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Ca2+ Signaling (ca2+ + signaling)
Terms modified by Ca2+ Signaling Selected AbstractsLysophosphatidic Acid Inhibits Ca2+ Signaling in Response to Epidermal Growth Factor Receptor Stimulation in Human Astrocytoma Cells by a Mechanism Involving Phospholipase C, and a G,i ProteinJOURNAL OF NEUROCHEMISTRY, Issue 4 2000Marita Hernández Abstract: The effect of the lysophospholipid mediators lysophosphatidic acid (LPA) and sphingosine 1-phosphate and the polypeptide growth factor epidermal growth factor (EGF) on the human astrocytoma cell line 1321N1 was assessed. These agonists produced a rapid and transient increase of the intracellular Ca2+ concentration. When LPA was perfused before addition of EGF, the EGF-dependent Ca2+ transient was abrogated, whereas this was not observed when EGF preceded LPA addition. This inhibitory effect was not found for other EGF-mediated responses, e.g., activation of the mitogen-activated protein kinase cascade and cell proliferation, thus pointing to the existence of cross-talk between LPA and EGF for only a branch of EGF-induced responses. As 1321N1 cells expressed mRNA encoding the LPA receptors endothelial differentiation gene (Edg)-2, Edg-4, and Edg-7 and as sphingosine 1-phosphate did not interfere with LPA signaling, Edg-2, Edg-4, and/or Edg-7 could be considered as the LPA receptors mediating the aforementioned cross-talk. Attempts to address the biochemical mechanism involved in the cross-talk between the receptors were conducted by the immunoprecipitation approach using antibodies reacting with the EGF receptor (EGFR), phosphotyrosine, phospholipase C, (PLC,)-1, and G,i protein. LPA was found to induce coupling of PLC,-1 to the EGFR by a mechanism involving a G,i protein, in the absence of tyrosine phosphorylation of both PLC, and the EGFR. These data show a cross-talk between LPA and EGF limited to a branch of EGFR-mediated signaling, which may be explained by a LPA-induced, G,i -protein-mediated translocation of PLC,-1 to EGFR in the absence of detectable tyrosine phosphorylation of both proteins. [source] Functional Expression, Targeting and Ca2+ Signaling of a Mouse Melanopsin-eYFP Fusion Protein in a Retinal Pigment Epithelium Cell Line,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Maikel E. Giesbers Melanopsin, first discovered in Xenopus melanophores, is now established as a functional sensory photopigment of the intrinsically photosensitive retinal ganglion cells. These ganglion cells drive circadian rhythm and pupillary adjustments through projection to the brain. Melanopsin shares structural similarities with all known opsins. Comprehensive characterization of melanopsin with respect to its spectral properties, photochemical cascade and signaling partners requires a suitable recombinant system and high expression levels. This combination has not yet been described. To address this issue, we have expressed recombinant mouse melanopsin in several cell lines. Using enhanced yellow fluorescent protein (eYFP) as a visualization tag, expression was observed in all cell lines. Confocal microscopy revealed that melanopsin was properly routed to the plasma membrane only in retinal pigment epithelium (RPE)-derived D407 cells and in human embryonic kidney (HEK) cells. Further, we performed intracellular calcium measurements in order to probe the melanopsin signaling activity of this fusion protein. Transfected cells were loaded with the calcium indicator Fura2-AM. Upon illumination, an immediate but transient calcium response was observed in HEK as well as in D407 cells, while mock-transfected cells showed no calcium response under identical conditions. Supplementation with 11- cis retinal or all- trans retinal enhanced the response. After prolonged illumination the cells became desensitized. Thus, RPE-derived cells expressing recombinant melanopsin may constitute a suitable system for the study of the structural and functional characteristics of melanopsin. [source] Homocysteine enhances cardiac neural crest cell attachment in vitro by increasing intracellular calcium levelsDEVELOPMENTAL DYNAMICS, Issue 8 2008David J. Heidenreich Abstract Elevated homocysteine (Hcys) increases the risk of neurocristopathies. Previous studies show Hcys inhibits neural crest (NC) cell migration in vivo. However, the mechanisms responsible for this effect are unknown. Here, we evaluated the effect of Hcys on NC cell attachment