Increased autophagy reduces endoplasmic reticulum stress after neonatal hypoxia-ischemia: Role of protein synthesis and autophagic pathways
Increased autophagy reduces endoplasmic reticulum stress after neonatal hypoxia-ischemia: Role of protein synthesis and autophagic pathways
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DOI：
10.1016/j.expneurol.2014.03.002
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发表时间：
2014-05-01
影响因子：
5.3
通讯作者：
Balduini, Walter
中科院分区：
文献类型：
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作者：
Carloni, Silvia;Albertini, Maria Cristina;Balduini, Walter
内质网（ER）应激可由扰乱ER稳态的几种病理条件引起，其特征在于未折叠蛋白质在ER腔中的积累。为了科普ER应激，细胞激活未折叠蛋白反应（UPR），这是一种旨在恢复稳态的蛋白质质量控制机制。本研究旨在探讨新生儿缺氧/缺血（HI）后UPR及其与自噬的相互作用。HI后GRP 78和Hsp 70表达、eIF 2 α磷酸化、Xbp-1 mRNA剪接和CHOP表达显著增加，显示严重的ER应激和UPR。用雷帕霉素（Rap）增加自噬显著降低了UPR。Rap没有进一步增加HI诱导的eIF 2 α磷酸化和p70 S6激酶（p70 S6 K）失活。然而，自噬激活后，单丹尸胺（MDC）阳性自噬体样结构和核糖体蛋白S6（RPS 6）之间存在明确的共定位，表明自噬体中存在核糖体（ribophagy）。我们发现Rap治疗后给予自噬抑制剂3-甲基腺嘌呤完全逆转了eIF 2 α磷酸化的增加和p70 S6 K的失活，并阻断了自噬体样结构的形成，恢复了UPR。自噬的过度激活显著降低了这种反应，突出了ER和自噬机制之间的相互作用在这种重要的病理条件下的相关性。此外，自噬体样结构中核糖体亚基的存在表明，通过自噬增加的核糖体周转（ribophagy）可能是自噬过度激活后观察到的神经保护作用中涉及的另一种机制。(c)2014爱思唯尔公司All rights reserved.
The endoplasmic reticulum (ER) stress can result from several pathological conditions that perturb ER homeostasis and is characterized by accumulation of unfolded proteins in the ER lumen. To cope with ER stress, cells activate the unfolded protein response (UPR), a protein quality control mechanism aimed at restoring homeostasis. The present study was undertaken to characterize the UPR after neonatal hypoxia/ischemia (HI) and its crosstalk with autophagy. After HI, there was a significant increase of GRP78 and Hsp70 expression, phosphorylation of eIF2 alpha, Xbp-1 mRNA splicing and CHOP expression, revealing severe ER stress and UPR. Increasing autophagy with rapamycin (Rap) significantly reduced the UPR. Rap did not further increase the eIF2 alpha phosphorylation and p70S6 kinase (p70S6K) inactivation induced by HI. After autophagy activation, however, there was a clear co-localization between monodansylcadaverine (MDC)-positive autophagosome-like structures and the ribosomal protein S6 (RPS6), indicating the presence of ribosomes in autophagosomes (ribophagy). We found that the autophagy inhibitor 3-methyladenine administered after Rap treatment completely reverted the increased phosphorylation of eIF2 alpha and p70S6K inactivation, and blocked the formation of autophagosome-like structures restoring the UPR.These results demonstrate that the UPR is strongly activated after neonatal HI. Over-activation of autophagy significantly reduces this response, highlighting the relevance of the cross-talk between ER and the autophagy machinery in this important pathological condition. Furthermore, the presence of ribosome subunits in autophagosome-like structures suggests that increased ribosome turnover through autophagy (ribophagy) may represent an additional mechanism involved in the neuroprotective effect observed after autophagy over-activation. (c) 2014 Elsevier Inc. All rights reserved.