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)

To clarify the role of protein kinase C in the mechanical response, the effects of exogenous protein kinase C and its cofactors were investigated on skinned smooth muscle preparations of the rabbit mesenteric artery. Addition of protein kinase C with 12-O-tetradecanoylphorbol-13-acetate (TPA) and phosphatidylserine (PS) caused slow inactivation of a maximal Ca2+ contraction of the muscle fiber and correspondingly increased protein kinase C phosphorylation of myosin light chain. Neither protein kinase C nor enzyme cofactors (PS and TPA) produced relaxation of this tissue and all three components caused significant relaxation. Furthermore, when the muscle fiber was activated by Ca2+-insensitive fragment of MLC-kinase, addition of protein kinase C with PS and TPA decreased the tension and increased protein kinase C phosphorylation of myosin light chain. This evidence suggests that protein kinase C phosphorylation of myosin light chain may play an inhibitory role in the contraction of vascular smooth muscle.
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PMID:Purified rabbit brain protein kinase C relaxes skinned vascular smooth muscle and phosphorylates myosin light chain. 357 93

Cultured dog thyroid cells contain 21 and 19 kilodalton (K) phosphoproteins which by several criteria have been identified as light chains of myosin (MLC). TSH causes a reduction in the phosphorylation state of the 21 K-19 K proteins, at least in part through activating adenylate cyclase and increasing cAMP levels. We now report that 12-O-tetradecanoyl-phorbol-13-acetate (TPA) also decreases the 21 K-19 K protein phosphorylation state, but in contrast to that due to TSH, the TPA-induced decrease is not associated with elevated cAMP levels. The effect of TPA was not additive to that of TSH. Because Ca++ is a major factor regulating MLC kinase and TPA-stimulated protein kinase C in other systems, the role of Ca++ in the phosphorylation of the 21 and 19 K polypeptides in dog thyroid was examined. In intact cells, both (8-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) (1 X 10(-4) M) and trifluoperazine (TFP) (4 X 10(-5) M) increase basal 21 K-19 K protein phosphorylation and inhibit the decrease in phosphorylation caused by TSH and TPA without affecting cAMP levels. Ionophore A23187 (5 X 10(-6) M) counteracts TMB-8- and TFP-stimulated phosphorylation as well as TMB-8 and TFP inhibition of TSH- and TPA-reduced 21 K-19 K phosphorylation. Incubation of 32PO4-labeled dog thyroid cells in the absence of extracellular Ca++ or with verapamil does not significantly affect basally phosphorylated 21 K-19 K proteins or the decreased 21 K-19 K phosphorylation state caused by TSH. These results strongly suggest that the phosphorylation state of the 21 and 19 K proteins is affected more significantly by intracellular Ca++ pools than by extracellular Ca++, and implicate a kinase(s) other than Ca++-calmodulin-dependent MLC kinase in the phosphorylation of MLC in the dog thyroid.
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PMID:Role of cellular Ca++ in phosphorylation of 21 K and 19 K polypeptides in cultured thyroid cells: effects of phorbol ester, trifluoperazine, and 8-diethylamino-octyl-3,4,5-trimethoxybenzoate hydrochloride. 359 18

