Biochemical characterization of the human diabetes-associated HLA-DQ8 allelic product: similarity to the major histocompatibility complex class II I-A(g)7 protein of non-obese diabetic mice.
The human HLA-DQ8 (A1*0301/B1*0302) allelic product manifests a strong association with insulin-dependent diabetes mellitus (IDDM). Previous biochemical studies of the major histocompatibility complex (MHC) class II I-A(g)7 protein of IDDM-prone non-obese diabetic mice produced controversial results. To better define the biochemical properties of IDDM-associated MHC class II molecules, we analyzed DQ8 proteins, in comparison to other DQ allelic products, by partially denaturing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). We now report that DQ8 proteins have a normal peptide occupancy and lifespan in cells. Similar to I-A(g)7, DQ8 proteins formed only a minor fraction of SDS-stable complexes with peptides. Although this phenotype was not unique to DQ8, some DQ allelic products such as IDDM-protective DQ6 proteins were SDS resistant. The DQ9 allelic product, differing from DQ8 only at position (P) beta 57, was SDS stable, suggesting that non-Asp residues at beta 57 might decrease the SDS stability of DQ proteins. We identified a single peptide which specifically induced an SDS-stable conformation in DQ8 as well as in I-A(g)7 molecules. The residues at anchor P1 in this peptide were found to influence the SDS stability of both molecules. Together with our previous observation of similar binding motifs of I-A(g)7 and DQ8, these results demonstrate an overall biochemical similarity of mouse and human diabetes-associated MHC class II molecules. This similarity might contribute to a common immunological mechanism of IDDM in both species.
Reizis
B
B
Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
Altmann
D M
DM
Cohen
I R
IR
D000483:Alleles; D000818:Animals; D002461:Cell Line, Transformed; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D004198:Disease Susceptibility; D004591:Electrophoresis, Polyacrylamide Gel; D005802:Genes, MHC Class II; D006683:HLA-DQ Antigens / Q000737:chemistry* / Q000235:genetics; D000949:Histocompatibility Antigens Class II / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D006801:Humans; D051379:Mice; D016688:Mice, Inbred NOD; D011489:Protein Denaturation / Q000187:drug effects; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013045:Species Specificity; D013501:Surface-Active Agents / Q000494:pharmacology
D006683:HLA-DQ Antigens; D000949:Histocompatibility Antigens Class II; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate