Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

T2 cells have a large homozygous deletion in the MHC II region. Transfection of MHC class II genes into T2 cells allows presentation of peptide but not native protein Ags. This defect in protein presentation has been attributed to the lack of HLA-DM, an MHC class II-related protein that facilitates the release of an invariant chain peptide (CLIP) intermediate from nascent MHC class II proteins within the endocytic compartment of APC. Here, we show that Ak molecules within isolated late endosome fractions of T1.Ak (wild-type) vs T2.Ak (HLA-DM-deficient) bind biotin-HEL46-61 at comparable levels, consistent with previous observations that Ak molecules on T2 cells are not predominantly occupied with CLIP. However, Ak molecules in the late endosomes of T2.Ak fail to present peptide to a T hybrid, whereas the late endosomes from T1.Ak have no such defect. Transfection of HLA-DM A and B into T2.Ak partially restores protein Ag presentation by T2.Ak cells. These data suggest that HLA-DM can play a role in Ag presentation in addition to its role in CLIP release. However, even after DM transfection there remains a 10-fold difference in the dose-response curve for hen egg lysozyme presentation by T1.Ak vs T2.Ak/DM cells. In addition, HLA-DM transfection fails to restore presentation by late endosome fractions. The failure to fully restore Ag presentation in T2.Ak cells by DM transfection suggests that another gene product, required for efficient Ag presentation, may be absent from the late endosomes of T2.
 ...
PMID:Effect of HLA-DM transfection on hen egg lysozyme presentation by T2.Ak cells. 880 21

A bound conformation of the antigenic decapeptide hen egg lysozyme HEL[52-61] associated to the mouse MHC class II (MHC II) I-Ak was modeled by homology with the three-dimensional structure of hemagglutinin HA[306-318]-HLA-DR1 complex. HEL peptide Tyr53 could not be aligned with the HA peptide Tyr308 because this resulted in a buried Tyr53 side chain within the I-Ak peptide-binding groove and this conflicted with this side chain being recognized by T cells. Therefore, Asp52 of HEL was fixed as the P1 anchor and aligned on Tyr308 of HA. After molecular dynamics, the modeled complex was stable even in the absence of any constraint. The peptide backbone adopted a polyproline II-like conformation with canonical hydrogen bonding between the peptide backbone and MHC II molecule. Asp52, IIe55, Gin57 and Ser60 were predicted to be deeply buried into P1, P4, P6 and P9 MHC II pockets, and Tyr53, Leu56, Asn59 and Arg61 as TCR contacting residues. The modeling of 15 complexes associating I-Ak with peptides derived from HEL[52-61] by single amino acid substitution proved stable with conserved hydrogen bonds and side chain orientation compatible with their recognition by two T cell hybridomas. Moreover, comparison with the recently solved crystal structure of the related HEL[50-62]-I-Ak complex revealed striking similarities.
 ...
PMID:Molecular modeling of hen egg lysozyme HEL[52-61] peptide binding to I-Ak MHC class II molecule. 988 96

Here, we report on an elderly woman with sarcoidosis and Hashimoto's disease who later developed myasthenia gravis. She was 68-year-old with a long history of Hashimoto's disease who had a clinical diagnosis of sarcoidosis with uveritis at the age of 66 years. On laboratory examination, angiotensin-converting enzyme, lysozyme and gamma-globulin were elevated and there was bilateral hilar lymphoadenopathy. She was admitted to our hospital because of left blepharoptosis and mild fatigability in the proximal muscles at the age of 68 years. Myasthenia gravis, type IIa, was confirmed by elevated titer of anti-acetylcholine receptor antibody in serum (0.8 nmol/l, normal < 0.6), positive edrophonium test and decremental EMG response. Oral prednisolone therapy was effective. Her muscle biopsy revealed HLA ABC-positive fibers in all fascicles, and HLA-DR positive fibers in the perifascicular areas. Myasthenia gravis complicated by sarcoidosis and Hashimoto's thyroiditis is extremely rare, suggesting that the common underlying immunological abnormalities for the three disorders such as a certain defective cellular immunity are responsible for the pathomechanism to induce the patient condition.
 ...
PMID:[A case of myasthenia gravis following sarcoidosis and Hashimoto's thyroiditis]. 1121 99

