Conversion of Tyrosine to the Inflammation-Associated Analog 3′-Nitrotyrosine at Either TCR- or MHC-Contact Positions Can Profoundly Affect Recognition of the MHC Class I-Restricted Epitope of Lymphocytic Choriomeningitis Virus Glycoprotein 33 by CD8 T Cells

Abstract

Immunohistochemical detection of increased levels of protein-associated nitrotyrosine has become widely used as a surrogate marker of in situ inflammation. However, the potential consequences of protein-associated nitrotyrosine formation in terms of cellular immune recognition has received surprisingly little attention. Using a well-defined I-EK-restricted epitope of pigeon cytochrome c, we previously demonstrated that conversion of a single tyrosine residue to nitrotyrosine can have a profound effect on recognition by CD4 T cells. In this study, we used the MHC class I-restricted epitope of lymphocytic choriomeningitis virus glycoprotein (gp33) to demonstrate that conversion of tyrosine to nitrotyrosine can also profoundly affect recognition of MHC class I-restricted epitopes. Conversion of the Y4 residue of the gp33 epitope to nitrotyrosine completely abrogated recognition by gp33-specific T cells from P14 TCR-transgenic mice. In contrast, CD8+ T cells specific for “nitrated gp33” (NY-gp33) can be readily elicited in C57BL/6 mice after immunization with NY-gp33 peptide. Interestingly, T-T hybridomas specific for NY-gp33 peptide were found to fall into two distinct subsets, being specific for NY-gp33 presented in the context of either H-2Db or H-2Kb. This latter result is surprising in light of previous structural studies showing that Y4 comprises a critical TCR-contact residue when presented by H-2Db but that the same residue points downward into the peptide-binding groove of the MHC when presented by H-2Kb. Together, these results indicate that nitrotyrosine formation can impact T cell recognition both directly, through alteration of TCR-contact residues, or indirectly, through alterations in MHC-contact positions.

Tumor-infiltrating myeloid cells induce tumor cell resistance to cytotoxic T cells in mice

“…NO and PNT, which are major components of this system, are extremely effective in causing nitrosylation of the 4 amino acids: tyrosine, tryptophan, cysteine, and methionine. Previous studies have demonstrated that the conversion of tyrosine residues to NT was sufficient to block the binding of peptide epitopes to MHC class I and class II (28)(29)(30). Here we confirmed this effect of PNT in tumor cells.…”

“…This observation was consistent with reports in different experimental systems that conversion of a single tyrosine residue to NT can profoundly affect the recognition of MHC class II- and class I-restricted epitopes by CD4 + and CD8 + T cells, respectively (29,30).…”

Tumor-induced myeloid deviation: when myeloid-derived suppressor cells meet tumor-associated macrophages

“…ROS affect T cell fitness by downregulating CD3ζ chain expression and reducing cytokine secretion, as observed in pancreatic cancer (81). RNS, such as peroxynitrite (ONOO -), are byproducts of the combined activity of iNOS, ARG1, and NOX2 and can alter the formation of a correct peptide-MHC complex in MHCI molecules or induce modification of the immunodominant tumor-antigen peptides, thereby affecting TCR recognition and T cell activation (82). RNS can act on α and β chains of the TCR, promoting dissociation of the CD3ζ chain from the TCR complex and preventing TCR signaling (83).…”

Mechanistic studies of the immunochemical termination of self-tolerance with unnatural amino acids

“…Indeed, the nonspecific derivatization of autologous cancer cells with dinitrophenyl groups has been exploited as a vaccine in melanoma patients (9), and physiological 3-nitrotyrosine formation has been implicated in the pathology of a number of autoimmune diseases (10)(11)(12). To test whether this immunogenic group could be used to break tolerance to specific selfproteins, we previously introduced a p-nitrophenylalanine (pNO 2 Phe) residue at a single site in murine TNF-␣.…”