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首页> 美国卫生研究院文献>The Journal of General Physiology >A novel mechanism for the Ca(2+)-sensitizing effect of protein kinase C on vascular smooth muscle: inhibition of myosin light chain phosphatase
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A novel mechanism for the Ca(2+)-sensitizing effect of protein kinase C on vascular smooth muscle: inhibition of myosin light chain phosphatase

机译：蛋白激酶C对血管平滑肌的Ca（2+）致敏作用的新机制：抑制肌球蛋白轻链磷酸酶。

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摘要

Mechanisms of Ca2+ sensitization of both myosin light chain (MLC) phosphorylation and force development by protein kinase C (PKC) were studied in permeabilized tonic smooth muscle obtained from the rabbit femoral artery. For comparison, the Ca2+ sensitizing effect of guanosine 5'-O-(gamma-thiotriphosphate) (GTP gamma S) was examined, which had been previously shown to inhibit MLC phosphatase in phasic vascular smooth muscle. We now report that PKC activators (phorbol esters, short chain synthetic diacylglycerols and a diacylglycerol kinase inhibitor) and GTP gamma S significantly increase both MLC phosphorylation and force development at constant [Ca2+]. Major phosphorylation site occurring in the presence of phorbol-12,13- dibutyrate (PDBu) or GTP gamma S at constant [Ca2+] is the same serine residue (Ser-19) as that phosphorylated by MLC kinase in response to increased Ca2+ concentrations. In an ATP- and Ca(2+)-free solution containing 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4- diazepine (ML-9), to avoid the kinase activity, both PDBu and GTP gamma S significantly decreased the rate of MLC dephosphorylation to half its control value. However, PDBu inhibited the relaxation rate more than did GTP gamma S. In the presence of microcystin-LR to inhibit the phosphatase activity, neither PDBu nor GTP gamma S affected MLC phosphorylation and force development. These results indicate that PKC, like activation of GTP binding protein, increases Ca2+ sensitivity of both MLC phosphorylation and force production through inhibition of MLC phosphatase.
机译：在从兔股动脉获得的通透性滋养平滑肌中，研究了肌球蛋白轻链（MLC）磷酸化和蛋白激酶C（PKC）产生力的Ca2 +敏化机制。为了进行比较，研究了鸟苷5'-O-（γ-硫代三磷酸）（GTPγS）的Ca2 +增敏作用，先前已证明其可抑制相血管平滑肌中的MLC磷酸酶。现在，我们报道PKC激活剂（佛波酯，短链合成二酰基甘油和二酰基甘油激酶抑制剂）和GTPγS显着增加了MLC磷酸化和恒定[Ca2 +]力的产生。在存在恒定[Ca2 +]的phorbol-12,13-二丁酸酯（PDBu）或GTPγS存在下，主要的磷酸化位点与MLC激酶响应增加的Ca2 +浓度而磷酸化的丝氨酸残基（Ser-19）相同。在包含1-（5-氯萘-1-磺酰基）-1H-六氢-1,4-二氮杂（ML-9）的不含ATP和Ca（2+）的溶液中，避免PDBu和GTPγS显着降低了MLC的去磷酸化速率至其控制值的一半。但是，PDBu比GTPγS更能抑制松弛率。在存在微囊藻毒素-LR抑制磷酸酶活性的情况下，PDBu和GTPγS均不影响MLC磷酸化和作用力的发展。这些结果表明，PKC像激活GTP结合蛋白一样，增加了MLC磷酸化的Ca2 +敏感性，并通过抑制MLC磷酸酶而增强了产生力。

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