bluuebunny/crossref_metadata_2025 huggingface dataset:
Roles of proteolysis and lipid rafts in the processing of the amyloid precursor protein and prion protein
Authors: Hooper N.M.
Published: April 2005

In the amyloidogenic pathway, the APP (amyloid precursor protein) is proteolytically processed by the β- and γ-secretases to release the Aβ (amyloid-β) peptide that is neurotoxic and aggregates in the brains of patients suffering from Alzheimer's disease. In the non-amyloidogenic pathway, APP is cleaved by α-secretase within the Aβ domain, precluding deposition of intact Aβ peptide. The cellular form of the PrPC (prion protein) undergoes reactive oxygen species-mediated β-cleavage within the copper-binding octapeptide repeats or, alternatively, α-cleavage within the central hydrophobic neurotoxic domain. In addition, PrPC is shed from the membrane by the action of a zinc metalloprotease. Members of the ADAM (a disintegrin and metalloproteinase) family of zinc metalloproteases, notably ADAM10 and TACE (ADAM17) display α-secretase activity towards APP and appear to be responsible for the α-cleavage of PrPC. The amyloidogenic cleavage of APP by the β- and γ-secretases appears to occur preferentially in cholesterol-rich lipid rafts, while the conversion of PrPC into the infectious form PrPSc also appears to occur in these membrane domains.
Introduction to the Kinases in Diabetes Biochemical Society focused meeting: are protein kinases good targets for antidiabetic drugs?
Authors: Coghlan M.P. , Smith D.M.
Published: April 2005

Insulin regulates whole-body glucose homoeostasis by modulating the activities of protein kinases in its target tissues: muscle, liver and fat. Defects in insulin's ability to modulate protein kinase activity lead to ‘insulin resistance’ or impaired insulin action. Insulin resistance in combination with defective insulin secretion from the pancreas results in the elevated blood glucose levels that are characteristic of diabetes mellitus. Pharmacological agents that selectively modulate protein kinase activities in insulin-resistant tissues may act either as insulin-sensitizing or insulin-mimetic drugs. Consistent with this, small molecule modulators of a number of protein kinases have demonstrated efficacy in animal models of insulin resistance and diabetes. Moreover, emerging data in humans suggest that marketed anti-diabetic agents may also act in part through modulating protein kinase activities. This meeting was convened to consider the potential to treat insulin resistance and Type II diabetes by modulating protein kinase activity.
Atypical protein kinase C in insulin action and insulin resistance
Authors: Farese R.V. , Sajan M.P. , Standaert M.L.
Published: April 2005

It now seems clear that aPKC (atypical protein kinase C) isoforms are required for insulin-stimulated glucose transport in muscle and adipocytes. Moreover, there are marked defects in the activation of aPKCs under a variety of insulin-resistant conditions in humans, monkeys and rodents. In humans, defects in aPKC in muscle are seen in Type II diabetes and its precursors, obesity, the obesity-associated polycystic ovary syndrome and impaired glucose tolerance. These defects in muscle aPKC activation are due to both impaired activation of insulin receptor substrate-1-dependent PI3K (phosphoinositide 3-kinase) and the direct activation of aPKCs by the lipid product of PI3K, PI-3,4,5-(PO4)3. Although it is still uncertain which underlying defect comes first, the resultant defect in aPKC activation in muscle most certainly contributes significantly to the development of skeletal muscle insulin resistance. Of further note, unlike the seemingly ubiquitous presence of defective aPKC activation in skeletal muscle in insulin-resistant states, the activation of aPKC is normal or increased in livers of Type II diabetic and obese rodents. The maintenance of aPKC activation in the liver may explain how insulin-dependent lipid synthesis is maintained in these states, as aPKCs function mainly in the activation of enzymes important for lipid synthesis. Thus increased activation of liver aPKC in hyperinsulinaemic states may contribute significantly to the development of hyperlipidaemia in insulin-resistant states.
AMP-activated protein kinase and the metabolic syndrome
Authors: Fryer L.G.D. , Carling D.
Published: April 2005

The occurrence of Type II (non-insulin-dependent) diabetes and obesity and their associated morbidities continue to increase and they are rapidly reaching epidemic proportions. AMPK (AMP-activated protein kinase) was initially thought of as an intracellular ‘fuel gauge’ responding to a decrease in the level of ATP by increasing energy production and decreasing energy utilization. Recent studies have shown that AMPK plays a role in controlling the whole body energy homoeostasis, including the regulation of plasma glucose levels, fatty acid oxidation and glycogen metabolism. In addition to its effects on the periphery, AMPK has been found to play a key role in the control of food intake through its regulation by hormones, including leptin, within the hypothalamus. The control of AMPK activity, therefore, provides an attractive target for therapeutic intervention in metabolic disorders such as obesity and Type II diabetes. Indeed, a number of physiological and pharmacological factors that are beneficial in these disorders have been shown to act, at least in part, through the activation of AMPK.
PDH kinase inhibitors: a novel therapy for Type II diabetes?
Authors: Mayers R.M. , Leighton B. , Kilgour E.
Published: April 2005

