Full activation of WASP, not N-WASP, by Cdc42 and PIP2 requires Cdc42 prenylation.

Abstract

WASP and N-WASP are homologous proteins that require the binding of multiple regulators, including the acidic lipid PIP2 and the small GPTase Cdc42, to relieve auto-inhibition before they can stimulate the initiation of actin polymerization. Little is known about how a single intrinsically disordered protein, WASP or N-WASP, binds multiple regulators to achieve full activation. Here we used molecular dynamics simulations to characterize the binding of WASP and N-WASP with PIP2 and Cdc42. In the absence of Cdc42, both WASP and N-WASP strongly associate with PIP2-containing membranes, through their basic region and also possibly through a tail portion of the upstream WH1 domain. The basic region also participates in Cd42 binding, especially for WASP; consequently, Cdc42 binding significantly compromises the ability of WASP, but not N-WASP, to bind PIP2. PIP2 binding of WASP is restored only when Cdc42 is prenylated at the C-terminus and tethered to the membrane. This distinction in the full activation of WASP and N-WASP may contribute to their different function roles.