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)

It has been demonstrated that erythropoietin (EPO) influences rat and human Leydig cell steroidogenesis, stimulating testosterone production through a direct and specific receptor-mediated mechanism. The aim of this study was to investigate the mechanism by which recombinant human erythropoietin (rHuEPO) exerts its stimulatory effect on rat Leydig cells. Recombinant human EPO did not induce, at any dose tested (10(-10) to 10(-13) mol/l), an increase in either cAMP or cGMP, suggesting that in Leydig cells the effect of rHuEPO does not involve the adenylate or guanylate-cyclase systems. The role of transmembrane calcium flux in rHuEPO-stimulated steroidogenesis was studied by evaluating the effect of calcium channel blocker, verapamil, and by the 45Ca2+ uptake method. Verapamil did not influence rHuEPO-induced testosterone secretion and rHuEPO did not modify calcium recycling, indicating that calcium transmembrane flux is not involved in the rHuEPO effect. The protein kinase C inhibitor staurosporine (10, 30, 100 and 300 nmol/l) inhibited rHuEPO-stimulated testicular steroidogenesis in a dose-dependent manner. This indirect evidence suggests that the stimulatory effect of rHuEPO on rat Leydig cells may involve protein kinase C activation.
 ...
PMID:Erythropoietin and testicular steroidogenesis: the role of second messengers. 785 3

In cultured bovine adrenal chromaffin cells, pituitary adenylate cylase-activating polypeptide (PACAP) stimulated [14C]catecholamine synthesis from [14C]tyrosine (but not from [14C]DOPA) in a concentration-dependent manner, causing maximal stimulation at 10(-7) M. The stimulatory action of PACAP was not affected by staurosporine (an inhibitor of protein kinase C) or in the cells in which protein kinase C was down-regulated by prolonged exposure to TPA (an activator of protein kinase C), whereas it was partially attenuated in Ca(2+)-free medium. PACAP (10(-7) M) increased the formation of [3H]inositol phosphates, [Ca2+]i and 45Ca2+ uptake as well as cAMP. The peptide also stimulated the phosphorylation of tyrosine hydroxylase, the enzyme catalyzing the rate-limiting step in catecholamine synthesis. Catecholamine synthesis and tyrosine hydroxylase phosphorylation stimulated by the maximal effective concentration of dibutyryl cAMP or high K+, which activates Ca2+ uptake, were further enhanced by PACAP, suggesting that both cAMP- and Ca(2+)-dependent protein kinases may be involved in the stimulation of tyrosine hydroxylase phosphorylation and catecholamine synthesis caused by PACAP.
 ...
PMID:Stimulatory effect of pituitary adenylate cyclase-activating polypeptide on catecholamine synthesis in cultured bovine adrenal chromaffin cells: involvements of tyrosine hydroxylase phosphorylation caused by Ca2+ influx and cAMP. 786 19

Using AMP deaminase (AMP aminohydrolase; EC 3.5.4.6) purified from rabbit left-ventricular heart tissue, we report direct investigation of the potential for cardiac AMP deaminase activity to be regulated by kinase-mediated phosphorylation. Rabbit heart AMP deaminase served as a substrate for Ca2+/phospholipid-dependent protein kinase (protein kinase C; PKC) exclusively; no other mammalian protein kinase phosphorylated the enzyme. PKC-dependent AMP deaminase phosphorylation was rapid, linear with respect to time and the concentrations of PKC and AMP deaminase in the reaction, and inhibitable by staurosporine. Upon phosphorylation, the apparent Km of cardiac AMP deaminase decreased from 5.6 mM to 1.2 mM, without effect on the Vmax. Whether phosphorylated or not, rabbit heart AMP deaminase was inhibited by 1.0 mM GTP, which decreased the Vmax. by approximately 50% in each case. PKC-dependent phosphorylation of cardiac AMP deaminase did not alter the enzyme's allosterism toward millimolar ATP or ADP: both nucleotides at 1.0 mM concentration decreased the apparent Km to approximately 0.5 mM. Treatment of cardiac phospho-AMP deaminase with either the protein phosphatase calcineurin or alkaline phosphatase generated a dephosphorylated form which displayed molecular and kinetic properties identical with those of the originally isolated enzyme. These data raise the possibility that a phosphorylation-dephosphorylation mechanism may regulate flux through AMP deaminase in the heart under pathological conditions, such as myocardial ischaemia, characterized by PKC activation and adenylate depletion.
 ...
PMID:Modulation of mammalian cardiac AMP deaminase by protein kinase C-mediated phosphorylation. 838 71