in vitro and determined if any of the effects were due to altered Ca2+ signaling. We found Hcys enhanced NC cell attachment in a dose and substrate-dependent manner. Ionomycin mimicked the effect of Hcys while BAPTA-AM and 2-APB blocked the effect of Hcys on NC attachment. In contrast, inhibitors of plasma membrane Ca2+ channels had no effect on NC attachment. Hcys also increased the emission of the intracellular Ca2+ -sensitive probe, Fluo-4. These results show Hcys alters NC attachment by triggering an increase in intracellular Ca2+ possibly by generating inositol triphosphate. Hence, the teratogenic effect ascribed to Hcys may be due to perturbation of intracellular Ca2+ signaling. Developmental Dynamics 237:2117,2128, 2008. © 2008 Wiley-Liss, Inc. [source] Pharmacological characterization of the rat brain P2Y1 receptor expressed in HEK293 cells: Ca2+ signaling and receptor regulationDRUG DEVELOPMENT RESEARCH, Issue 2-3 2001Christian Vöhringer Abstract The increasing number of ATP- and UTP-sensitive membrane receptors identified by cloning represent either ligand-activated ion channels (P2X) or G-protein-coupled receptors (P2Y). Adenosine, ATP, and UTP have potential application in the management of pain, cancer, and some cardiovascular and pulmonary diseases and are also involved in inflammatory processes in the brain. Therefore, P2Y receptors seem to be promising therapeutic targets. Multiple P2Y receptor subtypes, classified pharmacologically, are mainly linked to activation of phospholipase C (PLC). The present study further characterizes the rat brain P2Y1 wild-type receptor (rP2Y1 -wt) and the eGFP-tagged receptor (rP2Y1 -eGFP) stably expressed in HEK293 cells, thus shedding light on receptor regulation. Both receptors were analyzed by measuring Ca2+ responses in single cells. The rP2Y1 -eGFP receptor was coupled to Ca2+ release like the rP2Y1 -wt receptor. Experiments using the PLC inhibitor U73122 confirm the functional activation of PLC, through rP2Y1 -eGFP activation. The P2Y1 -selective agonists 2-MeSADP and 2-MeSATP were most potent at the heterologously expressed receptors. We found a ligand selectivity typical for P2Y1 receptors (2-MeSADP = 2-MeSATP > ADP > ATP,S, ATP >> UTP). Fluorescence microscopy and Ca2+ measurements confirm that the rP2Y1-eGFP receptor during homologous desensitization is subjected to processes leading to agonist-induced internalization. The kinetics of receptor resensitization were also examined. Therefore, rP2Y1 -eGFP expressing cells are suitable to determine the physiological P2Y1 receptor signaling pathway and can be a helpful tool to identify drugs acting at P2Y1 receptors as possible therapeutic targets. Drug Dev. Res. 53:172,179, 2001. © 2001 Wiley-Liss, Inc. [source] Axon-glia communication evokes calcium signaling in olfactory ensheathing cells of the developing olfactory bulbGLIA, Issue 4 2007Anne Rieger Abstract Olfactory ensheathing cells (OECs) accompany receptor axons in the olfactory nerve and promote axonal growth into the central nervous system. The mechanisms underlying the communication between axons and OECs, however, have not been studied in detail yet. We investigated the effect of activity-dependent neuronal transmitter release on Ca2+ signaling of OECs in acute mouse olfactory bulb slices using confocal Ca2+ imaging. TTX-sensitive axonal activity upon electrical nerve stimulation triggers a rise in cytosolic Ca2+ in OECs, which can be mimicked by application of DHPG, an agonist of metabotropic glutamate receptors (mGluRs). Both stimulation- and DHPG-induced Ca2+ transients in OECs were abolished by depletion of intracellular Ca2+ stores with cyclopiazonic acid (CPA). The mGluR1 -specific antagonist CPCCOEt completely inhibited DHPG-evoked Ca2+ transients, but reduced stimulation-induced Ca2+ transients only partly, suggesting the involvement of another neurotransmitter. Application of ATP evoked CPA-sensitive Ca2+ transients in OECs, which were inhibited by the P2Y1 -specific antagonist MRS2179. Co-application of CPCCOEt and MRS2179 almost completely blocked the stimulation-induced Ca2+ transients, indicating that they were mediated by mGluR1 and P2Y1 receptors. Our results show that OECs are able to respond to olfactory nerve activity with an increase in cytosolic Ca2+ due to glutamate and ATP release. © 2006 Wiley-Liss, Inc. [source] Changes in the expression of plasma membrane calcium extrusion systems during the maturation of