人sBCMA cDNA的克隆、高可溶性融合表达及活性分析

BCMA是除TACI外BAFF和APRIL共用的另一细胞表面受体。为了研究sBCMA作为拮抗受体的可能及获得活性sBCMA蛋白用做结构功能研究,我们以RTPCR法从人B系非洲淋巴瘤细胞株Raji总RNA中扩增出人BCMA的全长cDNA,经克隆测序证实所克隆的基因为人BCMA。继而通过嵌套PCR扩增出胞外可溶区(sBCMA,46个氨基酸组成,含有一个6个半胱氨酸的保守CRD,构成3个二硫键)cDNA,构建原核表达载体pET43.1a( )sBCMA,在大肠杆菌菌株OrigamiB(DE3)pLysS中高可溶性融合表达出重组蛋白sBCMANusAHis6,同时克隆表达了融合蛋白NusAHis6。经Ni NTA亲和纯化后的目的蛋白进行细胞学实验表明sBCMA能特异阻断BAFF促小鼠B细胞的增殖作用,而NusAHis6则不能,证实我们所表达得到的受体胞外可溶性片段sBCMA与配体具有较高的结合活性。sBCMA融合蛋白的成功表达将为二硫键富含类蛋白的表达提供参考,并为研究其临床应用以及BAFF和APRIL受体结构和功能的关系奠定基础。

Cloning, Soluble Expression and Characterization of Human sBCMA

BCMA is one of the transmembrane receptors belonging to BAFF and APRIL. In order to identify the feasibility of sBCMA as decoy receptor and obtain active sBCMA for its structural and functional research, full length of hBCMA was amplified with total RNA from Raji cell line by RT-PCR, and the cDNA encoding the extracelluar soluble domain of hBCMA was inserted into pET43.1a( ) vector. The recombinant vector pET43.1a( )-sBCMA was transformed into E.coli Origami B(DE3) pLyS which is helpful for disulfide bond construction of expression proteins. After IPTG induction, the recombinant protein was expressed as soluble fusion protein, sBCMA-NusA-His_6, and identified by western blotting. Then the target protein was purified by Ni -chelating Sepharose Fast Flow. The binding activity between recombinant sBCMA and BAFF was detected by ELISA. Also, Recombinant sBCMA inhibited proliferation of mouse B cell stimulating by rhsBAFF. It was proved that recombinant sBCMA has good bioactivity and the method to express those proteins rich in disulfide bond is feasible and effectual.