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)

We have determined whether the process of agonist-mediated phosphorylation of the muscarinic receptor correlates with the process of muscarinic receptor desensitization in chick cardiac tissue. Exposure of ventricular slices to the agonist carbachol under conditions previously shown to lead to large increases in muscarinic receptor phosphorylation (Kwatra, M. M., and Hosey, M. M. (1986) J. Biol. Chem. 261, 12429-12432) resulted in decreased affinity of the muscarinic receptor for agonists. The agonist oxotremorine mimicked and the antagonist atropine prevented the effects of carbachol on receptor phosphorylation and agonist affinity. The time courses and concentration dependences for agonists to induce phosphorylation of the muscarinic receptor and decreases in agonist affinity were similar. Treatment of chick atria with acetylcholine under conditions which led to receptor phosphorylation resulted in decreased sensitivity of these preparations to the negative inotropic effect of carbachol. Taken together, the results support the concept that phosphorylation of cardiac muscarinic receptors may be related to the process of receptor desensitization. The mechanism by which agonists induce receptor phosphorylation was also investigated. The phosphorylated amino acids formed in response to agonists were serine and threonine. The protein kinase C activator phorbol myristate acetate had no effect on receptor phosphorylation or agonist affinity, nor did it prevent the effects of carbachol on either of these parameters. Receptor phosphorylation also was unaffected by the calmodulin antagonists W-7 and W-13, by elevation of cyclic nucleotides, and by agonists which activate other cardiac receptor systems. The results suggest that the phosphorylation of cardiac muscarinic receptors requires agonist occupancy of the receptor and/or may involve the participation of a selective protein kinase.
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PMID:Correlation of agonist-induced phosphorylation of chick heart muscarinic receptors with receptor desensitization. 368 Feb 52

We have developed the coexpression system of both delta-opioid receptor (DOR1) and M2-muscarinic receptor (M2) which mediate agonist-evoked currents due to common post-receptor mechanisms including Gi1 and phospholipase C (PLC) activation in Xenopus oocytes reconstituted with Gi1 alpha. The DOR1-currents by 100 nM D-Ser2-leu-enkephalin-Thr6 (DSLET) were selectively desensitized by 10 nM phorbol 12-myristate 13-acetate (PMA). The PMA-desensitization of DSLET-currents was abolished in the presence of calphostin C, a protein kinase C inhibitor, or reversed by an intracellular injection of calcineurin, a protein phosphatase 2B. When a higher concentration (3 microM) of DSLET was used, DSLET-currents were rapidly desensitized by repeated challenges of DSLET itself. However, repeated challenges of 10 microM ACh caused no influence on such DSLET- or M2-currents. The desensitization of DSLET-currents was selectively reversed by protein kinase C inhibitors. Similar results were also obtained with various delta-opioid agonists. These results suggest that protein kinase C is involved in the homologous desensitization of delta-opioid receptors.
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PMID:Protein kinase C involvement in homologous desensitization of delta-opioid receptor coupled to Gi1-phospholipase C activation in Xenopus oocytes. 747

The preceding paper [Y. G. Wang and S. L. Lipsius, Am. J. Physiol. 268 (Heart Circ. Physiol. 37): H1313-H1321, 1995.] showed that when an atrial myocyte is treated with two consecutive exposures to acetylcholine (ACh) separated by a recovery interval, the second ACh exposure elicits a larger increase in K+ conductance than the first ACh exposure. In the present study a nystatin-perforated patch whole cell recording method was used to determine the mechanisms underlying the potentiating effect of ACh on ACh-induced K+ currents and the nature of the potentiated K+ current. The K+ current potentiated by the second ACh exposure was selectively abolished by 1) M1 muscarinic receptor block by 0.1 microM pirenzepine, 2) depletion of sarcoplasmic reticulum (SR) Ca2+ stores by 1 microM ryanodine or 10 mM caffeine, 3) intracellular dialysis with 10 mM ethylene glycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), 4) omitting external Ca2+, 5) 50% external Na+, 6) inhibition of protein kinase C by 0.01 microM staurosporine or 0.1 microM calphostin C, or 7) inhibition of ATP-sensitive K+ channels with 10 microM glibenclamide (Glib). AFDX-116 (100 microM), an M2 muscarinic receptor antagonist, selectively abolished the conventional ACh-activated K+ current and revealed an ACh-activated Glib-sensitive K+ current. In addition, with K+ conductances blocked and zero external Ca2+, 10 microM ACh induced a small nonselective inward current carried by Na+.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Acetylcholine activates a glibenclamide-sensitive K+ current in cat atrial myocytes. 753 7

