Haidl I D, Ng D H, Rothenberger S, Johnson P, Jefferies W A
Biotechnology Laboratory, University of British Columbia, Vancouver, Canada.
Eur J Immunol. 1995 Dec;25(12):3370-4. doi: 10.1002/eji.1830251225.
CD45 is a cell surface transmembrane tyrosine phosphatase. It is expressed as distinct protein isoforms via alternative splicing of exons 4, 5 and 6. In T and B lymphocytes, CD45 is thought to play a critical role in antigen-dependent signaling through their respective antigen receptor complexes. However, the isoform expression and enzymatic activity of CD45 in other leukocytes remains largely unknown. Here, we examine the isoform expression and phosphatase activity of CD45 in murine dendritic cells (DC). Flow cytometric double-labeling analysis and biochemical analysis of purified splenic DC CD45 demonstrate that DC express both the CD45RB and CD45R0 isoforms. Flow cytometric analyses of freshly isolated splenic DC and thymic DC also indicate the expression of CD45RB and CD45R0 on these DC populations. In addition, we find that purified splenic DC CD45 possesses a high level of intrinsic tyrosine phosphatase activity. These data therefore establish the restricted isoform expression pattern of CD45 in murine DC and demonstrate that cells lacking specific antigen receptor complexes have active tyrosine phosphatase activity associated with CD45.
CD45是一种细胞表面跨膜酪氨酸磷酸酶。它通过外显子4、5和6的可变剪接表达为不同的蛋白质异构体。在T淋巴细胞和B淋巴细胞中，CD45被认为在通过各自的抗原受体复合物进行的抗原依赖性信号传导中起关键作用。然而，CD45在其他白细胞中的异构体表达和酶活性在很大程度上仍不清楚。在这里，我们研究了CD45在小鼠树突状细胞（DC）中的异构体表达和磷酸酶活性。对纯化的脾脏DC CD45进行流式细胞术双标记分析和生化分析表明，DC表达CD45RB和CD45R0异构体。对新鲜分离的脾脏DC和胸腺DC进行的流式细胞术分析也表明，这些DC群体上表达CD45RB和CD45R0。此外，我们发现纯化的脾脏DC CD45具有高水平的内在酪氨酸磷酸酶活性。因此，这些数据确定了CD45在小鼠DC中的受限异构体表达模式，并表明缺乏特异性抗原受体复合物的细胞具有与CD45相关的活性酪氨酸磷酸酶活性。
