Angiotensin II activates Ca 1.2 Ca channels through β-arrestin2 and casein kinase 2 in mouse immature cardiomyocytes.

Key Points: Angiotensin II (AngII) is crucial in cardiovascular regulation in perinatal mammalians. Here we show that AngII increases twitch Ca transients of mouse immature but not mature cardiomyocytes by robustly activating Ca 1.2 L-type Ca channels through a novel signalling pathway involving angiotensin type 1 (AT ) receptors, β-arrestin2 and casein kinase 2. A β-arrestin-biased AT receptor agonist, TRV027, was as effective as AngII in activating L-type Ca channels. Our results help understand the molecular mechanism by which AngII regulates the perinatal circulation and also suggest that β-arrestin-biased AT receptor agonists may be valuable therapeutics for paediatric heart failure.

Abstract: Angiotensin II (AngII), the main effector peptide of the renin-angiotensin system, plays important roles in cardiovascular regulation in the perinatal period. Despite the well-known stimulatory effect of AngII on vascular contraction, little is known about regulation of contraction of the immature heart by AngII. Here we found that AngII significantly increased the peak amplitude of twitch Ca transients by robustly activating L-type Ca 1.2 Ca (Ca 1.2) channels in mouse immature but not mature cardiomyocytes. This response to AngII was mediated by AT receptors and β-arrestin2. A β-arrestin-biased AT receptor agonist was as effective as AngII in activating Ca 1.2 channels. Src-family tyrosine kinases (SFKs) and casein kinase 2α'β (CK2α'β) were sequentially activated when AngII activated Ca 1.2 channels. A cyclin-dependent kinase inhibitor, p27 (p27), inhibited CK2α'β, and AngII removed this inhibitory effect through phosphorylating tyrosine 88 of p27 via SFKs in cardiomyocytes. In a human embryonic kidney cell line, tsA201 cells, overexpression of CK2α'β but not c-Src directly activated recombinant Ca 1.2 channels composed of C-terminally truncated α , the distal C-terminus of α , β and α δ subunits, by phosphorylating threonine 1704 located at the interface between the proximal and the distal C-terminus of Ca 1.2α subunits. Co-immunoprecipitation revealed that Ca 1.2 channels, CK2α'β and p27 formed a macromolecular complex. Therefore, stimulation of AT receptors by AngII activates Ca 1.2 channels through β-arrestin2 and CK2α'β, thereby probably exerting a positive inotropic effect in the immature heart. Our results also indicated that β-arrestin-biased AT receptor agonists may be used as valuable therapeutics for paediatric heart failure in the future.