[HTML][HTML] HIV-1 Nef sequesters MHC-I intracellularly by targeting early stages of endocytosis and recycling

BS Dirk, EN Pawlak, AL Johnson, LR Van Nynatten… - Scientific reports, 2016 - nature.com
Scientific reports, 2016nature.com
A defining characteristic of HIV-1 infection is the ability of the virus to persist within the host.
Specifically, MHC-I downregulation by the HIV-1 accessory protein Nef is of critical
importance in preventing infected cells from cytotoxic T-cell mediated killing. Nef
downregulates MHC-I by modulating the host membrane trafficking machinery, resulting in
the endocytosis and eventual sequestration of MHC-I within the cell. In the current report, we
utilized the intracellular protein-protein interaction reporter system, bimolecular fluorescence …
Abstract
A defining characteristic of HIV-1 infection is the ability of the virus to persist within the host. Specifically, MHC-I downregulation by the HIV-1 accessory protein Nef is of critical importance in preventing infected cells from cytotoxic T-cell mediated killing. Nef downregulates MHC-I by modulating the host membrane trafficking machinery, resulting in the endocytosis and eventual sequestration of MHC-I within the cell. In the current report, we utilized the intracellular protein-protein interaction reporter system, bimolecular fluorescence complementation (BiFC), in combination with super-resolution microscopy, to track the Nef/MHC-I interaction and determine its subcellular localization in cells. We demonstrate that this interaction occurs upon Nef binding the MHC-I cytoplasmic tail early during endocytosis in a Rab5-positive endosome. Disruption of early endosome regulation inhibited Nef-dependent MHC-I downregulation, demonstrating that Nef hijacks the early endosome to sequester MHC-I within the cell. Furthermore, super-resolution imaging identified that the Nef:MHC-I BiFC complex transits through both early and late endosomes before ultimately residing at the trans-Golgi network. Together we demonstrate the importance of the early stages of the endocytic network in the removal of MHC-I from the cell surface and its re-localization within the cell, which allows HIV-1 to optimally evade host immune responses.
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