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HIV Nef-mediated CD4 down-regulation is adaptor protein complex 2 dependent
Yong-Jiu Jin1, Catherine Yi Cai, Xiaoping Zhang
1Skirball Institute of Biomedical Research, New York University School of Medicine, New York, NY 10016, USA. jiny@saturn.med.nyu.edu
Journal of Immunology (Baltimore, Md. : 1950)
|August 24, 2005
Summary
HIV Nef protein down-regulates CD4 via AP-2 clathrin-coated pits. Inhibiting AP-2 components blocks this process, revealing a key mechanism in HIV pathogenesis and viral replication.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Nef is a vital HIV protein essential for viral replication and AIDS development.
- Nef down-regulates CD4 receptors from the cell surface, increasing viral pathogenicity.
- The precise mechanism linking Nef's C-terminal dileucine motif to clathrin-coated pit components was unclear.
Purpose of the Study:
- To elucidate the role of the AP-2 complex in Nef-mediated CD4 down-regulation.
- To investigate the dependence of HIV and SIV Nef-mediated CD4 down-regulation on AP-2.
- To determine if PMA-induced CD4 down-regulation also involves the AP-2 complex.
Main Methods:
- Utilized a dominant-negative mutant of Eps15 (Eps15DIII) that inhibits the alpha subunit of AP-2.
- Employed small interference RNA specific for the mu2 subunit of AP-2.
- Assessed the synergistic effect of these inhibitors on CD4 down-regulation mediated by HIV Nef and SIV Nef.
Main Results:
- Both HIV Nef and SIV Nef-mediated CD4 down-regulation were significantly blocked by the combined inhibition of AP-2 components.
- These findings demonstrate that Nef-mediated CD4 down-regulation is dependent on the AP-2 complex.
- PMA-induced CD4 down-regulation was also inhibited by the AP-2 specific inhibitors, indicating its AP-2 dependence.
Conclusions:
- HIV/SIV Nef-mediated CD4 down-regulation relies on the AP-2 complex.
- Dileucine motif-dependent endocytosis of Nef and CD4 is mediated by AP-2, similar to tyrosine motif-dependent endocytosis.
- This research clarifies a critical step in HIV pathogenesis involving viral protein-mediated receptor trafficking.