Cited by 44Autophagy in Disease and TherapyAmyotrophic Lateral Sclerosis ResearchGenetics, Aging, and Longevity in Model Organisms

Inhibition of p70 S6 kinase activity by A77 1726 induces autophagy and enhances the degradation of superoxide dismutase 1 (SOD1) protein aggregates

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Sun, Jing, Mu, Yarong, Jiang, Yuanyuan, Song, Ruilong, Yi, Jianxin, Zhou, Jingsong, Sun, Jun, Jiao, Xinan +3 more·2018·Cell Death & Disease

Abstract

Autophagy plays a central role in degrading misfolded proteins such as mutated superoxide dismutase 1 (SOD1), which forms aggregates in motor neurons and is involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). Autophagy is activated when UNC-51-like kinase 1 (ULK1) is phosphorylated at S555 and activated by AMP-activated protein kinase (AMPK). Autophagy is suppressed when ULK1 is phosphorylated at S757 by the mechanistic target of rapamycin (mTOR). Whether p70 S6 kinase 1 (S6K1), a serine/threonine kinase downstream of mTOR, can also regulate autophagy remains uncertain. Here we report that inhibition of S6K1 by A77 1726, the active metabolite of an anti-inflammatory drug leflunomide, induced mTOR feedback activation and ULK1 S757 phosphorylation in NSC34 cells, a hybrid mouse motoneuron cell line. Unexpectedly, A77 1726 did not suppress but rather induced autophagy by increasing AMPK T172 and ULK1 S555 phosphorylation. Similar observations were made with PF-4708671, a specific S6K1 inhibitor, or with S6K1 siRNA. Further studies showed that A77 1726 induced AMPK phosphorylation by activating the TGF-β-activated kinase 1 (TAK1). Functional studies revealed that A77 1726 induced co-localization of mutant SOD1 G93A protein aggregates with autophagosomes and accelerated SOD1 G93A protein degradation, which was blocked by inhibition of autophagy through autophagy-related protein 7 (ATG7) siRNA. Our study suggests that S6K1 inhibition induces autophagy through TAK1-mediated AMPK activation in NSC34 cells, and that blocking S6K1 activity by a small molecule inhibitor such as leflunomide may offer a new strategy for ALS treatment.

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  • In G93A mice, dysregulation of autophagy leads to the elimination of misfolded proteins such as superoxide dismutase 1, and this dismutant form accumulates in the motor neurons involved in the pathogenesis of ALS.

    “Dysregulation of autophagy appears to lead to the elimination of misfolded proteins, such as superoxide dismutase 1, in G93A mice, and this dismutant form accumulates in the motor neurons involved in the pathogenesis of ALS (88).”

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Authors
Sun, J., Mu, Y., Jiang, Y., Song, R., Yi, J., Zhou, J., Sun, J., Jiao, X., Prinz, R. A., Li, Y., & Xu, X.
Affiliations
  • University of Illinois Chicago (US)
  • Yangzhou University (CN)
  • Kansas City University (US)
  • Endeavor Health (US)
  • Baylor College of Medicine (US)
  • Rush University Medical Center (US)
Corresponding author
Xu, Xiulong
Venue
Cell Death & Disease
Published
2018-03-14
Volume
9
Issue
3
Pages
407-407
ISSN
2041-4889 (ISSN-L)
OpenAlex
W2793701057
Cited by
44
References
64
Citations by year
2026: 1 · 2025: 4 · 2024: 3 · 2023: 3 · 2022: 11 · 2021: 8 · 2020: 7 · 2019: 6 · 2018: 1
FWCI
4.29
Type
journal article
Language
en
Open access
Locations
  • Cell Death and Disease (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Funders
  • U.S. Department of Defense
  • Northwestern University
  • National Natural Science Foundation of China (81672643)
  • China Postdoctoral Science Foundation (BK20150450, 2015311, 2015M581873)
  • Government of Jiangsu Province
  • Natural Science Foundation of Jiangsu Province (2015M581873, 2015311, BK20150450)
  • Yangzhou University
  • Priority Academic Program Development of Jiangsu Higher Education Institutions
  • National Institutes of Health
  • National Institute of Arthritis and Musculoskeletal and Skin Diseases (R01AR057404)
Topics
  • Health Sciences › Medicine › Epidemiology › Autophagy in Disease and Therapy
  • Health Sciences › Medicine › Neurology › Amyotrophic Lateral Sclerosis Research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Aging › Genetics, Aging, and Longevity in Model Organisms
Keywords
A771726, leflunomide, autophagy, superoxide dismutase 1, amyotrophic lateral sclerosis, ULK1 phosphorylation, AMPK activation, TAK1, ATG7, protein degradation, motor neurons
MeSH terms
Autophagy-Related Protein-1 Homolog, Autophagy-Related Protein 7, Superoxide Dismutase-1, AMP-Activated Protein Kinase Kinases, MAP Kinase Kinase Kinase 7, Aniline Compounds, Animals, Autophagy, Cell Line, Crotonates, Hydroxybutyrates, Nitriles, Protein Kinases, Toluidines, Amino Acid Motifs, MAP Kinase Kinase Kinases, Ribosomal Protein S6 Kinases, 70-kDa, Mice, TOR Serine-Threonine Kinases, Proteolysis, Protein Aggregates

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