title: Downregulation of kinin B1 receptor function by B2 receptor heterodimerization and signaling.
abstract: Signaling through the G protein-coupled kinin receptors B1 (kB1R) and B2 (kB2R) plays a critical role in inflammatory responses mediated by activation of the kallikrein-kinin system. The kB2R is constitutively expressed and rapidly desensitized in response to agonist whereas kB1R expression is upregulated by inflammatory stimuli and it is resistant to internalization and desensitization. Here we show that the kB1R heterodimerizes with kB2Rs in co-transfected HEK293 cells and natively expressing endothelial cells, resulting in significant internalization and desensitization of the kB1R response in cells pre-treated with kB2R agonist. However, pre-treatment of cells with kB1R agonist did not affect subsequent kB2R responses. Agonists of other G protein-coupled receptors (thrombin, lysophosphatidic acid) had no effect on a subsequent kB1R response. The loss of kB1R response after pretreatment with kB2R agonist was partially reversed with kB2R mutant Y129S, which blocks kB2R signaling without affecting endocytosis, or T342A, which signals like wild type but is not endocytosed. Co-endocytosis of the kB1R with kB2R was dependent on β-arrestin and clathrin-coated pits but not caveolae. The sorting pathway of kB1R and kB2R after endocytosis differed as recycling of kB1R to the cell surface was much slower than that of kB2R. In cytokine-treated human lung microvascular endothelial cells, pre-treatment with kB2R agonist inhibited kB1R-mediated increase in transendothelial electrical resistance (TER) caused by kB1R stimulation (to generate nitric oxide) and blocked the profound drop in TER caused by kB1R activation in the presence of pyrogallol (a superoxide generator). Thus, kB1R function can be downregulated by kB2R co-endocytosis and signaling, suggesting new approaches to control kB1R signaling in pathological conditions.
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, United States.
authors.forename: Xianming
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, United States.
authors.forename: Viktor
authors.initials: V
authors.lastname: Brovkovych
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, United States.
authors.forename: Yongkang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, United States.
authors.forename: Fulong
authors.initials: F
authors.lastname: Tan
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, United States; Center for Lung and Vascular Biology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, United States. Electronic address: rskidgel@uic.edu.
authors.forename: Randal A
authors.initials: RA
authors.lastname: Skidgel
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002463:Cell Membrane Permeability; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D015536:Down-Regulation; D004705:Endocytosis; D042783:Endothelial Cells / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D055503:Protein Multimerization; D043783:Receptor, Bradykinin B1 / Q000378:metabolism*; D043782:Receptor, Bradykinin B2 / Q000819:agonists / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D002118:Calcium
keywords: Clathrin-coated pit; Endocytosis; G protein-coupled receptor; Heterodimer; Heterologous desensitization; Kinin B1 and B2 receptor