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)

The LAN-1 clone, a cell line derived from a human neuroblastoma, possesses muscarinic receptors. The stimulation of these receptors with increasing concentrations of carbachol (CCh; 1-1,000 microM) caused a dose-dependent increase of the intracellular free Ca2+ concentration ([Ca2+]i). This increase was characterized by an early peak phase (10 s) and a late plateau phase. The removal of extracellular Ca2+ reduced the magnitude of the peak phase to approximately 70% but completely abolished the plateau phase. The muscarinic-activated Ca2+ channel was gadolinium (Gd3+) blockade and nimodipine and omega-conotoxin insensitive. In addition, membrane depolarization did not cause any increase in [Ca2+]i. The CCh-induced [Ca2+]i elevation was concentration-dependently inhibited by pirenzepine and 4-diphenylacetoxy-N-methylpiperidine methiodide, two rather selective antagonists of M1 and M3 muscarinic receptor subtypes, respectively, whereas methoctramine, an M2 antagonist, was ineffective. The coupling of M1 and M3 receptor activation with [Ca2+]i elevation does not seem to be mediated by a pertussis toxin-sensitive guanine nucleotide-binding protein or by the diacylglycerol-protein kinase C system. The mobilization of [Ca2+]i elicited by M1 and M3 muscarinic receptor stimulation seems to be dependent on an inositol trisphosphate-sensitive intracellular store. In addition, ryanodine did not prevent CCh-induced [Ca2+]i mobilization, and, finally, LAN-1 cells appear to lack caffeine-sensitive Ca2+ stores, because the methylxanthine was unable to elicit intracellular Ca2+ mobilization, under basal conditions, after a subthreshold concentration of CCh (0.3 microM), or after thapsigargin.
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PMID:LAN-1: a human neuroblastoma cell line with M1 and M3 muscarinic receptor subtypes coupled to intracellular Ca2+ elevation and lacking Ca2+ channels activated by membrane depolarization. 131 63

Metabotropic glutamate receptor (mGluR) is highly expressed in cerebellar Purkinje cells. The purpose of this study was pharmacological and immunocytochemical characterization of the mGluR in single cerebellar neurons, especially Purkinje cells. Ca2+ imaging with fura-2 in cultured cerebellar neurons, identified immunocytochemically, was used to record the direct effects of drugs in stable conditions. In addition, the expression of mGluR was examined, and expression of the intracellular receptor for inositol trisphosphate (IP3) produced by mGluR activation was studied immunocytochemically with specific antibodies. Purkinje neurons and some other neurons showed Ca(2+)-mobilizing responses to mGluR agonists. These responses were mediated by mGluR because they were not blocked by ionotropic GluR antagonists, were independent of the caffeine-sensitive Ca2+ pool, and were blocked by inhibitors of IP3-induced Ca2+ release. This is the first pharmacological characterization of mGluR at single Purkinje cells. The results differed as follows from those in earlier studies in which phosphoinositide turnover of the entire population of cerebellar cells was monitored: (1) the mGluR responses were not blocked by pertussis toxin or D,L-2-amino-3-phosphonopropionic acid; (2) glutamate was a potent agonist, whereas L-aspartate was ineffective; and (3) the dose-response relationship showed an all-or-none tendency. The metaboltropic response of Purkinje cells changed markedly during development, with a sharp peak after day 4 of culture, whereas mGluR and IP3 receptor proteins increased steadily during maturation. This apparent desensitization of mGluR was not blocked by inhibitors of protein kinase C (PKC) or ADP-ribosyltransferase. The metabotropic responses were mainly localized to the center of the somata of Purkinje cells even on day 4, whereas both receptor proteins were expressed throughout the cell. These results suggest that the function of mGluR is spatially and developmentally controlled by a posttranslational mechanism involving a mechanism other than phosphorylation by PKC or ADP-ribosylation.
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PMID:Pharmacological and immunocytochemical characterization of metabotropic glutamate receptors in cultured Purkinje cells. 133 61

