Sla2p is associated with the yeast cortical actin cytoskeleton via redundant localization signals

Sla2p, also known as End4p and Mop2p, is the founding member of a widely co nserved family of actin-binding proteins, a distinguishing feature of which is a C-terminal region homologous to the C terminus of talin. These protei ns may function in actin cytoskeleton-mediated plasma membrane remodeling. A human homologue of Sla2p binds to huntingtin, the protein whose mutation results in Huntington's disease. Here we establish by immunolocalization th at Sla2p is a component of the yeast cortical actin cytoskeleton. Deletion analysis showed that Sla2p contains two separable regions, which can mediat e association with the cortical actin cytoskeleton, and which can provide S la2p function. One localization signal is actin based, whereas the other si gnal is independent of filamentous actin. Biochemical analysis showed that Sla2p exists as a dimer in vivo. Two-hybrid analysis revealed two intramole cular interactions mediated by coiled-coil domains. One of these interactio ns appears to underlie dimer formation. The other appears to contribute to the regulation of Sla2p distribution between the cytoplasm and plasma membr ane. The data presented are used to develop a model for Sla2p regulation an d interactions.