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

To investigate the possible role of members of the mammalian transient receptor potential (TRP) channel family (TRPC1-7) in vasoconstrictor-induced Ca(2+) entry in vascular smooth muscle cells, we studied [Arg(8)]-vasopressin (AVP)-activated channels in A7r5 aortic smooth muscle cells. AVP induced an increase in free cytosolic Ca(2+) concentration ([Ca(2+)](i)) consisting of Ca(2+) release and Ca(2+) influx. Whole cell recordings revealed the activation of a nonselective cation current with a doubly rectifying current-voltage relation strikingly similar to those described for some heterologously expressed TRPC isoforms. The current was also stimulated by direct activation of G proteins as well as by activation of the phospholipase Cgamma-coupled platelet-derived growth factor receptor. Currents were not activated by store depletion or increased [Ca(2+)](i). Application of 1-oleoyl-2-acetyl-sn-glycerol stimulated the current independently of protein kinase C, a characteristic property of the TRPC3/6/7 subfamily. Like TRPC6-mediated currents, cation currents in A7r5 cells were increased by flufenamate. Northern hybridization revealed mRNA coding for TRPC1 and TRPC6. We therefore suggest that TRPC6 is a molecular component of receptor-stimulated Ca(2+)-permeable cation channels in A7r5 smooth muscle cells.
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PMID:TRPC6 is a candidate channel involved in receptor-stimulated cation currents in A7r5 smooth muscle cells. 1178 46

Store-operated Ca(++) entry (SOCE) is thought to comprise the major pathway for Ca(++) entry in platelets. Recently, a number of transient receptor potential (TRP) proteins, which have been divided into 3 groups (TRPC, TRPM, and TRPV), have been suggested as SOCE channels. We report the expression and function of TRPC proteins in human platelets. TRPC6 is found at high levels and TRPC1 at low levels. Using purified plasma (PM) and intracellular membranes (IM), TRPC6 is found in the PM, but TRPC1 is localized to the IM. Using Fura-2-loaded platelets, we report that, in line with TRPC6 expression, 1-oleoyl-2-acetyl-sn-glycerol (OAG) stimulated the entry of Ca(++) and Ba(2+) independently of protein kinase C. Thrombin also induced the entry of Ca(++) and Ba(2+), but thapsigargin, which depletes the stores, induced the entry of only Ca(++). Thus, thrombin activated TRPC6 via a SOCE-independent mechanism. In phosphorylation studies, we report that neither TRPC6 nor TRPC1 was a substrate for tyrosine kinases. TRPC6 was phosphorylated by cAMP-dependent protein kinase (cAMP-PK) and associated with other cAMP-PK substrates. TRPC1 was not phosphorylated by cAMP-PK but also associated with other substrates. Activation of cAMP-PK inhibited Ca(++) but not Ba(2+) entry induced by thrombin and neither Ca(++) nor Ba(2+) entry stimulated by OAG. These results suggest that TRPC6 is a SOCE-independent, nonselective cation entry channel stimulated by thrombin and OAG. TRPC6 is a substrate for cAMP-PK, although phosphorylation appears to not affect cation permeation. TRPC1 is located in IM, suggesting a role at the level of the stores.
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PMID:Expression and role of TRPC proteins in human platelets: evidence that TRPC6 forms the store-independent calcium entry channel. 1243 1

