Addiction associated N40D mu-opioid receptor variant modulates synaptic function in human neurons

Area of Science:

• Neuroscience
• Genetics
• Pharmacology

Background:

• The OPRM1 A118G gene variant (rs1799971) encodes the N40D µ-opioid receptor (MOR).
• This variant is linked to opioid and drug abuse dependence, but the underlying mechanisms remain unclear.
• Opioid abuse is a significant public health crisis, necessitating a deeper understanding of genetic predispositions.

Purpose of the Study:

• To investigate the neurophysiological and molecular impact of the N40D MOR variant.
• To elucidate the mechanisms by which this genetic variation influences synaptic transmission and opioid responsivity.

Main Methods:

• Generated homozygous N40D subject-specific induced inhibitory neuronal cells (iNs) from human induced pluripotent stem cells (iPSCs).
• Examined the regulation of MOR on synaptic transmission, including spontaneous inhibitory postsynaptic currents (sIPSCs).
• Utilized isogenic iNs and biochemical analysis to assess differential N-linked glycosylation of MOR variants.

Main Results:

• N40D iNs demonstrated significantly stronger suppression of sIPSCs compared to N40 MOR.
• Differential N-linked glycosylation of the N40D MOR variant was observed.
• Isogenic models confirmed the regulatory effects of MOR on synaptic transmission, mitigating genetic background noise.

Conclusions:

• The N40D MOR variant exhibits distinct neurophysiological and molecular properties compared to the wild-type N40 MOR.
• These differences may underlie altered opioid responsivity and increased susceptibility to dependence in individuals carrying the A118G variant.
• Findings provide insights into potential therapeutic targets for managing opioid use disorder.