bluuebunny/crossref_metadata_2025 huggingface dataset:
Bipolar Order
Authors: VanHook Annalisa M.
Published: June 2008

The
Drosophila
wing has proven valuable in understanding planar cell polarity (PCP), the phenomenon that dictates the packing geometry and polarity of cells in a polarized epithelium. Each cell of the dorsal wing epithelium produces a single hair, and the Frizzled (Fz) PCP pathway aligns all the hairs along the proximodistal (PD) wing axis. Doyle
et al.
report that mutations that disrupt Fz PCP signaling also caused defects in the alignment of wing ridges. In the posterior wing compartment, ridges are oriented along the PD axis, but in the anterior compartment they are oriented along the anteroposterior (AP) axis, thus making hairs and ridges aligned in the posterior compartment but orthogonal in the anterior compartment. To address the question of how a single PCP pathway could generate two different patterns in the same polarized epithelium, the group focused on Spiny legs (Sple) and Prickle (Pk), two different protein isoforms encoded by the
pk
gene. Through loss- and gain-of-function genetic experiments, the authors found that disrupting PCP signaling early in wing development [up to 18 hours after pupal formation (APF)] did not affect hair polarity but did affect posterior ridge orientation and that disrupting late PCP signaling (more than 18 hours APF) affected hair polarity all over the wing but only altered ridge orientation in the anterior compartment. The authors propose a model in which the early Sple-dependent phase of PCP patterning establishes a cell-packing pattern that orients all ridges along the PD axis; during the late Pk-dependent phase of PCP, hair polarity is established and the anterior compartment ridges are reoriented. The differential use of two closely related isoforms of a PCP pathway component enables the system to function biphasically.

K. Doyle, J. Hogan, M. Lester, S. Collier, The Frizzled Planar Cell Polarity signaling pathway controls
Drosophila
wing topography.
Dev. Biol.
317
, 354-367 (2008).
[PubMed]
Allosteric Regulator of Bacterial Cell Fate
Authors: Gough Nancy R.
Published: June 2008

Bacterial cells can undergo asymmetric cell division. In
Caulobacter crescentus
, this involves the transition from a motile cell to an attached stalked cell, which divides to form a stalked cell that divides again immediately, and a motile swarmer cell that forms a flagellum and swims away before attaching and starting the process again. Two sensor histidine kinases, DivJ and PleC, are important for the polarized cell division process and determination of cell fate, and both phosphorylate and stimulate the activity of the diguanylate cyclase PleD, which produces cyclic-di-GMP. Paul
et al
. show that DivK, which is a response regulator downstream of both DivJ and PleC, is also an allosteric regulator of each enzyme. For PleC, which has both kinase and phosphatase activities, in vitro DivK and a nonphosphorylatable form of DivK stimulated the kinase activity and inhibited the phosphatase activity of PleC. In vitro, the activation of PleD by DivJ was inhibited by the addition of DivK because DivJ preferred DivK as a substrate. However, nonphosphorylatable DivK stimulated the kinase activity of DivJ for either wild-type DivK or PleD; thus, DivK is an allosteric regulator of both DivJ and PleC. Through the analysis of a DivK mutant that was defective in stimulating the kinase activity of PleC and analysis of PleC mutants defective in kinase activity, or kinase and phosphatase activity, the authors showed that, in vivo, the transition of PleC from a phosphatase to a kinase through the allosteric regulator DivK and the PleC-mediated activation of PleD were essential for the swarmer-to-stalk cell differentiation and asymmetric cell division. DivK appears to mediate crosstalk between and provide feedback to the DivJ and PleC kinases to coordinate polarized cell differentiation and division.

R. Paul, T. Jaeger, S. Abel, I. Wiederkehr, M. Folcher, E. G. Biondi, M. T. Laub, U. Jenal, Allosteric regulation of histidine kinases by their cognate response regulator determines cell fate.
Cell
133
, 452-461 (2008).
[PubMed]
Synaptojanin Protects Synaptic Function
Authors: Foley John F.
Published: June 2008

Alzheimer’s disease (AD) is associated with the accumulation of aggregates of insoluble amyloid-β (Aβ) protein, in particular Aβ42, which is released from the membrane-bound amyloid precursor protein by the proteases β- and γ-secretase. Oligomeric Aβ42 alters synaptic activity by affecting glutamate receptor abundance at synaptic membranes and reducing the number of dendritic spines, but its effects on intracellular signaling are unclear. Berman
et al
. had previously shown that mutations in genes encoding components of the γ-secretase complex are linked to abnormal metabolism of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P
2
]. Here, they showed that exposure of mouse cortical neurons to a preparation of oligomeric Aβ42 or to cell-derived Aβ42 reduced the abundance of membrane PtdIns(4,5)P
2
compared with that in control neurons, as measured by high-performance liquid chromatography. This Aβ42-dependent reduction of membrane PtdIns(4,5)P
2
abundance was blocked when extracellular Ca
2+
was chelated by EGTA or when neurons were treated with an antibody against Aβ. The membrane localization of a fluorescent PtdIns(4,5)P
2
-binding protein was lower in Aβ42-treated PC12 cells than in control cells; however, an inhibitor of phospholipase C, which hydrolyzes PtdIns(4,5)P
2
, restored membrane localization of the PtdIns(4,5)P
2
probe in Aβ42-treated cells. When neurons from mice heterozygous for the gene encoding the PtdIns(4,5)P
2
phosphatase synaptojanin 1 (
Synj1
+/–
mice) were treated with Aβ42, the abundance of membrane PtdIns(4,5)P
2
was unchanged. Furthermore, whereas long-term potentiation (LTP) in hippocampal slices of wild-type mice was inhibited by Aβ42 treatment, LTP in hippocampal slices from
Synj1
+/–
mice was unaffected. Thus, Aβ42 appears to impair synaptic plasticity by reducing membrane PtdIns(4,5)P
2
abundance, an effect that is partly dependent on synaptojanin 1, whose inhibition may well prove beneficial in the treatment of AD.

