The Brucella Effector Grhg1 Reprograms the Host N-Glycome to Sustain Infection

Abstract

The intracellular bacterium Brucella is a globally distributed pathogen that causes brucellosis, a disease of wildlife, domesticated animals, and humans. The virB Type IV secretion system (virB-T4SS) plays an essential role in bacterial pathogenesis, in part through the secretion into host cells of effector proteins that modulate host cell functions to promote pathogen survival, replication and persistence. To date, several virB-T4SS effectors have been identified and characterized in Brucella abortus, however no B. melitensis effector proteins have been identified or shown to play a role in bacterial pathogenesis. Here, we describe the identification and characterization of a novel effector protein BMEI1482 (Grhg1) that is translocated into macrophages in a virB-T4SS dependent fashion. Mechanistic studies revealed that Grhg1 reprograms glycosylation by binding proteins in the oligosaccharide transferase (OST) complex. Importantly, B. melitensis Grhg1 gene promotes bacterial replication in vitro and in vivo demonstrating its important role to sustain infection. Taken together, these findings provide mechanistic insights into B. melitensis intracellular lifecycle and demonstrate that this bacterium disrupts cell functions to promote pathogenesis through virB-T4SS effector proteins. In addition, this work provides a new paradigm for glycoproteome reprograming as a target for Brucella manipulation of host functions to promote disease.