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Visualizing Clathrin-mediated Endocytosis of G Protein-coupled Receptors at Single-event Resolution via TIRF Microscopy
Published on: October 20, 2014
Phosducin, beta-arrestin and opioid receptor migration
R Schulz1, A Wehmeyer, J Murphy
1Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Germany. schulz@pharmtox.vetmed.uni-muenchen.de
European Journal of Pharmacology
|August 12, 1999
Summary
Phosducin blocks opioid receptor internalization, but beta-arrestin 1 overrides this effect. Arrestin, not phosphorylation, is key for morphine-induced mu-opioid receptor endocytosis.
Area of Science:
- Pharmacology
- Cell Biology
- Neuroscience
Background:
- G protein-coupled opioid receptor internalization is complex, influenced by drug affinity and receptor-G protein interactions.
- Cytosolic proteins phosducin and arrestin play opposing roles in receptor internalization.
- Phosducin inhibits receptor phosphorylation, while arrestin promotes endocytosis by uncoupling receptors from G proteins.
Purpose of the Study:
- To investigate the interplay between phosducin and arrestin in regulating mu-opioid receptor endocytosis.
- To elucidate the mechanisms underlying opioid receptor internalization in neuronal cells.
Main Methods:
- Utilized neuronal NG 108-15 hybrid cells expressing a fluorescently tagged mu-opioid receptor.
- Employed confocal laser scanning microscopy to visualize and quantify receptor internalization in living cells.
- Manipulated cellular expression of phosducin and beta-arrestin 1 to assess their effects on receptor trafficking.
Main Results:
- Mu-opioid receptors were observed at the cell membrane and surface protrusions in drug-naive cells.
- Etorphine induced receptor internalization, a process blocked by phosducin overexpression but restored by co-expressing beta-arrestin 1.
- Morphine did not induce internalization in naive cells but did so when arrestin was overexpressed, an effect not modulated by phosducin.
Conclusions:
- Arrestin-mediated uncoupling of the mu-opioid receptor from its G protein complex is the primary driver of endocytosis.
- Drug-induced receptor phosphorylation plays a secondary role in the internalization process.
- These findings highlight the critical role of arrestin in regulating opioid receptor signaling and trafficking.
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