The pyruvate dehydrogenase multienzyme complex catalyses the oxidative decarboxylation of pyruvate, which is an important regulatory step in oxidative metabolism. Phosphorylation of the E1 (pyruvate decarboxylase) subunit on one of three specific serine residues results in loss of enzyme activity. Four dedicated PDHK (pyruvate dehydrogenase kinase) isoenzymes have been identified, each of which display a distinct tissue-specific expression profile, and have differential regulatory properties. Thus PDHK play a key role in controlling the balance between glucose and lipid oxidation according to substrate supply. Increasing glucose oxidation by inhibiting PDHK may be an effective mechanism to increase glucose utilization; additionally, increasing pyruvate oxidation may further contribute to lowering of glucose level by decreasing the supply of gluconeogenic substrates. A number of PDHK inhibitors are now available to enable this mechanism to be evaluated as a therapy for diabetes. The isoenzyme selectivity profile of AZD7545 and related compounds will be described and evidence for their non-ATP-competitive mode of action presented. These compounds increase PDH activity in vivo, and when dosed chronically, improve glycaemic control in Zucker rats. Furthermore, glucose lowering has been demonstrated in the hyperglycaemic Zucker diabetic fatty rat. This result supports the hypothesis that inhibition of PDHK may be an effective therapy for Type II diabetes.
Storage reserve mobilization in germinating oilseeds: Arabidopsis as a model system
Authors: Penfield S. , Graham S. , Graham I.A.
Published: April 2005

Germinating oilseeds break down fatty acids through peroxisomal β-oxidation and convert the carbon into soluble carbohydrates through the glyoxylate cycle and gluconeogenesis. This interconversion is unique among higher eukaryotes. Using a combination of forward and reverse genetic screens, we have isolated mutants that compromise fatty acid breakdown at each step. These mutants exhibit characteristic, yet nonidentical, seedling establishment phenotypes that can be rescued by the provision of an alternative carbon source. In addition, we have recently shown that Arabidopsis seed's lipid breakdown occurs in two distinct tissues, the embryo and endosperm. The utilization of endospermic lipid reserves requires gluconeogenesis and transport of the resulting sugars to the germinating embryo. We discuss the potential of the Arabidopsis endosperm tissue as a simplified model system for the study of germination and lipid breakdown in germinating oilseeds.
The molecular biology of appressorium turgor generation by the rice blast fungus Magnaporthe grisea
Authors: Wang Z.-Y. , Jenkinson J.M. , Holcombe L.J. , Soanes D.M. , Veneault-Fourrey C. , Bhambra G.K. , Talbot N.J.
Published: April 2005

The rice blast fungus Magnaporthe grisea develops specialized infection structures known as appressoria, which develop enormous turgor pressure to bring about plant infection. Turgor is generated by accumulation of compatible solutes, including glycerol, which is synthesized in large quantities in the appressorium. Glycogen, trehalose and lipids represent the most abundant storage products in M. grisea conidia. Trehalose and glycogen are rapidly degraded during conidial germination and it is known that trehalose synthesis is required for virulence of the fungus. Lipid bodies are transported to the developing appressoria and degraded at the onset of turgor generation, in a process that is cAMP-dependent. A combined biochemical and genetic approach is being used to dissect the process of turgor generation in the rice blast fungus.
Serpentine plant MLO proteins as entry portals for powdery mildew fungi
Authors: Panstruga R.
Published: April 2005

In the dicotyledonous plant species Arabidopsis and the monocot barley, presence of specific isoforms of the family of heptahelical plasma membrane-localized MLO proteins is required for successful host-cell invasion by ascomycete powdery mildew fungi. Absence of these MLO proteins, either caused by natural polymorphisms or induced lesions in the respective Mlo genes, results in failure of fungal sporelings to penetrate the plant cell wall. As a consequence, recessively inherited cell-autonomous mlo resistance is effective against all known isolates of powdery mildew fungi colonizing either barley or Arabidopsis. Barley MLO interacts constitutively with the cytoplasmic calcium sensor calmodulin, but the strength of this interaction increases transiently during fungal pathogenesis. In addition, MLO as well as ROR2, a plasma membrane-resident syntaxin also implicated in mlo penetration resistance, focally accumulate at sites of attempted fungal attack, thereby defining a novel pathogen-triggered micro-domain. In conclusion, powdery mildew fungi appear to specifically corrupt MLO to modulate vesicle-associated processes at the plant cell periphery for successful pathogenesis.
Soluble adhesion molecules in inflammatory and vascular diseases
Authors: Giddings J.C.
Published: April 2005

For many years the vascular endothelium was believed simply to provide a passive lining between circulating blood and extravascular tissue. It is now clear, however, that this monolayer of cells on the luminal surface of all blood vessels, provides a selective barrier that responds dynamically to various stimuli, and controls a complex series of cellular reactions and interactions. The current presentation describes the use of computer enhanced video recording to study interactions between endothelial cells and circulating blood cells, especially leucocytes. Subsequently, modern assays for soluble cell adhesion molecules and other cell receptors were assessed for potential use in routine clinical practice. The results demonstrated that adhesive mechanisms involving leucocytes and endothelial cells involve a range of interrelationships that cut across conventional views of haemostasis and leucocyte function. The findings also suggest that interplay between the vascular lumen and circulating blood cells might be vitally important in clinically demanding pathologies, such as life-threatening sepsis, ischaemic heart disease, atherosclerosis and cancer. The concepts provide challenging strategies for further investigation.
Using proteomics to identify potential therapeutic targets in platelets
Authors: Maguire P.B. , Foy M. , Fitzgerald D.J.
Published: April 2005

