Mycobacterium tuberculosis sheds an antacid that drives lysosome dysfunction and lipid droplet accumulation

Bedard M1, Bernard E2, van der Niet S3, Aylan B2, Cheng TY1, Buter J4, Minaard A4, van der Wel N3, Gutierrez M2, Moody DB1*

1Brigham and Women’s Hospital/Harvard Medical School, Department of Rheumatology, Inflammation, and Immunology, 60 Fenwood Road, Boston, MA, 02115

2The Francis Crick Institute, 1 Midland Road, London, UK, NW1 1AT

3Amsterdam University Medical Centers, Medical Biology, Meibergdreef 9 1105, Amsterdam, The Netherlands

4Unveristy of Groningen, Faculty of Science and Engineering, 9700 AB Groningen, The Netherlands

The success of Mycobacterium tuberculosis (Mtb) as a pathogen stems from its ability to evade host immune responses by surviving within macrophages. 1-tuberculosinyl adenosine (1-TbAd) is a lysosomotropic compound produced abundantly by virulent Mtb, but not other mycobacterial species. 1-TbAd acts as an antacid, neutralizing and swelling phagolysosomes – the compartment in which intracellular Mtb resides. We recently observed that 1-TbAd-induced lysosomal remodeling is accompanied by inhibition of the acid-activated lysosomal enzymes and accumulation of lipid droplets in M1 macrophages, but not M2 macrophages. We hypothesize that synthetic 1-TbAd, by disrupting lysosome function in host macrophages, will both initiate upstream autophagic signaling required for lysophagy whilst blocking autophagic flux, the final step of autophagic degradation. Using cell biology techniques, live infection models, and transcriptomic profiling, we are dissecting the specific pathways involved in 1-TbAd induced lysosomal dysfunction, including lysophagy. At a later timepoint, we observe intracellular lipid droplet accumulation and fusion by Bodipy staining. Lipidomic analysis at this timepoint indicates a 1-TbAd dose-dependent increase in certain relevant lipid species. A clear understanding of the molecular mechanisms altered in macrophages by 1-TbAd will guide the development of host-directed therapies to control 1-TbAd driven pathogenesis.