The heptapeptide angiotensin (Ang)-(1-7) is part of the beneficial arm of the renin-angiotensin system. Ang-(1-7) has cardiovascular protective effects, stimulates regeneration, and opposes the often detrimental effects of AngII. We recently identified the G protein-coupled receptors Mas and MrgD as receptors for the heptapeptide. Ala1-Ang-(1-7) (Alamandine), a decarboxylated form of Ang-(1-7), has similar vasorelaxant effects, but has been described as only stimulating MrgD. Therefore, this study aimed to characterise the consequences of the lack of the carboxyl group in amino acid 1 on intracellular signalling and to identify the receptor fingerprint for Ala1-Ang-(1-7). In primary endothelial and mesangial cells, Ala1-Ang-(1-7) elevated cAMP concentration. Dose response curves generated with Ang-(1-7) and Ala1-Ang-(1-7) significantly differed from each other, with a much lower EC50 and a bell-shape curve for Ala1-Ang-(1-7). We provided pharmacological proof that both, Mas and MrgD, are functional receptors for Ala1-Ang-(1-7). Consequently, in primary mesangial cells with genetic deficiency in both receptors, the heptapeptide failed to increase cAMP concentration. As we previously described for Ang-(1-7), the Ala1-Ang-(1-7)-mediated cAMP increase in Mas/MrgD-transfected HEK293 cells and primary cells was blocked by the AT2 receptor blocker, PD123319. The very distinct dose-response curves for both heptapeptides could be explained by in silico modelling, electrostatic potential calculations, and an involvement of Galpha i for higher concentrations of Ala1-Ang-(1-7). Our results identify Ala1-Ang-(1-7) as a peptide with specific pharmacodynamic properties and builds the basis for the design of more potent and efficient Ang-(1-7) analogues for therapeutic intervention in a rapidly growing number of diseases.
Keywords: Ala(1)-Angiotensin-(1–7); Dose-response curve; G-proteins; Mas receptor; MrgD receptor; Renin-angiotensin system.
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