Tethered agonist activated ADGRF1 structure and signalling analysis reveal basis for G protein coupling

Adhesion G Protein Coupled Receptors (aGPCRs) have evolved an activation mechanism to translate extracellular force into liberation of a tethered agonist (TA) to effect cell signalling. We report here that ADGRF1 can signal through all major G protein classes and identify the structural basis for a previously reported Gaq preference by cryo-EM. Our structure shows that Gaq preference in ADGRF1 may derive from tighter packing at the conserved F569 of the TA, altering contacts between TM helix I and VII, with a concurrent rearrangement ofTMhelix VII and helix VIII at the site of Ga recruitment. Mutational studies of the interface and of contact residues within the 7TM domain identify residues critical for signalling, and suggest that Gas signalling is more sensitive to mutation of TA or binding site residues than Gaq. Our work advances the detailed molecular understanding of aGPCR TA activation, identifying features that potentially explain preferential signal modulation.

Automated summary

This study reveals that ADGRF1 can signal through all major G protein classes and identifies the structural basis for its preference for Gaq through cryo-EM. The preference for Gaq in ADGRF1 may be due to tighter packing at the conserved F569 of the tethered agonist, leading to alterations in contact between TM helix I and VII, as well as rearrangements of TM helix VII and helix VIII at the site of Ga recruitment. Mutational studies of the interface and contact residues within the 7TM domain identify crucial residues for signaling, suggesting that Gas signaling is more sensitive to mutations in the tethered agonist or binding site residues than Gaq. This work advances our understanding of aGPCR tethered agonist activation at a molecular level and provides insights into potential mechanisms underlying preferential signal modulation.