In the human gastric adenocarcinoma cell line AGS the effects of the protein-kinase-C-activating phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), the protein kinase C inhibitor staurosporine, the adenylate-cyclase activating agent forskolin, and the permeable dibutyryl-adenosine 3',5'-monophosphate (Bt2cAMP) on the proliferation were assessed. Cell counting followed 5 days of incubation. Prolonged activation of protein kinase C by TPA, inhibition of protein kinase C by staurosporine, activation of adenylate cyclase by forskolin or a direct increase of the intracellular cAMP level all result in a dose-dependent growth inhibition of AGS gastric tumour cells. Half-maximal inhibition was achieved at 100 pM for TPA, 1 nM for staurosporine, 20 microM for forskolin, and 600 microM for Bt2cAMP. It is concluded that protein kinase C and adenylate cyclase play a fundamental role in the growth of AGS gastric cancer cells. Interference with these enzymes involved in the signal transduction of growth regulation in tumour cells may represent a target in the development of new antiproliferative principles.
 ...
PMID:Protein kinase C and adenylate cyclase as targets for growth inhibition of human gastric cancer cells. 840 80

Recently, the pituitary adenylate-cyclase activating polypeptide (PACAP) has emerged as a potential noncholinergic neuromodulator of adrenal medullary function. In support of this hypothesis, we documented PACAP's effects on the secretion and biosynthesis of neuropeptides by cultured bovine chromaffin cells. Data presented in this study indicate that PACAP is a potent and efficacious secretagogue of leucine-enkephalin which was coreleased with catecholamines with identical profiles. In comparison to nicotinic activation, however, rates of PACAP-induced secretion were substantially slower but persisted for several hours causing a prolonged increase in the tonic release of both transmitters and peptides. Interestingly, renewal of intracellular pools of neuropeptides was also stimulated by PACAP but not the vasoactive intestinal peptide (VIP). Indeed, the higher incorporation of [35S]-labeled amino acids into atrial and brain natriuretic peptides (ANP, BNP) provided strong evidence that PACAP directly activated de novo biosynthesis. Of particular importance was PACAP's net preferential stimulation of the biosynthesis of BNP, similar to the differential regulation by protein kinase A (PK-A) and protein kinase C (PK-C) activators we have previously the differential regulation by protein kinase A (PK-A) and protein kinase C (PK-C) activators we have previously reported. PACAP-induced secretion and biosynthesis appeared to be mediated by the PACAP-specific type I receptors known to activate adenylate cyclase and phospholipase C. We verified that PACAP did indeed stimulate the production of cyclic AMP and inositol phosphates in our cell system. These findings suggest that the dual signaling properties of type I receptors may be important for PACAP's differential effect on the biosynthesis of natriuretic peptides. We conclude that PACAP might assume important noncholinergic trans-synaptic regulation of the adrenal medulla by releasing and modifying intragranular catecholamine and neuropeptide contents.
 ...
PMID:Pituitary adenylate-cyclase activating polypeptide (PACAP) evokes long-lasting secretion and de novo biosynthesis of bovine adrenal medullary neuropeptides. 900 56

