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)

Experiments were conducted to characterize the effects of amiloride on the regulatory mechanisms of vascular smooth muscle contraction. Intact, saponin-skinned and A23187-treated strips of rabbit aorta were used for these studies. Amiloride significantly (P less than 0.05) reduced the norepinephrine bitartrate (NE)-stimulated increase in intracellular Ca2+ in intact arteries. In saponin-skinned arteries, amiloride depressed both stress and concomitant levels of myosin light chain phosphorylation. This inhibition of stress appeared to be competitive with MgATP. In A23187-treated preparations, where the effects of amiloride were studied at physiological [MgATP] in the absence of functional membrane Ca2+-channels, amiloride caused a reduction in both stress and myosin light chain phosphorylation. In other experiments on intact arteries, the contractile response to phorbol 12,13-dibutyrate, an activator of protein kinase C, was reduced by amiloride. We conclude that the vasorelaxant effects of amiloride are mediated via inhibition of myosin light chain kinase and protein kinase C, in addition to the inhibition of Ca2+ influx.
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PMID:Effect of amiloride on regulatory mechanisms of vascular smooth muscle contraction. 244 93

Fluoride interacts with G proteins and, consequently, stimulates phospholipase C as measured by the formation of inositol phosphates and phosphatidic acid. In human platelets this paralleled platelet aggregation and the activation of phosphorylation of substrates of protein kinase C (47kDa protein) and myosin light chain kinase (20kDa protein). Phospholipase C activation by fluoride was inhibited by dibutyryl cyclic AMP and by agents that increase cyclic AMP levels such as iloprost and forskolin. This information suggest that cyclic AMP affects the G protein associated with the stimulation of phospholipase C.
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PMID:Activation of platelet phospholipase C by fluoride is inhibited by elevation of cyclic AMP. 246 3

IgE-mediated stimulation of rat basophilic leukemia (RBL-2H3) cells results in the secretion of histamine. Myosin immunoprecipitated from these cells shows an increase in the amount of radioactive phosphate incorporated into its heavy (200 kDa) and light (20 kDa) chains. In unstimulated cells two-dimensional mapping of tryptic peptides of the myosin light chain reveals one phosphopeptide containing the serine residue phosphorylated by myosin light chain kinase. Following stimulation a second phosphopeptide appears containing a serine residue phosphorylated by protein kinase C. Tryptic phosphopeptide maps derived from myosin heavy chains show that unstimulated cells contain three major phosphopeptides. Following stimulation a new tryptic phosphopeptide appears containing a serine site phosphorylated by protein kinase C. The stoichiometry of phosphorylation of the myosin light and heavy chains was determined before and after antigenic stimulation. Before stimulation, myosin light chains contained 0.4 mol of phosphate/mol of light chain all confined to a serine not phosphorylated by protein kinase C. Cells that secreted 44% of their total histamine in 10 min exhibited an increase in phosphate content at sites phosphorylated by protein kinase C from 0 mol of phosphate/mol of myosin subunit to 0.7 mol of phosphate/mol of light chain and to 1 mol of phosphate/mol of heavy chain. When RBL-2H3 cells were made permeable with streptolysin O they still showed a qualitatively similar pattern of secretion and phosphorylation. Our results show that the time course of histamine secretion from stimulated RBL-2H3 cells parallels that of myosin heavy and light chain phosphorylation by protein kinase C.
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PMID:Antigen-induced secretion of histamine and the phosphorylation of myosin by protein kinase C in rat basophilic leukemia cells. 247 73

We investigated the role of microfilaments in stimulus-induced translocation of protein kinase C (PKC) in polymorphonuclear leukocytes (PMNs) from C57BL/6 mice. Cytochalasin B and dihydrocytochalasin B almost completely inhibited PKC translocation induced by either TPA or Ca2+ ionophore after pretreatment of cells for 30 min. In addition, ML-9, a potent inhibitor of Ca2+/calmodulin-dependent myosin light chain kinase which regulate microfilament contraction, and a calmodulin antagonist W-7, also inhibited PKC translocation. These findings suggest the possibility that microfilaments are involved in the translocation of PKC.
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PMID:Possible involvement of microfilaments in protein kinase C translocation. 249 32