D. E. Berman, C. Dall’Armi, S. V. Voronov, L. B. J. McIntire, H. Zhang, A. Z. Moore, A. Staniszewski, O. Arancio, T.-W. Kim, G. Di Paolo, Oligomeric amyloid-β peptide disrupts phosphatidylinositol-4,5-bisphosphate metabolism.
Nat
.
Neurosci
.
11
, 547-554 (2008).
[PubMed]
Common Senses
Authors: VanHook Annalisa M.
Published: June 2008

Many of the signaling pathways shared between vertebrates and invertebrates were present in the eumetazoan, the ancestor of all multicellular animals, as evidenced by their presence in the sea anemone
Nematostella vectensis
. Fibroblast growth factor (FGF) signaling performs varied functions throughout an animal’s lifetime and is required during early embryogenesis for gastrulation and neural cell fate specification, including the specification of sensory structures. Rentzsch
et al.
suggest that sensory organ specification was one of its ancestral roles.
Nematostella
has only one larval sensory organ, the apical organ, which forms at the aboral pole of the embryo (opposite the mouth) and allows the animal to find a suitable place for settlement and metamorphosis. Expression analysis revealed that genes encoding two FGF ligands,
NvFGFa1
and
NvFGFa2
, and one encoding a FGF receptor,
NvFGFRa
, were expressed at the embryonic apical pole. Knockdown with morpholino oligonucleotides of either NvFGFa1 or NvFGFRa produced larvae that lacked an apical organ and that were able to swim but failed to settle and metamorphose. Conversely, knockdown of NvFGFa2 generated larvae with expanded apical organs. Signaling by NvFGFa1 was required to maintain expression of both
NvFGFa1
and
NvFGFa2
, thereby establishing both positive and negative feedback mechanisms. Pharmacological experiments suggested that NvFGFa1 signaled through a mitogen-activated protein kinase (MAPK) cascade. The region of the embryo in which
NvFGFa1
and
NvFGFRa
were expressed expanded in the absence of NvFGFa2. Thus, two FGFs antagonize one another to induce the apical organ and at least NvFGFa1 signals through a pathway that is very much like the canonical FGF pathway of more complex animals. Although sea anemones do not have a centralized nervous system, the larval sensory organ is induced by the same pathway that contributes to neural cell fating and sensory organ induction in more complex nervous systems.

F. Rentzsch, J. H. Fritzenwanker, C. B. Scholz, U. Technau, FGF signalling controls formation of the apical sensory organ in the cnidarian
Nematostella vectensis
.
Development
135
, 1761-1769 (2008).
[Abstract]
[Full Text]
VGF, a New Player in Antidepressant Action?
Authors: Malberg Jessica E. , Monteggia Lisa M.
Published: June 2008

Recent studies have identified adaptations of intracellular signaling pathways and target genes that could contribute or modulate the action of antidepressant drugs, as well as exercise-mediated antidepressant responses. Understanding these adaptations, particularly those changes that are common to diverse antidepressant treatments, is important for the development of more potent and specific treatments of depression. There is growing evidence that growth factors may be important mediators of antidepressant responses. Now, VGF (not an acronym), a neuropeptide that has previously been shown to be involved in maintaining organismal energy balance, as well as in mediating hippocampal synaptic plasticity, may be involved in mediating antidepressant responses. These studies use in vivo approaches to link VGF to the antidepressant-like behavioral effects produced by antidepressant drugs and exercise.
Synaptic Patterning by Morphogen Signaling
Authors: Williamson W. Ryan , Hiesinger P. Robin
Published: June 2008

Gradients of secreted small morphogenic molecules control cell proliferation and patterning throughout animal development. Recent years have seen the discovery of surprising roles for morphogens in later developmental processes, including axon pathfinding and synaptogenesis. The latest addition is a role for the TGF-β superfamily morphogen Activin in synaptic patterning of the
Drosophila
visual system. In contrast to classical instructive and long-range morphogen gradients, Activin acts as a permissive and local motility restriction signal around several hundred individual photoreceptor axon terminals. Activin must therefore act in concert with other instructively attracting and repelling signals as part of a larger genetic program for brain wiring.
A Deadly Gift
Authors: Adler Elizabeth M.
Published: June 2008

Although many malignant gliomas express EGFRvIII, a constitutively active oncogenic mutant form of the epidermal growth factor receptor (EGFR), the mutant receptor may actually be present in only a subset of the tumor cells. Al-Nedawi
et al
. found that a human glioma cell line (U373 cells) stably transfected with and made to express EGFRvIII (U373vIII cells) produced more membrane-derived microvesicles than did the parent cell line. Increased formation of vesicular membrane protrusions was apparent in U373vIII cells by scanning electron microscopy, and the abundance of total protein in the microvesicle fraction of medium in which cells had grown was increased. U373vIII cell-derived microvesicles contained EGFRvIII, as well as the lipid raft marker flotillin-1. Unlike U373 cells, U373vIII cells form subcutaneous tumors when injected into immunodeficient mice; these EGFRvIII-immunoreactive tumors released EGFRvIII-containing microvesicles into the circulatory system. Experiments in which U373 cells were incubated with vesicles derived from U373vIII cells indicated that microvesicular EGFRvIII was transferred to the U373 cells, where it appeared on the cell surface. A day later, U373 cells that had been exposed to EGFRvIII-containing microvesicles showed increased phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2). Pharmacological treatment of microvesicles to inhibit signaling by EGFR-family receptors attenuated this increase in ERK1/2 phosphorylation, as did treatment of the microvesicles with annexin V (to prevent their uptake). EGFRvIII-containing microvesicles also stimulated other events downstream of EGFRvIII: Akt phosphorylation, release of vascular endothelial growth factor, abundance of the antiapoptotic protein Bcl-x
L
, and the ability of U373 cells to grow in soft agar (indicative of malignant transformation). The authors thus conclude that membrane microvesicles provide a mechanism for horizontal transfer of the transformed phenotype.

