Down-Modulation of Mature Major Histocompatibility Complex Class II and Up-Regulation of Invariant Chain Cell Surface Expression Are Well-Conserved Functions of Human and Simian Immunodeficiency Virus
            <i>nef</i>
            Alleles

Schindler, Michael; Würfl, Stephanie; Benaroch, Philippe; Greenough, Thomas C.; Daniels, Rod S.; Easterbrook, Philippa; Brenner, Matthias; Münch, Jan; Kirchhoff, Frank

doi:10.1128/jvi.77.19.10548-10556.2003

Cited by 152 publications

(227 citation statements)

References 67 publications

(100 reference statements)

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“…siRNA knockdowns were started on day 1 and repeated on day 3. Transient transfections were carried out on day 4, by using an IRES plasmid encoding Nef and GFP as a bicistronic message so that we could identify the Nef-expressing cells (Schindler et al, 2003). As a control, we used the same plasmid in which a premature stop codon had been inserted into the Nef sequence at position 2 (Nef STOP ).…”

Section: Assay For Mhc Class I Down-regulationmentioning

confidence: 99%

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HIV-1 Nef-induced Down-Regulation of MHC Class I Requires AP-1 and Clathrin but Not PACS-1 and Is Impeded by AP-2

Lubben

Sahlender

Motley

et al. 2007

MBoC

Self Cite

106

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Major histocompatibility complex class I is down-regulated from the surface of human immunodeficiency virus (HIV)-1-infected cells by Nef, a virally encoded protein that is thought to reroute MHC-I to the trans-Golgi network (TGN) in a phosphofurin acidic cluster sorting protein (PACS) 1, adaptor protein (AP)-1, and clathrin-dependent manner. More recently, an alternative model has been proposed, in which Nef uses AP-1 to direct MHC-I to endosomes and lysosomes. Here, we show that knocking down either AP-1 or clathrin with small interfering RNA inhibits the down-regulation of HLA-A2 (an MHC-I isotype) by Nef in HeLa cells. However, knocking down PACS-1 has no effect, not only on Nef-induced down-regulation of HLA-A2 but also on the localization of other proteins containing acidic cluster motifs. Surprisingly, knocking down AP-2 actually enhances Nef activity. Immuno-electron microscopy labeling of Nef-expressing cells indicates that HLA-A2 is rerouted not to the TGN, but to endosomes. In AP-2-depleted cells, more of the HLA-A2 localizes to the inner vesicles of multivesicular bodies. We propose that depleting AP-2 potentiates Nef activity by altering the membrane composition and dynamics of endosomes and causing increased delivery of HLA-A2 to a prelysosomal compartment. INTRODUCTIONLike many viruses, human immunodeficiency virus (HIV)-1 has evolved strategies to avoid detection and destruction by the host. One such strategy is the down-regulation of major histocompatability complex (MHC) class I from the plasma membrane of HIV-1-infected cells, which prevents the cells from being attacked by cytotoxic T lymphocytes. MHC-I down-regulation has been shown to be a function of a virally encoded protein called Nef (Schwartz et al., 1996;Collins et al., 1998). Nef is one of the so-called "accessory proteins" of both human and simian immunodeficiency viruses: although not required for viral replication in vitro, Nef plays a key role in the development of acquired immunodeficiency syndrome. Nef is a small protein, only ϳ200 amino acids, but it has been reported to interact with a large number of host cell proteins, including several proteins that are involved in membrane traffic. These interactions are thought to be responsible for the ability of Nef to modulate the surface expression of MHC-I and other molecules (for review, see Collins and Baltimore, 1999;Piguet et al., 1999;Doms and Trono, 2000;Roeth and Collins, 2006).Among the binding partners that have been identified for Nef are the adaptor protein (AP) complexes. There are four AP complexes in mammalian cells, two of which, AP-1 and AP-2, are highly enriched in clathrin-coated vesicles (CCVs). AP-1 facilitates clathrin-mediated trafficking between the trans-Golgi network (TGN) and endosomes (although there is still some question about directionality), and AP-2 facilitates clathrin-mediated endocytosis (Robinson, 2004). AP-3, which seems to be able to act both in a clathrin-dependent and in a clathrin-independent manner (Dell'Angelica et al., 1998;Peden et al., 2...