hippocampal neuronsHIPPOCAMPUS, Issue 1 2006Sertac N. Kip Abstract Spatial and temporal control of intracellular calcium signaling is essential for neuronal development and function. The termination of local Ca2+ signaling and the maintenance of basal Ca2+ levels require specific extrusion systems in the plasma membrane. In rat hippocampal neurons (HNs) developing in vitro, transcripts for all isoforms of the plasma membrane Ca2+ pump and the Na/Ca2+ exchanger, and the major nonphotoreceptor Na+/Ca2+,K+ exchangers (NCKX) were strongly upregulated during the second week in culture. Upregulation of plasma membrane calcium ATPases (PMCAs)1, 3, and 4 mRNA coincided with a splice shift from the ubiquitous b-type to the neuron-specific a-type with altered calmodulin regulation. Expression of all PMCA isoforms increased over 5-fold during the first 2 weeks. PMCA immunoreactivity was initially concentrated in the soma and growth cones of developing HNs. As the cells matured, PMCAs concentrated in the dendritic membrane and often colocalized with actin-rich dendritic spines in mature neurons. In the developing rat hippocampal CA1 region, immunohistochemistry confirmed the upregulation of all PMCAs and showed that by the end of the second postnatal week, PMCAs1, 2, and 3 were concentrated in the neuropil, with less intense staining of cell bodies in the pyramidal layer. PMCA4 staining was restricted to a few cells showing intense labeling of the cell periphery and neurites. These results establish that all major Ca2+ extrusion systems are strongly upregulated in HNs during the first 2 weeks of postnatal development. The overall increase in Ca2+ extrusion systems is accompanied by changes in the expression and cellular localization of different isoforms of the Ca2+ pumps and exchangers. The accumulation of PMCAs in dendrites and dendritic spines coincides with the functional maturation in these neurons, suggesting the importance of the proper spatial organization of Ca2+ extrusion systems for synaptic function and development. © 2005 Wiley-Liss, Inc. [source] Calcium ions in neuronal degenerationIUBMB LIFE, Issue 9 2008Urszula Wojda Abstract Neuronal Ca2+ homeostasis and Ca2+ signaling regulate multiple neuronal functions, including synaptic transmission, plasticity, and cell survival. Therefore disturbances in Ca2+ homeostasis can affect the well-being of the neuron in different ways and to various degrees. Ca2+ homeostasis undergoes subtle dysregulation in the physiological ageing. Products of energy metabolism accumulating with age together with oxidative stress gradually impair Ca2+ homeostasis, making neurons more vulnerable to additional stress which, in turn, can lead to neuronal degeneration. Neurodegenerative diseases related to aging, such as Alzheimer's disease, Parkinson's disease, or Huntington's disease, develop slowly and are characterized by the positive feedback between Ca2+ dyshomeostasis and the aggregation of disease-related proteins such as amyloid beta, alfa-synuclein, or huntingtin. Ca2+ dyshomeostasis escalates with time eventually leading to neuronal loss. Ca2+ dyshomeostasis in these chronic pathologies comprises mitochondrial and endoplasmic reticulum dysfunction, Ca2+ buffering impairment, glutamate excitotoxicity and alterations in Ca2+ entry routes into neurons. Similar changes have been described in a group of multifactorial diseases not related to ageing, such as epilepsy, schizophrenia, amyotrophic lateral sclerosis, or glaucoma. Dysregulation of Ca2+ homeostasis caused by HIV infection or by sudden accidents, such as brain stroke or traumatic brain injury, leads to rapid neuronal death. The differences between the distinct types of Ca2+ dyshomeostasis underlying neuronal degeneration in various types of pathologies are not clear. Questions that should be addressed concern the sequence of pathogenic events in an affected neuron and the pattern of progressive degeneration in the brain itself. Moreover, elucidation of the selective vulnerability of various types of neurons affected in the diseases described here will require identification of differences in the types of Ca2+ homeostasis and signaling among these neurons. This information will be required for improved targeting of Ca2+ homeostasis and signaling components in future therapeutic strategies, since no effective treatment is currently available to prevent neuronal degeneration in any of the pathologies described here. © 