Journal
MOLECULAR CELL
Volume 17, Issue 2, Pages 181-191Publisher
CELL PRESS
DOI: 10.1016/j.molcel.2004.11.054
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Funding
- NIGMS NIH HHS [GM66229] Funding Source: Medline
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Phosphatidylinositol 4,5-bisphosphate (PIP2) 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 PIP2 in a multivalent, cooperative manner. As a result, PIP2 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 PIP2 (Hill coefficient n(H) = similar to20). We show that the sharpness of the PIP2 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 PIP2 levels yet leave it poised for activation upon subtle, signaling-induced perturbations in PIP2 distribution.
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