人朊蛋白不同N-糖基化修饰突变体的构建及其在哺乳动物细胞中表达

Construction and Expression of Various Human Prion Proteins Mutants with Modified N-glycosylation Sites in Mammalian Cells

构建并表达人朊蛋白N-糖基化修饰位点突变的真核表达载体,有助于进一步研究朊蛋白N-糖基化修饰的生物学功能。定点突变野生型人朊蛋白基因PRNP,将获得的突变体亚克隆至真核表达载体pcDNA3.1中,并在人宫颈癌细胞株HeLa中瞬时表达各种朊蛋白糖基化修饰位点突变体,利用免疫印迹和糖苷酶消化等糖蛋白分析方法鉴定表达产物的糖基化形式。经Western blot鉴定,野生型和突变型朊蛋白表达产物出现不同形式的泳动特征,分别出现特异性糖基化修饰的多个条带,单糖基化修饰的两条条带和无糖基化修饰的一条条带。经PNGase F糖苷酶消化,野生型和糖基化单点突变型表达产物均能被糖苷酶消化,其分子量下移,去糖基化突变型表达产物的分子条带位置不变。通过突变野生型人朊蛋白基因PRNP的N-糖基化修饰位点,获得单糖基化修饰和去N-糖基化修饰的6种人朊蛋白突变体,并能够在HeLa细胞株中瞬时表达单糖基化修饰和去N-糖基化修饰朊蛋白,为进一步研究朊蛋白的相关功能建立良好基础。

To study the biological function of the N-glycosylation modification of prion proteins （PrP）, various eukaryotic expression vectors for the mutants with N-glycosylation modification of human PrP had been constructed and expressed. With sitedirect mutation technique, human PRNP gene was mutated and the obtained mutants were suboloned into eukaryotic expressing plasmid pcDNA3.1 and transiently expressed in Hela cervical adenocarcinoma cell. The expression products of the mutated PrP were identified with Western blotting assay and the PNGase digestion assay. Several mutants with specific glycosylation modification were identified from the expressed products by Western blot, including two mutants with one glycosylation site mutated and one without any mutation at glycosylation sites. The expressed products were digested with PNGase F. The wild type proteins and those with one of glycosylation sites mutated were digested, resulting in their molecular weights reduced, while the molecular weights of products with mutations at both glycosylation sites were not changed. The mutant of wild type human PRNP gene at N-glycosylation modification sites and six modified mutants with mono- or non-N-glycosylation had been obtained successfully in the study. Moreover, the modified PrP with mono- and non-N-glycosylation were able to be expressed transitantly in Hela cells, which could be a useful means for studying prions.