We examined the effects of heparin, guanosine nucleotides, protein kinase C (PKC) modulators, such as phorbol 12,13-dibutyrate (PDBu) and H-7 on Ca(2+)-dependent K+ currents in smooth muscle cells of the rabbit portal vein using the whole-cell patch-clamp technique, to explore the effects of PKC on the oscillatory outward current (Ioo). Neomycin (30 microM), an inhibitor of phospholipase C, and intracellular applications of heparin (10 micrograms/ml) and guanosine 5'-O-(2-thiodiphosphate) (GDP[beta S]; 1 mM) partly but consistently inhibited the generation of Ioo, whereas a higher concentration of heparin (100 micrograms/ml) transiently enhanced then suppressed the generation of Ioo. Inhibition of Ioo generation by heparin was more powerful at the holding potential of +20 mV than at -20 mV. Inositol 1,4,5-trisphosphate (InsP3; 30 microM) continuously generated Ioo at holding potentials more positive than -60 mV. Noradrenaline (10 microM) and caffeine (3-20 mM) transiently augmented, then reduced the generation of Ioo. Heparin (10 micrograms/ml) completely inhibited responses induced by InsP3 and noradrenaline, but not those induced by caffeine. Intracellular application of guanosine 5'-triphosphate (GTP; 200 microM) or low concentrations of guanosine 5'-O-(3-thiotriphosphate) (GTP[gamma S]; < or = 3 microM) continuously augmented the generation of Ioo. High concentrations of GTP[gamma S] (> or = 10 microM) transiently augmented, then inhibited Ioo. Neither GTP[gamma S] nor noradrenaline induced the transient augmentation or the subsequent inhibition of Ioo when applied in the presence of GDP[beta S] (1 mM), neomycin (30 microM) or heparin (10 micrograms/ml). PDBu (0.1 microM) reduced the generation of Ioo but failed to produce an outward current following application of caffeine (3-5 mM). This action of PDBu was inhibited by pretreatment with H-7 (20 microM). In the presence of H-7, GTP[gamma S] continuously enhanced the generation of Ioo. The suppression of the generation of Ioo during application of noradrenaline (10 microM) was reduced by pretreatment with H-7. Thus both InsP3 and protein kinase C contribute to the generation of Ioo in smooth muscle cells of the rabbit portal vein and heparin is not a specific InsP3 antagonist on the InsP3-induced Ca(2+)-release channel (PIRC). InsP3 opens PIRC and protein kinase C may deplete the stored Ca2+ by either inhibiting the reuptake of Ca2+ or by enhancement of the releasing actions of InsP3.
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PMID:Roles of inositol trisphosphate and protein kinase C in the spontaneous outward current modulated by calcium release in rabbit portal vein. 133 73

The tumour promoter and protein kinase C agonist, 12-O-tetranodecanoyl-phorbol-13-acetate (TPA), has been reported to show a radiomimetic action because it transiently delays the passage of HeLa cells through the G2 phase, as do ionizing radiation and other DNA damaging agents. Caffeine is known to override the G2 delay imposed by DNA damage; it is shown here that caffeine does not override the radiomimetic delay imposed by TPA in HeLa, but instead enhances it, without affecting G2 progression in control cells. Most of the other agents which more specifically affect some of the diverse range of caffeine targets either do not affect G2 progression after TPA, or delay G2 progression in control cells and exert a further delay in the presence of TPA. The exception is 2-aminopurine, a protein kinase inhibitor which has been shown to have an action similar to that of caffeine is allowing progression of the cell cycle to mitosis after the inhibition of DNA synthesis, without affecting normal cycle progression through G2. This agent, like caffeine, also has the contrary action of retarding cycle progression after TPA. It is concluded that the G2 delays induced by ionizing radiation and by TPA operate by different mechanisms, which are modulated in opposite senses by mechanisms involving protein kinase inhibition.
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PMID:Radiomimetic cell cycle delay induced by tetranodecanoyl phorbol acetate is enhanced by caffeine and by the protein kinase inhibitor 2-aminopurine. 134 33

We investigated whether the enhanced contractile response to norepinephrine caused by a subthreshold concentration of angiotensin II was associated with an increased 45Ca++ influx or net uptake. Rabbit facial artery segments were mounted isometrically to measure the 45Ca++ influx and net uptake in response to norepinephrine. The contractile response to norepinephrine (3 microM) in the presence of angiotensin II (0.1 nM) was 149.5 +/- 7.4% of control. This response amplification was not associated with changes in norepinephrine-induced 45Ca++ influx or net uptake. Angiotensin II also potentiated the contractile response to caffeine obtained in a Ca(++)-free buffer containing ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid (2 mM) to 148.0 +/- 4.8% of control. In both cases, the amplification was prevented by pretreatment with either staurosporine (10 nM) or calphostin C (100 nM), two inhibitors of protein kinase C. We conclude that angiotensin II potentiation of norepinephrine-induced vascular tone occurs in the absence of changes in stimulated Ca++ entry. This potentiation may be due to an increase in intracellular sensitivity to Ca++, possibly mediated by protein kinase C.
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PMID:Angiotensin II amplifies arterial contractile response to norepinephrine without increasing Ca++ influx: role of protein kinase C. 137 60

