A polybasic motif allows N-WASP to act as a sensor of PIP(2) density.
Phosphatidylinositol 4,5-bisphosphate (PIP(2)) activates the actin regulatory protein N-WASP by binding to a short polybasic region involved in N-WASP autoinhibition. Here, we show that unlike canonical lipid binding modules, such as PH domains, this polybasic motif binds PIP(2) in a multivalent, cooperative manner. As a result, PIP(2) activation of N-WASP-mediated actin polymerization in vitro and in extracts is ultrasensitive: above a certain threshold, N-WASP responds in a switch-like manner to a small increase in the density of PIP(2) (Hill coefficient n(H) = approximately 20). We show that the sharpness of the PIP(2) activation threshold can be tuned by varying the length of the polybasic motif. This sharp activation threshold may help suppress N-WASP activation by quiescent PIP(2) levels yet leave it poised for activation upon subtle, signaling-induced perturbations in PIP(2) distribution.
Papayannopoulos
Venizelos
V
Department of Cellular and Molecular Pharmacology and Program in Biological Sciences, University of California, San Francisco, San Francisco, CA 94143, USA.
Co
Carl
C
Prehoda
Kenneth E
KE
Snapper
Scott
S
Taunton
Jack
J
Lim
Wendell A
WA
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D011993:Recombinant Fusion Proteins; C495772:Wasl protein, mouse; C495770:Wasl protein, rat; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D020764:cdc42 GTP-Binding Protein