Functional analysis of phosphatidylinositol 5-kinases (PIP5K)

(1)突变体PIP5K分析：通过删除n端或c端，PIP5K的激酶活性定位在中心380个氨基酸区。(2) PIP5K的胞内定位：内源性PIP5K的表达量很低，很难检测到。外源PIP5K主要存在于细胞质膜表面，细胞质中也有。(3) PIP5K反应产物：除生成PI (4,5) P2外，还生成少量的PI (5) P和PI (3,5) P2。(4)肌动蛋白聚合：通过过表达PIP5K，肌动蛋白聚合得到极大增强。(5) Rac与PIP5K的相互作用：在血小板半完整系统中，Rac和PIP5K都参与凝血酶刺激的肌动蛋白聚合过程。当引入Rac突变体时，聚合被抑制，这表明Rac和PIP5K之间的相互作用是肌动蛋白聚合所必需的

(1) Analysis of mutant PIP5K : By deleting either N-terminus or C-terminus, the kinase activity of PIP5K was localized in central 380 amino acids region.(2) Intracellular localization of PIP5K : Endogenous PIP5K was hard to detect as the expression was very low. Exogenous PIP5K was found mainly on the cytoplasmic surface of the plasma membrane and also in the cytoplasm.(3) Products of PIP5K reaction : In addition to PI (4,5) P2, small amount of PI (5) P and PI (3,5) P2 was produced.(4) Actin polymerization : By overexpression of PIP5K, actin polymerization was greatly enhanced.(5) Interactin between Rac and PIP5K : In platelet semiintact system, Rac and PIP5K are both involved in thrombin stimulated actin polymerization process. When a Rac mutant was introduced, the polymerization was inhibited, suggesting that the interaction between Rac and PIP5K is necessary for actin polymerization