K. Al-Nedawi, B. Meehan, J. Micallef, V. Lhotak, L. May, A. Guha, J. Rak, Intercellular transfer of the oncogenic receptor EGFRvIII by microvesicles derived from tumour cells.
Nat
.
Cell Biol
.
10
, 619-624 (2008).
[PubMed]
Faster Than a Speeding Molecule
Authors: VanHook Annalisa M.
Published: June 2008

Mechanotransduction is the process by which external physical forces induce intracellular responses. Na
et al.
examined the velocity with which the tyrosine kinase Src could be activated by mechanical stress as compared with epidermal growth factor (EGF) signaling. The authors measured Src activation with a reporter that consisted of a yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP) tethered to one another by a short (12-amino acid) Src substrate peptide. When the peptide is not bound by Src, the fluorescent tags are close enough to interact, producing a high fluorescence resonance energy transfer (FRET) ratio, but upon binding by Src, the tags are displaced, producing a low FRET ratio. The authors added magnetic beads coated with the tripeptide Arg-Gly-Asp to cultured fibroblasts to induce the cells to form focal adhesions with the beads and then used a magnetic field to deliver mechanical stress to the cells. Focal adhesions were required for mechanical stress-induced Src activation, because cells that were not induced to form focal adhesions exhibited no Src activation in response to a magnetic field. By using fluorescently labeled tubulin and a microscopic method for mapping microtubule deformations, the authors found that Src activation colocalized with the regions of greatest microtubule deflections. Mechanical stimulation of Src activity was much faster than stimulation through the EGF pathway. Whereas application of purified EGF resulted in Src activation in 12 seconds, mechanical stress activated Src in as little as 0.3 seconds, much faster than could be accomplished by a pathway that relied on either passive diffusion or active transport of molecules to relay the signal inside the cell. Only cells plated on stiff (as opposed to soft) substrates exhibited Src activation by mechanotransduction, so the phenomenon also required that the cytoskeleton be prestressed; much like a spider’s web, the cytoskeletal network could transmit mechanical stress signals only when tensioned. The authors proposed that the cytoskeleton conveyed the mechanical force into the cytoplasm by vibrating or stretching. Mechanotransduction, then, may enable nearly simultaneous, though nonspecific, activation of molecules near the plasma membrane and deep inside the cytoplasm.

S. Na, O. Collin, F. Chowdhury, B. Tay, M. Ouyang, Y. Wang, N. Wang, Rapid signal transduction in living cells is a unique feature of mechanotransduction.
Proc. Natl. Acad. Sci. U.S.A.
105
, 6626-6631 (2008).
[Abstract]
[Full Text]
A Window into the Dynamics of Rab5 Activity
Authors: Adler Elizabeth M.
Published: June 2008

The small guanosine triphosphatase (GTPase) Rab5, known for its role in early endocytosis, has also been implicated in the engulfment of apoptotic cells, a process important in limiting the inflammatory response. Kitano
et al
. used Raichu-Rab5, a fluorescence resonance energy transfer (FRET) probe in which FRET reflects an increase in the active GTP-bound form of Rab, or Raichu-Rab5/PM (a form targeted to the plasma membrane) to monitor Rab5 activation in Swiss3T3 cells stably expressing integrin α
v
β
3
or in a macrophage cell line. Live cell imaging showed that the duration of Rab5 activation varied among phagosomes and that, in a substantial number, Rab5 was reactivated after termination of the initial period of activation. Simultaneous imaging of fluorescently labeled actin revealed that Rab5 activation and recruitment to phagosomes occurred during disassembly of the actin network around the phagosome. Rab5 inactivation took place before the breakdown of the apoptotic cell, a process that was delayed (but not blocked) by a Rab5 dominant-negative mutant. Pharmacological manipulations indicated that microtubule integrity was required for Rab5 activation and that its repetitive activation depended on their dynamic instability. Depletion of the Rab5 guanine nucleotide exchange factor (GEF) Gapex-5 with short interfering RNA (siRNA) inhibited Rab5 activation during phagocytosis, whereas depletion of other Rab5 GEFs (Rabex-5 and Rin) did not. EB1, a protein that associates with the tips of microtubules, bound to Gapex-5 in pull-down assays, and EB1 depletion with siRNA decreased Rab5 activation. The authors develop a model in which actin disassembly during closure of the phagosome enables extension of microtubules to the area, allowing the delivery of Gapex-5 to the phagosome and thereby Rab5 activation.

M. Kitano, M. Nakaya, T. Nakamura, S. Nagata, M. Matsuda, Imaging of Rab5 activity identifies essential regulators for phagosome maturation.
Nature
453
, 241-245 (2008).
[PubMed]
Home Is Where the Hearth Is
Authors: Ray L. Bryan
Published: June 2008

The nematode
Caenorhabditis elegans
can "remember" the temperature at which it was grown and will seek out that temperature if later exposed to a gradient of temperatures. In an effort to define the neuronal circuitry that allows this behavior, Kuhara
et al
. found that a neuron known as AWC has an important role in sensing temperature. This came as a surprise because the AWC cell is also known to function as an olfactory neuron. The cell could respond independently to odorants and temperature, even though when sensing temperature the neuron used a G protein-mediated intracellular signaling system similar to that used in olfactory responses.

