Resolving endogenous PINK1-Parkin activation to in vivo mitophagy Thomas G McWilliams1,2 Risto Pohjolan-Pirhonen2, Lambert Montava-Garriga, Alan R Prescott1, Francois Singh1, Pentti J Tienari2, Erica Barini1, Simon P Brooks3, Anu Suomalainen2, Miratul M K Muqit1, Ian G Ganley1 1MRC Protein Phosphorylation & Ubiquitylation Unit, University of Dundee, UK; 2Molecular Neurology Research Unit, University of Helsinki, Finland; 3The Brain Repair Group, Cardiff University, UK
Our recently developed fluorescent reporter mouse model (mito-QC) revealed mitophagy is both highly pervasive and constitutive in vivo, with striking spatiotemporal heterogeneity1,2. Although PINK1-Parkin signalling regulates mitophagy in vitro, its contribution in vivo has remained elusive3. With newly developed tools, we report the first detection of endogenous mouse PINK1 protein under basal conditions in vivo, verified using Pink1 knock-out (KO) tissues and mass spectrometry4. Regardless, genetic ablation of PINK1 did not perturb the mito-QC readout of basal mitophagy in clinically-relevant midbrain dopaminergic neurons and all other tissues of high metabolic demand. We next analysed the pathway in more detail by characterizing a mouse model expressing non-activating form of Parkin. Mature primary neurons from these mutant mice cannot activate the PINK1-Parkin pathway, as evidenced by the collective loss of E3 activity and phospho-ubiquitin. Strikingly, in the absence of any discernable stress, Parkin mutant mice exhibit selective mitochondrial and motor defects. However, when crossed with mito-QC, basal mitophagy in Parkin mutant mice remains largely unaffected. Conversely, these animals exhibit modest mitochondrial dysfunction in muscle, representing the first convergence of Parkin phenotypes from Drosophila to mammals. Finally, we report the discovery of a new human Parkinson's disease mutation, validating the clinical significance of our mouse findings. Our work clarifies the physiological significance of PINK1-Parkin signalling to in vivo mitophagy, and the importance of Parkin activation in mammals.
References: 1. McWilliams et al (2016) Journal of Cell Biology 2. McWilliams & Ganley (2016) Autophagy 3. McWilliams & Muqit (2017) Current Opinion in Cell Biology 4. McWilliams et al (2017) Cell Metabolism (In Press)
Funding: Medical Research Council, Wellcome Trust (UK), Michael J Fox Foundation for PD Research (USA), Sigrid Jusélius Foundation (FI)
Credits: None available.
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