The effect of staurosporine on the Ca2+ signalling induced by the muscarinic receptor agonist carbachol (CCh) was studied in Fura-2-loaded rat parotid acinar cells. At concentrations > 1 nM, staurosporine dose-dependently enhanced the sustained increase in cytosolic free Ca2+ concentration ([Ca2+]i), but did not affect the peak [Ca2+]i seen just after stimulation. The enhancement of the sustained increase in [Ca2+]i was not attenuated by the protein kinase C activator, 4 beta-phorbol 12-myristate 13-acetate, and not mimicked by another inhibitor of protein kinase C, K-252a, suggesting that the effect of staurosporine on the CCh-induced Ca2+ signalling may be due to a mechanism independent of the inhibitory action on protein kinase C. Staurosporine also enhanced the increases in [Ca2+]i induced by the microsomal Ca(2+)-ATPase inhibitor thapsigargin (TG) and the Ca2+ ionophore ionomycin (Iono). When the cells were stimulated by CCh, TG, or Iono in the absence of extracellular Ca2+, a transient increase in [Ca2+]i due to Ca2+ release from intracellular stores was observed. This increase in [Ca2+]i was unaffected by preincubation with staurosporine. However, when Ca2+ was added to the extracellular medium after [Ca2+]i had returned to the resting level, the increase in [Ca2+]i was significantly enhanced by staurosporine. In addition, staurosporine accelerated the Mn2+ influx following the addition of CCh, TG, or Iono. These results suggest that staurosporine modulates the Ca2+ entry system activated by depletion of intracellular Ca2+ stores in rat parotid acinar cells.
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PMID:Staurosporine enhances Ca2+ entry induced by depletion of intracellular Ca2+ stores in rat parotid acinar cells. 755 79

The structure of protein kinase C zeta (PKC zeta) is unusual with respect to other PKCs, as it lacks the C2 domain and possesses only one zinc finger region. Consequently, PKC zeta can not be activated by diacylglycerol or phorbol esters and is not downregulated by prolonged treatment by phorbol esters nor blocked by commonly utilized PKC inhibitors. In this study, we have explored the idea that PKC zeta might participate in proliferative pathways. Our findings show that marked overexpression of mammalian PKC zeta does not alter the growth characteristics of NIH 3T3 cells, nor induces cellular transformation. Furthermore, mammalian PKC zeta does not potentiate the transforming ability of oncogenes such as ras, sis and the muscarinic receptor m1. In this context, PKC zeta or its dominant negative mutant do not affect MAP kinase activation by oncogenes or growth factors. Taken together, our findings demonstrate that mammalian PKC zeta does not directly participate in signaling pathways involved in oncogenic transformation.
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PMID:Overexpression of mammalian protein kinase C-zeta does not affect the growth characteristics of NIH 3T3 cells. 763 44

