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Insulin-responsive aminopeptidase trafficking in 3T3-L1 adipocytes
1Howard Hughes Medical Institute, Philadelphia, Pennsylvania 19104, USA.
The Journal of Biological Chemistry
|January 25, 2000
Summary
Insulin-responsive aminopeptidase (IRAP) rapidly moves to the cell surface and recycles back, similar to GLUT4. This trafficking is essential for insulin signaling in adipocytes.
Area of Science:
- Cell biology
- Molecular trafficking
- Insulin signaling
Background:
- Insulin-responsive aminopeptidase (IRAP) is found in GLUT4 vesicles and translocates with insulin.
- Understanding IRAP's dynamic membrane trafficking is crucial for its role in insulin action.
Purpose of the Study:
- To characterize the exocytosis, endocytosis, and recycling kinetics of IRAP in 3T3-L1 adipocytes.
- To compare IRAP trafficking dynamics with that of GLUT4.
Main Methods:
- Cell fractionation
- Surface biotinylation assays
- Plasma membrane sheet assays
- Subcellular fractionation
Main Results:
- Insulin induced IRAP translocation to the plasma membrane, with exocytosis rates mirroring GLUT4.
- IRAP underwent endocytosis with a half-time of 3-5 min, inhibited by cytosol acidification, suggesting clathrin involvement.
- IRAP recycling to the plasma membrane was wortmannin-sensitive, occurring rapidly.
Conclusions:
- IRAP exhibits rapid, insulin-dependent endocytosis and recycling.
- IRAP trafficking kinetics closely match those of GLUT4, highlighting coordinated roles in insulin response.