EC:2.7.11.13 - FACTA Search

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)

Recent evidence has implicated activation of the N-methyl-D-aspartate (NMDA) class of glutamate receptor in the initiation of hippocampal long-term potentiation (LTP), an electrophysiological model of information storage in the brain. A separate line of evidence has suggested that activation of protein kinase C (PKC) and the consequent phosphorylation of its substrates is necessary for the maintenance of the LTP response. To determine if PKC activation is a consequence of NMDA receptor activation during LTP, we applied the NMDA receptor antagonist drug, DL-aminophosphonovalerate (APV) both immediately prior to and following high frequency stimulation, resulting in successful and unsuccessful blockade of LTP initiation, respectively. We then measured the phosphorylation of a PKC substrate (protein F1) in hippocampal tissue dissected from these animals. Only successful blockade of LTP initiation by prior application of APV was seen to block the LTP-associated increase in protein F1 phosphorylation measured in vitro (P less than 0.001 by ANOVA). This suggests that NMDA receptor-mediated initiation triggers maintenance processes that are, at least in part, mediated by protein F1 phosphorylation. These data provide the first evidence linking two mechanisms associated with LTP, NMDA receptor activation and PKC substrate phosphorylation.
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PMID:NMDA receptor blockade prevents the increase in protein kinase C substrate (protein F1) phosphorylation produced by long-term potentiation. 290 92

Previous work suggests that delayed protection against infarction following ischaemic preconditioning of rabbit myocardium may involve the activation of protein kinase C (PKC). Preconditioning in the presence of chelerythrine, an inhibitor of PKC, abolished the late anti-infarct effect of preconditioning. In the studies described here, we tested the hypothesis that direct PKC activation with an analogue of diacylglycerol, the physiological activator of PKC, would invoke an adaptive mechanism leading to enhanced myocardial tolerance to ischaemia 24 h later. Rabbits were treated with i.v. injections of 1,2-dioctanoyl-sn-glycerol (DiC8) 5 mg/kg or 15 mg/kg or an equivalent volume of vehicle solution. Twenty-four h after pretreatment, the animals were anaesthetised and underwent 30 min coronary artery occlusion with 120 min reperfusion. Infarct size was determined by triphenyltetrazolium staining. In vehicle pretreated rabbits, infarct-risk zone ratio was 32.8+/-2.6%. Pretreatment with DiC8 5 mg/kg did not significantly affect infarct size (26.3+/-4.0%), but pretreatment with DiC8 15 mg/kg resulted in a marked reduction in infarct size (18.0+/-3.4%, P<0.05, 1-way ANOVA). Reduction in infarct size with the higher dose of DiC8 was independent of myocardial risk zone size and systemic haemodynamic parameters during coronary occlusion. The haemodynamic effects of acute administration of DiC8 15 mg/kg were examined in a separate cohort of pentobarbitone-anaesthetised rabbits. The compound was found not to affect systolic blood pressure or heart rate under these conditions. We examined the possibility that increased ischaemic tolerance might be due to induction of the 27 and 72 kDa heat shock proteins (hsp27 and hsp70i) which are known to be cytoprotective and are upregulated by ischaemia and other stressful stimuli. Western blot analysis of left ventricular tissue revealed that neither protein was induced 24 h after treatment with DiC8 15 mg/kg. Thus, infarct limitation 24 h after DiC8 treatment did not appear to be due to increased tissue content of these proteins. The mechanisms of DiC8-induced delayed myocardial protection remain unclear. However, these data are compatible with the hypothesis that activation of PKC isoenzymes is an important intermediate signal of sub-acute cellular adaptation, and results in enhanced tolerance to ischaemia-reperfusion injury in myocardium many hours later.
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PMID:Attenuation of myocardial ischaemic injury 24 h after diacylglycerol treatment in vivo. 923 50

Desensitization is defined as a decreased functional response after continuous or repetitive stimulation of a receptor with its agonist. Thyrotropin (TSH) increases cAMP levels in normal and neoplastic thyroid tissue. The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) activates protein kinase C (PKC). The aim was to determine whether TPA induces heterologous desensitization of the TSH-adenylate cyclase (AC) signal transduction system. Three human thyroid neoplasms in culture for 6 months or longer (one papillary carcinoma, one Hurthle cell carcinoma, one follicular adenoma) were incubated with TSH (10 mU/ml) and TPA (1.6 x 10(-8) M) separately and together for various time periods (from 10 minutes to 24 hours). The mixture was subsequently incubated for 30 minutes with TSH. TPA alone had no effect on cAMP levels, but co-incubation of TPA and TSH caused a significant reduction in cAMP response when compared to the cAMP response that resulted after stimulation with only TSH (p < 0.001). cAMP levels in response to TSH decreased by 31%, 44%, and 57% after preincubation with TSH for 10 minutes, 4 hours, and 24 hours, respectively (p < 0.01; ANOVA). Co-incubation of cells with TPA and staurosporine (10 ng/ml), a PKC inhibitor, prevented the effect of TPA on desensitization at 10 minutes and blunted the effect at 4 hours. This is the first demonstration in human neoplastic thyroid cells that TPA induced heterologous desensitization of the cAMP response to TSH. This TPA-induced effect appears to involve PKC activation, as it can be blocked by staurosporine.
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PMID:Heterologous desensitization in neoplastic thyroid cells: influence of the phospholipase C signal transduction system on the thyrotropin-adenylate cyclase signal transduction system. 959 26

