Role of TOCA proteins in glia: from cellular morphology to animal behavior

SUMMARY Cells use a broad arsenal of proteins to change the curvature of cell membranes. This is important for cell motility, endocytosis, and establishment of cell morphology. As such, it comes as no surprise that components of this machinery are central in the etiology of many diseases, including developmental and immunodeficiency disorders, neurodegenerative conditions, and cancer. One protein family that appears repeatedly at the intersection of membrane biology and disease is the Bin1/Amphiphysin/Rvs family of proteins (BAR proteins). Homologues of this family are found from yeast to humans and are essential for the induction of morphological changes of cells and for the coupling of membrane curvature to actin polymerization. While BAR proteins are proposed to function in these processes, little is known about the structure/function of these proteins in an in vivo context. This gap of knowledge hinders leveraging BAR proteins and their targets for the treatment of cancer and other diseases. A comprehensive model of full-length BAR proteins is needed to perform structure/function analysis in vivo, so physiologically relevant structures can be identified. The goal of this exploratory proposal is twofold: to establish an in vivo model of BAR protein structure/function using the pioneering organism C. elegans (Aim 1), and to use cryoEM/cryoET to identify salient structural motifs in a full-length human BAR protein bound to the membrane in the presence and absence of one of its main targets, the small Rho GTPase CDC42 (Aim 2). The accomplishment of these two aims will provide information on essential structural interfaces and amino acid residues that can be then tested in vivo. Data obtained here will set the groundwork for a comprehensive in vivo determination of BAR protein structure/function that we will pursue in the future. Ultimately, this work will advance our understanding of how cells change morphology in health and disease.