Regulation of gasdermins through protease processing and other post-translational modifications.

Abstract The long-term research program in the Xiao lab focuses on structural and biochemical studies of innate immune signaling, particularly the inflammasome pathways. Activation of inflammasomes may lead to the maturation and secretion of proinflammatory cytokines IL-1b and IL-18, as well as pyroptosis. Pyroptosis is a highly inflammatory form of cell death mediated by gasdermin D (GSDMD) and other gasdermin family members downstream of diverse signaling pathways implicated in infections and autoimmune or autoinflammatory disorders. As such, understanding the mechanisms of gasdermin regulation is highly significant. Despite recent progress on the identification of gasdermins as effectors of pyroptosis, and on the mechanisms of GSDMD activation by inflammatory caspases, contributed by the Xiao lab and others, the molecular mechanisms underlying the regulation of gasdermin function remain incompletely understood. In particular, gasdermin processing by different caspases and other proteases that may activate or suppress pyroptosis remain understudied. Even though protease processing, an irreversible form of post-translational modification (PTM), is the most intensively studied mechanisms of gasdermin regulation, emerging evidence suggests that gasdermins are regulated by several other PTMs such as ubiquitination and Cys modifications. The regulation of gasdermins by host and microbial proteases, ubiquitin ligases, and palmitoyltransferases remain key knowledge gaps that have hampered mechanistic understanding of pyroptosis regulation under physiological and pathological conditions. This proposal is based on emerging evidence from the rapidly evolving field of gasdermin biology that serve as strong scientific premise and rationale. The proposed studies leverage our expertise in structural and biochemical studies of gasdermin activation by inflammatory caspases, and target critical gaps in our understanding of gasdermin regulation using complementary structure-function approaches. We hypothesize that post-translational modifications of gasdermins by host and microbial enzymes, such as proteases, ubiquitin ligases, palmitoyltransferases, and other enzymes, regulate their function in pyroptosis. Better understanding of how gasdermins are regulated will not only furnish new insights into pyroptosis modulation, but also stimulate the development of novel therapeutics that target gasdermins and pyroptosis. Overall, this proposal builds upon the PI’s past research program that enables the long-term pursuit of the mechanisms for gasdermin regulation on a scale that is broadly compatible with the MIRA mechanism.