Uncovering the role of cardiolipin in promoting gasdermin D-mediated necroptosis and hyperinflammation - PROJECT SUMMARY Mitochondria serve as a central signaling hub for innate immune responses. Disruption of mitochondrial function is a hallmark for various infections and chronic inflammatory diseases. The overall objective of this proposal is to define the molecular mechanisms that regulate mitochondrial membrane homeostasis and determine how membrane disruption promotes inflammatory cell death. Mutations in leucine-rich repeat kinase 2 (LRRK2) are associated with disrupted mitochondrial integrity and increased reactive oxygen species. They are also associated with increased susceptibility to hormonal breast cancer, Crohn's disease, and mycobacterial infection, strongly suggesting a role in innate immune function. Recently, the Watson lab set out to investigate LRRK2's role in peripheral innate immunity, focusing on a gain of function mutation, Lrrk2G2019S. Mitochondrial stress conferred by the Lrrk2G2019S mutation increases demand on the electron transport chain, which leads to excessive ROS production. This increased ROS triggers a new type of cell death where a protein canonically associated with pyroptosis, gasdermin D (GSDMD), can associate with mitochondrial membranes and cause necroptotic cell death. Aim 1 of this proposal will identify the minimal domain within GSDMD that targets mitochondrial membranes, enabling a better understanding of the molecular mechanisms underlying GSDMD's newly described role in necroptosis. Aim 2 will investigate the contribution of various aspects of mitochondrial dysfunction to GSDMD mitochondrial targeting and necroptosis, providing new insights into connections between the disruption of mitochondrial homeostasis and GSDM relocalization. With the goal of understanding how mitochondria are impacted by genetic mutations and/or stress, Aim 3 will measure relocalization of the mitochondrial inner membrane phospholipid cardiolipin in WT and Lrrk2G2019S macrophages and catalog mitochondrial lipids in WT vs. Lrrk2G2019S macrophages. Defining the molecular mechanisms that drive inflammation in the face of specific mitochondrial mutations will help enable therapeutic interventions designed to correct specific aspects of mitochondrial dysfunction associated with a variety of inflammatory, infectious, cardiac, and neurological disorders.
