Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuronal Ca2+ channels are inhibited by a variety of transmitter receptors coupled to Go-type GTP-binding proteins. Go has been postulated to work via a direct interaction between an activated G protein subunit and the Ca2+ channel complex. Here we show that the inhibition of sensory neuron N-type Ca2+ channels produced by gamma-aminobutyric acid involves a novel, rapidly activating tyrosine kinase signaling pathway that is mediated by Galphao and a src-like kinase. In contrast to other recently described G protein-coupled tyrosine kinase pathways, the Galphao-mediated modulation requires neither protein kinase C nor intracellular Ca2+. The results suggest that this pathway mediates rapid receptor-G protein signaling in the nervous system and support the existence of a previously unrecognized form of crosstalk between G protein and tyrosine kinase pathways.
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PMID:Novel form of crosstalk between G protein and tyrosine kinase pathways. 914 52

Neuronal and glial sodium-dependent transporters are crucial for the control of extracellular glutamate levels in the CNS. The regulation of these transporters is relatively unexplored, but the activity of other transporters is regulated by protein kinase C (PKC)- and phosphatidylinositol 3-kinase (PI3K)-mediated trafficking to and from the cell surface. In the present study the C6 glioma cell line was used as a model system that endogenously expresses the excitatory amino acid carrier 1 (EAAC1) subtype of neuronal glutamate transporter. As previously observed, phorbol 12-myristate 13-acetate (PMA) caused an 80% increase in transporter activity within minutes that cannot be attributed to the synthesis of new transporters. This increase in activity correlated with an increase in cell surface expression of EAAC1 as measured by using a membrane-impermeant biotinylation reagent. Both effects of PMA were blocked by the PKC inhibitor bisindolylmaleimide II (Bis II). The putative PI3K inhibitor, wortmannin, decreased L-[3H]-glutamate uptake activity by >50% within minutes. Wortmannin decreased the Vmax of L-[3H]-glutamate and D-[3H]-aspartate transport, but it did not affect Na+-dependent [3H]-glycine transport. Wortmannin also decreased cell surface expression of EAAC1. Although wortmannin did not block the effects of PMA on activity, it prevented the PMA-induced increase in cell surface expression. This trafficking of EAAC1 also was examined with immunofluorescent confocal microscopy, which supported the biotinylation studies and also revealed a clustering of EAAC1 at cell surface after treatment with PMA. These studies suggest that the trafficking of the neuronal glutamate transporter EAAC1 is regulated by two independent signaling pathways and also may suggest a novel endogenous protective mechanism to limit glutamate-induced excitotoxicity.
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PMID:Multiple signaling pathways regulate cell surface expression and activity of the excitatory amino acid carrier 1 subtype of Glu transporter in C6 glioma. 950 8

Rapid and accurate management of a patient afflicted by cerebral ischemia is crucial for the development of a successful outcome. Yet, it is the understanding of the molecular and clinical presentation of cerebrovascular disease that enables the physician to diagnose and effectively treat cerebral ischemia. Neuronal degeneration can occur at several levels in the ischemic cascade. The free radical nitric oxide (NO) has been clearly linked to ischemic neurodegeneration in both animal models and cell culture systems, but the final cellular pathways that lead from the generation of NO to eventual neuronal death require further investigation. The protective mechanisms of the peptide growth factors basic fibroblast growth factor and epidermal growth factor appear to be linked to the signal transduction pathways of NO, programmed cell death, and protein kinase C. Active modulation of metabotropic glutamate receptor activity also can prevent neuronal injury at or below the level of NO generation. The molecular mechanisms that mediate the protective effects of the metabotropic glutamate receptors are dependent on the modulation of programmed cell death. Further investigation into the molecular signal transduction pathways that are responsible for ischemic neuronal injury will foster the development of efficacious and safe treatments for cerebral ischemia.
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PMID:From the bench to the bedside: the molecular management of cerebral ischemia. 957 79

