title: The Cdc42 effector IRSp53 generates filopodia by coupling membrane protrusion with actin dynamics.
abstract: The Cdc42 effector IRSp53 is a strong inducer of filopodia formation and consists of an Src homology domain 3 (SH3), a potential WW-binding motif, a partial-Cdc42/Rac interacting binding region motif, and an Inverse-Bin-Amphiphysins-Rvs (I-BAR) domain. We show that IRSp53 interacts directly with neuronal Wiskott-Aldrich syndrome protein (N-WASP) via its SH3 domain and furthermore that N-WASP is required for filopodia formation as IRSp53 failed to induce filopodia formation in N-WASP knock-out (KO) fibroblasts. IRSp53-induced filopodia formation can be reconstituted in N-WASP KO fibroblasts by full-length N-WASP, by N-WASPDeltaWA (a mutant unable to activate the Arp2/3 complex), and by N-WASPH208D (a mutant unable to bind Cdc42). IRSp53 failed to induce filopodia in mammalian enabled (Mena)/VASP KO cells, and N-WASP failed to induce filopodia when IRSp53 was knocked down with RNA interference. The IRSp53 I-BAR domain alone induces dynamic membrane protrusions that lack actin and are smaller than normal filopodia ("partial-filopodia") in both wild-type N-WASP and N-WASP KO cells. We propose that IRSp53 generates filopodia by coupling membrane protrusion through its I-BAR domain with actin dynamics through SH3 domain binding partners, including N-WASP and Mena.
authors.affiliation: Institute of Medical Biology, 8A Biomedical Grove, Immunos, Singapore.
authors.forename: Kim Buay
authors.initials: KB
authors.lastname: Lim
authors.forename: Wenyu
authors.initials: W
authors.lastname: Bu
authors.forename: Wah Ing
authors.initials: WI
authors.lastname: Goh
authors.forename: Esther
authors.initials: E
authors.lastname: Koh
authors.forename: Siew Hwa
authors.initials: SH
authors.lastname: Ong
authors.forename: Tony
authors.initials: T
authors.lastname: Pawson
authors.forename: Thankiah
authors.initials: T
authors.lastname: Sudhaharan
authors.forename: Sohail
authors.initials: S
authors.lastname: Ahmed
mesh_terms: D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D006224:Cricetinae; D000080865:Formins; D006801:Humans; D013058:Mass Spectrometry; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D011554:Pseudopodia / Q000378:metabolism*; D051316:Wiskott-Aldrich Syndrome Protein / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C491464:Diap1 protein, mouse; D000080865:Formins; D009419:Nerve Tissue Proteins; D051316:Wiskott-Aldrich Syndrome Protein; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein