Loss of PIP5KIgamma, unlike other PIP5KI isoforms, impairs the integrity of the membrane cytoskeleton in murine megakaryocytes.
Loss of PIP5KIgamma, unlike other PIP5KI isoforms, impairs the integrity of the membrane cytoskeleton in murine megakaryocytes.
复制标题
DOI：
10.1172/jci34239
复制
发表时间：
2008-02
期刊：
影响因子：
--
通讯作者：
Yanfeng Wang;R. Litvinov;Xinsheng Chen;Tami L. Bach;L. Lian;B. Petrich;S. Monkley;Y. Kanaho;D. Critchley;Takehiko Sasaki;M. Birnbaum;J. Weisel;J. Hartwig;C. Abrams
中科院分区：
文献类型：
--
作者：
Yanfeng Wang;R. Litvinov;Xinsheng Chen;Tami L. Bach;L. Lian;B. Petrich;S. Monkley;Y. Kanaho;D. Critchley;Takehiko Sasaki;M. Birnbaum;J. Weisel;J. Hartwig;C. Abrams
磷脂酰肌醇-4，5-二磷酸(PIP(2))是一种丰富的磷脂，有助于第二信使的形成，也被证明在所有真核细胞中都有助于调节细胞骨架的动力学。虽然磷脂酰肌醇-4-磷酸-5-激酶I(PIP5KI)的α、β和伽马亚型都能合成PIP2，但哺乳动物细胞通常含有不止一个PIP5KI亚型。这提出了一个问题，即不同的PIP5KI亚型是否具有不同的功能。考虑到PIP(2)在血小板和巨核细胞肌动蛋白动力学中的推测作用，我们分析了缺乏PIP5KI亚型的小鼠巨核细胞。PIP5KIGamma(-/-)巨核细胞表现为质膜起泡，并伴有膜与细胞骨架结合减少。这种膜缺陷是通过重新添加野生型PIP5KIGamma来修复的，但不是通过添加一个催化不活跃的突变体或缺乏talin结合基序的剪接变异体来修复的。值得注意的是，PIP5KIbeta-和PIP5KIGamma(-/-)细胞都损害了PIP(2)的合成。然而，PIP5KIbeta缺失的细胞缺乏膜-细胞骨架缺陷。此外，在PIP5KIGamma(-/-)细胞中过表达PIP5KIbeta未能逆转这一缺陷。缺乏PIP5KIGamma结合伙伴talin1的巨核细胞模仿了PIP5KIGamma(-/-)细胞的膜-细胞骨架缺陷表型。这些发现表明，PIP5KIGamma在巨核细胞的细胞膜与细胞骨架的锚定中发挥着独特的作用，可能是通过涉及talin的途径。这些观察进一步证明，各个PIP5KI亚型在细胞内发挥着不同的功能。
Phosphatidylinositol-4,5-bisphosphate (PIP(2)) is an abundant phospholipid that contributes to second messenger formation and has also been shown to contribute to the regulation of cytoskeletal dynamics in all eukaryotic cells. Although the alpha, beta, and gamma isoforms of phosphatidylinositol-4-phosphate-5-kinase I (PIP5KI) all synthesize PIP2, mammalian cells usually contain more than one PIP5KI isoform. This raises the question of whether different isoforms of PIP5KI fulfill different functions. Given the speculated role of PIP(2) in platelet and megakaryocyte actin dynamics, we analyzed murine megakaryocytes lacking individual PIP5KI isoforms. PIP5KIgamma(-/-) megakaryocytes exhibited plasma membrane blebbing accompanied by a decreased association of the membrane with the cytoskeleton. This membrane defect was rescued by adding back wild-type PIP5KIgamma, but not by adding a catalytically inactive mutant or a splice variant lacking the talin-binding motif. Notably, both PIP5KIbeta- and PIP5KIgamma(-/-) cells had impaired PIP(2) synthesis. However, PIP5KIbeta-null cells lacked the membrane-cytoskeleton defect. Furthermore, overexpressing PIP5KIbeta in PIP5KIgamma(-/-) cells failed to revert this defect. Megakaryocytes lacking the PIP5KIgamma-binding partner, talin1, mimicked the membrane-cytoskeleton defect phenotype seen in PIP5KIgamma(-/-) cells. These findings demonstrate a unique role for PIP5KIgamma in the anchoring of the cell membrane to the cytoskeleton in megakaryocytes, probably through a pathway involving talin. These observations further demonstrate that individual PIP5KI isoforms fulfill distinct functions within cells.