A. Kuhara, M. Okumura, T. Kimata, Y. Tanizawa, R. Takano, K. D. Kimura, H. Inada, K. Matsumoto, I. Mori, Temperature sensing by an olfactory neuron in a circuit controlling behavior of
C. elegans.
Science
320
, 803-807 (2008).
[Abstract]
[Full Text]
TCR Triggering by the pMHC Complex: Valency, Affinity, and Dynamics
Authors: Varma Rajat
Published: June 2008

The interaction between the T cell receptor (TCR) and a peptide-loaded major histocompatibility complex (pMHC) is one of the most-studied interactions in immunology, and yet the precise mechanism by which this system operates is still not fully understood. One key issue is whether TCR triggering minimally requires monomeric pMHC complexes or higher-order multimers (two or more pMHCs). Any model of TCR triggering must explain the high sensitivity, specificity, and dynamic range of ligand responsiveness that this receptor system exhibits. Most models of TCR triggering have not fully appreciated the dynamic aspects of TCR triggering. TCR triggering happens very quickly, and the properties of sensitivity and specificity can be explained by a model that accounts for the interaction dynamics of such a receptor system. In this paper, it is proposed that the important parameter in TCR triggering is the immobilization of the TCR-pMHC complex in the plasma membrane. Whether this involves monomeric or multimeric pMHCs may depend on the affinity of the TCR for the pMHC.
Is Zinc a Neuromodulator?
Authors: Kay Alan R. , Tóth Katalin
Published: June 2008

The vesicles of certain glutamatergic terminals in the mammalian forebrain are replete with ionic zinc. It is believed that during synaptic transmission zinc is released, binds to receptors on the pre- or postsynaptic membranes, and hence acts as a neuromodulator. Although exogenous zinc modulates a wide variety of channels, whether synaptic zinc transits across the synaptic cleft and alters the response of channels has been difficult to establish. We will review the evidence for zinc as a neuromodulator and propose diagnostic criteria for establishing whether it is indeed one. Moreover, we will delineate alternative ways in which zinc might act at synapses.
Focal Adhesion Kinase Versus p53: Apoptosis or Survival?
Authors: Cance William G. , Golubovskaya Vita M.
Published: June 2008

Focal adhesion kinase (FAK) is a tyrosine kinase that interacts with a multitude of signaling partners and helps cells to survive in the face of various proapoptotic signals. One of the most important interactions for FAK is with the tumor suppressor protein p53. p53 binds not only to the amino-terminal domain of FAK but also to the
FAK
promoter to inhibit its transcription. A study now reports the biological implications of the kinase-independent interaction of FAK with p53, which opens up future perspectives in cell signaling and cancer research. We focus on FAK and p53 signaling, which link signal transduction pathways from the extracellular matrix and cytoplasm to the nucleus, in human and mouse cells. FAK is proposed to be a critical scaffold protein that sequesters proapoptotic proteins, such as p53, to mediate cell survival.
Traffic Control for Oocytes
Authors: Ray L. Bryan
Published: June 2008

The nematode
C. elegans
, not wanting to waste its resources, produces mature oocytes through meiotic maturation only when the presence of sperm is detected. The detection system consists of a transmembrane receptor protein, VAB-1, which recognizes a secreted sperm protein known as MSP (major sperm protein). Constitutive signaling through VAB-1 appears to hold oocytes in check, and the signal from sperm decreases such signaling to allow the oocyte to mature. VAB-1 occurs on both the oocytes themselves and gonadal sheath cells. Cheng
et al
. used a fusion protein of green fluorescent protein (GFP) linked to VAB-1 to monitor the receptor’s location and report that regulation of endocytic trafficking of the receptor might provide a critical control point for the regulation of oocyte maturation. In the absence of sperm, VAB-1::GFP was localized with a marker of recycling endosomes at the cortex. In hermaphrodites (which make their own sperm), VAB-1 was found instead in larger cytoplasmic vesicles. In a mutant in which vesicle transport from the recycling compartment to the plasma membrane is inhibited, VAB-1::GFP accumulated in the endocytic recycling compartment and maturation was inhibited. A search for proteins that interacted with the intracellular domain of VAB-1 yielded RAN-1, which was previously genetically identified as a negative regulator of oocyte maturation but is better known for its role in controlling nuclear transport. Depletion of RAN-1 with RNAi reduced the abundance of VAB-1::GFP in the cortex and enhanced accumulation in the larger cytoplasmic vesicles. The sheath cells do their part through signaling that requires a heterotrimeric guanine nucleotide-binding protein (G protein) and gap-junction channels. Disruption of these elements with RNAi appeared to diminish the signals required to inhibit maturation in the absence of sperm and led exclusion of VAB-1::GFP from the recycling endosome compartment. Although cause and effect remain to be formally established, the authors propose that the gonadal sheath cells may have a primary role in sensing MSP and then influence trafficking in the oocyte and, thus, its ability to respond directly to MSP. As Hang
et al
. note in commentary, why the double layer of regulation is required and exactly how VAB-1 trafficking regulates signaling by the receptor are among a series of new directions for study that are brought into focus by the new results.

