Defining Mechanisms of MLKL-Mediated Mitochondrial Damage in Necroptosis and Mycobacterium tuberculosis Infection

PROJECT SUMMARY Mitochondria are essential regulators of cell death and innate immune responses, and their dysfunction is a hallmark of many infectious and inflammatory diseases. Although mitochondria are known to influence various forms of programmed cell death, their involvement in necroptosis—a lytic form of programmed cell death mediated by the pore-forming protein MLKL—remains poorly understood. My preliminary data indicate that inhibition of Drp1, a key regulator of mitochondrial fission, enhances necroptosis and promotes the recruitment of active MLKL to mitochondria, accompanied by loss of mitochondrial membrane potential, suggesting that Drp1-mediated mitochondrial fission acts as a protective mechanism that limits MLKL-induced mitochondrial damage. This key finding motivates my overarching hypothesis that mitochondrial membrane dynamics modulate cellular sensitivity to necroptosis by influencing the affinity of mitochondria for MLKL. Consequently, the overall objective of this proposal is to define the mechanism and inducing conditions by which MLKL- mediated mitochondrial damage enhances inflammatory cell death. Aim 1 will define the impact of MLKL recruitment on mitochondrial integrity and necroptotic signaling, thereby elucidating how mitochondrial damage amplifies necroptosis. Aim 2 will focus on identifying conditions that promote MLKL translocation to mitochondria during necroptosis, investigating factors such as impaired mitophagy, cardiolipin externalization, and mitochondrial network hyperfusion. Additionally, as Mycobacterium tuberculosis (Mtb) infection of macrophages in vitro is known to both alter mitochondrial dynamics and act as an inducing condition for necroptosis, I will evaluate the contribution of MLKL-mediated mitochondrial damage to cell death during Mtb infection. By defining the molecular mechanismsthat drive inflammation through MLKL-mediated mitochondrial damage, this research will enhance our understanding of the interplay between mitochondrial dynamics and inflammation, potentially facilitating the rational development of therapeutic interventions aimed at modulating these processes in various inflammatory and infectious diseases.