To better understand the biochemical events accompanying lung alveolarization and development, we studied the specific activity of the cAMP-dependent protein kinase (PKA) and the type 2A protein phosphastase (PP2A), and the activity and protein content of the calcium- and lipid-dependent protein kinase (PKC) in cytosolic preparations of lungs. Lungs were obtained from rat pups on day 2 of life and on days 7, 14, and 27 from pups exposed to hyperoxia (> 95% O2, days 4-14; 65% O2 days 15-27) or normoxia from day 4 onwards. There were no significant changes in PKA specific activity with developmental age or hyperoxic exposure. PKC specific activity increased significantly (P < .05) in normoxic animals from day 2 (64 +/- 13.5 pmol phosphate released/min/mg protein) to day 14 (105 +/- 9). The increase was sustained to day 27. There was no effect on PKC activity due to hyperoxia alone (ANOVA). This increase in PKC activity was accompanied by an increase in the mass of the delta, epsilon and zeta isoforms of PKC in normoxic pups. The gamma isoform of PKC was undetectable in all samples whereas the alpha and beta isoforms were detectable but showed no changes with developmental age. PP2A specific activity increased significantly (P < .05) from 13.3 +/- 0.5 nmol phosphate released/min/mg protein on day 2 to 17.7 +/- 0.9 on day 7 in normoxic pups, then returned to day 2 level at advanced developmental age. Hyperoxia exposure prevented the increase in enzyme activity observed on day 7 in normoxic animals. These data suggest that protein phosphorylation may be one mechanism by which alveolarization is regulated in developing lungs.
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PMID:Effect of developmental age and hyperoxia exposure on kinase and phosphatase activities in newborn rat lungs. 963 55

Inositol 1,4,5-trisphosphate (IP3), inositol 1,3,4,5-tetrakisphosphate (IP4) and protein kinase C (PKC) play important roles in the phosphoinositide hydrolysis signal transducing pathway. Several studies have shown severe deficits in both IP3 receptor levels and PKC levels and activity in Alzheimer's disease brain, although the relationship of these changes to disease pathology is poorly understood. In the present study, we determined the autoradiographic localization of [3H]IP3 and [3H]IP4 binding to their calcium mobilizing receptor sites and [3H]phorbol 12,13-dibutyrate ([3H]PDBu) binding to PKC in sections of entorhinal cortex/hippocampal formation and cerebellum from 24 cases that had been staged for Alzheimer's disease-related neurofibrillary changes and amyloid deposition according to Braak and Braak [Acta Neuropathol. Berl., 82 (1991) 239-259]. Results indicated that [3H]IP3 binding showed a trend towards a decline with staging for neurofibrillary changes in the entorhinal region (0.05 < P < 0.10, ANOVA) and subiculum (0.05 < P < 0.10). In the former region, [3H]IP3 binding showed a significant decline with staging for amyloid deposition (P < 0.05). [3H]IP3 binding in the CA1 region showed statistically significant declines with respect to both neurofibrillary changes and amyloid staging (P < 0.05). [3H]IP3 binding levels in the other hippocampal subregions were too low to quantify accurately. The binding of [3H]IP4 showed no significant changes with either neurofibrillary changes or amyloid staging in any of the regions investigated. In contrast, [3H]PDBu binding showed significant declines with neurofibrillary staging in the entorhinal region (P < 0.01), subiculum (P < 0.001), CA1 (P < 0.001), CA2 (P < 0.001), CA3 (P < 0.001) and CA4 (P < 0.0001) regions and the dentate gyrus (P < 0.0001). Of these regions, only the subiculum showed a significant decline of [3H]PDBu binding with amyloid staging. There were no significant neurofibrillary or amyloid stage-related changes in either [3H]IP3, [3H]IP4 or [3H]PDBu binding in the molecular layer of the cerebellum. These findings suggest that reduced IP3 receptor and PKC levels in the entorhinal cortex/hippocampal formation reflect and may be important for the progression of Alzheimer's disease neurofibrillary pathology. The data also suggests that hippocampal IP3 receptor loss is related to the extent of amyloid deposition.
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PMID:Loss of inositol 1,4,5-trisphosphate receptor sites and decreased PKC levels correlate with staging of Alzheimer's disease neurofibrillary pathology. 968 71