H. Cheng, J. A. Govindan, D. Greenstein, Regulated trafficking of the MSP/Eph receptor during oocyte meiotic maturation in
C. elegans
.
Curr. Biol.
18
, 705-714 (2008).
[PubMed]

J. S. Hang, B. D. Grant, A. Singson, Meiotic maturation: Receptor trafficking is the key.
Curr. Biol.
18
, R416-R418 (2008).
[PubMed]
Two Clocks Are Better Than One
Authors: Kelner Katrina L.
Published: June 2008

The circadian clock of mammals resides within the hypothalamus, in the suprachiasmatic nucleus, and it is entrained by light. There is evidence that another circadian clock--entrained by food--also exists in the brain, possibly elsewhere in the hypothalamus. By replacing a missing clock component (Bmal) in selected hypothalamic nuclei of mice lacking Bmal1, Fuller
et al.
identified the dorsomedial nucleus of the hypothalamus as the site of the food-entrained clock. When Bmal1 was reintroduced selectively into the suprachiasmatic nucleus, the previously unresponsive mice regained the ability to entrain both locomotor activity and body temperature rhythms to a 12:12 light:dark cycle. Reintroduction of Bmal into the dorsomedial nucleus restored the ability of the animals to entrain to a restricted period of food availability, but not to a light cycle. Thus, the dorsomedial nucleus contains a second circadian clock that seems to be induced when food is restricted to take over control of functions such as activity levels that increase the chances of the animal successfully locating additional food resources.

P. M. Fuller, J. Lu, C. B. Saper, Differential rescue of light- and food-entrainable circadian rhythms.
Science
320
, 1074-1077 (2008).
[Abstract]
[Full Text]
Unmasking the Sensor of Iron Deficiency
Authors: VanHook Annalisa M.
Published: June 2008

Iron homeostasis is important because most animals require it and high levels can be toxic. Despite being a relatively common metabolic condition, very little is known about how iron deficiency is perceived in mammals. Mouse
mask
mutants are characterized by iron deficiency anemia and loss of body hair. The chemically induced mutation in the
mask
strain was positionally cloned by Du
et al.
and found to map to the transmembrane serine protease 6 (Tmprss6), where it interferes with splicing. Overexpression of
Tmprss6
caused transcriptional repression of the
Hamp
gene, which encodes the peptide hormone hepcidin. Hepcidin represses iron absorption by intestinal cells. The authors conclude that Tmprss6 is part of the iron-sensing machinery that relays an iron deficiency signal to the molecules that control dietary absorption.

X. Du, E. She, T. Gelbart, J. Truksa, P. Lee, Y. Xia, K. Khovananth, S. Mudd, N. Mann, E. M. Y. Moresco, E. Beutler, B. Beutler, The serine protease TMPRSS6 is required to sense iron deficiency.
Science
320
, 1088-1092 (2008).
[Abstract]
[Full Text]
Bacterial-Modulated Signaling Pathways in Gut Homeostasis
Authors: Lee Won-Jae
Published: June 2008

Symbiotic mutualism with gut microbes occurs in all metazoans, and it is well established that commensal bacteria influence multiple aspects of host gut physiology such as innate immunity and development. However, our understanding of these coevolved interactions between prokaryotes and eukaryotes remains unclear. One mechanism by which commensal bacteria modulate host intracellular signaling pathways in order to avoid excess inflammation has now been determined. In this process, bacterial-induced reactive oxygen species in gut epithelial cells act as key messengers that inhibit the cullin-1–dependent protein degradation machinery, which in turn results in the stabilization of a master negative regulator of inflammation, inhibitor of nuclear factor-κB (IκB). Furthermore, this bacterial-mediated system also appears to be involved in the stabilization of a key developmental regulator, β-catenin. These findings provide new insights into the molecular mechanisms by which commensal microbes shape host cellular physiology.
ETosis: A Novel Cell Death Pathway
Authors: Wartha Florian , Henriques-Normark Birgitta
Published: June 2008

The formation of extracellular traps (ETs) by neutrophils and mast cells is an important mechanism in the innate immune response. These structures consist of a chromatin-DNA backbone with attached antimicrobial peptides and enzymes that trap and kill microbes. After stimulation of neutrophils and mast cells with phorbol esters, chemoattractant peptides, or chemokines, the generation of reactive oxygen species (ROS), such as hydrogen peroxide, by NAPDH [nicotinamide adenine dinucleotide phosphate (reduced form)] oxidase initiates a signaling cascade that leads to the disintegration of the nuclear and cellular membranes and the formation of ETs. This form of cell death is neither apoptotic nor necrotic, but whether it occurs because of the oxidation of phosphatases and kinases, as in other ROS-mediated signaling cascades, remains to be elucidated. These findings implicate "ETosis" as a novel cell death pathway in leukocytes.
Evaluation of the Antimicrobial, Antioxidant, and Anti-Inflammatory Activities of Hydroxychavicol for Its Potential Use as an Oral Care Agent
Authors: Sharma Sandeep , Khan Inshad Ali , Ali Intzar , Ali Furqan , Kumar Manoj , Kumar Ashwani , Johri Rakesh Kamal , Abdullah Sheikh Tasduq , Bani Sarang , Pandey Anjali , Suri Krishan Avtar , Gupta Bishan Datt , Satti Naresh Kumar , Dutt Prabhu , Qazi Ghulam Nabi
Published: June 2008