Proteomics has provided powerful new insights into the complex events of the anucleate platelet and has revealed many potential protein targets in the search for suitable agents for thrombotic disease. In the present study, we summarize recent proteomic approaches to analyse specific platelet subproteomes, such as the platelet releasate, the platelet phosphotyrosine proteome and characterization of the proteins associated with membrane lipid rafts.
Polyunsaturated fatty acids and inflammation
Authors: Calder P.C.
Published: April 2005

The n–6 polyunsaturated fatty acid, arachidonic acid, is a precursor of prostaglandins, leukotrienes and related compounds that have important roles as mediators and regulators of inflammation. Consuming increased amounts of long chain n–3 polyunsaturated fatty acids (found in oily fish and fish oils) results in a partial replacement of the arachidonic acid in cell membranes by eicosapentaenoic and docosahexaenoic acids. This leads to decreased production of arachidonic acid-derived mediators. This alone is a potentially beneficial anti-inflammatory effect of n–3 fatty acids. However, n–3 fatty acids have a number of other effects that might occur downstream of altered eicosanoid production or are independent of this. For example, they result in suppressed production of pro-inflammatory cytokines and can modulate adhesion molecule expression. These effects occur at the level of altered gene expression.
Haemostasis in normal pregnancy: a balancing act?
Authors: Holmes V.A. , Wallace J.M.W.
Published: April 2005

Pregnancy is a risk factor for venous thrombosis and the incidence of venous thromboembolism during normal pregnancy is 6-fold higher during pregnancy than in the general female population of child-bearing age. This incidence is, however, remarkably low given the increases in markers of haemostatic activation observed during normal pregnancy. During normal healthy pregnancy there are substantial changes in the haemostatic system, many of which are procoagulant and supposed to be in preparation for the haemostatic challenge of delivery. Normal haemostasis requires a balance between coagulation and fibrinolysis to maintain the integrity of the vasculature, and complex physiological changes are evident during pregnancy which appear to ensure a constant coagulation/fibrinolysis balance. This balance is maintained, at least partly, by an increase in fibrinolytic activity, but decreases in other factors such as factor XI and monocyte tissue factor expression may also serve to counterbalance procoagulant changes.
Microsatellite markers for heart of palm –Euterpe edulis and E. oleracea Mart. (Arecaceae)
Authors: Gaiotto F. A. , Brondani R. P. V. , Grattapaglia D.
Published: April 2005

Euterpe edulis is the species of palm found in the Atlantic Forest and Cerrado gallery forest that yields the best heart of palm. A battery of 18 highly polymorphic microsatellite markers was developed from an enriched genomic library. Using fluorescence automated detection an average of 10.6 alleles per locus were found on a sample of 66 individuals sampled from a natural population. These loci allow extremely precise paternity testing, estimation of gene flow and of parentage coefficients among trees in the wild.
Environmental Constraints on Phenology and Internal Nutrient Cycling in the Mediterranean Winter‐Deciduous Shrub Amelanchier ovalis Medicus
Authors: Milla R. , Castro‐Díez P. , Maestro‐Martínez M. , Montserrat‐Martí G.
Published: April 2005

Abstract: The functional adjustments of winter‐deciduous perennials to Mediterranean conditions have received little attention. The objectives of this study were: (i) to determine whether Amelanchier ovalis, a winter‐deciduous shrub of Mediterranean and sub‐Mediterranean regions, has nutritional and phenological traits in common with temperate zone deciduous trees and shrubs and (ii) to determine the constraints of Mediterranean environmental conditions on these traits. Over two years, phenology and nitrogen, and phosphorus concentrations were monitored monthly in the crown of A. ovalis. Leaf longevity, survival and nutrient resorption from senescing leaves were used to infer nutrient use efficiency and retention times of nutrients within the crown. In A. ovalis, bud burst was much earlier than in temperate deciduous trees and shrubs. Most vegetative and reproductive growth occurred in spring. Limited phenological development took place during the summer drought period. Unexpectedly, leaf shedding was very gradual, which might be related to water shortages in summer. Leaf longevity, nutrient resorption from senescing leaves, and maximum leaf nutrient concentrations indicated that nutrient retention times were short and nutrient use efficiency was low compared to that found in temperate deciduous plants and co‐occurring Mediterranean evergreens. A. ovalis exhibited phenological development appropriate for a Mediterranean climate, although its limited ability to retain nutrients likely restricts the types of sites that it can occupy.
Managing Expectations and Benefits: A Model for Electronic Trading and EDI in the Insurance Industry
Authors: Fearon Colm , Philip George
Published: April 2005

This paper investigates the role of insurer and broker expectations in achieving long-term benefit success from electronic trading in the insurance industry. The paper highlights the importance of intra- and inter-organisational expectations with the implementation of electronic data intercharge, as a major electronic trading initiative within the insurance industry. A benefits management model is conceptualised to explore the effects of competitive stimuli and depict the technology management response of insurers and brokers within the case study. The model highlights the importance of managing benefits and expectations in developing long-term partnerships for the successful implementation of electronic trading. The technology management response among key stakeholders and the roles of communication, coordination and support during the implementation phase are also discussed. Finally, a number of lessons are recommended, which should be of use to practitioners and concluding remarks indicate areas for future research.
Floret development and survival in wheat plants exposed to contrasting photoperiod and radiation environments during stem elongation
Authors: González Fernanda G. , Slafer Gustavo A. , Miralles Daniel J.
Published: April 2005