Neuronal nicotinic acetylcholine receptor (nAChR) desensitization is hypothesized to be a trigger for long-term changes in receptor number and function observed after chronic administration of nicotine at levels similar to those found in persons who use tobacco. Factors that regulate desensitization could potentially influence the outcome of long-lasting exposure to nicotine. The roles of Ca2+ and protein kinase C (PKC) on desensitization of alpha4beta2 nAChRs expressed in Xenopus laevis oocytes were investigated. Nicotine-induced (300 nM; 30 min) desensitization of alpha4beta2 receptors in the presence of Ca2+ developed in a biphasic manner with fast and slow exponential time constants of tauf = 1.4 min (65% relative amplitude) and taus = 17 min, respectively. Recovery from desensitization was reasonably well described by a single exponential with taurec = 43 min. Recovery was largely eliminated after replacement of external Ca2+ with Ba2+ and slowed by calphostin C (taurec = 48 min), an inhibitor of PKC. Conversely, the rate of recovery was enhanced by phorbol-12-myristate-13-acetate (taurec = 14 min), a PKC activator, or by cyclosporin A (with taurec = 8 min), a phosphatase inhibitor. alpha4beta2 receptors containing a mutant alpha4 subunit that lacks a consensus PKC phosphorylation site exhibited little recovery from desensitization. Based on a two-desensitized-state cyclical model, it is proposed that after prolonged nicotine treatment, alpha4beta2 nAChRs accumulate in a "deep" desensitized state, from which recovery is very slow. We suggest that PKC-dependent phosphorylation of alpha4 subunits changes the rates governing the transitions from "deep" to "shallow" desensitized conformations and effectively increases the overall rate of recovery from desensitization. Long-lasting dephosphorylation may underlie the "permanent" inactivation of alpha4beta2 receptors observed after chronic nicotine treatment.
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PMID:Regulation of alpha4beta2 nicotinic receptor desensitization by calcium and protein kinase C. 1005 26

Neuronal alpha1E subunits are thought to form R-type Ca channels. When expressed in human embryonic kidney cells with M2 muscarinic acetylcholine receptors, Ca channels encoded by rabbit alpha1E exhibit striking biphasic modulation. Receptor activation first produces rapid inhibition of current amplitude and activation rate. However, in the continued presence of agonist, alpha1E currents subsequently increase. Kinetic slowing persists during this secondary stimulation phase. After receptor deactivation, kinetic slowing is quickly relieved, and current amplitude over-recovers before returning toward control levels. These features indicate that inhibition and stimulation of alpha1E are separate processes, with stimulation superimposed on inhibition. Pertussis toxin eliminates inhibition without affecting stimulation, demonstrating that inhibition and stimulation involve distinct signaling pathways. Neither inhibition nor stimulation is altered by coexpression of Ca channel beta2a or beta3 subunits. Stimulation is abolished by staurosporine and reduced by intracellular 5'-adenylylimidodiphosphate, suggesting that phosphorylation is required. However, stimulation does not seem to involve cAMP-dependent protein kinase, protein kinase C, cGMP-dependent protein kinase, tyrosine kinases, or phosphoinositide 3-kinases. Stimulation does not require a Ca signal, because it is not specifically altered by varying intracellular Ca buffering or by substituting Ba as the charge carrier. In contrast to those formed by alpha1E, Ca channels formed by alpha1A or alpha1B display only inhibition and no stimulation during prolonged activation of M2 receptors. The dual modulation of alpha1E may confer unique physiological properties on native R-type Ca channels. As one possibility, R-type channels may continue to mediate Ca influx during steady inhibition of N-type and P/Q-type channels by muscarinic or other receptors.
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PMID:Biphasic, opposing modulation of cloned neuronal alpha1E Ca channels by distinct signaling pathways coupled to M2 muscarinic acetylcholine receptors. 1043 38

