Inhibition of the mitochondrial calcium uniporter rescues dopaminergic neurons in pink1-/- zebrafish.

Smijin Soman,Marcus Keatinge,Jacek Kuznicki,Oliver Bandmann,Marc Da Costa,Sreedevi Sugunan,Mahsa Moein,Alexander Skupin,Michal Bazala,Heather Mortiboys

doi:10.1111/ejn.13473

Abstract

Mutations in PTEN‐induced putative kinase 1 (PINK1) are a cause of early onset Parkinson's disease (PD). Loss of PINK1 function causes dysregulation of mitochondrial calcium homeostasis, resulting in mitochondrial dysfunction and neuronal cell death. We report that both genetic and pharmacological inactivation of the mitochondrial calcium uniporter (MCU), located in the inner mitochondrial membrane, prevents dopaminergic neuronal cell loss in pink1 Y431* mutant zebrafish (Danio rerio) via rescue of mitochondrial respiratory chain function. In contrast, genetic inactivation of the voltage dependent anion channel 1 (VDAC1), located in the outer mitochondrial membrane, did not rescue dopaminergic neurons in PINK1 deficient D. rerio. Subsequent gene expression studies revealed specific upregulation of the mcu regulator micu1 in pink1 Y431* mutant zebrafish larvae and inactivation of micu1 also results in rescue of dopaminergic neurons. The functional consequences of PINK1 deficiency and modified MCU activity were confirmed using a dynamic in silico model of Ca2+ triggered mitochondrial activity. Our data suggest modulation of MCU‐mediated mitochondrial calcium homeostasis as a possible neuroprotective strategy in PINK1 mutant PD.

Highlights

Parkinson’s disease (PD) is a common neurodegenerative disorder, resulting in both motor and non-motor symptoms (Kalia & Lang, 2015)
We recently reported our findings in a zebrafish mutant line carrying a Stop mutation in the kinase domain of pink1, the zebrafish orthologue of the human PD gene PINK1 (Flinn et al, 2013). pink1-/- already resulted in impaired function of the mitochondrial respiratory chain and loss of dopaminergic neurons at 3 days post fertilization
mitochondrial calcium uniporter (MCU) inactivation rescues dopaminergic neurons in PINK1 deficiency mcu (ENSDARG00000101175), the zebrafish orthologue of human MCU (ENSG00000156026), was identified using Ensembl genome browser. mcu shares 70.7% DNA and 78.8% protein identity with human MCU. mcu was already expressed at 1 hour post fertilization, expression was constant throughout development (Fig 1A)

Summary

Introduction

Parkinson’s disease (PD) is a common neurodegenerative disorder, resulting in both motor and non-motor symptoms (Kalia & Lang, 2015). Loss of PINK1 function results in mitochondrial calcium overload, thought to be due to impaired calcium efflux from the mitochondria (Gandhi et al, 2009; Marongiu et al, 2009). The reduced mitochondrial calcium capacity in PINK1 deficient neurons results in increased oxidative stress which in turn leads to reduced glucose uptake and a lowering of the threshold for the opening of the permeability transition pore (PTP). This suggests that impaired mitochondrial calcium homeostasis is at least one of the pathological mechanisms resulting from PINK1 deficiency

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Conclusion