title: Heteromerization of chemokine (C-X-C motif) receptor 4 with α1A/B-adrenergic receptors controls α1-adrenergic receptor function.
abstract: Recent evidence suggests that chemokine (C-X-C motif) receptor 4 (CXCR4) contributes to the regulation of blood pressure through interactions with α1-adrenergic receptors (ARs) in vascular smooth muscle. The underlying molecular mechanisms, however, are unknown. Using proximity ligation assays to visualize single-molecule interactions, we detected that α1A/B-ARs associate with CXCR4 on the cell surface of rat and human vascular smooth muscle cells (VSMC). Furthermore, α1A/B-AR could be coimmunoprecipitated with CXCR4 in a HeLa expression system and in human VSMC. A peptide derived from the second transmembrane helix of CXCR4 induced chemical shift changes in the NMR spectrum of CXCR4 in membranes, disturbed the association between α1A/B-AR and CXCR4, and inhibited Ca(2+) mobilization, myosin light chain (MLC) 2 phosphorylation, and contraction of VSMC upon α1-AR activation. CXCR4 silencing reduced α1A/B-AR:CXCR4 heteromeric complexes in VSMC and abolished phenylephrine-induced Ca(2+) fluxes and MLC2 phosphorylation. Treatment of rats with CXCR4 agonists (CXCL12, ubiquitin) reduced the EC50 of the phenylephrine-induced blood pressure response three- to fourfold. These observations suggest that disruption of the quaternary structure of α1A/B-AR:CXCR4 heteromeric complexes by targeting transmembrane helix 2 of CXCR4 and depletion of the heteromeric receptor complexes by CXCR4 knockdown inhibit α1-AR-mediated function in VSMC and that activation of CXCR4 enhances the potency of α1-AR agonists. Our findings extend the current understanding of the molecular mechanisms regulating α1-AR and provide an example of the importance of G protein-coupled receptor (GPCR) heteromerization for GPCR function. Compounds targeting the α1A/B-AR:CXCR4 interaction could provide an alternative pharmacological approach to modulate blood pressure.
authors.affiliation: Burn and Shock Trauma Research Institute, Department of Surgery, Loyola University Chicago Stritch School of Medicine, Maywood, IL 60153;
authors.forename: Abhishek
authors.initials: A
authors.lastname: Tripathi
authors.affiliation: Burn and Shock Trauma Research Institute, Department of Surgery, Loyola University Chicago Stritch School of Medicine, Maywood, IL 60153;
authors.forename: P Geoff
authors.initials: PG
authors.lastname: Vana
authors.affiliation: Department of Medicinal Chemistry, University of Illinois, Chicago, IL 60607;
authors.forename: Tanmay S
authors.initials: TS
authors.lastname: Chavan
authors.affiliation: Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago Stritch School of Medicine, Maywood, IL 60153;
authors.forename: Lioubov I
authors.initials: LI
authors.lastname: Brueggemann
authors.affiliation: Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago Stritch School of Medicine, Maywood, IL 60153;
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Byron
authors.affiliation: Cancer and Inflammation Program, National Cancer Institute, Frederick, MD 21702-1201;
authors.forename: Nadya I
authors.initials: NI
authors.lastname: Tarasova
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226; and.
authors.forename: Brian F
authors.initials: BF
authors.lastname: Volkman
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, IL 60607.
authors.forename: Vadim
authors.initials: V
authors.lastname: Gaponenko
authors.affiliation: Burn and Shock Trauma Research Institute, Department of Surgery, Loyola University Chicago Stritch School of Medicine, Maywood, IL 60153; Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago Stritch School of Medicine, Maywood, IL 60153; mmajetschak@luc.edu.
authors.forename: Matthias
authors.initials: M
authors.lastname: Majetschak
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001596:Benzylamines; D001794:Blood Pressure / Q000187:drug effects; D002462:Cell Membrane; D054377:Chemokine CXCL12 / Q000378:metabolism; D000080027:Cyclams; D019281:Dimerization; D006367:HeLa Cells; D006571:Heterocyclic Compounds / Q000737:chemistry; D006801:Humans; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D010656:Phenylephrine / Q000737:chemistry; D051381:Rats; D011917:Rats, Inbred Lew; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism
chemical_list: C547713:ADRA1A protein, human; C547716:ADRA1B protein, human; C547715:Adra1a protein, rat; C547718:Adra1b protein, rat; D001596:Benzylamines; C515255:CXCL12 protein, human; C575935:CXCL12 protein, rat; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; C486264:Cxcr4 protein, rat; D000080027:Cyclams; D006571:Heterocyclic Compounds; D018340:Receptors, Adrenergic, alpha-1; D019718:Receptors, CXCR4; D043562:Receptors, G-Protein-Coupled; D010656:Phenylephrine; C088327:plerixafor
keywords: AMD3100; CXCL12; blood pressure; phenylephrine; ubiquitin