Ohnishi Kazuo, Melchers Fritz
National Institute of Infectious Diseases, Department of Immunology, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
Nat Immunol. 2003 Sep;4(9):849-56. doi: 10.1038/ni959. Epub 2003 Aug 3.
The pre-B cell receptor (preBCR), composed of mu immunoglobulin (Ig) and surrogate light chains, signals large 'preB-II' cells to proliferate in the apparent absence of ligands or cooperating cells. We deleted the N-terminal, nonimmunoglobulin (nonlg) portion of lambda5, or mutated seven arginine residues in it to serine residues. PreBCRs with such mutant lambda5 proteins showed increased cell surface representation and a diminished rate of aggregation and internalization. Tyrosine phosphorylation of preBCR complexes containing mutant lambda5 proteins was abolished. These results indicate that the nonIg portion of lambda5, and the seven arginine residues in it, are needed for signal transduction, and that signaling could be cell autonomous. We propose two models to explain the apparently constitutive, ligand-independent signal-transducing capacity of the preBCR.
前B细胞受体（preBCR）由μ免疫球蛋白（Ig）和替代轻链组成，在明显缺乏配体或协同细胞的情况下，能使大型“前B-II”细胞增殖。我们删除了λ5的N端非免疫球蛋白（nonlg）部分，或将其中的七个精氨酸残基突变为丝氨酸残基。含有此类突变λ5蛋白的PreBCR在细胞表面的表达增加，聚集和内化速率降低。含有突变λ5蛋白的PreBCR复合物的酪氨酸磷酸化被消除。这些结果表明，λ5的非Ig部分及其七个精氨酸残基是信号转导所必需的，并且信号传导可能是细胞自主的。我们提出了两种模型来解释PreBCR明显的组成性、不依赖配体的信号转导能力。
