猪I型补体受体与C3b活性片段相互结合的体外检测

【目的】检测猪红细胞类补体受体I型（Complement receptor 1-like,CR1-like）与C3b活性片段能否发生结合,以期为阐明猪红细胞发挥免疫粘附功能的分子机理提供科学数据。【方法】利用前期已构建的CR1-like_(3-6)、CR1-like_(8-11)功能域片段的重组质粒建立酵母双杂交检测体系,运用酵母共转化的方法将诱饵质粒（重组pGBKT7-CR1-like）与捕获质粒（重组pGADT7-C3b）共同转入Y2HGold酵母细胞中,分别利用一缺平板SD/-Leu、SD/-Trp和二缺平板SD/-Leu/-Trp（DDO）严格筛选共转化成功的酵母细胞,再根据报告因子是否表达来鉴别转化子在SD/-Leu/-Trp/X-α-Gal（DDO/X）、SD/-Leu/-Trp/X-α-Gal/Aba（DDO/X/A）二缺培养板上的生长情况,并结合菌落的颜色变化现象综合判定CR1-like活性片段与补体C3b在酵母细胞中是否发生相互结合;然后运用免疫沉淀技术分离酵母细胞中CR1-like与C3b结合复合物,并对该复合物的特异性进行Western blot鉴定。【结果】试验成功将pGBKT7-CR1-like与pGADT7-C3b基因共转入Y2HGold酵母细胞。共转化的酵母克隆在SD/-Leu、SD/-Trp、DDO平板上能够正常生长,在DDO/X、DDO/X/A平板上正常生长且菌落呈现蓝色,由此表明,试验中酵母双杂交系统建立成功,并通过试验获得了阳性酵母克隆。共同转化了pGBKT7-CR1-like和pGADT7-C3b质粒的酵母菌落PCR反向鉴定结果显示,在共转化的酵母菌中含有目的基因CR1-like_(3-6)和CR1-like_(8-11),共转化组的质粒酶切后出现C3b基因片段,与设计大小一致,说明重组质粒成功共转化入酵母细胞中。免疫沉淀试验中应用pGBKT7载体的标签抗体c-Myc沉淀酵母细胞中的融合蛋白,以c-Myc为一抗进行Western blot检测发现,单独转化了pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)的融合蛋白在50 kD处出现特异性条带;共转化pGBKT7-CR1-like_(3-6) + pGADT7-C3b和共转化pGBKT7-CR1-like_(8-11) + pGADT7-C3b的酵母融合蛋白在83 kD处出现特异性条带;以HA单克隆抗体为一抗进行Western blot检测时,在pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)融合蛋白中没有出现特异性条带,只有3、4泳道中共转化的酵母融合蛋白在83 kD处出现特异性条带,表明在Y2HGold酵母细胞中存在CR1-like与C3b识别结合的复合物。使用CR1-like单克隆抗体沉淀酵母细胞中的融合蛋白,以CR1-like单克隆抗体为一抗进行Western blot检测发现,单独转化了pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)的融合蛋白在50 kD处出现特异性条带;共转化pGBKT7-CR1-like_(3-6) + pGADT7-C3b和共转化pGBKT7-CR1-like_(8-11) + pGADT7-C3b的酵母融合蛋白在83 kD处出现特异性条带;以C3单克隆抗体为一抗进行Western blot检测发现,在pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)融合蛋白中没有出现特异性条带,泳道3、4所示只有共转化的酵母融合蛋白在83 kD处出现特异性条带,表明在Y2HGold酵母细胞中存在具有生物活性的CR1-like与C3b识别结合的复合物。通过多个单克隆抗体杂交结果,可看出诱饵质粒的表达产物CR1-like_(3-6)、CR1-like_(8-11)片段与捕获质粒的表达产物C3b片段可在酵母细胞内发生结合。【结论】猪红细胞CR1-like发挥免疫粘附功能的识别配体为C3b,为猪红细胞CR1-like功能域分子结构的进一步解析提供了重要数据依据。

Detection of Interaction Between Porcine Type I Complement Receptor and C3b Active Fragment in Vitro

