Differential Regulation of WASP and N-WASP by Cdc42, Rac1, Nck, and PI(4,5)P2

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• 作者：Nenad Tomasevic ; Zhiheng Jia ; Alan Russell ; Toby Fujii ; James J. Hartman ; Sheila Clancy ; Manping Wang ; Christophe Beraud ; Kenneth W. Wood ; Roman Sakowicz
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：March 20, 2007
• 年：2007
• 卷：46
• 期：11
• 页码：3494 - 3502
• 全文大小：230K
• 年卷期：v.46,no.11(March 20, 2007)
• ISSN：1520-4995

文摘

The Wiskott-Aldrich syndrome protein (WASP) and neural WASP (N-WASP) are key playersin regulating actin cytoskeleton via the Arp2/3 complex. It has been widely reported that the WASPproteins are activated by Rho family small GTPase Cdc42 and that Rac1 acts through SCAR/WAVEproteins. However, a systematic study of the specificity of different GTPases for different Arp2/3 activatorshas not been conducted. In this study, we have expressed, purified, and characterized completely soluble,highly active, and autoinhibited full-length human WASP and N-WASP from mammalian cells. We showa novel N-WASP activation by Rho family small GTPase Rac1. This GTPase exclusively stimulatesN-WASP and has no effects on WASP. Rac1 is a significantly more potent N-WASP activator thanCdc42. In contrast, Cdc42 is a more effective activator of WASP than N-WASP. Lipid vesicles containingPIP2 significantly improve actin nucleation by the Arp2/3 complex and N-WASP in the presence ofRac1 or Cdc42. PIP2 vesicles have no effect on WASP activity alone. Moreover, the inhibition of WASP-stimulated actin nucleation in the presence of Cdc42 and PIP2 vesicles has been observed. We found thatadaptor proteins Nck1 or Nck2 are the most potent WASP and N-WASP activators with distinct effectson the WASP family members. Our in vitro data demonstrates differential regulation of full-length WASPand N-WASP by cellular activators that highlights fundamental differences of response at the protein-protein level.