Mitochondrially localized ERK2 regulates mitophagy and autophagic cell stress

作者：Dagda Ruben K; Zhu Jianhui; Kulich Scott M; Chu Charleen T^*

来源：Autophagy, 2008, 4(6): 770-782.

DOI：10.4161/auto.6458

• autophagy
• oxidative stress
• mitochondria
• mitogen activated protein kinases
• 6-hydroxydopamine
• Parkinson's disease

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 (NIEK2-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 I 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.

• 出版日期2008-8-16