Rv2037c, a stress induced conserved hypothetical protein of Mycobacterium tuberculosis, is a phospholipase: Role in cell wall modulation and intracellular survival

The genome of Mycobacterium tuberculosis encode for several hypothetical proteins that needed to be characterized. Rv2037c, a hypothetical protein, was 25 and 4 folds upregulated under acidic and nutritive stress, respectively in M. tuberculosis H37Ra. The protein demonstrated lipolytic activity with pNP-decanoate with optimum pH 8.0 and temperature 40 degrees C. In addition, the protein demonstrated phospholipase activity. To understand the effect of rv2037c on mycobacterium physiology, the gene was cloned and expressed in M. smegmatis. The protein was found in membrane and extracellular fraction. The expression of rv2037c in M. smegmatis (MS_Rv2037c) altered colony morphology and cell surface features like enhanced biofilm and pellicle formation. MS_Rv2037c decreased cell-wall permeability, enhanced TDM content, resistance against various stresses and antibiotics. MS_Rv2037c demonstrated better infection and intracellular survival capability in infected THP-1 macrophage. Macrophages treated with Rv2037c demonstrated irregular cell membrane. Mice infected with MS_Rv2037c had higher bacterial load in lung, liver and spleen compared to control. Rv2037c induced the production of pro-inflammatory cytokines TNF alpha and IL12, suggesting its role in immune-modulation. Recombinant protein also generated humoral response in EPTB and MDR-TB patients. The results pointed towards the audal role of this enzyme in cell-wall modulation, infection and intracellular survival of mycobacterium. (C) 2020 Published by Elsevier B.V.