Activation of Chemokine (C-C Motif) Receptor 1 Modulates α_1B-Adrenoceptor and Arginine Vasopressin Receptor 1A...

We reported previously that α_1B-AR (α_1B-adrenoceptor) and AVPR1A (arginine vasopressin receptor 1A) heteromerize with CCR1 (C-C motif [chemokine] receptor 1) in human monocytes, through which CCR1 is controlled. Whether CCR1 affects α_1B-AR and AVPR1A signaling and whether such complexes are detectable in human vascular smooth muscle cells (hVSMCs) is unknown.

Bioluminescence resonance energy transfer suggested that the receptors can form hetero-oligomeric complexes. Activation of CCR1 with CCL23 (chemokine [C-C motif] ligand 23) increased the efficacy of aVP (arginine vasopressin)-stimulated AVPR1A and reduced the efficacy of phenylephrine-stimulated α_1b-AR to activate guanine nucleotide-binding protein G(q) subunit alpha (Gαq) in cells coexpressing all 3 receptors. Although CCL23 increased the efficacy of aVP and phenylephrine to recruit β-arrestin to AVPR1A and α_1b-AR, respectively, when CCR1 is coexpressed, CCL23 did not affect β-arrestin recruitment to agonist-stimulated AVPR1A and α_1b-AR when all 3 receptors are present. Proximity ligation assays suggested that such receptor complexes are expressed in hVSMCs. Proximity ligation assays after small interfering RNA knockdown of each receptor showed that interactions between CCR1 and AVPR1A depend on the presence of α_1B-AR, whereas interactions between CCR1 and α_1B-AR and between α_1B-AR and AVPR1A are not affected by the presence of the third receptor partner. CCL23 increased IP3 (inositol trisphosphate) production and gel contraction of hVSMCs upon aVP stimulation and inhibited IP3 production and gel contraction of hVSMCs upon phenylephrine stimulation.

Our findings suggest that CCR1 within functional heteromeric complexes with α_1B-AR and AVPR1A modulates the efficacy of α_1B-AR and AVPR1A in hVSMCs to activate downstream signaling cascades that mediate vasoconstriction and control vascular tone.