Biased activation of β2-AR/Gi/GRK2 signal pathway attenuated β1-AR sustained activation induced by β1-adrenergic receptor autoantibody

Heart failure is the terminal stage of many cardiac diseases, in which beta(1)-adrenoceptor (beta(1)-AR) autoantibody (beta(1)-AA) has a causative role. By continuously activating beta(1)-AR, beta(1)-AA can induce cytotoxicity, leading to cardiomyocyte apoptosis and heart dysfunction. However, the mechanism underlying the persistent activation of beta(1)-AR by beta(1)-AA is not fully understood. Receptor endocytosis has a critical role in terminating signals over time. beta(2)-adrenoceptor (beta(2)-AR) is involved in the regulation of beta(1)-AR signaling. This research aimed to clarify the mechanism of the beta(1)-AA-induced sustained activation of beta(1)-AR and explore the role of the beta(2)-AR/Gi-signaling pathway in this process. The beating frequency of neonatal rat cardiomyocytes, cyclic adenosine monophosphate content, and intracellular Ca2+ levels were examined to detect the activation of beta(1)-AA. Total internal reflection fluorescence microscopy was used to detect the endocytosis of beta(1)-AR. ICI118551 was used to assess beta(2)-AR/Gi function in beta(1)-AR sustained activation induced by beta(1)-AA in vitro and in vivo. Monoclonal beta(1)-AA derived from a mouse hybridoma could continuously activate beta(1)-AR. beta(1)-AA-restricted beta(1)-AR endocytosis, which was reversed by overexpressing the endocytosis scaffold protein beta-arrestin1/2, resulting in the cessation of beta(1)-AR signaling. beta(2)-AR could promote beta(1)-AR endocytosis, as demonstrated by overexpressing/interfering with beta(2)-AR in HL-1 cells, whereas beta(1)-AA inhibited the binding of beta(2)-AR to beta(1)-AR, as determined by surface plasmon resonance. ICI118551 biasedly activated the beta(2)-AR/Gi/G protein-coupled receptor kinase 2 (GRK2) pathway, leading to the arrest of limited endocytosis and continuous activation of beta(1)-AR by beta(1)-AA in vitro. In vivo, ICI118551 treatment attenuated myocardial fiber rupture and left ventricular dysfunction in beta(1)-AA-positive mice. This study showed that beta(1)-AA continuously activated beta(1)-AR by inhibiting receptor endocytosis. Biased activation of the beta(2)-AR/Gi/GRK2 signaling pathway could promote beta(1)-AR endocytosis restricted by beta(1)-AA, terminate signal transduction, and alleviate heart damage.

Automated summary

This study revealed that beta(1)-AA continuously activates beta(1)-AR by inhibiting receptor endocytosis. Biased activation of the beta(2)-AR/Gi/GRK2 signaling pathway can promote beta(1)-AR endocytosis restricted by beta(1)-AA, terminate signal transduction, and alleviate heart damage.