title: Accumulation of p62 in degenerated spinal cord under chronic mechanical compression: functional analysis of p62 and autophagy in hypoxic neuronal cells.
abstract: Intracellular accumulation of altered proteins, including p62 and ubiquitinated proteins, is the basis of most neurodegenerative disorders. The relationship among the accumulation of altered proteins, autophagy, and spinal cord dysfunction by cervical spondylotic myelopathy has not been clarified. We examined the expression of p62 and autophagy markers in the chronically compressed spinal cord of tiptoe-walking Yoshimura mice. In addition, we examined the expression and roles of p62 and autophagy in hypoxic neuronal cells. Western blot analysis showed the accumulation of p62, ubiquitinated proteins, and microtubule-associated protein 1 light chain 3 (LC3), an autophagic marker, in the compressed spinal cord. Immunohistochemical examinations showed that p62 accumulated in neurons, axons, astrocytes, and oligodendrocytes. Electron microscopy showed the expression of autophagy markers, including autolysosomes and autophagic vesicles, in the compressed spinal cord. These findings suggest the presence of p62 and autophagy in the degenerated compressed spinal cord. Hypoxic stress increased the expression of p62, ubiquitinated proteins, and LC3-II in neuronal cells. In addition, LC3 turnover assay and GFP-LC3 cleavage assay showed that hypoxic stress increased autophagy flux in neuronal cells. These findings suggest that hypoxic stress induces accumulation of p62 and autophagy in neuronal cells. The forced expression of p62 decreased the number of neuronal cells under hypoxic stress. These findings suggest that p62 accumulation under hypoxic stress promotes neuronal cell death. Treatment with 3-methyladenine, an autophagy inhibitor decreased the number of neuronal cells, whereas lithium chloride, an autophagy inducer increased the number of cells under hypoxic stress. These findings suggest that autophagy promotes neuronal cell survival under hypoxic stress. Our findings suggest that pharmacological inducers of autophagy may be useful for treating cervical spondylotic myelopathy patients.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Kagoshima Prefecture, Japan.
authors.forename: Fumito
authors.initials: F
authors.lastname: Tanabe
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yone
authors.forename: Naoya
authors.initials: N
authors.lastname: Kawabata
authors.forename: Harutoshi
authors.initials: H
authors.lastname: Sakakima
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Matsuda
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishidou
authors.forename: Shingo
authors.initials: S
authors.lastname: Maeda
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abematsu
authors.forename: Setsuro
authors.initials: S
authors.lastname: Komiya
authors.forename: Takao
authors.initials: T
authors.lastname: Setoguchi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology; D001343:Autophagy; D001369:Axons / Q000378:metabolism / Q000473:pathology; D002452:Cell Count; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002574:Cervical Vertebrae / Q000473:pathology / Q000648:ultrastructure; D006360:Heat-Shock Proteins / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009410:Nerve Degeneration / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D009836:Oligodendroglia / Q000378:metabolism / Q000473:pathology; D010588:Phagosomes / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D013117:Spinal Cord Compression / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D013314:Stress, Mechanical; D013312:Stress, Physiological; D057149:Ubiquitinated Proteins / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D006360:Heat-Shock Proteins; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D000071456:Sequestosome-1 Protein; C101343:Sqstm1 protein, mouse; D057149:Ubiquitinated Proteins
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