Kugawa Mai, Kawakami Kouki, Kise Ryoji, Suomivuori Carl-Mikael, Tsujimura Masaki, Kobayashi Kazuhiro, Kojima Asato, Inoue Wakana J, Fukuda Masahiro, Matsui Toshiki E, Fukunaga Ayami, Koyanagi Junki, Kim Suhyang, Ikeda Hisako, Yamashita Keitaro, Saito Keisuke, Ishikita Hiroshi, Dror Ron O, Inoue Asuka, Kato Hideaki E
Research Center for Advanced Science and Technology, The University of Tokyo, Meguro, Tokyo, Japan.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan.
Nat Commun. 2025 Mar 26;16(1):2809. doi: 10.1038/s41467-025-57983-4.
The free fatty acid receptor 2 (FFA2) is a G protein-coupled receptor (GPCR) that selectively recognizes short-chain fatty acids to regulate metabolic and immune functions. As a promising therapeutic target, FFA2 has been the focus of intensive development of synthetic ligands. However, the mechanisms by which endogenous and synthetic ligands modulate FFA2 activity remain unclear. Here, we present the structures of the human FFA2-Gi complex activated by the synthetic orthosteric agonist TUG-1375 and the positive allosteric modulator/allosteric agonist 4-CMTB, along with the structure of the inactive FFA2 bound to the antagonist GLPG0974. Structural comparisons with FFA1 and mutational studies reveal how FFA2 selects specific fatty acid chain lengths. Moreover, our structures reveal that GLPG0974 functions as an allosteric antagonist by binding adjacent to the orthosteric pocket to block agonist binding, whereas 4-CMTB binds the outer surface of transmembrane helices 6 and 7 to directly activate the receptor. Supported by computational and functional studies, these insights illuminate diverse mechanisms of ligand action, paving the way for precise GPCR-targeted drug design.
游离脂肪酸受体2（FFA2）是一种G蛋白偶联受体（GPCR），可选择性识别短链脂肪酸以调节代谢和免疫功能。作为一个有前景的治疗靶点，FFA2一直是合成配体密集开发的重点。然而，内源性和合成配体调节FFA2活性的机制仍不清楚。在这里，我们展示了由合成的正构激动剂TUG-1375和正变构调节剂/变构激动剂4-CMTB激活的人FFA2-Gi复合物的结构，以及与拮抗剂GLPG0974结合的无活性FFA2的结构。与FFA1的结构比较和突变研究揭示了FFA2如何选择特定的脂肪酸链长度。此外，我们的结构表明，GLPG0974通过结合在正构口袋附近来阻断激动剂结合，从而作为变构拮抗剂发挥作用，而4-CMTB则结合跨膜螺旋6和7的外表面以直接激活受体。在计算和功能研究的支持下，这些见解阐明了配体作用的多种机制，为精确的GPCR靶向药物设计铺平了道路。
