Chapter 10. Small-molecule Inhibitors of Endocannabinoid Transport and Trafficking

The endocannabinoid system (ECS) comprises two major endocannabinoids (eCBs), 2-arachidonoyl glycerol (2-AG) and N-arachidonoylethanolamine (AEA), which act via the cannabinoid receptors CB1 and CB2. The ECS represents a major retrograde inhibitory system at chemical synapses and further modulates immune and metabolic processes related to stress. Upon interaction with their receptors, eCBs must be removed and/or degraded to terminate signal transduction and receptor signalling. How eCBs travel between membranes and how their intracellular transport is orchestrated remains poorly understood. While eCBs readily sequestrate into the outer or inner leaflets of membrane bilayers, there is experimental evidence that they cross the entire plasma membrane by facilitated diffusion. Using small molecules to selectively inhibit eCB trafficking between apolar surfaces or discrete binding sites related to transport is key to understand these complex biochemical mechanisms. Different eCB membrane and intracellular transport mechanisms have been proposed, with varying degrees of thermodynamic and stoichiometric constraints. In this chapter, the role of chemical tools for the characterization of eCB transport is discussed, emphasizing recent developments. The serendipitous evolutionary and pharmacological convergence of eCB-like natural products interfering with eCB transport and metabolism is highlighted.