Biased activation of β(2)-AR/Gi/GRK2 signal pathway attenuated β(1)-AR sustained activation induced by β(1)-adrenergic receptor autoantibody

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