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Signalling Processes (signalling + process)
Selected AbstractsG,s protein C -terminal ,-helix at the interface: does the plasma membrane play a critical role in the G,s protein functionality?JOURNAL OF PEPTIDE SCIENCE, Issue 10 2005Stefania Albrizio Abstract The heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins, G,,,) mediate the signalling process of a large number of receptors, known as G protein-coupled receptors. The C -terminal domain of the heterotrimeric G protein ,-subunit plays a key role in the selective activation of G proteins by their cognate receptors. The interaction of this domain can take place at the end of a cascade including several successive conformational modifications. G,s(350,394) is the 45-mer peptide corresponding to the C -terminal region of the G,s subunit. In the crystal structure of the G,s subunit it encompasses the ,4/,6 loop, the ,6 ,-sheet segment and the ,5 helix region. Following a previous study based on the synthesis, biological activity and conformational analysis of shorter peptides belonging to the same G,s region, G,s(350,394) was synthesized and investigated. The present study outlines the central role played by the residues involved in the ,4/,6 loop and ,6/,5 loops in the stabilization of the C -terminal G,s,-helix. H2O/2H2O exchange experiments, and NMR diffusion experiments show interesting evidence concerning the interaction between the SDS micelles and the polypeptide. These data prompt intriguing speculations on the role of the intracellular environment/cellular membrane interface in the stabilization and functionality of the C -terminal G,s region. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Fine-Tuning Plant Defence Signalling: Salicylate versus JasmonatePLANT BIOLOGY, Issue 1 2006G. J. M. Beckers Abstract: Plant defences against pathogens and herbivorous insects form a comprehensive network of interacting signal transduction pathways. The signalling molecules salicylic acid (SA) and jasmonic acid (JA) play important roles in this network. SA is involved in signalling processes providing systemic acquired resistance (SAR), protecting the plant from further infection after an initial pathogen attack. SAR is long-lasting and provides broad spectrum resistance to biotrophic pathogens that feed on a living host cell. The regulatory protein NPR1 is a central positive regulator of SAR. SA-activated NPR1 localizes to the nucleus where it interacts with TGA transcription factors to induce the expression of a large set of pathogenesis-related proteins that contribute to the enhanced state of resistance. In a distinct signalling process, JA protects the plant from insect infestation and necrotrophic pathogens that kill the host cell before feeding. JA activates the regulatory protein COI1 that is part of the E3 ubiquitin ligase-containing complex SCFCOI1, which is thought to derepress JA-responsive genes involved in plant defence. Both synergistic and antagonistic interactions have been observed between SA- and JA-dependent defences. NPR1 has emerged as a critical modulator of cross-talk between the SA and JA signal and is thought to aid in fine tuning defence responses specific to the encountered attacker. Here we review SA- and JA-dependent signal transduction and summarize our current understanding of the molecular mechanisms of cross-talk between these defences. [source] Reactive oxygen species and nitric oxide are involved in ABA inhibition of stomatal openingPLANT CELL & ENVIRONMENT, Issue 10 2007JIUPIANG YAN ABSTRACT Although nitric oxide (NO) and reactive oxygen species (ROS) are essential signalling molecules required for mediation of abscisic acid (ABA)-induced stomatal closure, it is not known whether these molecules also mediate the ABA inhibition of stomatal opening. In this study, we investigated the role of NO and ROS in the ABA inhibition of stomatal opening in Vicia faba. ABA induced both NO and ROS synthesis, and the NO scavenger reduced the ABA inhibition of stomatal opening. Exogenous NO and hydrogen peroxide (H2O2) also inhibited stomatal opening, indicating that NO and ROS are involved in the inhibition signalling process. An inhibitor of nitric oxide synthase (NOS) reversed the ABA inhibition of stomatal opening. Either the NO scavenger or the NOS inhibitor also reversed the process in the H2O2 inhibition of stomatal opening. We found that in the ABA inhibition of stomatal opening, NO is downstream of ROS in the signalling process, and NO is synthesized by a NOS-like enzyme. [source] Protein kinase C mRNA and protein expressions in hypobaric hypoxia-induced cardiac hypertrophy in ratsACTA PHYSIOLOGICA, Issue 