Characterization of phosphatidic acid phosphatase enzymes in mycobacteria

GRAMAJO, H; CROTTA ASIS, A; GAGO, G.

Buenos Aires

Congreso; SAIB 2017; 2017

One of the most striking features of the tuberculosis (TB)granuloma is the presence around the lesion of a specific populationof macrophages enriched in lipid droplets known as foamy macrophages(FM). Within FM, Mycobacterium tuberculosis decreases itsmultiplication rate and accumulates intracytoplasmic lipid inclusions(ILI) in its own cytoplasm which consist mainly of triacylglycerides(TAG). However, the mechanisms by which M. tuberculosis inducesthe differentiation of these FM and by which ILI accumulates in theircytoplasm within infected cells are not known.The main biosynthetic pathway for TAG synthesis involves thesequential esterification of glycerol-3-phosphate to produce phosphatidicacid (PA). In M. tuberculosis, the PA can be dephosphorylatedby a phosphatidic acid phosphatase enzyme (PAP) giving diacylglycerol(DAG), which is the direct precursor of TAG synthesis.Therefore, DAG synthesis is the first reaction specifically dedicatedto the synthesis of TAG, suggesting a key role for the PAP enzyme inthe regulation of PA flow towards the synthesis of TAG or membranephospholipids.The main goal of our project is to elucidate the role of the keyenzymatic step that governs the decision of M. tuberculosis to synthesizeTAG and, therefore, slow its growth and enter dormancy. Toaccomplish this goal, we overexpressed two candidate PAP proteinsin Mycobacterium smegmatis and found that both strains showedhigher levels of DAG and consequently of TAG. Genetic analysesare being carried out in order to define the physiological role of theseproteins, by the construction and further characterization of knockout mutants.