Multiple deletions in the polyketide synthase gene repertoire ofMycobacterium tuberculosisreveal functional overlap of cell envelope lipids in host-pathogen interactions

Abstract

SummarySeveral specific lipids of the cell envelope are implicated in the pathogenesis of M. tuberculosis (Mtb), including phthiocerol dimycocerosates (DIM) that have clearly been identified as virulence factors. Others, such as trehalose-derived lipids, sulfolipids (SL), diacyltrehaloses (DAT) and polyacyltrehaloses (PAT), are believed to be essential for Mtb virulence, but the details of their role remain unclear. We therefore investigated the respective contribution of DIM, DAT/PAT and SL to tuberculosis by studying a collection of mutants, each with impaired production of one or several lipids. We confirmed that among those with a single lipid deficiency, only strains lacking DIM were affected in their replication in lungs and spleen of mice in comparison to the WT Mtb strain. We found also that the additional loss of DAT/PAT, and to a lesser extent of SL, increased the attenuated phenotype of the DIM-less mutant. Importantly, the loss of DAT/PAT and SL in a DIM-less background also affected Mtb growth in human monocyte-derived macrophages (hMDMs). Fluorescence microscopy revealed that mutants lacking DIM or DAT/PAT were localized in an acid compartment and that bafilomycin A1, an inhibitor of phagosome acidification, rescued the growth defect of these mutants. These findings provide evidence for DIM being dominant virulence factors that mask the functions of lipids of other families, notably DAT/PAT and to a lesser extent of SL, which we showed for the first time to contribute to Mtb virulence.

The rv1184c Locus Encodes Chp2, an Acyltransferase in Mycobacterium tuberculosis Polyacyltrehalose Lipid Biosynthesis

“…On the other hand, in sulfolipid 1 biosynthesis, when Chp1 is absent, the diacylated sulfotrehalose intermediate SL 1278 (also known as Ac 2 SGL) is detected at the cell surface, suggesting that MmpL8 is capable of transporting this intermediate in addition to SL-1 and shares the ability to transport multiple substrates with MmpL10, which is a closely related homologue (58% sequence identity). Interestingly, both mmpL10 and chp2 have been characterized as essential M. tuberculosis genes in vivo (44), but an M. tuberculosis strain disrupted in pks3/4 (and therefore lacking all PAT-related acyltrehaloses) was not attenuated for growth in a mouse infection (45). These data suggest that the accumulation of DAT compromises M. tuberculosis survival in vivo.…”

CpsA, a LytR-CpsA-Psr Family Protein in Mycobacterium marinum, Is Required for Cell Wall Integrity and Virulence

“…The cell envelopes of mycobacteria can contribute significantly to their virulence, and many mycobacterial mutants that possess an impaired cell envelope show attenuated virulence in vitro or in vivo (22,(40)(41)(42)(43)(44)(45)(46). A previous study comprehensively identified the genes required by M. tuberculosis for optimal growth by using transposon sequencing (Tnseq), and those investigators speculated that Rv3484 (cpsA) is an essential gene for M. tuberculosis growth in vivo (47).…”

Protein expression of Myt272-3 recombinant clone and in silico prediction of a possible vaccine candidate against <i>Mycobacterium tuberculosis</i>

“…It has been reported that polyketide synthase is involved in the biosynthesis of unique cell surface lipids; Mycobacterium tuberculosis cell envelope contain the cell surface lipids that link the host and the pathogen [21]. Phthiocerol and phenolphthiocerol diesters were reported also as important virulence factors of the two main mycobacterial pathogens (M. tuberculosis and L. leprae) in human [22].…”