1. In this study we have investigated the effects of short-term exposure of cells to histamine on the subsequent H1 receptor responsiveness in HeLa cells, using Ca2+ fluorescence microscopy and video digital imaging. 2. In HeLa cells, histamine (100 microM) induces an immediate H1 receptor-mediated biphasic elevation of the intracellular Ca2+ concentration ([Ca2+]i) (basal [Ca2+]i: 81 +/- 30 nM, histamine-induced Ca2+ response: first phase: 1135 +/- 79 nM; second phase: 601 +/- 52 nM, n = 11). 3. The histamine H1 receptors on HeLa cells are readily susceptible to desensitization since repetitive exposure of the same group of cells to histamine (100 microM) markedly affected the release and influx component of the induced Ca2+ response (second application of histamine: first phase: 590 +/- 92 nM, second phase: 279 +/- 47 nM; third application of histamine: first phase: 454 +/- 127 nM, second phase: 240 +/- 45 nM, n = 6). Video digital imaging revealed an increase in the lag time between stimulation and monitoring of the Ca2+ response and a reduced increase in [Ca2+]i after desensitization with histamine. 4. Neither the release component of the ATP response (50 microM) nor the caffeine (3 mM)-induced Ca2+ release were found to be affected by desensitization with 100 microM histamine. However, the second phase of the ATP response was significantly reduced after desensitization with histamine (control cells: 516 +/- 33 nM; desensitized cells: 331 +/- 96 nM, n = 4, P < 0.05).5. Activation of protein kinase C (PKC) by phorbol-12-myristate-1 3-acetate was found to inhibit the histamine as well as ATP-induced Ca2" response in a dose-dependent manner.6. In PKC downregulated cells the second phase of the histamine-induced Ca2+ response was significantly elevated, indicating the involvement of PKC in the negative feedback on the Ca2+ influx(control cells: second phase: 601 +/- 52 nM (n = 11); PKC downregulated cells: second phase:890 +/- 90nM, n = I0, P<0.05).7. Homologous desensitization of H, receptor responsiveness was still observed in PKC downregulated cells, implying the rapid activation of a regulatory mechanism other than PKC.8. Based on our experimental data we suggest that short-term desensitization of the histamine H,receptor evolves from two different processes: a selective reduction of the histamine-induced Ca2+ release, mediated by a PKC-independent pathway, and a non-selective inhibition of the receptormediated Ca2+ influx activated by a PKC-dependent pathway.
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PMID:Short-term desensitization of the histamine H1 receptor in human HeLa cells: involvement of protein kinase C dependent and independent pathways. 142 91

1. Voltage-clamp recordings of membrane current were made from Xenopus oocytes that had been injected with RNA which had been transcribed in vitro from a cloned complementary DNA. 2. Depolarization from -80 mV evoked outward potassium currents that developed very slowly. At -20 mV the time constant for activation was about 50 s, and at +40 mV about 6 s. 3. The potassium current was increased by the calcium ionophore A23187 or by intracellular injection of inositol 1,4,5-trisphosphate (IP3), each of which should increase the intracellular calcium concentration ([Ca2+]i). The current was decreased by injection of BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). The current was also reduced by phorbol esters; this effect was blocked by staurosporine. 4. In oocytes that had also been injected with RNA encoding the 5-hydroxytryptamine (5-HT2) receptor, 5-HT increased the potassium current. After caffeine pretreatment, to block the release of intracellular calcium, 5-HT decreased the current; this decrease was prevented by staurosporine. 5. It is concluded that the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes is increased by increases in [Ca2+]i and is decreased by activation of protein kinase C. Stimulation of 5-HT2 receptors can have both these effects, but the former normally predominates.
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PMID:Regulation by second messengers of the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes. 143 14