Neuronal differentiation and axonal growth are controlled by a variety of factors including neurotrophic factors, extracellular matrix components, and cell adhesion molecules. Here we describe a novel and very efficient neuritogenic factor, the metastasis-related Mts1 protein, belonging to the S100 protein family. The oligomeric but not the dimeric form of Mts1 strongly induces differentiation of cultured hippocampal neurons. A mutant with a single Y75F amino acid substitution, which stabilizes the dimeric form of Mts1, is unable to promote neurite extension. Disulfide bonds do not play an essential role in the Mts1 neuritogenic activity. Mts1-stimulated neurite outgrowth involves activation of phospholipase C and protein kinase C, depends on the intracellular level of Ca(2+), and requires activation of the extracellular signal-regulated kinases (ERKs) 1 and 2.
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PMID:Oligomeric forms of the metastasis-related Mts1 (S100A4) protein stimulate neuronal differentiation in cultures of rat hippocampal neurons. 1101 41

Neuronal process outgrowth has been postulated to be one of the fundamental steps involved in neuronal development. To test whether vasopressin can influence neuronal development by acting on the outgrowth of neuronal processes, we determined the neurotrophic action of the memory-enhancing peptide, vasopressin, in neurons derived from the cerebral cortex, a site of integrative cognitive function and long-term memory. Exposure to V(1) receptor agonist significantly increased multiple features of nerve cell morphology, including neurite length, number of branches, branch length, number of branch bifurcation points and number of microspikes. The dose-response profile of V(1) receptor agonist-induced neurotrophism exhibited a biphasic function, with lower concentrations inducing a significant increase while higher concentrations generally induced no significant effect. The neurotrophic effect of V(1) receptor activation did not require growth factors present in serum. Analysis of the regional selectivity of the vasopressin-induced neurotrophic effect revealed significant V(1) receptor agonist-induced neurotrophism in occipital and parietal neurons, whereas frontal and temporal neurons were unresponsive. Results of experiments to determine the mechanism of vasopressin-induced neurotrophism demonstrated that vasopressin-induced neurotrophism is dependent on V(1)a receptor activation, requires L-type calcium channel activation and activation of both pathways of the phosphatidylinositol signaling cascade, inositol trisphosphate and protein kinase C. These studies are the first to describe a functional cellular response for vasopressin in the cerebral cortex. The findings are discussed with respect to their implications for understanding the role of vasopressin-induced neurotrophism, the associated signaling pathways required for this response, and the ability of vasopressin to enhance memory function.
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PMID:Vasopressin-induced neurotrophism in cultured neurons of the cerebral cortex: dependency on calcium signaling and protein kinase C activity. 1106 33

Much evidence suggests that apoptosis plays a crucial role in cell population homeostasis that depends on the expression of various genes implicated in the control of cell life and death. The sensitivity of human neuroblastoma cells SK-N-SH to undergo apoptosis induced by thapsigargin was examined. SK-N-SH were previously differentiated into neuronal cells by treatments with retinoic acid (RA), 4 beta-phorbol 12-myristate 13-acetate (PMA) which increases protein kinase C (PKC) activity, and staurosporine which decreases PKC activity. Neuronal differentiation was evaluated by gamma-enolase, microtubule associated protein 2 (MAP2) and synaptophysin immunocytochemistry. The sensitivity of the cells to thapsigargin-induced apoptosis was evaluated by cell viability and nuclear fragmentation (Hoechst 33258) and compared with pro-(Bcl-2, Bcl-x(L)) and anti-apoptotic (Bax, Bak) protein expression of the Bcl-2 family. Cells treated with RA and PMA were more resistant to apoptosis than controls. Conversely, the cells treated with staurosporine were more susceptible to apoptosis. In parallel with morphological modifications, the expression of inhibitors and activators of apoptosis was directly dependent upon the differentiating agent used. Bcl-2 expression was strongly increased by PMA and drastically decreased by staurosporine as was Bcl-x(L) expression. Bax and Bak expression were not significantly modified. These results demonstrate that drugs that modulate PKC activity may induce a modification of Bcl-2 expression as well as resistance to the apoptotic process. Furthermore, the expression of Bcl-2 was reduced by toxin B from Clostridium difficile and, to a lesser extent, by wortmannin suggesting a role of small G-protein RhoA and PtdIns3 kinase in the control of Bcl-2 expression. Our data demonstrate a relationship between the continuous activation of PKC, the expression of Bcl-2 protein family and the resistance of differentiated SK-N-SH to apoptosis.
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PMID:Resistance to induced apoptosis in the human neuroblastoma cell line SK-N-SH in relation to neuronal differentiation. Role of Bcl-2 protein family. 1123 Dec 87

