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)

Endothelin-1 contracts porcine carotid arterial smooth muscle with an ED50 of 10 nM. Contraction is associated with phosphorylation of the 20,000 dalton-regulatory light chain subunits of vascular myosin. Phosphopeptide mapping of light chains isolated from 32PO4-loaded muscle strips stimulated by endothelin-1 (5 x 10(-8) M) and comparison with maps generated from light chains phosphorylated in vitro or muscles stimulated with KCl (110 mM) or angiotensin-II (5 x 10(-8) M) indicates that Ca2(+)-calmodulin activation of myosin light chain kinase is a biochemical pathway stimulated by all three agonists. However, a small amount of phosphate (17%) was detected in a light chain peptide phosphorylated by protein kinase C. Endothelin-1 also stimulated phosphorylation of the thin filament protein, caldesmon, (from 0.35 mol PO4/mol caldesmon to 0.52 mol PO4/mol). Collectively, these results provide evidence that the effects of endothelin-1 on force generation and maintenance in vascular muscle may be dependent upon myosin light chain phosphorylation by Ca2+ calmodulin--requiring myosin light chain kinase and upon a thin filament mechanism that is modulated by phosphorylation of caldesmon.
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PMID:Myosin light chain and caldesmon phosphorylation in arterial muscle stimulated with endothelin-1. 228 Apr 12

The phosphorylation of caldesmon was studied to determine if kinase activity reflected either an endogenous kinase or caldesmon itself. Titration of kinase activity with calmodulin yielded maximum activity at substoichiometric ratios of calmodulin/caldesmon. The sites of phosphorylation on caldesmon for calcium/calmodulin-dependent protein kinase II and endogenous kinase were the same, but distinct from protein kinase C sites. Phosphorylation in the presence of Ca2+ and calmodulin resulted in a subsequent increase of endogenous kinase activity in the absence of Ca2+. These results suggest that caldesmon is not a protein kinase and that kinase activity in caldesmon preparations is due to calcium/calmodulin-dependent protein kinase II.
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PMID:Phosphorylation of caldesmon. 255 23

We have isolated caldesmon (Mr = 145,000), by immunoprecipitation, from [32P]orthophosphate-loaded porcine carotid arteries. In resting muscles, caldesmon was phosphorylated to 0.45 mol of PO4/mol protein, while the 20,000-dalton myosin regulatory light chain (LC20) was phosphorylated to less than 0.05 mol/mol. After stimulation by KCl (110 mM) for 75 min and phorbol 12,13-dibutyrate (PDBu, 1 microM) for 60 min, caldesmon phosphorylation levels rose to 0.96 and 1.1 mol/mol, respectively. LC20 phosphorylation increased to 0.49 mol/mol at 1 min of stimulation by KCl and decreased to 0.17 mol/mol at 60 min. With PDBu, phosphate incorporation into LC20 rose only slightly, reaching 0.09 mol/mol after 90 min. Muscles contracted with histamine (10 microM) or ouabain (1 microM) also demonstrated elevated levels of phosphate incorporation into caldesmon. In these muscles, LC20 phosphorylation levels were less than 0.05 mol/mol. Three major phosphopeptides of indistinguishable mobility were identified on maps of caldesmon from resting, KCl-stimulated, and PDBu-stimulated muscles. There was, however, little similarity between the phosphopeptide maps of caldesmon phosphorylated in intact tissue and maps of purified caldesmon phosphorylated in vitro by protein kinase C (Ca2+/phospholipid-dependent enzyme) or Ca2+/calmodulin kinase II.
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PMID:Phosphorylation of caldesmon in arterial smooth muscle. 270 86

Calcium initiates smooth muscle contraction by binding to calmodulin and activating the enzyme myosin light chain kinase. The activated form of myosin light chain kinase phosphorylates myosin on the 20,000-dalton light chain and contractile activity ensues. Calcium may also enhance smooth muscle contractile activity by binding directly to myosin, the main component of the thick filament. Recent studies raise the possibility that the calcium-calmodulin complex may also modulate smooth muscle contractile activity by removing the inhibition imposed by caldesmon, a protein that is bound to the thin (i.e., actin-containing) filaments of smooth muscle. In vitro studies have demonstrated that the calcium-activated, phospholipid-dependent kinase, protein kinase C, can phosphorylate smooth muscle myosin at a different site than does myosin light chain kinase and down-regulate its actin-activated magnesium adenosine triphosphatase activity. This raises the possibility that protein kinase C phosphorylation of myosin may play a role in modulating vascular contractile activity in vivo.
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PMID:Effects of calcium on vascular smooth muscle contraction. 302 18