Wheat breeding has improved yield potential increasing floret survival through higher dry matter partitioning to the spikes during the stem elongation phase (from terminal spikelet initiation to anthesis). We studied survival of floret primodia in different spikelet positions along the spike in relation to dynamics of spike growth, when dynamics of dry matter partitioning to the spike was altered by photoperiod and shading treatments applied during the stem elongation phase. The cultivar Buck Manantial was exposed to (1) NP+0 un-shaded (natural photoperiod and incoming radiation of the growing season), (2) NP+0 shaded (natural photoperiod but only 33% of the incoming radiation), and (3) NP+6 un-shaded (natural photoperiod extended 6 h and natural incoming radiation). Floret survival increased, depending on spikelet position, 1.1–2.5 fold under un-shaded v. shaded treatments (both under NP+0), and 1.3–1.8 fold under NP+0 v. NP+6 treatments (both un-shaded), without any impact of treatments on the total number of initiated floret primordia. The fate of the floret primordia and its final stage at anthesis were associated with duration of floret development within the stem elongation phase (R2 = 82%, P<0.0001). Florets may be classified into three groups: (i) those that were fertile at anthesis under all treatments (mostly the two florets F1 and F2, proximal to the rachis within the spikelet), (ii) those that reached different stages at anthesis, depending on treatment, and that contributed differentially to the number of fertile florets at anthesis (mostly the florets F3, F4 and F5, positioned in the middle of the spikelet), and (iii) those that did not contribute to the number of fertile florets under any treatment (mostly the florets ≥ F6). Degeneration of florets in group (ii) was associated with spike growth at maximum rate, explaining the strong relationship observed between spike dry weight at anthesis and number of fertile florets. However, degeneration of florets in group (iii) seemed to occur before spike growth at maximum rate. Survival of florets positioned in the middle of the spikelets could be improved by increasing spike growth through manipulation of photoperiod sensitivity during stem elongation.
Elevated CO2 protects poplar (Populus trichocarpa × P. deltoides) from damage induced by O3: identification of mechanisms
Authors: Gardner Simon D. L. , Freer-Smith Peter H. , Tucker J. , Taylor Gail
Published: April 2005

CO2 concentrations in the Earth’s atmosphere will rise to between 550 and 700 μL L–1 by 2100 (IPCC 2001). In much of the world, ozone (O3) is the air pollutant most likely to be having adverse effects on the growth of plants. Here we describe the impacts of CO2 and O3 episodes (rising to 100 nL L–1), singly and in mixtures on the growth and physiology of an interamerican hybrid poplar (Populus trichocarpa L. (Torr. & Gray ex Hook.) × P. deltoids Bartr. ex Marsh). 700 μL L–1 CO2 increased all growth variables relative to values in 350 μL L–1. Mainstem dry weight showed a 38% increase in year 1 and a 32% increase in year 2. Ozone episodes reduced mainstem dry mass by 45% in 350 μL L–1 CO2 and by 34% in 700 μL L–1 CO2. A / Ci analysis showed limited effects on photosynthetic efficiency of 700 μL L–1 CO2 but in contrast, Vcmax was reduced by O3 episodes. CO2 tended to increase leaf expansion but O3 episodes reduced expansion rates generally although a short period of increased leaf expansion in response to O3 was also observed. O3 reduced leaf solute potentials (Ψs) and increased turgor (P) in young leaves. Cell wall properties (elasticity and plasticity) were both stimulated by ozone and this was associated with increased leaf expansion. A new mechanism is proposed which suggests that O3 may act directly on the cell wall, attacking polysaccharides in the wall that result in altered cell wall properties and leaf growth. O3 episodes increased leaf loss, elevated CO2 delayed abscission and O3 was less effective at accelerating leaf loss in elevated CO2. Overall CO2 increased growth, O3 caused decreases and the treatment combination gave intermediate effects. Thus O3 episodes are less likely to be detrimental to P. trichocarpa × P. deltoides in the CO2 concentrations of the future.
Nitrate reductase in durum wheat seedlings as affected by nitrate nutrition and salinity
Authors: Carillo Petronia , Mastrolonardo Gabriella , Nacca Francesco , Fuggi Amodio
Published: April 2005

The combined effects of nitrate (0, 0.1, 1, 10 mm) and salt (0, 100 mm NaCl) on nitrogen metabolism in durum wheat seedlings were investigated by analysis of nitrate reductase (NR) expression and activity, and metabolite content. High salinity (100 mm NaCl) reduced shoot growth more than root growth. The effect was independent of nitrate concentration. NR mRNA was present at a low level in both leaves and roots of plants grown in a nitrogen-free medium. NaCl increased NR mRNA at low nitrate, suggesting that chloride can mimic nitrate as a signal molecule to induce transcription in both roots and leaves. However, the level of NR protein remained low in salt-stressed plants, indicating an inhibitory effect of salt on translation of NR mRNA or an increase in protein degradation. The lower activity of nitrate reductase in leaves of high-nitrate treated plants under salinity suggested a restriction of NO3– transport to the shoot under salinity. Salt treatment promoted photorespiration, inhibiting carbohydrate accumulation in plants grown on low nitrate media. Under salinity free amino acids, in particular proline and asparagine, and glycine betaine could function as osmolytes to balance water potential within the cell, especially when nitrogen availability exceeded the need for growth.
WM5: Isolation and characterisation of a gene expressed during early meiosis and shoot meristem development in wheat
Authors: Dong Chongmei , Thomas Stephen , Becker Dirk , Lörz Horst , Whitford Ryan , Sutton Tim , Able Jason A. , Langridge Peter
Published: April 2005

