ABSTRACTMycobacterium tuberculosis, the causative agent of tuberculosis (TB), remains a significant cause of morbidity and mortality worldwide, despite the availability of a live attenuated vaccine and anti-TB antibiotics. The vast majority of individuals infected withM. tuberculosisdevelop an asymptomatic latent infection in which the bacterium survives within host-generated granulomatous lesions in a physiologically altered metabolic state of nonreplicating persistence. The granuloma represents an adverse environment, asM. tuberculosisis exposed to various stressors capable of disrupting the essential constituents of the bacterium. In Gram-negative and Gram-positive bacteria, resistance to cell envelope stressors that perturb the plasma membrane is mediated in part by proteins comprising the phage shock protein (Psp) system. PspA is an important component of the Psp system; in the presence of envelope stress, PspA localizes to the inner face of the plasma membrane, homo-oligomerizes to form a large scaffold-like complex, and helps maintain plasma membrane integrity to prevent a loss of proton motive force.M. tuberculosisand other members of theMycobacteriumgenus are thought to encode a minimal functional unit of the Psp system, including an ortholog of PspA. Here, we show that Rv2744c possesses structural and physical characteristics that are consistent with its designation as a PspA family member. However, althoughRv2744cis upregulated under conditions of cell envelope stress, loss ofRv2744cdoes not alter resistance to cell envelope stressors. Furthermore, Rv2744c localizes to the surface of lipid droplets inMycobacteriumspp. and regulates lipid droplet number, size, andM. tuberculosispersistence during anaerobically induced dormancy. Collectively, our results indicate that Rv2744c is a bona fide ortholog of PspA that may function in a novel role to regulate lipid droplet homeostasis and nonreplicating persistence (NRP) inM. tuberculosis.IMPORTANCEMycobacterium tuberculosisis the causative agent of tuberculosis, a disease associated with significant morbidity and mortality worldwide.M. tuberculosisis capable of establishing lifelong asymptomatic infections in susceptible individuals and reactivating during periods of immune suppression to cause active disease. The determinants that are important for persistent infection ofM. tuberculosisor for reactivation of this organism from latency are poorly understood. In this study, we describe our initial characterizations of Rv2744c, an ortholog of phage shock protein A (PspA) that regulates the homeostasis of lipid bodies and nonreplicating persistence inM. tuberculosis. This function of PspA inM. tuberculosisis novel and suggests that PspA may represent a unique bacterial target upon which to base therapeutic interventions against this organism.
Drosophila Snazarus Regulates a Lipid Droplet Population at Plasma Membrane-Droplet Contacts in Adipocytes
