title: Quantification of beta adrenergic receptor subtypes in beta-arrestin knockout mouse airways.
abstract: In allergic asthma Beta 2 adrenergic receptors (β2ARs) are important mediators of bronchorelaxation and, paradoxically, asthma development. This contradiction is likely due to the activation of dual signaling pathways that are downstream of G proteins or β-arrestins. Our group has recently shown that β-arrestin-2 acts in its classical role to desensitize and constrain β2AR-induced relaxation of both human and murine airway smooth muscle. To assess the role of β-arrestins in regulating β2AR function in asthma, we and others have utilized β-arrestin-1 and -2 knockout mice. However, it is unknown if genetic deletion of β-arrestins in these mice influences β2AR expression in the airways. Furthermore, there is lack of data on compensatory expression of βAR subtypes when either of the β-arrestins is genetically deleted, thus necessitating a detailed βAR subtype expression study in these β-arrestin knockout mice. Here we standardized a radioligand binding methodology to characterize and quantitate βAR subtype distribution in the airway smooth muscle of wild-type C57BL/6J and β-arrestin-1 and β-arrestin-2 knockout mice. Using complementary competition and single-point saturation binding assays we found that β2ARs predominate over β1ARs in the whole lung and epithelium-denuded tracheobronchial smooth muscle of C57BL/6J mice. Quantification of βAR subtypes in β-arrestin-1 and β-arrestin-2 knockout mouse lung and epithelium-denuded tracheobronchial tissue showed that, similar to the C57BL/6J mice, both knockouts display a predominance of β2AR expression. These data provide further evidence that β2ARs are expressed in greater abundance than β1ARs in the tracheobronchial smooth muscle and that loss of either β-arrestin does not significantly affect the expression or relative proportions of βAR subtypes. As β-arrestins are known to modulate β2AR function, our analysis of βAR subtype expression in β-arrestin knockout mice airways sets a reference point for future studies exploiting these knockout mice in various disease models including asthma.
authors: Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, Durham, North Carolina, United States of America.
authors: Akhil
authors: A
authors: Hegde
authors: Howard Hughes Medical Institute and Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America.
authors: Ryan T
authors: RT
authors: Strachan
authors: Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, Durham, North Carolina, United States of America.
authors: Julia K L
authors: JK
authors: Walker
mesh_terms: D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D001249:Asthma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D001980:Bronchi / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009126:Muscle Relaxation; D009130:Muscle, Smooth / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D014132:Trachea / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605253:ARRB1 protein, human; C000605254:ARRB2 protein, human; C000605255:Arrb1 protein, mouse; C000605258:Arrb2 protein, mouse; D019390:Arrestins; D018343:Receptors, Adrenergic, beta-2; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins