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)

Heterologous expression of the rat 5-HT1A receptor in stably transfected GH4C1 rat pituitary cells (clone GH4ZD10) and mouse Ltk- fibroblast cells (clone LZD-7) (Albert, P.R., Zhou, Q.-Y., VanTol, H.H.M., Bunzow, J.R., and Civelli, O. (1990) J. Biol. Chem. 265, 5825-5832) was used to characterize the cellular specificity of signal transduction by the 5-HT1A receptor. We demonstrate that the 5-HT1A receptor, acting via pertussis toxin-sensitive G proteins, can change its inhibitory signaling phenotype and become a stimulatory receptor, depending on the cell type, differentiation state, or intracellular milieu of the cell in which it is expressed. When expressed in pituitary GH4ZD10 cells, activation of 5-HT1A receptors decreased both basal and vasoactive intestinal peptide-enhanced cAMP accumulation and blocked (+/-)-Bay K8644-induced influx of calcium, inhibitory responses which are typical of neurons which endogenously express this receptor. Similarly, 5-hydroxytryptamine (5-HT) also inhibited adenylyl cyclase in fibroblast LZD-7 cells, reducing the forskolin-induced enhancement of cAMP levels by 50%, but did not alter basal cAMP levels. In contrast to GH4ZD10 cells, where 5-HT had no effect on basal or thyrotropin-releasing hormone-induced phosphatidylinositol turnover, 5-HT enhanced the accumulation of inositol phosphates and induced a biphasic increase in [Ca2+]i in LZD-7 cells. These dominant stimulatory actions of 5-HT, as well as the inhibitory effects, were absent in untransfected cells and displayed the potency and pharmacological specificity of the 5-HT1A receptor, indicating that the 5-HT1A subtype coupled to both inhibitory and stimulatory pathways in the fibroblast cell. The actions of 5-HT in GH and L cells were blocked by 24-h pretreatment with pertussis toxin, suggesting that inhibitory G proteins (Gi/G(o)) mediate both inhibitory and stimulatory signal transduction of the 5-HT1A receptor. However, the 5-HT-induced stimulatory pathway in fibroblasts was blocked selectively by acute (2-min) pretreatment with TPA, an activator of protein kinase C. This action of protein kinase C was potentiated by activation of protein kinase A, indicating that the expression of the stimulatory pathway of the 5-HT1A receptor in LZD-7 cells is modulated by second messengers.
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PMID:Cell-specific signaling of the 5-HT1A receptor. Modulation by protein kinases C and A. 166 Aug 81

The role of protein kinase C (PKC) in modulating platelet activation has been examined in platelets pre-incubated with either the PKC activator 12-O-tetradecanoylphorbol 13-acetate (TPA) or the non-specific protein kinase inhibitor, staurosporine. In order to determine where in the signal transduction pathway PKC is exerting its effect platelets were activated either with a receptor-operated stimulus platelet activating factor (PAF) or by direct elevation of [Ca2+]i (ionomycin) or with arachidonic acid which is converted into thromboxane B2 (TxB2). In PAF-stimulated platelets activation of PKC inhibited both [Ca2+]i elevation and TxB2 generation but had no effect on 5-hydroxytryptamine (5-HT) release whilst staurosporine increased the duration of [Ca2+]i elevation and potentiated TxB2 generation but inhibited 5-HT release. In ionomycin-stimulated platelets modulation of PKC had no effect on [Ca2+]i elevation but in contrast to PAF-stimulated platelets PKC activation caused potentiation of TxB2 generation and 5-HT release whilst inhibition of PKC caused inhibition of TxB2 generation and 5-HT release. Modulation of PKC did not affect arachidonic acid-induced TxB2 generation. These findings suggest that in receptor activated platelets endogenously activated PKC is exerting a negative feedback role, however, when [Ca2+]i elevation is not modified by PKC activation or inhibition (such as in ionomycin stimulated platelets) the relationship between the state of PKC activation and subsequent platelet functional responses corresponds more closely. The findings from this study suggest a different relationship between PKC and TxB2 generation than between PKC and dense granule release in PAF-stimulated platelets.
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PMID:Comparison of the role of protein kinase C in platelet functional responses induced by three different mechanisms, PAF, ionomycin and arachidonic acid. 166 Nov 65

