Pharmacological Analysis and Structure Determination of 7-Methylcyanopindolol-Bound Beta1-Adrenergic Receptor.Sato, T., Baker, J., Warne, T., Brown, G., Leslie, A., Congreve, M., Tate, C.
(2015) Mol.Pharmacol. 88: 1024
- PubMed: 26385885
- DOI: 10.1124/mol.115.101030
- PubMed Abstract:
Comparisons between structures of the β1-adrenergic receptor (AR) bound to either agonists, partial agonists, or weak partial agonists led to the proposal that rotamer changes of Ser(5.46), coupled to a contraction of the binding pocket, are sufficie ...
Comparisons between structures of the β1-adrenergic receptor (AR) bound to either agonists, partial agonists, or weak partial agonists led to the proposal that rotamer changes of Ser(5.46), coupled to a contraction of the binding pocket, are sufficient to increase the probability of receptor activation. (RS)-4-[3-(tert-butylamino)-2-hydroxypropoxy]-1H-indole-2-carbonitrile (cyanopindolol) is a weak partial agonist of β1AR and, based on the hypothesis above, we predicted that the addition of a methyl group to form 4-[(2S)-3-(tert-butylamino)-2-hydroxypropoxy]-7-methyl-1H-indole-2-carbonitrile (7-methylcyanopindolol) would dramatically reduce its efficacy. An eight-step synthesis of 7-methylcyanopindolol was developed and its pharmacology was analyzed. 7-Methylcyanopindolol bound with similar affinity to cyanopindolol to both β1AR and β2AR. As predicted, the efficacy of 7-methylcyanopindolol was reduced significantly compared with cyanopindolol, acting as a very weak partial agonist of turkey β1AR and an inverse agonist of human β2AR. The structure of 7-methylcyanopindolol-bound β1AR was determined to 2.4-Å resolution and found to be virtually identical to the structure of cyanopindolol-bound β1AR. The major differences in the orthosteric binding pocket are that it has expanded by 0.3 Å in 7-methylcyanopindolol-bound β1AR and the hydroxyl group of Ser(5.46) is positioned 0.8 Å further from the ligand, with respect to the position of the Ser(5.46) side chain in cyanopindolol-bound β1AR. Thus, the molecular basis for the reduction in efficacy of 7-methylcyanopindolol compared with cyanopindolol may be regarded as the opposite of the mechanism proposed for the increase in efficacy of agonists compared with antagonists.
MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom (T.S., T.W., A.G.W.L., C.G.T.); Heptares Therapeutics Ltd, Welwyn Garden City, United Kingdom (G.A.B., M.C.); School of Life Sciences, University of Nottingham, Medical School, Queen's Medical Centre, Nottingham, United Kingdom (J.B.); KEK High Energy Accelerator Research Organization, Institute of Materials Structure Science, Structural Biology Research Center, Tsukuba, Japan (T.S.).