Complementarity determining region 1 (CDR1)- and CDR3-analogous regions in CTLA-4 and CD28 determine the binding to B7-1.
Complementarity determining region 1 (CDR1)- and CDR3-analogous regions in CTLA-4 and CD28 determine the binding to B7-1.
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DOI：
10.1084/jem.180.6.2049
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发表时间：
1994-12-01
期刊：
影响因子：
--
通讯作者：
Linsley PS
中科院分区：
文献类型：
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作者：
Peach RJ;Bajorath J;Brady W;Leytze G;Greene J;Naemura J;Linsley PS
T细胞表面受体CD 28和CTLA-4是免疫球蛋白超家族（IgSF）的同源成员，各自包含单个V样胞外结构域。CD 28和CTLA-4与抗原递呈细胞（APC）上的B7-1和B7-2反受体结合，从而触发对体外和体内最佳T细胞活化重要的共刺激途径。可溶形式的CD 28和CTLA-4（其中V样细胞外结构域与IG恒定结构域融合（CD 28 IG和CTLA 4 IG））已被用于研究它们与B7-1和B7- 2的相互作用，其中CTLA 4 IG比CD 28 IG更强地结合B7-1（亲合力高约20倍）。我们现在已经通过位点特异性和同源诱变，鉴定了CTLA 4 Ig中对B7-1强结合重要的区域。互补决定区3（CDR 3）样区中的六肽基序（MYPPPY）在所有CD 28和CTLA-4家族成员中是完全保守的。通过CTLA 4 Ig中的基序和CD 28 Ig中的选定残基的丙氨酸扫描诱变减少或消除了与B7-1的结合。构建了嵌合分子HS 4、HS 4-A和HS 4-B，其中CTLA-4的CDR 3样区（COOH末端延伸以包括非保守残基）被移植到CD 28 Ig上。这些同源突变体与B7-1的结合比CD 28 Ig强。将CTLA-4的CDR 1-样区（其在CD 28中不保守并且预测在空间上与CDR 3相邻）移植到HS 4和HS 4-A中，产生了甚至更好地结合B7-1的嵌合分子（HS 7和HS 8）。将CTLA-4的CDR 2样结构域包含到HS 7和HS 8中不会进一步增加结合。因此，CTLA 4 Ig和CD 28 Ig的MYPPPY基序对于它们与B7-1的结合是重要的，但是CTLA 4 Ig的这种结合强度的增加是由CDR 1-和CDR 3-类似区中的非保守残基介导的。
T cell surface receptors CD28 and CTLA-4 are homologous members of the immunoglobulin superfamily (IgSF), each comprising a single V-like extracellular domain. CD28 and CTLA-4 bind to the B7-1 and B7-2 counter- receptors on antigen presenting cells (APCs), thereby triggering a costimulatory pathway important for optimal T cell activation in vitro and in vivo. Soluble forms of CD28 and CTLA-4 in which the V-like extracellular domains were fused to Ig constant domains (CD28Ig and CTLA4Ig), have been used to study their interactions with B7-1 and B7- 2, with CTLA4Ig binding B7-1 more strongly than CD28Ig (approximately 20-fold higher avidity). We have now, by site-specific and homologue mutagenesis, identified regions in CTLA4Ig important for strong binding to B7-1. A hexapeptide motif (MYPPPY) in the complementarity determining region 3 (CDR3)-like region is fully conserved in all CD28 and CTLA-4 family members. Alanine scanning mutagenesis through the motif in CTLA4Ig and at selected residues in CD28Ig reduced or abolished binding to B7-1. Chimeric molecules HS4, HS4-A, and HS4-B were constructed in which CDR3-like regions of CTLA-4, COOH-terminally extended to include nonconserved residues, were grafted onto CD28Ig. These homologue mutants showed stronger binding to B7-1 than did CD28Ig. Grafting of the CDR1-like region of CTLA-4, which is not conserved in CD28 and is predicted to be spatially adjacent to CDR3, into HS4 and HS4-A, resulted in chimeric molecules (HS7 and HS8) which bound B7-1 even better. Inclusion of the CDR2-like domain of CTLA-4 into HS7 and HS8 did not further increase binding. Thus, the MYPPPY motifs of CTLA4Ig and CD28Ig are important for their binding to B7-1, but the increased strength of this binding by CTLA4Ig is mediated by nonconserved residues in the CDR1- and CDR3-analogous regions.