Regulation of Src trafficking and activation by the endocytic regulatory proteins MICAL-L1 and EHD1

Abstract

Localization of the non-receptor tyrosine kinase Src to the cell periphery is required for its activation and to mediate focal adhesion turnover, cell spreading and migration. Inactive Src localizes to a perinuclear compartment and the movement of Src to the plasma membrane is mediated by endocytic transport. However, the precise pathways and regulatory proteins that are responsible for SRC transport are incompletely understood. Here, we demonstrate that Src partially colocalizes with the endocytic regulatory protein MICAL-L1 (molecule interacting with CasL-like protein 1) in mammalian cells. Furthermore, MICAL-L1 is required for growth-factor- and integrin-induced Src activation and transport to the cell periphery in HeLa cells and human fibroblasts. Accordingly, MICAL-L1 depletion impairs focal adhesion turnover, cell spreading and cell migration. Interestingly, we find that the MICAL-L1 interaction partner EHD1 (EH domain-containing protein 1) is also required for Src activation and transport. Moreover, the MICAL-L1-mediated recruitment of EHD1 to Src-containing recycling endosomes is required for the release of Src from the perinuclear endocytic recycling compartment in response to growth factor stimulation. Our study sheds new light on the mechanism by which Src is transported to the plasma membrane and activated, and provides a new function for MICAL-L1 and EHD1 in the regulation of intracellular non-receptor tyrosine kinases.