Dual-mode intramolecular agonist-dependent mechanoactivation of the adhesion GPCR ADGRG1/GPR56

Mechanical stimuli instruct cardinal cellular decisions pertaining to their fate, proliferation, morphology, and movement ^1,2 . How adhesion G protein-coupled receptors (aGPCRs), a large family of mechanosensors with more than 30 members in humans ^3–5 , transduce mechanical cues into metabotropic commands, has been a matter of debate due to the lack of suitable approaches to analyze receptor activation during mechanotransduction in live cells ⁶ . Here we use human ADGRG1/GPR56 (G1), an aGPCR with roles in brain development ⁷ , skeletal muscle ⁸ , and platelet function ⁹ , to study the events during aGPCR mechanotransduction. We show that G1 dissociation, taking place at ∼18 pN (ref. ¹⁰ ), occurs at retracting fibers during cell migration over an adhesive substrate ¹¹ , an effect that can be enhanced by cell stretching. Simultaneous live recording of G protein recruitment through total internal reflection fluorescence (TIRF) imaging and pharmacological assays during force transmission onto G1 show graded receptor responses with sub-maximal signaling before receptor dissociation, and maximal activation thereafter. Both modes require the intramolecular agonist/Stachel element ^12,13 of the receptor. Our findings demonstrate that non-dissociative and dissociative aGPCR signaling can emerge from the same aGPCR depending on mechanical stimulus magnitude, demonstrating the capability of aGPCRs for graded receptor responses upon force detection.