Regulation by GDI of RhoA/Rho-kinase-induced Ca2+ sensitization of smooth muscle myosin II.
Regulation by GDI of RhoA/Rho-kinase-induced Ca2+ sensitization of smooth muscle myosin II.
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GDI 对 RhoA/Rho 激酶诱导的平滑肌肌球蛋白 II Ca2 敏化的调节。
DOI：
10.1152/ajpcell.2001.281.1.c257
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Somlyo,AP
中科院分区：
文献类型：
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作者：
Gong,MC;Gorenne,I;Read,P;Jia,T;Nakamoto,RK;Somlyo,AV;Somlyo,AP
我们的特点是鸟嘌呤核苷酸解离抑制剂（GDI）在RhoA/Rho激酶介导的平滑肌Ca 2+敏化的作用。RhoA和RhoGDI的内源性含量（约2-4 μM）接近化学计量比，而超生理的GDI浓度则需要用于缓解GTP和鸟苷5′-O-（3-硫代三磷酸）（GTPγS）对Ca 2+的力敏感性。GDI还抑制GTP ·G14 V RhoA、α-肾上腺素能激动剂和毒蕈碱激动剂对Ca ~（2+）的增敏作用，并从膜上提取RhoA。GTPγS将Rho激酶转运至Triton X-114可提取的膜组分。GTP ·G14 V RhoA与GDI复合物也可诱导Ca ~（2+）敏化，可能是通过在体内将GTP · RhoA从复合物中解离出来，因为过量的GDI可逆转这种作用。GDI不抑制佛波醇酯对Ca ~（2+）的敏化作用。Cdc 42和Rac 1抑制GTP ·G14 V RhoA对Ca ~（2+）的增敏作用。我们得出结论：1）GDI最可能的体内功能是阻止GDP · RhoA向GTP · RhoA的永久“循环”;2）复合GDP · RhoA/GDI上的核苷酸交换（GTP交换GDP）可以先于RhoA易位到膜上;3）Rho激酶的激活暴露了一个疏水结构域; 4）Cdc 42和Rac 1可以抑制激活的GTP · RhoA对Ca 2+的敏化作用。
We characterized the role of guanine nucleotide dissociation inhibitor (GDI) in RhoA/Rho-kinase-mediated Ca2+sensitization of smooth muscle. Endogenous contents (∼2–4 μM) of RhoA and RhoGDI were near stoichiometric, whereas a supraphysiological GDI concentration was required to relax Ca2+sensitization of force by GTP and guanosine 5′-O-(3-thiotriphosphate) (GTPγS). GDI also inhibited Ca2+sensitization by GTP · G14V RhoA, by α-adrenergic and muscarinic agonists, and extracted RhoA from membranes. GTPγS translocated Rho-kinase to a Triton X-114-extractable membrane fraction. GTP · G14V RhoA complexed with GDI also induced Ca2+sensitization, probably through in vivo dissociation of GTP · RhoA from the complex, because it was reversed by addition of excess GDI. GDI did not inhibit Ca2+sensitization by phorbol ester. Constitutively active Cdc42 and Rac1 inhibited Ca2+sensitization by GTP · G14V RhoA. We conclude that1) the most likely in vivo function of GDI is to prevent perpetual “recycling” of GDP · RhoA to GTP · RhoA;2) nucleotide exchange (GTP for GDP) on complexed GDP · RhoA/GDI can precede translocation of RhoA to the membrane;3) activation of Rho-kinase exposes a hydrophobic domain; and4) Cdc42 and Rac1 can inhibit Ca2+sensitization by activated GTP · RhoA.