Wheat Meiosis 5 (WM5), isolated from an early meiosis anther cDNA library of wheat by cDNA subtraction encodes a novel glycine–serine–proline–alanine-rich protein. The corresponding homologous genes are located on the short arms of chromosomes 3A, 3B and 3D of allohexaploid wheat (Triticum aestivum L.). The copy on 3DS is located within the region deleted in the wheat mutant ph2a that displays increased homoeologous chromosome pairing in crosses with alien species. While WM5 is expressed primarily in young flower buds during early meiosis it is also expressed in shoot meristems, thus indicating functional roles in both meiosis and meristem development. Overall, the WM5 amino acid sequence shares no significant similarity with other known proteins in the NCBI database. However, the carboxyl-terminal region does have similarity with the Arabidopsis PDF1 (Protodermal Factor 1) protein. Comparing WM5 and PDF1 reveals that the two proteins share 33% identity and have similar hydropathy plots and predicted secondary structures. In situ immuno-staining locates the protein to the nuclei of pollen mother cells undergoing meiosis and the epidermal layer of the shoot and flower meristem, including the cell wall and cuticle. We propose that the WM5 protein has a role in shoot and flower development within this economically important cereal crop.
Effect of aluminium on membrane potential and ion fluxes at the apices of wheat roots
Authors: Wherrett Tim , Ryan Peter R. , Delhaize Emmanuel , Shabala Sergey
Published: April 2005

Aluminium (Al) tolerance in wheat (Triticum aestivum L.) is associated with the Al-activated efflux of malate and K+ from the root apices. We tested the hypothesis that these Al-activated ion fluxes would induce changes in the membrane potential (Vm) and that these responses would differ between wheat genotypes that differ in Al tolerance. Within minutes of exposing wheat roots to 50 μm AlCl3, a significant depolarisation was measured in the Al-tolerant ET8 genotype but not in a near-isogenic, Al-sensitive genotype, ES8. We investigated the ion movements that may be responsible for these changes in Vm by measuring real-time fluxes of Cl–, H+ and K+ at the root apices of wheat seedlings using the non-invasive microelectrode ion flux estimation (MIFE) technique. Addition of 50 μm AlCl3 to the bathing solution stimulated an increase in K+ efflux and H+ influx in ET8 but not in ES8. The differences between the genotypes were sustained for 24 h and were observed only at the elongating zone and not the meristematic zone. After 24 h Al increased Cl– influx in ET8 but inhibited ES8 influx in a dose-dependent manner. These results provide new temporal and spatial information on the Al-activated ion fluxes from intact wheat plants.
Olfactory expression of a single and highly variable V1r pheromone receptor-like gene in fish species
Authors: Pfister Patrick , Rodriguez Ivan
Published: April 2005

Sensory neurons expressing members of the seven-transmembrane V1r receptor superfamily allow mice to perceive pheromones. These receptors, which exhibit no sequence homology to any known protein except a weak similarity to taste receptors, have only been found in mammals. In the mouse, the V1r repertoire contains >150 members, which are expressed by neurons of the vomeronasal organ, a structure present exclusively in some tetrapod species. Here, we report the existence of a single V1r gene in multiple species of a non-terrestrial, vomeronasal organ-lacking taxon, the teleosts. In zebrafish, this V1r gene is expressed in chemosensory neurons of the olfactory rosette with a punctate distribution, strongly suggesting a role in chemodetection. This unique receptor gene exhibits a remarkably high degree of sequence variability between fish species. It likely corresponds to the original V1r present in the common ancestor of vertebrates, which led to the large and very diverse expansion of vertebrate pheromone receptor repertoires, and suggests the presence of V1rs in multiple nonmammalian phyla.
Calbindin D28k targets
myo
-inositol monophosphatase in spines and dendrites of cerebellar Purkinje neurons
Authors: Schmidt Hartmut , Schwaller Beat , Eilers Jens
Published: April 2005

The Ca
2+
-binding protein calbindin D28k (CB) is vital for the normal function of the central nervous system but its specific functional role is largely unclear. CB is typically described as a mobile Ca
2+
buffer that shapes the spatiotemporal extent of cellular Ca
2+
signals. Recent biochemical data, however, indicate that CB also has characteristics of a Ca
2+
sensor and activates
myo
-inositol monophosphatase (IMPase), a key enzyme of the inositol-1,4,5-trisphosphate signaling cascade and an assumed target of mood-stabilizing drugs in the treatment of bipolar disorder. Here, we show that CB interacts with IMPase in cerebellar Purkinje neurons, a cell type well known to rely on inositol-1,4,5-trisphosphate-dependent synaptic integration. Quantification of the mobility of dye-labeled CB with two-photon fluorescence recovery after photobleaching revealed that a substantial fraction of CB is immobilized in spines and dendrites, but not in axons. Immobilization occurs over several seconds, is increased by suprathreshold synaptic activity, and can be relieved by a synthetic peptide that resembles the putative CB-binding site of IMPase, indicating that CB binds to immobilized IMPase. Measurements of the apparent diffusion coefficients of CB imply that CB does not interact with cytosolic IMPase or that the latter is present only in minute amounts in the spiny dendrites of Purkinje neurons. Our results suggest that CB acts as an activity-dependent sensor that targets membrane/cytoskeleton-bound IMPase in central neurons.
Molecular structure of the lecithin ripple phase
Authors: de Vries Alex H. , Yefimov Serge , Mark Alan E. , Marrink Siewert J.
Published: April 2005

