ASSESSMENT OF THE W293A MUTATION IN THE µ-OPIOID RECEPTOR USING MOLECULAR DYNAMICS SIMULATIONS

The µ-opioid receptor (µOR), a member of the G protein-coupled receptor (GPCR) family, plays a key role in pain modulation and opioid pharmacology. This receptor is the main target of morphine, a drug widely used for the treatment of pain. GPCRs are membrane receptors comprised by 7 transmembrane helices, linked by intra- and extracellular loops. Upon activation, remarkable structural rearrangements take place, allowing classification of the receptor as inactive or active based on protein conformation features. Residue W293^6.48, located in transmembrane helix 6 (TM6), is highly conserved among class A GPCRs and is thought to participate in water flux regulation and signal transduction via the conserved CWxP motif. This ongoing project investigates the structural and dynamic implications of the W293A point mutation on µOR structural features through molecular dynamics (MD) simulations. The study focuses on modeling, validating, and comparing the wild-type and W293A mutant structures of µOR embedded in a 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer surrounded by 0.15M NaCl solution. Initial structural modeling was performed using crystallographic data, followed by in silico mutagenesis. The systems were prepared and modified using UCSF Chimera, and MD simulations were carried out using GROMACS. Resulting trajectories will be analyzed using root mean square deviation (RMSD), principal component analysis, clustering with k-means, and assessment of selected residue pair distances. Particular attention will be given to internal water flux and the disruption of intramolecular interactions induced by the W293A mutation. Expected results include observable conformational alterations in TM6, alteration of water flow through the transmembrane channel, and insights into the molecular mechanisms underlying receptor constitutive activity. By comparing results of the W293A mutant dynamics with similar simulations with the wild type receptor, this work aims to deepen our understanding of opioid receptor activation and support the development of novel therapeutic strategies targeting GPCRs.

This work is supported by Centro Nacional de Processamento de Alto Desempenho em São Paulo (CENAPAD/SP) (proj643).