Regulation of Rab5 Function during Phagocytosis of Live Pseudomonas aeruginosa in Macrophages

Abstract

ABSTRACTPseudomonas aeruginosa, a Gram-negative opportunistic human pathogen, is a frequent cause of severe hospital-acquired infections. Effectors produced by the type III secretion system disrupt mammalian cell membrane trafficking and signaling and are integral to the establishment ofP. aeruginosainfection. One of these effectors, ExoS, ADP-ribosylates several host cell proteins, including Ras and Rab GTPases. In this study, we demonstrated that Rab5 plays a critical role during early stages ofP. aeruginosainvasion of J774-Eclone macrophages. We showed that live, but not heat-inactivated,P. aeruginosainhibited phagocytosis and that this occurred in conjunction with downregulation of Rab5 activity. Inactivation of Rab5 was dependent on ExoS ADP-ribosyltransferase activity, and in J744-Eclone cells, ExoS ADP-ribosyltransferase activity caused a more severe inhibition of phagocytosis than ExoS Rho GTPase activity. Furthermore, we found that expression of Rin1, a Rab5 guanine exchange factor, but not Rabex5 and Rap6, partially reversed the inactivation of Rab5 during invasion of liveP. aeruginosa. These studies provide evidence that liveP. aeruginosacells are able to influence their rate of phagocytosis in macrophages by directly regulating activation of Rab5.