Corequirement of specific phosphoinositides and small GTP-binding protein Cdc42 in inducing actin assembly in Xenopus egg extracts.
Corequirement of specific phosphoinositides and small GTP-binding protein Cdc42 in inducing actin assembly in Xenopus egg extracts.
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DOI：
10.1083/jcb.140.5.1125
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发表时间：
1998-03-09
期刊：
影响因子：
--
通讯作者：
Kirschner MW
中科院分区：
文献类型：
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作者：
Ma L;Cantley LC;Janmey PA;Kirschner MW
磷酸肌醇和Rho家族的小G蛋白结合蛋白都被认为可以调节细胞中肌动蛋白的组装。我们已经重建了肌动蛋白组装在非洲爪蟾提取物中响应这些信号，并检查这些途径的关系。我们发现，GTP γ S刺激肌动蛋白组装存在的内源性膜囊泡在低速提取物。这些膜囊泡是必需的，但可以用从含有磷酸肌醇的纯化磷脂制备的脂质囊泡代替。含有磷脂酰肌醇（4，5）二磷酸或磷脂酰肌醇（3，4，5）三磷酸的囊泡即使在没有GTP γ S的情况下也能诱导肌动蛋白组装。RhoGDI是Rho家族的鸟嘌呤核苷酸解离抑制剂，抑制磷酸肌醇诱导的肌动蛋白组装，表明Rho家族小G蛋白的参与。使用这些G蛋白的各种显性突变体，我们证明了Cdc42磷酸肌醇诱导的肌动蛋白组装的要求。我们的研究结果表明，磷酸肌醇可能有助于GTP交换Cdc42，以及锚Cdc42和肌动蛋白成核活动。因此，这两个磷酸肌醇和Cdc42都需要在这个无细胞系统中诱导肌动蛋白组装。
Both phosphoinositides and small GTP-binding proteins of the Rho family have been postulated to regulate actin assembly in cells. We have reconstituted actin assembly in response to these signals in Xenopus extracts and examined the relationship of these pathways. We have found that GTPγS stimulates actin assembly in the presence of endogenous membrane vesicles in low speed extracts. These membrane vesicles are required, but can be replaced by lipid vesicles prepared from purified phospholipids containing phosphoinositides. Vesicles containing phosphatidylinositol (4,5) bisphosphate or phosphatidylinositol (3,4,5) trisphosphate can induce actin assembly even in the absence of GTPγS. RhoGDI, a guanine-nucleotide dissociation inhibitor for the Rho family, inhibits phosphoinositide-induced actin assembly, suggesting the involvement of the Rho family small G proteins. Using various dominant mutants of these G proteins, we demonstrate the requirement of Cdc42 for phosphoinositide-induced actin assembly. Our results suggest that phosphoinositides may act to facilitate GTP exchange on Cdc42, as well as to anchor Cdc42 and actin nucleation activities. Hence, both phosphoinositides and Cdc42 are required to induce actin assembly in this cell-free system.