Probing important protein interactions in the regulation of cell shape and movement

Abstract

Diaphanous-related Formins (DRF) are a conserved family of proteins that are involved in the coordination of the cytoskeleton, a structure that plays a role in cellular shape, movement, and division. Since the DRFs play an important role in many cellular processes, it is vital that these proteins are tightly regulated and only activated in response to a cellular signal, as uncontrolled DRFs can result in dire consequences for a cell. The regulation of the DRFs centers around the ability of the protein to inhibit itself (autoinhibition). Specifically, the intramolecular interactions between the C-terminal Dia-autoregulatory domain (DAD) and the N-terminal Diaphanous inhibitory domain (DID) keeps the DRF in an “closed” inactive state. Autoinhibition is relieved when a Rho GTPase binds to the GTPase Binding Domain (GBD) and releases the DAD from DID, thereby “opening” the DRF to an active state. Since DID-DAD binding plays a vital role in the regulation of the full length DRF protein, thereby impacting many cellular processes, our laboratory focuses on elucidating these important DID-DAD interactions. Through a combination of protein biochemical, cellular, and molecular biological techniques, undergraduate students have made major contributions in determining specific amino acid residues in conserved regions of both DAD and DID that are critical for mediating DID-DAD binding. In addition, our laboratory has discovered another residue in DID that is not only involved in binding to DAD, but it also harbors a potential role in the cellular localization of the DRF protein.