Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, United States.
Chem Biol Interact. 2013 Jul 5;204(2):116-24. doi: 10.1016/j.cbi.2013.04.016. Epub 2013 May 14.
Dysfunction of protein handling has been implicated in many neurodegenerative diseases and inhibition of the ubiquitin-proteasome system (UPS) has been linked to the formation of protein aggregates and proteinopathies in such diseases. While proteasomal inhibition could trigger an array of downstream protein handling changes including up-regulation of heat shock proteins (HSPs), induction of molecular chaperones, activation of the ER stress/unfolded protein response (UPR), autophagy and aggresome formation, little is known of the relationship of proteasomal inhibition to the sequence of activation of these diverse protein handling systems. In this study we utilized the reversible proteasome inhibitor MG132 and examined the activity of several major protein handling systems in the immortalized dopaminergic neuronal N27 cell line. In the early phase (up to 6h after proteasomal inhibition), MG132 induced time-dependent proteasomal inhibition which resulted in stimulation of the UPR, increased autophagic flux and stimulated heat shock protein response as determined by increased levels of phosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2α), C/EBP homologous protein (CHOP)/GADD153, turnover of autophagy related microtubule-associated protein 1 light chain 3 (LC3) and increased levels of Hsp70 respectively. After prolonged proteasomal inhibition induced by MG132, we observed the formation of vimentin-caged aggresome-like inclusion bodies. A recovery study after MG132-induced proteasomal inhibition indicated that the autophagy-lysosomal pathway participated in the clearance of aggresomes. Our data characterizes the relationship between proteasome inhibition and activation of other protein handling systems. These data also indicated that the induction of alternate protein handling systems and their temporal relationships may be important factors that determine the extent of accumulation of misfolded proteins in cells as a result of proteasome inhibition.
蛋白质处理功能障碍与许多神经退行性疾病有关,而泛素-蛋白酶体系统 (UPS) 的抑制与这些疾病中的蛋白质聚集和蛋白质病的形成有关。虽然蛋白酶体抑制可能会引发一系列下游蛋白质处理变化,包括热休克蛋白 (HSPs) 的上调、分子伴侣的诱导、内质网应激/未折叠蛋白反应 (UPR) 的激活、自噬和聚集体形成,但蛋白酶体抑制与这些不同蛋白质处理系统的激活顺序之间的关系知之甚少。在这项研究中,我们利用可逆蛋白酶体抑制剂 MG132 检查了几种主要蛋白质处理系统在永生化多巴胺能神经元 N27 细胞系中的活性。在早期阶段(蛋白酶体抑制后长达 6 小时),MG132 诱导时间依赖性蛋白酶体抑制,导致 UPR 激活、自噬通量增加,并通过增加真核翻译起始因子 2 alpha (eIF2α)、C/EBP 同源蛋白 (CHOP)/GADD153 的磷酸化水平、自噬相关微管相关蛋白 1 轻链 3 (LC3) 的周转和 Hsp70 水平的增加来刺激热休克蛋白反应。在 MG132 诱导的蛋白酶体抑制延长后,我们观察到波形蛋白笼状聚集体样包含体的形成。MG132 诱导的蛋白酶体抑制后的恢复研究表明,自噬溶酶体途径参与了聚集体的清除。我们的数据描述了蛋白酶体抑制与其他蛋白质处理系统激活之间的关系。这些数据还表明,替代蛋白质处理系统的诱导及其时间关系可能是决定蛋白酶体抑制导致细胞中错误折叠蛋白质积累程度的重要因素。