Expression of P2X7 receptor splice variants is differentially regulated in macrophages versus T lymphocytes and is modulated by inflammatory cytokines

Abstract

The P2X7 ionotropic receptor (P2X7R) is expressed in macrophages and T cells and regulates multiple immune responses including cytokine release and apoptosis. P2X7R has high specificity but a low affinity for ATP which differs in macrophages vs. T cells. P2X7R channels in T cells but not macrophages can also be gated by ADP-ribosylation. With the identification of murine P2X7R splice variants “a” and “k,” we hypothesized that 1) their differential expression in T cells vs. macrophages may explain the differences in P2X7R phenotype of these leukocytes and 2) expression of the splice variants may be regulated by immune activation state. We compared 1) dose-response relationships for ATP activation of P2X7R-gated Ca2+ influx and 2) mRNAs for the P2X7-a and P2X7-k splice variants in murine BW5147 T cells vs. J774 macrophages with or without IFN-γ stimulation. Under basal conditions, the ratio of k/a splice variant expression was high in T cells but low in macrophages. Treatment of macrophages with IFN-γ markedly increased expression of the P2X7-k splice variant, which was correlated with a left shift in the ATP- Ca2+ influx dose response. We conclude that the ATP sensitivity of murine P2X7R is modulated via differential expression of splice variants and that alternative splicing of the primary P2X7 pre-mRNA transcript can be regulated by inflammatory cytokines. Support: NSF Grant REU-Biology: 2010-2012, R-01-GM-36387