Mice deficient of G-protein coupled receptor 3 (GPR3) developed severe experimental autoimmune uveitis (EAU) through increased effector T cell activities

We discovered a protective role of G protein-coupled receptor 3 (GPR3) in a mouse model of T cell-mediated autoimmune uveitis. GPR3 is an orphan receptor that maintains Gs-coupling and cyclic AMP production without an exogenous ligand. Consequently, GPR3 deficient (GPR3KO) mice were more susceptible to developing experimental autoimmune uveitis (EAU) induced by immunization with interphotoreceptor retinoid-binding protein (IRBP) or by adoptive transfer of IRBP-specific T cells than their wild type (WT) littermates. T cells isolated from IRBP-immunized GPR3KO mice demonstrated an increase in proliferation and inflammatory cytokine production in response to the specific IRBP antigen and a relatively high resistance to activation-induced T cell death compared to T cells isolated from immunized WT mice. Moreover, a major tight junction protein such as ZO-1 was reduced in GPR3 deficient retina with severe uveitis after IRBP-specific T cells were transferred. Taken together, our findings suggest that constitutively active GPR3 inhibits T cell mediated retinal inflammation.