Arginine GlcNAcylation of Rab small GTPases by the pathogen Salmonella Typhimurium.

Salmonella enterica serovar Typhimurium, an intracellular Gram-negative bacterial pathogen, employs two type III secretion systems to deliver virulence effector proteins to host cells. One such effector, SseK3, is a Golgi-targeting arginine GlcNAc transferase. Here, we show that SseK3 colocalizes with cis-Golgi via lipid binding. Arg-GlcNAc-omics profiling reveals that SseK3 modifies Rab1 and some phylogenetically related Rab GTPases. These modifications are dependent on C-termini of Rabs but independent of the GTP- or GDP-bound forms. Arginine GlcNAcylation occurs in the switch II region and the third α-helix and severely disturbs the function of Rab1. The arginine GlcNAc transferase activity of SseK3 is required for the replication of Salmonella in RAW264.7 macrophages and bacterial virulence in the mouse model of Salmonella infection. Therefore, this SseK3 mechanism of action represents a new understanding of the strategy adopted by Salmonella to target host trafficking systems. Meng, Zhuang, Peng et al. study the role of a Golgi-targeting arginine GlcNAc transferase, SseK3, in the pathogenesis of Salmonella enterica. Through R-GlcNAcylated proteome analysis, they identify Rab proteins as targets for SseK3 as well as their modification sites. They demonstrate that SseK3 GlcNAc transferase activity is required for bacterial virulence in vitro and in vivo.