Our previous work on atrial myocytes suggested that the effect of acetylcholine (ACh) to increase K+ conductance can be potentiated by prior loading of the sarcoplasmic reticulum (SR) with Ca2+. The present study, therefore, sought to determine whether prior exposure to isoproterenol (ISO) potentiates ACh-induced increases in K+ conductance and the underlying mechanisms. A nystatin-perforated patch whole-cell configuration was used to record from cat atrial myocytes. Voltage-clamp ramps (40 mV/s) were used to assess total membrane conductance. The experimental protocol consisted of two consecutive 30-second ACh exposures (ACh1 and ACh2) separated by a 6-minute recovery period in ACh-free solution. In general, experimental interventions, such as exposure to ISO, were imposed during the period between ACh1 and ACh2 to determine their effects on the response to ACh2 in relation to ACh1. Under control conditions, K+ conductances induced by ACh1 and ACh2 were not different from one another with or without activation of L-type Ca2+ current (ICa,L) during the recovery period. When 1 mumol/L ISO plus ICa,L activation was imposed during the recovery period, ACh2 induced a significantly larger increase in K+ conductance than ACh1. The ACh2-induced K+ current potentiated by ISO was time independent and selectively blocked by 10 mumol/L glibenclamide and therefore identified as ATP-sensitive K+ current (IK,ATP). The effect of ISO to induce ACh2-activated IK,ATP was mimicked by 1 mumol/L forskolin or 200 mumol/L 8-(4-chlorophenylthio)-cAMP, but not by 0.5 mumol/L BAY K 8644, and was selectively abolished by (1) 5 mumol/L thapsigargin or 1 mumol/L ryanodine, agents that prevent accumulation of SR Ca2+, (2) inhibition of L-type Ca2+ current (ICa,L) by 1 mumol/L nisoldipine or zero external Ca2+, (3) 50 mumol/L Rp-cAMPs, an inhibitor of cAMP-dependent protein kinase A, or (4) 2 mumol/L propranolol. Atropine (1 mumol/L) abolished all ACh-induced currents. Moreover, ACh2-activated IK,ATP was selectively blocked by 0.2 mumol/L pirenzepine, an M1 muscarinic receptor antagonist, or 0.1 mumol/L calphostin C, a selective inhibitor of protein kinase C. AFDX116 (100 mumol/L), an M2 muscarinic receptor antagonist, blocked the conventional ACh-activated K+ current and revealed ACh2-activated IK,ATP. These results indicate that prior exposure to ISO potentiates ACh-induced increases in K+ current via ACh-activated IK,ATP.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:beta-Adrenergic stimulation induces acetylcholine to activate ATP-sensitive K+ current in cat atrial myocytes. 764 26

In SH-SY5Y human neuroblastoma cells, addition of acetylcholine or carbachol rapidly induces a transient protrusion of lamellipodia. The protrusions appear after a delay of 30 sec and persist for a period of about 5 min at the margins of cell somata and at the distal parts of cell processes. They are caused by a strikingly increased, cytochalasin B-sensitive assembly of actin at the cell periphery. They often detach from the substrate, retracting and protruding again. In retinoic acid-induced neuronally differentiated cells, this initialized protrusive activity is restricted to growth cones. d-Tubocurarine does not influence, but atropine totally inhibits the cholinergic induction of the actin-driven protrusions, suggesting that a muscarinic receptor-mediated activation of the phosphoinositol signaling pathway is involved. Depolarization by increase of the potassium concentration and ionophore-mediated Ca(2+)-influx are ineffective to trigger the protrusive and ruffling activity. An identical cytochalasin B-sensitive actin-driven response is caused by treating of the cells with the protein kinase C (PKC) activator 12-myristate-13-acetate. In this case, however, lamellar protrusions are formed after a delay of at least 3 min and are maintained for several days. Incubating the cells with the protein kinase C inhibitor bisindolylmaleide or staurosporine inhibits both the muscarinic receptor-mediated and phorbolester-mediated actin-driven response, suggesting that activated PKC plays a crucial role.
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PMID:Muscarinic receptor-mediated induction of actin-driven lamellar protrusions in neuroblastoma cell somata and growth cones. Involvement of protein kinase C. 765 99

