Studies on Physiological Roles of Protein Phosphatases in Mammalian Smooth Muscle Tissues

哺乳动物平滑肌组织中蛋白磷酸酶的生理作用研究

基本信息

批准号：
01570062
负责人：
TAKAI Akira
金额：
$ 1.34万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

In mammalian smooth muscle tissues, the composition and physiological functions of protein phosphatases have been studied with the use of okadaic acid (OA), a potent inhibitor of type 2A and type 1 protein phosphatases, and inhibitor 2, an intrinsic inhibitory factor of type 1 phosphatase. We have obtained the following results :[1] In the extracts of smooth muscle tissues of guinea-pig, we have identified the following four distinct protein phosphatase activities : an inhibitor 2-sensitive (type 1) phosphatase activity which is susceptible to OA, a Mg^<2+>-dependent and OA-insensitive (type 2C) phosphatase activity, and two type 2A-like phosphatase activities with different susceptibilities to OA. We have also obtained results indicating that the type 2A-like fraction with lower affinity to okadaic acid may be responsible for dephosphorylation of myosin light chains to induce relaxation of smooth muscle.[2] In isolated myocytes of rabbit trachea, we have shown that the openstate probability of Ca^<2+>-dependent K^+-channel is reversibly increased by either extracellular application of isoprenaline or intracellular application of protein kinase A. We have also observed that this effect is significantly enhanced and prolonged in the presence of okadaic acid.[3] So far the dephosphorylation of p-nitrophenyl phosphate (pNPP) by protein phosphatase preparations has been thought to be due to contamination by alkaline phosphatases. We have found that the activity of protein phosphatases are very susceptible to OA, to the same extent as is their activity against phosphorylated proteins. As OA has been shown to have no effect on alkaline phosphatases, this result indicates that the activity against pNPP is intrinsic to the protein phosphatases.

在哺乳动物平滑肌组织中，已经研究了蛋白质磷酸酶的组成和生理功能，使用了冈田酸（OA）（OA），这是一种有效的2A型和1型蛋白质磷酸酶的有效抑制剂，以及抑制剂2（一种1型磷酸酶的固有抑制因子）。 We have obtained the following results :[1] In the extracts of smooth muscle tissues of guinea-pig, we have identified the following four distinct protein phosphatase activities : an inhibitor 2-sensitive (type 1) phosphatase activity which is susceptible to OA, a Mg^<2+>-dependent and OA-insensitive (type 2C) phosphatase activity, and two type 2A-like phosphatase activities with different susceptibilities to OA。我们还获得了结果，表明与冈田酸亲和力较低的2A型分数可能是肌球蛋白轻链的去磷酸化，以诱导平滑肌的松弛。[2]在孤立的兔气管肌细胞中，我们已经表明，通过异位肾上腺素的细胞外应用或蛋白激酶的细胞内应用。我们也观察到，这种效果显着增强并延长了OKADAIC酸。到目前为止，蛋白质磷酸酶制剂的p-硝基苯基磷酸盐（PNPP）的去磷酸化已被认为是碱性磷酸酶污染的。我们发现，蛋白质磷酸酶的活性非常容易受到OA的影响，与它们对磷酸化蛋白的活性相同。由于已经证明OA对碱性磷酸酶没有影响，因此该结果表明对PNPP的活性与蛋白质磷酸酶的固有性。