Zeliszewski D, Golvano J J, Gaudebout P, Dorval I, Freidel C, Gebuhrer L, Betuel H, Borras-Cuesta F, Sterkers G
INSERM CJF 90.15, Hôpital R. Debré, Paris, France.
J Immunol. 1993 Dec 1;151(11):6237-47.
To get further insight into the role of three polymorphic DR residues located in one alpha-helix of the HLA-DR binding groove, we studied how natural substitutions at positions 67, 71, and 86 on DR11 molecules influence MHC binding and/or T cell recognition of peptide HA306-320 and of monosubstituted peptide analogues. Our results show that: 1) Reactivities of all HA306-320-specific T cell clones tested are decreased by DR substitution at position 86 and can even be lowered by additional substitutions at position 71, and at positions 71 plus 67, indicating that these three residues are functionally important. 2) The functional effects of substitutions at positions 67, 71, and/or 86 cannot be explained by a decreased affinity of HA306-320 for the substituted DR11 molecules, as determined in binding assays. 3) More likely, they are explained by modifications of the conformation, orientation, or location of the peptide once bound in the HLA groove, because each individual DR substitution at positions 86, 71, and 67 differentially affects the binding ability of the same panel of 50 monosubstituted analogues. 4) This interpretation is reinforced by the identification of a small set of monosubstituted analogues that can compensate the functional effects of DR substitutions at positions 86, 86 plus 71, or 86 plus 71 plus 67, and thus restore T cell reactivities. All together these results strongly suggest that residues 67, 71, and 86 play a key role in interactions with HA306-320, probably by modifying the way the peptide is bound within the binding groove of HLA-DR11. Using the same DR11.1-restricted clones, we identified putative T cell and DR contact residues of HA306-320 by comparing DR binding and T cell-activating capacity of the peptide analogues. This analysis suggests that: 1) Residues 310, 311, 312, 313, and 316 are putative TCR contacts. 2) Peptide HA306-320 anchors to DR11.1 molecules mainly via residue Y-309, possibly at the vicinity of DR residue 86, whereas peptide residues 315 and 317 constitute minor aggregotopes that would be at the vicinity of DR residues 71 and/or 67. 3) Finally, residues 308, 310, and 314 might also be on the MHC side of the DR-peptide-TCR complex.
为了更深入了解位于HLA - DR结合槽一个α螺旋中的三个多态性DR残基的作用,我们研究了DR11分子上第67、71和86位的天然取代如何影响MHC对肽HA306 - 320以及单取代肽类似物的结合和/或T细胞识别。我们的结果表明:1)所测试的所有HA306 - 320特异性T细胞克隆的反应性因第86位的DR取代而降低,甚至在第71位以及第71位加67位有额外取代时反应性会进一步降低,这表明这三个残基在功能上很重要。2)如结合试验所测定,第67、71和/或86位取代的功能效应不能用HA306 - 320对取代的DR11分子亲和力降低来解释。3)更有可能的是,它们是由肽一旦结合在HLA槽中的构象、方向或位置的改变所解释,因为在第86、71和67位的每个单独的DR取代对同一组50个单取代类似物的结合能力有不同影响。4)一小部分单取代类似物能够补偿第86位、第86位加71位或第86位加71位加67位的DR取代的功能效应,从而恢复T细胞反应性,这一发现进一步支持了这一解释。所有这些结果强烈表明,第67、71和86位残基在与HA306 - 320的相互作用中起关键作用,可能是通过改变肽在HLA - DR11结合槽内的结合方式。使用相同的DR11.1限制性克隆,我们通过比较肽类似物的DR结合和T细胞激活能力,确定了HA306 - 320的推定T细胞和DR接触残基。该分析表明:1)第310、311、312、313和316位残基是推定的TCR接触位点。2)肽HA306 - 320主要通过Y - 309残基锚定到DR11.1分子上,可能在DR残基86附近,而肽残基315和317构成较小的聚集表位,可能在DR残基71和/或67附近。3)最后,第308、310和314位残基也可能位于DR - 肽 - TCR复合物的MHC一侧。