Association of SWAP-70 with the B cell antigen receptor complex

SWAP-70 is a component of an enzyme complex that recombines Ig switch regions in vitro. We report here the cloning of the human cDNA and its B lymphocyte-specific expression. Although its sequence contains three nuclear localization signals, in small resting B cells, SWAP-70 is mainly found in the cytoplasm. On stimulation, SWAP-70 translocates to the nucleus. In activated, class-switching B cell cultures, it is associated with membrane IgG, but not IgM. The membrane Ig association requires a functional pleckstrin homology domain and is controlled by the C terminus. We suggest that SWAP-70 is involved not only in nuclear events but also in signaling in B cell activation.

SWAP-70是可在体外介导免疫球蛋白（Ig）转换区重组的酶复合物的组分之一。本研究报道了人类SWAP-70编码互补DNA（cDNA）的克隆工作，以及该基因的B淋巴细胞特异性表达特征。尽管其氨基酸序列含有三个核定位信号，但在静息小B细胞中，SWAP-70主要定位于细胞质内。经活化刺激后，SWAP-70可发生核转位。在发生类别转换的活化B细胞培养体系中，SWAP-70可与膜型免疫球蛋白G（IgG）结合，但不与免疫球蛋白M（IgM）结合。该膜型免疫球蛋白结合活性依赖于具有功能活性的普列克底物蛋白同源（pleckstrin homology, PH）结构域，并受其C端区域调控。本研究提示，SWAP-70不仅参与细胞核内的生物学过程，还在B细胞活化的信号转导通路中发挥作用。