B淋巴细胞信号转导相关接头蛋白Bam32与Hic-5的相互作用

32kDB淋巴细胞接头分子(Bam32)是调控B细胞抗原受体(Bcellantigenreceptor,BCR)信号转导通路的关键蛋白质分子之一.为了研究Bam32的功能及其作用机理,应用酵母双杂交技术筛选了能与Bam32相互作用的蛋白质分子.筛选发现1个呈强阳性反应的克隆,其基因编码Hic5,为paxillin蛋白家族成员之一.Paxillin是整合素(integrin)信号转导通路中的关键蛋白质分子,而整合素在细胞对细胞外基质分子的粘附、细胞运动等方面起了重要的作用,因此对Bam32与Hic5的相互作用进行了进一步研究.用293T细胞共转染和特异性免疫共沉淀法证实,Bam32可在哺乳动物细胞中与Hic5共沉淀,证明它们可以在细胞内相互作用.应用免疫共沉淀法和抗磷酸化酪氨酸抗体检测显示,激酶Lyn可导致Bam32和Hic5的磷酸化.这些研究结果提示,Bam32与Hic5的相互作用可能在激活下游分子的信号转导级联反应以及调节细胞的粘附和运动等功能中发挥了重要的作用.

Interaction of B lymphocyte Signal Transduction-Associated Adaptor Protein Bam32 with Hic-5

The B lymphocyte adaptor molecule of 32 kD(Bam 32) acts as conduicts to channel upstream signals into downstream effectors branches.To explore the role of Bam32 in B cell antigen receptor (BCR) signaling,an yeast two_hybrid screening the library from fetal mouse was performed to identify molecules that could interact with Bam32. One of the positive clones was found to encode Hic-5, a member of the paxillin protein family. It has been proved that paxillin plays a critical role in the signal transduction pathways of integrin, a receptor involving in many important functions such as adhesion of cell to extracellular matrix, cell movement etc. Through co-transfection of 293T cells with expression plasmids and immunoprecipitation, this study confirmed that Hic-5 could precipitate together with Bam32, suggesting their interaction inside mammalian cells. By using specific anti-phosphotyrosine antibody, it was found that both Bam32 and Hic-5 could be phosphorylated by Lyn, a protein tyrosine kinase. The results indicated that the interaction of Bam32 with Hic-5 might play an important role in activating downstream signaling molecules and in the regulation of cell adhesion and movement.