The Nitella-based in vitro motility assay developed by Sheetz and Spudich (Sheetz, M.P., and Spudich, J. A. (1983) Nature 303, 31-35) is a quantitative assay for measuring the velocity of myosin-coated beads over an organized substratum of actin. We have used this assay to analyze the effect of phosphorylation of various sites on the 20,000-Da light chain of smooth muscle and cytoplasmic myosins. Phosphorylation by myosin light chain kinase at serine 19 on the 20,000-Da light chain subunit of smooth muscle myosin from turkey gizzard, bovine trachea and aorta, and of cytoplasmic myosin from human platelets was required for bead movement. The individual phosphorylated myosin-coated beads moved at characteristic rates under the same conditions (turkey gizzard myosin, 0.2 micron/s; aorta or trachea myosin, 0.12 micron/s; and platelet myosin, 0.04 micron/s; in contrast, rabbit skeletal muscle myosin, 2 micron/s). Myosin light chain kinase can also phosphorylate threonine 18 in addition to serine 19, and this phosphorylation resulted in an increase in the actin-activated MgATPase activity (Ikebe, M., and Hartshorne, D.J. (1985) J. Biol. Chem. 260, 10027-10031). Phosphorylation at this site had no effect on the velocity of smooth muscle myosin-coated beads. Protein kinase C (Ca2+/phospholipid-dependent enzyme) can also phosphorylate two to three sites on the 20,000-Da light chain, and this phosphorylation alone did not result in the movement of myosin-coated beads. When myosin that had been previously phosphorylated by myosin light chain kinase at serine 19 was also phosphorylated by protein kinase C, myosin-coated beads moved at the same velocity as beads coated with myosin phosphorylated by myosin light chain kinase alone. Tropomyosin binding to actin also had an activating effect on the actin-activated MgATPase activity through an effect on the Vmax and also resulted in an increase in the velocity of myosin-coated beads.
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PMID:Effect of multiple phosphorylations of smooth muscle and cytoplasmic myosins on movement in an in vitro motility assay. 252 81

We have examined the effect of protein kinase C phosphorylation on the actin-activated ATPase activity and filament stability of calf thymus myosin. Protein kinase C phosphorylated thymus myosin regulatory light chains, LC20, on two sites which are different from the site phosphorylated by myosin light chain kinase. The light meromyosin part of the thymus myosin heavy chain was also phosphorylated by protein kinase C, but at a rate about 10% that of LC20. Under conditions where both unphosphorylated thymus and myosin light chain kinase-phosphorylated thymus myosin were filamentous and under conditions where myosin light chain kinase phosphorylation induces myosin filament formation, protein kinase C phosphorylation had little effect on the actin-activated ATPase activity or filament stability of unphosphorylated or myosin light chain kinase-phosphorylated myosin. In contrast, protein kinase C phosphorylation has been reported to inhibit the actin-activated ATPase activity of gizzard myosin.
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PMID:Protein kinase C phosphorylation of thymus myosin. 253 57

The mechanism of vasodilator-induced inhibition of platelet aggregation was investigated in human platelets. Cyclic nucleotide-elevating vasodilators stimulated cAMP- or cGMP-dependent protein phosphorylation, inhibited the activation of both protein kinase C and myosin light chain kinase, and inhibited the thrombin-induced hydrolysis of phosphatidylinositol-4,5-bisphosphate without affecting its resynthesis. The results suggest that cAMP- and cGMP-elevating vasodilators both inhibit platelet aggregation at an early step of the activation cascade, presumably at the level of phospholipase C.
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PMID:Cyclic nucleotide elevating vasodilators inhibit platelet aggregation at an early step of the activation cascade. 253 41

