CB<SUB>1</SUB>R–OX<SUB>2</SUB>R HETEROMER IN ALZHEIMER’S DISEASE: IMPLICATIONS FOR NEURONAL NEUROPROTECTIVE SIGNALING

Alzheimer’s disease (AD) remains a major global health challenge, prompting intense research into its pathophysiology and potential therapeutic targets. Among these, G protein-coupled receptors (GPCRs) have gained attention due to their involvement in neurodegenerative processes. In particular, orexin and cannabinoid receptors—both GPCRs—have been implicated in AD progression and neuroprotection. Selective modulation of orexin 2 receptor (OX₂R) signaling has been linked to AD pathology, while cannabinoid 1 receptor (CB₁R) overexpression occurs in neuroinflammatory contexts and is associated with neuroprotective effects. Given the documented interactions between the orexin and cannabinoid systems, their interplay represents a promising therapeutic avenue. Here, we demonstrate a close functional and physical relationship between OX₂R and CB₁R in transfected cells and primary neuronal cultures. These receptors form a heteromeric complex (CB₁R–OX₂R Het) in which they allosterically modulate each other’s signaling. Notably, simultaneous activation of CB1R and OX2R reduces reactive oxygen species (ROS) production in primary cortical neurons exposed to amyloid beta, indicating enhanced neuroprotection. Heteromer formation was confirmed using BRET assays in heterologous cells and PLA assays in primary neurons. A key finding was that blockade of one receptor enhanced signaling through the other, a heteromer-specific property observed in both experimental systems. These results suggest that selective antagonism within the CB₁R–OX₂R could potentiate the endogenous neuroprotective actions of cannabinoids and orexins, highlighting a novel strategy with potential therapeutic relevance for AD.