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)

The effects of cocaine on glycine-induced Cl- current (I(GLY)) of single neurons, freshly isolated from the rat hippocampal CA1 area, were studied with conventional whole-cell recording under voltage-clamp conditions. Cocaine depressed I(GLY) in a concentration-dependent manner, with an IC50 of 0.78 mM. Preincubation with 1 mM cocaine alone had no effect on I(GLY), suggesting that resting glycine channels are insensitive to cocaine. The depression of I(GLY) by cocaine was independent of membrane voltage. Internal cell dialysis with 1 mM cocaine failed to modify I(GLY). Because the depression of I(GLY) was noncompetitive, cocaine may act on the glycine receptor-chloride ionophore complex at a site distinct from that to which glycine binds. The cocaine suppression of I(GLY) was unaffected by 1 microM tetrodotoxin and 1 microM strychnine. Blockers of protein kinase C (Chelerythrine), kinase A (N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide HCl, (H-89)) and Ca-calmodulin-dependent kinase (1-[N,O-bis(5-isoquinoline-sulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperaz ine (KN-62)) were also ineffective, which suggests that these phosphorylating mechanisms do not modulate cocaine-induced suppressant action on I(GLY). This extracellular, strychnine-independent depression of I(GLY) may contribute to cocaine-induced seizures.
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PMID:Cocaine decreases the glycine-induced Cl- current of acutely dissociated rat hippocampal neurons. 1008 75

1. C335Stop is a constitutively active mutant of the TRH receptor (TRH-R). To investigate the mechanism of the decreased responsiveness of C335Stop TRH-R, we studied cellular Ca2+ concentrations ([Ca2+]i) in AtT20 cells stably transfected with C335Stop TRH-R cDNA, or Ca2+-activated chloride currents in Xenopus laevis oocytes expressing this mutant receptor after injection of cRNA. The competitive TRH-R binding antagonist, chlorodiazepoxide (CDE), was used as an inverse agonist to study the contribution of constitutive activity to desensitization. 2. Acute treatment with CDE resulted in a rapid (within minutes) decrease in [Ca2+]i and an increase in the response amplitude to TRH with no measurable change in receptor density. Conversely, removal of chronically administered CDE caused a rapid increase in [Ca2+]i and a decrease in TRH response amplitude. 3. CDE abolished heterologous desensitization induced by C335Stop TRH-R on muscarinic m1-receptor (ml-R) co-expressed in Xenopus oocytes. 4. Chelation of extracellular calcium with EGTA caused a rapid decrease in [Ca2+]i and a concomitant increase in the response to TRH in AtT20 cells expressing C335Stop TRH-Rs. 5. Chelerythrine, a specific inhibitor of protein kinase C (PKC), reversed the heterologous desensitization of the response to acetylcholine (ACh). The phosphoserine/phosphothreonine phosphatase inhibitor, okadaic acid, abolished the effect of chelerythrine. 6. Down-regulation of PKC by chronic exposure to phorbol 12-myristate 13-acetate (PMA) or acute inhibition with chelerythrine caused a partial resensitization of the response to TRH. 7. Western analysis indicated that the alpha subtype of protein kinase C was down-regulated in cells expressing C335Stop TRH-Rs. Following a 5 min exposure to PMA, the residual alphaPKC translocated to the particular fraction. 8. We propose that cells expressing the constitutively active mutant TRH-R rapidly desensitize their response, utilizing a mechanism mediated by an increase in [Ca2+]i and PKC.
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PMID:Inverse agonist abolishes desensitization of a constitutively active mutant of thyrotropin-releasing hormone receptor: role of cellular calcium and protein kinase C. 1020 96

