DM loss in k haplotype mice reveals isotype-specific chaperone requirements
DM loss in k haplotype mice reveals isotype-specific chaperone requirements
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DOI：
10.4049/jimmunol.170.7.3751
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发表时间：
2003-04-01
影响因子：
4.4
通讯作者：
Bikoff, EK
中科院分区：
文献类型：
--
作者：
Koonce, CH;Wutz, G;Bikoff, EK
DM 作为 II 类伴侣促进内吞区室内不同肽的捕获。迄今为止研究的DM突变细胞表达由II类相关的不变链衍生肽（CLIP）（不变链的短蛋白水解片段）结合的II类，并表现出有缺陷的肽加载能力。为了评估 k 单倍型小鼠的 DM 功能贡献，我们通过胚胎干细胞技术在 DMa 基因座设计了一种新的突变。本实验证明 A(k)/CLIP 复合物寿命较短，A(k) 表面表达减少，A(k) 肽结合活性增强。因此，我们得出结论，k 单倍型小鼠中的 DM 缺失产生了大量空的或松散占据的 Ak 构象异构体。另一方面，突变几乎不影响E-k活性。成熟紧凑的 E-k 二聚体的出现、接近正常的表面表达和高效的 Ag 呈递能力强化了同种型特异性 DM 需求的证据。与之前描述的 DM 突变体相反，野生型配体的部分占据足以消除抗自身反应性。质谱分析揭示了 A(k)/CLIP 以及与 E-k 分子结合的相对短肽的异质集合。这些实验表明，DM 具有不同的作用，具体取决于其特定的 II 类伙伴。
DM actions as a class II chaperone promote capture of diverse peptides inside the endocytic compartment(s). DM mutant cells studied to date express class II bound by class II-associated invariant chain-derived peptide (CLIP), a short proteolytic fragment of the invariant chain, and exhibit defective peptide-loading abilities. To evaluate DM functional contributions in k haplotype mice, we engineered a novel mutation at the DMa locus via embryonic stem cell technology. The present experiments demonstrate short-lived A(k)/CLIP complexes, decreased A(k) surface expression, and enhanced A(k) peptide binding activities. Thus, we conclude that DM loss in k haplotype mice creates a substantial pool of empty or loosely occupied Ak conformers. On the other hand, the mutation hardly affects E-k activities. The appearance of mature compact E-k dimers, near normal surface expression, and efficient Ag presentation capabilities strengthen the evidence for isotype-specific DM requirements. In contrast to DM mutants described previously, partial occupancy by wild-type ligands is sufficient to eliminate antiself reactivity. Mass spectrometry profiles reveal A(k)/CLIP and a heterogeneous collection of relatively short peptides bound to E-k molecules. These experiments demonstrate that DM has distinct roles depending on its specific class II partners.