A Gain-of-function Polymorphism in a G-protein Coupling Domain of the Human β1-Adrenergic Receptor

• Published in: The Journal of biological chemistry 1999-04, Vol.274 (18), p.12670
• Main Authors: Deborah A. Mason, J. Donald Moore, Stuart A. Green, Stephen B. Liggett
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.18.12670

The β 1 -adrenergic receptor (β 1 AR) is a key cell surface signaling protein expressed in the heart and other organs that mediates the actions of catecholamines of the sympathetic nervous system. A polymorphism in the intracellular cytoplasmic tail near the seventh transmembrane-spanning segment of the human β 1 AR has been identified in a cohort of normal individuals. At amino acid position 389, Gly or Arg can be found (allele frequencies 0.26 and 0.74, respectively), the former previously considered as the human wild-type β 1 AR. Using site-directed mutagenesis to mimic the two variants, CHW-1102 cells were permanently transfected to express the Gly-389 and Arg-389 receptors. In functional studies with matched expression, the Arg-389 receptors had slightly higher basal levels of adenylyl cyclase activities (10.7 ± 1.2 versus 6.1 ± 0.4 pmol/min/mg). However, maximal isoproterenol-stimulated levels were markedly higher for the Arg-389 as compared to the Gly-389 receptor (63.3 ± 6.1 versus 20.9 ± 2.0 pmol/min/mg). Agonist-promoted [ 35 S]guanosine 5′- O -(thiotriphosphate) binding was also increased with the Arg-389 receptor consistent with enhanced coupling to G s and increased adenylyl cyclase activation. In agonist competition studies carried out in the absence of guanosine 5′-(β,γ-imido)triphosphate, high affinity binding could not be resolved with the Gly-389 receptor, whereas Arg-389 displayed an accumulation of the agonist high affinity receptor complex ( R H = 26%). Taken together, these data indicate that this polymorphic variation of the human β 1 AR results in alterations of receptor-G s interaction with functional signal transduction consequences, consistent with its localization in a putative G-protein binding domain. The genetic variation of β 1 AR at this locus may be the basis of interindividual differences in pathophysiologic characteristics or in the response to therapeutic βAR agonists and antagonists in cardiovascular and other diseases.