Mitochondrially localized ERK2 regulates mitophagy and autophagic cell stress: implications for Parkinson's disease

Autophagy. 2008 Aug;4(6):770-82. doi: 10.4161/auto.6458. Epub 2008 Jun 16.

Abstract

Degenerating neurons of Parkinson's disease (PD) patient brains exhibit granules of phosphorylated extracellular signal-regulated protein kinase 1/2 (ERK1/2) that localize to autophagocytosed mitochondria. Here we show that 6-hydroxydopamine (6-OHDA) elicits activity-related localization of ERK1/2 in mitochondria of SH-SY5Y cells, and these events coincide with induction of autophagy and precede mitochondrial degradation. Transient transfection of wildtype (WT) ERK2 or constitutively active MAPK/ERK Kinase 2 (MEK2-CA) was sufficient to induce mitophagy to a degree comparable with that elicited by 6-OHDA, while constitutively active ERK2 (ERK2-CA) had a greater effect. We developed green fluorescent protein (GFP) fusion constructs of WT, CA, and kinase-deficient (KD) ERK2 to study the role of ERK2 localization in regulating mitophagy and cell death. Under basal conditions, cells transfected with GFP-ERK2-WT or GFP-ERK2-CA, but not GFP-ERK2-KD, displayed discrete cytoplasmic ERK2 granules of which a significant fraction colocalized with mitochondria and markers of autophagolysosomal maturation. The colocalizing GFP-ERK2/mitochondria granules are further increased by 6-OHDA and undergo autophagic degradation, as bafilomycin-A, an inhibitor of autolysosomal degradation, robustly increased their detection. Interestingly, increasing ERK2-WT or ERK2-CA expression was sufficient to promote comparable levels of macroautophagy as assessed by analysis of the autophagy marker microtubule-associated protein 1 light chain 3 (LC3). In contrast, the level of mitophagy was more tightly correlated with ERK activity levels, potentially explained by the greater localization of ERK2-CA to mitochondria compared to ERK2-WT. These data indicate that mitochondrial localization of ERK2 activity is sufficient to recapitulate the effects of 6-OHDA on mitophagy and autophagic cell death.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Autophagy / physiology*
  • Biomarkers / metabolism
  • Cell Line / drug effects
  • Cytoplasmic Granules / metabolism
  • Enzyme Activation
  • Humans
  • Lysosomes / metabolism
  • MAP Kinase Signaling System / physiology
  • Mitochondria / drug effects
  • Mitochondria / enzymology*
  • Mitochondria / pathology
  • Mitogen-Activated Protein Kinase 1 / genetics
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Mitogen-Activated Protein Kinase 3 / genetics
  • Mitogen-Activated Protein Kinase 3 / metabolism*
  • Oxidative Stress*
  • Oxidopamine / pharmacology
  • Parkinson Disease / metabolism*
  • Parkinson Disease / pathology
  • Phagosomes / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism

Substances

  • Biomarkers
  • Recombinant Fusion Proteins
  • Oxidopamine
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3