Yin Shaoman, Fan Xingjun, Yu Shuiliang, Li Chaoyang, Sy Man-Sun
Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44120.
Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44120.
J Biol Chem. 2008 Sep 12;283(37):25446-25454. doi: 10.1074/jbc.M800814200. Epub 2008 Jul 11.
Recombinant prion protein, rPrP, binds DNA. Both the KKRPK motif and the octapeptide repeat region of rPrP are essential for maximal binding. rPrP with pathogenic insertional mutations binds more DNA than wild-type rPrP. DNA promotes the aggregation of rPrP and protects its N terminus from proteinase K digestion. When rPrP is mixed with an expression plasmid and Ca(2+), the rPrP.DNA complex is taken up by mammalian cells leading to gene expression. In the presence of Ca(2+), rPrP by itself is also taken up by cells in a temperature- and pinocytosis-dependent manner. Cells do not take up rPrP(DeltaKKRPK), which lacks the KKRPK motif. Thus, rPrP is the carrier for DNA and the KKRPK motif is essential for its uptake. When mixed with DNA, a pentapeptide KKRPK, but not KKKKK, is sufficient for DNA internalization and expression. In contrast, whereas the normal cellular prion protein, PrP(C), on the cell surface can also internalize DNA, the imported DNA is not expressed. These findings may have relevance to the normal functions of PrP(C) and the pathogenic mechanisms of human prion disease.
重组朊病毒蛋白（rPrP）能结合DNA。rPrP的KKRPK基序和八肽重复区域对于最大程度的结合至关重要。带有致病性插入突变的rPrP比野生型rPrP结合更多的DNA。DNA促进rPrP的聚集，并保护其N端免受蛋白酶K的消化。当rPrP与表达质粒和Ca(2+)混合时，rPrP-DNA复合物被哺乳动物细胞摄取，从而导致基因表达。在Ca(2+)存在的情况下，rPrP自身也以温度和胞吞作用依赖的方式被细胞摄取。细胞不摄取缺乏KKRPK基序的rPrP(DeltaKKRPK)。因此，rPrP是DNA的载体，而KKRPK基序对于其摄取至关重要。当与DNA混合时，五肽KKRPK而非KKKKK足以实现DNA的内化和表达。相比之下，尽管细胞表面的正常细胞朊病毒蛋白PrP(C)也能内化DNA，但导入的DNA并不表达。这些发现可能与PrP(C)的正常功能以及人类朊病毒病的致病机制有关。
