The functional role of the endocytic protein syndapin in controlling actin cytoskeletal organization and dynamics

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The actin cytoskeleton is a complex and highly organized structure, yet it is dynamic and responds to a variety of inner and outer clues. Since actin and the Arp2/3 complex - the actin nucleation machinery - are basic, general components, a specific linkage of cytoskeletal functions to the huge variety of cellular processes actin is involved in will require distinct molecules controlling the Arp2/3 complex. Some of this specificity may be provided by the different Arp2/3 complex activators, the majority of which belong to the Scar/WASP protein family, but most of this specificity may involve a diverse group of proteins interacting with these molecules and controlling them. With syndapins, we have identified proteins that are part of membrane trafficking processes but also interact with the Arp2/3 complex activator N-WASP. In this study, we want to address whether interaction with Scar/WASP superfamily proteins is a general feature of syndapin function, examine the molecular mechanisms by which the syndapin/N-WASP interaction we have previously identified triggers actin polymerization as well as actin-driven motility and conduct a detailed mechanistical analysis of the involved proteins, protein domains and their interactions. For this purpose, we will employ in vitro reconstitution assays using purified proteins. We will also study syndapin- and actin-dependent morphology changes in vivo and try to gain insights into the regulation of the actin nucleation machinery and into the organization of the functional interface of the actin cytoskeleton with cellular membranes.