The fatty acid 12(S)-HETE may be a new second messenger capable of activating PKC. In tumor cells 12(S)-HETE stimulates cytoskeleton-dependent cellular responses such as adhesion and spreading. Analysis of 12(S)-HETE effects on B16a melanoma cell cytoskeleton revealed reversible rearrangement of microtubules, microfilaments, the actin-binding proteins, vinculin, myosin heavy (MHC) and light chains (MLC), as well as bundling of vimentin intermediate filaments. The alterations in microfilaments and intermediate filaments occurred very rapidly, i.e., 5 min after exposure of tumor cells to 12(S)-HETE. The 12(S)-HETE-induced cytoskeletal alterations were accompanied by centrifugal organelle-translocation. Interestingly, MLC exhibited clear association with the cytoplasmic organelles. Biochemical analysis of the 12(S)-HETE effect indicated a PKC-mediated reversible hyperphosphorylation of MLC, vimentin, and a 130 kD cytoskeletal-associated protein. Optimal effects were obtained after 5 min treatment with 12(S)-HETE at 0.1 microM concentration. 12(S)-HETE pretreatment induced tumor cell spreading on a fibronectin matrix which required the intactness of all three major cytoskeletal components. The spreading process was dependent upon the activity of PKC. Our data suggest that 12(S)-HETE is a physiological stimulant of PKC. Further, it induces rearrangement of the cytoskeleton of tumor cells in interphase resulting in the stimulation of cytoskeleton-dependent cell activity such as spreading.
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PMID:PKC mediates 12(S)-HETE-induced cytoskeletal rearrangement in B16a melanoma cells. 822 7

Phosphorylation of the regulatory light chain of myosin II (MLC) controls the contractility of actomyosin in nonmuscle and muscle cells. It has been reported that cdc2 phosphorylates MLC in vitro at Ser-1 or Ser-2 and Thr-9 which protein kinase C phosphorylates (Satterwhite, L. L., M. J. Lohka, K. L. Wilson, T. Y. Scherson, L. K. Cisek, J. L. Corden, and T. D. Pollard. 1992 J. Cell Biol. 118:595-605). We have examined in vivo phosphorylation of MLC during mitosis and after the release of mitotic arrest. Phosphate incorporation of MLC in mitotic cells is found to be 6-12 times greater than that in nonmitotic cells. Phosphopeptide maps have revealed that the MLC from mitotic cells is phosphorylated at Ser-1 and/or Ser-2 (Ser-1/2), but not at Thr-9. MLC is also phosphorylated to a much lesser extent at Ser-19 which myosin light chain kinase phosphorylates. On the other hand, MLC of nonmitotic cells is phosphorylated at Ser-19 but not at Ser-1/2. The extent of phosphate incorporation is doubled at 30 min after the release of mitotic arrest when some cells start cytokinesis. Phosphopeptide analyses have revealed that the phosphorylation at Ser-19 is increased 20 times, while the phosphorylation at Ser-1/2 is decreased by half. This high extent of MLC phosphorylation at Ser-19 is maintained for another 30 min and gradually decreased to near the level of interphase cells as cells complete spreading at 180 min. On the other hand, phosphorylation at Ser-1/2 is decreased to 18% at 60 min, and is practically undetectable at 180 min after the release of mitotic arrest. The stoichiometry of MLC phosphorylation has been determined by quantitation of phosphorylated and unphosphorylated forms of MLC separated on 2D gels. The molar ratio of phosphorylated MLC to total MLC is found to be 0.16 +/- 0.06 and 0.31 +/- 0.05 in interphase and mitotic cells, respectively. The ratio is increased to 0.49 +/- 0.05 at 30 min after the release of mitotic arrest. These results suggest that the change in the phosphorylation site from Ser-1/2 to Ser-19 plays an important role in signaling cytokinesis.
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PMID:In vivo phosphorylation of regulatory light chain of myosin II during mitosis of cultured cells. 829 96

The present study aimed to examine the turnover of phospholipids such as PI, PC and PE, the time course of PKC activity and the phosphorylation of 20 kDa MLC in the canine BA undergoing chronic VS. The phosphorylation of 20 kDa MLC was not augmented in the spastic BA. Turnover of PC and PE was detectably stimulated on day 7. The cytosolic PKC activity was down-regulated on days 4 and 7, while the membrane PKC activity remained unchanged during these periods. The present results indicate that a process which affected the membrane lipid metabolism, PKC metabolism and PKC activity occurred in spastic BA.
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PMID:Possible involvement of C-kinase in occurrence of chronic cerebral vasospasm after subarachnoid hemorrhage. 833 32