Pituitary adenylate-cyclase-activating polypeptide (PACAP) has been shown to possess mitogenic activity in various tumor cells. The present study was designed to investigate signal transduction mechanisms and expression of the proto-oncogenes c-fos and c-jun linked to the mitogenic effect of PACAP in the pancreatic carcinoma cell line AR4-2J. PACAP-(1-27)-peptide and PACAP-(1-38)-peptide, but not the structurally related vasoactive intestinal polypeptide (VIP), potently stimulated [3H]thymidine incorporation and cell number at doses of 0.1-10 nM. Both molecular forms of PACAP strongly increased formation of cAMP and inositol trisphosphate, elevated cytosolic Ca2+ levels and induced mitogen-activated protein (MAP) kinase activity. Quantitative reverse-transcription PCR revealed that PACAP-(1-27)-peptide and PACAP-(1-38)-peptide elevated c-fos mRNA levels 50-100-fold, whereas c-jun mRNA levels increased only moderately (2-3-fold). The effect of PACAP on c-fos and c-jun expression in AR4-2J cells was rapid (20 min), transient (1-2 h), dose-dependent IC50, 0.5 nM) and was abolished by the specific PACAP receptor antagonist PACAP-(6-38)-peptide or inhibitors of protein kinase C or tyrosine kinases. Compared with PACAP, epidermal growth factor and gastrin equipotently stimulated c-fos transcription whereas VIP, secretin, forskolin or phorbolester showed only marginal effects. Both PACAP (1-27)-peptide and PACAP-(1-38)-peptide strongly increased the DNA binding activity of the c-fos/ c-jun heterodimer transcription factor AP-1 at 10 nM and also stimulated AP-1 transcriptional activity up to 20-fold in AR4-2J cells. These findings indicate that the mitogenic effect of PACAP mediated via activation of the GTP-binding protein coupled PACAP/VIP-1 (PV1) receptor is linked to the MAP kinase cascade, increased expression of the proto-oncogenes c-fos and c-jun and activation of the heterodimeric transcription factor AP-1.
 ...
PMID:Pituitary adenylate-cyclase-activating polypeptide stimulates proto-oncogene expression and activates the AP-1 (c-Fos/c-Jun) transcription factor in AR4-2J pancreatic carcinoma cells. 902 70

The rat gastric GATA DNA-binding protein, GATA-6 (GATA-GT1), was stably expressed in CHO-K1 cells. The GATA-6 protein was localized in the nucleus but not in the cytoplasm. Interestingly, when cells were treated with dibutyryl cAMP, the GATA-6 protein was specifically degraded. Such a phenomenon was not observed in the presence of 5'-AMP or dibutyryl cGMP. The cellular level of the GATA-6 protein was restored upon removal of dibutyryl cAMP. Degradation was also induced by cholera toxin, which increased the cellular cAMP concentration, and was inhibited by a protein kinase A inhibitor. However, activators of protein kinase C did not have any effect. The degradation was inhibited by proteasome inhibitors (PSI (benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal) and MG115 (benzyloxycarbonyl-Leu-Leu-norvalinal)) but not by those of lysosomes and serine proteases. These results suggest that a kinase-mediated protein phosphorylation is the cellular signal for degradation of the GATA-6 protein. This finding constitutes a novel aspect of regulation by GATA DNA-binding proteins, which are essential for developmental processes and tissue-specific transcription.
 ...
PMID:Gastric GATA-6 DNA-binding protein: proteolysis induced by cAMP. 918 81

Lithium and carbamazepine (CBZ) alter levels of specific kinase-activating second messengers generated by adenylate cyclases and the phosphoinositide system. Thus, lithium and CBZ may change endogenous protein phosphorylation mediated by cyclic AMP-dependent protein kinase (PKA) and protein kinase C (PKC). The present study aimed at comparing the chronic effects of lithium and CBZ on protein phosphorylation in the rat brain by using quantitative autoradiography. Long-term treatments yielded plasma levels within the therapeutic range. In the particulate hippocampal fraction PKA-mediated phosphorylation of a 42 kDa protein and PKC-mediated phosphorylation of a 88 kDa protein were decreased after lithium treatment. In the cortical particulate fraction approximately 30% reduction in the PKA-mediated protein phosphorylation of several proteins was observed after lithium and CBZ treatments. In the same fraction, CBZ treatment significantly reduced PKC-mediated phosphorylation of several substrates by 30-40%. PKA activity was significantly reduced in cortex, but not in the hippocampus. Thus, both drugs exhibited fraction and region specificities.
 ...
PMID:Altered protein phosphorylation in the rat brain following chronic lithium and carbamazepine treatments. 921 75