4 2010M. Uenoyama Abstract Aim:, Protein kinase C (PKC), cloned as a serine/threonine kinase, plays key roles in diverse intracellular signalling processes and in cardiovascular remodelling during pressure overload or volume overload. We looked for correlations between changes in PKC isoforms (levels and/or subcellular distributions) and cardiac remodelling during experimental hypobaric hypoxic environment (HHE)-induced pulmonary hypertension. Methods:, To study the PKC system in the heart during HHE, 148 male Wistar rats were housed for up to 21 days in a chamber at the equivalent of 5500 m altitude level (10% O2). Results:, At 14 or more days of exposure to HHE, pulmonary arterial pressure (PAP) was significantly increased. In the right ventricle (RV): (1) the expression of PKC-, protein in the cytosolic and membrane fractions was increased at 3,14 days and at 5,7 days of exposure respectively; (ii) the cytosolic expression of PKC-, protein was increased at 1,5, 14 and 21 days of exposure; (3) the membrane expressions of the proteins were decreased at 14,21 (PKC-,II), 14,21 (PKC-,), and 0.5,5 and 21 (PKC-,) days of exposure; (4) the expression of the active form of PKC-, protein on the plasma membrane was increased at 3 days of exposure (based on semiquantitative analysis of the immunohistochemistry). In the left ventricle, the expressions of the PKC mRNAs, and of their cytosolic and membrane proteins, were almost unchanged. The above changes in PKC-,, which were strongly evident in the RV, occurred alongside the increase in PAP. Conclusion:, PKC-, may help to modulate the right ventricular hypertrophy caused by pulmonary hypertension in HHE. [source] Retina expresses a novel variant of the ryanodine receptorEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2007Varda Shoshan-Barmatz Abstract Calcium released from intracellular stores via the ryanodine receptor (RyR) mediates a variety of signalling processes. We previously showed that retina expresses the three known types of RyR, but retinal membrane preparations exhibit unique characteristics such as Ca2+ -independent [3H]ryanodine-binding and inhibition by caffeine. We have heretofore suggested that the major retinal RyR isoform is novel. The present study aimed to identify this receptor isoform and to localize RyR in mammalian retina. Immunoblotting with specific and pan-antibodies showed that the major retinal RyR has a mobility similar to that of RyR2 or RyR3. Real-time PCR revealed that the major type is RyR2, and RT-PCR followed by sequencing showed a transcript that encodes a protein with ~ 99% identity to RyR2, yet lacking two regions of seven and 12 amino acids and including an additional insertion of eight amino acids. An antibody against RyR2 localized this type to somas and primary dendrites of most retinal neurons. An antibody against RyR1 localized RyR to most somas but also revealed staining in photoreceptor outer segments, concentrated on the disk membranes at their rim. The ryanodine-binding properties and the electrophoretic mobility of RyR from the outer segments were similar to those of the whole retinal preparation. The results thus identify a novel variant of RyR2 which can contribute to regulating photoreceptor Ca2+ concentrations. The restricted localization of the outer segment RyR to the disk rim suggests that its activation mechanism involves a coupling between retinal RyR and the cGMP-gated channel. [source] Redox regulation of skeletal muscleIUBMB LIFE, Issue 8 2008Malcolm J. Jackson Abstract The potential deleterious roles of "oxidative stress" have been studied in skeletal muscle for over 30 years, but recent studies have identified that reactive oxygen species and nitric oxide generated by skeletal muscle can exert regulatory roles in cell signalling processes. This "redox regulation" appears to depend upon the reversible oxidation of cysteine residues within key proteins with reversible gluathionylation and formation of protein disulphides potentially leading to changes in the activities of proteins such as enzymes, transcription factors or transporters. Control of this process is dependent upon the local redox environment pertaining at a subcellular level. This short review provides examples of redox-regulated physiological processes in skeletal muscle that include some activation of transcription factors and changes in gene expression that result from contractile activity and the modulation of force generation during sustained contractions. There is also increasing evidence that dysregulation of redox-sensitive processes plays a role in the loss of muscle mass and function that occurs during normal ageing and in the gross muscle