Cholesterol differentially modulates the activity of opioid and muscarinic receptors via common binding site

Abstract

G protein-coupled receptors (GPCRs) are membrane proteins that represent the largest and most therapeutically targeted receptor class, accounting for 30% of currently marketed drugs. Two binding motifs for membrane cholesterol, the cholesterol recognition amino acid consensus (CRAC) domain and the cholesterol consensus motif (CCM), have been postulated. Using a simulation of the molecular dynamics of cholesterol association with the receptor, we predicted the binding of membrane cholesterol to non-canonical sites, distinct from CRAC and CCM, at muscarinic and opioid receptors. We identified a binding site common to muscarinic and opioid receptors at TM6, with arginine 6.35 as the major residue. Membrane cholesterol depletion mimics the effects of R6.35 mutations, confirming its role in receptor modulation. Targeting cholesterol-binding sites offers novel pharmacotherapeutic strategies, including tissue-specific sterol-based modulation. One sentence summaryThis study identifies a shared non-canonical cholesterol-binding site at TM6 in muscarinic and opioid receptors, with significant implications for drug development targeting tissue-specific GPCR modulation.