Chronic treatment with the complex I inhibitor MPP+ depletes endogenous PTEN-induced kinase 1 (PINK1) via up-regulation of Bcl-2–associated athanogene 6 (BAG6)

Manish Verma,Jianhui Zhu,Kent Z.Q Wang,Charleen T Chu

doi:10.1074/jbc.ra119.010474

Manish Verma, Jianhui Zhu + Show 2 more

Open Access

https://doi.org/10.1074/jbc.ra119.010474

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Abstract

Mitochondrial dysfunction is implicated in sporadic and familial Parkinson's disease (PD). However, the mechanisms that impair homeostatic responses to mitochondrial dysfunction remain unclear. Previously, we found that chronic, low-dose administration of the mitochondrial complex I inhibitor 1-methyl-4-phenylpyridinium (MPP+) dysregulates mitochondrial fission-fusion, mitophagy, and mitochondrial biogenesis. Given that PTEN-induced kinase 1 (PINK1) regulates mitochondrial function, dynamics, and turnover, we hypothesized that alterations in endogenous PINK1 levels contribute to depletion of mitochondria during chronic complex I injury. Here we found that chronic MPP+ treatment of differentiated SH-SY5Y neuronal cells significantly decreases PINK1 expression prior to reductions in other mitochondrial components. Furthermore, Bcl2-associated athanogene 6 (BAG6, BAT3, or Scythe), a protein involved in protein quality control and degradation, was highly up-regulated during the chronic MPP+ treatment. BAG6 interacted with PINK1, and BAG6 overexpression decreased the half-life of PINK1. Conversely, siRNA-mediated BAG6 knockdown prevented chronic MPP+ stress-induced loss of PINK1, reversed MPP+-provoked mitochondrial changes, increased cell viability, and prevented MPP+-induced dendrite shrinkage in primary neurons. These results indicate that BAG6 up-regulation during chronic complex I inhibition contributes to mitochondrial pathology by decreasing the levels of endogenous PINK1. Given that recessive mutations in PINK1 cause familial PD, the finding of accelerated PINK1 degradation in the chronic MPP+ model suggests that PINK1 loss of function represents a point of convergence between the neurotoxic and genetic causes of PD.

Highlights

Mitochondrial dysfunction is implicated in sporadic and familial Parkinson’s disease (PD)
Genetic models based upon mutations in ␣-synuclein, Parkin, PTEN-induced kinase 1 (PINK1), LRRK2, and DJ-1 have further emphasized the role of mitochondrial dyshomeostasis in the pathogenesis of PD [1, 4, 5]
Chronic treatment of differentiated SH-SY5Y cells with 250 ␮M MPPϩ resulted in reduced expression of both full-length (FL) and processed forms of PINK1 normalized to GAPDH (Fig. 1, A and B, and Table 1)

Summary

Introduction

Mitochondrial dysfunction is implicated in sporadic and familial Parkinson’s disease (PD). Chronic treatment of differentiated SH-SY5Y cells with 250 ␮M MPPϩ resulted in reduced expression of both full-length (FL) and processed (dN) forms of PINK1 normalized to GAPDH (Fig. 1, A and B, and Table 1). To determine whether loss of PINK1 played a pathogenic role in the chronic MPPϩ model, we transfected neuronally differentiated SH-SY5Y cells with plasmids expressing either GFP or GFP-tagged WT PINK1.

Results

Conclusion