The vascular endothelial cell forms a semipermeable barrier between blood and interstitium. Inflammatory mediators such as thrombin and histamine induce vascular leakage defined as increased endothelial permeability to plasma proteins and other solutes. Increased endothelial permeability is the hallmark of inflammatory vascular edema. Inflammatory mediators that bind to heptahelical G protein-coupled receptors (GPCR) trigger increased endothelial permeability by increasing the intracellular Ca(2+) concentration ([Ca(2+)](i)). The rise in [Ca(2+)](i) activates key signaling pathways, which mediate cytoskeletal reorganization (through myosin light chain (MLC)-dependent contraction) and disassembly of VE-cadherin at the adherens junctions. The Ca(2+)-dependent protein kinase C (PKC) isoform, PKC-alpha, plays a critical role in initiating endothelial cell contraction and disassembly of VE-cadherin junctions. The increase in [Ca(2+)](i) induced by a variety of agonists is achieved by the generation of inositol 1,4,5-trisphosphate (IP3), activation of IP3 receptors (IP3R), release of stored intracellular Ca(2+), and Ca(2+) entry through plasma membrane channels. Recent findings demonstrate that IP3-sensitive Ca(2+) store depletion activates plasma membrane cation channels (i.e., store-operated cation channels (SOC) or Ca(2+) release activated channels) to cause Ca(2+) influx in endothelial cells. This mode of Ca(2+) influx is also known as capacitative Ca(2+) entry (CCE). Store-operated Ca(2+) influx signals increase in permeability and nitric oxide (NO) production and provokes changes in gene expression in endothelial cells. Recent studies have established that the Drosophila transient receptor potential (TRP) gene family of channels expressed in endothelial cells can function as SOC. Deletion of one of the TRP homologues, TRPC4, in mouse caused impairment in store-operated Ca(2+) current and Ca(2+) store release activated Ca(2+) influx in aortic and lung endothelial cells (LEC). In TRPC4 knockout (TRPC4(-/-)) mice, acetylcholine-induced endothelium-dependent smooth muscle relaxation was drastically reduced. In addition, TRPC4(-/-) mice LEC exhibited lack of actin stress fiber formation and cell retraction in response to thrombin activation of proteinase-activated receptor-1 (PAR-1) in endothelial cells. The increase in lung microvascular permeability in response to thrombin receptor activation was inhibited in TRPC4(-/-) mice. These results indicate that endothelial TRP channels such as TRPC1 and TRPC4 play an important role in signaling the increase in endothelial permeability.
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PMID:Role of Ca2+ signaling in the regulation of endothelial permeability. 1274 58

Over twenty years ago it was shown that depletion of the intracellular Ca2+ store in smooth muscle triggered a Ca2+ influx mechanism. The purpose of this review it to describe recent electrophysiological data which indicate that Ca2+ influx occurs through discrete ion channels in the plasmalemma of smooth muscle cells. The effect of external Ca2+ on the amplitude and reversal potential of whole-cell and single channel currents suggests that there are at least two, and probably more, distinct store-operated channels (SOCs) which have markedly different permeabilities to Ca2+ ions. Two activation mechanisms have been identified which involve Ca2+ influx factor and protein kinase C (PKC) activation via diacylglycerol. In addition, in rabbit portal vein cells there is evidence that stimulation of alpha-adrenoceptors can stimulate SOC opening via PKC in a store-independent manner. There is at present little knowledge on the molecular identity of SOCs but it has been proposed that TRPC1 may be a component of the functional channel. We also summarise the data showing that SOCs may be involved in contraction and cell proliferation of smooth muscle. Finally, we highlight the similarities and differences of SOCs and receptor-operated cation channels that are present in native rabbit portal vein myocytes.
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PMID:Store-operated Ca2+-permeable non-selective cation channels in smooth muscle cells. 1276 81

Ca2+ homeostasis mechanisms, in which the Ca2+ entry pathways play a key role, are critically involved in both normal function and cancerous transformation of prostate epithelial cells. Here, using the lymph node carcinoma of the prostate (LNCaP) cell line as a major experimental model, we characterize prostate-specific store-operated Ca2+ channels (SOCs)--a primary Ca2+ entry pathway for non-excitable cells--for the first time. We show that prostate-specific SOCs share major store-dependent, kinetic, permeation, inwardly rectifying, and pharmacological (including dual, potentiation/inhibition concentration-dependent sensitivity to 2-APB) properties with "classical" Ca2+ release-activated Ca2+ channels (CRAC), but have a higher single channel conductance (3.2 and 12pS in Ca2+- and Na+-permeable modes, respectively). They are subject to feedback inhibition via Ca2+-dependent PKC, CaMK-II and CaM regulatory pathways and are functionally dependent on caveolae integrity. Caveolae also provide a scaffold for spatial co-localization of SOCs with volume-regulated anion channels (VRAC) and their Ca2+-mediated interaction. The TRPC1 and TRPV6 members of the transient receptor potential (TRP) channel family are the most likely molecular candidates for the formation of prostate-specific endogenous SOCs. Differentiation of LNCaP cells to an androgen-insensitive, apoptotic-resistant neuroendocrine phenotype downregulates SOC current. We conclude that prostate-specific SOCs are important determinants in the transition to androgen-independent prostate cancer.
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PMID:Store-operated Ca2+ channels in prostate cancer epithelial cells: function, regulation, and role in carcinogenesis. 1276 82

