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)

Thrombin, the key regulatory protein of hemostasis, is a potent stimulus for endothelial cell activation, a process implicated in a variety of ischemic, thrombotic, and inflammatory vascular disorders. Activation of the thrombin receptor requires a novel mechanism of receptor proteolysis generating a tethered receptor ligand. Synthetic peptides whose sequences are identical to this newly exposed receptor NH2-terminus reproduce thrombin effects on human and bovine endothelial cell activation. Receptor cleavage by catalytically active alpha-thrombin is tightly coupled to a PI-PLC, with resultant generation of IP3 and DAG, increases in [Ca2+]i, and translocation of PKC (Fig. 3). Both the increase in [Ca2+]i and PKC activation are required for thrombin-stimulated PLA2 and PLD activity, PGI2 synthesis, and barrier dysfunction, the latter occurring as the result of Ca2+ and PKC effects on specific cytoskeletal protein elements and other contractile proteins (Fig. 3). Further investigations are ongoing to identify more clearly not only the precise biochemical intermediates involved in the endothelial cell response to thrombin but also the specific protein kinase systems involved in thrombin-mediated signal transduction in vascular endothelium.
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PMID:Molecular mechanisms of thrombin-induced human and bovine endothelial cell activation. 140 26

Vinculin is a cytoskeletal protein believed to be involved in linking microfilaments to the cell membrane. It is a substrate for the Ca(2+)- and phospholipid-dependent protein kinase C. We show here that when human platelets attach and spread on a solid surface, the alpha isoforms of vinculin become phosphorylated at serine and/or threonine residues. Phosphorylation is dependent on adhesion to a surface, since suspended, unattached platelets can produce filopodia but no phosphorylation of vinculin. Phosphorylation is also dependent on actin polymerization, as it does not occur when platelets had been pretreated with cytochalasin B. Most likely, protein kinase C is responsible for the phosphorylation of vinculin, since phosphorylation also occurs when platelets are treated with a phorbol ester, which activates protein kinase C, and is blocked by treatment with a staurosporine derivative which inhibits this enzyme. These results suggest that phosphorylation plays a role in anchoring vinculin at sites of microfilament-membrane interaction.
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PMID:Phosphorylation of vinculin in human platelets spreading on a solid surface. 146 61

Cytoskeletal protein (CSP) interactions are critical to the contractile response in muscle and non-muscle cells. Current concepts suggest that activation of the contractile apparatus occurs through selective phosphorylation by specific cellular kinase systems. Because the Ca(2+)-phospholipid-dependent protein kinase C (PKC) is involved in the regulation of a number of key endothelial cell responses, the hypothesis that PKC modulates endothelial cell contraction and monolayer permeability was tested. Phorbol myristate acetate (PMA), a direct PKC activator, and alpha-thrombin, a receptor-mediated agonist known to increase endothelial cell permeability, both induced rapid, dose-dependent activation and translocation of PKC in bovine pulmonary artery endothelial cells (BPAEC), as assessed by gamma-[32P]ATP phosphorylation of H1 histone in cellular fractions. This activation was temporally associated with evidence of agonist-mediated endothelial cell contraction as demonstrated by characteristic changes in cellular morphology. Agonist-induced activation of the contractile apparatus was associated with increases in BPAEC monolayer permeability to albumin (approximately 200% increase with 10(-6) MPMA, approximately 400% increase with 10(-8) M alpha-thrombin). To more closely examine the role of PKC in activation of the contractile apparatus, PKC-mediated phosphorylation of two specific CSPs, the actin- and calmodulin-binding protein, caldesmon77, and the intermediate filament protein, vimentin, was assessed. In vitro phosphorylation of both caldesmon and vimentin was demonstrated by addition of exogenous, purified BPAEC PKC to unstimulated BPAEC homogenates, to purified bovine platelet caldesmon77, or to purified smooth muscle caldesmon150. Caldesmon77 and vimentin phosphorylation were observed in intact [32P]-labeled BPAEC monolayers stimulated with either PMA or alpha-thrombin, as detected by immunoprecipitation. In addition, BPAEC pretreatment with the PKC inhibitor, staurosporine, prevented alpha-thrombin- and PMA-induced phosphorylation of both cytoskeletal proteins, attenuated morphologic evidence of contraction, and abolished agonist-induced barrier dysfunction. These results demonstrate that agonist-stimulated PKC activity results in cytoskeletal protein phosphorylation in BPAEC monolayer, an event which occurs in concert with agonist-mediated endothelial cell contraction and resultant barrier dysfunction.
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PMID:Protein kinase C phosphorylates caldesmon77 and vimentin and enhances albumin permeability across cultured bovine pulmonary artery endothelial cell monolayers. 152 36

