G-protein-coupled receptors (GPCRs) play an important role in sensing various extracellular stimuli, such as neurotransmitters, hormones, and tastants, and transducing the input information into the cell. While the human genome encodes more than 800 GPCR genes, only four Gα-proteins (Gαs, Gαi/o, Gαq/11, and Gα12/13) are known to couple with GPCRs. It remains unclear how such divergent GPCR information is translated into the downstream G-protein signaling dynamics. To answer this question, we report a live-cell fluorescence imaging system for monitoring GPCR downstream signaling dynamics. Genetically encoded biosensors for cAMP, Ca2+, RhoA, and ERK were selected as markers for GPCR downstream signaling, and were stably expressed in HeLa cells. GPCR was further transiently overexpressed in the cells. As a proof-of-concept, we visualized GPCR signaling dynamics of five dopamine receptors and 12 serotonin receptors, and found heterogeneity between GPCRs and between cells. Even when the same Gα proteins were known to be coupled, the patterns of dynamics in GPCR downstream signaling, including the signal strength and duration, were substantially distinct among GPCRs. These results suggest the importance of dynamical encoding in GPCR signaling.

中文翻译：

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GPCR下游信号动力学的定量活细胞成像

G 蛋白偶联受体 (GPCR) 在感知各种细胞外刺激（如神经递质、激素和促味剂）以及将输入信息转入细胞中发挥着重要作用。虽然人类基因组编码超过 800 个 GPCR 基因，但已知只有四种 Gα 蛋白（Gαs、Gαi/o、Gαq/11 和 Gα12/13）与 GPCR 偶联。目前尚不清楚这种不同的 GPCR 信息是如何转化为下游 G 蛋白信号动力学的。为了回答这个问题，我们报告了一种用于监测 GPCR 下游信号动力学的活细胞荧光成像系统。cAMP、Ca2+、RhoA 和 ERK 的基因编码生物传感器被选为 GPCR 下游信号转导的标记，并在 HeLa 细胞中稳定表达。GPCR 在细胞中进一步瞬时过表达。作为概念验证，我们可视化了 5 种多巴胺受体和 12 种血清素受体的 GPCR 信号动力学，发现 GPCR 之间和细胞之间存在异质性。即使已知相同的 Gα 蛋白是偶联的，GPCR 下游信号的动力学模式，包括信号强度和持续时间，在 GPCR 之间也基本不同。这些结果表明动态编码在 GPCR 信号传导中的重要性。