Monovalent cation and amiloride analog modulation of adrenergic ligand binding to the unglycosylated α(2B)-adrenergic receptor subtype

The unglycosylated α(2B) subtype of the α₂-adrenergic receptor found in NG-108-15 cells possesses allosteric regulation of adrenergic ligand binding by monovalent cations and 5-amino-substituted amiloride analogs. These findings demonstrate that allosteric modulation of adrenergic ligand binding is not a property unique to the α(2A) subtype. The observation that amiloride analogs as well as monovalent cations can modulate adrenergic ligand binding to the nonglycosylated α(2B) subtype indicates that charge shielding due to carbohydrate moieties does not play a role in this allosteric modulation but, rather, these regulatory effects result from interactions of cations and amiloride analogs with the protein moiety of the receptor. Furthermore, the observation that both α(2A) and α(2B) receptor subtypes are modulated by amiloride analogs suggests that structural domains that are conserved between the two are likely to be involved in this allosteric modulation.