GAIN Domain Dynamics And Its Relevance For Adhesion GPCR Signaling<i>In Vivo</i>

In the past few years, several members of the Adhesion G-Protein-coupled receptor (aGPCR) family have been described as putative metabotropic mechanosensors. However, the molecular details of how aGPCR contribute to mechanosensing remain elusive. As part of their extracellular region aGPCR contain an evolutionarily conserved GPCR autoproteolysis inducing (GAIN) domain. Recent Molecular Dynamics (MD) simulations of GAIN domains from different mammalian aGPCR identified two flexible regions, termed flaps. Movement of these flaps were hypothesized to promote accessibility of a tethered agonist that can induce receptor activity. To test this hypothesis in vivo, we used MD simulations to predict GAIN domain residues that might alter the flexibility of the flaps and thus the activity profile of the Latrophilin homologue Cirl in Drosophila melanogaster. Guided by these predictions, we generated transgenes expressing Cirl with such GAIN mutations, referred to as Cirl flap mutants, from the endogenous locus and subjected them to genetic, behavioral, biochemical and functional analyses. Our analyses consistently suggests that single or double residue modifications within Cirl’s GAIN domain, even at supposedly critical positions, has no impact on receptor function in vivo. We conclude that the GAIN domain is functionally robust, supporting its pivotal role in trafficking and functional regulation of aGPCR. Funding source: German Research Council, CRC 1423, project number 421152132, subproject B06 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.