Markedly reduced effects of (-)-isoprenaline but not of (-)-CGP12177 and unchanged affinity of beta-blockers at Gly389-beta1-adrenoceptors compared to Arg389-beta1-adrenoceptors.
1. Substitution of arginine by glycine at position 389, a frequent beta(1)-adrenoceptor polymorphism, reduces adenylyl cyclase stimulation by (-)-isoprenaline. beta(1)-Adrenoceptors mediate the effects of catecholamines and nonconventional partial agonists ((-)-CGP12177) through different sites. We investigated the influence of the 389 polymorphism on beta blocker affinity, as well as on the responses to (-)-isoprenaline and the nonconventional partial agonist (-)-CGP12177 on cyclic AMP levels in CHO cells expressing recombinant Arg389-beta(1)-adrenoceptors (101 fmol mg(-1) protein) or Gly389-beta(1)-adrenoceptors (94 fmol mg(-1)). 2. The affinity of beta-blockers and partial agonists, estimated from competition binding with (-)-[(125)I]-cyanopindolol, was not different for Arg389-beta(1)-adrenoceptors and Gly389-beta(1)-adrenoceptors. 3. The maximum cAMP increases by (-)-isoprenaline and (-)-CGP12177 at Gly389-beta(1)-adrenoceptors were reduced by 97 and 46%, but the potencies enhanced 2 and 0.5 log units, respectively, compared to Arg389-beta(1)-adrenoceptors. The intrinsic activity of (-)-CGP12177 with respect to the (-)-isoprenaline was 0.057 at Arg389-beta(1)-adrenoceptors and 1.05 at Gly389-beta(1)-adrenoceptors. 4. We confirm in intact CHO cells that responses to (-)-isoprenaline are markedly reduced at Gly389-beta(1)-adrenoceptors compared to Arg389-beta(1)-adrenoceptors. However, the 389 polymorphism reduces considerably less the agonist responses to (-)-CGP12177, indicating that coupling to G(s) protein is different for beta(1)-adrenoceptors activated by catecholamines than for receptors activated by nonconventional partial agonists. The affinity of beta-blockers is conserved across the Arg389Gly polymorphism.
Joseph
S S
SS
Department of Physiology, University of Cambridge, Downing Street, Cambridge CB2 3EG.
Lynham
J A
JA
Grace
A A
AA
Colledge
W H
WH
Kaumann
A J
AJ
D000319:Adrenergic beta-Antagonists / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000378:metabolism* / Q000494:pharmacology; D011110:Polymorphism, Genetic; D011412:Propanolamines / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D018342:Receptors, Adrenergic, beta-1 / Q000235:genetics / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D018342:Receptors, Adrenergic, beta-1; D001120:Arginine; D007545:Isoproterenol; C033394:CGP 12177; D005998:Glycine