IRSp53 Links the Enterohemorrhagic E. coli Effectors Tir and EspFU for Actin Pedestal Formation

SummaryActin pedestal formation by pathogenic E. coli requires signaling by the bacterial intimin receptor Tir, which induces host cell actin polymerization mediated by N-WASP and the Arp2/3 complex. Whereas canonical enteropathogenic E. coli (EPEC) recruit these actin regulators through tyrosine kinase signaling cascades, enterohemorrhagic E. coli (EHEC) O157:H7 employ the bacterial effector EspFU (TccP), a potent N-WASP activator. Here, we show that IRSp53 family members, key regulators of membrane and actin dynamics, directly interact with both Tir and EspFU. IRSp53 colocalizes with EspFU and N-WASP in actin pedestals. In addition, targeting of IRSp53 is independent of EspFU and N-WASP but requires Tir residues 454–463, previously shown to be essential for EspFU-dependent actin assembly. Genetic and functional loss of IRSp53 abrogates actin assembly mediated by EHEC. Collectively, these data indentify IRSp53 family proteins as the missing host cell factors linking bacterial Tir and EspFU in EHEC pedestal formation