1. Intracellular recordings were made from neurones in the nucleus accumbens in slices from the rat brain maintained in vitro. 2. Muscarine (1-100 microM) depolarized 101 of 107 neurones; this was associated with an increase in the input resistance. The potential change reversed polarity with conditioning hyperpolarization and the reversal potential was linearly related to the logarithm of the extracellular potassium concentration. 3. The depolarization caused by muscarine was not changed by tetrodotoxin (1 microM) or by a solution that contained lower levels of calcium (0.24 instead of 2.4 mM), higher levels of magnesium (5 instead of 1.2 mM) and cobalt (2 mM). 4. Muscarine caused an inward current and a decrease in slope conductance when applied to neurones voltage clamped near their resting potential (-82 mV). The current caused by muscarine reversed polarity at the potassium equilibrium potential. The current-voltage relation of the neurones between -60 and -120 mV was well fitted by assuming a voltage-independent potassium conductance and an inward rectifier potassium conductance; muscarine reduced predominantly the inward rectifier conductance. 5. Phorbol-12,13-diacetate (3 microM) and 5-hydroxytryptamine mimicked the action of muscarine. The inward currents caused by muscarine or 5-hydroxytryptamine were occluded by the inward current evoked by the phorbol ester. 6. The depolarization caused by muscarine was competitively antagonized by pirenzepine; the dissociation constant of 11 nM suggested involvement of the M1 receptor. 7. It is concluded that muscarine acts at M1 receptors to reduce the membrane potassium conductance and that activation of protein kinase C may be an intermediate step.
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PMID:Muscarine reduces inwardly rectifying potassium conductance in rat nucleus accumbens neurones. 169 82

The present study was undertaken to examine the action of endothelin-1 (ET-1) per se, or the combined effects of ET-1 with vasoconstrictor agonists such as acetylcholine (ACh), histamine (His), and 5-hydroxytryptamine (5-HT), all of which have been implicated in the genesis of coronary spasm. Isometric tension development and the cytosolic Ca2+ concentration [( Ca2+]i) in a ring segment of porcine coronary artery loaded with fura-2 were measured simultaneously with a mechanoelectric transducer and a fluorometer, respectively. ET-1 (30-100 pM) specifically potentiated the 5-HT-induced contraction without causing a significant increase in [Ca2+]i. This effect of the peptide seems to be qualitatively similar to that produced by the tumor-promoting phorbol ester, DPB. These results suggest that the combined stimulation of ET-1 and 5-HT augments the Ca2+ sensitivity of the contractile elements through the possible activation of protein kinase C.
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PMID:Synergistic coronary vasoconstriction produced by endothelin-1 in combination with 5-hydroxytryptamine. 172 25

1. In order to elucidate the physiological and potential pathological roles of endothelin-1 (ET-1) in coronary artery contraction and relaxation, we undertook the present study to examine the action of ET-1 itself, and the combined effects of ET-1 with vasoconstrictor agonists such as acetylcholine (ACh), histamine, and 5-hydroxytryptamine (5-HT), all of which have been implicated in the genesis of coronary spasm. 2. Isometric tension and cytosolic Ca2+ concentration ([Ca2+]i) in a ring segment of porcine coronary artery loaded with fura-2 were measured simultaneously. 3. ET-1 contracted the artery in a concentration-dependent manner; and nisoldipine, a Ca2+ channel blocking drug of the 1,4-dihydropyridine type, antagonized the ET-1 action non-competitively. A radio-receptor binding assay also indicated the mutually exclusive binding of ET-1 and (+)-[3H]-PN200-110, a Ca2+ channel ligand, to the membrane fraction of porcine coronary artery. 4. ET-1 (10-100 pM) increased tension and [Ca2+]i in a parallel manner, while at higher concentrations (1-10 nM) it produced further contraction with a small increase in [Ca2+]i. 5. ET-1 (30-100 pM) selectively potentiated the 5-HT-induced contraction 1.5 to 2 times over the control without causing a significant increase in [Ca2+]i, which seems to be qualitatively similar to a tumour promoting phorbol ester, 12-deoxyphorbol 13-isobutylate (DPB). Bay K 8644 (10 nM), on the other hand, potentiated the contraction in response to practically all agonists used and affected a concomitant increase in [Ca2+]i.6. A Ca2+ channel blocking drug such as diltiazem abolished the increase in [Ca2+]i and partially attenuated the mechanical potentiation produced by a small amount of ET-1 in combination with 5-HT.7. The results suggest that ET-1 and 5-HT interact functionally at the cellular or subcellular level and modulate the Ca2 + sensitivity of the contractile elements through the possible activation of protein kinase C.
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PMID:Potentiation by endothelin-1 of 5-hydroxytryptamine-induced contraction in coronary artery of the pig. 181 Jun 5

