Anti-apoptotic properties of physiological and elevated levels of the cellular prion protein (PrPc) under stress conditions are well documented. Yet, detrimental effects of elevated PrPc levels under stress conditions, such as exposure to staurosporine (STS) have also been described. In the present study, we focused on discerning early apoptotic STS-induced proteome and phospho-proteome changes in SH-SY5Y human neuroblastoma cells stably transfected either with an empty or PRNP-containing vector, expressing physiological or supraphysiological levels of PrPc, respectively. PrPc-overexpression per se appears to stress the cells under STS-free conditions as indicated by diminished cell viability of PrPc-overexpressing versus control cells. However, PrPc-overexpression becomes advantageous following exposure to STS. Thus, only a short exposure (2 h) to 1 μM STS results in lower survival rates and significantly higher caspase-3 activity in control versus PrPc-overexpressing cells. Hence, by exposing both experimental groups to the same apoptotic conditions we were able to induce apoptosis in control, but not in PrPc-overexpressing cells (as assessed by caspase-3 activity), which allowed for filtering out proteins possibly contributing to protection against STS-induced apoptosis in PrPc-overexpressing cells. Among other proteins regulated by different PrPc levels following exposure to STS, those involved in maintenance of cytoskeleton integrity caught our attention. In particular, the finding that elevated PrPc levels significantly reduce profilin-1 (PFN-1) expression. PFN-1 is known to facilitate STS-induced apoptosis. Silencing of PFN-1 expression by siRNA significantly increased viability of PrPc-overexpressing versus control cells, under STS treatment. In addition, PrPc-overexpressing cells depleted of PFN-1 exhibited increased viability versus PrPc-overexpressing cells with preserved PFN-1 expression, both subjected to STS. Concomitant increase in caspase-3 activity was observed in control versus PrPc-overexpressing cells after treatment with siRNA- PFN-1 and STS. We suggest that reduction of PFN-1 expression by elevated levels of PrPc may contribute to protective effects PrPc-overexpressing SH-SY5Y cells confer against STS-induced apoptosis.

译文

:在应激条件下,生理抗性和细胞病毒蛋白(PrPc)水平升高的抗凋亡特性已得到充分证明。然而,还已经描述了在应激条件下升高的PrPc水平的有害作用,例如暴露于星形孢菌素(STS)。在本研究中,我们专注于识别早期凋亡STS诱导的蛋白质组和磷酸化蛋白质组的变化,分别用空载体或含PRNP的载体稳定转染的SH-SY5Y人成神经细胞瘤细胞表达生理或超生理学水平的PrPc。 PrPc过度表达本身似乎在无STS的条件下对细胞造成压力,这由PrPc过度表达与对照细胞的细胞活力降低所表明。但是,PrPc过表达在暴露于STS后变得有利。因此,与过表达PrPc的细胞相比,仅短暂暴露(2 h)1μMSTS会导致较低的存活率和显着较高的caspase-3活性。因此,通过将两个实验组置于相同的凋亡条件下,我们能够在对照中诱导凋亡,但不能在过表达PrPc的细胞中诱导凋亡(通过caspase-3活性评估),从而可以滤除可能有助于抵抗STS的蛋白质诱导的PrPc过表达细胞凋亡。在暴露于STS后受不同PrPc水平调节的其他蛋白质中,涉及维持细胞骨架完整性的蛋白质引起了我们的注意。特别是,发现PrPc水平升高会大大降低profilin-1(PFN-1)的表达。已知PFN-1促进STS诱导的细胞凋亡。在STS处理下,通过siRNA沉默PFN-1表达可显着增加过表达PrPc的细胞与对照细胞的生存力。另外,与均保留了PFN-1表达的PrPc过表达细胞相比,均被STS处理的细胞中,耗尽了PFN-1的PrPc过表达细胞表现出增加的生存力。在用siRNA-PFN-1和STS处理后,在对照组中与过表达PrPc的细胞中同时观察到caspase-3活性的增加。我们建议,通过升高水平的PrPc降低PFN-1表达可能有助于过表达PrPc的SH-SY5Y细胞赋予抗STS诱导的细胞凋亡的保护作用。

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