Hydroxychavicol isolated from the chloroform extraction of aqueous extract of
Piper betle
leaves showed inhibitory activity against oral cavity pathogens. It exhibited an inhibitory effect on all of the oral cavity pathogens tested (MICs of 62.5 to 500 μg/ml) with a minimal bactericidal concentration that was twofold greater than the inhibitory concentration. Hydroxychavicol exhibited concentration-dependent killing of
Streptococcus mutans
ATCC 25175 up to 4× MIC and also prevented the formation of water-insoluble glucan. Interestingly, hydroxychavicol exhibited an extended postantibiotic effect of 6 to 7 h and prevented the emergence of mutants of S.
mutans
ATCC 25175 and
Actinomyces viscosus
ATCC 15987 at 2× MIC. Furthermore, it also inhibited the growth of biofilms generated by
S. mutans
and
A. viscosus
and reduced the preformed biofilms by these bacteria. Increased uptake of propidium iodide by hydroxychavicol-treated cells of
S. mutans
and
A. viscosus
indicated that hydroxychavicol probably works through the disruption of the permeability barrier of microbial membrane structures. Hydroxychavicol also exhibited potent antioxidant and anti-inflammatory activities. This was evident from its concentration-dependent inhibition of lipid peroxidation and significant suppression of tumor necrosis factor alpha expression in human neutrophils. Its efficacy against adherent cells of
S. mutans
in water-insoluble glucan in the presence of sucrose suggests that hydroxychavicol would be a useful compound for the development of antibacterial agents against oral pathogens and that it has great potential for use in mouthwash for preventing and treating oral infections.
Rapid Eradication of
Listeria monocytogenes
by Moxifloxacin in a Murine Model of Central Nervous System Listeriosis
Authors: Grayo Solène , Lott-Desroches Marie-Catherine , Dussurget Olivier , Respaud Renaud , Fontanet Arnaud , Join-Lambert Olivier , Singlas Eric , Le Monnier Alban
Published: June 2008

Listeriosis is a rare but life-threatening infection. A favorable outcome is greatly aided by early administration of antibiotics with rapid bactericidal activity against
Listeria monocytogenes
. Moxifloxacin, a new-generation fluoroquinolone with extended activity against gram-positive bacteria, has proved its effectiveness in vitro against intracellular reservoirs of bacteria. The efficacies of moxifloxacin and amoxicillin were compared in vivo by survival curve assays and by studying the kinetics of bacterial growth in blood and organs in a murine model of central nervous system (CNS) listeriosis. We combined pharmacokinetic and pharmacodynamic approaches to correlate the observed efficacy in vivo with plasma and tissue moxifloxacin concentrations. Death was significantly delayed for animals treated with a single dose of moxifloxacin compared to a single dose of amoxicillin. We observed rapid bacterial clearance from blood and organs of animals treated with moxifloxacin. The decrease in the bacterial counts in blood and brain correlated with plasma and cerebral concentrations of antibiotic. Moxifloxacin peaked in the brain at 1.92 ± 0.32 μg/g 1 hour after intraperitoneal injection. This suggests that moxifloxacin rapidly crosses the blood-brain barrier and diffuses into the cerebral parenchyma. Moreover, no resistant strains were selected during in vivo experiments. Our results indicate that moxifloxacin combines useful pharmacokinetic properties and rapid bactericidal activity and that it may be a valuable alternative for the treatment of CNS listeriosis.
Cytokine Expression in the Colonic Mucosa of Human Immunodeficiency Virus-Infected Individuals before and during 9 Months of Antiretroviral Therapy
Authors: Schulbin Hubert , Bode Hagen , Stocker Hartmut , Schmidt Wolfgang , Zippel Thomas , Loddenkemper Christoph , Engelmann Elisabeth , Epple Hans-Jörg , Arastéh Keikawus , Zeitz Martin
Published: June 2008

High-level human immunodeficiency virus (HIV) replication and the rapid breakdown of the mucosal immune system are the hallmarks of HIV infection in the gut. Cytokine dysregulation may be related to both phenomena. Using real-time PCR we quantified the colonic mucosal mRNA expression of selected proinflammatory and regulatory (gamma interferon [IFN-gamma], tumor necrosis factor alpha [TNF-α], and interleukin-2 [IL-2], IL-4, IL-6, and IL-10) and HIV-inhibitory (IL-16, CCL3, and CCL5) cytokines for 10 HIV-infected patients before and during 9 months of highly active antiretroviral therapy (HAART). HIV RNA and T-cell dynamics were measured in the colonic mucosa and the blood. Seven HIV-negative individuals served as controls. The mucosal mRNA expression of TNF-α, IFN-gamma, IL-4, IL-6, and IL-10 was significantly higher in HIV-infected patients than in control patients and remained elevated during 9 months of HAART despite the decline in blood and mucosal HIV RNA levels and an increase in the level of CD4+T lymphocytes. The mRNA levels of CCL3 and CCL5, both of which were elevated before treatment, returned to nearly normal during therapy. Despite reductions in levels of mucosal HIV RNA and the restoration of mucosal CD4+T lymphocytes, antiretroviral therapy failed to restore the normal colonic immunologic environment.
Chronic Administration of Tenofovir to Rhesus Macaques from Infancy through Adulthood and Pregnancy: Summary of Pharmacokinetics and Biological and Virological Effects
Authors: Van Rompay Koen K. A. , Durand-Gasselin Lucie , Brignolo Laurie L. , Ray Adrian S. , Abel Kristina , Cihlar Tomas , Spinner Abigail , Jerome Christopher , Moore Joseph , Kearney Brian P. , Marthas Marta L. , Reiser Hans , Bischofberger Norbert
Published: June 2008

