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Characterization of rapid membrane internalization and recycling
1Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.
The Journal of Biological Chemistry
|May 16, 2000
Summary
Cell membrane lipids rapidly recycle to the plasma membrane via sorting endosomes. This rapid membrane trafficking suggests faster internalization rates than previously thought, impacting cellular processes.
Area of Science:
- Cell Biology
- Membrane Trafficking
- Lipid Biology
Background:
- Membrane constituents continuously recycle between the plasma membrane and intracellular compartments.
- The fluorescent lipid analogue C(6)-NBD-SM is a common marker for studying membrane dynamics.
Purpose of the Study:
- To investigate the kinetics of C(6)-NBD-SM recycling in mammalian cells.
- To identify the endocytic compartments involved in rapid lipid recycling.
Main Methods:
- Kinetic analysis of C(6)-NBD-SM internalization and recycling in CHO, HEp2, and Madin-Darby canine kidney cells.
- Utilized FM dyes of varying hydrophobicity to track membrane passage.
- Co-localization studies with transferrin and low-density lipoprotein to identify endocytic organelles.
Main Results:
- A significant portion (42-62%) of internalized C(6)-NBD-SM rapidly recycles to the plasma membrane with a half-time (t(1/2)) of 1-2 minutes.
- This rapid recycling pathway involves passage through sorting endosomes.
- Implies a much higher membrane internalization rate (t(1/2) of 5-10 minutes) than previously estimated.
Conclusions:
- Mammalian cells exhibit rapid lipid recycling from the plasma membrane via sorting endosomes.
- The high rate of membrane internalization and recycling is crucial for cellular functions like nutrient uptake and cholesterol transport.