The ATP-Exporting Hemichannel Pannexin-1 Promotes CD8+ T Cell Memory Establishment

Abstract

Abstract Release of extracellular ATP (eATP) by dying cells is often identified as a "danger signal" by immune cells. However, eATP export by healthy cells is common, and a major transmembrane ATP exporter is the Pannexin 1 (Panx1) molecule. CD8+ T cells express Panx1 during thymic development, at steady-state and during immune response. However, the role of Panx1 on CD8+ T cell-mediated immune response is not well defined. Here, we used genetic and pharmacological ablation tools to address this question. T cell-specific Panx1 deletion does not affect CD8+ T cell thymic development or effector responses to viral infection (LCMV). In contrast, memory CD8+ T cell establishment is impaired by either pharmacological inhibition or CD8-specific Panx1 deletion. Using a tamoxifen-controlled, conditional Panx1 knockout LCMV-specific (P14) CD8+ T cell system, we found that both memory CD8+ T cell generation and survival rely on Panx1. In vitro data further supports these findings: two Panx1 inhibitors, 10Panx and Probenecid, reduce the expression of the central memory marker CD62L. Panx1-deficient CD8+ T cells develop a memory-like phenotype in response to IL-15, but fail to engage mitochondrial respiration and present decreased mitochondrial membrane potential, suggesting Panx1 promotes optimal mitochondrial function. These defects are partially reverted with exogenous eATP. Collectively, our data indicates that cell-intrinsic Panx1-mediated eATP export favors memory CD8+ T cell differentiation. We are currently testing whether CD8-intrinsic Panx1 controls memory CD8+ T cell generation solely as an autocrine eATP source, or if Panx1 also serves as a “rheostat” controlling intracellular ATP levels in antigen-responding CD8+ T cells.