Lillo Jaume, García-Pérez Irene, Lillo Alejandro, Serrano-Marín Joan, Martínez-Pinilla Eva, Navarro Gemma, Franco Rafael
Department of Biochemistry and Physiology, School of Pharmacy and Food Science, Universitat de Barcelona, Barcelona, Spain.
CiberNed, Network Center for Neurodegenerative Diseases, National Spanish Health Institute Carlos III, Madrid, Spain.
Front Pharmacol. 2023 May 17;14:1108617. doi: 10.3389/fphar.2023.1108617. eCollection 2023.
Heteromer formation is unknown for the olfactory family of G protein-coupled receptors (GPCRs). We here identified, in a heterologous system, heteromers formed by the adenosine A receptor (AR), which is a target for neuroprotection, and an olfactory receptor. AR interacts with the receptor family 51, subfamily E, member 2 (OR51E2), the human ortholog of the mouse Olfr-78, whose mRNA is differentially expressed in activated microglia treated with adenosine receptor ligands. Bioluminescence resonance energy transfer (BRET) assays were performed in HEK-293T cells expressing the human version of the receptors, OR51E2 and AR, fused, respectively, to (RLuc) and the yellow fluorescent protein (YFP). BRET data was consistent with a receptor-receptor interaction whose consequences at the functional level were measured by cAMP level determination in CHO cells. Results showed an olfactory receptor-mediated partial blockade of G coupling to the AR, i.e., the effect of the AR selective agonist on intracellular levels of cAMP was significantly reduced. Two odorants, menthol and 1,8-cineole, which failed to show G-mediated OR51E2 activation because they did not increase cytosolic cAMP levels, reduced the BRET readings in cells expressing AR-YFP and OR51E2-Rluc, most likely suggesting a conformational change of at least one receptor. These odorants led to an almost complete block of AR coupling to G.
G蛋白偶联受体（GPCR）嗅觉家族中异源二聚体的形成情况尚不清楚。我们在此异源系统中鉴定出由腺苷A受体（AR，一种神经保护靶点）和一种嗅觉受体形成的异源二聚体。AR与受体家族51、亚家族E、成员2（OR51E2）相互作用，OR51E2是小鼠Olfr-78的人类直系同源物，其mRNA在用腺苷受体配体处理的活化小胶质细胞中差异表达。在分别与人源化受体OR51E2和AR融合了海肾荧光素酶（RLuc）和黄色荧光蛋白（YFP）的HEK-293T细胞中进行了生物发光共振能量转移（BRET）分析。BRET数据与受体-受体相互作用一致，其在功能水平上的后果通过在CHO细胞中测定cAMP水平来衡量。结果显示，一种嗅觉受体介导了对G与AR偶联的部分阻断，即AR选择性激动剂对细胞内cAMP水平的作用显著降低。两种气味剂薄荷醇和1,8-桉叶素，由于它们没有增加胞质cAMP水平，未能显示出G介导的OR51E2激活，但降低了表达AR-YFP和OR51E2-Rluc的细胞中的BRET读数，这很可能表明至少一种受体发生了构象变化。这些气味剂导致AR与G的偶联几乎完全被阻断。
