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AAK1-mediated micro2 phosphorylation is stimulated by assembled clathrin
Sean D Conner1, Thomas Schröter, Sandra L Schmid
1The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
Traffic (Copenhagen, Denmark)
|November 18, 2003
Summary
Adaptor-associated kinase 1 (AAK1) activity is regulated by clathrin, which stimulates AAK1 to phosphorylate AP2. This clathrin-mediated activation enhances receptor internalization during endocytosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Adaptor-associated kinase 1 (AAK1) phosphorylates the AP2 complex's micro2 subunit.
- AAK1 overexpression inhibits AP2-dependent receptor internalization.
- In vivo micro2 phosphorylation is not altered by AAK1 overexpression, suggesting cellular regulation.
Purpose of the Study:
- Investigate the regulation of AAK1 activity in vivo.
- Determine the role of clathrin in AAK1-mediated micro2 phosphorylation.
- Elucidate the mechanism by which clathrin influences AAK1 activity.
Main Methods:
- In vitro kinase assays using purified AAK1, AP2, and clathrin components.
- Comparison of AAK1 activity with unassembled clathrin triskelia and clathrin cages.
- Analysis of protein-protein interactions between AAK1, AP2, and clathrin.
Main Results:
- AAK1 is an atypical kinase whose activity is rate-limited by AP2 association.
- Clathrin significantly stimulates micro2 phosphorylation by AAK1.
- Clathrin cages provide greater stimulation than unassembled clathrin, indicating multiple interaction sites.
Conclusions:
- Clathrin plays a regulatory role in endocytosis beyond structural functions.
- Clathrin activates AAK1, thereby modulating AP2 complex activity.
- AAK1 is activated in coated pits to enhance cargo recruitment and receptor internalization.