Ohnishi K, Takemori T
Department of Immunology, National Institute of Health, Tokyo, Japan.
J Biol Chem. 1994 Nov 11;269(45):28347-53.
We describe the molecular components, subunit assembly, and cell surface expression of mu-chain complexes in mu+kappa- pre-B cell lines as revealed by two-dimensional gel electrophoresis. The mu-chain complexes of these cell lines contain several previously unreported components, p42(6.4), p39(6.7), p18(8.6), and p14(7.0), in addition to lambda 5, VpreB1, VpreB3 (formerly named 8HS20), MB-1(Ig-alpha), and B29(Ig-beta). These new components are not detected in mu+kappa+ immature B cell lines. The mu-chain associates with lambda 5, VpreB3, and p56(5.0) at an early phase of assembly, preceding the association of other molecules. mu-Associated VpreB3 decreased during assembly as the association of VpreB1 became dominant, suggesting that the change in the ratio of these two VL-like surrogate light chains is involved in the mechanism of assembly. Lambda 5, VpreB1, p56(5.0), p32(5.0), p36(5.5), and p14(7.0) were shown to be expressed on the cell surface in association with mu-chain. The association of the other molecules with mu-chain is most likely restricted to the intracellular compartment. An interaction between VpreB1 and VpreB3 was also suggested. These findings might be important for understanding the function of mu-chain complexes in pre-B cells. A possible signaling mechanism of mu/surrogate light chain complexes is discussed.
我们通过二维凝胶电泳揭示了μ⁺κ⁻前B细胞系中μ链复合物的分子组成、亚基组装及细胞表面表达。这些细胞系的μ链复合物除了含有λ5、VpreB1、VpreB3（原名8HS20）、MB-1（Ig-α）和B29（Ig-β）外，还包含几个先前未报道的成分，即p42(6.4)、p39(6.7)、p18(8.6)和p14(7.0)。在μ⁺κ⁺未成熟B细胞系中未检测到这些新成分。在组装的早期阶段，μ链与λ5、VpreB3和p56(5.0)结合，先于其他分子的结合。随着VpreB1的结合占主导地位，组装过程中与μ相关的VpreB3减少，这表明这两种类VL替代轻链比例的变化参与了组装机制。已证明λ5、VpreB1、p56(5.0)、p32(5.0)、p36(5.5)和p14(7.0)与μ链一起在细胞表面表达。其他分子与μ链的结合很可能局限于细胞内区室。还提示了VpreB1和VpreB3之间存在相互作用。这些发现可能对理解前B细胞中μ链复合物的功能很重要。本文讨论了μ/替代轻链复合物可能的信号传导机制。