This study aims to investigate potential mechanisms involved in the stimulatory effect of amniotic fluid on prostaglandin production by fetal membranes. A cell culture study of amnion and chorion was obtained following elective caesarean section, incubated with amniotic fluid collected at term (37-42 weeks' gestation) following either spontaneous labour (n = 6) or elective caesarean section (n = 6). The effect of addition of cycloheximide and actinomycin D (inhibitors of translation and transcription respectively), and staurosporine and genistein (inhibitors of protein kinase C and tyrosine kinase respectively) to these cultures was investigated. ANOVA was employed for statistical analysis. Cycloheximide and staurosporine significantly inhibited the stimulatory effect of spontaneous labour and elective section amniotic fluid on PGE2 production by amnion, and PGEM production by chorion. Genistein significantly inhibited the stimulatory effect of spontaneous labour amniotic fluid on PGE2 and PGEM production by amnion and chorion respectively. The stimulatory effect of amniotic fluid on prostaglandin production is dependent on new protein synthesis, presumably cyclooxygenase (COX), and stimulation of cell signal transduction pathways involving protein kinase C and tyrosine kinase.
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PMID:Mechanisms involved in the stimulatory effect of amniotic fluid on prostaglandin production by human fetal membranes. 969 Jul 15

Nucleophosmin (NPM) is an estrogen-regulated nucleolar phosphoprotein; a substrate for phosphorylation by p34cdc2 kinase, protein kinase C, and casein kinase II; and a repressor of the transcriptional regulating activities of the YY1 and IFN regulatory factor-1 transcription factors. We have completed a pilot study to determine whether autoantibodies to NPM are present in breast cancer patients and explored the ability of these autoantibodies to predict recurrence in breast cancer patients. One hundred breast cancer patients were studied: 50 who recurred, and 50 matched for age and length of follow-up but who did not recur. Patients' sera were collected at the times of diagnosis (T1), six months before recurrence (T2), and at recurrence (T3). Recurrent and nonrecurrent patients did not differ in autoantibody levels at the times of diagnosis or recurrence. However, antiNPM autoantibody levels increase significantly between diagnosis and six months before recurrence in recurrent patients, whereas no change occurs over the comparable time period in nonrecurrent patients (repeated measures ANOVA; P = 0.041). At recurrence, the levels return to those seen at diagnosis. The greater the change in levels between T1 and T2, the greater the risk of recurrence within the next 6 months (conditional logistic regression: increase in risk for highest versus lowest tertile of change from T1 to T2; odds ratio, 3.25; 95% confidence interval, 1.04-10.18; P = 0.043). Consistent with the estrogenic/antiestrogenic regulation of the antigen in breast cancer cells, the levels of antiNPM autoantibodies are decreased 6 months before recurrence in patients treated with the antiestrogen tamoxifen (P = 0.012). The association between antiNPM levels and recurrence remained after adjustment for confounding factors. Further study of antiNPM autoantibody levels as a new and simple, intermediate serum biomarker for predicting both the timing of recurrence and monitoring response to endocrine manipulations in breast cancer patients is warranted.
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PMID:Autoantibodies to the nuclear phosphoprotein nucleophosmin in breast cancer patients. 986 29

