Fukami K, Endo T, Imamura M, Takenawa T
Department of Molecular Oncology, University of Tokyo, Japan.
J Biol Chem. 1994 Jan 14;269(2):1518-22.
Western blot analysis of Balb/c 3T3 cell lysates by an antibody specific to phosphatidylinositol 4,5-bisphosphate (PIP2) showed that several proteins exist in a PIP2-bound form. Among them, two proteins, 100 and 115 kDa in molecular mass, were detected as PIP2 abundant proteins. These were identified as alpha-actinin and vinculin by their antibodies. In Balb/c 3T3 cells, alpha-actinin in the cytoskeleton contains PIP2, while alpha-actinin in cytosol does not. The levels of PIP2 bound to alpha-actinin decrease in response to platelet-derived growth factor (PDGF). Similarly, PIP2 bound to vinculin is decreased upon stimulation with PDGF. By immunofluorescent staining, PIP2 was found to be present densely in the central areas around nuclei, microfilament bundles, and focal contacts, where alpha-actinin and vinculin are distributed. PDGF stimulation decreases the intensity of PIP2 staining in these areas. In this paper we suggest that tyrosine kinase-activated phospholipase C hydrolyzes PIP2 bound to alpha-actinin and vinculin, leading to the simultaneous generation of second messengers and reorganization of the cytoskeleton.
用磷脂酰肌醇4,5 - 二磷酸（PIP2）特异性抗体对Balb/c 3T3细胞裂解物进行蛋白质免疫印迹分析表明，有几种蛋白质以与PIP2结合的形式存在。其中，检测到两种分子量分别为100 kDa和115 kDa的蛋白质为富含PIP2的蛋白质。用它们的抗体鉴定为α - 辅肌动蛋白和纽蛋白。在Balb/c 3T3细胞中，细胞骨架中的α - 辅肌动蛋白含有PIP2，而胞质溶胶中的α - 辅肌动蛋白则不含。与α - 辅肌动蛋白结合的PIP2水平会因血小板衍生生长因子（PDGF）而降低。同样，在用PDGF刺激后，与纽蛋白结合的PIP2也会减少。通过免疫荧光染色发现，PIP2密集存在于细胞核周围的中心区域、微丝束和粘着斑中，这些地方也是α - 辅肌动蛋白和纽蛋白分布的位置。PDGF刺激会降低这些区域中PIP2染色的强度。在本文中，我们认为酪氨酸激酶激活的磷脂酶C水解与α - 辅肌动蛋白和纽蛋白结合的PIP2，从而导致第二信使的同时产生和细胞骨架的重组。