Thrombin, the key regulatory protein of hemostasis, has been implicated in a variety of important endothelial cell processes closely linked to endothelial signal transduction mechanisms. An initial event, following receptor binding by catalytically active alpha-thrombin, appears to be the activation of a G-protein-coupled, PI-specific PLC, with resultant generation of IP3 and DAG, with increases in [Ca2+]i, and activation and translocation of PKC (Fig. 9). PKC activation results in down-regulation of PLC, as demonstrated by inhibition of agonist-induced increases in [Ca2+]i, whereas PLA2 activity is up-regulated, with a resultant increase in endothelial PGI2 synthesis. Recently, we have demonstrated that activity of membrane-bound, endothelial PLD, is also up-regulated by PKC activation. In addition to its modulatory role in endothelial cell phospholipase activities, PKC activation appears to play a critical role in thrombin-mediated endothelial barrier dysfunction, likely via specific cytoskeletal protein phosphorylation. A temporal relationship between alpha-thrombin-mediated signal transduction and specific cellular responses, such as PGI2 synthesis and barrier dysfunction, can be established (Fig. 2). Further investigations are ongoing to identify more clearly the precise biochemical intermediates involved in the endothelial cell response to thrombin, as well as the role of differential phosphorylation by various protein kinase systems in thrombin-mediated signal transduction in vascular endothelium.
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PMID:The role of protein kinase C in alpha-thrombin-mediated endothelial cell activation. 157 13

The effect of phosphorylation on the binding of protein 4.1 to erythrocyte inside-out vesicles was investigated. Protein 4.1 was phosphorylated with casein kinase A, protein kinase C, and cAMP-dependent protein kinase. An analysis of the phosphopeptides generated by alpha-chymotryptic and tryptic digestion indicates these kinases phosphorylate similar as well as distinct domains within protein 4.1. All three enzymes catalyze the phosphorylation to varying degrees of the 46-, 16-, and 8-10-kDa fragments derived from limited chymotryptic cleavage. In addition, casein kinase A phosphorylates a 24-kDa domain, whereas protein kinase C phosphorylates a 30-kDa domain. Protein 4.1 phosphorylated by casein kinase A and protein kinase C, but not cAMP-dependent protein kinase, exhibits a reduced binding to KI-extracted inside-out vesicles. On the other hand, phosphorylation of inside-out vesicles by casein kinase A does not affect their ability to bind protein 4.1. The inside-out vesicles, however, inhibit the phosphorylation of protein 4.1 by casein kinase A and protein kinase C, but not by cAMP-dependent protein kinase. These results suggest that casein kinase A and protein kinase C may modulate the binding of protein 4.1 to the membrane by phosphorylation of specific domains of the cytoskeletal protein. Since the 30-kDa domain has been suggested as a membrane-binding site, that phosphorylation by protein kinase C reduces the binding of protein 4.1 to inside-out vesicles is perhaps not surprising. On the other hand, the role of the casein kinase A substrate 24-kDa domain in membrane binding has not been established and needs to be examined.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Modulation of protein 4.1 binding to inside-out membrane vesicles by phosphorylation. 193 75

Putative binding sites for zinc are present in the regulatory domain of protein kinase C but a distinct role for zinc has not yet been proposed. Here we show that micromolar concentrations of zinc chloride cause pure rat brain protein kinase C to localize in a detergent-insoluble, cytoskeletal fraction of red cell membranes and to bind to isolated cytoskeleton in the presence of phosphatidylserine. Attachment of protein kinase C to cytoskeleton was accompanied by enhanced expression of binding sites for 3H-phorbol ester, a regulatory ligand of protein kinase C. The active factor in the cytoskeleton was labile to protease suggesting that protein kinase C binds to a cytoskeletal protein.
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PMID:Zinc induces specific association of PKC with membrane cytoskeleton. 207 98

Protein kinase C was measured in the cytoskeletal fraction of lymphocytes, platelets and HL60 cells, by specific binding of [3H]phorbol dibutyrate and by immunoblotting with antibody to a consensus sequence in the regulatory domain of alpha-, beta- and gamma-isozymes of protein kinase C. Treatment of cells for 40 min with a combination of zinc (2-50 microM), zinc ionophore pyrithione and unlabelled phorbol dibutyrate (200 nM) caused up to a ten-fold increase in cytoskeletal protein kinase C and a corresponding decrease in other cellular compartments. Omission of any of the reagents resulted in much less or no translocation. These effects were inhibited by 1,10-phenanthroline, which chelates zinc, and were not seen with calcium. Increase in cytoskeletal protein kinase C persisted for several hours and appeared to involve attachment of the enzyme to actin microfilaments. We propose that zinc, like calcium, regulates the distribution of PKC in cells. However, unlike calcium which controls the binding of PKC to the lipid component on cell membranes, zinc controls the distribution of PKC to membrane cytoskeleton, possibly actin.
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PMID:Synergy between zinc and phorbol ester in translocation of protein kinase C to cytoskeleton. 222 43

