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mu-Opioid receptor cell surface expression is regulated by its direct interaction with Ribophorin I

Xin Ge1, Horace H Loh, Ping-Yee Law

  • 1Department of Pharmacology, University of Minnesota Medical School, Minneapolis, 55455, USA. gexx0019@umn.edu

Molecular Pharmacology
|March 18, 2009
PubMed

Insights

Ribophorin I (RPNI) directly interacts with the mu-opioid receptor (MOR), a G protein-coupled receptor. This interaction regulates MOR trafficking, depending on the receptor's N-glycosylation status.

Area of Science:

  • Molecular biology
  • Cellular biology
  • Neuroscience

Background:

  • The mu-opioid receptor (MOR), a rhodopsin G protein-coupled receptor (GPCR), is crucial for pain modulation.
  • MOR trafficking is a complex process influenced by interactions with various cellular proteins.

Purpose of the Study:

  • To identify novel proteins that regulate MOR trafficking.
  • To elucidate the mechanism by which Ribophorin I (RPNI) influences MOR cell surface expression.

Main Methods:

  • Targeted proteomics and mass spectrometry to identify interacting proteins.
  • Small interfering RNA (siRNA) knockdown and overexpression studies.
  • Analysis of MOR trafficking in cells with altered RPNI levels and receptor glycosylation mutants.

Main Results:

  • RPNI was identified as a direct interacting partner of MOR.
  • siRNA-mediated knockdown of RPNI resulted in intracellular retention of MOR.
  • Overexpression of RPNI rescued surface expression of a MOR mutant, independent of calnexin.
  • RPNI's effect on MOR trafficking is dependent on the N-glycosylation status of the receptor.

Conclusions:

  • RPNI acts as a novel chaperone, regulating MOR trafficking through N-glycosylation-dependent interactions.
  • This finding reveals a new mechanism controlling GPCR trafficking and function.

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