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 phosphorylation of the alpha-subunit of Na+/K(+)-transporting ATPase (Na,K-ATPase) by cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) was characterized in purified enzyme preparations of Bufo marinus kidney and duck salt gland and in microsomes of Xenopus oocytes. In addition, we have examined cAMP and phorbol esters, which are stimulators of PKA and PKC, respectively, for their ability to provoke the phosphorylation of alpha-subunits of Na,K-ATPase in homogenates of Xenopus oocytes. In the enzyme from the duct salt gland, phosphorylation by PKA and PKC occurs on serine and threonine residues, whereas in the enzyme from B. marinus kidney and Xenopus oocytes, phosphorylation by PKA occurs only on serine residues. Phosphopeptide analysis indicates that a site phosphorylated by PKA resides in a 12-kDa fragment comprising the C terminus of the polypeptide. Studies of phosphorylation performed on homogenates of Xenopus oocytes show that not only endogenous oocyte Na,K-ATPase but also exogenous Xenopus Na,K-ATPase expressed in the oocyte by microinjection of cRNA can be phosphorylated in response to stimulation of oocyte PKA and PKC. In conclusion, these data are consistent with the possibility that the alpha-subunit of Na,K-ATPase can serve as a substrate for PKA and PKC in vivo.
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PMID:Phosphorylation of Na,K-ATPase alpha-subunits in microsomes and in homogenates of Xenopus oocytes resulting from the stimulation of protein kinase A and protein kinase C. 133 Oct 53

Although abnormalities in cellular ion transport have been shown in a variety of cells of essential hypertensives, the mechanistic link between these abnormalities and elevated blood pressure is poorly understood. Reduced sodium-potassium ATPase activity, with and without elevated levels of a circulating inhibitor of this transport system, has been reported by a number of studies. The recent characterization of the endogenous ouabain or its isomer will facilitate the testing of the hypothesis that salt-sensitive essential hypertension relates to higher levels of this factor. The erythrocyte sodium-lithium countertransport may serve as a marker for a subpopulation of essential hypertensives. However, this transport system has no physiologic counterpart and thus does not provide insight into mechanisms associated with altered cellular ionic homeostasis in essential hypertension. Increased activity of the sodium-hydrogen antiport in essential hypertension relates to an alkaline shift in the cytosolic pH set-point for activation of this transport system. This process may reflect increased cytosolic free calcium concentration with or without augmented protein kinase C activity.
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PMID:Defects in membrane transport of ions as possible pathogenic factors in hypertension. 136 33

The light-activated protein kinase C inhibitor, calphostin C, is shown to inhibit the ability of IL-3-dependent 32D cells to reduce the tetrazolium salt, MTT. To determine whether this inhibition was mediated through mitochondria which have been implicated in MTT reduction, isolated mitochondria were treated with calphostin C in the presence of various substrates for mitochondrial electron transport and EDTA (to exclude PKC involvement). Calphostin C extensively inhibited succinate-dependent MTT reduction (IC50 = 110nM) but had little effect on either NADH- or NADPH-dependent MTT reduction. An alternative protein kinase C inhibitor, H7, did not affect succinate-dependent mitochondrial MTT reduction, and the protein kinase A inhibitor, KT5720, had little effect on either cellular or mitochondrial MTT reduction. These results show that in addition to its role as a PKC inhibitor, calphostin C is also a potent inhibitor of succinate-dependent mitochondrial electron transport.
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PMID:The protein kinase C inhibitor, calphostin C, inhibits succinate-dependent mitochondrial reduction of MTT by a mechanism that does not involve protein kinase C. 137 66

Several lines of evidence indicate that phosphorylation of the 25 kDa mRNA cap binding protein (eIF-4E) stimulates the efficiency of translational initiation. While the protein kinases which catalyze this reaction in intact cells have not been completely identified, evidence suggests that protein kinase C phosphorylates serine residues of eIF-4E in intact cells. In this study we demonstrate that protein kinase C also phosphorylates threonine residues of recombinant human eIF-4E in vitro. Phosphorylation of threonine and serine was observed over a range of eIF-4E and salt concentrations. However, relatively low levels of phosphorylation were seen even under optimal conditions. Similar results were observed with native eIF-4E purified from human erythrocytes. These findings demonstrate that protein kinase C can phosphorylate both serine and threonine residues of eIF-4E in vitro, but suggest that protein kinase C may not be the primary enzyme that phosphorylates eIF-4E in vivo.
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PMID:Protein kinase C phosphorylates both serine and threonine residues of the mRNA cap binding protein eIF-4E. 140 50