Previous studies have shown that erythrocytes from the Milan hypertensive strain of rats (MHS) differ from erythrocytes from the control normotensive strain (MNS). These differences are determined within the stem cells, are genetically associated with the development of hypertension, and are similar to those found between the tubular cells of the two strains. Moreover they seem to be dependent upon the presence of the membrane skeleton proteins. In this paper we describe our studies aimed at identifying some precise protein difference between the membrane skeletons of the two strains, which may cause the cellular differences described above. Milan hypertensive strain and MNS rats were immunized with ghost or membrane skeleton extracts prepared from the other or their own strains. Only MHS rats immunized with MNS ghost or membrane skeleton extracts produced an antibody against a 105 KD protein in about 95% of the animals. This protein has been identified with the recently described cytoskeletal protein adducin on the following bases: the protein binds calmodulin (CaM) and protein kinase C (PKc) in a Ca2+ dependent way. It also binds phosphatidylserine, is the substrate of exogenous PKc, and finally it is purified by high salt extraction of Triton-X100 insoluble erythrocyte cytoskeletons followed by affinity chromatography on CaM-sepharose. Using this antibody the isolation from a mouse spleen library, the characterization and sequencing of a partial cDNA clone coding for this protein has been carried out. In conclusion adducin may be considered a very useful tool to test the hypothesis that the cellular differences between MHS and MNS may be caused by a difference in a membrane skeleton protein.
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PMID:Erythrocyte adducin differential properties in the normotensive and hypertensive rats of the Milan strain. Characterization of spleen adducin m-RNA. 270 90

In this paper we discuss recent experimental results pertinent to three unresolved issues regarding the long-term potentiation (LTP) effect: the nature of its enduring substrates, the biochemical mechanisms that produce it, and its potential role in memory. LTP appears to be triggered by a postsynaptic influx of calcium and is associated with alterations in the shape of dendritic spines and probably the formation of new synapses. We discuss the possibility that morphological reorganization also modifies membrane surface chemistry of synaptic elements. Evidence is presented that LTP is not associated with changes in presynaptic calcium currents. Activation of protein kinase C is shown to be insufficient for the induction of LTP, although it may play a modulatory role. The hypothesis that activation of a calcium-sensitive protease (calpain) is pivotal to the establishment of LTP is supported by experiments showing that a calpain inhibitor, leupeptin, blocks LTP. Furthermore, activation of NMDA receptors, an event implicated in LTP induction, is accompanied by calcium-sensitive proteolysis of spectrin, a major dendritic cytoskeletal protein. The finding that stimulation patterns designed to mimic naturally-occurring cell discharge patterns are highly effective for LTP induction greatly strengthens the hypothesis that LTP actually occurs during the encoding of information in cortical systems. Potential contributions of LTP to learning are explored using computer simulations of a simple cortical network.
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PMID:Long-term potentiation: persisting problems and recent results. 285 Aug 41

Stimulation of intact human neutrophils with phorbol 12-myristate 13-acetate results in the selective phosphorylation of two cytoskeletal protein components with molecular masses of 20 and 48 kDa. After phosphorylation the 48-kDa protein is no longer recovered as a component of the cytoskeletal fraction but is present as a fully soluble phosphoprotein. Phosphorylation of the 20-kDa protein (probably myosin light chains) signals a proteolytic conversion, catalyzed by calpain, to a smaller species having a molecular mass of approximately 15 kDa. Phosphorylation of both the 48- and 20-kDa proteins is related to the conversion of protein kinase C, also catalyzed by calpain, to the soluble fully active form. Leupeptin, an inhibitor of calpain, blocks both the phosphorylation of the target proteins and the proteolytic modification of the 20-kDa polypeptide. Thus, phosphorylation of cytoskeletal proteins and signal-directed proteolysis appear to be related processes that follow stimulation of human neutrophils by phorbol esters. The resulting changes in cytoskeletal organization may be involved in the expression of some neutrophil functions, such as exocytosis of specific granules.
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PMID:Phosphorylation and proteolytic modification of specific cytoskeletal proteins in human neutrophils stimulated by phorbol 12-myristate 13-acetate. 347 71


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