2008 IUBMB IUBMB Life, 60(9): 575,590, 2008 [source] A Role for G Protein-Coupled Lysophospholipid Receptors in Sphingolipid-Induced Ca2+ Signaling in MC3T3-E1 Osteoblastic CellsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2001Jeremy M. Lyons Abstract Sphingolipids have been proposed to modulate cell function by acting as intracellular second messengers and through binding to plasma membrane receptors. Exposure of MC3T3-E1 osteoblastic cells to sphingosine (SPH), sphingosine-1-phosphate (SPP), or sphingosylphosphorylcholine (SPC) led to the release of Ca2+ from the endoplasmic reticulum (ER) and acute elevations in cytosolic-free Ca2+ ([Ca2+]i). Desensitization studies suggest that SPP and SPC bind plasma membrane endothelial differentiation gene (Edg) receptors for lysophosphatidic acid (LPA). Consistent with the coupling of Edg receptors to G proteins, SPP- and SPC-induced Ca2+ signaling was inhibited by pretreatment of the cells with pertussis toxin (PTx). Of the Edg receptors known to bind SPH derivatives in other cell types, MC3T3-E1 cells were found to express transcripts encoding Edg -1 and Edg -5 but not Edg -3, Edg -6, or Edg -8. In contrast to SPP and SPC, the ability of SPH to elicit [Ca2+]i elevations was affected neither by prior exposure of cells to LPA nor by PTx treatment. However, LPA-induced Ca2+ signaling was blocked in MC3T3-E1 cells previously exposed to SPH. Elevations in [Ca2+]i were not evoked by SPP or SPC in cells treated with 2-aminoethoxydiphenylborate (2-APB), an inhibitor of inositol 1,4,5-trisphosphate (IP3)-gated Ca2+ channels in the ER. No effect of 2-APB was observed on SPH- or LPA-induced [Ca2+]i elevations. The data support a model in which SPP and SPC bind Edg -1 and/or Edg -5 receptors in osteoblasts leading to the release of Ca2+ from the ER through IP3 -gated channels. [source] Dual Mechanism of Intercellular Communication in HOBIT Osteoblastic Cells: A Role for Gap-Junctional HemichannelsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2001Milena Romanello Abstract Intercellular communication allows tissue coordination of cell metabolism and sensitivity to extracellular stimuli. Paracrine stimulation and cell-to-cell coupling through gap junctions induce the formation of complex cellular networks, which favors the intercellular exchange of nutrients and second messengers. Intercellular Ca2+ signaling was investigated in human osteoblast-like initial transfectant (HOBIT) cells, a human osteoblastic cell line in which cells retain most of the osteoblastic differentiation markers. HOBIT cells express connexin43 (Cx43) clustered at the cell-to-cell boundary and display functional intercellular coupling as assessed by the intercellular transfer of Lucifer yellow. Mechanical stimulation of a single cell induced a wave of increased Ca2+ that was radially propagated to surrounding cells. Treatment of cells with thapsigargin blocked mechanically induced signal propagation. Intercellular Ca2+ spreading and dye transfer were inhibited by 18,-glycyrrhetinic acid (18-GA), showing the involvement of gap junctions in signal propagation. Pretreatment of cells with suramin or with apyrase decreased the extent of wave propagation, suggesting that ATP-mediated paracrine stimulation contribute to cell-to-cell signaling. The functional expression of gap-junctional hemichannels was evidenced in experiments of Mn2+ quenching, extracellular dye uptake, and intracellular Ca2+ release, activated by uptake of inositol 1,4,5-trisphosphate (InsP3) from the external medium. Gap-junctional hemichannels were activated by low extracellular Ca2+ concentrations and inhibited by 18-GA. A role for Cx hemichannels in adenosine triphosphate (ATP) release and paracrine stimulation is suggested. [source] Mitochondria and Ca2+ signalingJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2000Emil C. Toescu Abstract Mitochondria play a central role in cell homeostasis. Amongst others, one of the important functions of mitochondria is to integrate its metabolic response with one of the major signaling pathways - the Ca2+ signaling. Mitochondria are capable to sense the levels of cytosolic Ca2+ and generate mitochondrial Ca2+ responses. Specific mechanisms for both Ca2+ uptake and Ca2+ release exist in the mitochondrial membranes. In turn, the mitochondrial Ca2+ signals are able to produce changes in the mitochondrial function and metabolism, which provide the required level of functional