The reverse transcriptase (RT) inhibitor tenofovir (TFV) is highly effective in the simian immunodeficiency virus (SIV) macaque model of human immunodeficiency virus infection. The current report describes extended safety and efficacy data on 32 animals that received prolonged (≥1- to 13-year) daily subcutaneous TFV regimens. The likelihood of renal toxicity (proximal renal tubular dysfunction [PRTD]) correlated with plasma drug concentrations, which depended on the dosage regimen and age-related changes in drug clearance. Below a threshold area under the concentration-time curve for TFV in plasma of ∼10 μg·h/ml, an exposure severalfold higher than that observed in humans treated orally with 300 mg TFV disoproxil fumarate (TDF), prolonged TFV administration was not associated with PRTD based on urinalysis, serum chemistry analyses, bone mineral density, and clinical observations. At low-dose maintenance regimens, plasma TFV concentrations and intracellular TFV diphosphate concentrations were similar to or slightly higher than those observed in TDF-treated humans. No new toxicities were identified. The available evidence does not suggest teratogenic effects of prolonged low-dose TFV treatment; by the age of 10 years, one macaque, on TFV treatment since birth, had produced three offspring that were healthy by all criteria up to the age of 5 years. Despite the presence of viral variants with a lysine-to-arginine substitution at codon 65 (K65R) of RT in all 28 SIV-infected animals, 6 animals suppressed viremia to undetectable levels for as long as 12 years of TFV monotherapy. In conclusion, these findings illustrate the safety and sustained benefits of prolonged TFV-containing regimens throughout development from infancy to adulthood, including pregnancy.
Temporal and Spatial Distribution of Clonal Complexes of
Streptococcus pneumoniae
Isolates Resistant to Multiple Classes of Antibiotics in Belgium, 1997 to 2004
Authors: Amrine-Madsen Heather , Van Eldere Johan , Mera Robertino M. , Miller Linda A. , Poupard James A. , Thomas Elizabeth S. , Halsey Wendy S. , Becker Julie A. , O'Hara F. Patrick
Published: June 2008

We performed multilocus sequence typing on 203 invasive disease isolates of
Streptococcus pneumoniae
to assess the clonal compositions of isolates from two provinces in Belgium and to determine the relationship between clones and antibiotic nonsusceptibility, particularly nonsusceptibility to two or more classes of antibiotics. The frequency of multiclass nonsusceptibility (MCNS) was higher in the province of West Flanders (38%) than in Limburg (21%). This difference was largely attributable to five clonal complexes (CC156, CC81, CC143, CC193, and CC1848), which contained high proportions of isolates with MCNS (>47%) and which were circulating at higher frequencies in West Flanders. The
S. pneumoniae
population changed over time, as CC156 and CC81 declined in frequency from 1997 to 1999 to 2001 to 2004. Over the same time period, the frequency of pneumococcal conjugate vaccine 7 (PCV7) serotypes dropped from 69% to 41%. In contrast, the nonvaccine serotype 19A increased in frequency from 2.1% to 6.6%. None of these changes can be attributed to PCV7 vaccine, as it was not in use in Belgium during the time period studied. There was evidence that MCNS clones flowed from West Flanders to Limburg.
Inhibition of Herpes Simplex Virus Types 1 and 2 In Vitro Infection by Sulfated Derivatives of
Escherichia coli
K5 Polysaccharide
Authors: Pinna Debora , Oreste Pasqua , Coradin Tiziana , Kajaste-Rudnitski Anna , Ghezzi Silvia , Zoppetti Giorgio , Rotola Antonella , Argnani Rafaela , Poli Guido , Manservigi Roberto , Vicenzi Elisa
Published: June 2008

Herpes simplex virus type 1 (HSV-1) and HSV-2 are neurotropic viruses and common human pathogens causing major public health problems such as genital herpes, a sexually transmitted disease also correlated with increased transmission and replication of human immunodeficiency virus type 1 (HIV-1). Therefore, compounds capable of blocking HIV-1, HSV-1, and HSV-2 transmission represent candidate microbicides with a potential added value over that of molecules acting selectively against either infection. We report here that sulfated derivatives of the
Escherichia coli
K5 polysaccharide, structurally highly similar to heparin and previously shown to inhibit HIV-1 entry and replication in vitro, also exert suppressive activities against both HSV-1 and HSV-2 infections. In particular, the N,O-sulfated [K5-N,OS(H)] and O-sulfated epimerized [Epi-K5-OS(H)] forms inhibited the infection of Vero cells by HSV-1 and -2, with 50% inhibitory concentrations (IC
50
) between 3 ± 0.05 and 48 ± 27 nM, and were not toxic to the cells at concentrations as high as 5 μM. These compounds impaired the early steps of HSV-1 and HSV-2 virion attachment and entry into host cells and reduced the cell-to-cell spread of HSV-2. Since K5-N,OS(H) and Epi-K5-OS(H) also inhibit HIV-1 infection, they may represent valid candidates for development as topical microbicides preventing sexual transmission of HIV-1, HSV-1, and HSV-2.
Powerful Bactericidal Activity of Moxifloxacin in Human Leprosy
Authors: Pardillo Fe Eleanor F. , Burgos Jasmin , Fajardo Tranquilino T. , Cruz Eduardo Dela , Abalos Rodolfo M. , Paredes Rose Maria D. , Andaya Cora Evelyn S. , Gelber Robert H.
Published: June 2008

In a clinical trial of moxifloxacin in eight multibacillary leprosy patients, moxifloxacin proved highly effective. In all trial patients, a single 400-mg dose of moxifloxacin resulted in significant killing (
P
≤ 0.006) of
Mycobacterium leprae
, ranging from 82% to 99%, with a mean of 91%. In all instances, no viable bacilli were detected with an additional 3 weeks of daily therapy, this observed rapid bactericidal activity being matched previously only by rifampin. On moxifloxacin therapy, skin lesions cleared exceedingly rapidly with definite improvement observed consistently after eight doses and progressive resolution continuing for the 56 days of the trial. Side effects, toxicities, and laboratory abnormalities were mild, not requiring discontinuation of therapy.
Reduced Biocide Susceptibility in
Candida albicans
Biofilms
Authors: Nett Jeniel E. , Guite Kristie M. , Ringeisen Alex , Holoyda Kathleen A. , Andes David R.
Published: June 2008

