TFE3, a potential therapeutic target for Spinal Cord Injury via augmenting autophagy flux and alleviating ER stress

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Abstract

Background and Aim: Increasing evidence suggests that spinal cord injury (SCI)-induced defects in autophagic flux may contribute to an impaired ability for neurological repair following injury. Transcription factor E3 (TFE3) plays a crucial role in oxidative metabolism, lysosomal homeostasis, and autophagy induction. Here, we investigated the role of TFE3 in modulating autophagy following SCI and explored its impact on neurological recovery.

Methods: Histological analysis via HE, Nissl and Mason staining, survival rate analysis, and behavioral testing via BMS and footprint analysis were used to determine functional recovery after SCI. Quantitative real-time polymerase chain reaction, Western blotting, immunofluorescence, TUNEL staining, enzyme-linked immunosorbent assays, and immunoprecipitation were applied to examine levels of autophagy flux, ER-stress-induced apoptosis, oxidative stress, and AMPK related signaling pathways. In vitro studies using PC12 cells were performed to discern the relationship between ROS accumulation and autophagy flux blockade.

Results: Our results showed that in SCI, defects in autophagy flux contributes to ER stress, leading to neuronal death. Furthermore, SCI enhances the production of reactive oxygen species (ROS) that induce lysosomal dysfunction to impair autophagy flux. We also showed that TFE3 levels are inversely correlated with ROS levels, and increased TFE3 levels can lead to improved outcomes. Finally, we showed that activation of TFE3 after SCI is partly regulated by AMPK-mTOR and AMPK-SKP2-CARM1 signaling pathways.

Conclusions: TFE3 is an important regulator in ROS-mediated autophagy dysfunction following SCI, and TFE3 may serve as a promising target for developing treatments for SCI.

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Autophagy is activated for cell survival after endoplasmic reticulum stress.

Maiko OGATA, Shin-ichiro Hino, Atsushi Saito … (2006)

Eukaryotic cells deal with accumulation of unfolded proteins in the endoplasmic reticulum (ER) by the unfolded protein response, involving the induction of molecular chaperones, translational attenuation, and ER-associated degradation, to prevent cell death. Here, we found that the autophagy system is activated as a novel signaling pathway in response to ER stress. Treatment of SK-N-SH neuroblastoma cells with ER stressors markedly induced the formation of autophagosomes, which were recognized at the ultrastructural level. The formation of green fluorescent protein (GFP)-LC3-labeled structures (GFP-LC3 "dots"), representing autophagosomes, was extensively induced in cells exposed to ER stress with conversion from LC3-I to LC3-II. In IRE1-deficient cells or cells treated with c-Jun N-terminal kinase (JNK) inhibitor, the autophagy induced by ER stress was inhibited, indicating that the IRE1-JNK pathway is required for autophagy activation after ER stress. In contrast, PERK-deficient cells and ATF6 knockdown cells showed that autophagy was induced after ER stress in a manner similar to the wild-type cells. Disturbance of autophagy rendered cells vulnerable to ER stress, suggesting that autophagy plays important roles in cell survival after ER stress.

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ROS and Autophagy: Interactions and Molecular Regulatory Mechanisms.

Lulu Li, Wai Jin Tan, Yuyang Miao … (2015)

Reactive oxygen species (ROS) and antioxidant ingredients are a series of crucial signaling molecules in oxidative stress response. Under some pathological conditions such as traumatic brain injury, ischemia/reperfusion, and hypoxia in tumor, the relative excessive accumulation of ROS could break cellular homeostasis, resulting in oxidative stress and mitochondrial dysfunction. Meanwhile, autophagy is also induced. In this process, oxidative stress could promote the formation of autophagy. Autophagy, in turn, may contribute to reduce oxidative damages by engulfing and degradating oxidized substance. This short review summarizes these interactions between ROS and autophagy in related pathological conditions referred to as above with a focus on discussing internal regulatory mechanisms. The tight interactions between ROS and autophagy reflected in two aspects: the induction of autophagy by oxidative stress and the reduction of ROS by autophagy. The internal regulatory mechanisms of autophagy by ROS can be summarized as transcriptional and post-transcriptional regulation, which includes various molecular signal pathways such as ROS-FOXO3-LC3/BNIP3-autophagy, ROS-NRF2-P62-autophagy, ROS-HIF1-BNIP3/NIX-autophagy, and ROS-TIGAR-autophagy. Autophagy also may regulate ROS levels through several pathways such as chaperone-mediated autophagy pathway, mitophagy pathway, and P62 delivery pathway, which might provide a further theoretical basis for the pathogenesis of the related diseases and still need further research.

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AMPK-SKP2-CARM1 signalling cascade in transcriptional regulation of autophagy.

Hi-Jai Shin, Hyunkyung Kim, Sungryong Oh … (2016)

Autophagy is a highly conserved self-digestion process, which is essential for maintaining homeostasis and viability in response to nutrient starvation. Although the components of autophagy in the cytoplasm have been well studied, the molecular basis for the transcriptional and epigenetic regulation of autophagy is poorly understood. Here we identify co-activator-associated arginine methyltransferase 1 (CARM1) as a crucial component of autophagy in mammals. Notably, CARM1 stability is regulated by the SKP2-containing SCF (SKP1-cullin1-F-box protein) E3 ubiquitin ligase in the nucleus, but not in the cytoplasm, under nutrient-rich conditions. Furthermore, we show that nutrient starvation results in AMP-activated protein kinase (AMPK)-dependent phosphorylation of FOXO3a in the nucleus, which in turn transcriptionally represses SKP2. This repression leads to increased levels of CARM1 protein and subsequent increases in histone H3 Arg17 dimethylation. Genome-wide analyses reveal that CARM1 exerts transcriptional co-activator function on autophagy-related and lysosomal genes through transcription factor EB (TFEB). Our findings demonstrate that CARM1-dependent histone arginine methylation is a crucial nuclear event in autophagy, and identify a new signalling axis of AMPK-SKP2-CARM1 in the regulation of autophagy induction after nutrient starvation.

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Journal

Journal ID (nlm-ta): Theranostics

Journal ID (iso-abbrev): Theranostics

Journal ID (publisher-id): thno

Title: Theranostics

Publisher: Ivyspring International Publisher (Sydney )

ISSN (Electronic): 1838-7640

Publication date Collection: 2020

Publication date (Electronic): 23 July 2020

Volume: 10

Issue: 20

Pages: 9280-9302

Affiliations

[1 ]Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325000, China.

[2 ]Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, 325000, China.

[3 ]University of Maryland School of Medicine, Baltimore, MD 21201, USA.

Author notes

✉ Corresponding authors: Jian Xiao, E-mail: xfxj2000@ 123456126.com ; Huazi Xu, E-mail: spinexu@ 123456163.com .

#Co-first authors with equal contributions to this manuscript.

Competing Interests: The authors have declared that no competing interest exists.

Article

Publisher ID: thnov10p9280

DOI: 10.7150/thno.46566

PMC ID: 7415792

PubMed ID: 32802192

SO-VID: 2c870a72-8612-4bee-ada0-9b17cfaa261a

License:

This is an open access article distributed under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.

TFE3, a potential therapeutic target for Spinal Cord Injury via augmenting autophagy flux and alleviating ER stress

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Most cited references 55

Autophagy is activated for cell survival after endoplasmic reticulum stress.

ROS and Autophagy: Interactions and Molecular Regulatory Mechanisms.

AMPK-SKP2-CARM1 signalling cascade in transcriptional regulation of autophagy.

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