Department of Pharmacology, Columbia University, New York, NY, USA.
Department of Pharmacology, University of California at Davis, Davis, CA, USA.
Sci Rep. 2017 Aug 11;7(1):7890. doi: 10.1038/s41598-017-06607-z.
β-adrenergic receptors (βARs) mediate catecholamine actions in cardiomyocytes by coupling to both Gs/cAMP-dependent and Gs-independent/growth-regulatory pathways. Structural studies of the βAR define ligand-binding sites in the transmembrane helices and effector docking sites at the intracellular surface of the βAR, but the extracellular N-terminus, which is a target for post-translational modifications, typically is ignored. This study identifies βAR N-terminal O-glycosylation at Ser/Ser as a mechanism that prevents βAR N-terminal cleavage. We used an adenoviral overexpression strategy to show that both full-length/glycosylated βARs and N-terminally truncated glycosylation-defective βARs couple to cAMP and ERK-MAPK signaling pathways in cardiomyocytes. However, a glycosylation defect that results in N-terminal truncation stabilizes βARs in a conformation that is biased toward the cAMP pathway. The identification of O-glycosylation and N-terminal cleavage as novel structural determinants of βAR responsiveness in cardiomyocytes could be exploited for therapeutic advantage.
β-肾上腺素能受体（βAR）通过与 Gs/cAMP 依赖性和 Gs 非依赖性/生长调节途径偶联，介导儿茶酚胺在心肌细胞中的作用。βAR 的结构研究定义了跨膜螺旋中的配体结合位点和βAR 细胞内表面的效应器对接位点，但通常忽略了作为翻译后修饰靶点的细胞外 N 端。本研究鉴定了βAR N 端丝氨酸/丝氨酸的 O-糖基化，作为一种防止βAR N 端切割的机制。我们使用腺病毒过表达策略表明，全长/糖基化的βAR 和 N 端截短的糖基化缺陷的βAR 在心肌细胞中都与 cAMP 和 ERK-MAPK 信号通路偶联。然而，导致 N 端截断的糖基化缺陷使βAR 稳定在偏向 cAMP 途径的构象中。在心肌细胞中，O-糖基化和 N 端切割作为βAR 反应性的新型结构决定因素的鉴定，可能被用于治疗优势。