The cellular and molecular mechanisms underlying smooth muscle contraction are reviewed in the light of recent studies of smooth muscle ultrastructure and of the role of polyphosphoinositide turnover and protein kinase C function in smooth muscle contraction. A new model of smooth muscle contraction is proposed that differs radically from accepted views, particularly the latch bridge hypothesis, in terms of both Ca2+ messenger function and the molecular events underlying this process. A coordinate fibrillar domain model of contraction is proposed in which the initial and sustained phases of contraction are mediated by different cellular and molecular events. The initial phase of response is mediated by a rise in [Ca2+]c and the resulting calmodulin-dependent activation of both myosin light chain kinase and the dissociation of caldesmon from the actin-caldesmon-tropomyosin-myosin fibrillar domain. These events lead to an interaction between actin and the phosphorylated light chains of myosin just as in previous models. However, this initial phase is followed by a sustained phase in which a rise in [Ca2+]sm stimulates the plasma membrane-associated, Ca2+-sensitive form of protein kinase C that results in the phosphorylation of both structural and regulatory components of the filamin-actin-desmin fibrillar domain. These events underlie the tonic phase of contraction.
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PMID:Protein kinase C in the regulation of smooth muscle contraction. 304 May 4

The effects of a protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), and of a calmodulin antagonist calmidazolium (CZ), on a human colonic cancer cell line HT-29 were analyzed. HT-29 cells are undifferentiated in standard culture conditions (HT-29 G+) and display an enterocytic differentiation when cultured in glucose-deprived medium (HT-29 G-). Early effects of TPA and CZ on the localization of cytoskeletal proteins (caldesmon, alpha-actinin and vinculin) and on cell proliferation were examined. Differentiation of the cells was assessed after 4 weeks on the basis of ultrastructural and functional characteristics of enterocytic polarity, presence of apical brush borders, expression of brush border membrane antigens (Caco 5/50 and sucrase-isomaltase), and segregation of calmodulin to the brush border cytoskeleton. TPA treatment of HT-29 G+ or G- cells induced early morphological and cytoskeletal alterations: the cells rounded up and lost their stress fibers with the associated caldesmon, alpha-actinin, and vinculin. TPA did not modify the differentiation of G- cells, but induced in G+ cells the expression, although limited, of enterocytic differentiation characteristics. Addition of CZ to HT-29 G- cells enhanced their differentiation state but did not provoke any early morphological or cytoskeletal alterations. No effects of CZ on HT-29 G+ cells were obvious. The results suggest that protein kinase C, the TPA receptor, is involved in the triggering of HT-29 G+ cell differentiation whereas calmodulin-dependent functions would be implicated in HT-29 G- cell maturation.
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PMID:Modulation of HT-29 human colonic cancer cell differentiation with calmidazolium and 12-O-tetradecanoylphorbol-13-acetate. 304 55

Caldesmon is a widely distributed calmodulin- and actin-binding protein which occurs in different forms depending on the tissue or cell type under examination. On the basis of molecular weight, caldesmon species can be divided into two classes: caldesmon77 (Mr 70,000-80,000) and caldesmon150 (Mr 140,000-150,000). We have examined the phosphorylation of caldesmon77 by protein kinase C (the Ca2+/phospholipid-dependent enzyme) in vitro and in intact platelets. Caldesmon77, purified from bovine liver, could be phosphorylated by purified rat brain protein kinase C to a level of approximately 1.0 mol of phosphate per mol of caldesmon77 monomer. Two-dimensional tryptic peptide mapping and phosphoamino acid analysis reveals that caldesmon77 is phosphorylated at two major sites exclusively on serine residues. Following treatment of platelets with tumor-promoting phorbol ester, caldesmon77 phosphorylation was elevated 4-fold. Tryptic peptide mapping of phosphorylated platelet caldesmon77 demonstrates that phosphorylation is most significantly enhanced on two peptides which had migration patterns identical with those of the two major phosphopeptides of bovine liver caldesmon77 phosphorylated in vitro. The results of this study indicate that protein kinase C can phosphorylate caldesmon77 in vitro and in intact platelets, suggesting a role for protein kinase C in the regulation of caldesmon77 function or localization.
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PMID:Phosphorylation of caldesmon77 by protein kinase C in vitro and in intact human platelets. 359 62

