Peptide and beta 2-microglobulin regulation of cell surface MHC class I conformation and expression.
Peptide and beta 2-microglobulin regulation of cell surface MHC class I conformation and expression.
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DOI：
10.4049/jimmunol.148.12.3723
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发表时间：
1992-06
影响因子：
4.4
通讯作者：
Gillis R. Otten;E. Bikoff;R. Ribaudo;Steven Kozlowski;David H. Margulies;Ronald N. Germain
中科院分区：
文献类型：
--
作者：
Gillis R. Otten;E. Bikoff;R. Ribaudo;Steven Kozlowski;David H. Margulies;Ronald N. Germain
我们研究了肽和β 2-微球蛋白（β 2m）在调节细胞表面I类分子的构象和表达水平中的作用。利用一种合成H- 2dd H链和小鼠β 2m但内源性肽负载缺陷的细胞系，我们证明了外源肽或β 2m单独在25℃和37℃下增加表面H- 2dd表达的能力。肽和β 2m在增加表面I类表达的能力方面显示出明显的协同作用，在缺乏游离β 2m的情况下，肽促进的增加很小。低温诱导的分子在37℃的培养过程中，β 2m和α 1/ α 2结构域构象表位的丢失速率难以区分。然而，α 3表位的丢失速率要慢得多，表明细胞表面的I类丢失至少有两个步骤：1)β 2m与H链结合的丢失和α 1/ α 2区域的展开；2)具有α 3表位的自由H链的变性、降解或内化。这些数据首次表明，自由H链在膜上以一种能够在加入β 2m和肽后重新折叠成α 1/ α 2表位阳性分子的形式存活有限时间。这种在β 2m和肽存在下的重折叠可以解释在i类依赖性CTL裂解中致敏细胞对这两种成分的需求。这也表明I类分子的这种构象变化并不严格依赖于新合成的H链或细胞内的伴侣。细胞表面H链-肽- β 2m相互作用的研究可能与理解细胞内肽装载事件有关。
We have examined the roles of peptide and beta 2-microglobulin (beta 2m) in regulating the conformation and expression level of class I molecules on the cell surface. Using a cell line synthesizing H-2Dd H chain and mouse beta 2m but defective in endogenous peptide loading, we demonstrate the ability of either exogenous peptide or beta 2m alone to increase surface H-2Dd expression at both 25 degrees C and 37 degrees C. Peptide and beta 2m show marked synergy in their abilities to increase surface class I expression, with minimal increases promoted by peptide in the absence of free beta 2m. Low temperature-induced molecules have indistinguishable rates of loss of beta 2m and alpha 1/alpha 2 domain conformational epitopes during culture at 37 degrees C. However, the rate of alpha 3 epitope loss is much slower, indicating a minimum of two steps in class I loss from the cell surface: 1) loss of beta 2m binding to H chain and unfolding of the alpha 1/alpha 2 region; then 2) denaturation, degradation, or internalization of the free H chains possessing alpha 3 epitopes. These data show for the first time that free H chains survive for a finite time on the membrane in a form capable of refolding into alpha 1/alpha 2 epitope positive molecules upon addition of beta 2m and peptide. This refolding in the presence of beta 2m and peptide can explain the reported requirement for both components in sensitizing cells for class I-dependent CTL lysis. It also indicates that such conformational changes in class I molecules are not strictly dependent on either newly synthesized H chains or on intracellular chaperons. The study of H chain-peptide-beta 2m interaction on the cell surface may be relevant to understanding intracellular peptide loading events.