Upon platelet activation by a high shear stress (108 dyne/cm2), actin and actin-binding protein increased rapidly into the Triton-insoluble cytoskeleton, whereas the association of myosin increased gradually. The amounts of cytoskeleton-associated myosin depended on the extent of aggregation. Preceding the maximal aggregation and ATP secretion, the 20 kDa light chain of myosin (MLC) is rapidly phosphorylated to approx. 45% of 20 kDa MLC and is then dephosphorylated. Cytoskeletal association of myosin and phosphorylation of 20 kDa MLC was inhibited by OP-41483, a prostaglandin I2 analog, which inhibited the full aggregation response to shear stress. Exposure to high shear stress resulted in an increased association of myosin light chain kinase and protein phosphatase types 1 and 2A with the cytoskeleton, while the cytoskeletal association of protein kinase C was not evident. These results indicate that 20 kDa MLC phosphorylation is involved in shear stress-induced platelet activation, and that cytoskeletal association of protein phosphatases may regulate the phosphorylation level of cytoskeletal elements such as myosin together with myosin light chain kinase.
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PMID:Shear stress-induced myosin association with cytoskeleton and phosphorylation in human platelets. 907 28

The mechanisms by which protein kinase C (PKC) activation results in increased transepithelial resistance (TER) are unknown [G. Hecht, B. Robinson, and A. Koutsouris. Am. J. Physiol. 266 (Gastrointest. Liver Physiol. 29): G214-G221, 1994]. We have previously shown that phosphorylation of the regulatory light chain of myosin II (MLC) is associated with decreases in TER and have suggested that contraction of the perijunctional actomyosin ring (PAMR) increases tight junction (TJ) permeability [J. R. Turner, B. K. Rill, S. L. Carlson, D. Carnes, R. Kerner, R. J. Mrsny, and J. L. Madara. Am. J. Physiol. 273 (Cell Physiol. 42): C1378-C1385, 1997]. We therefore hypothesized that PKC activation alters TER via relaxation of the PAMR. Activation of PKC by the phorbol ester phorbol 12-myristate 13-acetate (PMA) resulted in a progressive dose-dependent increase in TER that was apparent within 15 min (111% of controls) and maximal within 2 h (142% of controls). Similar increases were induced by a diacylglycerol analog, and the effects of both PMA and the diacylglycerol analog were prevented by the PKC inhibitor bisindolylmaleimide I. PMA treatment caused progressive decreases in MLC phosphorylation, by 12% at 15 min and 41% at 2 h. Phosphorylation of MLC kinase (MLCK) increased by 64% within 15 min of PMA treatment and was stable over 2 h (51% greater than that of controls). Thus increases in MLCK phosphorylation preceded decreases in MLC phosphorylation. These data suggest that PKC regulates TER via decreased phosphorylation of MLC, possibly due to inhibitory phosphorylation of MLCK. The decreased phosphorylation of MLC likely reduces PAMR tension, leading to decreased TJ permeability.
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PMID:PKC-dependent regulation of transepithelial resistance: roles of MLC and MLC kinase. 1048 42

Ca(+)/calmodulin-dependent protein kinase II (CaM kinase II) has been implicated in the regulation of smooth muscle contractility. The goals of this study were to determine: 1) to what extent CaM kinase II is activated by contractile stimuli in intact arterial smooth muscle, and 2) the effect of a CaM kinase II inhibitor (KN-93) on CaM kinase II activation, phosphorylation of myosin regulatory light chains (MLC(20)), and force. Both histamine (1 microM) and KCl depolarization activated CaM kinase II with a time course preceding maximal force development, and suprabasal CaM kinase II activation was sustained during tonic contractions. CaM kinase II activation was inhibited by KN-93 pretreatment (IC(50) approximately 1 microM). KN-93 inhibited histamine-induced tonic force maintenance, whereas early force development and MLC(20) phosphorylation responses during the entire time course were unaffected. Both force development and maintenance in response to KCl were inhibited by KN-93. Rapid increases in KCl-induced MLC(20) phosphorylation were also inhibited by KN-93, whereas steady-state MLC(20) phosphorylation responses were unaffected. In contrast, phorbol 12,13-dibutyrate (PDBu) did not activate CaM kinase II and PDBu-stimulated force development was unaffected by KN-93. Thus KN-93 appears to target a step(s) essential for force maintenance in response to physiological stimuli, suggesting a role for CaM kinase II in regulating tonic contractile responses in arterial smooth muscle. Pharmacological activation of protein kinase C bypasses the KN-93 sensitive step.
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PMID:Inhibition of CaM kinase II activation and force maintenance by KN-93 in arterial smooth muscle. 1071 42