Molecular dynamics simulations of lecithin lipid bilayers in water as they are cooled from the liquid crystalline phase show the spontaneous formation of rippled bilayers. The ripple consists of two domains of different length and orientation, connected by a kink. The organization of the lipids in one domain of the ripple is found to be that of a splayed gel; in the other domain the lipids are gel-like and fully interdigitated. In the concave part of the kink region between the domains the lipids are disordered. The results are consistent with the experimental information available and provide an atomic-level model that may be tested by further experiments.
Structural and numerical chromosome changes in colon cancer develop through telomere-mediated anaphase bridges, not through mitotic multipolarity
Authors: Stewénius Ylva , Gorunova Ludmila , Jonson Tord , Larsson Nina , Höglund Mattias , Mandahl Nils , Mertens Fredrik , Mitelman Felix , Gisselsson David
Published: April 2005

Telomere dysfunction has been associated with chromosomal instability in colorectal carcinoma, but the consequences of telomere-dependent instability for chromosome integrity and clonal evolution have been little explored. We show here that abnormally short telomeres lead to a wide spectrum of mitotic disturbances in colorectal cancer cell lines, including anaphase bridging, whole-chromosome lagging, and mitotic multipolarity. These abnormalities were found in both the presence and absence of microsatellite instability. The mean telomere length varied extensively between cells from the same tumor, allowing the establishment of tumor cell subpopulations with highly different frequencies of mitotic disturbances. Anaphase bridging typically resulted in either inter-centromeric chromatin fragmentation or centromere detachment, leading to pericentromeric chromosome rearrangements and loss of whole chromosomes, respectively. There was a strong correlation between anaphase bridges and multipolar mitoses, and the induction of dicentric chromosomes by gamma irradiation and telomerase inhibition led to an elevated frequency of multipolar mitotic spindles, suggesting that multipolarity could result from polyploidization triggered by anaphase bridging. Chromatid segregation in multipolar mitoses was close to random, resulting in frequent nullisomies and nonviable daughter cells. In contrast, there was a high clonogenic survival among cells having gone through anaphase bridging in bipolar mitoses. Bridging of telomere-deficient chromosomes could thus be a major mutational mechanism in colorectal cancer, whereas mitotic multipolarity appears to be a secondary phenomenon that rarely, if ever, contributes to clonal evolution.
Vertex operator algebras, the Verlinde conjecture, and modular tensor categories
Authors: Huang Yi-Zhi
Published: April 2005

Let
V
be a simple vertex operator algebra satisfying the following conditions: (
i
)
V
(

n

)
= 0 for
n
< 0,

\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\setlength{\oddsidemargin}{-69pt}
\begin{document}
\begin{equation*}V_{0}={\mathbb{C}}1\end{equation*}\end{document}

, and the contragredient module
V
' is isomorphic to
V
as a
V
-module; (
ii
) every

\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\setlength{\oddsidemargin}{-69pt}
\begin{document}
\begin{equation*}{\mathbb{N}}{\mathrm{-}}{\mathrm{gradable}}\end{equation*}\end{document}

weak
V
-module is completely reducible; (
iii
)
V
is
C
2
-cofinite. We announce a proof of the Verlinde conjecture for
V
, that is, of the statement that the matrices formed by the fusion rules among irreducible
V
-modules are diagonalized by the matrix given by the action of the modular transformation τ → –1/τ on the space of characters of irreducible
V
-modules. We discuss some consequences of the Verlinde conjecture, including the Verlinde formula for the fusion rules, a formula for the matrix given by the action of τ → –1/τ, and the symmetry of this matrix. We also announce a proof of the rigidity and nondegeneracy property of the braided tensor category structure on the category of
V
-modules when
V
satisfies in addition the condition that irreducible
V
-modules not equivalent to
V
have no nonzero elements of weight 0. In particular, the category of
V
-modules has a natural structure of modular tensor category.
Cyclization of short DNA fragments and bending fluctuations of the double helix
Authors: Du Quan , Smith Chaim , Shiffeldrim Nahum , Vologodskaia Maria , Vologodskii Alexander
Published: April 2005

Cloutier and Widom [Cloutier, T. E. & Widom, J. (2004)
Mol. Cell
14, 355–362] recently reported that the cyclization efficiency of short DNA fragments, about 100 bp in length, exceeds theoretical expectations by three orders of magnitude. In an effort to resolve this discrepancy, we tried modifying the theory. We investigated how the distribution of the angles between adjacent base pairs of the double helix affects the cyclization efficiency. We found that only the incorporation of sharp kinks in the angle distribution provides the desired increase of the cyclization efficiency. We did not find a model, however, that fits all cyclization data for DNA fragments of different lengths. Therefore, we carefully reinvestigated the cyclization of 100-bp DNA fragments experimentally and found their cyclization efficiency to be in remarkable agreement with the traditional model of DNA bending. We also found an explanation for the discrepancy between our results and those of Cloutier and Widom.
Burn injury causes mitochondrial dysfunction in skeletal muscle
Authors: Padfield Katie E. , Astrakas Loukas G. , Zhang Qunhao , Gopalan Suresh , Dai George , Mindrinos Michael N. , Tompkins Ronald G. , Rahme Laurence G. , Tzika A. Aria
Published: April 2005

