The G protein‐coupled free fatty acid receptor 2 (FFA2R) is highly expressed on neutrophils and was previously described to regulate neutrophil activation. Allosteric targeting of G protein‐coupled receptors (GPCRs) is increasingly explored to create distinct pharmacology compared to endogenous, orthosteric ligands. The consequence of allosteric versus orthosteric FFA2R activation for neutrophil response, however, is currently largely elusive. Here, different FFA2R desensitization profiles in human neutrophils following allosteric or orthosteric activation are reported. Using a set of neutrophil functional assays to measure calcium flux, pERK1/2, chemotaxis, cellular degranulation, and oxidative burst together with holistic and pathway‐unbiased whole cell sensing based on dynamic mass redistribution, it is found that the synthetic positive allosteric modulator agonist 4‐CMTB potently activates neutrophils and simultaneously alters FFA2R responsiveness toward the endogenous, orthosteric agonist propionic acid (C3) after homologous and heterologous receptor desensitization. Stimulation with C3 or the hierarchically superior chemokine receptor activator IL‐8 led to strong FFA2R desensitization and rendered neutrophils unresponsive toward repeated stimulation with C3. In contrast, stimulation with allosteric 4‐CMTB engaged a distinct composition of signaling pathways as compared to orthosteric receptor activation and was able to activate neutrophils that underwent homologous and heterologous desensitization with C3 and IL‐8, respectively. Moreover, allosteric FFA2R activation could re‐sensitize FFA2 toward the endogenous agonist C3 after homologous and heterologous desensitization. Given the fact that receptor desensitization is critical in neutrophils to sense and adapt to their current environment, these findings are expected to be useful for the discovery of novel pharmacological mechanisms to modulate neutrophil responsiveness therapeutically.

中文翻译：

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FFA2 受体 (GPR43) 的变构靶向恢复脱敏的人类中性粒细胞的反应性

G 蛋白偶联游离脂肪酸受体 2 (FFA2R) 在中性粒细胞上高度表达，之前被描述为调节中性粒细胞活化。与内源性正构配体相比，越来越多地探索 G 蛋白偶联受体 (GPCR) 的变构靶向以创造独特的药理学。然而，变构与正构 FFA2R 激活对中性粒细胞反应的影响目前在很大程度上难以捉摸。在这里，报告了变构或正构激活后人中性粒细胞中不同的 FFA2R 脱敏谱。使用一组中性粒细胞功能测定来测量钙通量、pERK1/2、趋化性、细胞脱颗粒和氧化爆发，以及基于动态质量重新分布的整体和无偏向全细胞传感，发现合成的正变构调节剂激动剂 4-CMTB 在同源和异源受体脱敏后有效激活中性粒细胞并同时改变 FFA2R 对内源性正构激动剂丙酸 (C3) 的反应性。用 C3 或分级优越的趋化因子受体激活剂 IL-8 刺激导致强烈的 FFA2R 脱敏并使中性粒细胞对 C3 的重复刺激无反应。相比之下，与正构受体激活相比，变构 4-CMTB 的刺激参与了不同的信号通路组成，并且能够激活分别与 C3 和 IL-8 进行同源和异源脱敏的中性粒细胞。而且，在同源和异源脱敏后，变构 FFA2R 激活可以使 FFA2 重新对内源性激动剂 C3 敏感。鉴于受体脱敏对于中性粒细胞感知和适应其当前环境至关重要，这些发现有望用于发现新的药理机制以在治疗上调节中性粒细胞反应。