Horváth G, Serru V, Clay D, Billard M, Boucheix C, Rubinstein E
INSERM U268, Hôpital Paul Brousse, 94807 Villejuif Cedex, France.
J Biol Chem. 1998 Nov 13;273(46):30537-43. doi: 10.1074/jbc.273.46.30537.
The CD19-CD21-CD81 complex regulates signal transduction events critical for B lymphocyte development and humoral immunity. CD81, a molecule with 4 transmembrane domains, member of the tetraspan superfamily, is engaged, together with other tetraspans such as CD9, CD53, CD63, and CD82, in multimolecular complexes containing beta1 integrins and major histocompatibility complex antigens. Here we demonstrate that two other tetraspans, CD82 and the early B cell marker CD9, are coimmunoprecipitated with CD19 from Brij97 lysates of B cell lines. Moreover, CD9 was coprecipitated from lysates of purified CD10(+) early B cells. These associations were confirmed by the cocapping of CD19 with CD9 or CD82. The CD9/CD19 association was disrupted in the presence of digitonin, contrary to the CD81/CD19 association, indicating that CD9 and CD81 interact with CD19 in different ways. The CD9/CD81 association is also disrupted in the presence of digitonin, suggesting that CD9 associates with CD19 only through CD81. To characterize the regions involved in the CD81/CD19 association, two reciprocal CD9/CD81 chimeric molecules were tested for the association with CD19, but none of them could be coprecipitated with CD19 in digitonin, indicating that the domain of CD81 responsible for its association with CD19 is complex. Finally, engagement of CD9 could induce the tyrosine phosphorylation of different proteins, including CD19 itself, suggesting that the CD9/CD19 association is functionally relevant. Thus, a physical and functional link is formed between the CD19-CD21-CD81 complex and the integrin-tetraspan complexes, which is dynamically modulated in the process of B cell differentiation.
CD19 - CD21 - CD81复合物调节对B淋巴细胞发育和体液免疫至关重要的信号转导事件。CD81是一种具有4个跨膜结构域的分子，属于四跨膜超家族成员，它与其他四跨膜蛋白如CD9、CD53、CD63和CD82一起，参与含有β1整合素和主要组织相容性复合体抗原的多分子复合物的形成。在此我们证明，另外两种四跨膜蛋白CD82和早期B细胞标志物CD9，可从B细胞系的Brij97裂解物中与CD19共同免疫沉淀。此外，从纯化的CD10(+)早期B细胞裂解物中也能共沉淀出CD9。这些相互作用通过CD19与CD9或CD82的共帽作用得到证实。与CD81/CD19相互作用不同，在存在洋地黄皂苷的情况下，CD9/CD19相互作用被破坏，这表明CD9和CD81以不同方式与CD19相互作用。在存在洋地黄皂苷的情况下，CD9/CD81相互作用也被破坏，这表明CD9仅通过CD81与CD19结合。为了表征参与CD81/CD19相互作用的区域，测试了两种相互的CD9/CD81嵌合分子与CD19的相互作用，但在洋地黄皂苷存在的情况下，它们均不能与CD19共沉淀，这表明负责CD81与CD19结合的结构域很复杂。最后，CD9的结合可诱导包括CD19自身在内的不同蛋白质的酪氨酸磷酸化，这表明CD9/CD19相互作用在功能上是相关的。因此，在CD19 - CD21 - CD81复合物与整合素 - 四跨膜复合物之间形成了一种物理和功能联系，这种联系在B细胞分化过程中受到动态调节。
