Cockcroft S
Department of Physiology, University College London.
Bioessays. 1998 May;20(5):423-32. doi: 10.1002/(SICI)1521-1878(199805)20:5<423::AID-BIES9>3.0.CO;2-O.
Phosphatidylinositol transfer protein (PITP) was originally identified and named because of its ability to transport phosphatidylinositol through the aqueous phase from one membrane compartment to another. Recent data, however, indicate unanticipated roles for PITP in the coupling of PIP2 synthesis to signal transduction reactions and to membrane traffic in mammalian cells. PITP was recently purified on the basis of its ability to restore cellular functions in permeabilized cells depleted of cytosolic proteins. These functions include cell-surface receptor-regulated hydrolysis of PIP2 by phospholipases C beta- and gamma-isozymes, regulated release of secretory granules, and the budding of constitutive secretory vesicles and immature secretory granules from the trans-Golgi network. In the yeast Saccharomyces cerevisiae, a PITP was identified from a mutant strain with a defect in the secretory pathway (SEC14) and therefore required for cell viability; in Yarrowia lipolytica, PITP is required for differentiation from a yeast to a mycelial growth form. We are just beginning to unravel the intriguing mechanisms by which PITP/SEC14 may accomplish its function in eukaryotic cells in signal transduction and membrane trafficking.
磷脂酰肌醇转移蛋白（PITP）最初因其能够将磷脂酰肌醇通过水相从一个膜区室转运到另一个膜区室的能力而被鉴定和命名。然而，最近的数据表明，PITP在哺乳动物细胞中磷脂酰肌醇-4,5-二磷酸（PIP2）合成与信号转导反应以及膜运输的偶联中具有意想不到的作用。最近，PITP是根据其在缺乏胞质蛋白的通透细胞中恢复细胞功能的能力而被纯化的。这些功能包括细胞表面受体调节的磷脂酶Cβ和γ同工酶对PIP2的水解、分泌颗粒的调节性释放，以及从反式高尔基体网络出芽形成组成型分泌囊泡和未成熟分泌颗粒。在酿酒酵母中，从一个分泌途径存在缺陷（SEC14）的突变菌株中鉴定出一种PITP，因此它是细胞存活所必需的；在解脂耶氏酵母中，PITP是从酵母分化为菌丝体生长形式所必需的。我们才刚刚开始揭示PITP/SEC14在真核细胞信号转导和膜运输中发挥其功能的有趣机制。