Discovery of a number of novel and known human genes whose protein products bear striking similarity to two or more wheat gliadin domains raised the possibility that human intestinal non-HLA peptides homologous to celiac T-cell epitopes could play a role in non-HLA gene specification in celiac disease. Database searching of the entire human genome identified only 11 gut-expressed proteins with high T-cell epitope homology, particularly to the DQ2-gamma-I-gliadin epitope (i.e. TFIIA, FOXJ2 and IgD; mean BestFit quality score=40 versus random value of 24). Others were similar to DQ2-alpha-I-gliadin (i.e. PAX9; BestFit quality 46 versus 20 for random), or DQ2-alpha-II-gliadin (PHLDA1, known in mice as the T-cell death-associated gene; BestFit quality 43 versus 30 for random) epitopes. Among proteins previously screened for gliadin homology, noteworthy was achaete scute homologous protein (DQ2-alpha-I-gliadin; BestFit quality 41 versus 22 for random). With the exception of IgD, all are nuclear factors. Paying particular attention to the position of potential major histocompatibility complex (MHC) anchor residues, several were selected for testing in a DQ2-gamma-I-gliadin-restricted T-cell system. All native 10-mer peptides were inactive, even when deamidated, but V96F substitution of deamidated TFIIA amino acid residues 91-100 stimulated IL-2 release at levels exceeding the wheat gliadin positive control. Also active, but only slightly, was L1009F substitution of AIB3 amino acid residues 1004-1013. PlotSimilarity alignment of TFIIAs from eight species revealed subthreshold similarity score in the peptide region, in contrast to the highly conserved amino and carboxy termini. Molecular modeling of TFIIA[V96F] peptide points to an important juxtaposition of an upwardly projecting phenylalanine residue at peptide position 6 that likely contacts a receptor complementarity-determining region, and a downwardly projecting glutamic acid residue that fits into the shallow MHC P7 pocket. These observations tentatively point to a new multi-gene hypothesis for the initiation of celiac disease in which deamidated free human peptides with T-cell epitope homology (particularly those made more homologous by mutation) escape negative selection, as per deamidation of the HEL(48-62) peptide in the hen egg lysozyme model of autoimmunity. Deamidation following peptide release due to injury triggers inflammation, thereafter repeatedly provoked by dietary gliadin immunodominant peptides concentrated in the proximal small intestine.
 ...
PMID:Human genome search in celiac disease: mutated gliadin T-cell-like epitope in two human proteins promotes T-cell activation. 1205 57

We quantitated the amounts of peptides from hen egg-white lysozyme presented by I-A(k) molecules in APC lines. The large chemical gradient of presentation of the four hen egg-white lysozyme epitopes observed in cell lines expressing HLA-DM or H-2DM (referred to in this study as DM) was significantly diminished in the T2.A(k) line lacking DM. Differences in levels of presentation between wild-type and DM-deficient APC were observed for all four epitopes, but differences were most evident for the highest affinity epitope. As a result of these quantitative differences in display, presentation of all four epitopes to T cells was impaired in the line lacking DM. The binding affinity of the pool of naturally processed peptides from DM-expressing lines was higher than that from the DM-deficient line. Thus, using a direct biochemical approach in APC, we demonstrate that DM influences the selection of peptides bound to MHC class II by favoring high affinity peptides.
 ...
PMID:Cutting edge: H-2DM is responsible for the large differences in presentation among peptides selected by I-Ak during antigen processing. 1292 60

We present a 1-year-old boy who developed a cutaneous lesion on the trunk and hepatosplenomegaly. Laboratory examination showed leukocytosis with peripheral blasts, atypical monocytosis, anemia, hyper IgG, and a mild elevation of C-reactive protein. Clinical features and skin biopsy findings matched the diagnostic criteria of both juvenile myelomonocytic leukemia (JMML) and Langerhans cell histiocytosis (LCH). Histopathology revealed atypical mononuclear cells that had infiltrated around vessels throughout the dermis in a skin biopsy specimen. These cells were CD1a (+), S-100 (+), CD68 (+), CD207 (-), lysozyme (+), and myeloperoxidase (-). The diagnosis of JMML was confirmed by detection of spontaneous colony formation and granulocyte-macrophage colony-stimulating factor hypersensitivity in vitro, and a somatic NRAS point mutation. Transplantation of bone marrow from an HLA-matched unrelated donor was performed, and the marrow was successfully engrafted. The cutaneous lesion and hepatosplenomegaly were improved at the time of discharge. It is often difficult to distinguish between JMML and LCH-like infiltrates by assessing clinical and light microscopic features of various cutaneous lesions. In the current case, molecular biological analysis enabled us to develop a precise diagnosis.
 ...
PMID:Juvenile myelomonocytic leukemia characterized by cutaneous lesion containing Langerhans cell histiocytosis-like cells. 2135 Aug 22


<< Previous 1 2 3