Efficient cell surface expression of class II MHC molecules in the absence of associated invariant chain.
Efficient cell surface expression of class II MHC molecules in the absence of associated invariant chain.
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DOI：
10.1084/jem.164.5.1478
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发表时间：
1986-11-01
期刊：
影响因子：
--
通讯作者：
Germain RN
中科院分区：
文献类型：
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作者：
Miller J;Germain RN
II类（或Ia类）主要组织相容性复合物异二聚体的胞浆内形式与第三种糖蛋白相关，称为不变链（Ii）。这种特定的相互作用导致了Ii在Ia分子的组装、细胞内运输和/或膜插入中起必要作用的观点。为了直接验证这一假设，我们将编码小鼠II类α和β链的互补DNA克隆转染到不表达任何内源性Ii信使RNA（mRNA）的细胞（COS-7和BALB/c 3 T3细胞）中。DNA介导的基因转移后，显着的细胞表面表达Ia观察到在瞬时表达试验中使用COS- 7细胞和稳定表达系统使用BALB/c 3 T3细胞。此外，II类α和β mRNA的总水平在Ii-细胞（转染的BALB/c 3 T3）和Ii+细胞（B细胞杂交瘤）中相似，其表达几乎相同量的表面Ia，这表明Ia表达的效率在两种细胞类型中相等，因此不依赖于Ii。这些结果表明，Ii的生理作用是不是简单地介导Ia分子的膜表达，并需要考虑关于这个分子的真正功能的替代假设。
The intracytoplasmic forms of class II (or Ia) major histocompatibility complex heterodimers are associated with a third glycoprotein, termed the invariant chain (Ii). This specific interaction has led to the view that Ii plays a necessary role in the assembly, intracellular transport, and/or membrane insertion of Ia molecules. To test this hypothesis directly, we have transfected complementary DNA clones that encode murine class II alpha and beta chains into cells that do not express any endogenous Ii messenger RNA (mRNA) (COS-7 and BALB/c 3T3 cells). After DNA-mediated gene transfer, significant cell surface expression of Ia was observed in transient expression assays using COS- 7 cells and a stable expression system using BALB/c 3T3 cells. Furthermore, the total levels of class II alpha and beta mRNA were similar in Ii- cells (transfected BALB/c 3T3) and in Ii+ cells (B cell hybridoma) that expressed nearly identical amounts of surface Ia, suggesting that the efficiency of Ia expression was equivalent in the two cell types and, therefore, independent of Ii. These results indicate that the physiologic role for Ii is not simply to mediate membrane expression of Ia molecules, and that alternative hypotheses concerning the true function of this molecule need to be considered.