Related Experiment Videos
ARF1 regulates Nef-induced CD4 degradation.
Julien Fauré1, Romaine Stalder, Christelle Borel
1Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland.
Current Biology : CB
|June 19, 2004
Summary
The small GTPase ARF1 directly interacts with HIV Nef protein, controlling the targeting of CD4 to lysosomes. This interaction is crucial for the Nef-induced pathway that downregulates CD4 expression.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- The HIV Nef protein downregulates CD4 cell surface receptors.
- This process involves clathrin-coated pits and COP1 coatomer for endocytosis and lysosomal targeting.
Purpose of the Study:
- To investigate the role of the small GTPase ARF1 in the Nef-mediated CD4 downregulation pathway.
- To elucidate the molecular mechanism by which Nef targets CD4 for lysosomal degradation.
Main Methods:
- Co-immunoprecipitation assays to detect protein complexes.
- Site-directed mutagenesis to identify critical residues in Nef.
- Expression of dominant-negative ARF1 mutants to block pathway progression.
Main Results:
- ARF1 directly binds to HIV Nef and is recruited to endosomal membranes.
- A ternary complex of Nef, ARF1, and betaCOP is formed.
- Specific Nef residues are essential for ARF1 interaction and late endosomal targeting of CD4.
- A dominant-negative ARF1 mutant inhibits CD4 migration to lysosomes.
Conclusions:
- ARF1 acts as a direct downstream effector of Nef in the CD4 lysosomal targeting pathway.
- Nef utilizes ARF1 to mediate the COP-dependent trafficking of CD4 to late endosomes and lysosomes.