Angiotensin II-induced phosphorylation of proteins was examined in isolated myocytes from hearts of Dahl rats. A high salt diet induced cardiac hypertrophy in Dahl salt-sensitive rats. Angiotensin II-induced phosphorylation of a 42-kd protein (pp42) was detected by two-dimensional electrophoresis in hypertrophic but not normal ventricular myocytes. Angiotensin II stimulation was time-dependent, with a peak effect at 30 minutes. The half-maximal and maximal concentrations of angiotensin II that stimulated pp42 phosphorylation were 1 and 10 nM, respectively. Phosphorylation of pp42 was a function of cardiac hypertrophy. Phorbol 12-myristate 13-acetate-induced phosphorylation of pp42 indicates the possibility of an association between protein kinase C and the signal transduction pathway of angiotensin II-induced pp42 phosphorylation. Ionomycin and A23187 (both at 1 microM) did not stimulate phosphorylation of pp42. Angiotensin II produced a small increase in the synthesis of myocyte proteins in both normal and hypertrophic cells as shown by [35S]methionine incorporation. However, this increase could not account for the increase in the phosphate content of pp42. This protein was not an isoform of actin nor was it of platelet origin. These results raise the possibility that angiotensin II may play a role in the activation of factors in hypertrophic myocytes; however, further study is required to define a link between phosphorylation of pp42 and the hypertrophic process.
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PMID:Angiotensin II-induced protein phosphorylation in the hypertrophic heart of the Dahl rat. 142 15

To clarify the requirement of the association of substrate proteins with phospholipid membranes for phosphorylation by protein kinase C (PKC), we studied the relationship between membrane association of PKC-substrate proteins and their phosphorylation by PKC. In the presence of phosphatidylserine, 12-O-tetradecanoylphorbol-13-acetate induced PKC autophosphorylation in either the presence or the absence of Ca2+, and this phosphorylation was not inhibited by increasing salt concentration (up to 200 mM NaCl). Thus, Ca2+ and ionic strength did not markedly affect the enzymatic activity of PKC. Annexin I required Ca2+ for both its association with phospholipid membranes and phosphorylation by PKC, whereas histone and monomyristilated lysozyme (C14:0-lysozyme) did not. This result indicates that the membrane association of substrates closely correlates with their phosphorylation by PKC. Similar correlation was also observed in the effects of ionic strength on the membrane association of the substrates and their phosphorylation by PKC; increased ionic strength (200 mM NaCl) remarkably inhibited both the membrane association and the phosphorylation of histone and annexin I by PKC but C14:0-lysozyme was not markedly affected. These results suggest that the membrane association of PKC-substrate proteins is a prerequisite for their phosphorylation by PKC. This concept further conforms to the mechanisms of PKC inhibitors; some types of PKC inhibitors are mediated all or in part through inhibition of the substrate-membrane interaction.
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PMID:Requirement of protein association with membranes for phosphorylation by protein kinase C. 153 81

Protein kinase C-zeta (PKC-zeta) is a member of the protein kinase C gene family which using in vitro preparations has been described as being resistant to activation by phorbol esters. PKC-zeta was found to be expressed in several cell types as an 80-kDa protein. In vitro translation of a full-length PKC-zeta construct also yielded as a primary translation product an 80-kDa protein. In the U937 cell, PKC-zeta was slightly more abundant in the cytosol than in the particulate fraction. Acute exposure of U937 cells to tetradecanoyl-phorbol-13-acetate (TPA), phorbol dibutyrate, mezerin, or diacylglycerol derivatives did not induce translocation of this isoform to the particulate fraction. Chronic exposure to 1 microM TPA failed to translocate or down-regulate PKC-zeta in U937, HL-60, COS, or HeLa-fibroblast fusion cells. To examine whether PKC-zeta was activated by TPA, PKC activity was evaluated in COS cells transiently over-expressing this isoform. In non-transfected cells, two peaks of phospholipid- and TPA-dependent kinase activity were observed. Eluting at a lower salt concentration was a peak of activity associated with PKC-alpha. PKC-zeta eluted with the second peak of activity and at a higher salt concentration. In transfected cells which expressed PKC-zeta at 4-10-fold over endogenous levels, there was only a slight increase in activity associated with the second peak. The activity and quantity of PKC-zeta did not strictly correlate. Treatment with TPA under conditions that did not alter PKC-zeta content abolished detection of the second peak of PKC activity eluting from the Mono Q column. Thus, PKC-zeta does not translocate or down-regulate in response to phorbol esters or diacylglycerol derivatives. However, for reasons discussed these studies do not resolve the issue of whether this isoform is activated by TPA.
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PMID:Effect of phorbol esters on protein kinase C-zeta. 153 59