Repetitive brief ischemic episodes (ischemic preconditioning, PC) result in transient intracellular acidosis and protect the heart from subsequent ischemic injury, potentially through a protein kinase C (PKC)-dependent mechanism. We hypothesized that repetitive brief acidification of the heart without concomitant ischemia would also protect the heart from ischemic injury via a PKC-dependent mechanism. Isolated rat hearts underwent 30 min of global ischemia following control perfusion (CTL), or after PC or repetitive acidosis (RA), in the presence of absence of chelerythrine, a specific PKC inhibitor. Intracellular pH, PCr and ATP were measured using 31P NMR spectroscopy, while intracellular sodium [Na]i was measured using 23Na spectroscopy. Na,K-ATPase activity was measured prior to ischemia and on reperfusion. Both PC and RA resulted in transient acidification prior to ischemia. Ischemic injury, as assessed by creatinine kinase (CK) release on reperfusion, was reduced in both the PC and RA hearts [63+/-14 and 16+/-4 IU/g dry weight (dw) respectively, v 705+/-72 IU/gdw for control P<0.001], and was associated with improved functional recovery on reperfusion. PC and RA each significantly reduced Na,K-ATPase activity prior to ischemia (8.18+/-0.47 and 7.76+/-0.54 micromol ADP/h/mg protein) when compared to control (11.05+/-0.54 micromol ADP/h/mg protein P<0.05), limited the rate of ATP depletion during ischemia, and resulted in more rapid normalization of [Na]i on reperfusion. Chelerythrine resulted in intermediate CK release in PC and RA hearts (443+/-48 and 375+/-72 IU/gdw, P<0.001 v PC, P<0.01 v control), but did not alter the rate of ATP depletion or [Na]i kinetics in either PC or RA hearts. PC and RA each protect the ischemic heart, having in common ATP preservation during ischemia and more rapid normalization of [Na]i on reperfusion. These effects, not modulated by protein kinase C, are consistent with the hypothesis that ATP preservation during ischemia provides enhanced substrate for sodium efflux via the Na,K-ATPase on reperfusion.
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PMID:Repetitive acidosis protects the ischemic heart: implications for mechanisms in preconditioned hearts. 1032 17

This study was designed to determine whether mechanical stretch activates the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway in cardiomyocytes and, if so, by what mechanism. Neonatal rat/murine cardiomyocytes were cultured on malleable silicone dishes and were stretched by 20%. Mechanical stretch induced rapid phosphorylation of JAK1, JAK2, Tyk2, STAT1, STAT3, and glycoprotein 130 as early as 2 minutes and peaked at 5 to 15 minutes. It also caused gel mobility shift of sis-inducing element, which was supershifted by preincubation with anti-STAT3 antibody. Preincubation with CV11974 (AT1 blocker) partially inhibited the phosphorylation of STAT1, but not that of STAT3. Preincubation with TAK044 (endothelin-1-type A/B-receptor blocker) did not attenuate this pathway. RX435 (anti-glycoprotein 130 blocking antibody) inhibited the phosphorylation of STAT3 and partially inhibited that of STAT1. Phosphorylation of STAT1 and STAT3 was strongly inhibited by HOE642 (Na+/H+ exchanger inhibitor) and BAPTA-AM (intracellular calcium chelator), but not by gadolinium (stretch-activated ion channel inhibitor), EGTA (extracellular Ca2+ chelator), or KN62 (Ca2+/calmodulin kinase II inhibitor). Chelerythrine (protein kinase C inhibitor) partially inhibited the phosphorylation of STAT1 and STAT3. Mechanical stretch also augmented the mRNA expression of cardiotrophin-1, interleukin-6, and leukemia inhibitory factor at 60 to 120 minutes. These results indicated that the JAK/STAT pathway was activated by mechanical stretch, and that this activation was partially dependent on autocrine/paracrine-secreted angiotensin II and was mainly dependent on the interleukin-6 family of cytokines but was independent of endothelin-1. Moreover, certain levels of intracellular Ca2+ were necessary for stretch-induced activation of this pathway, and protein kinase C was also partially involved in this activation.
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PMID:Mechanical stretch activates the JAK/STAT pathway in rat cardiomyocytes. 1034 87