Candida
biofilm formation is common during infection and environmental growth. We tested the impacts of three biocides (ethanol [EtOH], H
2
O
2
, and sodium dodecyl sulfate) on
Candida albicans, C. parapsilosis
, and
C. glabrata
biofilms. Higher concentrations of the biocides were required for efficacy against biofilms than for efficacy against planktonic controls. A combination study with two biocides (EtOH and H
2
O
2
) and fluconazole demonstrated that the combination had enhanced efficacy.
CD46 Contributes to the Severity of Group A Streptococcal Infection
Authors: Lövkvist Lena , Sjölinder Hong , Wehelie Rahma , Aro Helena , Norrby-Teglund Anna , Plant Laura , Jonsson Ann-Beth
Published: June 2008

Streptococcus pyogenes(group AStreptococcus) is a human pathogen that causes a wide variety of diseases ranging from uncomplicated superficial infections to severe infections such as streptococcal toxic shock syndrome and necrotizing fasciitis. These bacteria interact with several host cell receptors, one of which is the cell surface complement regulator CD46. In this study, we demonstrate that infection of epithelial cells withS. pyogenesleads to the shedding of CD46 at the same time as the bacteria induce apoptosis and cell death. Soluble CD46 attached to the streptococcal surface, suggesting that bacteria might bind available extracellular CD46 as a strategy to survive and avoid host defenses. The protective role of human CD46 was demonstrated in ex vivo whole-blood assays showing that the growth ofS. pyogeneswas enhanced in blood from mice expressing human CD46. Finally, in vivo experimental infection showed that bacteremia levels, arthritis frequency, and mortality were higher in CD46 transgenic mice than in nontransgenic mice. Taken together, these results argue that bacterial exploitation of human CD46 enhances bacterial survival and represents a novel pathogenic mechanism that contributes to the severity of group A streptococcal disease.
The ScpC Protease of
Streptococcus pyogenes
Affects the Outcome of Sepsis in a Murine Model
Authors: Sjölinder Hong , Lövkvist Lena , Plant Laura , Eriksson Jens , Aro Helena , Jones Allison , Jonsson Ann-Beth
Published: June 2008

The ScpC protease of
Streptococcus pyogenes
degrades interleukin-8 (IL-8), a chemokine that mediates neutrophil transmigration and activation. The ability to degrade IL-8 differs dramatically among clinical isolates of
S. pyogenes
. Bacteria expressing ScpC overcome immune clearance by preventing the recruitment of neutrophils in soft tissue infection of mice. To study the role of ScpC in streptococcal sepsis, we generated an ScpC mutant that did not degrade IL-8 and thus failed to prevent the recruitment of immune cells as well as to cause disease after soft tissue infection. In a murine model of sepsis, challenge with the ScpC mutant resulted in more severe systemic disease with higher bacteremia levels and mortality than did challenge with the wild-type strain. As expected, the blood level of KC, the murine IL-8 homologue, increased in mice infected with the ScpC mutant. However, the elevated KC levels did not influence neutrophil numbers in blood, as it did in soft tissue, indicating that additional factors contributed to neutrophil transmigration in blood. In addition, the absence of ScpC increased tumor necrosis factor, IL-6, and C5a levels in blood, which contributed to disease severity. Thus, the ScpC mutant triggers high neutrophil infiltration but not lethal outcome after soft tissue infection, whereas intravenous infection leads to highly aggressive systemic disease.
Characterization of Human Cellular Immune Responses to NovelMycobacterium tuberculosisAntigens Encoded by Genomic Regions Absent inMycobacterium bovisBCG
Authors: Al-Attiyah R. , Mustafa A. S.
Published: June 2008

Comparative genomics has identified several regions of differences (RDs) between the infectiousMycobacterium tuberculosisand the vaccine strains ofMycobacterium bovisBCG. We aimed to evaluate the cellular immune responses induced by antigens encoded by genes predicted in 11 RDs. Synthetic peptides covering the sequences of RD1, RD4 to RD7, RD9 to RD13, and RD15 were tested for antigen-induced proliferation and secretion of Th1 cytokine, gamma interferon (IFN-γ), by peripheral blood mononuclear cells (PBMC) obtained from culture-proven pulmonary tuberculosis (TB) patients andM. bovisBCG-vaccinated healthy subjects. Among the peptide pools, RD1 induced the best responses in both donor groups and in both assays. In addition, testing of TB patients' PBMC for secretion of proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], interleukin 6 [IL-6], IL-8, and IL-1β), Th1 cytokines (IFN-γ, IL-2, and TNF-β), and Th2 cytokines (IL-4, IL-5, and IL-10) showed differential effects of RD peptides in the secretion of IFN-γ and IL-10, with high IFN-γ/IL-10 ratios (32 to 5.0) in response to RD1, RD5, RD7, RD9, and RD10 and low IFN-γ/IL-10 ratios (<1.0) in response to RD12, RD13, and RD15. Peptide-mixing experiments with PBMC from healthy subjects showed that secretion of large quantities of IL-10 in response to RD12 and RD13 correlated with inhibition of Th1 responses induced by RD1 peptides. In conclusion, our results suggest thatM. tuberculosisRDs can be divided into two major groups—one group that activates PBMC to preferentially secrete IFN-γ and another group that activates preferential secretion of IL-10—and that these two groups of RDs may have roles in protection against and pathogenesis of TB, respectively.