Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study determined if phorbol ester-induced contraction of vascular smooth muscle requires calcium-dependent myosin light chain (MLC) phosphorylation and, if not, whether the mechanical characteristics of the contraction in terms of stiffness and crossbridge cycling are similar to those during a calcium- and MLC phosphorylation-dependent contraction. Carotid arterial strips were exposed to 1.0 microM phorbol 12,13-dibutyrate (PDBu) in the presence of normal physiological salt solution (PSS) or after calcium depletion in calcium-free PSS and compared with contraction elicited by calcium-containing 110 mM KCl-PSS. PDBu induced maximal stress in both the presence and absence of calcium. While there was a temporal correlation between MLC phosphorylation and shortening velocity during KCl depolarization, shortening velocity was dissociated from MLC phosphorylation during PDBu stimulation. The stress-stiffness relationship was not different during KCl and PDBu stimulation, suggesting similar crossbridge interactions even though MLC phosphorylation levels were significantly different. These results demonstrate that PDBu-induced contraction of the swine carotid artery is not dependent on calcium or MLC phosphorylation. We suggest the possibility that activation of a calcium-independent PKC isoform may result in the expression of an inherent level of actin-activated myosin ATPase activity resulting in the slow development of stress.
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PMID:Phorbol ester-induced contractions of swine carotid artery are supported by slowly cycling crossbridges which are not dependent on calcium or myosin light chain phosphorylation. 824 64

We previously demonstrated that ERK/PKC signaling pathways play a key role in regulation of Ca(2+) sensitivity and contractility of the uterine artery. The present study tested the hypothesis that ERK and PKC differentially regulated myosin light chain phosphatase activity by phosphorylation of myosin phosphatase target protein-1 (MYPT-1) and CPI-17. Agonist-induced contractions and phosphorylation of MYPT-1/Thr(696), MYPT-1/Thr(850), and CPI-17/Thr(38) were measured simultaneously in the same tissues of isolated near-term pregnant ovine uterine arteries. Phenylephrine produced time-dependent concurrent increases in the phosphorylation of ERK(44/42) and MYPT-1/Thr(850) that preceded contractions. In addition, phenylephrine induced phosphorylation of CPI-17/Thr(38) that was concurrent with the contractions. In contrast, phenylephrine did not induce phosphorylation of MYPT-1/Thr(696) in the uterine artery. PD-098059 inhibited phosphorylation of ERK(44/42) and the initial peak phosphorylation of MYPT-1/Thr(850) but did not affect CPI-17/Thr(38) phosphorylation. Activation of PKC by phorbol 12,13-dibutyrate induced a time-dependent phosphorylation of CPI-17/Thr(38) that preceded contractions of the uterine artery. In addition, phorbol 12,13-dibutyrate activated PKC-alpha and induced a coimmunoprecipitation of PKC-alpha with caldesmon. The results suggest that phosphorylation of MYPT-1/Thr(850) and CPI-17/Thr(38) play important roles in regulation of agonist-mediated Ca(2+) sensitivity in the uterine artery, in part by ERK and PKC, respectively. In addition, phosphorylated CPI-17 may regulate Ca(2+) sensitivity by interacting with caldesmon and reversing its inhibitory effect on myosin ATPase.
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PMID:Alpha1-adrenoceptor-mediated phosphorylation of MYPT-1 and CPI-17 in the uterine artery: role of ERK/PKC. 1566 49