Actin assembly mediated by Arp2/3 complex and WASP family proteins

Abstract

This chapter describes an actin assembly mediated by Arp2/3 complex and WASP family proteins. The Arp2/3 complex is known to be regulated in cells by a direct interaction with WASP family proteins. These proteins have been shown biochemically to stimulate the nucleation activity of the complex in vitro . The chapter presents a signal-dependent actin assembly mechanism from purified components. Based on genetic and cell biological data, this mechanism appears to represent a cellular signaling pathway for de novo nucleation of actin filaments. The chapter describes various reconstituted systems that are extremely powerful tools for studying signal-dependent actin assembly. The technical challenges in studying such a reconstituted system are to obtain highly purified proteins from a homogeneous tissue source, to collect meaningful data, and to analyze data correctly. The chapter describes various methods that have been used in the laboratories to characterize the nucleation activity of the Arp2/3 complex and its regulation by WASP family proteins. These methods can be applied to many systems for the study of actin dynamics. The chapter concludes with a description of the model-dependent analysis using KINSIM for studying the mechanism of actin polymerization.