The Bw4/Bw6 difference between HLA-B*0802 and HLA-B*0801 changes the peptides endogenously bound and the stimulation of alloreactive T cells

 HLA-B^*0801 is unique among HLA-B allotypes in having dominant amino acid anchors at positions 3 and 5 of the peptide-binding motif. HLA-B^*0802 is a variant of HLA-B^*0801 in which the Bw6 sequence motif is replaced by a Bw4 sequence motif. This change, involving substitutions at positions 77, 80, 81, 82, and 83 of the B^*08 heavy chain, is probably the result of a single evolutionary event of interallelic conversion. Moreover, the difference between B^*0802 and B^*0801 is sufficient to stimulate a cytotoxic T-cell response. To assess further the functional impact of the Bw4 motif on a B8 background, we compared the peptide-binding specificity of the B^*0801 and B^*0802 allotypes by sequencing the mixture of peptides endogenously bound to B^*0802 and 12 individual peptides purified from that mixture. The HLA-B^*0802 allotype, while able to bind some peptides bound by B^*0801, has a broader repertoire of endogenously bound peptides than B^*0801: the peptides bound by B^*0802 are more variable in length and exhibit greater diversity in the carboxyl-terminal amino acid which interacts with the F pocket. Received: 29 October 1997     

Genetic and serological heterogeneity of the supertypic HLA-B locus specificities Bw4 and Bw6

Gene cloning and sequencing of theHLA-B locus split antigens B38 (B16.1) and B39 (B16.2) allowed localization of their subtypic as well as their public specificities HLA-Bw4 or-Bw6 to the α-helical region of the α 1 domain flanked by the amino acid positions 74–83. Comparison of their amino acid sequences with those of otherHLA-B-locus alleles established HLA-Bw6 to be distinguished by Ser at residue 77 and Asn at residue 80. In contrast, HLA-Bw4 is characterized by at least seven different patterns of amino acid exchanges at positions 77 and 80–83. Reactivity patterns of Bw4-or Bw6-specific monoclonal antibodies reveal two alloantigenic epitopes contributing to the HLA-Bw4 or-Bw6 specificity residing next to the region of highest diversity of the α 1 domain.     

The primary structure of HLA-A32 suggests a region involved in formation of the Bw4/Bw6 epitopes

All HLA-B locus molecules have either the Bw4 or Bw6 epitopes. In addition, the Bw4 epitope is found on HLA-Aw23, Aw24, and A32, and Bw6 is also found on HLA-Cw3. The structural basis for these determinants and the evolution of their distribution among products of the HLA-B locus has been a long standing puzzle. To identify residues that may be involved in these determinants, we have cloned a gene for A32 and sequenced the protein encoding exons. Comparison of the predicted protein sequence with other HLA-A,B,C sequences identified residues 79 through 83 of the alpha 1 domain as having a pattern of polymorphic substitution that correlates with the presence and absence of the Bw4 and Bw6 epitopes.     

The "public" determinants HLA-Bw4/Bw6 do not generate cytotoxic T lymphocytes (CTLs)

The human leucocyte antigens (HLA)-Bw4/Bw6 antigens detected serologically are "public" determinants located in the HLA-B molecule. They do not generate cytotoxic T lymphocytes (CTLs) in primary allogeneic cultures (mixed lymphocyte antigens) and secondary (primed lymphocyte typing) cultures indicate that they do not behave like normal HLA "private" cell-mediated lympholysis determinants. Therefore, the contribution of the 79-83 (alpha 1) residues in the generation of the epitopes Bw4/Bw6 does not seem to be critical for the examination by T cell receptor in allogeneic CML. The different overlapping patterns of the serological and CTL examinations are discussed, based on the structure of HLA class I antigens.     

HLA-B51 and HLA-Bw52 differ by only two amino acids which are in the helical region of the alpha 1 domain

Genes encoding the serologically cross-reactive HLA-B51 and HLA-Bw52 molecules were isolated and the exons sequenced. HLA-B51 genes obtained from Caucasian and Oriental individuals were identical. HLA-Bw52 differs from HLA-B51 by four nucleotide substitutions in exon 2 encoding the alpha 1 domain. These comprise one isolated silent substitution in codon 23 and a cluster of three coding substitutions in codons 63 and 67. Amino acid substitutions of N----E at position 63 and F----S at position 67 are the only differences between HLA-B51 and HLA-Bw52 and these residues are postulated to form HLA-B51 specific epitopes. HLA-B51 could have been formed from HLA-Bw52 by the combination of a genetic exchange with HLA-B8 and a point mutation. Similarity of HLA-B51 and HLA-Bw52 with HLA-Bw58 suggest they also share a common ancestor.     