The effect of ethanol on muscarinic receptor-stimulated formation of inositol 1,4,5-trisphosphate was studied in human neuroblastoma SH-SY5Y cells. Stimulation with carbachol induced a biphasic increase of inositol 1,4,5-triphosphate with an initial peak after 10 sec declining to a plateau phase of elevation above basal levels, which was sustained for at least 5 min in the presence of agonist. The peak, but not the plateau phase, was concentration-dependently decreased by exposure to ethanol. Maximal inhibition was obtained within 30 sec of exposure to ethanol. Ethanol caused an increase in the EC50 value of carbachol for the initial rate of inositol 1,4,5-trisphosphate formation, measured after 10 sec of stimulation, from 98 microM in the absence to 196 microM in the presence of 100 mM ethanol. The potencies of pirenzepine and hexahydro-sila-difenidol hydrochloride for inhibiting [3H]quinuclidinyl benzilate binding and inositol 1,4,5-trisphosphate formation suggest that both phases are mediated via the muscarinic M1 receptor. Phorbol 12-myristate 13-acetate inhibited both phases of inositol 1,4,5-trisphosphate formation, whereas okadaic acid and modulators of cAMP-dependent protein kinase were without any effect. There was no inhibitory effect of ethanol when protein kinase C was inhibited by H7 and calphostin C, indicating that the ethanol effect is dependent on protein kinase C activity.
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PMID:Ethanol inhibits the peak of muscarinic receptor-stimulated formation of inositol 1,4,5-trisphosphate in neuroblastoma SH-SY5Y cells. 766 67

Transient peaks of quisqualate (QA)-, but not 1S,3R-1-amino-3-cyclopentane dicarboxylate (1S,3R-ACPD)- and carbachol-induced inositol phosphate formation occur between 2 and 5 days in vitro (DIV) in hippocampal neurons in culture. In order to elucidate the putative origin of such developmental activity differences, the effect of PKC on metabotropic glutamate receptor (mGluR) and muscarinic receptor responses was investigated at 3 and 10 DIV. (i) Stimulation of PKC by phorbol-12,13-dibutyrate inhibited QA, 1S,3R-ACPD and carbachol responses at 3 DIV. At 10 DIV, only 1S,3R-ACPD response was still inhibited by phorbol esters. (ii) Inhibition of PKC by staurosporine at 3 DIV potentiated 1S,3R-ACPD-induced inositol phosphate formation, but had no effect on QA and carbachol responses. At 10 DIV, all responses were potentiated by staurosporine. These data strongly suggest that PKC differently modulates 1S,3R-ACPD- and QA-induced inositol phosphate accumulations during in vitro development. The specific activity of mGluRs during development, vs that of muscarinic receptor, and the peculiar modes of regulation by PKC of these two mGluR activities further suggest their particular involvement in the maturation of neuronal culture.
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PMID:Protein kinase C differently regulates quisqualate- and 1S,3R-trans aminocyclopentane dicarboxylate-induced phosphoinositide hydrolysis during in vitro development of hippocampal neurons. 767 Mar 65

The human neuroblastoma cells SH-SY5Y were treated with the differentiation agents 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or dimethyl sulfoxide (DMSO) and the muscarinic receptor subtype M1 and M2 RNA levels analyzed. After a decrease induced by both agents, the M1 level gradually returned to normal in the presence of TPA but remained minimal with DMSO. As for M2, several phases were observed with TPA, while DMSO caused a drastic increase. The data obtained with TPA were tentatively correlated with the amounts of immunoreactive PKC alpha. In conclusion, our results reveal: (a) differential regulation of M1 and M2 muscarinic receptor subtypes by either treatment; (b) opposing effects of TPA and DMSO on both subtypes.
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PMID:Different regulatory patterns of M1 and M2 muscarinic receptor subtype RNA in SH-SY5Y human neuroblastoma induced by phorbol ester or DMSO. 768 3


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