Characterization of a secretory hydrolase from Mycobacterium tuberculosis sheds critical insight into host lipid utilization by M. tuberculosis

Abstract

causes tuberculosis in humans and predominantly infects alveolar macrophages. To survive inside host lesions and to evade immune surveillance, this pathogen has developed many strategies. For example, uses host-derived lipids/fatty acids as nutrients for prolonged persistence within hypoxic host microenvironments. imports these metabolites through its respective transporters, and in the case of host fatty acids, a pertinent question arises: does have the enzyme(s) for cleavage of fatty acids from host lipids? We show herein that a previously uncharacterized membrane-associated protein encoded by is conserved exclusively in actinomycetes, exhibits both lipase and protease activities, is secreted into macrophages, and catalyzes host lipid hydrolysis. In light of these functions, we annotated Rv2672 as mycobacterial secreted hydrolase 1 (Msh1). Furthermore, we found that this enzyme is up-regulated both in an model of hypoxic stress and in a mouse model of infection, suggesting that the pathogen requires Msh1 under hypoxic conditions. Silencing Msh1 expression compromised the ability of to proliferate inside lipid-rich foamy macrophages but not under regular culture conditions , underscoring Msh1's importance for persistence in lipid-rich microenvironments. Of note, this is the first report providing insight into the mechanism of host lipid catabolism by an enzyme, augmenting our current understanding of how meets its nutrient requirements under hypoxic conditions.

Mycobacterium tuberculosis: Rewiring host cell signaling to promote infection

“…Recent work showed that M. tuberculosis secretes a membrane-associated hydrolytic protein (Msh1) into macrophages under hypoxic stress. 48 Msh1 is expressed during infection in vivo, and functions to catalyze host lipid hydrolysis. Thus, M. tuberculosis has devised strategies to both stockpile essential nutrients in the form of lipid bodies, as well as to tap into these reserves as required, perhaps during reactivation from latency.…”

“…However, little attention has been given to how the pathogen mobilizes host TAG stores in order to import the fatty acids into the bacteria. Recent work showed that M. tuberculosis secretes a membrane‐associated hydrolytic protein (Msh1) into macrophages under hypoxic stress . Msh1 is expressed during infection in vivo , and functions to catalyze host lipid hydrolysis.…”

Transcriptional Profile of Mycobacterium tuberculosis in an in vitro Model of Intraocular Tuberculosis

“…Thus, the upregulation of transcripts whose protein products are involved in these metabolic activities (Supplementary Table 3 ) highlights the active metabolic physiological state of bacteria inside the host environment during replication. Rv2672 encodes for a mycobacterial secretory protein with lipase and protease activities and hydrolyzes the host lipid for its nutrient requirements and helps in survival of M. tuberculosis inside lipid-rich foamy macrophages (Singh et al, 2017 ). Genes ( Rv0462 : lpdC and Rv1005c : pabB ) of folate biosynthesis are predicted to be essential for mycobacterial survival (Griffin et al, 2011 ) and enzymes of folate metabolism are targets of potent antitubercular agents (Minato et al, 2015 ).…”

Microbial esterases and ester prodrugs: An unlikely marriage for combating antibiotic resistance

“…LipY could make a good partner for prodrug esters, as it has a wide substrate specificity but a well‐defined structure–activity relationship (Delorme et al, ; Satpati, Behera, & Dixit, ; Saxena et al, ). Recently, Msh1 (mycobacterial secreted hydrolase) was identified as a second TAG hydrolyzing esterase, which is specific for host–lipid hydrolysis (Singh et al, ). Because it targets host lipids, catalyzes ester hydrolysis outside Mtb , and is upregulated during hypoxic conditions, Msh1 could also represent a novel drug target and ester prodrug activating partner (Singh et al, ).…”

“…Recently, Msh1 (mycobacterial secreted hydrolase) was identified as a second TAG hydrolyzing esterase, which is specific for host–lipid hydrolysis (Singh et al, ). Because it targets host lipids, catalyzes ester hydrolysis outside Mtb , and is upregulated during hypoxic conditions, Msh1 could also represent a novel drug target and ester prodrug activating partner (Singh et al, ).…”