Prolonged AT₁R activation induces Ca_V1.2 channel internalization in rat cardiomyocytes

The cardiac L-type calcium channel is a multi-subunit complex that requires co-assembling of the pore-forming subunit Ca_V1.2 with auxiliary subunits Ca_Vα₂δ and Ca_Vβ. Its traffic has been shown to be controlled by these subunits and by the activation of various G-protein coupled receptors (GPCR). Here, we explore the consequences of the prolonged activation of angiotensin receptor type 1 (AT₁R) over Ca_V1.2 channel trafficking. Bioluminescence Resonance Energy Transfer (BRET) assay between β-arrestin and L-type channels in angiotensin II-stimulated cells was used to assess the functional consequence of AT₁R activation, while immunofluorescence of adult rat cardiomyocytes revealed the effects of GPCR activation on Ca_V1.2 trafficking. Angiotensin II exposure results in β-arrestin₁ recruitment to the channel complex and an apparent loss of Ca_V1.2 immunostaining at the T-tubules. Accordingly, angiotensin II stimulation causes a decrease in L-type current, Ca²⁺ transients and myocyte contractility, together with a faster repolarization phase of action potentials. Our results demonstrate that prolonged AT₁R activation induces β-arrestin₁ recruitment and the subsequent internalization of Ca_V1.2 channels with a half-dose of AngII on the order of 100 nM, suggesting that this effect depends on local renin-angiotensin system. This novel AT₁R-dependent Ca_V1.2-trafficking modulation likely contributes to angiotensin II-mediated cardiac remodeling.