The C-terminal proline-rich repeats of Enteropathogenic E. coli effector EspF are sufficient for the depletion of tight junction membrane proteins and interactions with early and recycling endosomes

Abstract

Abstract Background Enteropathogenic E. coli (EPEC) causes acute infantile diarrhea accounting for significant morbidity and mortality in developing countries. EPEC uses a type three secretion system to translocate more than twenty effectors into the host intestinal cells. At least four of these effectors, namely EspF, Map, EspG1/G2 and NleA, are reported to disrupt the intestinal tight junction barrier. We have reported earlier that the expression of EspF and Map in MDCK cells causes the depletion of the TJ membrane proteins and compromises the integrity of the intestinal barrier. In the present study, we have examined the role of the domains within the C-terminus of EspF in the depletion of tight junction proteins and identified key endocytosis markers that interact with EspF.Results We generated mutant EspF proteins which lacked one or more proline-rich repeats (PRRs) at the C-terminus of EspF and examined the effect of their expression on the cellular localization of tight junction membrane proteins. In lysates derived from cells expressing the mutant EspF proteins, we found that the C-terminal PRRs of EspF are sufficient for the depletion of TJ membrane proteins. Pull-down assays revealed that these domains mediate interactions with the TJ adaptor proteins ZO-1 and ZO-2 as well as with the proteins involved in endocytosis such as caveolin-1, Rab5a and Rab11.Conclusions Our study demonstrates the direct role of the proline-rich repeat domains of EspF in the depletion of the TJ proteins and a possible involvement of these domains in the endocytosis of host proteins. New therapeutic strategies can target these PRR domains to prevent intestinal barrier dysfunction in EPEC infections.