Class II phosphoinositide 3-kinase α-isoform regulates Rho, myosin phosphatase and contraction in vascular smooth muscle
Class II phosphoinositide 3-kinase α-isoform regulates Rho, myosin phosphatase and contraction in vascular smooth muscle
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DOI：
10.1042/bj20051471
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发表时间：
2006-03-15
影响因子：
4.1
通讯作者：
Takuwa, Y
中科院分区：
文献类型：
--
作者：
Wang, Y;Yoshioka, K;Takuwa, Y
我们以前证明，膜去极化和兴奋性受体激动剂，如去甲肾上腺素诱导的Ca（2+）依赖性Rho激活VSM（血管平滑肌），导致在MP（肌球蛋白磷酸酶）抑制通过涉及Rho激酶介导的磷酸化的机制，其调节亚基MYPT 1。在本研究中，我们发现在去内皮化的VSM条中，PI 3 K（磷酸肌醇3-激酶）抑制剂LY 294002和渥曼青霉素抑制KCl膜去极化和去甲肾上腺素诱导的Rho激活和MYPT 1磷酸化，同时抑制MLC（20 kDa肌球蛋白轻链）磷酸化和收缩。LY 294002还增强了MLC的去磷酸化和KCl收缩的VSM的结果松弛，而LY 294002在MP被磷酸酶抑制剂或佛波酯以Rho非依赖性方式抑制的条件下有效性低得多或无效。VSM表达至少四种PI 3 K同种型，包括I类酶p110 α和p110 β以及II类酶PI 3 K-C2 α和-C2 β。PI 3 K抑制剂诱导的Rho、MLC磷酸化和收缩抑制的剂量-反应关系与PI 3 K-C2 α抑制相似，但与I类PI 3 K抑制不同。此外，KCl和去甲肾上腺素以Ca（2+）依赖性方式诱导PI 3 K-C2 α的刺激，但不诱导p110 α或p110 β的刺激。通过siRNA（小干扰RNA）下调PI 3 K-C2 α表达抑制VSM细胞中MYPT 1和MLC的收缩和磷酸化。最后，静脉注射渥曼青霉素诱导大鼠持续性低血压，抑制动脉中PI 3 K-C2 α活性、Rho的GTP负载和MYPT 1磷酸化。这些结果表明PI 3 K-C2 α在Ca（2+）依赖性Rho介导的MP负性控制和VSM收缩中的新作用。
We demonstrated previously that membrane depolarization and excitatory receptor agonists such as noradrenaline induce Ca(2+)- dependent Rho activation in VSM (vascular smooth muscle), resulting in MP (myosin phosphatase) inhibition through the mechanisms involving Rho kinase-mediated phosphorylation of its regulatory subunit MYPT1. In the present study, we show in de-endothelialized VSM strips that the PI3K (phosphoinositide 3-kinase) inhibitors LY294002 and wortmannin inhibited KCI membrane depolarization- and noradrenaline-induced Rho activation and MYPT1 phosphorylation, with concomitant inhibition of MLC (20-kDa myosin light chain) phosphorylation and contraction. LY294002 also augmented de-phosphorylation of MLC and resultantly relaxation in KCI-contracted VSM, whereas LY294002 was much less effective or ineffective under the conditions in which MP was inhibited by either a phosphatase inhibitor or a phorbol ester in Rho-independent manners. VSM express at least four PI3K isoforms, including the class I enzymes p110 alpha and p110 beta and the class II enzymes PI3K-C2 alpha and -C2 beta. The dose-response relationships of PI3K-inhibitor-induced inhibition of Rho, MLC phosphorylation and contraction were similar to that of PI3K-C2 alpha inhibition, but not to that of the class I PI3K inhibition. Moreover, KCl and noradrenaline induced stimulation of PI3K-C2 alpha in a Ca(2+)-dependent manner, but not of p110 alpha or p110 beta. Down-regulation of PI3K-C2 alpha expression by siRNA (small interfering RNA) inhibited contraction and phosphorylation of MYPT1 and MLC in VSM cells. Finally, intravenous wortmannin infusion induced sustained hypotension in rats, with inhibition of PI3K-C2 alpha activity, GTP-loading of Rho and MYPT1 phosphorylation in the artery. These results indicate the novel role of PI3K-C2 alpha in Ca(2+)-dependent Rho-mediated negative control of MP and thus VSM contraction.