Identificação de potenciais ligantes do glicolipídeo fenólico (PGL I) do Mycobacterium leprae e seu papel como modulador do metabolismo lipídico de células de Schwann humanas

Abstract

The phenolic glycolipid PGL I is an exclusive molecule of Mycobacterium leprae (M. leprae), the etiological agent of leprosy, located in the cell wall of the bacillus. Its trisaccharide portion not found in PGLs of other mycobacteria confers specificity to this molecule. PGL I interacts with receptors involved both in the invasion of host cells by M.leprae and in the evasion of the immune response induced by mycobacteria. One of the complications related to leprosy is peripheral nerve lesions, which lead to highly disabling neuropathies as a result of Schwann cell (CS) infection. It is known that PGL I is associated with M. leprae tropism by CS because it interacts with laminin type 2 present in the basal lamina of the peripheral nerve. Recent data from our group show that M. leprae and PGL I per se are capable of inducing the formation of cholesterol-rich lipid bodies (CLs), which are important organelles for the survival of the pathogen. Therefore, this project aimed to understand how PGL I could be influencing the host cell, focusing essentially on pathways associated with lipid metabolism, cholesterol synthesis and formation of CLs. Using qRT-PCR techniques to analyze gene expression, immunofluorescence, cross-linking and a reanalysis of shotgun proteomics data, we aimed to: 1) show the role of PGL I as a modulator of lipid metabolism in Schwann cells; 2) To analyze potential binding proteins of PGL I and to verify their possible relation with the activation of the transcription factor PPARγ and modulation of the lipid metabolism, seeking, therefore, to understand better, at the molecular level, how M. leprae subverts the accumulation of cholesterol to its favor. To achieve these objectives, CS cultures from the ST88-14 lineage were stimulated with the PGL I molecule per se or with a recombinant strain of M. bovis BCG expressing PGL I (BCG-PGL I). Our data suggest that PGL I was able to induce an increase in the expression of enzymes such as HMGCoA reductase and the enzyme fatty acid synthase (FASN), and our results indicate that the PGL I molecule increased the expression of the PPARγ transcription factor and the gene which encodes the prostaglandin E2 synthase enzyme (PGE2S) leading to increased production of PGE2. Through a reanalysis of proteomics data generated in our laboratory, we selected 12 potentially PGL I-binding proteins involved in lipid metabolism, as well as in the formation of CLs. In silico analysis of these proteins expanded information regarding their cellular location and the presence of transmembrane domains. Sequence analysis of these proteins also reinforced some of them as potential ligands of the PGL I molecule. We believe that the data generated from this study may contribute to a better understanding of this disease and a greater understanding of the development of neural lesions.