ß1-adrenoceptor Arg389Gly polymorphism confers differential ß-arrestin-binding tropism in cardiac myocytes.

AIM: The ß1-adrenergic receptor (AR) Arg389Gly polymorphism affects efficacy of its procontractile signaling in cardiomyocytes and carriers' responses to ß-blockers. To identify molecular mechanisms underlying functional differences between Arg389 and Gly389 ß1ARs, we examined their binding to ß-arrestins (ßarr-1 and -2), which mediate ß1AR signaling, in neonatal rat ventricular myocytes. METHODS: We tested the ß1AR-ßarr interaction via ß1AR immunoprecipitation followed by ßarr immunoblotting. RESULTS: ßarr1 binds both variants upon isoproterenol, carvedilol or metoprolol treatment in neonatal rat ventricular myocytes. Conversely, the potentially beneficial in the heart ßarr2 only interacts with the Arg389 receptor in response to isoproterenol or carvedilol. CONCLUSION: Arg389 confers unique ßarr2-interacting tropism to the ß1AR in cardiac myocytes, potentially underlying this variant's gain-of-function phenotype and better clinical responses to ß-blockers.

Structure-activity relationship study of angiotensin II analogs in terms of ß-arrestin-dependent signaling to aldosterone production.

The known angiotensin II (AngII) physiological effect of aldosterone synthesis and secretion induction, a steroid hormone that contributes to the pathology of postmyocardial infarction (MI) heart failure (HF), is mediated by both Gq/11 proteins and ß-arrestins, both of which couple to the AngII type 1 receptors (AT1Rs) of adrenocortical zona glomerulosa (AZG) cells. Over the past several years, AngII analogs with increased selectivity ("bias") toward ß-arrestin-dependent signaling at the AT1R have been designed and described, starting with SII, the gold-standard ß-arrestin-"biased" AngII analog. In this study, we examined the relative potencies of an extensive series of AngII peptide analogs at relative activation of G proteins versus ß-arrestins by the AT1R. The major structural difference of these peptides from SII was their varied substitutions at position 5, rather than position 4 of native AngII. Three of them were found biased for ß-arrestin activation and extremely potent at stimulating aldosterone secretion in AZG cells in vitro, much more potent than SII in that regard. Finally, the most potent of these three ([Sar(1), Cys(Et)(5), Leu(8)]-AngII, CORET) was further examined in post-MI rats progressing to HF and overexpressing adrenal ß-arrestin1 in vivo. Consistent with the in vitro studies, CORET was found to exacerbate the post-MI hyperaldosteronism, and, consequently, cardiac function of the post-MI animals in vivo. Finally, our data suggest that increasing the size of position 5 of the AngII peptide sequence results in directly proportional increases in AT1R-dependent ß-arrestin activation. These findings provide important insights for AT1R pharmacology and future AngII-targeted drug development.

Suppression of adrenal ßarrestin1-dependent aldosterone production by ARBs: head-to-head comparison.

The known angiotensin II (AngII) physiological effect of aldosterone synthesis and secretion is mediated by either Gq/11 proteins or ßarrestin1 (ßarr1), both of which can couple to its type 1 receptors (AT1Rs), present in adrenocortical zona glomerulosa (AZG) cell membranes. In the present study, we examined the relative potencies of all the currently used in the clinic AT1R antagonist drugs (angiotensin receptor blockers, ARBs, or sartans) at preventing activation of these two signaling mediators (G proteins and ßarrs) at the AngII-bound AT1R and, consequently, at suppression of aldosterone in vitro. All ARBs were found to be potent inhibitors of G protein activation at the AT1R. However, candesartan and valsartan were the most potent at blocking AngII-induced ßarr activation at this receptor, among the tetrazolo-biphenyl-methyl derivatives, translating into excellent efficacies at aldosterone suppression in H295R cells. Conversely, irbesartan and losartan were largely G protein-selective inhibitors at the AT1R, with very low potency towards ßarr inhibition. As a result, they were very weak suppressors of ßarr1-dependent aldosterone production in H295R cells. These findings provide important pharmacological insights into the drug class of ARBs and medicinal chemistry insights for future drug development in the field of AngII antagonism.