Severe burn trauma is generally followed by a catabolic response that leads to muscle wasting and weakness affecting skeletal musculature. Here, we perform whole-genome expression andin vivoNMR spectroscopy studies to define respectively the full set of burn-induced changes in skeletal muscle gene expression and the role of mitochondria in the altered energy expenditure exhibited by burn patients. Our results show 1,136 genes differentially expressed in a mouse hind limb burn model and identify expression pattern changes of genes involved in muscle development, protein degradation and biosynthesis, inflammation, and mitochondrial energy and metabolism. To assess further the role of mitochondria in burn injury, we performedin vivo31P NMR spectroscopy on hind limb skeletal muscle, to noninvasively measure high-energy phosphates and the effect of magnetization transfer on inorganic phosphate (Pi) and phosphocreatine (PCr) resonances during saturation of γATP resonance, mediated by the ATP synthesis reactions. Although local burn injury does not alter high-energy phosphates or pH, apart from PCr reduction, it does significantly reduce the rate of ATP synthesis, to further implicate a role for mitochondria in burn trauma. These results, in conjunction with our genomic results showing down-regulation of mitochondrial oxidative phosphorylation and related functions, strongly suggest alterations in mitochondrial-directed energy expenditure reactions, advancing our understanding of skeletal muscle dysfunction suffered by burn injury patients.
Diverse taxa of cyanobacteria produce β-
N
-methylamino-
l
-alanine, a neurotoxic amino acid
Authors: Cox Paul Alan , Banack Sandra Anne , Murch Susan J. , Rasmussen Ulla , Tien Georgia , Bidigare Robert Richard , Metcalf James S. , Morrison Louise F. , Codd Geoffrey A. , Bergman Birgitta
Published: April 2005

Cyanobacteria can generate molecules hazardous to human health, but production of the known cyanotoxins is taxonomically sporadic. For example, members of a few genera produce hepatotoxic microcystins, whereas production of hepatotoxic nodularins appears to be limited to a single genus. Production of known neurotoxins has also been considered phylogenetically unpredictable. We report here that a single neurotoxin, β-
N
-methylamino-
l
-alanine, may be produced by all known groups of cyanobacteria, including cyanobacterial symbionts and free-living cyanobacteria. The ubiquity of cyanobacteria in terrestrial, as well as freshwater, brackish, and marine environments, suggests a potential for wide-spread human exposure.
Wheat archive links long-term fungal pathogen population dynamics to air pollution
Authors: Bearchell Sarah J. , Fraaije Bart A. , Shaw Michael W. , Fitt Bruce D. L.
Published: April 2005

We used the PCR to study the presence of two plant pathogens in archived wheat samples from a long-term experiment started in 1843. The data were used to construct a unique 160-yr time-series of the abundance of
Phaeosphaeria nodorum
and
Mycosphaerella graminicola
, two important pathogens of wheat. During the period since 1970, the relative abundance of DNA of these two pathogens in the samples has reflected the relative importance of the two wheat diseases they cause in U.K. disease surveys. Unexpectedly, changes in the ratio of the pathogens over the 160-yr period were very strongly correlated with changes in atmospheric pollution, as measured by SO
2
emissions. This finding suggests that long-term, economically important, changes in pathogen populations can be influenced by anthropogenically induced environmental changes.
A pivotal role of calcineurin signaling in development and maturation of postnatal cerebellar granule cells
Authors: Sato Masaaki , Suzuki Kazunori , Yamazaki Hiroshi , Nakanishi Shigetada
Published: April 2005

Primary culture of postnatal cerebellar granule cells provides a model system that recapitulates many molecular events of developing granule cellsin vivo. Depolarization of cultured granule cells increases intracellular Ca2+and activates Ca2+/calmodulin-dependent calcineurin (CaN) phosphatase. This Ca2+signaling mimics some of the signaling events for proliferation, migration, and differentiation of granule cellsin vivo. We investigated the genome-wide expression profiles of depolarization- and CaN-regulated genes in cultured mouse granule cells and addressed their relevance to gene regulation in developing granule cellsin vivo. Granule cells were cultured under a nondepolarization condition (5 mM KCl) and a depolarization condition (25 mM KCl) with and without the CaN inhibitor FK506. Gene expression profiles between depolarization and nondepolarization and between FK506 treatment and untreatment were analyzed by microarray techniques. Both depolarization and FK506 treatment influence expression levels of a large number of genes, most of which are overlapping, however, are conversely regulated by these two treatments. Importantly, many of the FK506-responsive genes are up- or down-regulated in parallel with gene expression in postnatal granule cellsin vivo. The FK506-down-regulated genes are highly expressed in proliferating/premigratory granule cells and many of these genes encode cellular components involved in cell proliferation, migration, and differentiation. In contrast, the FK506-up-regulated genes are predominantly expressed in postmigratory granule cells, including many functional molecules implicated in synaptic transmission and modulation. This investigation demonstrates that the CaN signaling plays a pivotal role in development and synaptic organization of granule cells during the postnatal period.
Life history biology of early land plants: Deciphering the gametophyte phase
Authors: Taylor Thomas N. , Kerp Hans , Hass Hagen
Published: April 2005

