HIV-1 Nef protein binds to the cellular protein PACS-1 to downregulate class I major histocompatibility complexes.
Major-histocompatibility-complex (MHC) proteins are used to display, on the surface of a cell, peptides derived from foreign material - such as a virus - that is infecting that cell. Cytotoxic T lymphocytes then recognize and kill the infected cell. The HIV-1 Nef protein downregulates the cell-surface expression of class I MHC proteins, and probably thereby promotes immune evasion by HIV-1. In the presence of Nef, class I MHC molecules are relocalized from the cell surface to the trans-Golgi network (TGN) through as-yet-unknown mechanisms. Here we show that Nef- induced downregulation of MHC-I expression and MHC-I targeting to the TGN require the binding of Nef to PACS-1, a molecule that controls the TGN localization of the cellular protein furin. This interaction is dependent on Nef's cluster of acidic amino acids. A chimaeric integral membrane protein containing Nef as its cytoplasmic domain localizes to the TGN after internalization, in an acidic-cluster- and PACS-1-dependent manner. These results support a model in which Nef relocalizes MHC-I by acting as a connector between MHC-I's cytoplasmic tail and the PACS-1-dependent protein-sorting pathway.[1]References
- HIV-1 Nef protein binds to the cellular protein PACS-1 to downregulate class I major histocompatibility complexes. Piguet, V., Wan, L., Borel, C., Mangasarian, A., Demaurex, N., Thomas, G., Trono, D. Nat. Cell Biol. (2000) [Pubmed]
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