Implant surface roughness influences osteoblast proliferation, differentiation, and local factor production. Moreover, the responsiveness of osteoblasts to systemic hormones such as 1, 25-(OH)(2)D(3) is altered by the effects of surface roughness; on the roughest Ti surfaces the effects of roughness and 1, 25-(OH)(2)D(3) are synergistic. Prostaglandin E(2) (PGE(2)) appears to be involved in mediating the effects of surface roughness on the cells, as well as in the response to 1,25-(OH)(2)D(3). However, it is not yet known through which signaling pathways surface roughness exerts its effects on the response of osteoblasts to 1, 25-(OH)(2)D(3). The present study examined the potential role of protein kinase A (PKA), phospholipase A(2)(PLA(2)), and protein kinase C (PKC) in this process. MG63 osteoblast-like human osteosarcoma cells were cultured on cpTi disks with R(a) values of 0. 54 microm (PT), 4.14 microm (SLA), or 4.92 microm (TPS). PKA was inhibited by adding H8 to the cultures; similarly, PLA(2) was inhibited with quinacrine or activated with melittin, and PKC was inhibited with chelerythrine. Inhibitors or activators were included in the culture media through the entire culture period or for the last 24 h of culture. In addition, cultures were treated for 24 h with inhibitors or activators in the presence of 1,25-(OH)(2)D(3). The effects on cell number and alkaline phosphatase specific activity were determined after 24 h; PKC activity was determined after 9 min and at 24 h. Cell number was reduced on rough surfaces, and alkaline phosphatase activity was increased. 1,25-(OH)(2)D(3) had a synergistic effect with surface roughness on alkaline phosphatase. However, neither surface roughness nor 1,25-(OH)(2)D(3) had an effect on PKC. H8 treatment for 24 h inhibited cell number and alkaline phosphatase on all surfaces; however, when it was present throughout the culture period, the PKA inhibitor had no effect on cell number, but decreased alkaline phosphatase-specific activity. H8 reduced the 1,25-(OH)(2)D(3)-mediated effect on cell number and alkaline phosphatase. Quinacrine inhibited cell proliferation and alkaline phosphatase on all surfaces and further reduced the 1,25-(OH)(2)D(3)-dependent decreases in both parameters. Melittin had no effect when applied for 24 h and did not modify the 1,25-(OH)(2)D(3) effect; however, when present throughout the culture period, it caused a decrease in proliferation and an increase in enzyme activity. Chelerythrine, the PKC inhibitor, only inhibited cell proliferation when it was present throughout the entire culture period. However, it decreased alkaline phosphatase in cultures treated for 24 h, but increased enzyme activity when it was present for the entire culture period. The results indicate that surface roughness and 1,25-(OH)(2)D(3) both mediate their effects through PLA(2) which catalyzes the rate-limiting step in PGE(2) production. Further downstream, PGE(2) activates PKA. Surface roughness-dependent effects are also mediated through PKC, but only after the cells have reached confluence and are undergoing phenotypic maturation. The effect of surface roughness on responsiveness to 1,25-(OH)(2)D(3) is mediated through PLA(2)/PKA and not through PKC.
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PMID:Surface roughness modulates the response of MG63 osteoblast-like cells to 1,25-(OH)(2)D(3) through regulation of phospholipase A(2) activity and activation of protein kinase A. 1044 25

Prolonged treatment with serotonin leads to long-term facilitation of sensory-to-motor neuron synapses in Aplysia. We have shown previously that there is a protein synthesis-dependent increase in an autonomous kinase activity that phosphorylates a protein kinase C substrate during an intermediate phase of this facilitation. Here, I report that the increase in autonomous activity was independent of RNA synthesis, suggesting it may play a role in the maintenance phase of synaptic facilitation. Immunoprecipitation experiments using an antibody specific to the Ca(2+)-independent protein kinase C, Apl II, demonstrated that the autonomous kinase activity increased by serotonin emanated from Apl II. Chelerythrine, an inhibitor targeted to the substrate binding site of protein kinase C, also blocked the autonomous kinase activity increased by serotonin. Using immunoblotting experiments and calphostin-C, an inhibitor targeted to the regulatory domain of protein kinase C, the autonomous activity is shown not to be a catalytic fragment of Apl II. Furthermore, a higher concentration of calphostin-C was required to inhibit autonomous kinase activity than regulated kinase activity, suggesting that calphostin-C's binding site in the regulatory domain of Apl II is modified in the autonomous kinase. These data suggest that an autonomous kinase derived from Apl II may play a role in synaptic facilitation in Aplysia.
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PMID:An autonomous kinase generated during long-term facilitation in Aplysia is related to the Ca(2+)-independent protein kinase C Apl II. 1045 6

Myocardial ischemia results in an increase in intracellular sodium concentration ([Na]i), which may lead to cellular injury via cellular swelling and calcium overload. Because protein kinase C (PKC) has been shown to reduce Na-K-ATPase activity, we postulated that pharmacological inhibition of PKC would directly increase Na-K-ATPase activity, reduce [Na]i during ischemia, and provide protection from ischemic injury. Isolated rat hearts were subjected to 30 min of global ischemia with and without the specific PKC inhibitor chelerythrine. Intracellular pH, ATP, and [Na]i were assessed using 31P and 23Na NMR spectroscopy, whereas Na-K-ATPase and PKC activity were determined using biochemical assays. Na/H exchanger activity was determined using the ammonium prepulse technique under nonischemic conditions. Chelerythrine increased Na-K-ATPase activity (13.76 +/- 0.89 vs. 10.89 +/- 0.80 mg ADP. h(-1). mg protein(-1); P = 0.01), reduced PKC activity in both the membrane and cytosolic fractions (39% and 28% of control, respectively), and reduced creatine kinase release on reperfusion (48 +/- 5 IU/g dry wt vs. 689 +/- 63 IU/g dry wt; P = 0.008). The rise in [Na](i) during ischemia was significantly reduced in hearts treated with chelerythrine (peak [Na](i) chelerythrine: 21.5 +/- 1.2 mM; control: 31.9 +/- 1.2 mM; P < 0.0001), without an effect on either acidosis (nadir pH 6.16 +/- 0.05 for chelerythrine vs. 6.08 +/- 0.04 for control), the rate of ATP depletion or Na/H exchanger activity. These data support the hypothesis that pharmacological inhibition of PKC before ischemia induces cardioprotection by reducing intracellular sodium overload via an increase in Na-K-ATPase activity.
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PMID:Chelerythrine increases Na-K-ATPase activity and limits ischemic injury in isolated rat hearts. 1048 22

