Cannabinoid tolerance relies on CB₁ receptor ubiquitination by NEDD4L

Cannabinoids, the active components of cannabis, exert numerous acute effects in the brain by engaging cannabinoid CB₁ receptors (CB₁Rs). However, tolerance emerges rapidly after repeated drug exposure, undermining the efficacy of cannabinoid-based therapies and contributing to cannabis-associated adverse effects. Although the processes of CB₁R short-term desensitization (i.e., receptor uncoupling and internalization) are well characterized, the mechanisms underlying CB₁R long-term tolerance (i.e., downregulation of receptor protein levels) remain elusive. Here, we identify a ubiquitin-dependent pathway that couples CB₁R activation to its proteasomal degradation. We show that cannabinoids engage a G_q/11-PLC-PKC signaling cascade that phosphorylates and activates the E3 ubiquitin ligase neural precursor cell-expressed developmentally downregulated 4-like (NEDD4L), promoting its recruitment to CB₁R and the ubiquitination of four specific lysine residues. This modification targets the receptor for proteasomal clearance, reducing neuronal CB₁R abundance in vitro and in the mouse brain. Using molecular, pharmacological, and circuit-specific rescue approaches, we demonstrate that preventing CB₁R ubiquitination stabilizes receptor levels and abolishes behavioral cannabinoid tolerance in mice without impairing acute drug responses. These findings reveal a molecular mechanism that controls CB₁R stability and identify NEDD4L-mediated ubiquitination as a central driver of cannabinoid tolerance.