Optical Control of Cannabinoid Receptor 2–Mediated Ca2+ Release Enabled By Synthesis of Photoswitchable Probes

Cannabinoid receptor 2 (CB2) is a promising target for the treatment of neuroinflammation and other diseases. Howev-er, lack of understanding of its complex signaling in cells and tissues complicates its therapeutic targeting. For the first time we show that HU308 increases cytosolic Ca2+ levels in mammalian cells via CB2 and phospholipase C. We report the synthesis of pho-toswitchable derivatives of CB2 agonist HU308, azo-HU308s, from central building block 3-OTf-HU308. Azo-HU308s enable optical control over CB2 activity with spatiotemporal precision, as demonstrated in real-time Ca2+ fluorescence imaging. Our findings reveal a novel messenger pathway by which HU308 and its derivatives can affect cellular excitability, and demonstrate the utility of chemical photoswitches to control CB2 signaling in real time.