Experiments were designed to examine the role of sphingosine, PP2A phosphatases, and protein kinase C (PKC) inhibition in mediating the vasodilatory effects of ceramide in rat thoracic aorta. Sphingosine did not cause vasorelaxation, and oleoylethanol-amine, a ceramidase inhibitor, did not affect sphingomyelinase-induced relaxation. Okadaic acid potentiated the relaxation response to ceramide. These observations rule out involvement of sphingosine and PP2A phosphatases in mediating ceramide-induced relaxation. Sphingomyelinase attenuated contractile and single-cell intracellular calcium responses to phorbol ester. Chelerythrine incubation potentiated the relaxation response to ceramide. These observations support a role for PKC inhibition in mediating the vasodilatory effects of ceramide.
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PMID:Ceramide-induced vasorelaxation: An inhibitory action on protein kinase C. 1055 83

Activation of protein kinase C (PKC) protects the heart from ischemic injury; however, its mechanism of action is unknown, in part because no model for chronic activation of PKC has been available. To test whether chronic, mild elevation of PKC activity in adult mouse hearts results in myocardial protection during ischemia or reperfusion, hearts isolated from transgenic mice expressing a low level of activated PKCbeta throughout adulthood (beta-Tx) were compared with control hearts before ischemia, during 12 or 28 min of no-flow ischemia, and during reperfusion. Left-ventricular-developed pressure in isolated isovolumic hearts, normalized to heart weight, was similar in the two groups at baseline. However, recovery of contractile function was markedly improved in beta-Tx hearts after either 12 (97 +/- 3% vs. 69 +/- 4%) or 28 min of ischemia (76 +/- 8% vs. 48 +/- 3%). Chelerythrine, a PKC inhibitor, abolished the difference between the two groups, indicating that the beneficial effect was PKC-mediated. (31)P NMR spectroscopy was used to test whether modification of intracellular pH and/or preservation of high-energy phosphate levels during ischemia contributed to the cardioprotection in beta-Tx hearts. No difference in intracellular pH or high-energy phosphate levels was found between the beta-Tx and control hearts at baseline or during ischemia. Thus, long-term modest increase in PKC activity in adult mouse hearts did not alter baseline function but did lead to improved postischemic recovery. Furthermore, our results suggest that mechanisms other than reduced acidification and preservation of high-energy phosphate levels during ischemia contribute to the improved recovery.
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PMID:Long-term expression of protein kinase C in adult mouse hearts improves postischemic recovery. 1055 56

Although protein kinase C (PKC) plays a pivotal role in ischemic preconditioning, it is not clear what the end effector is that protects the myocardium. In isolated, paced (1.25 Hz, 36-37 degrees C) adult rat cardiomyocytes, the effects of PKC preactivation by diacylglycerol on cell motion, intracellular Ca(2+) concentration ([Ca(2+)](i); indo 1), and intracellular pH (pH(i); seminaphthorhodafluor-1) during simulated ischemia-reperfusion (I/R) were investigated. The degree of reperfusion-induced contracture was significantly attenuated in the myocytes pretreated with 10 microM 1, 2-dioctanoyl-sn-glycerol (DOG; n = 19) compared with the untreated myocytes (n = 23, P < 0.02). There were no differences in twitch amplitude, end-diastolic [Ca(2+)](i), or peak-systolic [Ca(2+)](i) during I/R between the DOG-pretreated and untreated myocytes. Although there were no differences in pH(i) during ischemia, the pH(i) overshoot during reperfusion was significantly delayed in the DOG-pretreated myocytes compared with the untreated myocytes (n = 17 for each, P < 0.01). Chelerythrine completely abolished the favorable effects of DOG on the reperfusion-induced contracture and the pH(i) overshoot. These data suggest that diacylglycerol attenuates I/R injury in isolated, paced cardiomyocytes, which may be related to the slower pH(i) overshoot during reperfusion.
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PMID:Diacylglycerol delays pH(i) overshoot after reperfusion and attenuates contracture in isolated, paced myocytes. 1056 23


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