Regulation of MHC Class I Assembly and Peptide Binding

Peaper, David R.; Cresswell, Peter

doi:10.1146/annurev.cellbio.24.110707.175347

Cited by 178 publications

(158 citation statements)

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“…Tapbp encodes the transmembrane glycoprotein tapasin, which is involved in endoplasmic reticulum (ER) quality control of major histocompatibility complex (MHC) class I antigen presentation [33,34]. The data in Figures 3C and 4B showed that Smad2 binds to the Tapbp promoter and Activin can upregulate Tapbp expression.…”

Section: Tapbp a Downstream Target Of Activin/nodal-smad2 Signalingmentioning

confidence: 99%

Smad2 mediates Activin/Nodal signaling in mesendoderm differentiation of mouse embryonic stem cells

et al. 2010

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Although Activin/Nodal signaling regulates pluripotency of human embryonic stem (ES) cells, how this signaling acts in mouse ES cells remains largely unclear. To investigate this, we confirmed that mouse ES cells possess active Smad2-mediated Activin/Nodal signaling and found that Smad2-mediated Activin/Nodal signaling is dispensable for self-renewal maintenance but is required for proper differentiation toward the mesendoderm lineage. To gain insights into the underlying mechanisms, Smad2-associated genes were identified by genome-wide chromatin immunoprecipitation-chip analysis. The results showed that there is a transcriptional correlation between Smad2 binding and Activin/Nodal signaling modulation, and that the development-related genes were enriched among the Smad2-bound targets. We further identified Tapbp as a key player in mesendoderm differentiation of mouse ES cells acting downstream of the Activin/Nodal-Smad2 pathway. Taken together, our findings suggest that Smad2-mediated Activin/Nodal signaling orchestrates mesendoderm lineage commitment of mouse ES cells through direct modulation of corresponding developmental regulator expression.

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Section: Tapbp a Downstream Target Of Activin/nodal-smad2 Signalingmentioning

confidence: 99%

Smad2 mediates Activin/Nodal signaling in mesendoderm differentiation of mouse embryonic stem cells

et al. 2010

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“…Subsequently, peptides are trimmed and loaded into the grooves of MHC-I molecules, a dynamic process that is mediated by the peptide loading complex (PLC) consisting of MHC-I, b2m, ERp57, TAP, tapasin and chaperones [11][12][13]. The TAP peptide transport is operated by the heterodimer pump TAP1/TAP2, members of the ABC transporter family.…”

Section: Introductionmentioning

confidence: 99%

Peptide transporter TAP mediates between competing antigen sources generating distinct surface MHC class I peptide repertoires

et al. 2011

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We recently described a category of TAP-independent peptide-epitopes that are selectively presented by cells with processing defects in the classical MHC class I (MHC-I) pathway. Here, we studied the ER-resident ceramide synthase Trh4 as a prototypic example of these neo-antigens and found that moderate inhibition of TAP permits cell surface presentation of the Trh4 peptide. The absence of this peptide from WT cells was not related to the binding or stability of the Trh4/D b complexes, or to the availability of MHC-I heavy chains, but rather to the limited expression of the antigen. Strongly elevated antigen levels were needed to reach comparable peptide display on WT as on TAP-deficient cells. Our data suggest that the normal influx of TAP-transported peptides in the ER during routine processing creates an efficient barrier for peptides from alternative processing routes. Impairment of TAP function, as commonly found in cancers and virus-infected cells, lowers this resistance allowing for MHC-I presentation of other peptide sources.Key words: Antigen processing . Cytotoxic T lymphocytes . Transporter associated with peptide processing Supporting Information available online IntroductionCytotoxic T lymphocytes (CTLs) are key effector cells of the adaptive immune system and circulate throughout the body in search of their cognate peptides that are presented by MHC class I (MHC-I) molecules. T-cell receptors determine the antigen specificity of CTLs and engagement with peptide/MHC-I complexes leads to their activation and elimination of target cells. Therefore, the process of MHC-I antigen processing and presentation, which operates in all nucleated cells of our body, is crucial for CTL immune surveillance [1][2][3]. The highly complex repertoire of MHC-I presented peptides reflects the total proteome of cells and derives from the physiological turnover of proteins, a process that is largely operated by the multicatalytic enzyme proteasome [4,5]. In addition to the proteasome, other proteolytic enzymes in the cytosol have been implicated in the liberation of peptides for MHC-I presentation, some of which can compensate for the lack of proteasome activity [1,6,7]. For instance, tripeptidyl peptidase II (TPPII), insulin-degrading enzyme (IDE), thimet oligopeptidase (TOP) and nardilysin have been implicated in the generation of some CTL epitopes [8][9][10]. However, the relative contributions of these novel peptidases and Ã These authors contributed equally to this work 3114their cooperation with the proteasome have not been fully characterized.The intermediate peptide products are rescued from total breakdown by these cytosolic proteases through translocation into the ER. Subsequently, peptides are trimmed and loaded into the grooves of MHC-I molecules, a dynamic process that is mediated by the peptide loading complex (PLC) consisting of MHC-I, b2m, ERp57, TAP, tapasin and chaperones [11][12][13]. The TAP peptide transport is operated by the heterodimer pump TAP1/TAP2, members of the ABC transporter family. The imp...

