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Clathrin-mediated endocytosis in AP-2-depleted cells
Alison Motley1, Nicholas A Bright, Matthew N J Seaman
1University of Cambridge, Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Cambridge CB2 2XY, UK.
The Journal of Cell Biology
|September 4, 2003
Summary
AP-2 adaptor protein is not essential for clathrin-coated vesicle formation but is crucial for transferrin receptor uptake. Alternative adaptors may mediate endocytosis of EGF and LDL receptors.
Area of Science:
- Cell Biology
- Molecular Biology
- Endocytosis
Background:
- Clathrin-coated vesicles mediate receptor-mediated endocytosis.
- Adaptor proteins, like AP-2, are thought to be essential for cargo selection and vesicle formation.
Purpose of the Study:
- To investigate the role of the AP-2 mu2 subunit and clathrin heavy chain in clathrin-coated vesicle formation and receptor-mediated endocytosis.
- To determine if AP-2 is essential for the internalization of specific cargo proteins.
Main Methods:
- RNA interference (RNAi) was used to deplete AP-2 mu2 subunit and clathrin heavy chain in HeLaM cells.
- The abundance of clathrin-coated pits was quantified.
- Receptor-mediated endocytosis of transferrin, EGF, and an LDL receptor chimera was assessed.
Main Results:
- Depletion of AP-2 reduced clathrin-coated pits but did not abolish them.
- Clathrin depletion eliminated clathrin-coated pits and vesicles, causing Golgi swelling.
- Transferrin uptake was inhibited by both AP-2 and clathrin depletion.
- EGF and LDL receptor uptake were inhibited by clathrin depletion but not AP-2 depletion.
Conclusions:
- AP-2 is not essential for clathrin-coated vesicle formation at the plasma membrane.
- AP-2 is one of several endocytic adaptors required for specific cargo uptake, such as the transferrin receptor.
- Alternative adaptors likely facilitate the internalization of EGF and LDL receptors.