C-terminal region of Rv1039c (PPE15) protein of Mycobacterium tuberculosis targets host mitochondria to induce macrophage apoptosis

This study investigated the role of C-terminal region of Rv1039c (PPE15) in inducing mitochondrial perturbations and macrophage apoptosis. Ourin-silico studies revealed the disordered, coiled, and hydrophobic C-terminal region in Rv1039c has similarity with C-terminal of mitochondria-targeting pro-apoptotic host proteins. Wild type Rv1039c and C-terminal deleted Rv1039c (Rv1039c-/-Cterm) recombinant proteins were purified and theirM. smegmatis knock-in strains were constructed which were used forin-vitro experiments. Confocal microscopy showed localization of Rv1039c to mitochondria of PMA-differentiated THP1 macrophages; and reduced mitochondrial membrane depolarization and production of mitochondrial superoxides were observed in response to Rv1039c-/-Cterm in comparison to full-length Rv1039c. The C-terminal region of Rv1039c was found to activate caspases 3, 7 and 9 along with upregulated expression of pro-apoptotic genes likeBax andBim. Rv1039c-/-Cterm also reduced the Cytochrome-C release from the mitochondria and the expression of AnnexinV/PI positive and TUNEL positive cells as compared to Rv1039c. Additionally, Rv1039c was observed to upregulate the TLR4-NF- κB-TNF-α signalling whereas the same was downregulated in response to Rv1039c-/-Cterm. These findings suggested that the C-terminal region of Rv1039c is a molecular mimic of pro-apoptotic host proteins which induce mitochondria-dependent macrophage apoptosis and evoke host immune response. These o bservations en...
Source: Apoptosis - Category: Molecular Biology Source Type: research