D-amino acid-substituted atrial natriuretic peptide analogs reveal novel receptor recognition requirements.

Abstract

The introduction of D-amino acid residues into peptide hormones has been traditionally utilized in structure-activity studies to probe the conformational requirements of ligand-receptor interactions.A study was undertaken to examine the effect of D-amino acid substitutions into the atrial natriuretic peptide molecule on interactions with distinct subpopulations of specific membrane-associated receptors of bovine aortic smooth muscle cells.Competitive binding analysis revealed that each of 15 synthetic D-aminO acid-substituted analogs showed comparable affinities for C-ANP receptors, a class of specific receptors which have been proposed to mediate the sequestration and metabolic clearance of ANP.The relative affinities of all 15 analogs did not differ more than 10-fold.In contrast, the interaction of the ANP analogs with a second receptor pool (B-ANP receptors), which is coupled to the stimulation of particulate guanylate cyclase, varied over a 1000-fold range of potency consistent with expectations for a receptor that displays rigorous conformational specificity.The indiscriminant selectivity of C-ANP receptors for D-amino acid-substituted ANP analogs is unprecedented for hormone receptors involved in biological signal transduction.These results, when coupled with the inability to correlate any direct in vitro biological effect associated with C-ANP receptor occupancy supports the hypothesis that the C-ANP receptor protein is a novel transport protein involved in the metabolic clearance of ANP.Atrial natriuretic peptide (ANP)' is a hormone that regulates blood pressure and extracellular fluid volume.Specific receptors for ANP have been identified in numerous target cells and tissues, including endothelial and smooth muscle cells of the vasculature, epithelial and mesangial cells of the renal glomerulus, the renal papilla, the adrenal, the pituitary, and various regions of the brain (1).A broad role for ANP in regulating cardiovascular homeostasis is inferred by this widespread distribution of specific receptors.Recent investigations have demonstrated that the ANP receptor population is heterogenous (2-6).Pharmacological and biochemical studies have led to the identification of at