EspC translocation into epithelial cells by enteropathogenic Escherichia coli requires a concerted participation of type V and III secretion systems.
EspC is a non-locus of enterocyte effacement (LEE)-encoded autotransporter protein secreted by enteropathogenic Escherichia coli (EPEC) that causes a cytopathic effect on epithelial cells, including cytoskeletal damage. EspC cytotoxicity depends on its internalization and functional serine protease motif. Here we show that during EPEC infection, EspC is secreted from the bacteria by the type V secretion system (T5SS) and then it is efficiently translocated into the epithelial cells through the type III secretion system (T3SS) translocon. By dissecting this mechanism, we found that EspC internalization during EPEC-host cell interaction occurs after 1 h, unlike purified EspC (8 h). LEE pathogenicity island is involved in specific EspC translocation as three espC-transformed attaching and effacing (AE) pathogens translocated EspC into the cells. A role for effectors and other factors involved in the intimate adherence encoded in LEE were discarded by using an exogenous EspC internalization model. In this model, an isogenic EPEC DeltaespC strain allows the efficient internalization of purified EspC. Moreover, isogenic mutants in T3SS were unable to translocate endogenous and exogenous EspC into epithelial cells, as EspC-EspA interaction is required. These data show for the first time the efficient delivery of an autotransporter protein inside the epithelial cells by EPEC, through cooperation between T5SS and T3SS.
Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Ap. Postal 14-740, 07000 México City, Mexico.
Jorge E
JE
Vidal
Fernando
F
Navarro-García
D002460:Cell Line; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D044404:Genomic Islands; D006801:Humans; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D013997:Time Factors
D029968:Escherichia coli Proteins; C102051:EspA protein, E coli; C102541:EspC protein, E coli; C457340:LEE protein, E coli; D010750:Phosphoproteins