EPEC LpxR and the Type III Secretion System

Enteropathogenic E. coli (EPEC) is a Gram-negative pathogen which attaches to the intestinal epithelium of the host and deploys a type III secretion system (T3SS) to inject effector proteins into the cytoplasm of infected cells. When looking for genes which are co-regulated at the transcriptional level with the T3SS genes of EPEC, we identified lpxR which is embedded in a prophage. The encoded protein, LpxR, is an outer membrane beta barrel protein with a lipid A 3’-O-deacylation enzymatic activity. Previous reports on LpxR in other gram-negative pathogens, focus on its impact on host-recognition since the deacetylation of LPS reduces its detection by TLR4. Intriguingly, our results suggest that T3SS inhibits the exposure of wild type LpxR to antibodies. This exposure required LpxR to be enzymatically active. Moreover, T3SS function itself seems to be influenced by LpxR. Therefore, our work is now focusing on deciphering the interplay between T3SS and LpxR and its importance for EPEC virulence.