The stimulation of postsynaptic gamma-aminobutyric acid (GABA)B receptors leads to slow inhibitory postsynaptic potentials due to the influx of K(+)-ions. This was studied biochemically, in vitro in mammalian cultured spinal cord neurons by using 86Rb as a substitute for K+. (-)-Baclofen, a GABAB receptor agonist, produced a concentration-dependent increase in the 86Rb-influx. This effect was stereospecific and blocked by GABAB receptor antagonists like CGP 35 348 (3-aminopropyl-diethoxymethyl-phosphonic acid) and phaclofen. Apart from the GABAB receptors, both adenosine via adenosine1 receptors and 5-hydroxytryptamine (5-HT) via 5-HT1 alpha agonists also increased the 86Rb-influx. These agonists failed to show any additivity between them when they were combined in their maximal concentration. In addition, their effect was antagonized specifically by their respective antagonists without influencing the others. These findings suggest the presence of GABAB, adenosine1 and 5-HT1 alpha receptors in the cultured spinal cord neurons, which exhibit a heterologous regulation of the same K(+)-channel. The effect of these agonists were antagonized by phorbol 12,13-didecanoate, an activator of protein kinase C, and pretreatment with pertussis toxin. This suggests that these agonists by acting on their own receptors converge on the same K(+)-channel through the Gi/Go proteins. In summary, we have developed a biochemical functional assay for studying and characterizing GABAB synaptic pharmacology in vitro, using spinal cord neurons.
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PMID:A functional assay to measure postsynaptic gamma-aminobutyric acidB responses in cultured spinal cord neurons: heterologous regulation of the same K+ channel. 184 95

Platelets adhere to artificial surfaces in the initial stage of thrombus formation, but the subsequent steps in signal transduction that lead to platelet activation by artificial surfaces are not understood. When 0.325-micron diameter beads composed of a hydrophobic polymer, polymethylmethacrylate (PMMA), were added to gel-filtered aequorin-loaded platelets suspended in media containing Ca2+, the platelets aggregated; addition of fibrinogen was not required. Platelet aggregation was preceded by an increase in cytoplasmic Ca2+ and was accompanied by phosphorylation of the 47-Kd substrate of protein kinase C (PKC), 5-hydroxytryptamine (5-HT) release, and accumulation of phosphatidic acid. All these effects were partially inhibited by apyrase and aspirin. Monoclonal antibodies (MoAbs) 7E3 and M148 and the synthetic peptides RGDS and fibrinogen gamma chain fragment 400-411, all of which bind to the platelet fibrinogen receptor glycoprotein IIb-IIIa (GPIIb-IIIa) and inhibit fibrinogen binding, prevented PMMA-induced aggregation but did not inhibit the Ca2+ increase. Chymotrypsin-treated platelets aggregated after addition of fibrinogen, but not PMMA. We conclude that platelets interact initially with PMMA at membrane sites other than those required for fibrinogen binding, leading to activation of membrane phospholipases and PKC, an increase in cytoplasmic Ca2+, release of 5-HT, ADP, and fibrinogen from storage granules, and to platelet aggregation.
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PMID:Platelet activation by a synthetic hydrophobic polymer, polymethylmethacrylate. 191 61

