Perturbation of redox balance after thioredoxin reductase deficiency interrupts autophagy-lysosomal degradation pathway and enhances cell death in nutritionally stressed SH-SY5Y cells.
Oxidative damage and aggregation of cellular proteins is a hallmark of neuronal cell death after neurotrauma and chronic neurodegenerative conditions. Autophagy and ubiquitin protease system are involved in degradation of protein aggregates, and interruption of their function is linked to apoptotic cell death in these diseases. Oxidative modification of cysteine groups in key molecular proteins has been linked to modification of cellular systems and cell death in these conditions. Glutathione and thioredoxin systems provide reducing protons that can effectively reverse protein modifications and promote cell survival. The central role of Thioredoxin in inhibition of apoptosis is well identified. Additionally, its involvement in initiation of autophagy has been suggested recently. We therefore aimed to investigate the involvement of Thioredoxin system in autophagy-apoptosis processes. A model of serum deprivation in SH-SY5Y was used that is associated with autophagy and apoptosis. Using pharmacological and RNA-editing technology we show that Thioredoxin reductase deficiency in this model enhances oxidative stress and interrupts the early protective autophagy and promotes apoptosis. This was associated with decreased protein-degradation in lysosomes due to altered lysosomal acidification and accumulation of autophagosomes as well as impairment in proteasome pathway. We further confirmed that the extent of oxidative stress is a determining factor in autophagy- apoptosis interplay, as upregulation of cellular reducing capacity by N-acetylcysteine prevented impairment in autophagy and proteasome systems thus promoted cell viability. Our study provides evidence that excessive oxidative stress inhibits protein degradation systems and affects the final stages of autophagy by inhibiting autolysosome maturation: a novel mechanistic link between protein aggregation and conversion of autophagy to apoptosis that can be applicable to neurodegenerative diseases.
Spinal Cord Research Center, Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; Regenerative Medicine Program, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Pandian
P
Nagakannan
Spinal Cord Research Center, Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; Regenerative Medicine Program, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Mohamed Ariff
MA
Iqbal
Spinal Cord Research Center, Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; Regenerative Medicine Program, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Albert
A
Yeung
Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
James A
JA
Thliveris
Department of Biochemistry & Medical Genetics, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; Regenerative Medicine Program, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Mojgan
M
Rastegar
Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Saeid
S
Ghavami
Spinal Cord Research Center, Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; Regenerative Medicine Program, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Eftekhar
E
Eftekharpour
D000111:Acetylcysteine / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects*; D000071193:Autophagy-Related Protein 7 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D016086:Lentivirus / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010084:Oxidation-Reduction; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects* / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species; D054481:Thioredoxin Reductase 1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
D000975:Antioxidants; D016895:Culture Media, Serum-Free; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C516124:TXNRD1 protein, human; D054481:Thioredoxin Reductase 1; D046988:Proteasome Endopeptidase Complex; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D000111:Acetylcysteine
Autophagy-Apotosis Interplay; Lysosome; Neurodegenerative disease; Proteasome; Redox Regulation; Ubiquitination