Numerous genes and their products are involved in the expression of the transformed phenotype. Chemical carcinogens transform cells by altering the structure and function of these macromolecules. Some of them have been identified as oncogenes and oncogene products whereas most of the rest are unknown. Since the expressions of transformed phenotype such as alteration of cell morphology, motility and growth are closely correlated to the alteration of cytoskeletal structures, we have investigated the genetic and post-translational alterations of actin and actin-binding proteins in transformed cells. We have found that the expression of a point-mutated beta-actin correlates with the expression of transformed phenotype in one of these chemically transformed human cell lines. Mutated beta-actin showed reduced ability for self-polymerization in vitro, which coincides with the observation in vivo in reduced incorporation of the mutated actin into the cytoskeletal fraction. On the other hand, actin-binding proteins, caldesmon and calspectin which also bind to calmodulin, and 36K protein which also binds to calspectin, were examined using antibodies specific for each protein. Their binding to counterproteins was dependent on the Ca++ concentration. Compared with the untransformed NIH3T3 cells, the NIH3T3 cells transformed by various oncogenes showed considerably smaller amounts of the three proteins and an increase in their phosphorylated forms. The degradation rate of caldesmon and calspectin did not differ between untransformed and transformed cells. Phosphoamino acid analysis showed that the serine residue was the major site for phosphorylation in calspectin whereas calspectin was a good substrate in vitro for both src tyrosine protein kinase and protein kinase C, while 36K protein was phosphorylated at the tyrosine residue as well as the serine residue. The addition of tumor promoter to cultured cells also caused changes in actin-binding proteins simultaneously with changes in morphology, motility and microfilament structure and with the induction of transcription of the beta-actin gene. The role of actin and actin-binding proteins in the cascade reactions induced by oncogene products was discussed.
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PMID:[Malignant transformation and alteration of actin-related proteins]. 360 34

The changes in protein phosphorylation associated with bovine tracheal smooth muscle contraction were studied by labeling intact muscle strips with [32P]PO4(3-) and analyzing the phosphoproteins by two-dimensional gel electrophoresis. Among 20 to 30 phosphoproteins resolvable with the two-dimensional electrophoresis system, the phosphorylation of 12 proteins was reproducibly affected by treatment with carbachol, in a time-dependent manner. Five of these proteins have been identified as 20-kDa myosin light chain, caldesmon, synemin, and two isoelectric variants of desmin. The other 7 are low molecular weight (Mr less than 40,000) cytosolic proteins. One cytosolic protein and myosin light chain are quickly but transiently phosphorylated by carbachol, the peak of myosin light chain phosphorylation being at about 1 min after agonist addition. In contrast, both variants of desmin, synemin, caldesmon, and 5 cytosolic proteins are phosphorylated at varying rates and remain phosphorylated for the duration of carbachol action. These "late" phosphorylation changes occur simultaneously with the dephosphorylation of one cytosolic protein. These carbachol-induced phosphorylation changes, like the contractile response, appear to be calcium-dependent. The addition of 12-deoxyphorbol 13-isobutyrate, a protein kinase C activator, causes a dose-dependent, sustained contraction of tracheal smooth muscle which develops more slowly than that induced by carbachol. This contractile response is associated with the same protein phosphorylation changes as those observed after prolonged carbachol treatment. In contrast, forskolin, an adenylate cyclase activator and a potent smooth muscle relaxant, induces the phosphorylation protein 3 and one variant of desmin. These observations strongly suggest that different phosphoproteins may be mediators of tension development and tension maintenance in agonist-induced contraction of tracheal smooth muscle.
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PMID:Carbachol-induced protein phosphorylation changes in bovine tracheal smooth muscle. 378 86

Protein kinase C catalyzes phosphorylation of caldesmon, an F-actin binding protein of smooth muscle, in the presence of Ca2+ and phospholipid. Protein kinase C incorporates about 8 mol of phosphate/mol of chicken gizzard caldesmon. When calmodulin was added in the medium, there was an inhibition of phosphorylation. The fully phosphorylated, but not unphosphorylated, caldesmon inhibited myosin light chain kinase activity. The possibility that protein kinase C plays some role in smooth muscle contractile system through caldesmon, warrants further attention.
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PMID:Phosphorylation of caldesmon by protein kinase C. 390 49


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