integration. This essay reviews briefly the current available information regarding the mitochondrial Ca2+ transport systems and some of the functional consequences of mitochondrial Ca2+ uptake [source] CREB-dependent cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression is mediated by protein kinase C and calciumJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2006Hung Pham Abstract Cellular production of prostaglandins (PGs) is controlled by the concerted actions of cyclooxygenases (COX) and terminal PG synthases on arachidonic acid in response to agonist stimulation. Recently, we showed in an ileal epithelial cell line (IEC-18), angiotensin II-induced COX-2-dependent PGI2 production through p38MAPK, and calcium mobilization (J. Biol. Chem. 280: 1582,1593, 2005). Agonist binding to the AT1 receptor results in activation of PKC activity and Ca2+ signaling but it is unclear how each pathway contributes to PG production. IEC-18 cells were stimulated with either phorbol-12,13-dibutyrate (PDB), thapsigargin (TG), or in combination. The PG production and COX-2 and PG synthase expression were measured. Surprisingly, PDB and TG produced PGE2 but not PGI2. This corresponded to induction of COX-2 and mPGES-1 mRNA and protein. PGIS mRNA and protein levels did not change. Activation of PKC by PDB resulted in the activation of ERK1/2, JNK, and CREB whereas activation of Ca2+ signaling by TG resulted in the delayed activation of ERK1/2. The combined effect of PKC and Ca2+ signaling were prolonged COX-2 and mPGES-1 mRNA and protein expression. Inhibition of PKC activity, MEK activity, or Ca2+ signaling blocked agonist induction of COX-2 and mPGES-1. Expression of a dominant negative CREB (S133A) blocked PDB/TG-dependent induction of both COX-2 and mPGES-1 promoters. Decreased CREB expression by siRNA blocked PDB/TG-dependent expression of COX-2 and mPGES-1 mRNA. These findings demonstrate a coordinated induction of COX-2 and mPGES-1 by PDB/TG that proceeds through PKC/ERK and Ca2+ signaling cascades, resulting in increased PGE2 production. J. Cell. Biochem. © 2006 Wiley-Liss, Inc. [source] Role of endogenous regucalcin in transgenic rats: Suppression of kidney cortex cytosolic protein phosphatase activity and enhancement of heart muscle microsomal Ca2+ -ATPase activityJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2002Masayoshi Yamaguchi Abstract Rats were generated by pronuclear injection of the transgene with a cDNA construct encoding rat regucalcin that is a regulatory protein of Ca2+ signaling. Transgenic (TG) founders were fertile, transmitted the transgene at the expected frequency, and bred to homozygote. Western analysis of the cytosol prepared from the tissue of TG female rats (5-week-old) showed a remarkable expression of regucalcin (3.3 kDa) protein in the liver, kidney cortex, heart, lung, stomach, brain, spleen, muscle, colon, and duodenum. Regucalcin expression of TG male rats was seen in the liver, kidney cortex, heart, and lung. In wild-type (wt) male and female rats, regucalcin was mainly present in the liver and kidney cortex. Regucalcin inhibited protein phosphatase activity in rat kidney cortex cytosol and activated Ca2+ -ATPase activity in rat heart muscle microsomes. The suppressive effect of regucalcin on protein phosphatase activity was significantly enhanced in the cytosol of kidney cortex of TG male and female rats as compared with those of wt rats. Likewise, heart muscle microsomal Ca2+ -ATPase activity was significantly enhanced in TG rats. The changes in their enzyme's activities in TG rats were completely abolished in the presence of anti-regucalcin monoclonal antibody (100 ng/ml) in the enzyme reaction mixture. Moreover, the body weight of TG female rats was significantly lowered as compared with that of wt rats. Serum inorganic phosphorus concentration was significantly increased in TG male and female rats, while serum calcium, glucose, triglyceride, free cholesterol, albumin, and urea nitrogen concentrations were not significantly altered in TG rats. Regucalcin TG rats should be a useful model to define a regulatory role of endogenous regucalcin in the tissues in vivo. J. Cell. Biochem. 