Lysophosphatidate (LPA; 1-acyl-sn-glycero-3-phosphate) is a novel lipid mediator with diverse biological activity. The intracellular mechanisms that mediate the actions of LPA include activation of phospholipase C and protein kinase C (PKC), increases in intracellular Ca2+, inhibition of adenylyl cyclase, and activation of phospholipase D (PLD). We have shown that thyrotropin (TSH) mediated PLD activation involves both the cyclic adenosine monophosphate (cAMP) and PKC pathways. We determined the effects of LPA (10 or 50 microM; 30 minutes) on TSH- and forskolin-mediated cAMP production in FRTL-5 thyroid cells. Basal cAMP was unaffected by LPA. However, both 10 microM and 50 microM LPA inhibited TSH-mediated cAMP production by 66% and 64%, respectively (p < 0.01, ANOVA). A similar inhibition of forskolin-mediated cAMP production was observed following LPA (p < 0.01, ANOVA). After 30-minutes exposure to 50 microM LPA, TSH-mediated iodide uptake (IU) was unaffected. However, 50 microM LPA enhanced TSH-IU after 24-hour exposure by 23%+/-8% (p < 0.03, ANOVA) and inhibited TSH-IU following 72-hour exposure by 43%+/-10% (p < 0.02, ANOVA). There was no effect of LPA on basal IU. To determine whether PLD activation mediated the effects of LPA, PLD activity was examined in FRTL-5 thyroid cells 30 minutes after LPA exposure. While PLD was increased 3.5-fold compared to control values following 50 microM LPA (p < 0.05, ANOVA), no increase in PLD activation was seen following treatment with 10 microM LPA. Preliminary evidence revealed no effect of a protein kinase C inhibitor on LPA inhibition of cAMP generation. To examine the products of PLD activation, we measured the production of phosphatidate (PA) and diacylglycerol (DAG) in FRTL-5 thyroid cells following treatment with 50 microM LPA or 100 microU/mL TSH. Within 1 minute following LPA, a rapid spike of DAG production was observed (1.5- +/- 0.2-fold above basal, p < 0.05, ANOVA). No similar increases in PA or bisPA were demonstrated. However, TSH caused a steady increase in PA and DAG that reached a maximum after 30 minutes. In summary, the effects of LPA on differentiated thyroid function in FRTL-5 thyroid cells are complex. LPA inhibits TSH- and forskolin-mediated cAMP generation most likely via a direct inhibition of adenylyl cyclase, whereas its effects on TSH-IU involve other mechanisms, possibly including PLD activation.
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PMID:The effects of lysophosphatidate on thyrotropin-mediated differentiated thyroid function in FRTL-5 thyroid cells. 1041 Nov 26

Muscle insulin resistance in the chronic high-fat-fed rat is associated with increased membrane translocation and activation of the novel, lipid-responsive, protein kinase C (nPKC) isozymes PKC-theta and -epsilon. Surprisingly, fat-induced insulin resistance can be readily reversed by one high-glucose low-fat meal, but the underlying mechanism is unclear. Here, we have used this model to determine whether changes in the translocation of PKC-theta and -epsilon are associated with the acute reversal of insulin resistance. We measured cytosol and particulate PKC-alpha and nPKC-theta and -epsilon in muscle in control chow-fed Wistar rats (C) and 3-wk high-fat-fed rats with (HF-G) or without (HF-F) a single high-glucose meal. PKC-theta and -epsilon were translocated to the membrane in muscle of insulin-resistant HF-F rats. However, only membrane PKC-theta was reduced to the level of chow-fed controls when insulin resistance was reversed in HF-G rats [% PKC-theta at membrane, 23.0 +/- 4.4% (C); 39.7 +/- 3.4% (HF-F, P < 0.01 vs. C); 22.5 +/- 2.7% (HF-G, P < 0.01 vs. HF-F), by ANOVA]. We conclude that, although muscle localization of both PKC-epsilon and PKC-theta are influenced by chronic dietary lipid oversupply, PKC-epsilon and PKC-theta localization are differentially influenced by acute withdrawal of dietary lipid. These results provide further support for an association between PKC-theta muscle cellular localization and lipid-induced muscle insulin resistance and stress the labile nature of high-fat diet-induced insulin resistance in the rat.
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PMID:Acute reversal of lipid-induced muscle insulin resistance is associated with rapid alteration in PKC-theta localization. 1105 77

To determine the in vivo functional significance of troponin I (TnI) protein kinase C (PKC) phosphorylation sites, we created a transgenic mouse expressing mutant TnI, in which PKC phosphorylation sites at serines-43 and -45 were replaced by alanine. When we used high-perfusate calcium as a PKC activator, developed pressures in transgenic (TG) perfused hearts were similar to wild-type (WT) hearts (P = not significant, NS), though there was a 35% and 32% decrease in peak-systolic intracellular calcium (P < 0.01) and diastolic calcium (P < 0.005), respectively. The calcium transient duration was prolonged in the TG mice also (12-27%, ANOVA, P < 0.01). During global ischemia, TG hearts developed ischemic contracture to a greater extent than WT hearts (41 +/- 18 vs. 69 +/- 10 mmHg, perfusate calcium 3.5 mM, P < 0.01). In conclusion, expression of mutant TnI lacking PKC phosphorylation sites results in a marked alteration in the calcium-pressure relationship, and thus susceptibility to ischemic contracture. The reduced intracellular calcium and prolonged calcium transients suggests that a potent feedback mechanism exists between the myofilament and the processes controlling calcium homeostasis.
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PMID:Ischemic dysfunction in transgenic mice expressing troponin I lacking protein kinase C phosphorylation sites. 1115 84

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