A single point mutation increases the affinity of serotonin 5-HT1D alpha, 5-HT1D beta, 5-HT1E and 5-HT1F receptors for beta-adrenergic antagonists

• Published in: Neuropharmacology Vol. 33; no. 3-4; pp. 387 - 391
• Main Authors: Adham, N, Tamm, J A, Salon, J A, Vaysse, P J, Weinshank, R L, Branchek, T A
• Format: Journal Article
• Language: English
• Published: England 01.03.1994
• Subjects: Adrenergic beta-Antagonists - pharmacokinetics; Amino Acid Sequence; Animals; Humans; Iodocyanopindolol; Ligands; Molecular Sequence Data; Mutagenesis, Site-Directed; Pindolol - analogs & derivatives; Point Mutation; Propranolol - pharmacology; Radioligand Assay; Rats; Receptors, Serotonin - drug effects; Receptors, Serotonin - genetics; Receptors, Serotonin - metabolism; Transfection - physiology
• ISSN: 0028-3908; 1873-7064
• DOI: 10.1016/0028-3908(94)90068-X

The serotonin 5-HT1B and 5-HT1A receptors bind certain beta-adrenergic antagonists, such as propranolol and pindolol, with high affinity. Other 5-HT1 receptors that display very low affinity for beta-adrenergic antagonists, have either a threonine (T) (5-HT1D alpha, 5-HT1D beta and 5-HT1E) or an alanine (A) (5-HT1F) residue in the homologous position in the seventh transmembrane domain. In the case of the human 5-HT1D beta receptor, replacement of this T with asparagine (N), dramatically increases its ability to bind beta-adrenergic antagonists. To assess whether other 5-HT1 receptors would behave similarly, we have used site-directed mutagenesis to replace the T or A in 5-HT1D alpha, 5-HT1E and 5-HT1F receptors with N. Both the wild-type and mutant genes were expressed transiently in COS-7 cells and radioligand binding studies were performed by using [3H]5-HT and [125I]iodocyanopindolol. Using [3H]5-HT, we found that the affinities of all the mutant receptors for propranolol and pindolol were significantly increased by 100-1000 fold, 5-HT1D alpha and 5-HT1F receptors showing the highest and the 5-HT1E receptor displaying the lowest affinity. On the other hand, the affinities for 5-HT were essentially unchanged as compared to the wild-type receptors. All mutant receptors bound [125I]iodocyanopindolol with high affinity, KD values ranging between 0.04 nM (mutant 5-HT1D alpha) and 0.57 nM (mutant 5-HT1E), whereas the wild-type receptors failed to show any specific binding with this radioligand in the same concentration range used for the mutant receptors.