Rudolf Schönheimer Institute of Biochemistry, Medical Faculty, Leipzig University, Johannisallee 30, 04103, Leipzig, Germany.
Rudolf Boehm Institute of Pharmacology and Toxicology, Medical Faculty, Leipzig University, Härtelstraße 16-18, 04107, Leipzig, Germany.
Cell Commun Signal. 2020 Feb 26;18(1):31. doi: 10.1186/s12964-020-0516-2.
Medium-chain fatty acids and their 3-hydroxy derivatives are metabolites endogenously produced in humans, food-derived or originating from bacteria. They activate G protein-coupled receptors, including GPR84 and HCA, which regulate metabolism and immune functions. Although both receptors are coupled to G proteins, share at least one agonist and show overlapping tissue expression, GPR84 exerts pro-inflammatory effects whereas HCA is involved in anti-inflammatory responses. Here, we analyzed signaling kinetics of both HCA and GPR84, to unravel signal transduction components that may explain their physiological differences.
To study the signaling kinetics and components involved in signal transduction of both receptors we applied the label-free dynamic mass redistribution technology in combination with classical cAMP, ERK signaling and β-arrestin-2 recruitment assays. For phenotypical analyses, we used spheroid cell culture models.
We present strong evidence for a natural biased signaling of structurally highly similar agonists at HCA and GPR84. We show that HCA signaling and trafficking depends on dynamin-2 function. Activation of HCA by 3-hydroxyoctanoic acid but not 3-hydroxydecanoic acid leads to β-arrestin-2 recruitment, which is relevant for cell-cell adhesion. GPR84 stimulation with 3-hydroxydecanoic acid causes a sustained ERK activation but activation of GPR84 is not followed by β-arrestin-2 recruitment.
In summary, our results highlight that biased agonism is a physiological property of HCA and GPR84 with relevance for innate immune functions potentially to differentiate between endogenous, non-pathogenic compounds and compounds originating from e.g. pathogenic bacteria. Video Abstract.
中链脂肪酸及其 3- 羟基衍生物是人体内源性产生的、食物来源的或源自细菌的代谢物。它们激活 G 蛋白偶联受体，包括 GPR84 和 HCA，这些受体调节代谢和免疫功能。尽管这两种受体都与 G 蛋白偶联，但至少有一种激动剂共享，并表现出重叠的组织表达，GPR84 发挥促炎作用，而 HCA 参与抗炎反应。在这里，我们分析了 HCA 和 GPR84 的信号转导动力学，以揭示可能解释它们生理差异的信号转导成分。
为了研究这两种受体的信号转导动力学和相关成分，我们应用了无标记动态质量重分布技术，结合经典的 cAMP、ERK 信号和β-arrestin-2 招募测定。为了进行表型分析，我们使用了球体细胞培养模型。
我们提供了强有力的证据，证明在 HCA 和 GPR84 上，结构高度相似的激动剂具有天然的偏向性信号转导。我们表明，HCA 的信号转导和转运依赖于 dynamin-2 功能。3-羟基辛酸而非 3- 羟基癸酸激活 HCA 会导致β-arrestin-2 的募集，这与细胞间粘附有关。3-羟基癸酸刺激 GPR84 会导致持续的 ERK 激活，但 GPR84 的激活不会导致β-arrestin-2 的募集。
总之，我们的结果强调了偏向激动剂是 HCA 和 GPR84 的一种生理特性，这与先天免疫功能有关，可能有助于区分内源性、非致病性化合物和源自致病性细菌的化合物。视频摘要。
