Neurobiology Sector, Laboratory of Prion Biology, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.
Prion. 2012 Jul 1;6(3):309-16. doi: 10.4161/pri.20026.
Doppel (Dpl) protein is a paralog of the prion protein (PrP) that shares 25% sequence similarity with the C-terminus of PrP, a common N-glycosylation site and a C-terminal signal peptide for attachment of a glycosylphophatidyl inositol anchor. Whereas PrP (C) is highly expressed in the central nervous system (CNS), Dpl is detected mostly in testes and its ectopic expression in the CNS leads to ataxia as well as Purkinje and granule cell degeneration in the cerebellum. The mechanism through which Dpl induces neurotoxicity is still debated. In the present work, primary neuronal cultures derived from postnatal cerebellar granule cells of wild-type and PrP-knockout FVB mice were used in order to investigate the molecular events that occur upon exposure to Dpl. Treatment of cultured cerebellar neurons with recombinant Dpl produced apoptosis that could be prevented by PrP co-incubation. When primary neuronal cultures from Bax-deficient mice were incubated with Dpl, no apoptosis was observed, suggesting an important role of Bax in triggering neurodegeneration. Similarly, cell survival increased when recDpl-treated cells were incubated with an inhibitor of caspase-3, which mediates apoptosis in mammalian cells. Together, our findings raise the possibility that Bax and caspase-3 feature in Dpl-mediated apoptosis.
双效蛋白（Dpl）是朊病毒蛋白（PrP）的一种平行物，与 PrP 的 C 端有 25%的序列相似性，具有共同的 N-糖基化位点和 C 末端信号肽，用于连接糖基磷脂酰肌醇锚。虽然 PrP（C）在中枢神经系统（CNS）中高度表达，但 Dpl 主要在睾丸中检测到，其在 CNS 中的异位表达会导致共济失调以及小脑浦肯野细胞和颗粒细胞变性。Dpl 诱导神经毒性的机制仍存在争议。在本工作中，使用源自野生型和 PrP 敲除 FVB 小鼠出生后小脑颗粒细胞的原代神经元培养物，以研究暴露于 Dpl 时发生的分子事件。用重组 Dpl 处理培养的小脑神经元会产生细胞凋亡，而与 PrP 共孵育可预防这种凋亡。当用 Dpl 孵育 Bax 缺陷型小鼠的原代神经元培养物时，未观察到细胞凋亡，表明 Bax 在引发神经退行性变中起重要作用。同样，当用 caspase-3 的抑制剂孵育经 recDpl 处理的细胞时，细胞存活率增加，caspase-3 在哺乳动物细胞中介导细胞凋亡。总之，我们的发现表明 Bax 和 caspase-3 可能参与了 Dpl 介导的细胞凋亡。
