ALPHA(1)-ADRENERGIC RECEPTOR SUBTYPE DETERMINANTS FOR 4-PIPERIDYL OXAZOLE ANTAGONISTS

Mutational studies in conjunction with ligand binding assays were used to examine the basis of alpha(1)-adrenergic receptor subtype selectiv ity for a series of 4-piperidyloxazole antagonists. A set of chimeric alpha(1A) receptors were created by systematically substituting indivi dual transmembrane domains from alpha(1D) adrenergic receptors. The ox azole antagonists exhibited significant reductions in affinity against the receptor construct alpha(1A/D)(TM2), and moderate reductions in a ffinity versus constructs alpha(1A/D)(TM5), alpha(1A/B)(TM5), and alph a(1A/D)(TM6) Antagonist affinities for these chimeras exceeded those f ound 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 st udies revealed that mutations at position 86 in the second transmembra ne domain and position 185 in the fifth transmembrane domain of the al pha(1A) receptor have a major impact on receptor subtype selectivity.