OtDUB from the Human Pathogen Orientia tsutsugamushi Modulates Host Membrane Trafficking by Multiple Mechanisms

Abstract

Host cell membrane-trafficking pathways are often manipulated by bacterial pathogens to gain cell entry, avoid immune responses, or to obtain nutrients. The 1,369-residue OtDUB protein from the obligate intracellular human pathogen Orientia tsutsugamushi bears a deubiquitylase (DUB) and additional domains. Host cell membrane-trafficking pathways are often manipulated by bacterial pathogens to gain cell entry, avoid immune responses, or to obtain nutrients. The 1,369-residue OtDUB protein from the obligate intracellular human pathogen Orientia tsutsugamushi bears a deubiquitylase (DUB) and additional domains. Here we show that OtDUB ectopic expression disrupts membrane trafficking through multiple mechanisms. OtDUB binds directly to the clathrin adaptor-protein (AP) complexes AP-1 and AP-2, and the OtDUB(275-675) fragment is sufficient for binding to either complex. To assess the impact of OtDUB interactions with AP-1 and AP-2, we examined trans-Golgi trafficking and endocytosis, respectively. Endocytosis is reduced by two separate OtDUB fragments: one contains the AP-binding domain (OtDUB(1-675)), and the other does not (OtDUB(675-1369)). OtDUB(1-675) disruption of endocytosis requires its ubiquitin-binding capabilities. OtDUB(675-1369) also fragments trans- and cis-Golgi structures. Using a growth-based selection in yeast, we identified viable OtDUB(675-1369) point mutants that also no longer caused Golgi defects in human cells. In parallel, we found OtDUB(675-1369) binds directly to phosphatidylserine, and this lipid binding is lost in the same mutants. Together these results show that OtDUB contains multiple activities capable of modulating membrane trafficking. We discuss how these activities may contribute to Orientia infections.