Haplotype analysis of the beta2 adrenergic receptor gene and risk of myocardial infarction in humans.
ABSTRACT Polymorphisms in the beta2 adrenergic receptor (ADRB2), in particular G16R, Q27E, and T164I, have been implicated in the pathogenesis of cardiovascular and metabolic phenotypes. However, no prospective, genetic-epidemiological data are available on the risk of cardiovascular disease associated with these variants. Using DNA samples collected at baseline in a prospective cohort of 14,916 initially healthy American men, we evaluated the G16R, Q27E, and T164I polymorphisms among 523 individuals who subsequently developed myocardial infarction and among 2092 individuals who remained free of reported cardiovascular events during follow-up. The haplotype frequency distribution was significantly different among cases and controls (chi(2)(7d.f.) = 20.92, P = 0.0039). Haplotype-based logistic regression, adjusting for age, smoking, and randomized treatment group, indicated that G16-Q27-I164 (odds ratio 0.178, 95% C.I. 0.043-0.737, P = 0.017) and (non-G16-Q27)-T164 (odds ratio 1.235, 95% C.I. 1.031-1.480, P = 0.022) haplotypes were significantly associated with altered risk of myocardial infarction. These findings remained after further adjustment for BMI, history of hypertension, and presence or absence of diabetes. In conclusion, variation in haplotype frequencies for the beta2 adrenergic receptor gene was found to be associated with risk of myocardial infarction.
Article: Influence of beta 2-adrenergic receptor genotypes on signal transduction in human airway smooth muscle cells.[show abstract] [hide abstract]
ABSTRACT: The phenotypic relevance of allelic variation in the structure of the beta 2-adrenergic receptor (beta 2AR) expressed in lung cells is unknown. In particular, altered responsiveness of the beta 2AR expressed on airway smooth muscle, which are responsible for bronchodilation in the treatment of asthma, may be an important factor in the ultimate physiologic response to agonist. To approach this, we established primary cultures of human airway smooth muscle cells obtained at autopsy and developed a method to determine the beta 2AR genotype at the polymorphic loci of codons 16 and 27, using allele-specific polymerase chain reactions. Radioligand binding studies revealed that these cells expressed approximately 70 fmol/mg of receptor which was exclusively of the beta 2AR subtype. All cell lines obtained (n = 10) exhibited normal agonist binding and receptor-mediated activation of the adenylyl cyclase second messenger pathway. However, distinct differences were found in the response to long-term agonist exposure between the different beta 2AR genotypes. Cells expressing Arg at codon 16 (Arg16) traditionally referred to as wild-type, underwent 77.8 +/- 8.1% downregulations of beta 2AR following prolonged (24-h) exposure to the beta 2AR agonist isoproterenol (10 microM). In contrast, cells expressing Gly16 beta 2AR underwent enhanced agonist-promoted downregulation (95.6 +/- 1.7%, P < 0.05 versus Arg16), whereas cells expressing Glu27 beta 2AR were relatively resistant to such downregulation (29.5 +/- 12.7%, P < 0.01 versus Arg16). For cells expressing Glu27 beta 2AR, this difference resulted in a significant attenuation of agonist-promoted functional desensitization (33 +/- 7 versus 90 +/- 5% desensitization for Arg16, P < 0.001) following preincubation with 1 microM isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)American Journal of Respiratory Cell and Molecular Biology 08/1995; 13(1):25-33. · 5.13 Impact Factor
Article: A polymorphism of the human beta 2-adrenergic receptor within the fourth transmembrane domain alters ligand binding and functional properties of the receptor.[show abstract] [hide abstract]
ABSTRACT: We have recently identified several naturally occurring variants of the human beta 2-adrenergic receptor (beta 2AR). One of these polymorphisms, which is relatively uncommon, is a mutation occurring in the fourth transmembrane spanning domain, with Ile substituted for Thr at amino acid 164 within the proposed ligand binding pocket. This mutation is adjacent to Ser165 which has been predicted to interact with the beta-carbon hydroxyl group of adrenergic ligands. To determine the functional significance of this variant, we constructed by site-directed techniques a mutated beta 2AR (Ile164) with this substitution and expressed it in CHW-1102 cells. In the presence of guanine nucleotide, Ile164 displayed a lower binding affinity for epinephrine as compared with the wild-type beta 2AR (Ki = 1450 +/- 79 versus 368 +/- 39 nM; p < 0.001). A similarly decreased affinity was found with the catecholamines isoproterenol and norepinephrine, but not with dobutamine or dopamine which lack hydroxyl groups on their beta-carbons. In addition, antagonists without aromatic ring polar substituents displayed a decreased affinity for the mutated receptor. In agonist competition experiments conducted in the absence of guanine nucleotide, Ile164 failed to exhibit detectable high affinity binding, suggesting an impairment in the formation of the agonist-receptor-Gs complex. Consistent with this finding, functional coupling to Gs as determined in adenylyl cyclase assays was significantly (approximately 50%) depressed with Ile164 under both basal and agonist-stimulated conditions. beta 2AR sequestration, which is also triggered by agonist binding, was also found to be approximately 65% reduced in the Ile164 polymorphism. This study represents the first characterization of a naturally occurring mutation of a human adrenergic receptor. Our findings generally support the hypothesized role of this region of the receptor for ligand binding and receptor activation, as well as for establishing critical interactions for overall receptor conformation.Journal of Biological Chemistry 11/1993; 268(31):23116-21. · 4.77 Impact Factor
Article: Polymorphisms of the beta2 -adrenoceptor (ADRB2) gene and essential hypertension: the ECTIM and PEGASE studies.[show abstract] [hide abstract]
ABSTRACT: The beta2-adrenoceptor (ADRB2) plays a pivotal role in signalling in relation to hypertension and obesity. Polymorphisms of the ADRB2 gene have been shown to be potentially related to essential hypertension and other non-cardiovascular disease phenotypes. We investigated whether genetic variation of the ADRB2 gene might be related to essential hypertension or myocardial infarction (MI). Four ADRB2 gene polymorphisms C19R (T-47C), T-20C, G16R (G+46A), Q27E (C+79G) were investigated in two studies: PEGASE, a study of moderate to severe hypertension (707 cases) conducted in France, and ECTIM, a case-control study of MI (1178 cases, 1187 controls) conducted in France, Northern Ireland and Scotland. Genotyping was performed using allele-specific oligonucleotides. The ADRB2 polymorphisms T-20C and Q27E were found to be completely concordant, generating the haplotypes [T-20-Q27] and [C-20-E27]. Three main haplotypes accounted for 94% of all haplotypes: [R19-G16-E27] (39%), [C19-R16-Q27] (35%) and [C19-G16-Q27] (20%). Haplotype frequencies were not significantly different between countries. Allele and genotype frequencies did not differ significantly between cases with essential hypertension or MI and control subjects. There was no association of the polymorphisms with early onset hypertension, blood pressure level, coronary artery stenosis or any other phenotype measured in these study populations. In the ECTIM Study, our calculation revealed that we could have detected an odds ratio (OR) for MI of 1.3 with 80% power at a 5% type I error probability, the corresponding value for the PEGASE Study being an OR of 1.6 for hypertension. From our present analysis we conclude that the ADRB2 gene polymorphisms studied do not contribute in any important way to the risk of essential hypertension or MI in subjects of European ancestry.Journal of Hypertension 03/2002; 20(2):229-35. · 4.02 Impact Factor