Recruitment of inflammatory cells to the lung capillaries has been proposed as an important step in the sequence of events that lead to acute lung injury. Frequently, in the clinical setting, bacteremia and sepsis syndrome precede the acute lung failure and endotoxin priming may represent a comparable paradigm, useful for experimental pursuit. Following addition of the chemotactic tripeptide FMLP (10(-9) to 10(-6) M) to the cell-free, salt solution perfusate of isolated rat lungs, only a small degree of vasoconstriction was observed. However, in lungs isolated from rats that received 2 mg/kg intraperitoneal Salmonella enteritidis endotoxin 2 h before lung perfusion, FMLP dose dependently caused a large, transient pulmonary pressor response, edema formation, and release of large amounts of thromboxane and leukotriene B4. Since in vitro priming with endotoxin, direct vascular injury by neutrophil elastase, nor direct stimulation with FMLP of pulmonary artery rings from endotoxin-pretreated rats, mimicked the effects of in vivo endotoxin priming, we conclude that the presence of inflammatory cells in the lung capillaries accounted for the large amount of eicosanoids produced by the lungs after FMLP stimulation. In fact, by retrograde lavage of the lung circulation with a collagenase solution, previously adherent cell clumps were mobilized and identified. These cell clumps, composed of red blood cells, neutrophils, and platelets, were not seen in the vascular lavage sediment obtained from unprimed control lungs. Indomethacin, a thromboxane antagonist, AA861, a 5-lipoxygenase inhibitor, and WEB 2086, a platelet-activating factor (PAF) antagonist, reduced the thromboxane synthesis and release after FMLP (10(-7) M) in in vivo endotoxin-primed lungs. None of the inhibitors employed exclusively inhibited only one particular eicosanoid mediator but rather affected the release of several mediators, suggesting a close link between the different synthetic arachidonic acid pathways. An inhibitor of phospholipase C (2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate), NCDC, but not an inhibitor of phospholipase D (Wortmannin) or of protein kinase C (staurosporine) inhibited the FMLP-stimulated pulmonary pressure rise and eicosanoid release in endotoxin-primed lungs in vivo. Our data suggest that eicosanoids (in particular thromboxane) released from cells trapped in the lung circulation, but not from constitutive lung cells, contribute to vasoconstriction and edema formation caused by the chemoattractant FMLP in endotoxin-primed lungs.
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PMID:FMLP causes eicosanoid-dependent vasoconstriction and edema in lungs from endotoxin-primed rats. 154 53

Porcine carotid arterial muscles were 32P-labeled then contracted with 8 microM phorbol dibutyrate (PDBu) in normal physiological salt solution (PSS) and in Ca(2+)-free PSS containing 0.5 mM ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetate. Significant incorporation of [32P]phosphate into the 20-kDa myosin light chain, a 28-kDa protein, desmin and caldesmon was measured with no apparent difference between normal and Ca(2+)-depleted muscles. Ca-determination showed that the Ca(2+)-depleted muscle contained 15% of the total Ca of the normal muscle. However, determination of the actin-bound Ca revealed that all the Ca in the Ca(2+)-depleted muscle could be accounted for by its actin-bound Ca. Accordingly, protein phosphorylation during the slow PDBu-induced contraction may proceed in the virtual absence of free Ca2+. Phosphopeptide mapping of the myosin light chain isolated from muscles contracted with PDBu either in the presence or absence of Ca2+ showed that two-thirds of the incorporated [32P]phosphate was attributable to myosin light chain kinase catalyzed phosphorylation and one-third was due to phosphorylation by protein kinase C. PDBu increased the phosphorylation of the 28-kDa protein, desmin and caldesmon two- to threefold, as compared with that in muscles contracted by KCl depolarization or by the receptor mediated agonists norepinephrine and histamine. Muscles contracted by high concentration of PDBu in the presence or absence of Ca2+ could be fully relaxed and recontracted.
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PMID:Protein phosphorylation in arterial muscle contracted by high concentration of phorbol dibutyrate in the presence and absence of Ca2+. 155 47

A monoclonal antibody was made using the spleen cells of a mouse immunized with chick synaptic membranes and designated as mAb 1D12. It immunoprecipitated 25% of the omega-conotoxin binding protein but no dihydropyridine binding protein solubilized from chick brain membranes. By immunoblotting, a polypeptide of 58-kDa was identified as the antigen of this antibody in chick, rat, rabbit and guinea pig brain. Immunohistochemical observation indicated the immunoreactivity of mAb 1D12 to be localized in the synaptic regions of central and peripheral neurons. In peripheral organs, there was additional staining in the distal portions of nerve fibers. Immunoelectron microscopy showed immunoreactivity to be located in synaptic vesicle and presynaptic plasma membranes. In the subcellular fractionation of rat brain, 58-kDa protein was recovered in the fractions of synaptic vesicles and plasma membranes but not soluble proteins. This protein could be extracted from membranes by Triton X-100 but treatment with EDTA, acid, base or high salt failed to have such effect. Solubilized 58-kDa protein of rat brain was purified by immunoaffinity chromatography using mAb 1D12. Both protein kinase C and Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) phosphorylated purified 58-kDa protein, and maxima of 0.47 and 0.94 mol of phosphates, respectively, were incorporated per mol of 58-kDa protein. 58-kDa protein was not phosphorylated by either cAMP-dependent or cGMP-dependent protein kinase. When present in membranes, it was also phosphorylated by protein kinase C and CaM kinase II. Possible involvement of 58-kDa protein in the protein kinase C and CaM kinase II-mediated regulation of synaptic transmission in central and peripheral neurons is discussed.
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PMID:Protein kinase C and Ca2+/calmodulin-dependent protein kinase II phosphorylate a novel 58-kDa protein in synaptic vesicles. 165 60


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