The present studies were undertaken to determine whether neuronal subsets in normal brains constitutively express functionally competent C5a receptors. In situ hybridization studies coupled with immunohistochemical approaches revealed that most neurons in the hippocampal formation, many pyramidal cortical neurons, and cerebellar Purkinje neurons in normal human and murine brains constitutively express C5a receptors. Neuronal C5a receptors bound C5a-coated fluorescent microspheres, and primary rodent hippocampal neurons responded to C5a with increased calcium fluxes via a pertussis-sensitive, presumably Gi-coupled protein. Additional studies with human neuroblastoma cells conducted to address the functional role of C5a receptors revealed that C5a triggered rapid activation of protein kinase C and activation and nuclear translocation of the NF-kappa B transcription factor. In addition, C5a was found to be mitogenic for undifferentiated human neuroblastoma cells, a novel action for the C5aR. In contrast, C5a protected terminally differentiated human neuroblastoma cells from toxicity mediated by the amyloid A beta peptide. Thus, normal rodent hippocampal neurons as well as undifferentiated and differentiated human neuroblastoma cells express functional C5a receptors. These results have implications for understanding the role of neuronal C5aR receptors in normal neuronal development, neuronal homeostasis, and neuroinflammatory conditions such as Alzheimer's disease.
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PMID:Neuronal expression of a functional receptor for the C5a complement activation fragment. 1123 66

In the past several years there has been significant progress made on the biophysics of neurotransmitter transporters, leading to the proposal of new models of substrate and ion permeation across membranes. Questions arising from these studies are as follows: How are substrate uptake and substrate-induced current related? Where and how does substrate-ion coupling occur? What is the functional significance of the coupled and uncoupled currents? Because of a long-standing interest and collaboration, and because of their importance for normal function and disease, the authors have focused on the properties of human norepinephrine and serotonin transporters, using other clones and mutations as specific needs arise. It has been know for decades that hNETs (human norepinephrine transporters) clear NE+ (norepinephrine) following its release in peripheral sympathetic and central noradrenergic synapses. Neuronal activity influences NE+ uptake, so one is also interested in the acute regulation of hNET. To study these problems, hNET-expressing cells have been developed that are suitable for patch clamp, radioligand uptake, biochemistry, and transiently expressed clones for structure-function analysis, and new protocols have been designed combining patch-clamp, microamperometry, Ca2+ imaging, and native catecholamine transporter preparations to study transporters in whole cells and isolated patches. Using these methods, Na-dependent, NE+-induced hNET currents that are blocked by cocaine and antidepressants, channel modes of NE+ conduction, voltage-dependent uptake coupled to NE+-induced ion channel activity, PKC (phosphokinase C) regulation of NE+ uptake, and transporter modulation by [Ca2+]i have all been discovered. There is also provocative new data on other transporters in this family, such as Li/Na mole fraction experiments in the Drosophila serotonin transporters and sided enkephalin block in proline transporters. These studies have led one to postulate the existence of a narrow pore within transporters through which the substrate (NE+ or serotonin, 5HT+) and other ions (principally Na+) pass. It is hypothesized that the pore resides in an oligomeric structure and that separate gene products of hNET or hSERT (human serotonin transporters) come together to form a channel.
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PMID:Serotonin and norepinephrine transporters: possible relationship between oligomeric structure and channel modes of conduction. 1139 11


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