α₁-Adrenergic Receptor Subtype Determinants for 4-Piperidyl Oxazole Antagonists

Abstract

Mutational studies in conjunction with ligand binding assays were used to examine the basis of alpha1-adrenergic receptor subtype selectivity for a series of 4-piperidyloxazole antagonists. A set of chimeric alpha 1A receptors were created by systematically substituting individual transmembrane domains from alpha 1D adrenergic receptors. The oxazole antagonists exhibited significant reductions in affinity against the receptor construct alpha 1A/D(TM2), and moderate reductions in affinity versus constructs alpha 1A/D(TM5), alpha 1A/B(TM5), and alpha 1A/D(TM6). Antagonist affinities for these chimeras exceeded those found for wild type alpha 1D and alpha 1B. Site-directed mutagenesis methods were then used to explore the role that individual residues in TM2 and TM5 play in ligand binding affinity and selectivity. These studies revealed that mutations at position 86 in the second transmembrane domain and position 185 in the fifth transmembrane domain of the alpha 1A receptor have a major impact on receptor subtype selectivity.

Efficient inducible Pan‐neuronal cre‐mediated recombination in SLICK‐H transgenic mice

“…The objects in the dataset were wild type, chimeric, and point‐mutated adrenergic receptors with derivatives of 4‐piperidyl oxazole antagonists. The binding affinity pK i values on the interaction were taken from Hamaguchi et al17…”

“…In order to validate our methodology in modeling receptor‐ligand interactions, we applied it to three distinctive PCM datasets that represent a superfamily of membrane receptors. The first two datasets consist of melanocortin receptors and peptide ligands14–16 and the third dataset contain adrenergic receptors and ligands 17. Melanocortin18 and adrenergic19 receptors belong to the superfamily of GPCRs.…”

GPCR Antitarget Modeling: Pharmacophore Models for Biogenic Amine Binding GPCRs to Avoid GPCR‐Mediated Side Effects

“…In addition, through mutational studies and comparative affinity determinations based on ligand binding, the essential amino acids involved in antagonist recognition have been identified for the a 1A , [15][16][17] 5-HT 2A [18,19] and D2 receptors. [14,19] According to these studies, the binding pocket of the prototype biogenic amine receptor antagonist stretches from the agonist binding site formed by TM3, TM5, and TM6-interacting with the antagonist's head group-towards the transmembrane helices TM1, TM2, and TM7, which have been suggested to harbor the lipophilic tail moiety of several antagonists.…”

New Prospects for Drug Discovery from Structural Studies of Rhodopsin

“…For the β 2 -adrenergic receptor, catecholamines agonists have been shown to bind to a region of the receptor comprising helices III, V, VI and VII [72,73]. In the case of the α 1A -adrenergic receptor similar studies were carried out to examine binding of dihydropyridine and 4-piperidyloxazole antagonists [74,75]. The detailed analysis of ligand-receptor binding revealed critical amino acid residues involved in this molecular recognition process.…”