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“…CD8 + T cells, which rapidly expand during immune responses and mediate cytotoxicity against infected and tumor cells, recognize octamer or nonamer peptides on MHC class I molecules 1 . These peptides are thought to originate primarily from protein degradation by proteasomes, large multicatalytic proteases in cytosol and nucleus 2 . These peptides are then imported into the endoplasmic reticulum (ER) via the transporter associated with antigen processing (TAP), and can be further trimmed on their N-terminus via ER aminopeptidases associated with antigen processing (ERAAPs) 3 .…”

Section: T Cells Detect Infected or Transformed Cells Via Antigen Prementioning

confidence: 99%

MHC presentation via autophagy and how viruses escape from it

Gannagé

Münz

2010

Semin Immunopathol

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T cells detect infected and transformed cells via antigen presentation by major histocompatibility complex (MHC) molecules on the cell surface. For T cell stimulation, these MHC molecules present fragments of proteins that are expressed or taken up by the cell. These fragments are generated by distinct proteolytic mechanisms for presentation on MHC class I molecules to cytotoxic CD8(+) and on MHC class II molecules to helper CD4(+) T cells. Proteasomes are primarily involved in MHC class I ligand and lysosomes, in MHC class II ligand generation. Autophagy delivers cytoplasmic material to lysosomes and, therefore, contributes to cytoplasmic antigen presentation by MHC class II molecules. In addition, it has been recently realized that this process also supports extracellular antigen processing for MHC class II presentation and cross-presentation on MHC class I molecules. Although the exact mechanisms for the regulation of these antigen processing pathways by autophagy are still unknown, recent studies, summarized in this review, suggest that they contribute to immune responses against infections and to maintain tolerance. Moreover, they are targeted by viruses for immune escape and could maybe be harnessed for immunotherapy. These fragments are generated by distinct proteolytic mechanisms for presentation on MHC class I molecules to cytotoxic CD8 + and on MHC class II molecules to helper CD4 + T cells.Proteasomes are primarily involved in MHC class I ligand, and lysosomes in MHC class II ligand generation. Autophagy delivers cytoplasmic material to lysosomes, and, therefore, contributes to cytoplasmic antigen presentation by MHC class II molecules. In addition, it has been recently realized that this process also supports extracellular antigen processing for MHC class II presentation and cross-presentation on MHC class I molecules. Although the exact mechanisms for the regulation of these antigen processing pathways by autophagy are still unknown, recent studies, summarized in this review, suggest that they contribute to immune responses against infections and to maintain tolerance. Moreover, they are targeted by viruses for immune escape, and could maybe be harnessed for immunotherapy. Gannage and Münz 3

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Regulation of MHC Class I Assembly and Peptide Binding

Cited by 178 publications

References 157 publications

Smad2 mediates Activin/Nodal signaling in mesendoderm differentiation of mouse embryonic stem cells

Smad2 mediates Activin/Nodal signaling in mesendoderm differentiation of mouse embryonic stem cells

Peptide transporter TAP mediates between competing antigen sources generating distinct surface MHC class I peptide repertoires

MHC presentation via autophagy and how viruses escape from it

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