title: Roles of p62 in BDNF-dependent autophagy suppression and neuroprotection against mitochondrial dysfunction in rat cortical neurons.
abstract: Previously, we have reported that pre-conditioning of primary rat cortical neurons with brain-derived neurotrophic factor (BDNF) may exert neuroprotective effects against 3-nitropropionic acid (3-NP), a mitochondrial complex II inhibitor. However, the underlying mechanisms, especially potential involvements of autophagy, remain elusive. In this work, we tested the hypothesis that BDNF may suppress 3-NP-induced autophagy to exert its neuroprotective effects by inducing the expression of p62/sequestosome-1 in primary cortical neurons. We found that 3-NP increased total level of microtubule-associated protein 1A/1B-light chain (LC)-3 as well as the LC3-II/LC3-I ratio, an index of autophagy, in primary cortical neurons. BDNF decreased LC3-II/LC3-I ratio and time-dependently induced expression of p62. Knockdown of p62 by siRNA restored LC3-II/LC3-I ratio and increased total LC3 levels associated with BDNF exposure; p62 knockdown also abolished BDNF-dependent neuroprotection against 3-NP. Upstream of p62, we found that BDNF triggered phosphorylation of mammalian target of rapamycin (mTOR) and its downstream mediator p70S6K; importantly, the mTOR inhibitor rapamycin reduced both BDNF-dependent p62 induction as well as 3-NP resistance. BDNF is known to induce c-Jun in cortical neurons. We found that c-Jun knockdown in part attenuated BDNF-mediated p62 induction, whereas p62 knockdown had no significant effects on c-Jun expression. In addition to suppressing p62 induction, rapamycin also partially suppressed BDNF-induced c-Jun expression, but c-Jun knockdown failed to affect mTOR activation. Together, our results suggested that BDNF inhibits 3-NP-induced autophagy via, at least in part, mTOR/c-Jun-dependent induction of p62 expression, together contributing to neuroprotection against mitochondrial inhibition.
authors.affiliation: Program in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan.|Institute of Brain Science and Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chia-Lin
authors.initials: CL
authors.lastname: Wu
authors.affiliation: Institute of Brain Science and Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chien-Hui
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Department of Neurology, Taipei City Hospital, Taipei, Taiwan.|Department of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chi-Shin
authors.initials: CS
authors.lastname: Hwang
authors.affiliation: Department of Neurology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.|Center for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Shang-Der
authors.initials: SD
authors.lastname: Chen
authors.affiliation: Department of Neurology, Taipei City Hospital, Taipei, Taiwan.
authors.forename: Wei-Chao
authors.initials: WC
authors.lastname: Hwang
authors.affiliation: Institute of Brain Science and Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ding-I
authors.initials: DI
authors.lastname: Yang
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D000066829:Neuroprotection / Q000187:drug effects / Q000502:physiology*; D009574:Nitro Compounds / Q000633:toxicity; D011247:Pregnancy; D011422:Propionates / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071456:Sequestosome-1 Protein / Q000502:physiology*
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D009574:Nitro Compounds; D011422:Propionates; D000071456:Sequestosome-1 Protein; C491079:Sqstm1 protein, rat; C015392:3-nitropropionic acid
keywords: LC3; brain-derived neurotrophic factor (BDNF); c-Jun; mTOR; p62/sequestosome 1; rapamycin