The role of phosphatidylinositol (PI) turnover in excitation-contraction coupling was investigated in canine antral smooth muscle. Acetylcholine (ACh; 0.1-1 microM) transiently increased tissue levels of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and increased the amplitudes of the plateau phase of slow waves and associated Ca2+ transients and phasic contractions. ACh also increased basal concentrations of cytosolic Ca2+ ([Ca2+]c), but these changes were not associated with an increase in resting tension. ATP (0.3 mM) had similar effects on Ins(1,4,5)P3 levels, basal [Ca2+]c, and resting tension. However, in contrast to the effects of ACh, ATP transiently reduced the amplitude of the plateau phase of slow waves and reduced the amplitudes of associated Ca2+ transients and phasic contractions. We investigated the possibility that two products of PI turnover, diacylglycerol (DAG) and Ins(1,4,5)P3, might provide negative feedback to regulate Ca2+ entry during slow waves. 1) DAG is known to activate protein kinase C (PKC). Activation of PKC by phorbol 12,13-dibutyrate (PDBu, 0.5 microM) reduced the amplitude of the plateau phase of slow waves and corresponding Ca2+ transients and phasic contractions. Assay of PKC showed that ACh, ATP, and PDBu stimulated enzyme activity. 2) Ins(1,4,5)P3 is known to increase [Ca2+]c by release of Ca2+ from internal stores. Basal [Ca2+]c was also increased by elevated external K+, ionomycin, thapsigargin, or caffeine. Each of these compounds reduced the amplitude and duration of slow waves. Results suggest that products of PI turnover may provide negative-feedback control of Ca2+ influx during slow waves, tending to reduce the amplitude of phasic contractile activity in gastric muscles. Differences in responses to ACh and ATP can be explained by a G protein-dependent mechanism in which ACh suppresses the voltage dependence of Ca(2+)-activated K+ channels.
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PMID:Negative-feedback regulation of excitation-contraction coupling in gastric smooth muscle. 147 62

Phorbol esters, which activate protein kinase C, modulate vasoconstrictor-induced tension in vascular smooth muscle. We examined the effects of phorbol esters (phorbol 12,13-dibutyrate [PDBu] and 12-O-tetradecanoylphorbol 13-acetate [TPA]) on receptor agonist (serotonin [5-HT] and arginine vasopressin [AVP])-, high K(+)-, and caffeine-induced contractions in rings of rat aorta and a small (second-order) branch of the superior mesenteric artery (SMA). PDBu and TPA significantly augmented agonist-evoked contractions in aorta but diminished those in SMA. For example, 30 nM PDBu increased 5-HT- and AVP-evoked contractions 2.0-2.5-fold in aorta (p less than 0.01) but decreased 5-HT- and AVP-induced contractions by 40-60% in SMA (p less than 0.01). In contrast, PDBu and TPA amplified high K(+)- and 10 mM caffeine-induced contractions in both aorta and SMA. Augmentation of agonist-induced contractions by PDBu was greater in endothelium-denuded aorta than in intact aorta. Two protein kinase C antagonists, H-7 and staurosporine, inhibited 5-HT-evoked contractions in the absence as well as in the presence of PDBu in both types of arteries. The augmentation of contractile responses to caffeine and K+ by phorbol esters in both types of arteries suggests that the phorbols increase the sensitivity of the contractile apparatus to Ca2+, probably by activating protein kinase C. However, the inhibitory effects of phorbols on 5-HT- and AVP-evoked responses in SMA suggest that under these conditions the dominant effect of the phorbols is a marked reduction in the availability of Ca2+ in the SMA but not in the aorta.
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PMID:Contrasting effects of phorbol esters on serotonin- and vasopressin-evoked contractions in rat aorta and small mesenteric artery. 156 5

Although kappa- and delta-opioid receptors on mammalian cardiac myocytes have been discovered recently, the intracellular effects that result from stimulation of these receptors remain unknown. We examine the effects of a rapid and brief exposure to a kappa-opioid receptor agonist on intracellular Ca2+, pH, and cell length in individual isolated rat ventricular cells. The specific kappa-agonist trans-dl-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]- benzene-acetamide (U-50488H) (methane sulfonate salt) caused a transient increase in cytosolic pH (pHi) measured from the change in SNARF-1 fluorescence and an increase in cytosolic [Ca2+] (Cai), indexed by a change in indo-1 fluorescence. The initial Cai increase often was followed by Cai oscillations. Both pHi and Cai effects were blocked by the specific antagonist kappa-opioid receptor l-(N-furylmethyl)-alpha-normetazocine methane-sulfonate (Mr 1452). The amplitude of contraction that accompanied the Cai increase elicited by U-50488H was greater than that associated with a similar increase in Cai elicited by electrical stimulation or by the rapid exposure of cells to caffeine. Thus an acute and brief kappa-opioid receptor stimulation of cardiac cells leads to an increase in Cai and pHi. The pHi increase was abolished by 1) blockade of the Na(+)-H+ exchanger by ethyl isopropyl amiloride and 2) inhibition of protein kinase C (PKC) activity via pretreatment with staurosporine or prolonged incubation with 4 beta-phorbol 12-myristate 13-acetate. These maneuvers did not abolish the U-50488H-induced increase in Ca.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Kappa-opioid peptide receptor stimulation increases cytosolic pH and myofilament responsiveness to Ca2+ in cardiac myocytes. 165 31


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