PROJECT ABSTRACT Gasdermin (GSDM) A-E comprise a family of pore-forming proteins that are associated with infection, inflammation and cancer. RNAseq analysis revealed that the only GSDM family members expressed by neutrophils are Gsdmd and Gsdme/DFNA5, and preliminary data show that neutrophils can activate caspase- 3, which cleaves pro- GSDME to the pore-forming N-GSDME to drive formation of plasma membrane pores leading to pro-inflammatory pyroptotic cell death. This is in contrast to results from our Nature Communications 2020 paper showing that that GSDMD activated by caspase-1 and neutrophil elastase in neutrophils occurs in the absence of pyroptotic cell death. Both GSDMD and GSDME mediate neutrophil production of bioactive IL- 1β, which we reported is a pivotal cytokine in the host immune response that is required to regulate Streptococcus pneumoniae and Pseudomonas aeruginosa bacterial growth and corneal opacification. We propose to characterize GSDME regulation and function in neutrophils in response to S. pneumoniae and P. aeruginosa in vitro, and to define the vivo role(s) of GSDME in keratitis caused by these pathogenic bacteria. Aim 1 will characterize GSDME regulation and function in neutrophils and define its role in coordinating neutrophil pyroptotic cell death and formation of neutrophil extracellular traps in response to S. pneumoniae or P. aeruginosa. Aim 2 will characterize GSDME processing in infected corneas, and assess the role of GSDME in S. pneumoniae or P. aeruginosa using GSDME-/- and GSDME-/-/GSDMD-/- mice in neutrophil viability, bacterial killing and the severity of corneal disease, and will use an adoptive transfer model to examine the role of neutrophil GSDME. Results of the proposed studies will provide insight into the role of these pore forming proteins in neutrophil responses to these ocular pathogens, and will identify potential targets for immune intervention in bacterial keratitis.