Functional significance of tapasin membrane association and disulfide linkage to ERp57 in MHC class I presentation

Georgesen

et al. 2012

Molecular Immunology

The current model of antigen assembly with major histocompatibility complex (MHC) class I molecules posits that interactions between the tapasin N-terminal immunoglobulin (Ig)-like domain and the MHC class I peptide-binding groove permit tapasin to regulate antigen selection. Much less is known regarding interactions that might involve the tapasin C-terminal Ig-like domain. Additionally, the tapasin transmembrane/cytoplasmic region enables tapasin to bridge the MHC class I molecule to the transporter associated with antigen processing (TAP). In this investigation, we made use of two tapasin mutants to determine the relative contribution of the tapasin C-terminal Ig-like domain and the tapasin transmembrane/cytoplasmic region to the assembly of MHC class I molecules. Deletion of a loop within the tapasin C-terminal Ig-like domain (Δ334-342) prevented tapasin association with the MHC class I molecule Kd. Although tapasin Δ334-342 did not increase the efficiency of Kd folding, Kd surface expression was enhanced on cells expressing this mutant relative to tapasin-deficient cells. In contrast to tapasin Δ334-342, a soluble tapasin mutant lacking the transmembrane/cytoplasmic region retained the ability to bind to Kd molecules, but did not facilitate Kd surface expression. Furthermore, when soluble tapasin and tapasin Δ334-342 were co-expressed, soluble tapasin had a dominant negative effect on the folding and surface expression of not only Kd, but also Db and Kb. In addition, our molecular modeling of the MHC class I-tapasin interface revealed novel potential interactions involving tapasin residues 334-342. Together, these findings demonstrate that the tapasin C-terminal and transmembrane/cytoplasmic regions are critical to tapasin's capacity to associate effectively with the MHC class I molecule.

Section: Resultssupporting

confidence: 91%

“…Notably, soluble tapasin was highly stable (Fig. 2B), consistent with a previous finding that soluble tapasin mutants were expressed at higher levels than full-length forms of tapasin (Vigneron et al, 2009). As suggested by Vigneron et al (2009), positively charged residues within the tapasin transmembrane region (e.g.…”

Section: Resultssupporting

confidence: 91%

Productive association between MHC class I and tapasin requires the tapasin transmembrane/cytosolic region and the tapasin C-terminal Ig-like domain

Georgesen

et al. 2012

Molecular Immunology

Technol Cancer Res Treat

“…14 Wu et al investigated key regulatory molecules involved in prostate cancer (PCA) metastasis in 2 human androgen-independent PCA cell lines, highly metastatic 1E8-H, and lowly metastatic 2B4-L cells by proteomics analyses. They found that calreticulin precursor was upregulated in highly metastatic cells.…”

Section: Discussionmentioning

confidence: 99%

Identification of Differentiation-Related Proteins in Gastric Adenocarcinoma Tissues by Proteomics

Zhou

Yao

Zhang

et al. 2016

There is a significant correlation between the degree of tumor differentiation and the survival of patients with gastric cancers. In this report, we compared proteomic differences between poorly differentiated gastric adenocarcinoma tissues and welldifferentiated gastric adenocarcinoma tissues in order to identify differentiation-related proteins that may be closely correlated with differentiation of gastric cancer pathogenesis. We identified 7 proteins, of which calreticulin precursor, tapasinERP57 heterodimer, pyruvate kinase isozymes M1/M2 isoform M2, class Pi glutathione S-transferase, and chain A crystal structure of human enolase 1 were upregulated in poorly differentiated gastric adenocarcinoma compared with well-differentiated gastric adenocarcinoma, while myosin-11 isoform SM2A and actin alpha cardiac were downregulated. Two of them, pyruvate kinase isozymes M1/M2 isoform M2 and enolase 1 are enzymes involved in glycolytic pathway. The upregulation of pyruvate kinase isozymes M1/M2 isoform M2 and enolase 1 in poorly differentiated gastric adenocarcinoma was confirmed by Western blotting and immunohistochemistry. Furthermore, we observed 107 cases with gastric adenocarcinoma and found that the high expression of pyruvate kinase isozymes M1/M2 isoform M2 and enolase 1 correlates with tumor size (P ¼ .0001 and P ¼ .0017, respectively), depth of invasion (P ¼ .0024 and P ¼ .0261, respectively), and poor prognosis of patients. In conclusion, with this proteomic analysis, pyruvate kinase isozymes M1/M2 isoform M2 and enolase 1 were identified upregulated in poorly differentiated gastric adenocarcinoma comparing with well-differentiated gastric adenocarcinoma. The expression level of pyruvate kinase isozymes M1/M2 isoform M2 and enolase 1 was significantly correlated with overall survival. Some of them would be differentiation-related cancer biomarkers and are associated with tumor metastasis, invasion, and prognosis.

“…Other alleles, such as HLA-B27, reach the cell surface but contain a suboptimal peptide repertoire [219]. In a recent study, one of us observed that presentation of two HLA-B*4402-restricted peptides derived from tumor proteins MAGE-A1 and MUM-1 was abolished in the presence of tapasin variants lacking the ability to recruit TAP and ERp57 to the peptide loading complex [220]. These results agreed with previous in vitro studies using recombinant proteins [217,221], and further confirmed that, in the ER environment, the interaction of tapasin with both TAP and ERp57 is required for optimal loading of MHC class I molecules.…”

Section: Tapasinmentioning

confidence: 99%

Insights into the processing of MHC class I ligands gained from the study of human tumor epitopes

Vigneron

Eynde

2011

Cell. Mol. Life Sci.

Self Cite

The molecular definition of tumor antigens recognized by cytolytic T lymphocytes (CTL) started in the late 1980s, at a time when the MHC class I antigen processing field was in its infancy. Born together, these two fields of science evolved together and provided each other with critical insights. Over the years, stimulated by the potential interest of tumor antigens for cancer immunotherapy, scientists have identified and characterized numerous antigens recognized by CTL on human tumors. These studies have provided a wealth of information relevant to the mode of production of antigenic peptides presented by MHC class I molecules. A number of tumor antigenic peptides were found to result from unusual mechanisms occurring at the level of transcription, translation or processing. Although many of these mechanisms occur in the cell at very low level, they are relevant to the immune system as they determine the killing of tumor cells by CTL, which are sensitive to low levels of peptide/MHC complexes. Moreover, these unusual mechanisms were found to occur not only in tumor cells but also in normal cells. Thereby, the study of tumor antigens has illuminated many aspects of MHC class I processing. We review here those insights into the MHC I antigen processing pathway that result from the characterization of human tumor antigens recognized by CTL.