Bronchial hyperresponsiveness in patients with asthma may be associated with a damaged or dysfunctional epithelium. Also, changes in the activities of protein kinase C have been implicated in the pathogenesis of asthma. This study examined the role of protein kinase C in the modulation of airway smooth muscle tone and the influence of the epithelium on this function. Phorbol-12,13-diacetate (PDA) (10(-8) to 10(-5) M) induced concentration-dependent and epithelium-independent relaxations of guinea pig tracheal rings. PDA (10(-8) to 10(-5) M) induced significantly greater relaxations of tracheal rings contracted with 5-hydroxytryptamine (10(-5) M) than in tissues contracted to an equivalent degree with acetylcholine (10(-6) M). In experiments using phenoxybenzamine (10(-7) M and 10(-5) M), the dissociation constant (KA) for acetylcholine was significantly greater than that for 5-hydroxytryptamine. The fraction of active receptors (q) calculated for acetylcholine was significantly smaller than that calculated for an equieffective concentration of 5-hydroxytryptamine. Relaxations to PDA in tissues contracted with acetylcholine (2 x 10(-6) M) or 5-hydroxytryptamine (10(-5) M) were significantly augmented by phenoxybenzamine (10(-5) M and 10(-7) M, respectively). PDA did not affect contractions to acetylcholine (10(-8) to 10(-3) M) in the presence of epithelium but caused a significant right-ward displacement of the acetylcholine concentration-contraction curve in the absence of epithelium. The concentration-contraction curves for 5-hydroxytryptamine (10(-8) to 10(-5) M) were significantly displaced to the right by PDA in the presence or absence of epithelium. This effect was greater in the absence of epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of airway smooth muscle tone by a phorbol ester in the guinea pig trachea: role of epithelium and receptor reserve of the contractile agent. 192 Jan 16

The effects of forskolin (1 microM) and EGTA (5 mM) on indirect cyclic AMP responses in slices of guinea-pig cerebral cortex were examined. Forskolin had little effect on the direct 2-chloroadenosine-stimulated cyclic AMP response. However, it completely abolished the glutamate-induced augmentation of this response. In contrast, forskolin had very little effect on the indirect cyclic AMP responses to noradrenaline, 5-hydroxytryptamine, and histamine. Conversely, rapid removal of extracellular calcium with EGTA 2 min before addition of the indirectly acting agent markedly reduced the augmentation responses produced by these latter agonists, but had little effect on the glutamate augmentation. When EGTA was added once a steady level of cyclic AMP had been achieved with the indirect agents, it was without effect on any of the responses. Thus, calcium appears to have a role in the early, but not the later, stages of the noradrenaline, 5-hydroxytryptamine, and histamine responses. A role for protein kinase C in the glutamate augmentation response was suggested, because forskolin inhibited the augmentation of the 2-chloroadenosine response produced by phorbol esters (which mimic the actions of diacylglycerol in activating protein kinase C). We conclude that there is more than one mechanism by which the augmentation of cyclic AMP responses can occur.
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PMID:Discriminatory effects of forskolin and EGTA on the indirect cyclic AMP responses to histamine, noradrenaline, 5-hydroxytryptamine, and glutamate in guinea-pig cerebral cortical slices. 196 33

In cultured rat aortic smooth muscle cells, angiotensin II induced tyrosine phosphorylation of at least 9 proteins with molecular masses of 190, 117, 105, 82, 79, 77, 73, 45 and 40 kDa in time- and dose-dependent manners. Other vasoconstrictors such as [Arg]vasopressin, 5-hydroxytryptamine and norepinephrine induced the tyrosine phosphorylation of the same set of proteins as angiotensin II. The tyrosine phosphorylation of these proteins was mimicked by the protein kinase C-activating phorbol ester, phorbol 12 myristate 13-acetate, and the Ca2+ ionophore, ionomycin. These results demonstrate that the vasoconstrictors stimulate the tyrosine phosphorylation of several proteins in vascular smooth muscle cells and suggest that the tyrosine phosphorylation reactions are the events distal to the activation of protein kinase C and Ca2+ mobilization in the intracellular signalling pathways of the vasoconstrictors.
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PMID:Vasoconstrictor-induced protein-tyrosine phosphorylation in cultured vascular smooth muscle cells. 206 81


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