부산대학교 도서관

One of the mechanisms shaping the pathophysiology during the infection of enteric pathogen Salmonella Typhimurium is host PTM machinery utilization by the pathogen encoded effectors. Salmonella Typhimurium (S. Tm) during infection in host cells thrives in a vacuolated compartment, Salmonella containing vacuole (SCV), which sequentially acquires host endosomal and lysosomal markers. Long tubular structures, called as Salmonella induced filaments (SIFs), are further generated by S. Tm, which are known to be required for SCV's nutrient acquisition, membran maintenance and stability. A tightly coordinated interaction involving prominent effector SifA and various host adapters PLEKHM1, PLEKHM2 and Rab GTPases govern SCV integrity and SIF formation. Here, we report for the first time that the functional regulation of SifA is modulated by PTM SUMOylation at its 11th lysine. S. Tm expressing SUMOylation deficient lysine 11 mutants of SifA (SifAK11R) is defective in intracellular proliferation due to compromised SIF formation and enhanced lysosomal acidification. Furthermore, murine competitive index experiments reveal defective in vivo proliferation and weakened virulence of SifAK11R mutant. Concisely, our data reveal that SifAK11R mutant nearly behaves like a SifA knockout strain which impacts Rab9-MPR mediated lysosomal acidification pathway, the outcome of which culminates in reduced bacterial load in in vitro and in vivo infection model systems. Our results bring forth a novel pathogen-host crosstalk mechanism where the SUMOylation of effector SifA regulated S. Tm intracellular survival. Author summary: Effectors are specialized proteins produced by bacteria that enable their entry, colonization, and survival within host. The effectors cross-talk with host molecular pathways for ensuring successful infection. Current study focuses on one such event during infection by gastroenteritis causing bacterial pathogen, Salmonella Typhimurium (S. Tm). During invasion, S. Tm develops a vacuole around itself with host membranes resulting in a protective structure called Salmonella Containing Vacuole (SCV). By effector function, particularly that of Salmonella induced filament protein A (SifA), it is known that SCVs evade lysosome mediated degradation in host cell. To issue these outcomes, SifA interacts and interferes with multiple host proteins. However, the details of these mechanisms are not fully understood. In eukaryotic cells, synthesized proteins undergo modifications collectively referred as 'Post Translational Modifications' PTMs, which diversifies their functionality. Here we tested if SifA utilizes one such host PTM machinery, i.e., SUMOylation for its function. Using cell culture and mice model we show PTM modification of SifA by SUMOylation. Salmonella encoding a SUMOylation defective SifA shows several weaknesses including a compromised SCV formation, enhanced lysosomal killing and reduced fitness. Thus, this work brings forth a novel bacterial mechanism, involving SUMOylation of effector SifA, required for Salmonella pathogenesis. [ABSTRACT FROM AUTHOR]