addition , by counseling women about depression prior to conception , they and their families will have time to develop a plan of action should a depressive episode occur and will be equipped to make informed decisions about family planning . Tools such as Women with Depression may be beneficial in both educating consumers and assisting providers with consultations about depression prior to pregnancy or during the interconception period . The major challenge currently lies in convincing health care providers to address women 's mental health and to screen and counsel for depression during the preconception period . Intervention strategies using medication or counseling have not been significantly effective in preventing postpartum depression . Anticipating the potential interplay between depression and pregnancy may be an intervention that can lead to better mental health and perinatal outcomes . Future research should address the content and timing of preconception counseling , including what information is needed and when and how it should be disseminated . Treatment algorithms and strategies could then be developed for practitioners and families to help prepare for the postpartum period . Finally , well-controlled intervention studies utilizing the materials developed could focus on maternal mental health , perinatal , and infant outcomes to answer questions about efficacy and effectiveness .

O O B O O O O O O O O O O O B B O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B B O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O B O O O O O O O O B O O O O B O O O B O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O B O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O

perinatal
depression
preconception
mood disorder