Abstract
Enteropathogenic Escherichia coli (EPEC) strains are extracellular pathogens that generate actin-rich structures (pedestals) beneath the adherent bacteria as part of their virulence strategy. Pedestals are hallmarks of EPEC infections, and their efficient formation in vitro routinely requires phosphorylation of the EPEC effector protein Tir at tyrosine 474 (Y474). This phosphorylation results in the recruitment and direct attachment of the host adaptor protein Nck to Tir at Y474, which is utilized for actin nucleation through a downstream N-WASP-Arp2/3-based mechanism. Recently, the endocytic protein clathrin was demonstrated to be involved in EPEC pedestal formation. Here we examine the organization of clathrin in pedestals and report that CD2AP, an endocytosis-associated and cortactin-binding protein, is a novel and important component of EPEC pedestal formation that also utilizes Y474 phosphorylation of EPEC Tir. We also demonstrate the successive recruitment of Nck and then clathrin prior to actin polymerization at pedestals during the Nck-dependent pathway of pedestal formation. This study further demonstrates that endocytic proteins are key components of EPEC pedestals and suggests a novel endocytosis subversion strategy employed by these extracellular bacteria.