β₁ adrenergic receptors (β₁ARs) are central regulators of cardiac function and a drug target for cardiac disease. As a member of the G protein–coupled receptor family, β₁ARs activate cellular signaling by primarily coupling to Gs proteins to activate adenylyl cyclase, cAMP-dependent pathways, and the multifunctional adaptor-transducer protein β-arrestin. Carvedilol, a traditional β-blocker widely used in treating high blood pressure and heart failure by blocking β adrenergic receptor–mediated G protein activation, can selectively stimulate Gs-independent β-arrestin signaling of β adrenergic receptors, a process known as β-arrestin–biased agonism. Recently, a DNA-encoded small-molecule library screen against agonist-occupied β₂ adrenergic receptors (β₂ARs) identified Compound-6 (Cmpd-6) to be a positive allosteric modulator for agonists on β₂ARs. Intriguingly, it was further discovered that Cmpd-6 is positively cooperative with the β-arrestin–biased ligand carvedilol at β₂ARs. Here we describe the surprising finding that at β₁ARs unlike β₂ARs, Cmpd-6 is cooperative only with carvedilol and not agonists. Cmpd-6 increases the binding affinity of carvedilol for β₁ARs and potentiates carvedilol-stimulated, β-arrestin–dependent β₁AR signaling, such as epidermal growth factor receptor transactivation and extracellular signal-regulated kinase activation, whereas it does not have an effect on Gs-mediated cAMP generation. In vivo, Cmpd-6 enhances the antiapoptotic, cardioprotective effect of carvedilol in response to myocardial ischemia/reperfusion injury. This antiapoptotic role of carvedilol is dependent on β-arrestins since it is lost in mice with myocyte-specific deletion of β-arrestins. Our findings demonstrate that Cmpd-6 is a selective β-arrestin–biased allosteric modulator of β₁ARs and highlight its potential clinical utility in enhancing carvedilol-mediated cardioprotection against ischemic injury.

中文翻译：

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β-抑制蛋白偏向变构调节剂增强卡维地洛刺激的β肾上腺素能受体心脏保护作用

β ₁肾上腺素能受体 ( β ₁ ARs) 是心脏功能的中枢调节剂和心脏病的药物靶点。作为 G 蛋白偶联受体家族的一员，β ₁ AR 主要通过与 Gs 蛋白偶联以激活腺苷酸环化酶、cAMP 依赖性通路和多功能衔接子转导蛋白β-抑制蛋白来激活细胞信号传导。卡维地洛是一种传统的β受体阻滞剂，通过阻断β肾上腺素能受体介导的 G 蛋白激活而广泛用于治疗高血压和心力衰竭，可选择性刺激 β 的 Gs 非依赖性β抑制蛋白信号传导肾上腺素能受体，一个称为β-抑制蛋白偏向激动的过程。最近，针对激动剂占据的β ₂肾上腺素能受体 ( β ₂ AR) 的 DNA 编码小分子文库筛选鉴定出化合物 6 (Cmpd-6) 是β ₂ AR 上激动剂的正变构调节剂。有趣的是，进一步发现 Cmpd-6在β ₂ ARs与β -arrestin 偏向配体卡维地洛呈正合作。在这里，我们描述了一个令人惊讶的发现，即在β ₁ ARs 与β ₂ ARs 不同，Cmpd-6 仅合作用卡维地洛而不是激动剂。Cmpd-6 增加卡维地洛对​​β ₁ AR 的结合亲和力并增强卡维地洛刺激的、β-抑制蛋白依赖性β ₁ AR 信号，例如表皮生长因子受体反式激活和细胞外信号调节激酶激活，而它不具有对 Gs 介导的 cAMP 生成的影响。在体内，Cmpd-6 增强卡维地洛响应心肌缺血/再灌注损伤的抗细胞凋亡、心脏保护作用。卡维地洛的这种抗细胞凋亡作用依赖于β -arrestins，因为它在具有肌细胞特异性β -arrestins缺失的小鼠中消失。我们的研究结果表明 Cmpd-6 是一种选择性的β -arrestin 偏向β ₁ ARs 的变构调节剂，并强调其在增强卡维地洛介导的心脏保护作用以对抗缺血性损伤方面的潜在临床效用。