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Proc Natl Acad Sci U S A April 30, 2013; 110 (18): 7193-8.

Phosphoinositides and membrane curvature switch the mode of actin polymerization via selective recruitment of toca-1 and Snx9.

Gallop JL , Walrant A , Cantley LC , Kirschner MW .

The membrane-cytosol interface is the major locus of control of actin polymerization. At this interface, phosphoinositides act as second messengers to recruit membrane-binding proteins. We show that curved membranes, but not flat ones, can use phosphatidylinositol 3-phosphate [PI(3)P] along with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] to stimulate actin polymerization. In this case, actin polymerization requires the small GTPase cell cycle division 42 (Cdc42), the nucleation-promoting factor neural Wiskott-Aldrich syndrome protein (N-WASP) and the actin nucleator the actin-related protein (Arp) 2/3 complex. In liposomes containing PI(4,5)P2 as the sole phosphoinositide, actin polymerization requires transducer of Cdc42 activation-1 (toca-1). In the presence of phosphatidylinositol 3-phosphate, polymerization is both more efficient and independent of toca-1. Under these conditions, sorting nexin 9 (Snx9) can be implicated as a specific adaptor that replaces toca-1 to mobilize neural Wiskott-Aldrich syndrome protein and the Arp2/3 complex. This switch in phosphoinositide and adaptor specificity for actin polymerization from membranes has implications for how different types of actin structures are generated at precise times and locations in the cell.

PubMed ID: 23589871
PMC ID: PMC3645562
Article link: Proc Natl Acad Sci U S A
Grant support: [+]

Species referenced: Xenopus
Genes referenced: actl6a aicda cdc42 fnbp1l snx9 was wasl

References [+] :
Almendinger, A conserved role for SNX9-family members in the regulation of phagosome maturation during engulfment of apoptotic cells. 2011, Pubmed