A force-sensitive adhesion GPCR is indispensable in normal equilibrioception

Equilibrioception is essential for the perception and navigation of mammals in the three-dimensional world. A rapid mechanoelectrical transduction (MET) response in vestibular hair cells plays a critical role in positional and motional perception. Here, we identified that the G protein-coupled receptor LPHN2/ADGRL2, which is expressed in the apical membrane of utricular hair cells, is required for maintenance of normal balance. Hair cell-specific Lphn2 deficiency in mice impaired both balance behaviors and MET responses. Functional analyses using Pou4f3-CreER ^+/- ; Lphn2 ^fl/fl mice and LPHN2-specific inhibitors revealed that LPHN2 regulated the tip link-independent MET current at the apical surface of the utricular hair cell by converting force stimuli into transmembrane channel-like protein 1 (TMC1) activity. Force sensation by LPHN2 also induced glutamate release and calcium signaling in utricular hair cells. Reintroduction of LPHN2 into the hair cells of Lphn2-deficient mice restored the vestibular functions and MET responses. Our data suggest an indispensable role for a mechanosensitive GPCR in equilibrioception.