GRK2/3-regulated, but not constitutive, phosphorylation of the G protein-coupled receptor GPR84 controls arrestin interactions and subsequent function

ABSTRACT: Although the GPR84 activators 2-HTP and 6-OAU promoted phosphorylation of human GPR84 and its interactions with arrestin-3, PSB-16671 and DL-175 did not. Replacement of all 21 serine and threonine residues within the third intracellular loop, but not the 2 serines in the C-terminal tail, eliminated incorporation of [32P] promoted by 2-HTP and greatly reduced receptor-arrestin-3 interactions. Mass spectrometry indicated that GPR84 was phosphorylated constitutively on residues Ser221 and Ser224 whilst a range of sites became phosphorylated in response to 2-HTP. An antiserum able to identify pSer221/pSer224 recognised GPR84 from cells treated both with and without 2-THP, whilst an antiserum able to identify pThr263/pThr264 recognised GPR84 only after exposure to 2-HTP. Treatment with neither PSB-16671 nor DL-175 was able to promote receptor recognition by this antiserum. 2-HTP-mediated phosphorylation of Thr263/Thr264 was prevented by two chemically distinct GPR84 antagonists but neither affected constitutive phosphorylation of Ser221/Ser224. 2-HTP-mediated phosphorylation of Thr263/Thr264 but not constitutive phosphorylation of Ser221/Ser224 was prevented by GRK2/3 inhibition. Mutation of residues Thr263 and Thr264 to alanine generated a variant of GPR84 as limited in 2-HTP-induced interactions with arrestin-3 as when all 21 serine and threonine were eliminated from the third intracellular loop. By contrast this mutant was unaffected in capacity to reduce cAMP levels in response to 2-HTP. Homology modelling and mutagenesis provided molecular insight into differences in agonist function. These studies define key residues, regulated by GRK2/3, that define effective interactions with arrestins and provide novel tools to monitor the phosphorylation and functional status of GPR84.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Adrian Butcher  

LAB HEAD: Graeme Milligan

PROVIDER: PXD031252 | Pride | 2022-06-09

REPOSITORIES: Pride