Quantitative estimation of HLA-A and HLA-B antigens carrying the Bw4 supertypic specificity in human peripheral blood lymphocytes

A monoclonal antibody specific for HLA-Bw4 was employed for the quantitative estimation of class I antigens on human peripheral blood lymphocytes and on the human macrophage cell line U 937. The epitopes reactive with the HLA-Bw4-specific antibody, which are present on different antigens coded by the HLA-A or the HLA-B locus, were characterized in terms of equilibrium and kinetic binding parameters. The level of expression of class I antigens on human lymphocytes was found to be in direct proportion to the gene dose. Variations between donors of the same phenotype were of minor importance. Estimation of the association constant, association rate constant, and half-life of dissociation for the interaction of the antibody with lymphocytes heterozygous for either HLA-A24, HLA-A32, HLA-A9, or HLA-Bw4 strongly suggested that the public antigenic determinant shared by these antigens is identical.     

Antigenic determinants of the HLA-B7 molecule; Bw6- and B7-specific determinants are spatially separate

Monoclonal antibodies that bind HLA-B7 were used to show that the B7-specific determinant is at a topologically different site from that of the broad polymorphic, Bw6 determinant. The relationship to other antigenic determinants defined by monoclonal antibodies was also assessed. These results were independently obtained in four ways: (1) by cellular blocking assays, in which there was no inhibition of 125I-B7 antibody binding in the presence of Bw6 antibody and no inhibition of 125I-Bw6 antibody binding in the presence of B7 antibody; (2) cellular binding assays under conditions of antibody saturation showed the binding of B7-specific and Bw6 antibodies were additive; (3) solid-phase radioimmune assays demonstrated enhancement between B7-specific and Bw6 antibodies; (4) analysis of antigen antibody complexes by size-exclusion high pressure liquid chromatography showed Bw6 and B7 antibodies could form tetramolecular complexes with papain-solubilized HLA-B7. Limitations were encountered in using cellular blocking assays to map antigenic determinants of HLA-B7. These assays can produce blocking in cases where two antibodies are not competing for an antigenic determinant. Mapping antigenic determinants with assays using purified HLA-B7 as the antigenic target, in addition to cell-based assays, provided a more accurate picture.     

Redundancy and Complementarity between ERAP1 and ERAP2 Revealed by their Effects on the Behcet's Disease-associated HLA-B*51 Peptidome,

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Highlights

• •HLA-B*51 and ERAP1, but not ERAP2, are risk factors for Behçet's disease.
• •The HLA-B*51 peptidome and the effects of ERAP1 and ERAP2 on it are analyzed.
• •ERAP1 and ERAP2 alter multiple features of the HLA-B*51 peptidome in distinct ways.
• •Both enzymes act independently with complementary and partially redundant functions.

     

Studies of interactions between uracil-based hybrid molecules and P-glycoprotein--search for multidrug resistance modulators

The hybrid molecules having structural features of anticancer drug, 5-fluorouracil, and MDR modulator, propafenone, have been studied for their interactions with P-glycoprotein (P-gp). Some of the molecules (5, 8, and 9) show considerable interactions with P-gp and could be the potential candidates for their in vivo evaluation as MDR modulators. Further investigations show the dependence of P-gp interacting properties of these compounds on their physico-chemical parameters like logP and total polar surface area.     

Characterization and function of human Ly-6/uPAR molecules

Human Ly-6/uPAR molecules are a superfamily composed of two subfamilies; one is the membrane bound proteins with a GPI-anchor and the other are secreted proteins without the GPI-anchor. Ly-6/uPAR molecules have remarkable amino acid homology through a distinctive 8-10 cysteine-rich domain that is associated predominantly with O-linked glycans. These molecules are encoded by multiple tightly linked genes located on Chr. 8q23, and have a conserved genomic organization. Ly-6/uPAR molecules have an interesting expression pattern during hematopoiesis and on specific tumors indicating that Ly-6/uPAR molecules are associated with development of the immune system and carcinogenesis. Thus, Ly-6/uPAR molecules are useful antigens for diagnostic and therapeutic targets. This review summarizes our understanding of human Ly-6/uPAR molecules with regard to molecular structure as well as what is known about their function in normal and malignant tissues and suggest Ly-6/uPAR molecules as target antigens for cancer immunotherapy. [BMB Reports 2012; 45(11): 595-603]     

Design and synthesis of antimicrobial,anticoagulant, and anticholinesterase hybrid molecules from 4-methylumbelliferone

We designed and synthesized new series of diverse triazoles, isoxazoles, isoxazolines, and aziridines linked 4-methylumbelliferone 1 using intermolecular 1,3-dipolar cycloaddition reactions. Structures of these compounds were established on the basis of ¹H NMR, ¹³C NMR, and ESI-HRMS. All prepared compounds were evaluated for their antimicrobial, anticoagulant, and anticholinesterase activities. Interestingly, among the tested molecules, some of the analogs displayed better activities than the parent 4-methylumbelliferone 1 such as 6a and 6d for their antifungal properties. Moreover, compounds 4, 5, 6, and 7 showed the importance of the added fragments to 4-methylumbelliferone 1 via the linker methylene to have good activity.     