Two types of myosin light chain phosphatase from aortic smooth muscle extract were separated by chromatography on heparin-agarose. The phosphatase which appeared in the flow-through fractions had low activity on actomyosin, its apparent molecular mass was 260 kDa and upon ethanol treatment it generated a catalytic subunit with an apparent molecular mass of 36-39 kDa as determined by gel filtration. This phosphatase preferentially dephosphorylated the alpha-subunit of phosphorylase kinase and its phosphorylase phosphatase activity was not inhibited by heparin, inhibitor-1 or inhibitor-2. The phosphatase retained by heparin-agarose had high activity on actomyosin, its apparent molecular mass was 150 kDa and upon ethanol treatment it generated a catalytic subunit with an apparent molecular mass of 39-42 kDa. It preferentially dephosphorylated the beta-subunit of phosphorylase kinase and its phosphorylase phosphatase activity was not inhibited by heparin, inhibitor-1 or inhibitor-2. Myosin light chain was phosphorylated by myosin light chain kinase in peptides AB (Ser-P) and CD (Thr-P), and/or by protein kinase C in peptides E (Ser-P) and F (Thr-P) as determined by one-dimensional phosphopeptide mapping. The catalytic subunit of heparin-agarose flow-through phosphatase preferentially dephosphorylated peptide F over peptides AB, CD and E in both isolated light chain and actomyosin. The catalytic subunit of heparin-agarose bound phosphatase could effectively dephosphorylate all sites in isolated light chain, whereas it was less effective on dephosphorylation of peptide E in actomyosin.
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PMID:Dephosphorylation of distinct sites in myosin light chain by two types of phosphatase in aortic smooth muscle. 253 49

The effects of prostaglandin (PG) F2 alpha and PGB2 on isolated rat aortic strips were studied in calcium-free 1 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid buffer to explore the mechanisms of PG-induced smooth muscle contraction. In the absence of extracellular calcium, PGF2 alpha and PGB2 induced sustained contractions that were similar to those induced by activators of protein kinase C (PKC) or norepinephrine. These sustained contractions were apparently induced via a pharmacomechanical coupling mechanism because they could be elicited repeatedly in the absence of extracellular calcium and were not affected by changes in buffer concentrations of potassium, magnesium or phosphate. They depended on intracellular but not extracellular calcium because they were reversed by nitroprusside but not by nifedipine, verapamil or diltiazem. Contractions induced by combining either PG with 12-O-tetradecanoyl-phorbol-13-acetate or mezerein were consistent with the suggestion that PG-induced contractions were induced via a PKC-dependent mechanism. Moreover, both PGF2 alpha- and PGB2-induced contractions were inhibited noncompetitively by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine at concentrations known to inhibit PKC but not myosin light chain kinase. These data, combined with those published from other laboratories, suggest that PGF2 alpha and PGB2 induce contraction of the rat aorta, at least in part, by activating PKC. However, PG-induced contractions did not require enhanced phosphoinositide hydrolysis and apparently did not involve the mobilization of intracellular calcium by inositol 1,4,5-trisphosphate. The data thus suggest that PGs activate PKC via a novel mechanism.
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PMID:Evidence that prostaglandins can contract the rat aorta via a novel protein kinase C-dependent mechanism. 254 67

A number of different protein kinases phosphorylate purified heavy chains or the 20-kDa light chain of smooth muscle myosin. The physiological significance of these phosphorylation reactions has been examined in intact smooth muscle. Myosin heavy chain was slightly phosphorylated (0.08 mol of phosphate/mol) under control conditions in bovine tracheal tissue. Treatment with carbachol, isoproterenol, or phorbol 12,13-dibutyrate resulted in no significant change. In contrast, heavy chain was phosphorylated to 0.30 mol of phosphate/mol of heavy chain in tracheal smooth muscle cells in culture. This value increased significantly with ionomycin treatment. In control tissues, 9% of the light chain was monophosphorylated with 32P in the serine site phosphorylated by myosin light chain kinase. Carbachol (0.1 microM) alone resulted in contraction and 42% monophosphorylated light chain with 32P only in the serine site phosphorylated by myosin light chain kinase. Similarly, stimulation with histamine, 5-hydroxytryptamine, or KCl resulted in 32P incorporation into only the myosin light chain kinase serine site. Phorbol 12,13-dibutyrate (1 microM) alone resulted in 22% monophosphorylated light chain. However, only 25% of the 32P was in the myosin light chain kinase serine site, whereas 75% was in a serine site phosphorylated by protein kinase C. Phorbol 12,13-dibutyrate plus carbachol resulted in 27% monophosphorylated light chain; 75% of the 32P was in the myosin light chain kinase serine site, with the remainder in the protein kinase C serine site. These results indicate that phorbol esters act to increase phosphorylation of myosin light chain by protein kinase C. However, receptor-mediated stimulation or depolarization leading to tracheal smooth muscle contraction results in phosphorylation of myosin light chain by myosin light chain kinase alone.
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PMID:Phosphorylation of smooth muscle myosin heavy and light chains. Effects of phorbol dibutyrate and agonists. 259 71


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