Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (Cinvestav), México City, Mexico.
Basic Clin Pharmacol Toxicol. 2023 Oct;133(4):342-352. doi: 10.1111/bcpt.13927. Epub 2023 Aug 1.
Adhesion G protein-coupled receptors (aGPCRs) possess a unique topology, including the presence of a GPCR proteolysis site (GPS), which, upon autoproteolysis, generates two functionally distinct fragments that remain non-covalently associated at the plasma membrane. A proposed activation mechanism for aGPCRs involves the exposure of a tethered agonist, which depends on cleavage at the GPS. However, this hypothesis has been challenged by the observation that non-cleavable aGPCRs exhibit constitutive activity, thus making the function of GPS cleavage widely enigmatic. In this study, we sought to elucidate the function of GPS-mediated cleavage through the study of G protein coupling with Latrophilin-3/ADGRL3, a prototypical aGPCR involved in synapse formation and function. Using BRET-based G protein biosensors, we reveal that an autoproteolysis-deficient mutant of ADGRL3 retains constitutive activity. Surprisingly, we uncover that cleavage deficiency leads to a signalling bias directed at potentiating the activity of select G proteins such as Gi2 and G12/13. These data unveil the underpinnings of biased signalling for aGPCRs defined by GPS autoproteolysis.
黏附 G 蛋白偶联受体 (aGPCR) 具有独特的拓扑结构，包括存在 GPCR 蛋白水解位点 (GPS)，该位点在自身水解作用下生成两个功能上截然不同的片段，在质膜上保持非共价结合。aGPCR 的一种拟议激活机制涉及到被束缚配体的暴露，这取决于 GPS 的切割。然而，这个假设受到了挑战，因为观察到不可切割的 aGPCR 表现出组成型活性，从而使得 GPS 切割的功能广泛神秘。在这项研究中，我们试图通过研究与突触形成和功能有关的 Latrophilin-3/ADGRL3（一种典型的 aGPCR）的 G 蛋白偶联来阐明 GPS 介导的切割的功能。使用基于 BRET 的 G 蛋白生物传感器，我们揭示了 ADGRL3 的一个自身水解缺陷突变体保留组成型活性。令人惊讶的是，我们发现切割缺陷导致信号偏向于增强特定 G 蛋白（如 Gi2 和 G12/13）的活性。这些数据揭示了 GPS 自身水解定义的 aGPCR 偏置信号的基础。
