α-adrenoceptor ligands inhibit chemokine receptor heteromerization partners of α-adrenoceptors via interference with heteromer formation.

We reported previously that α-adrenoceptor (α-AR) ligands inhibit chemokine receptor (CR) heteromerization partners of α-AR. The underlying mechanisms are unknown and in vivo evidence for such effects is missing. Utilizing CCR2 and α-AR as prototypical partners, we observed in recombinant systems and THP-1 cells that α-AR enhanced whereas its absence inhibited Gαi signaling of CCR2. Phenylephrine and phentolamine reduced the CCR2:α-AR heteromerization propensity and inhibited Gαi signaling of CCR2. Phenylephrine cross-recruited β-arrestin-2 to CCR2, and reduced expression of α-AR, CR partners (CCR1/2, CXCR4) and corresponding heteromers. Phentolamine reduced CR:α-AR heteromers without affecting β-arrestin-2 recruitment or receptor expression. Phenylephrine/phentolamine prevented leukocyte infiltration mediated via CR heteromerization partners in a murine air pouch model. Our findings document that α-AR ligands inhibit leukocyte migration mediated by CR heteromerization partners in vivo and suggest interference with α-AR:CR heteromerization as a mechanism by which CR partners are inhibited. These findings provide new insights into the pharmacology of GPCR heteromers and indicate that an agonist and antagonist at one GPCR can act as antagonists at heteromerization partners of their target receptors.