1. To determine whether protein kinase C (PKC)-mediated activation of ecto-5'-nucleotidase would increase interstitial adenosine concentrations in the rat heart in vivo, we made use of the microdialysis technique and a flexibly mounted probe, which was implanted in the left ventricular myocardium and perfused with Tyrode solution. 2. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM (n = 16). Perfusion of adenosine 5'-monophosphate (AMP, 100 microM) through the probe increased the dialysate adenosine concentration markedly to 9.25 +/- 0.46 microM (n = 15). alpha, beta-Methyleneadenosine 5'-diphosphate (AOPCP, 100 microM), an inhibitor of ecto-5'-nucleotidase, abolished the AMP-induced increase in dialysate adenosine, but did not affect the baseline level of adenosine. These observations suggest that the dialysate adenosine obtained during the perfusion with AMP, but not the baseline levels of adenosine, originated from the dephosphorylation of AMP by ecto-5'-nucleotidase. Thus, the level of adenosine measured during AMP perfusion gives an index of the activity of ecto-5'-nucleotidase in the tissue. 3. Noradrenaline (10 microM) increased the adenosine concentration measured in the presence of 100 microM AMP (i.e. the activity of ecto-5'-nucleotidase) by 38.7 +/- 9.6% (n = 5, P < 0.05), an increase which was inhibited by an antagonist of the alpha 1-adrenoceptor (prazosin, 50 microM) or of PKC (chelerythrine, 10 microM). Further application of either the alpha 1-adrenoceptor agonist methoxamine (100 microM) or the diacylglycerol analogue 1,2-dioctanoyl-sn-glycerol (DOG, 100 microM) also increased the adenosine concentration by 35.1 +/- 10.0% (n = 6, P < 0.05) or 40.6 +/- 8.3% (n = 5, P < 0.05), respectively. 4. The presence of okadaic acid (50 microM), an inhibitor of protein phosphatase, enhanced the noradrenaline-induced increase in adenosine concentration by 112.4 +/- 35.9% (n = 4, P < 0.05), to a level significantly (P < 0.05) greater than the increase caused by noradrenaline alone (38.7 +/- 9.6%). 5. These data provide the first evidence that alpha 1-adrenoceptor stimulation and the subsequent activation of PKC can increase adenosine concentrations in interstitial spaces of ventricular muscle in vivo, through activation of endogenous ecto-5'-nucleotidase.
 ...
PMID:Stimulation of alpha 1-adrenoceptors and protein kinase C-mediated activation of ecto-5'-nucleotidase in rat hearts in vivo. 928 80

1. The ionotropic purinoceptors in isolated Deiters' cells of guinea-pig cochlea were characterized by use of the whole-cell variant of the patch-clamp technique. 2. Extracellular application of adenosine 5'-triphosphate (ATP) induced a dose-dependent inward current when the cells were voltage-clamped at -80 mV. The ATP-induced current showed desensitization and had a reversal potential around -4 mV. 3. Increasing intracellular free Ca2+ by decreasing the concentration of EGTA in the pipette solution reduced the amplitude of the ATP-gated current. 4. The order of agonist potency was: 2-methylthioATP (2-meSATP)>ATP>benzoylbenzoyl-ATP (BzATP)>alpha,beta-methyleneATP (alpha,beta,meATP>adenosine 5'-diphosphate (ADP)>uridine 5'-triphosphate (UTP)>adenosine 5'-monophosphate (AMP)=adenosine (Ad). 5. Pretreatment with forskolin (10 microM), 8-bromoadenosine-3',5'-cyclophosphate (8-Br-cyclic AMP, 1 mM), 3-isobutyl-1-methylxanthine (IBMX, 1 mM) or phorbol-12-myristate-13-acetate (PMA, 1 microM) reversibly reduced the ATP-induced peak current. 6. The results are consistent with molecular biological data which indicate that P2X2 purinoceptors are present in Deiters' cells. In addition, the reduction of the ATP-gated current by activators of protein kinase A and protein kinase C indicates that these P2X2 purinoceptors can be functionally modulated by receptor phosphorylation.
 ...
PMID:P2X receptors in cochlear Deiters' cells. 964 51


<< Previous 1 2 3 4 5 6 7 8 Next >>