Mdm2 enhances ligase activity of parkin and facilitates mitophagy

Seunghyi Kook,Eugenia V Gurevich,Mohamed R Ahmed,Vsevolod V Gurevich,Kimberly Thibeault,Mohamed R Ahmed,Xuanzhi Zhan,Xuanzhi Zhan

doi:10.1038/s41598-020-61796-4

Seunghyi Kook, Eugenia V Gurevich + Show 6 more

Open Access

https://doi.org/10.1038/s41598-020-61796-4

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Abstract

Loss-of-function mutations in the E3 ubiquitin ligase parkin have been implicated in the death of dopaminergic neurons in the substantia nigra, which is the root cause of dopamine deficit in the striatum in Parkinson's disease. Parkin ubiquitinates proteins on mitochondria that lost membrane potential, promoting the elimination of damaged mitochondria. Neuroprotective activity of parkin has been linked to its critical role in the mitochondria maintenance. Here we report a novel regulatory mechanism: another E3 ubiquitin ligase Mdm2 directly binds parkin and enhances its enzymatic activity in vitro and in intact cells. Mdm2 translocates to damaged mitochondria independently of parkin, enhances parkin-dependent ubiquitination of the outer mitochondria membrane protein mitofusin1. Mdm2 facilitates and its knockdown reduces parkin-dependent mitophagy. Thus, ubiquitously expressed Mdm2 might enhance cytoprotective parkin activity. The data suggest that parkin activation by Mdm2 could be targeted to increase its neuroprotective functions, which has implications for anti-parkinsonian therapy.

Highlights

Loss-of-function mutations in the E3 ubiquitin ligase parkin have been implicated in the death of dopaminergic neurons in the substantia nigra, which is the root cause of dopamine deficit in the striatum in Parkinson's disease
We have recently demonstrated that parkin dose-dependently promotes the association of another E3 ubiquitin ligase, murine double minute oncogene (Mdm2), with arrestins[37], proteins best known for their role in the homologous desensitization of G protein-coupled receptors (GPCRs)[38]
We found that GST-Mdm[2], but not GST, retained maltose binding protein (MBP)-parkin, whereas neither protein interacted with MBP (Fig. 1A)

Summary

Introduction

Loss-of-function mutations in the E3 ubiquitin ligase parkin have been implicated in the death of dopaminergic neurons in the substantia nigra, which is the root cause of dopamine deficit in the striatum in Parkinson's disease. We have recently demonstrated that parkin dose-dependently promotes the association of another E3 ubiquitin ligase, murine double minute oncogene (Mdm2), with arrestins[37], proteins best known for their role in the homologous desensitization of G protein-coupled receptors (GPCRs)[38]. Another major function of arrestins is to act as scaffolds of multi-protein complexes regulating the activity of signaling proteins[39,40,41,42]. Mdm[2] stimulates catalytic activity of parkin and promotes its biological functions in intact cells

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