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Updated: Jul 10, 2026

Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications
09:39

Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications

Published on: January 27, 2014

Mu opioid receptor mutant, T394A, abolishes opioid-mediated adenylyl cyclase superactivation

Hongyan Wang1, Wei Guang, Elisabeth Barbier

  • 1Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA.

Neuroreport
|November 17, 2007
PubMed

Insights

A mutation in the mu opioid receptor (MOR) C-terminus, specifically T394A, blocks chronic opioid-induced cellular responses like adenylyl cyclase superactivation and receptor phosphorylation.

Area of Science:

  • Pharmacology
  • Molecular Biology
  • Cellular Neuroscience

Background:

  • Chronic opioid use leads to cellular adaptive responses.
  • Adenylyl cyclase (AC) superactivation is a key indicator of these responses.
  • The C-terminal region of the mu opioid receptor (MOR) is implicated in these adaptations.

Purpose of the Study:

  • To investigate the role of the C-terminal amino acid T394 in MOR.
  • To characterize the impact of the MOR T394A mutation on chronic opioid-induced cellular signaling.
  • To elucidate the mechanisms underlying MOR-mediated cellular adaptation.

Main Methods:

  • Utilized cell lines expressing wild-type MOR and a C-terminal point-mutant (MOR T394A).
  • Chronic exposure to the opioid agonist DAMGO ([D-Ala, N-Me-Phe, Gly-ol] enkephalin) for 18 hours.
  • Assessed adenylyl cyclase (AC) activity and receptor phosphorylation.
  • Investigated the effect of MAP kinase kinase-1 (MKK1) overexpression.

Main Results:

  • Wild-type MOR-expressing cells exhibited AC superactivation after chronic DAMGO exposure.
  • AC superactivation was abolished in cells expressing the MOR T394A mutant.
  • Receptor phosphorylation was reduced in MOR T394A cells following prolonged agonist exposure.
  • MKK1 overexpression rescued AC superactivation in MOR T394A cells but not in wild-type cells.

Conclusions:

  • The amino acid T394 at the MOR C-terminus is critical for chronic agonist-induced AC superactivation.
  • T394 plays a significant role in regulating MOR phosphorylation during chronic opioid stimulation.
  • These findings highlight T394 as a key determinant of cellular adaptive responses to chronic opioid treatment.

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