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Van Lummel M.,Leiden University | Van Veelen P.A.,Leiden University | Zaldumbide A.,Leiden University | De Ru A.,Leiden University | And 6 more authors.
Journal of Biological Chemistry | Year: 2012

HLA-DQ2 and HLA-DQ8 are strongly predisposing haplotypes for type 1 diabetes (T1D). Yet HLA-DQ2/8 heterozygous individuals have a synergistically increased risk compared with HLA-DQ2 or HLA-DQ8 homozygote subjects that may result from the presence of a transdimer formed between the α-chain of HLA-DQ2 (DQA1*05:01) and the β-chain of HLA-DQ8 (DQB1*03:02). We generated cells exclusively expressing this transdimer (HLA-DQ8trans), characterized its peptide binding repertoire, and defined a unique transdimer-specific peptide binding motif that was found to be distinct from those of HLA-DQ2 and HLA-DQ8. This motif predicts an array of peptides of islet autoantigens as candidate T cell epitopes, many of which selectively bind to the HLA transdimer, whereas others bind to both HLA-DQ8 and transdimer with similar affinity. Our findings provide a molecular basis for the association between HLA-DQ transdimers and T1D and set the stage for rational testing of potential diabetogenic peptide epitopes. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc. Source


Behrens M.,Mayo Medical School | Papadopoulos G.K.,Epirus Institute of Technology | Moustakas A.,Technological Educational Institute of the Ionian Islands | Smart M.,Mayo Medical School | And 3 more authors.
Arthritis and Rheumatism | Year: 2011

Objective Certain HLA class II alleles are associated with susceptibility to the development of arthritis. However, the development of arthritis in some persons carrying non-rheumatoid arthritis (RA)-associated alleles remains unexplained. An individual who is heterozygous for the DQA1 and DQB1 genes can express the DQ molecule in cis or trans heterodimers. In a cis heterodimer, the α-chain interacts with the β-chain coded by the same chromosome, while in a trans heterodimer it interacts with the β-chain on the other chromosome. In this study, we used a humanized mouse model of arthritis in an attempt to determine whether a trans heterodimer of 2 nonassociated alleles, DQB1*0601 and DQB1*0604, can predispose to arthritis. Methods DQB1*0601 and*0604 occur in linkage with DQA1*0103 and*0102, respectively. To understand the role of trans heterodimers, we generated DQB1*0604/DQA1*0103-transgenic mice lacking endogenous HLA class II molecules. Results Severe arthritis developed in the DQB1*0604/A1*0103-trangenic mice, and an antigen-specific response was generated in vitro. DQB1*0604/DQA1*0103 presented type II collagen-derived peptides that were not presented by the arthritis-resistant DQB1*0601 allele, suggesting that trans heterodimer molecules between 2 DQB1 and DQA1 molecules may result in the presentation of unique antigens and susceptibility to the development of arthritis. Molecular modeling of type II collagen peptides showed that DQB1*0604/DQA1*0103 shares a p4 pocket with the arthritis-susceptible DQB1*0302 allele, suggesting a critical role of the p4 and p9 pockets in susceptibility to arthritis. Conclusion These results provide a possible explanation for the parental inheritance of nonsusceptibility alleles in some patients with RA and a mechanism by which they can predispose to the development of arthritis. Copyright © 2011 by the American College of Rheumatology. Source


Pavlidis I.V.,University of Ioannina | Vorhaben T.,University of Greifswald | Gournis D.,University of Ioannina | Papadopoulos G.K.,Epirus Institute of Technology | And 2 more authors.
Journal of Nanoparticle Research | Year: 2012

The interaction of enzymes with carbonbased nanomaterials (CBN s) is crucial for the functionof biomolecules and therefore for the design and development of effective nanobiocatalytic systems. In this study, the effect of functionalized CBN s, such as graphene oxide (GO) and multi-wall carbon nanotubes (CNT s), on the catalytic behaviour of various hydrolases of biotechnological interest was monitored and the interactions between CBN s and proteins were investigated. The enzyme-nanomaterial interactionssignificantly affect the catalytic behaviour of enzymes, resulting in an increase up to 60 % of the catalyticefficiency of lipases and a decrease up to 30 % of the esterase. Moreover, the use of CNT s and GO derivatives, especially those that are amine-functionalized, led to increased thermal stability of most the hydrolases tested. Fluorescence and circular dichroism studies indicated that the altered catalytic behaviour of enzymes in the presence of CBN s arises from specific enzyme-nanomaterial interactions, which can lead to significant conformational changes. In the case of lipases, the conformational changes led to a more active and rigid structure, while in the case of esterases this led to destabilization and unfolding. Kinetic and spectroscopic studies indicated that the extent of the interactions between CBN s and hydrolases can bemainly controlled by the functionalization of nanomaterials than by their geometry. © 2012 Springer Science+Business Media B.V. Source


