The N40D Variant Presents Distinct Trafficking and Signaling Properties to the Mu‐Opioid Receptor

Abstract

The opioid overdose crisis has continued to increase over the past few years resulting in about 1.7 million people battling substance use disorder related to prescription opioid pain relievers. Individual susceptibility to opioid overdose and addiction is largely determined by genetic variation. One gene that shows genetic variation is OPRM1, the gene for the mu-opioid receptor (MOR), the primary target of all clinically used and abused opioids. OPRM1 is susceptible to several naturally occurring single nucleotide polymorphisms (SNPs), such as A118G (or N40D). N40D is the most prevalent SNP and causes an Asn to Asp switch leading to the removal of an N-glycosylation site. N40D is associated with various disorders including substance use disorder and alcoholism. However, how N40D and other SNPs change MOR function at molecular and cellular levels are still unknown. To address this gap, we examined the effect of the N40D mutation on two key aspects of receptor function: trafficking and signaling. Our results suggest that N40D variant receptor shows steady state localization and trafficking that is distinct from the MOR, leading to differences in downstream consequences of receptor signaling from the same agonist. These results have profound implications to understanding the pharmacogenetics of opioid physiology and developing personalized care in the future.