Redox-dependent internalization of the purinergic P2Y receptor limits colitis progression.

After ligand stimulation, many G protein–coupled receptors (GPCRs) undergo β-arrestin–dependent desensitization, during which they are internalized and either degraded or recycled to the plasma membrane. Some GPCRs are not subject to this type of desensitization because they lack the residues required to interact with β-arrestins. We identified a mechanism of redox-dependent alternative internalization (REDAI) that promotes the internalization and degradation of the purinergic P2Y receptor (P2YR). Synthetic and natural compounds containing electrophilic isothiocyanate groups covalently modified P2YR at Cys, which promoted the ubiquitylation of Lys and receptor internalization and degradation in various mouse and human cultured cell lines. Endogenous electrophiles also promoted ligand-dependent P2YR internalization and degradation. P2YR is highly abundant in inflammatory cells and promotes the pathogenesis of colitis. Deficiency in P2YR protected mice against experimentally induced colitis, and mice expressing a form of P2YR in which Cys was mutated to nonmodifiable serine were more sensitive to the induction of colitis. Several other GPCRs, including AAR, contain cysteine and lysine residues at the appropriate positions to mediate REDAI, and isothiocyanate stimulated the internalization of AAR and of a form of P2YR with insertions of the appropriate residues. Thus, endogenous and exogenous electrophiles may limit colitis progression through cysteine modification of P2YR and may also mediate internalization of other GPCRs.