GABAergic neurones in the mesencephalon are important regulators of dopamine neurones. Cholinergic projections from mesopontine nuclei preferentially synapse onto these GABAergic neurones, thus suggesting that ACh can regulate dopamine neurones indirectly by modulating GABAergic interneurones. Muscarinic receptors mediate excitation of these interneurones through a Ca(2+)-dependent mechanism. Using a mesencephalic primary culture model, we show here that muscarine (10 microM) increases intracellular Ca2+ concentrations ([Ca2+]i) in GABAergic interneurones. Compatible with previous anatomical data, our pharmacological studies further suggest that the M3 receptor is the primary mediator of this increase. The rise in [Ca2+]i induced by muscarine was not activity-dependent but required influx of Ca2+ from the extracellular medium. Consistent with the known coupling of the M3 receptor to PKC, the effect of muscarine was blocked by bisindolylmaleimide, a selective PKC antagonist. The effect of muscarine was inhibited by SKF 96365 and verapamil, drugs known to block non-selective cationic channels such as those formed by transient receptor potential (TRPC) proteins. Finally, GABAergic neurones were found to be immunopositive for TRPC1, 3, 5 and 6. Taken together, these results suggest that the Ca(2+)-dependent regulation of mesencephalic GABAergic neurones by muscarinic receptors requires activation of some receptor-operated Ca2+ channels through a PKC-dependent mechanism.
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PMID:M3-like muscarinic receptors mediate Ca2+ influx in rat mesencephalic GABAergic neurones through a protein kinase C-dependent mechanism. 1582 52

The ubiquitously expressed canonical transient receptor potential (TRPC) ion channels are considered important in Ca2+ signal generation, but their mechanisms of activation and roles remain elusive. Whereas most studies have examined overexpressed TRPC channels, we used molecular, biochemical, and electrophysiological approaches to assess the expression and function of endogenous TRPC channels in A7r5 smooth muscle cells. Real time PCR and Western analyses reveal TRPC6 as the only member of the diacylglycerol-responsive TRPC3/6/7 subfamily of channels expressed at significant levels in A7r5 cells. TRPC1, TRPC4, and TRPC5 were also abundant. An outwardly rectifying, nonselective cation current was activated by phospholipase C-coupled vasopressin receptor activation or by the diacylglycerol analogue, oleoyl-2-acetyl-sn-glycerol (OAG). Introduction of TRPC6 small interfering RNA sequences into A7r5 cells by electroporation led to 90% reduction of TRPC6 transcript and 80% reduction of TRPC6 protein without any detectable compensatory changes in the expression of other TRPC channels. The OAG-activated nonselective cation current was similarly reduced by TRPC6 RNA interference. Intracellular Ca2+ measurements using fura-2 revealed that thapsigargin-induced store-operated Ca2+ entry was unaffected by TRPC6 knockdown, whereas vasopressin-induced Ca2+ entry was suppressed by more than 50%. In contrast, OAG-induced Ca2+ transients were unaffected by TRPC6 knockdown. Nevertheless, OAG-induced Ca2+ entry bore the hallmarks of TRPC6 function; it was inhibited by protein kinase C and blocked by the Src-kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2). Importantly, OAG-induced Ca2+ entry was blocked by the potent L-type Ca2+ channel inhibitor, *nimodipine. Thus, TRPC6 activation probably results primarily in Na ion entry and depolarization, leading to activation of L-type channels as the mediators of Ca2+ entry. Calculations reveal that even 90% reduction of TRPC6 channels would allow depolarization sufficient to activate L-type channels. This tight coupling between TRPC6 and L-type channels is probably important in mediating smooth muscle cell membrane potential and muscle contraction.
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PMID:Role of endogenous TRPC6 channels in Ca2+ signal generation in A7r5 smooth muscle cells. 1620 51

