Control of CD8+ T cell Memory Homeostasis via Extracellular Damage Sensors ARTC2 & P2RX7

/ABSTRACT Many types of resident leukocytes live within the tissues of the body, acting as frontline defenders against infection as well as fulfilling homeostatic tissue support roles. Tissue resident memory T cells (TRM) are poised to respond to antigen-specific and non-specific signals at sites of tissue injury. Extracellular adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD+) are evolutionary conserved “danger signals” released by cell damage. In mice and humans, extracellular ATP (eATP) is recognized by purinergic receptors. Among those receptors, P2RX7 is a cell membrane channel preferentially expressed in immune cells that can support T cell activation along with the development and maintenance of memory T cell subsets at physiologic levels of eATP. However, P2RX7 activity is finely balanced: too little activity discourages memory cell homeostasis whereas persistent, strong activation culminates in cell death via formation of a non-specific pore structure. In mice, ARTC2.2 covalently modifies P2RX7 in response to extracellular NAD+ (eNAD+), amplifying the sensitivity of P2RX7 eATP and encouraging its pro-apoptotic capacities. Previous work has suggested ARTC2.2 and P2RX7 function to limit inappropriate T cell activation at sites of tissue injury, perhaps curtailing development of harmful immune responses that would produce tissue damage in turn. However, autonomous, cell-intrinsic effects of ARTC2.2 upon TRM are poorly defined. Utilizing a newly-generated, germline knockout mouse strain deficient in ARTC2.2, this proposal aims to (1) characterize the cell-intrinsic contribution of ARTC2.2 to CD8+ TRM homeostasis in primary immune responses and (2) assess ARTC2.2 effects upon TRM in the setting of tissue injury incurred by sterile inflammation and secondary infection. Using murine models of primary, secondary, and bystander immune responses, multi-parameter spectral flow cytometry and advanced, high-resolution quantitative microscopy will identify and enumerate memory CD8+ T cell subsets from lymphoid and non-lymphoid tissues. As release of eNAD+ and eATP can occur during processing of experimental tissue, these studies purport to surmount technical challenges inherent to investigation of tissue-resident T cells. Ultimately, these studies will help elucidate the role of ARTC2.2 in memory CD8+ T cell homeostasis and will provide key insights on how “danger signals” and the sensing of cellular damage help build long-term immunity against pathogens and limit deleterious immune activation following tissue injury. Project Number: 1F32AI194558-01 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: William Valente | Institution: UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MN | Award Amount: $90,964 | Activity Code: F32 | Study Section: Special Emphasis Panel[ZRG1 F07B-G (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1F32AI19455801