SH-SY5Y_CB1R-antagonist_Proteomics

Cannabinoid receptor type 1 (CB1R) is one of the most abundant GPCRs in the brain, playing a critical role in neuronal viability. While CB1R activation is typically associated with neuroprotective effects, excessive or prolonged activation can be adverse. CB1R antagonists, therefore, have shown neuroprotective effects against neurotoxicity by CB1R overactivation. Unexpectedly, we found that CB1R antagonists rimonabant and AM251 induce cell death in human neuroblastoma SH-SY5Y cells under serum-free conditions, but not in serum-containing conditions. Phosphoproteomic analysis was performed to elucidate this molecular pathway. Phospho-EIF2AK3 (also known as PERK) was up-regulated in both rimonabant and AM251 treatments. PERK is a transducer of ER stress. Using western blotting it was also confirmed that the downstream effectors of PERK, eIF2α/ATF4/CHOP, were up-regulated, suggesting activation of the ER stress signal pathway PERK/eIF2α/ATF4/CHOP. In summary, cell death by CB1 antagonists under serum-free conditions results from ER stress response.