Lipid mediated inhibition of Niemann-Pick C1 protein is an evolutionary conserved feature of multiple Mycobacterium lineages and non-tubercular mycobacteria.
Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis (TB) and is a major cause of human morbidity and mortality. Crucially, Mtb can persist and replicate within host macrophages (MF) and subvert multiple antimicrobial defense mechanisms. How this is achieved is incompletely understood. Previously, we reported that lipids shed by persistent mycobacteria inhibit NPC1, the lysosomal protein deficient in most cases of the rare, inherited lysosomal storage disorder Niemann-Pick disease type C (NPC). Inhibition of NPC1 leads to a drop in lysosomal calcium levels blocking phagosome-lysosome fusion and thereby leads to mycobacterial persistence. Studies of mycobacterial lineages have identified events during mycobacterial evolution that result in the acquisition of persistence. We speculated that the production of specific cell wall lipid(s) capable of inhibiting NPC1 activities could have been a critical step in the evolution of pathogenicity. In this study, we have therefore investigated whether lipid extracts from clinical Mtb strains representative of multiple Mtb lineages, members of the Mtb complex (MTBC) and selected non-tubercular mycobacteria (NTM) inhibit the NPC pathway. We have found that the ability to inhibit the NPC pathway was present in all clinical isolates studied from Mtb lineages 1, 2 and 4. We also found that lipids from MTBC member, Mycobacterium bovis and the NTM, Mycobacterium abscessus and Mycobacterium avium also inhibited the NPC pathway. However, when lipids were assayed from Mycobacterium canettii (M. canettii), a smooth tubercle mycobacterium, which is considered to resemble the common ancestor of the MTBC no inhibition of the NPC1 pathway was detected. We therefore conclude that the evolution of mycobacterial cell wall lipids that inhibit the NPC pathway evolved early and post divergence from M. canettii related mycobacteria and NPC1 inhibition significantly contributes to the ability of these pathogens to persist and cause disease.