| The movement of individual cells is required for numerous cellular functions, such as morphogenesis, immune response, and tracking towards specific signals. One well-studied pathway eukaryotic cells utilize to change shape and move results in the polymerization of actin filaments from monomers of actin within the cytosol of a cell. Wiskott-Aldrich Syndrome protein (WASp) family members link signaling pathways to dynamic changes in the actin cytoskeleton. The proteins in this family are multi-domain containing proteins, and the protein family is highly conserved from amoeba to mammals. Scar, a WASp family protein, was first discovered in our laboratory in a genetic screen using Dictyostelium discoideum. Since the identification of Scar over 7 years ago, numerous studies have described the role of Scar in actin polymerization and cell motility. Few studies have been directed at understanding the regulation of Scar at a molecular level. My dissertation research is aimed at detailing the molecular mechanisms that regulate Scar.;Recent data from our lab and others suggest that Scar exists in, and may be regulated by, a protein complex containing four additional proteins - HSPC300, Nap1, PIR121, and Abi. Orthologues of protein complex partners HSPC300, Nap1, Abi, and PIR121 exist in Dictyostelium discoideum. Based on the evolutionary conservation of the proteins, we tested the hypothesis that Scar localization and function is regulated in Dictyostelium by a complex containing these proteins. In vitro experimentation shows Scar directly binds two proteins found in the Scar containing large molecular weight complex, HSPC300 and Abi, and a short region of Scar encompassing the first 96 amino acids is both necessary and sufficient for interaction with HSPC300 and Abi in vitro.;The biological significance of the HSPC300 and Abi binding site of Scar in cells was examined by observing Dictyostelium discoideum cell lines that express a Scar protein that is deleted for amino acids 1-96. Data presented here show that the first 96 amino acids of Scar, and presumably the interaction of Scar with Abi and/or HSPC300, are necessary for participation in a large molecular weight protein complex, proper localization, proper regulation, and normal actin cytoarchitecture and dynamics within cells. |