We report three cases of platelet dysfunction characterized by defective Ca2+ ionophore-induced platelet aggregation without impaired production of thromboxane A2 (TXA2). The patients had mild to moderate bleeding tendencies, and their platelet aggregation and secretion induced by ADP, collagen, arachidonic acid, stable TXA2 (STA2) and Ca2+ ionophore A23187 was defective or much reduced. However, ristocetin- or thrombin-induced platelet aggregation was normal. The analysis of second messenger formation showed that inositol 1,4,5-triphosphate formation or Ca2+ mobilization induced by thrombin, STA2 or A23187 was normal. Furthermore, the phosphorylation of 47 kDa protein (pleckstrin) and 20 kDa protein (myosin light chain, MLC) in response to those agonists was normal. These findings suggest that the defective site in the patients' platelets lies in the process distal to or independent of protein kinase C activation, Ca2+ mobilization and MLC phosphorylation.
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PMID:Pathogenetic analysis of three cases with a bleeding disorder characterized by defective platelet aggregation induced by Ca2+ ionophores. 1170 55

This article provides an update of a minireview published in 1996 (Abdel-Latif AA. Proc Soc Exp Biol Med 211:163-177, 1996), the purpose of which was to examine in nonvascular smooth muscle the biochemical and functional cross talk between the sympathetic nervous system, which governs the formation of cAMP and muscle relaxation, and the parasympathetic nervous system, which governs the generation of IP3 and diacylglycerol, from the polyphosphoinositides, Ca2+ mobilization, and contraction. This review examines further evidence, both from nonvascular and vascular smooth muscle, for cross talk between the cyclic nucleotides, cAMP and cGMP via their respective protein kinases, and the Ca2+-dependent- and Ca2+-independent-signaling pathways involved in agonist-induced contraction. These include the IP3-Ca2+-CaM- myosin light chain kinase (MLCK) pathway and the Ca2+-independent pathways, including protein kinase C-, MAP kinase-, and Rho-kinase. In addition, MLC phosphorylation and contraction can also be increased by a decrease in myosin phosphatase activity. A summary of the cross talk between the cyclic nucleotides and these signaling pathways was presented. In smooth muscle, there are several targets for cyclic nucleotide inhibition and consequent relaxation, including the receptor, G proteins, phospholipase C-beta1-4 isoforms, IP3 receptor, Ca2+ mobilization, MLCK, MAP kinase, Rho-kinase, and myosin phosphatase. While significant progress has been made in the past four years on this cross talk, the precise mechanisms underlying the biochemical basis for the cyclic nucleotide inhibition of Ca2+ mobilization and consequently muscle contraction remain to be established. Although it is well established that second-messenger cross talk plays an important role in smooth muscle relaxation, the many sources which exist in smooth muscle for Ca2+ mobilization, coupled with the multiple signaling pathways involved in agonist-induced contraction, contribute appreciably to the difficulties found by many investigators in identifying the targets for cyclic nucleotide inhibition and consequent relaxation. Better methodology and more novel interdisciplinary approaches are required for elucidating the mechanism(s) of cAMP- and cGMP-inhibition of smooth muscle contraction.
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PMID:Cross talk between cyclic nucleotides and polyphosphoinositide hydrolysis, protein kinases, and contraction in smooth muscle. 1136 Oct 33


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