Membrane-anchored β2-microglobtilin stabilizes a highly receptive state of MHC class I molecules
Membrane-anchored β2-microglobtilin stabilizes a highly receptive state of MHC class I molecules
复制标题
DOI：
10.4049/jimmunol.174.4.2116
复制
发表时间：
2005-02-15
影响因子：
4.4
通讯作者：
Gross, G
中科院分区：
文献类型：
--
作者：
Berko, D;Carmi, Y;Gross, G
CTL诱导疫苗引起的应答的大小与APC膜上形成的MHC I类（MHC-I）-肽复合物的密度相关。MHC-IL链β（2）-微球蛋白（β（2）m）控制复合物的稳定性。我们推断，将β（2）m基因转化为完整的膜蛋白应该对所得的MHC-I分子产生显著的稳定作用，并增强疫苗效力。在本研究中，我们表明，在小鼠RMA-S细胞中表达膜性人beta（2）m（hbeta（2）m）提高了MHC-I的热稳定性。RMA-S转染子以比亲本RMA-S低10（4）至10（6）倍的浓度结合外源肽，如通过复合物特异性Ab和通过T细胞活化所检测的。此外，转染细胞的MHC-I被外源肽饱和在1分钟内发生，而亲本细胞需要近似1小时。然而，在饱和时，被修饰的细胞结合的肽的水平仅高3至5倍。仅表达天然hbeta（2）m，对结合特征的影响很小。可溶性β（2）m对加速动力学没有影响，但转染子的动力学与亲本细胞在针对hbeta（2）m的Ab存在下的动力学平行。抗体抑制和免疫共沉淀分析表明，这两个持久的肽受体H链/β（2）m异源二聚体和快速异源二聚体形成通过横向扩散可能有助于稳定。在体内，负载肽的转染子在抑制肿瘤生长方面明显优于亲本细胞上级。我们的研究结果支持了变构机制在决定三元MHC-I复合物稳定性中的作用，并提出膜β（2）m作为CTL诱导的新支架。
The magnitude of response elicited by CTL-inducing vaccines correlates with the density of MHC class I (MHC-I)-peptide complexes formed on the APC membrane. The MHC-I L chain, beta(2)-microglobulin (beta(2)m), governs complex stability. We reasoned that genetically converting beta(2)m into an integral membrane protein should exert a marked stabilizing effect on the resulting MHC-I molecules and enhance vaccine efficacy. In the present study we show that, expression of membranal human beta(2)m (hbeta(2)m) in mouse RMA-S cells elevates MHC-I thermal stability. RMA-S transfectants bind an exogenous peptide at concentrations 10(4)- to 10(6)-fold lower than parental RMA-S, as detected by complex-specific Abs and by T cell activation. Moreover, saturation of the transfectants' MHC-I by exogenous peptide occurs within 1 min, as compared with similar to1 h required for parental cells. At saturation, however, level of peptide bound by modified cells is only 3- to 5-fold higher. Expression of native hbeta(2)m only,results in marginal effect on the binding profile. Soluble beta(2)m has no effect on the accelerated kinetics, but the kinetics of transfectants parallel that of parental cells in the presence of Abs to hbeta(2)m. Ab inhibition and coimmunoprecipitation analyses suggest that both prolonged persistence of peptide-receptive H chain/beta(2)m heterodimers and fast heterodimer formation via lateral diffusion may contribute to stabilization. In vivo, peptide-loaded transfectants are considerably superior to parental cells in suppressing tumor growth. Our findings support the role of an allosteric mechanism in determining ternary MHC-I complex stability and propose membranal beta(2)m as a novel scaffold for CTL induction.