Visualization of membrane localization and functional state of CB2R pools by matched agonist and inverse agonist probe pairs

The diversity of physiological roles of the endocannabinoid system has turned it into an attractive yet elusive therapeutic target. However, chemical probes with various functionalities could pave the way for a better understanding of the endocannabinoid system at the cellular level. Notably, inverse agonists of CB2R – a key receptor of the endocannabinoid system - lagged behind despite the evidence regarding the therapeutic potential of its antagonism. Herein, we report a matched fluorescent probe pair based on a common chemotype to address and visualize both the active and inactive states of CB2R, selectively. Alongside with extensive cross-validation by flow cytometry and confocal microscopy, we successfully visualize the intracellular localization of CB2R pools in live cells. The synthetic simplicity together with the high CB2R-selectivity and specificity of our probes, turn them into valuable tools in chemical biology and drug development that can benefit the clinical translatability of CB2R-based drug.