degeneration in disorders such as the muscular dystrophies. © 2008 IUBMB IUBMB Life, 60(8): 497,501, 2008 [source] Antagonistic Effects of Hydrogen Peroxide and Glutathione on Acclimation to Excess Excitation Energy in ArabidopsisIUBMB LIFE, Issue 1 2000Barbara Karpinska Abstract The redox status of the quinone B (QB) and plastoquinone (PQ) pools plays a key role in the cellular and systemic signalling processes that control acclimatory responses in plants. In this study, we demonstrate the effects of hydrogen peroxide and glutathione on acclimatory responses controlled by redox events in the proximity of the QB-PQ pools. Our results suggest that the chloroplast is a sink for H2O2 and that, paradoxically, high concentrations of H2O2 in the chloroplast protect the photosynthetic apparatus and the plant cell from photoinhibition and photooxidative damage. Excess glutathione, however, caused an effect antagonistic to that observed for high H2O2. An explanation of this apparent paradox and a hypothetical redox-signalling model are suggested. [source] Transforming growth factor-,1-regulated proteins in human endothelial cells identified by two-dimensional gel electrophoresis and mass spectrometryPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 4 2004Marta Lomnytska Abstract Transforming growth factor-, (TGF,) is a potent regulator of angiogenesis affecting proliferation, differentiation and migration of endothelial cells. The effect of TGF, on endothelial cells depends on the origin of the cells and on the experimental conditions. Global analysis of TGF, signalling is expected to unveil mechanisms of this variability and identify novel targets of the growth factor. Here, we report proteome profiling of human microvascular endothelial cells obtained from dermis, which were treated with TGF,1 and compared to nontreated cells. We identified 54 proteins affected by TGF,1 using two-dimensional gel electrophoresis and peptide mass fingerprinting. Thirteen of the identified proteins are involved in various signalling processes. Seven proteins are involved in cytoskeleton rearrangements and six are involved in regulation of metabolism. Ten proteins were identical to predicted hypothetical proteins with no assigned functions. In agreement with the effect of TGF,1 on components of the cytoskeleton, TGF,1 induces actin cytoskeleton rearrangements. TGF,1 also affected expression of E2F6, p57Kip2, G(q),, hnRNP A1 and myosin light chain proteins as shown by immunoblotting. Down-regulation of the transcriptional repressor E2F6 by TGF,1 correlated with a weak growth-inhibitory activity of TGF,1 on HMVEC-d cells. Twenty-five of the identified proteins have not previously been described as being regulated by TGF,1, providing new insights into TGF,1 signalling in endothelial cells. [source] Ca2+ -dependent components of inactivation of unitary cardiac L-type Ca2+ channelsTHE JOURNAL OF PHYSIOLOGY, Issue 1 2010Ira R. Josephson A Ca2+ ion-dependent inactivation (CDI) of L-type Ca2+ channels (LCC) is vital in limiting and shaping local Ca2+ ion signalling in a variety of excitable cell types. However, under physiological conditions the unitary LCC properties that underlie macroscopic inactivation are unclear. Towards this end, we have probed the gating kinetics of individual cardiac LCCs recorded with a physiological Ca2+ ion concentration (2 mm) permeating the channel, and in the absence of channel agonists. Upon depolarization the ensemble-averaged LCC current decayed with a fast and a slow exponential component. We analysed the unitary behaviour responsible for this biphasic decay by means of a novel kinetic dissection of LCC gating parameters. We found that inactivation was caused by a rapid decrease in the frequency of LCC reopening, and a slower decline in mean open time of the LCC. In contrast, with barium ions permeating the channel ensemble-averaged currents displayed only a single, slow exponential decay and little time dependence of the LCC open time. Our results demonstrate that the fast and slow phases of macroscopic inactivation reflect the distinct time courses for the decline in the frequency of LCC reopening and the open dwell time, both of which are modulated by Ca2+ influx. Analysis of the evolution of CDI in individual LCC episodes was employed to examine the stochastic nature of the underlying molecular switch, and revealed that influx on the order of a thousand Ca2+ ions may be sufficient to trigger CDI. This is the first study to characterize both the unitary kinetics and the stoichiometry of CDI of LCCs with a physiological Ca2+ concentration. These novel findings may provide a basis for understanding the mechanisms regulating unitary LCC gating, which is a pivotal element in the local control of Ca2+ -dependent signalling processes. [source] Intracellular function in rehydrated lyophilized plateletsBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2000Thomas H. Fischer This study aimed to evaluate the effect of cross-linking and lyophilization on intracellular signalling processes in rehydrated, lyophilized (RL) platelets, which are under development as a platelet substitute for transfusion. Exposure of RL platelets to thrombin resulted in enhanced phosphorylation of several proteins, including 18 kDa and 42 kDa kinase substrates that were shown to be the substrates of myosin light chain and protein kinase C respectively. Cross-linking and lyophilization depleted the platelets of free cytoplasmic ADP and ATP, but had less effect on protein-bound nucleotides. The surface membrane of RL platelets was found to be permeable to poly dT probes less than approximately 3 kDa in size; larger nucleotide probes and proteins did not penetrate the surface membrane. Taken together, our results indicate that RL platelets retain some of the haemostatic stimulus-response functions of fresh platelets and are capable of feedback amplification in coagulation. [source] Disrupting specific PDZ domain-mediated interactions for therapeutic benefitBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2009Miles D Houslay The past two decades have seen an immense increase in our appreciation of the vast range of signalling processes and supporting machinery that occur in cells. Pivotal to this is the notion of signal compartmentalization (compartmentation). Targeting by protein domains is critical in allowing signalling complexes to be assembled at defined intracellular locales so as to confer correct function. This issue of the BJP contains two intriguing articles that address functional protein,protein interactions involving PDZ domains [Post-synaptic density protein-95 (PSD95), Drosophila disc large tumour suppressor (DlgA) and Zonula occludens-1 protein (zo-1)] and their implications for signalling. One involves targeting of neuronal nitric oxide synthase to the N-methyl D-aspartic acid (NMDA) receptor via the PDZ-containing signal scaffold, PSD95. The other involves controlling multiple receptor inputs into regulation of epithelial Na+K+ -ATPase through the PDZ-containing signal scaffold Pals-associated tight junction. Highlighted is not only the use of dominant-negative strategies to identify the importance of targeting at specific types of PDZ domains but also the exciting notion that small molecule disruptors of interaction at specific PDZ domains can be generated for potential therapeutic application. [source] Should I stay or should I go?CELLULAR MICROBIOLOGY, Issue 8 2007Nucleocytoplasmic trafficking in plant innate immunity Summary Communication between the cytoplasm and the nucleus is a fundamental feature of eukaryotic cells. Bidirectional transport of macromolecules across the nuclear envelope is typically mediated by receptors and occurs exclusively through nuclear pore complexes (NPCs). The components and molecular mechanisms regulating nucleocytoplasmic trafficking and signalling processes are well studied in animals and yeast but are poorly understood in plants. Current work shows that components of the NPC and the nuclear import and export machinery play essential roles in plant innate immunity. Translocation of defence regulators and Resistance (R) proteins between the cytoplasm and the nucleus are recently uncovered aspects of plant defence responses against pathogens. Future studies will reveal more details on the spatial and temporal dynamics and regulation of this process. [source] Mechanisms of desmosome assembly and disassemblyCLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 8 2002Y. Kitajima Summary In skin, desmosomes constitute critical adhesion complexes between adjacent keratinocytes that help maintain an intact epidermis. However, individual keratinocytes need to migrate and differentiate and therefore desmosomes must have an inherent dynamic capacity to assemble and disassemble. This review highlights the role of the different structural junctional components involved in desmosome formation and turnover, as well as the possible signalling processes and pathways that may be implicated in desmosome homeostasis. Clues to the intricate nature of desmosome assembly and disassembly have been derived from human inherited and acquired blistering skin diseases as well as animal models and basic cell biology studies. The key implications for understanding desmosome dynamics from these findings are summarized in this review. [source] | ||||||||||||||||