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Section: Assay For Mhc Class I Down-regulationmentioning

confidence: 99%

“…The control (Nef STOP ) and wild-type (Nef WT ) plasmids have already been described (as pCG.NL43Nef*pIRESgfp and pCG.NL43NefϩpIRESgfp, respectively; Schindler et al, 2003). The two mutant plasmids (Nef LL164-165AA and Nef EEEE62-65AAAA ) were constructed using a QuikChange mutagenesis kit (Stratagene).…”

Section: Plasmidsmentioning

confidence: 99%

HIV-1 Nef-induced Down-Regulation of MHC Class I Requires AP-1 and Clathrin but Not PACS-1 and Is Impeded by AP-2

Lubben

Sahlender

Motley

et al. 2007

MBoC

Self Cite

106

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“…The delivery of immature MHCII to the endolysosomal compartment is also impaired, resulting in reduced Ii degradation (17). Mutational analysis suggests that these mechanisms are well conserved among nef alleles (18).…”

mentioning

confidence: 99%

HIV-1 Nef Promotes Endocytosis of Cell Surface MHC Class II Molecules via a Constitutive Pathway

Chaudhry

Verghese²,

Das³

et al. 2009

The Journal of Immunology

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HIV-1 Nef has been reported to disrupt MHC class II (MHCII)-mediated Ag presentation by a dual strategy that comprises a reduction in cell surface levels of peptide-loaded mature MHCII molecules and a up-regulation of immature MHCII molecules. We show that Nef achieves relocation of MHCII away from the cell surface in monocytic cells by both delaying its transport to the cell surface and by accelerating endocytic removal of cell surface MHCII to a lysosomal compartment. Nef-induced MHCII endocytosis is cholesterol-sensitive but clathrin- and dynamin-independent. Internalized MHCII molecules traverse the early endosomal system and colocalize with pinocytic cargo before reaching lysosomes. Nef-triggered MHCII endocytosis requires Rab5 activity and lyst function, whereas lysosomal trafficking of internalized MHCII molecules requires Rab7 activity. We further show that a similar pathway can remove peptide-MHCII complexes from the surface of monocytic cells not expressing Nef. Our data suggest that Nef uses mechanisms involved in normal MHCII recycling and turnover to mediate the delivery of cell surface MHCII to a lysosomal destination. Thus, Nef-mediated endocytosis of MHCII provides a novel perspective on the regulation of normal MHCII trafficking.

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“…Although elegant, this model encounters some conflicting data, showing that a small amount of Nef is able to induce strong accumulation of Ii. Also, other receptors that depend on AP-2 for its endocytosis, such as the Transferrin receptor, are not upregulated by Nef (Schindler et al, 2003). Nevertheless, this could be another mechanism used for Ii upregulation and still cannot be discarded.…”

Section: Downmodulation Of Mhc-iimentioning

confidence: 99%

“…Contrary to what is seen in MHCI downmodulation, Nef activity on MHC-II and Ii do not change significantly during the stages of infection. Of note, the strong Ii upregulation observed in the presence of wild type Nef is lost in some nef alleles derived from Long-term infected HIV-1 patients which do not progress to AIDS, suggesting that this feature of Nef may contribute to immune evasion (Schindler et al, 2003). Although Nef has been described to directly bind to the citoplasmatic tail of many receptors that it modulates (Chaudhry et al, 2005), there is still no evidence that it can bind MHC-II, suggesting that Nef might interact with proteins involved in the physiological turnover pathways of this surface marker, disrupting the natural balance of MHC-II surface expression.…”

Section: Downmodulation Of Mhc-iimentioning

confidence: 99%

Functions of the Lentiviral Accessory Protein Nef During the Distinct Steps of HIV and SIV Replication Cycle

Costa¹,

Mendonça²,

Sampaio³

2011

HIV and AIDS - Updates on Biology, Immunology, Epidemiology and Treatment Strategies

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Down-Modulation of Mature Major Histocompatibility Complex Class II and Up-Regulation of Invariant Chain Cell Surface Expression Are Well-Conserved Functions of Human and Simian Immunodeficiency Virus nef Alleles

Cited by 152 publications

References 67 publications

HIV-1 Nef-induced Down-Regulation of MHC Class I Requires AP-1 and Clathrin but Not PACS-1 and Is Impeded by AP-2

HIV-1 Nef-induced Down-Regulation of MHC Class I Requires AP-1 and Clathrin but Not PACS-1 and Is Impeded by AP-2

HIV-1 Nef Promotes Endocytosis of Cell Surface MHC Class II Molecules via a Constitutive Pathway

Functions of the Lentiviral Accessory Protein Nef During the Distinct Steps of HIV and SIV Replication Cycle

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