Bauer A, Hüttinger R, Staffler G, Hansmann C, Schmidt W, Majdic O, Knapp W, Stockinger H
Institute of Immunology, Vienna International Research Cooperation Center, University of Vienna, Austria.
Eur J Immunol. 1997 Jun;27(6):1366-73. doi: 10.1002/eji.1830270611.
Human CD1 form a group of nonpolymorphic leukocyte surface molecules with homology to major histocompatibility complex (MHC) proteins. Recent findings in human and in mouse demonstrate the capacity of CD1 molecules to present nonpeptide components like lipids or lipoglycans as well as peptides. We studied the involvement of beta 2-microglobulin (beta 2m) in expression of the classic human CD1 proteins CD1a, CD1b, and CD1c. The beta 2m-deficient human melanoma cell line FO-1 was transiently transfected with either CD1a, CD1b, or CD1c DNA alone, or in combination with beta 2m using the adenovirus-enhanced receptor-mediated transfer infection system. Only co-transfection of FO-1 cells with CD1+ beta 2m resulted in the detection of CD1 Ag by monoclonal antibodies (mAb). This indicated that CD1 mAb recognized determinants are dependent on beta 2m and raised the question whether beta 2m-free forms of CD1 can be expressed. Therefore, to visualize CD1 molecule expression independently of beta 2m, we expressed tagged recombinant forms. A full-length CD1b construct tagged at the very C terminus with a small peptide was transported to the plasma membrane only when beta 2m was co-transfected. beta 2m involvement in the transport of CD1 was confirmed by expression of soluble forms of CD1a, CD1b, and CD1c in three different cell types. Analogous to tagged full-length CD1b, secretion of the soluble CD1 constructs was strictly dependent on beta 2m. The soluble CD1 chimeras were secreted as complexes with endogenous beta 2m. Thus, similar to its role for MHC class I expression, beta 2m is essential for processing and surface transport of the classic human CD1 molecules CD1a, CD1b, and CD1c.
人类CD1是一组非多态性白细胞表面分子，与主要组织相容性复合体（MHC）蛋白具有同源性。最近在人类和小鼠中的研究结果表明，CD1分子能够呈递脂质或脂多糖等非肽成分以及肽段。我们研究了β2-微球蛋白（β2m）在经典人类CD1蛋白CD1a、CD1b和CD1c表达中的作用。使用腺病毒增强的受体介导的转染感染系统，将β2m缺陷的人类黑色素瘤细胞系FO-1单独用CD1a、CD1b或CD1c DNA转染，或与β2m联合转染。只有FO-1细胞与CD1 + β2m共转染才能通过单克隆抗体（mAb）检测到CD1抗原。这表明CD1 mAb识别的决定簇依赖于β2m，并提出了是否可以表达无β2m形式的CD1的问题。因此，为了独立于β2m可视化CD1分子的表达，我们表达了带标签的重组形式。只有当β2m共转染时，在C末端用小肽标记的全长CD1b构建体才会转运到质膜。通过在三种不同细胞类型中表达可溶性形式的CD1a、CD1b和CD1c，证实了β2m参与CD1的转运。与带标签的全长CD1b类似，可溶性CD1构建体的分泌严格依赖于β2m。可溶性CD1嵌合体作为与内源性β2m的复合物分泌。因此，与它在MHC I类表达中的作用类似，β2m对于经典人类CD1分子CD1a、CD1b和CD1c的加工和表面转运至关重要。