Chow I.-T.,Benaroya Research Institute | James E.A.,Benaroya Research Institute | Tan V.,Benaroya Research Institute | Moustakas A.K.,Technological Education Institute of Ionian Islands | And 3 more authors.
Molecular Immunology | Year: 2012

This study characterized the unique peptide-binding characteristics of HLA-DRB1*12:01 (DR1201), an allele studied in the context of various autoimmune diseases, using a peptide competition assay and structural modeling. After defining Influenza A/Puerto Rico/8/34 Matrix Protein M1 (H1MP) 40-54 as a DR1201 restricted epitope, the critical anchor residues within this sequence were confirmed by measuring the relative binding of peptides with non-conservative substitutions in competition with biotin labeled H1MP 40-54 peptide. Based on this information, a set of peptides was designed with single amino acid substitutions at these anchor positions. The overall peptide binding preferences for the DR1201 allele were deduced by incubating these peptides in competition with the reference H1MP 40-54 to determine the relative binding affinities of each to recombinant DR1201 protein. As expected, pocket 1 preferred methionine and aliphatic residues, and tolerated phenylalanine. Pocket 4 was mostly composed of hydrophobic residues, thereby preferentially accommodating aliphatic residues, but could also weakly accommodate lysine due to its slightly acidic environment. Pocket 6 accepted a wide range of amino acids because of the diverse residues that comprise this pocket. Pocket 9 accepted aliphatic and negatively charged amino acids, but showed a remarkable preference for aromatic residues due to the conformation of the pocket, which lacks the typical salt bridge between β57Asp and α76Arg. These binding characteristics contrast with the closely related DR1104 allele, distinguishing DR1201 among the alleles of the HLA-DR5 group. These empirical results were used to develop an algorithm to predict peptide binding to DR1201. This algorithm was used to verify T cell epitopes within novel antigenic peptides identified by tetramer staining and within peptides from published reports that contain putative DR1201 epitopes. © 2011 Elsevier Ltd. Source


Delli A.J.,Lund University | Vaziri-Sani F.,Lund University | Lindblad B.,Gothenburg University | Elding-Larsson H.,Lund University | And 12 more authors.
Diabetes | Year: 2012

We examined whether zinc transporter 8 autoantibodies (ZnT8A; arginine ZnT8-RA, tryptophan ZnT8-WA, and glutamine ZnT8-QA variants) differed between immigrant and Swedish patients due to different polymorphisms of SLC30A8, HLA-DQ, or both. Newly diagnosed autoimmune (≥1 islet autoantibody) type 1 diabetic patients (n = 2,964, <18 years, 55% male) were ascertained in the Better Diabetes Diagnosis study. Two subgroups were identified: Swedes (n = 2,160, 73%) and immigrants (non-Swedes; n = 212, 7%). Non-Swedes had less frequent ZnT8-WA (38%) than Swedes (50%), consistent with a lower frequency in the non-Swedes (37%) of SLC30A8 CT+TT (RW+WW) genotypes than in the Swedes (54%). ZnT8-RA (57 and 58%, respectively) did not differ despite a higher frequency of CC (RR) genotypes in non-Swedes (63%) than Swedes (46%). We tested whether this inconsistency was due to HLA-DQ as 2/X (2/2; 2/y; y is anything but 2 or 8), which was a major genotype in non-Swedes (40%) compared with Swedes (14%). In the non-Swedes only, 2/X (2/2; 2/y) was negatively associated with ZnT8-WA and ZnT8-QA but not ZnT8-RA. Molecular simulation showed nonbinding of the relevant ZnT8-R peptide to DQ2, explaining in part a possible lack of tolerance to ZnT8-R. At diagnosis in non-Swedes, the presence of ZnT8-RA rather than ZnT8-WA was likely due to effects of HLA-DQ2 and the SLC30A8 CC (RR) genotypes. © 2012 by the American Diabetes Association. Source

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