Shi Qian, Li Minghui, Mika Delphine, Fu Qin, Kim Sungjin, Phan Jason, Shen Ao, Vandecasteele Gregoire, Xiang Yang K
Department of Pharmacology, University of California at Davis, Davis, CA 95616, USA.
Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing 210001, China.
Cardiovasc Res. 2017 May 1;113(6):656-670. doi: 10.1093/cvr/cvx036.
Cardiac β-adrenergic receptor (βAR) signalling is susceptible to heterologous desensitization by different neurohormonal stimuli in clinical conditions associated with heart failure. We aim to examine the underlying mechanism of cross talk between βARs and a set of G-protein coupled receptors (GPCRs) activated by hormones/agonists.
Rat ventricular cardiomyocytes were used to determine heterologous phosphorylation of βARs under a series of GPCR agonists. Activation of Gs-coupled dopamine receptor, adenosine receptor, relaxin receptor and prostaglandin E2 receptor, and Gq-coupled α1 adrenergic receptor and angiotensin II type 1 receptor promotes phosphorylation of β1AR and β2AR at putative protein kinase A (PKA) phosphorylation sites; but activation of Gi-coupled α2 adrenergic receptor and activation of protease-activated receptor does not. The GPCR agonists that promote β2AR phosphorylation effectively inhibit βAR agonist isoproterenol-induced PKA phosphorylation of phospholamban and contractile function in ventricular cardiomyocytes. Heterologous GPCR stimuli have minimal to small effect on isoproterenol-induced β2AR activation and G-protein coupling for cyclic adenosine monophosphate (cAMP) production. However, these GPCR stimuli significantly promote phosphorylation of phosphodiesterase 4D (PDE4D), and recruit PDE4D to the phosphorylated β2AR in a β-arrestin 2 dependent manner without promoting β2AR endocytosis. The increased binding between β2AR and PDE4D effectively hydrolyzes cAMP signal generated by subsequent stimulation with isoproterenol. Mutation of PKA phosphorylation sites in β2AR, inhibition of PDE4, or genetic ablation of PDE4D or β-arrestin 2 abolishes this heterologous inhibitory effect. Ablation of β-arrestin 2 or PDE4D gene also rescues β-adrenergic stimuli-induced myocyte contractile function.
These data reveal essential roles of β-arrestin 2 and PDE4D in a common mechanism for heterologous desensitization of cardiac βARs under hormonal stimulation, which is associated with impaired cardiac function during the development of pathophysiological conditions.
在与心力衰竭相关的临床情况下，心脏β-肾上腺素能受体（βAR）信号传导易受不同神经激素刺激的异源脱敏作用影响。我们旨在研究βAR与一组由激素/激动剂激活的G蛋白偶联受体（GPCR）之间相互作用的潜在机制。
使用大鼠心室心肌细胞来确定一系列GPCR激动剂作用下βAR的异源磷酸化情况。激活与Gs偶联的多巴胺受体、腺苷受体、松弛素受体和前列腺素E2受体，以及与Gq偶联的α1肾上腺素能受体和血管紧张素II 1型受体，可促进β1AR和β2AR在假定的蛋白激酶A（PKA）磷酸化位点的磷酸化；但激活与Gi偶联的α2肾上腺素能受体和蛋白酶激活受体则不会。促进β2AR磷酸化的GPCR激动剂可有效抑制βAR激动剂异丙肾上腺素诱导的心室心肌细胞中受磷蛋白的PKA磷酸化及收缩功能。异源GPCR刺激对异丙肾上腺素诱导的β2AR激活和环磷酸腺苷（cAMP）产生的G蛋白偶联作用影响极小或较小。然而，这些GPCR刺激可显著促进磷酸二酯酶4D（PDE4D）的磷酸化，并以β-抑制蛋白2依赖性方式将PDE4D募集到磷酸化的β2AR上，而不会促进β2AR内吞。β2AR与PDE4D之间结合的增加有效地水解了随后异丙肾上腺素刺激产生的cAMP信号。β2AR中PKA磷酸化位点的突变、PDE4的抑制或PDE4D或β-抑制蛋白2的基因敲除可消除这种异源抑制作用。β-抑制蛋白2或PDE4D基因的敲除也可挽救β-肾上腺素能刺激诱导的心肌细胞收缩功能。
这些数据揭示了β-抑制蛋白2和PDE4D在激素刺激下心脏βAR异源脱敏的共同机制中的重要作用，这与病理生理状态发展过程中心脏功能受损有关。
