Profilin and gelsolin stimulate phosphatidylinositol 3-kinase activity
Profilin and gelsolin stimulate phosphatidylinositol 3-kinase activity
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DOI：
10.1021/bi9609634
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发表时间：
1996-12-24
期刊：
影响因子：
2.9
通讯作者：
Chauhan, VPS
中科院分区：
文献类型：
--
作者：
Singh, SS;Chauhan, A;Chauhan, VPS
肌动蛋白结合蛋白如profilin和gelsolin与磷脂酰肌醇（PI） 4,5-二磷酸（PI 4,5- p -2）结合并调节单体肌动蛋白的浓度。我们在这里报道，profilin和gelsolin以浓度依赖的方式刺激PI 3激酶介导的PI 4,5- p -2（脂激酶活性）磷酸化。这种作用是特异性的profilin和gelsolin，因为其他细胞骨架蛋白如tau或肌动蛋白不影响PI 3-激酶活性。除了脂质激酶活性外，PI - 3激酶还具有蛋白激酶活性：它磷酸化蛋白质（PI - 3激酶的p85亚基）。而在profilin的存在下，pi3 -激酶的蛋白激酶活性不受影响。动力学分析表明，作为不同浓度ATP和PI 4,5- p -2的函数，profilin影响PI 3-激酶的V-max而不影响km， profilin还可能通过与PI 3-激酶的直接关联而影响PI 3-激酶的活性，因为使用谷胱甘肽s -转移酶（GST）抗体的点印迹分析表明，PI 3-激酶的融合蛋白GST-85 kDa与profilin结合。然而，PI 3-激酶不影响profilin的肌动蛋白隔离能力（由pyrenee标记的actin测定），这表明actin和p85在profilin上没有共同的结合位点。这些研究表明，profilin和gelsolin可能控制3-OH磷酸化的磷酸肌苷的产生，从而调节肌动蛋白聚合。
Actin-binding proteins such as profilin and gelsolin bind to phosphatidylinositol (PI) 4,5-bisphosphate (PI 4,5-P-2) and regulate the concentration of monomeric actin. We report here that profilin and gelsolin stimulate PI 3-kinase-mediated phosphorylation of PI 4,5-P-2 (lipid kinase activity) in a concentration-dependent manner. This effect is specific to profilin and gelsolin because other cytoskeletal proteins such as tau or actin do not affect PI 3-kinase activity. In addition to lipid kinase activity, PI 3-kinase also has protein kinase activity: it phosphorylates proteins (p85 subunit of PI 3-kinase). However, the protein kinase activity of PI 3-kinase was not affected in the presence of profilin. Kinetic analysis, as a function of varying concentrations of ATP and PI 4,5-P-2, showed that profilin affects the V-max of PI 3-kinase without affecting km. Profilin may also affect PI 3-kinase activity by its direct association to the enzyme because dot-blot analysis using antibody to glutathione S-transferase (GST) suggested that GST-85 kDa, a fusion protein of PI 3-kinase, binds to profilin. However, PI 3-kinase did not affect the actin-sequestering ability of profilin (determined by pyrene-labeled actin), which indicates that actin and p85 do not share a common binding site on profilin. These studies suggest that profilin and gelsolin may control the generation of 3-OH phosphorylated phosphoinositides, which in turn may regulate the actin polymerization.