Real-time assembly and disassembly of human RAD51 filaments on individual DNA molecules

The human DNA repair protein RAD51 is the crucial component of helical nucleoprotein filaments that drive homologous recombination. The molecular mechanistic details of how this structure facilitates the requisite DNA strand rearrangements are not known but must involve dynamic interactions between RAD51 and DNA. Here, we report the real-time kinetics of human RAD51 filament assembly and disassembly on individual molecules of both single- and double-stranded DNA, as measured using magnetic tweezers. The relative rates of nucleation and filament extension are such that the observed filament formation consists of multiple nucleation events that are in competition with each other. For varying concentration of RAD51, a Hill coefficient of 4.3 ± 0.5 is obtained for both nucleation and filament extension, indicating binding to dsDNA with a binding unit consisting of multiple (≥4) RAD51 monomers. We report Monte Carlo simulations that fit the (dis)assembly data very well. The results show that, surprisingly, human RAD51 does not form long continuous filaments on DNA. Instead each nucleoprotein filament consists of a string of many small filament patches that are only a few tens of monomers long. The high flexibility and dynamic nature of this arrangement is likely to facilitate strand exchange.     

Kinetics of interaction between 3-hydroxyphthaloyl-beta-lactoglobulin and CD4 molecules.

Kinetics of 3-hydroxyphthaloyl-beta-lactoglobulin-CD4 interaction were evaluated using a biosensor instrument based on surface plasmon resonance. A very fast association (k(a)=2.4+/-0.3x10(6)M(-1)s(-1)) and slow dissociation (K(d)=2.3+/-0.14x10(-4)s(-1)) rate constants were observed indicating the high affinity of the complex. This result together with earlier data, suggest that "structure-specific" requirements must be met to endow acid anhydride modified lactoglobulin with the capacity for high affinity binding to CD4.     

SLC6A4基因多态性与海洛因依赖的关联性研究

目的:探讨5-羟色胺转运体基因(solute carrier family 6 member 4,SLC6A4)基因4个单核苷酸多态性(single nucleotide polymorphism,SNP)位点与海洛因依赖之间的关系。方法:严格按照诊断标准,选取无亲缘关系的海洛因依赖个体397例(病例组)及健康对照个体402例(对照组)提取基因组DNA,采用SNaPshot SNP分型技术对SLC6A4基因4个SNP位点(rs1042173,rs3813034,rs6354,rs7224199)进行基因分型,比较病例-对照组间各位点等位基因、基因型频率的差异。结果:病例组和对照组SLC6A4基因rs1042173和rs3813034位点的基因型和等位基因频率比较存在显著性差异(P0.05),rs1042173的C等位基因(P=0.031,OR=1.317,95%CI=1.026-1.691)及rs3813034的C等位基因(P=0.013,OR=1.375,95%CI=1.069-1.768)是海洛因依赖的危险因素。病例组TCC单倍型(rs7224199、rs3813034和rs1042173)的比例较对照组显著增高(P0.05)。结论:SLC6A4基因rs1042173和rs3813034多态性可能与海洛因成瘾有关,携带有rs1042173的C等位基因和rs3813034的C等位基因的个体及携带TCC单倍型的个体可能更容易对海洛因产生依赖。     

Conservation and alteration of HLA-B27-specific T cell epitopes on mouse cells. Implications for peptide-mediated alloreactivity.

Alloreactive CTL responses generate a great variety of clonal specificities. Such diversity may be related to recognition of multiple peptides constitutively bound to any given MHC alloantigen. Among human alloreactive CTL, only a fraction of the clones lyse mouse P815 cells expressing class I HLA proteins. In this study the fine specificity of HLA-B27 allorecognition on human or mouse cells by five human HLA-B27-specific CTL clones was comparatively analyzed. This was done to examine what degree of variation in epitope structure is compatible with recognition of HLA Ag on mouse cells. Nine site-specific HLA-B27 mutants were expressed on both human and mouse cells, after DNA-mediated gene transfer, to construct two analogous series of target cells. The reaction patterns of four of the five CTL clones with these cell panels were compatible with conservation of their corresponding epitopes upon expression of HLA-B27 on mouse cells. The reaction pattern of the fifth clone was different with either cell panel, indicating that its epitope was structurally altered on mouse cells. It also suggested a selectively increased expression of the determinant on these cells. The results suggest that most of the epitopes recognized by allospecific CTL clones reacting across species are either independent of any bound peptide or involve identical peptides from both cell types. However, some of these clones recognize alloantigen-bound peptides that are somewhat different in structure depending on the cell type, and may be expressed at the mouse cell surface in greater amounts. Such peptides could arise from related proteins in both species, and be polymorphic as a result of phylogenetic divergence.