86: 520,529, 2002. © 2002 Wiley-Liss, Inc. [source] Role of LOX-1 in monocyte adhesion-triggered redox, Akt/eNOS and Ca2+ signaling pathways in endothelial cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2009Nobuo Sakamoto This study was conducted to examine the role of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in monocyte adhesion-induced redox-sensitive, Akt/eNOS and Ca2+ signaling pathways in endothelial cells (ECs). LOX-1 was blocked by an antibody-neutralizing LOX-1 TS92 or small interfering RNA. In cultured human aortic ECs, monocyte adhesion activated Rac1 and p47phox, and increased NADPH oxidase activity and reactive oxygen species (ROS) generation within 30,min and NF-,B phosphorylation within 1,h, resulting in redox-sensitive gene expression. Akt and eNOS phosphorylation was induced 15,min after adding monocytes and returned to control level after 30,min, whereas NO production was not altered by monocyte adhesion. Blockade of LOX-1 blunted the monocyte adhesion-triggered redox-sensitive signaling pathway and Akt/eNOS phosphorylation in ECs. Both endothelial intracellular Ca2+ mobilization and Ca2+ influx caused by monocyte attachment were markedly attenuated by pretreatment of ECs with TS92. This suggests that LOX-1 is involved in redox-sensitive, Akt/eNOS and Ca2+ signaling pathways in monocyte adhesion to ECs independent of oxidized low-density lipoprotein (ox-LDL). Furthermore, blockade of Ca2+ inhibited monocyte adhesion-triggered Rac1 and p47phox activation and ROS generation in ECs, whereas Ca2+ signaling was suppressed by blockade of NADPH oxidase and ROS generation. Finally, TS92 blocked the monocyte adhesion to ECs stimulated with or without tumor necrosis factor-, or ox-LDL. We provide evidence that LOX-1 plays a role in redox-sensitive, Akt/eNOS and Ca2+ signaling pathways in monocyte adhesion to ECs independent of the ox-LDL,LOX-1 axis. J. Cell. Physiol. 220: 706,715, 2009. © 2009 Wiley-Liss, Inc. [source] Cyclic ADP-ribose as a potential second messenger for neuronal Ca2+ signalingJOURNAL OF NEUROCHEMISTRY, Issue 2 2001Haruhiro Higashida Cyclic ADP-ribose (cADPR), a known endogenous modulator of ryanodine receptor Ca2+ releasing channels, is found in the nervous system. Injection of cADPR into neuronal cells primarily induces a transient elevation of intracellular Ca2+ concentration ([Ca2+]i), and/or secondarily potentiates [Ca2+]i increases that are the result of depolarization-induced Ca2+ influx. Acetylcholine release from cholinergic neurons is facilitated by cADPR. cADPR modifies K+ currents or elicits Ca2+ -dependent inward currents. cADPR is synthesized by both membrane-bound and cytosolic forms of ADP-ribosyl cyclase in neuronal cells. cADPR hydrolase activity is weak in the membrane fraction, but high in the cytoplasm. Cytosolic ADP-ribosyl cyclase activity is upregulated by nitric oxide/cyclic GMP-dependent phosphorylation. Stimulation of muscarinic and ,-adrenergic receptors activates membrane-bound ADP-ribosyl cyclase via G proteins within membranes of neuronal tumor cells and cortical astrocytes. These findings strongly suggest that cADPR is a second messenger in Ca2+ signaling in the nervous system, although many intriguing issues remain to be addressed before this identity is confirmed. [source] Neural Stem Cells and AlcoholALCOHOLISM, Issue 2 2003F. T. Crews This article summarizes the proceedings of a symposium held at the 2002 Research Society on Alcoholism Meeting in San Francisco, California. The aim of this symposium was to review research on the effects of ethanol on neural stems cells and neurogenesis. Ethanol is known to alter neurogenesis during development; however, recent studies indicate that the brain forms new neurons from stem cells throughout life. Furthermore, stem cells can be transplanted into the brain, creating exciting new possibilities to study brain function. The symposium covered these research areas. Dr. Michael W. Miller reviewed knowledge on the effects of ethanol on stem cell proliferation and differentiation during development. Dr. Wu Ma described studies in culture indicating that (1) neural stem cells express functional muscarinic acetylcholine receptors (mAchR), (2) mAchR-mediated proliferation involves Ca2+ signaling and mitogen-activated protein kinase phosphorylation, and (3) phosphoinositol-3 kinase is a downstream effector for mAchR-mediated cell proliferation via activation of Akt. Drs. Kim Nixon and Fulton T. Crews followed with in vivo studies on ethanol's effects on adult neural stem cell proliferation and differentiation. Dr. W. Michael Zawada described studies directed at dopamine neuron cell transplants into mammalian central nervous system. These studies clearly establish