title: Regulation of autophagy by extracellular signal-regulated protein kinases during 1-methyl-4-phenylpyridinium-induced cell death.
abstract: Increased autophagic vacuoles (AVs) occur in injured or degenerating neurons, under both developmental and pathological situations. Although regulation of starvation-induced autophagy has been extensively studied, less is known about autophagic responses to pathological damage. The neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)) produces mitochondria-targeted injury, which contributes to parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine in mammals. Here, we demonstrate that MPP(+) elicited increased autophagy in SH-SY5Y cells, as assessed by electron microscopy, immunofluorescence for the autophagy protein LC3/Atg8, LC3 electrophoretic mobility shift, mitochondrial degradation, and monodansylcadaverine staining for late AVs/autolysosomes. During nutrient deprivation, class III phosphatidylinositol-3 kinase (PI3K) stimulates autophagy in concert with the autophagy-regulatory protein beclin 1/Atg6. Although PI3K inhibitors and RNA interference knockdown of beclin 1 effectively inhibited autophagy elicited by amino acid deprivation, neither reduced MPP+-induced autophagic stress. In contrast, inhibition of mitogen-activated protein kinase/extracellular signal-regulated protein kinase kinase reduced AV content, mitochondrial degradation, and cell death in MPP+-treated cells. RNA interference studies targeting core Atg proteins also reduced AV content and cell death. Likewise, in primary midbrain dopaminergic neurons, MPP+ elicited increased AV content, which was reversed by inhibition of mitogen-activated protein kinase/extracellular signal-regulated protein kinase kinase but not PI3K. These results implicate a role for extracellular signal-regulated protein kinase (ERK) signaling upstream of MPP+-elicited autophagic stress. Moreover, pathological stimulation of beclin 1-independent autophagy is associated with neuronal cell death.
authors.affiliation: Department of Pathology/Division of Neuropathology, Pittsburgh Institute for Neurodegenerative Diseases, Center for Biologic Imaging, Pittsburgh, PA, USA.
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Zhu
authors.forename: Craig
authors.initials: C
authors.lastname: Horbinski
authors.forename: Fengli
authors.initials: F
authors.lastname: Guo
authors.forename: Simon
authors.initials: S
authors.lastname: Watkins
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Uchiyama
authors.forename: Charleen T
authors.initials: CT
authors.lastname: Chu
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology*; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1; D045744:Cell Line, Tumor; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008636:Mesencephalon / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011506:Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D008565:Membrane Proteins; D011506:Proteins; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D015655:1-Methyl-4-phenylpyridinium