【Objective】In order to provide scientific data for elucidating the molecular mechanism of porcine erythrocyte immune adhesion function, it was investigated whether CR1-like (Complement receptor 1-like, CR1-like) of porcine erythrocyte could bind to the C3b or not.【Method】In this study, the recombinant plasmids of CR1-like_(3-6) and CR1-like_(8-11) functional domain fragments were constructed first, which were used to establish a yeast two-hybrid detection system. The bait plasmid (recombinant pGBKT7-CR1-like) and capture plasmid (recombinant pGADT7-C3b) were co-transformed into Y2HGold yeast cells. The single deficient SD/-Leu, SD/-Trp and double-deficient SD/-Leu/-Trp (DDO) media were used to strictly screen the co-transformed yeast cells. Then, according to the expression of report factor, the growth of transformants were identified on the double-deficient medium SD/-Leu/-Trp/X-α-Gal (DDO/X) or SD/-Leu/-Trp/X-α-Gal/Aba (DDO/X/A) combined with the color change phenomenon of the colony to comprehensively determine whether CR1-like active fragments and complement C3b bind to each other in yeast cells or not. The CR1-like-C3b binding complex in yeast cells was then separated by immunoprecipitation, and the specificity of the complex was identified by Western blot. 【Result】The co-transformed yeast clones showed normal growth on SD/-Leu, SD/-Trp, DDO and DDO/X, DDO/X/A media with blue color colonies, and this indicated that positive yeast colonies were successfully obtained. The results of PCR reverse identification showed that the co-transformed yeast contained the target genes CR1-like_(3-6) and CR1-like_(8-11). The C3b gene fragment appeared after the plasmid was digested, indicating that the recombinant plasmid pGBKT7-CR1-like and pGADT7-C3b were successfully co-transformed into yeast cells. In the immunoprecipitation test, the tag antibody c-Myc of the pGBKT7 vector was used to precipitate the fusion protein in yeast cells. Western blot detection with c-Myc as the primary antibody revealed that the fusion protein transformed pGBKT7-CR1-like_(3-6) and pGBKT7-CR1-like_(8-11) separately showed a specific band at 50 kDa; the yeast fusion protein co-transformed with pGBKT7-CR1-like_(3-6) + pGADT7-C3b and pGBKT7-CR1-like_(8-11) + pGADT7-C3b showed a specific band at 83 kDa; when the HA monoclonal antibody was used as the primary antibody for Western blot detection, no specific bands appeared in the pGBKT7-CR1-like_(3-6) and pGBKT7-CR1-like_(8-11) fusion proteins, and only the yeast fusion protein co-transformed in lane 3 and 4 showed a specific band at 83 kD. It showed that there was a complex of CR1-like and C3b in Y2HGold yeast cells. Using CR1-like monoclonal antibody to precipitate the fusion protein in yeast cells, Western blot detection with CR1-like as the primary antibody revealed that the fusion protein transformed with pGBKT7-CR1-like_(3-6) and pGBKT7-CR1-like_(8-11) separately showed a specific band at 50 kD; the yeast fusion protein co-transformed with pGBKT7-CR1-like_(3-6) + pGADT7-C3b and pGBKT7-CR1-like_(8-11) + pGADT7-C3b showed a specific band at 83 kD; when the C3 monoclonal antibody was used as the primary antibody for Western blot detection, no specific bands appeared in the pGBKT7-CR1-like_(3-6) and pGBKT7-CR1-like_(8-11) fusion proteins, lanes 3 and 4 showed that only the co-transformed yeast fusion protein had a specific band at 83 kD. This indicated that there was a biologically active CR1-like and C3b binding complex in Y2HGold yeast cells. The bait plasmid expression products CR1-like_(3-6), CR1-like_(8-11) fragments and capture plasmid expression products C3b fragment could be combined in yeast cells.【Conclusion】In summary, the recognition ligand for porcine erythrocyte CR1-like to exert immune adhesion function was C3b, which provided an important data basis for the further analysis of the molecular structure of CR1-like functional domain.