Branched Photoswitchable Tethered Ligands Enable Ultra-efficient Optical Control and Detection of G Protein-Coupled Receptors In Vivo

The limitations of classical drugs have spurred the development of covalently tethered photoswitchable ligands to control neuromodulatory receptors. However, a major shortcoming of tethered photopharmacology is the inability to obtain optical control with an efficacy comparable with that of the native ligand. To overcome this, we developed a family of branched photoswitchable compounds to target metabotropic glutamate receptors (mGluRs). These compounds permit photo-agonism of Gi/o-coupled group II mGluRs with near-complete efficiency relative to glutamate when attached to receptors via a range of orthogonal, multiplexable modalities. Through a chimeric approach, branched ligands also allow efficient optical control of Gq-coupled mGluR5, which we use to probe the spatiotemporal properties of receptor-induced calcium oscillations. In addition, we report branched, photoswitch-fluorophore compounds for simultaneous receptor imaging and manipulation. Finally, we demonstrate this approach in vivo in mice, where photoactivation of SNAP-mGluR2 in the medial prefrontal cortex reversibly modulates working memory in normal and disease-associated states. •Branched photoswitchable tethered ligands enable near-complete optical GPCR agonism•Efficient optical control of mGluR2, mGluR3, and mGluR5 across labeling and spectral modalities•mGluR5 activation in astrocytic processes leads to local calcium oscillations•mGluR2 activation in prefrontal cortex rapidly and reversibly modulates working memory Acosta-Ruiz et al. introduce branched tethered photoswitchable ligands that allow highly efficient optical control of G protein-coupled receptors with genetic targeting and high spatiotemporal resolution. These tools allow dissection of mGluR5-induced calcium oscillations and mGluR2-mediated modulation of working memory.