Qin Kefeng, Ding Tianbing, Xiao Yi, Ma Wenyu, Wang Zhen, Gao Jimin, Zhao Lili
Zhejiang Provincial Key Laboratory for Technology and Application of Model Organisms, Wenzhou Medical University, Wenzhou, China ; Department of Microbiology, Fourth Military Medical University, Xi'an, China ; Department of Neurology, University of Chicago, Chicago, Illinois, United States of America.
PLoS One. 2013 Dec 10;8(12):e82130. doi: 10.1371/journal.pone.0082130. eCollection 2013.
Although structurally and biochemically similar to the cellular prion (PrP(C)), doppel (Dpl) is unique in its biological functions. There are no reports about any neurodegenerative diseases induced by Dpl. However the artificial expression of Dpl in the PrP-deficient mouse brain causes ataxia with Purkinje cell death. Abundant Dpl proteins have been found in testis and depletion of the Dpl gene (Prnd) causes male infertility. Therefore, we hypothesize different regulations of Prnd in the nerve and male productive systems. In this study, by electrophoretic mobility shift assays we have determined that two different sets of transcription factors are involved in regulation of the Prnd promoter in mouse neuronal N2a and GC-1 spermatogenic (spg) cells, i.e., upstream stimulatory factors (USF) in both cells, Brn-3 and Sp1 in GC-1 spg cells, and Sp3 in N2a cells, leading to the expression of Dpl in GC-1 spg but not in N2a cells. We have further defined that, in N2a cells, Dpl induces oxidative stress and apoptosis, which stimulate ataxia-telangiectasia mutated (ATM)-modulating bindings of transcription factors, p53 and p21, to Prnp promoter, resulting the PrP(C) elevation for counteraction of the Dpl cytotoxicity; in contrast, in GC-1 spg cells, phosphorylation of p21 and N-terminal truncated PrP may play roles in the control of Dpl-induced apoptosis, which may benefit the physiological function of Dpl in the male reproduction system.
尽管多配体蛋白（Dpl）在结构和生化性质上与细胞朊蛋白（PrP(C)）相似，但其生物学功能却独具特色。目前尚无关于Dpl引发任何神经退行性疾病的报道。然而，在PrP基因缺陷的小鼠大脑中人工表达Dpl会导致共济失调并伴有浦肯野细胞死亡。在睾丸中发现了大量的Dpl蛋白，而Dpl基因（Prnd）的缺失会导致雄性不育。因此，我们推测Prnd在神经和雄性生殖系统中存在不同的调控机制。在本研究中，通过电泳迁移率变动分析，我们确定了两组不同的转录因子参与了小鼠神经元N2a和GC-1生精（spg）细胞中Prnd启动子的调控，即在这两种细胞中都有上游刺激因子（USF），在GC-1 spg细胞中有Brn-3和Sp1，在N2a细胞中有Sp3，这导致Dpl在GC-1 spg细胞中表达而在N2a细胞中不表达。我们进一步明确，在N2a细胞中，Dpl诱导氧化应激和细胞凋亡，刺激共济失调毛细血管扩张症突变（ATM）调节转录因子p53和p21与Prnp启动子的结合，从而导致PrP(C)升高以对抗Dpl的细胞毒性；相反，在GC-1 spg细胞中，p21的磷酸化和N端截短的PrP可能在控制Dpl诱导的细胞凋亡中发挥作用，这可能有利于Dpl在雄性生殖系统中的生理功能。