that ethanol has significant effects on stem cells. [source] Functional characterization of TRPV4 as an osmotically sensitive ion channel in porcine articular chondrocytesARTHRITIS & RHEUMATISM, Issue 10 2009Mimi N. Phan Objective Transient receptor potential vanilloid 4 (TRPV4) is a Ca2+ -permeable channel that can be gated by tonicity (osmolarity) and mechanical stimuli. Chondrocytes, the cells in cartilage, respond to their osmotic and mechanical environments; however, the molecular basis of this signal transduction is not fully understood. This study was undertaken to demonstrate the presence and functionality of TRPV4 in chondrocytes. Methods TRPV4 protein expression was measured by immunolabeling and Western blotting. In response to TRPV4 agonist/antagonists, osmotic stress, and interleukin-1 (IL-1), changes in Ca2+ signaling, cell volume, and prostaglandin E2 (PGE2) production were measured in porcine chondrocytes using fluorescence microscopy, light microscopy, or immunoassay, respectively. Results TRPV4 was expressed abundantly at the RNA and protein levels. Exposure to 4,-phorbol 12,13-didecanoate (4,PDD), a TRPV4 activator, caused Ca2+ signaling in chondrocytes, which was blocked by the selective TRPV4 antagonist, GSK205. Blocking TRPV4 diminished the chondrocytes' response to hypo-osmotic stress, reducing the fraction of Ca2+ responsive cells, the regulatory volume decrease, and PGE2 production. Ca2+ signaling was inhibited by removal of extracellular Ca2+ or depletion of intracellular stores. Specific activation of TRPV4 restored the defective regulatory volume decrease caused by IL-1. Chemical disruption of the primary cilium eliminated Ca2+ signaling in response to either 4,PDD or hypo-osmotic stress. Conclusion Our findings indicate that TRPV4 is present in articular chondrocytes, and chondrocyte response to hypo-osmotic stress is mediated by this channel, which involves both an extracellular Ca2+ and intracellular Ca2+ release. TRPV4 may also be involved in modulating the production or influence of proinflammatory molecules in response to osmotic stress. [source] Role of mitochondrial ion channels in cell deathBIOFACTORS, Issue 4 2010Shin-Young Ryu Abstract Ion channels located in the outer and inner mitochondrial membranes are key regulators of cellular signaling for life and death. Permeabilization of mitochondrial membranes is one of the most critical steps in the progression of several cell death pathways. The mitochondrial apoptosis-induced channel (MAC) and the mitochondrial permeability transition pore (mPTP) play major roles in these processes. Here, the most recent progress and current perspectives about the roles of MAC and mPTP in mitochondrial membrane permeabilization during cell death are presented. The crosstalk signaling of MAC and mPTP formation/activation mediated by cytosolic Ca2+ signaling, Bcl-2 family proteins, and other mitochondrial ion channels is also discussed. Understanding the mechanisms that regulate opening and closing of MAC and mPTP has revealed new therapeutic targets that potentially could control cell death in pathologies such as cancer, ischemia/reperfusion injuries, and neurodegenerative diseases. [source] Dynamical analysis of the calcium signaling pathway in cardiac myocytes based on logarithmic sensitivity analysisBIOTECHNOLOGY JOURNAL, Issue 5 2008Tae-Hwan Kim Abstract Many cellular functions are regulated by the Ca2+ signal which contains specific information in the form of frequency, amplitude, and duration of the oscillatory dynamics. Any alterations or dysfunctions of components in the calcium signaling pathway of cardiac myocytes may lead to a diverse range of cardiac diseases including hypertrophy and heart failure. In this study, we have investigated the hidden dynamics of the intracellular Ca2+ signaling and the functional roles of its regulatory mechanism through in silico simulations and parameter sensitivity analysis based on an experimentally verified mathematical model. It was revealed that the Ca2+ dynamics of cardiac myocytes are determined by the balance among various system parameters. Moreover, it was found through the parameter sensitivity analysis that the self-oscillatory Ca2+ dynamics are most sensitive to the Ca2+ leakage rate of the sarcolemmal membrane and the maximum rate of NCX, suggesting that these two components have dominant effects on circulating the cytosolic Ca2+. [source] | ||||||||||||||||||||||||||||