Cell biological functions of phosphoinositides-phosphorylation of 5-position

对于囊泡运输，囊泡上的分子与细胞质蛋白之间的相互作用是重要的。在这项研究中，我们专注于磷脂酰肌醇（PI）的囊泡膜和它的磷酸化。PI的磷酸化受磷脂酰肌醇激酶和磷酸酶的调节。尤其是磷脂酰肌醇（4，5）二磷酸（PIP 2）对于膜运输是重要的。PIP 2产生的最后一步由磷脂酰肌醇磷酸5-激酶（PIP 5 K）催化。PIP 5 K增加细胞内肌动蛋白的聚合。对于胞内囊泡，聚合的肌动蛋白通常与囊泡的一侧相关联，并且囊泡与聚合的肌动蛋白尾部一起移动。在被细菌病原体感染的宿主细胞中观察到类似的运动。在囊泡膜和细胞质之间的界面处，增加的PIP 2通过肌醇结合区募集N-WASP（Wiscott-Aldrich综合征蛋白）并诱导构象变化。这导致其C-末端结构域的活化以诱导肌动蛋白聚合。通过使用绿色荧光蛋白（GFP）衍生物的活细胞成像，我们可以观察到动态的细胞内囊泡运动。这些结果表明，除了微管上的囊泡运动，肌动蛋白聚合可能有助于细胞内囊泡运动和磷酸肌醇的水平调节这种肌动蛋白为基础的运动。

For vesicular traffic, the interaction between molecules on vesicles and cytoplasmic proteins is important. In this study, we focused on phosphoinositides (PI) on the vesicular membrane and its phosphorylation. Phosphorylation of PI is regulated by phosphatidylinositol kinases and phosphatases. Especially, phosphatidylinositol (4,5) bisphosphate (PIP2) is important for membrane traffic. The final step of PIP2 production is catalyzed by phosphatidylinositol phosphate 5-kinases (PIP5K). PIP5K increased actin polymerixzation in cells. For intracellular vesicles, polymerized actin was very often associated with one side of vesicles and vesicles moved around with polymerized actin tails. Similar movement was observed in host cells infected by bacterial pathogens. At the interface between vesicle membrane and cytoplasm, increased PIP2 recruited N-WASP (Wiscott- Aldrich syndrome protein) by inositol binding region and induced conformational change. This results in the activation of its C-terminal domain to induce actin polymerization. By live cell imaging using green fluorescent protein (GFP) derivatives, we could observe dynamic intracellular vesicular movement. These results suggest that, in addition to vesicle movement on microtubules, actin polymerization is likely to contribute intracellular vesicular movement and that the levels of phosphoinositides regulate this actin based motility.