Phospholipid homeostasis, membrane tenacity and survival of Mtb in lipid rich conditions is determined by MmpL11 function

Abstract

The mycobacterial cell wall is a chemically complex array of molecular entities that dictate the pathogenesis of Mycobacterium tuberculosis. Biosynthesis and maintenance of this dynamic entity in mycobacterial physiology is still poorly understood. Here we demonstrate a requirement for M. tuberculosis MmpL11 in the maintenance of the cell wall architecture and stability in response to surface stress. In the presence of a detergent like Tyloxapol, a mmpL11 deletion mutant suffered from a severe growth attenuation as a result of altered membrane polarity, permeability and severe architectural damages. This mutant failed to tolerate permissible concentrations of cis-fatty acids suggesting its increased sensitivity to surface stress, evident as smaller colonies of the mutant outgrown from lipid rich macrophage cultures. Additionally, loss of MmpL11 led to an altered cellular fatty acid flux in the mutant: reduced incorporation into membrane cardiolipin was associated with an increased flux into the cellular triglyceride pool. This increase in storage lipids like triacyl glycerol (TAG) was associated with the altered metabolic state of higher dormancy-associated gene expression and decreased sensitivity to frontline TB drugs. This study provides a detailed mechanistic insight into the function of mmpL11 in stress adaptation of mycobacteria.

Modern clinical Mycobacterium tuberculosis strains leverage type I IFN pathway for a pro-inflammatory response in the host

“…Expression of ESAT6 in the culture filtrate and secreted Mtb cultures was performed by immunoblotting with anti ESAT6 monoclonal antibody HYB76-8 as described earlier ( 3 ). The mmpL 8 null mutant (δM8) was created by homologous recombination using specialized transduction and recombineering as described earlier ( 50 ). Transducing phages generate by recombineering mediated generation of phages were used for transduction of Wt Erdman Mtb cultures and hyg R colonies were screened for deletion by qPCR and checking expression of sulfolipid in apolar lipid fractions by TLC as per recommended protocols ( 51 ).…”

“…All the cell lines used were tested for mycoplasma contamination at regular intervals and cultured according to the manufacturer’s recommendations. THP1 cells were grown in HiglutaXL RPMI-1640 (Himedia laboratories, India) with 10% FBS and differentiated by using PMA as described earlier ( 50 ). Human monocyte derived macrophages (MDMs) were isolated from 20ml as described earlier ( 49 ).…”

“…Macrophage cultures were seeded at the requisite density and infected with single cell suspensions (SCS) as described earlier ( 50 ). At different time intervals, the cells/ RNA/ supernatants were harvested and used for analysis.…”

Fatty acids of lipids of blood serum and liver of rats with tetracyclin-induced hepatosis and at correction

“…Among the toxic compounds causing structural and functional changes in the liver in the form of fatty hepatosis, antibiotics (primarily the tetracycline series), which are often used in the treatment of various diseases, dominate (Madian, 2015). Despite the successes achieved in providing pharmacological correction of structural, functional and metabolic changes in the mammalian organism during liver pathology, the issues of violation of the composition of fatty acids and their functional role in the development of fatty degeneration are insufficiently studied (Bothra et al, 2018;Calitz et al, 2018;Kagebeck et al, 2018).…”

“…It is known that phospholipid molecules are powerful factors in cellular repair, and can also serve as precursors of secondary messengers (Udut et al, 2013;Quinn, 2014;Yang et al, 2018). Many facts have now been accumulated about the participation of phospholipids in the activation of signal transduction processes in various pathological conditions, which has become the basis for the development of new drugs (Bothra et al, 2018;Colombo et al, 2018).…”