Research Projects

Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis (TB), is a highly successful intracellular pathogen and annually accounts for the largest number of deaths caused by a single infectious agent. Mtb effectively evades host immunity, compromising effector functions to establish a cellular niche conducive to survival. Subsequently, at later stages of infection, Mtb induces the programmed necrosis of infected cells to facilitate its dissemination. Such alterations are mediated by co-opting signaling pathways, transcription factors, and distinct epigenetic factors, leading to differentially regulated host gene expression. Despite ongoing research, our understanding of such complex mechanisms of interaction between the host and mycobacteria and the subsequent epigenomic changes induced by Mtb remains incomplete. A comprehensive study of host factors enabling persistence of the mycobacterium within the host gives a definite perception of its virulence and would illustrate means of combating the infection. While the majority of studies have focused on the dynamic host-pathogen interactions through which Mtb infects the cell and mediates its intracellular survival, the mechanism of Mtb dissemination remains largely unknown. Recently, a few studies reported a role for ferroptosis, an iron-mediated form of programmed cell death, in detrimental inflammation, TB-associated pathology, and Mtb dissemination. Ferroptosis is driven by the iron-dependent accumulation of lethal lipid peroxidation (LPO) within the cell, leading to a programmed necrotic cell death. Multiple signalling pathways, including the cysteine-GSH-GPX4 axis, iron metabolism, reactive oxygen species (ROS) metabolism, and MAPK pathway, have been implicated in regulating ferroptosis in distinct model systems. Interestingly, anti-ferroptosis agents such as Vitamin E, selenium, and ferrostatin-1 serve as promising avenues of therapy as they help control the mycobacterium burden and reduce lung damage. Nevertheless, the limited understanding of this process and the potential off-target effects remain significant challenges. Our interest in the current project aims to understand the status of iron homeostasis in Mtb-infected cells and delineate the molecular players regulating the release of large amounts of free iron into the cells. To our interest, a previous study from our laboratory identified PRMT5, a host arginine methyltransferase, as a key player in Mtb pathogenesis. Inhibition of PRMT5 could reduce lung pathology, dissemination, and mycobacterial burden in mice models of TB, thereby serving as a promising target for therapy. Interestingly, parallel reports have demonstrated a role for PRMT5 in regulating ferroptosis in distinct models of study. With this premise, we conducted preliminary studies and observed that the inhibition of PRMT5 could reduce the key hallmarks of ferroptosis during Mtb infection. Mechanistically, this was effectuated by a PRMT5-mediated induction of ferritinophagy, the autophagic degradation of the intracellular iron chelator ferritin in Mtb-infected cells. These results encourage us to identify the molecular cross-talks involved in modulating host cell iron homeostasis upon mycobacterial infection and their role in facilitating ferroptosis. In this current study, we plan to build on our results and determine the functional relevance of iron-overload and its consequences during Mtb infection. Further, we also aim to evaluate the comprehensive pathways under the control of PRMT5 during Mtb infection. To this end, we propose on conducting high throughput sequencing studies in PRMT5 KO macrophages to identify the genes directly under the control of PRMT5.