Theca.400-million-year-old Rhynie chert biota represents a benchmark for studies of early terrestrial ecosystems. The exquisite preservation of the organisms documents an ancient biodiversity that also includes various levels of biological interaction. Absent from the picture until recently has been detailed information about the development of the gametophyte phase and the alternation of generations of the macroplants in this ecosystem. Here, we trace the development of the gametophyte phase ofAglaophyton, an early land plant with an unusual complement of structural and morphological characters. Mature gametophytes consist of a fleshy protocorm attached to the substrate by basal rhizoids; arising from the upper surface are one to several upright gametangiophores bearing multiple gametangia. Stomata are present on the upper surface of the protocorm and gametangiophore, and endomycorrhizal fungi extend throughout the gametophyte. Gametophytes are unisexual, producing either antheridiophores or archegoniophores. There is no evidence that gametophytes later become hermaphroditic. The sexual dimorphism of the Rhynie chert gametophytes is inconsistent with theoretical ideas about the haploid phase of early land plants. The gametophyte phase of early land plants can now be considered within an ecological and evolutionary framework that, in turn, can be used to develop hypotheses about some aspects of the population dynamics and growth of these early land plants.
PI(4,5)P2-dependent microdomain assemblies capture microtubules to promote and control leading edge motility
Authors: Golub Tamara , Caroni Pico
Published: April 2005

The lipid second messenger PI(4,5)P2 modulates actin dynamics, and its local accumulation at plasmalemmal microdomains (rafts) might mediate regulation of protrusive motility. However, how PI(4,5)P2-rich rafts regulate surface motility is not well understood. Here, we show that upon signals promoting cell surface motility, PI(4,5)P2 directs the assembly of dynamic raft-rich plasmalemmal patches, which promote and sustain protrusive motility. The accumulation of PI(4,5)P2 at rafts, together with Cdc42, promotes patch assembly through N-WASP. The patches exhibit locally regulated PI(4,5)P2 turnover and reduced diffusion-mediated exchange with their environment. Patches capture microtubules (MTs) through patch IQGAP1, to stabilize MTs at the leading edge. Captured MTs in turn deliver PKA to patches to promote patch clustering through further PI(4,5)P2 accumulation in response to cAMP. Patch clustering restricts, spatially confines, and polarizes protrusive motility. Thus, PI(4,5)P2-dependent raft-rich patches enhance local signaling for motility, and their assembly into clusters is regulated through captured MTs and PKA, coupling local regulation of motility to cell polarity, and organization.
The subendothelial extracellular matrix modulates NF-κB activation by flow
Authors: Orr A. Wayne , Sanders John M. , Bevard Melissa , Coleman Elizabeth , Sarembock Ian J. , Schwartz Martin Alexander
Published: April 2005

Atherosclerotic plaque forms in regions of the vasculature exposed to disturbed flow. NF-κB activation by fluid flow, leading to expression of target genes such as E-selectin, ICAM-1, and VCAM-1, may regulate early monocyte recruitment and fatty streak formation. Flow-induced NF-κB activation is downstream of conformational activation of integrins, resulting in new integrin binding to the subendothelial extracellular matrix and signaling. Therefore, we examined the involvement of the extracellular matrix in this process. Whereas endothelial cells plated on fibronectin or fibrinogen activate NF-κB in response to flow, cells on collagen or laminin do not. In vivo, fibronectin and fibrinogen are deposited at atherosclerosis-prone sites before other signs of atherosclerosis. Ligation of integrin α2β1 on collagen prevents flow-induced NF-κB activation through a p38-dependent pathway that is activated locally at adhesion sites. Furthermore, altering the extracellular matrix to promote p38 activation in cells on fibronectin suppresses NF-κB activation, suggesting a novel therapeutic strategy for treating atherosclerosis.
Achlorhydria by ezrin knockdown
Authors: Tamura Atsushi , Kikuchi Shojiro , Hata Masaki , Katsuno Tatsuya , Matsui Takeshi , Hayashi Hisayoshi , Suzuki Yuichi , Noda Tetsuo , Tsukita Shoichiro , Tsukita Sachiko
Published: April 2005

Loss of gastric acid secretion is pathologically known as achlorhydria. Acid-secreting parietal cells are characterized by abundant expression of ezrin (Vil2), one of ezrin/radixin/moesin proteins, which generally cross-link actin filaments with plasma membrane proteins. Here, we show the direct in vivo involvement of ezrin in gastric acid secretion. Ezrin knockout (Vil2−/−) mice did not survive >1.5 wk after birth, making difficult to examine gastric acid secretion. We then generated ezrin knockdown (Vil2kd/kd) mice by introducing a neomycin resistance cassette between exons 2 and 3. Vil2kd/kd mice born at the expected Mendelian ratio exhibited growth retardation and a high mortality. Approximately 7% of Vil2kd/kd mice survived to adulthood. Ezrin protein levels in Vil2kd/kd stomachs decreased to <5% of the wild-type levels without compensatory up-regulation of radixin or moesin. Adult Vil2kd/kd mice suffered from severe achlorhydria. Immunofluorescence and electron microscopy revealed that this achlorhydria was caused by defects in the formation/expansion of canalicular apical membranes in gastric parietal cells.