Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Actins / metabolism
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Amino Acid Sequence
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Animals
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Biological Transport
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Cells, Cultured
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Cytoplasmic Vesicles / chemistry
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Cytoplasmic Vesicles / metabolism
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Fibroblasts / cytology
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Fibroblasts / physiology
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Mice
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Mice, Knockout
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Molecular Sequence Data
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Nerve Tissue Proteins / chemistry
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism*
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Phosphatidylinositol 4,5-Diphosphate / metabolism*
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Protein Binding
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Rats
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Second Messenger Systems / physiology
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Wiskott-Aldrich Syndrome Protein, Neuronal
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cdc42 GTP-Binding Protein / metabolism
Substances
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Actins
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Nerve Tissue Proteins
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Phosphatidylinositol 4,5-Diphosphate
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Recombinant Fusion Proteins
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Wasl protein, mouse
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Wasl protein, rat
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Wiskott-Aldrich Syndrome Protein, Neuronal
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cdc42 GTP-Binding Protein