We have reported previously that Delta9-tetrahydrocannabinol (Delta9-THC) treatment of resting human and murine splenic T cells robustly elevated intracellular calcium ([Ca2+]i). The objective of the present investigation was to examine the putative role of [Ca2+]i store depletion and store-operated calcium (SOC) and receptor-operated cation (ROC) channels in the mechanism by which Delta9-THC increases [Ca2+]i in the cannabinoid-2 receptor-expressing human peripheral blood-acute lymphoid leukemia (HPB-ALL) human T cell line. By using the smooth endoplasmic reticulum Ca2+-ATPase pump inhibitor, thapsigargin, and the ryanodine receptor antagonist, 8-bromo-cyclic adenosine diphosphate ribose, we demonstrate that the Delta9-THC-mediated elevation in [Ca2+]i occurs independently of [Ca2+]i store depletion. Furthermore, the ROC channel inhibitor, SK&F 96365 was more efficacious at attenuating the Delta9-THC-mediated elevation in [Ca2+]i than SOC channel inhibitors, 2-aminoethoxydiphenyl borate and La3+. Recently, several members of the transient receptor potential canonical (TRPC) channel subfamily have been suggested to operate as SOC or ROC channels. In the present studies, treatment of HPB-ALL cells with 1-oleoyl-2-acetyl-sn-glycerol (OAG), a cell-permeant analog of diacylglycerol (DAG), which gates several members of the TRPC channel subfamily, rapidly elevated [Ca2+]i, as well as prevented a subsequent, additive elevation in [Ca2+]i by Delta9-THC, independent of protein kinase C. Reverse transcriptase-polymerase chain reaction analysis for TRPC1-7 showed that HPB-ALL cells express detectable mRNA levels of only TRPC1. Finally, small interference RNA knockdown of TRPC1 attenuated the Delta9-THC-mediated elevation of [Ca2+]i. Collectively, these results suggest that Delta9-THC-induced elevation in [Ca2+]i is attributable entirely to extracellular calcium influx, which is independent of [Ca2+]i store depletion, and is mediated, at least partially, through the DAG-sensitive TRPC1 channels.
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PMID:Induction of intracellular calcium elevation by Delta9-tetrahydrocannabinol in T cells involves TRPC1 channels. 1624 7

The hypothesis that calcium signaling proteins segregate into lipid raft-like microdomains was tested in isolated membranes of rat oligodendrocyte progenitor (OP) cells and astrocytes using Triton X-100 solubilization and density gradient centrifugation. Western blot analysis of gradient fractions showed co-localization of caveolin-1 with proteins involved in the Ca2+ signaling cascade. These included agonist receptors, P2Y1, and M1, TRPC1, IP3R2, ryanodine receptor, as well as the G protein Galphaq and Homer. Membranes isolated from agonist-stimulated astrocytes showed an enhanced recruitment of phospholipase C (PLCbeta1), IP3R2 and protein kinase C (PKC-alpha) into lipid raft fractions. IP3R2, TRPC1 and Homer co-immunoprecipitated, suggesting protein-protein interactions. Disruption of rafts by cholesterol depletion using methyl-beta-cyclodextrin (beta-MCD) altered the distribution of caveolin-1 and GM1 to non-raft fractions with higher densities. beta-MCD-induced disruption of rafts inhibited agonist-evoked Ca2+ wave propagation in astrocytes and attenuated wave speeds. These results indicate that in glial cells, Ca2+ signaling proteins might exist in organized membrane microdomains, and these complexes may include proteins from different cellular membrane systems. Such an organization is essential for Ca2+ wave propagation.
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PMID:Signaling proteins in raft-like microdomains are essential for Ca2+ wave propagation in glial cells. 1690 88

Renewal of nongermative epithelia is poorly understood. The novel mitogen "lacritin" is apically secreted by several nongermative epithelia. We tested 17 different cell types and discovered that lacritin is preferentially mitogenic or prosecretory for those types that normally contact lacritin during its glandular outward flow. Mitogenesis is dependent on lacritin's C-terminal domain, which can form an alpha-helix with a hydrophobic face, as per VEGF's and PTHLP's respective dimerization or receptor-binding domain. Lacritin targets downstream NFATC1 and mTOR. The use of inhibitors or siRNA suggests that lacritin mitogenic signaling involves Galpha(i) or Galpha(o)-PKCalpha-PLC-Ca2+-calcineurin-NFATC1 and Galpha(i) or Galpha(o)-PKCalpha-PLC-phospholipase D (PLD)-mTOR in a bell-shaped, dose-dependent manner requiring the Ca2+ sensor STIM1, but not TRPC1. This pathway suggests the placement of transiently dephosphorylated and perinuclear Golgi-translocated PKCalpha upstream of both Ca2+ mobilization and PLD activation in a complex with PLCgamma2. Outward flow of lacritin from secretory cells through ducts may generate a proliferative/secretory field as a different unit of cellular renewal in nongermative epithelia where luminal structures predominate.
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PMID:Restricted epithelial proliferation by lacritin via PKCalpha-dependent NFAT and mTOR pathways. 1692 31


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