Biased Signaling is Structurally Encoded As An Autoproteolysis Event in Adhesion G Protein-Coupled Receptor Latrophilin-3/ADGRL3

Abstract

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 release 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 signaling bias directed at potentiating the activity of select G proteins such as G and G. These data unveil the underpinnings of biased signaling for aGPCRs defined by GPS autoproteolysis.

Adhesion G protein‐coupled receptor's structure, function and role in biology—Status from the 10th adhesion GPCR workshop in Copenhagen, 2022

“…Thorough signalling profiling requires assays that cover the full panel of G protein signalling pathways, which previously has been challenging for receptors coupled to the G12/13 pathway due to a lack of efficient and pathway‐specific downstream assays. In this issue, Faas et al (Rosenkilde group) 23 describe a new strategy for detecting ADGRG1 G12/13 signalling, which nicely complement the BRET strategies laid forward by Cevheroğlu et al 22 and Ojeda‐Muñiz et al 21 Using chimeric G proteins, Faas and co‐workers reroute GPR56 G12/13 signalling activity to a convenient Gq readout and show that synthetic Stachel peptide ligands in combination with these chimeras enhance the signalling in conventional gene transcription factor and second messenger assays. As such, the authors offer an additional readout for signalling profiling of adhesion GPCRs in the G12/13 pathway.…”

“…Many, but not all adhesion GPCRs, have been shown to be autoproteolytically cleaved at the GPS site, 3 and the impact of this phenomenon, along with the rational design of cleavage deficient mutations, was covered by several talks and posters at the meeting. In this special issue, Ojeda‐Muñiz and co‐workers (Boucard group) 21 sought to investigate the impact of GPS cleavage on ADGRL3 (latrophilin‐3) G protein activation. Using a panel of BRET sensors, the authors systematically compare the signalling capabilities for full‐length ADGRL3 and a cleavage‐deficient mutant.…”

Welcome to Basic & Clinical Pharmacology & Toxicology 2024

“…As we embark on the new year, we invite you to explore the wealth of knowledge and exciting content our journal offers. In 2023, we published three Special Collections from focused conferences supported by the Nordic Association for the Publication of Basic and Clinical Pharmacology and Toxicology, including Adhesion G‐Protein‐coupled Receptors, 1–10 Transmembrane Transporter Proteins: Catching Transport in Motion 11–19 and Advancing Deprescribing: Learnings from the first International Conference on Deprescribing 20–31 . The second part of the latter Special Collection will appear in the January 2024 issue.…”