Parkin Ubiquitinates Drp1 for Proteasome-dependent Degradation

Abstract

Mutations in Parkin, an E3 ubiquitin ligase that regulates protein turnover, represent one of the major causes of familial Parkinson disease, a neurodegenerative disorder characterized by the loss of dopaminergic neurons and impaired mitochondrial functions. The underlying mechanism by which pathogenic Parkin mutations induce mitochondrial abnormality is not fully understood. Here, we demonstrate that Parkin interacts with and subsequently ubiquitinates dynamin-related protein 1 (Drp1), for promoting its proteasome-dependent degradation. Pathogenic mutation or knockdown of Parkin inhibits the ubiquitination and degradation of Drp1, leading to an increased level of Drp1 for mitochondrial fragmentation. These results identify Drp1 as a novel substrate of Parkin and suggest a potential mechanism linking abnormal Parkin expression to mitochondrial dysfunction in the pathogenesis of Parkinson disease. Parkinson disease (PD)4 is one of the most common neurodegenerative diseases affecting over 2% populations over 65 years of age. It is classically characterized by the loss of dopaminergic neurons that project from the midbrain substantia nigra to the striatum (1, 2). Although the loss of dopaminergic neurons is responsible for the symptom of movement disorder in PD, it is now clear that other types of neurons throughout the brain are also affected in the disease (3, 4). The identification of genes linking to PD has greatly advanced our understanding of the molecular pathogenesis of the disease (5-8). Mutations in Parkin represent one of major causes for early onset of familial PD (9 -11). Parkin is an E3 ubiquitin ligase that contains two ring finger domains (12-15). A handful of substrates have been identified, including Parkin itself and CDCrel-1, synphilin-1, Pael-R, glycosylated ␣-synuclein, FBP1 (far upstream elementbinding protein 1), and the RNA-processing protein subunit p38/AIMP2 (16 -19). A putative mechanism by which mutations of Parkin cause PD would be abnormal accumulation and aggregation of the above substrates due to insufficient E3 ligase activity for ubiquitin-proteasome-dependent protein turnover (18,20,21). Surprisingly, only p38/AIMP2 and FBP1 were found to be accumulated in the brain samples of PD patients or in Parkin knock-out mice (16,17,19). Even though a number of the putative substrates have been identified, the causative link between these substrates and the PD pathogenesis remains not fully understood.Over the past few decades, accumulating evidence has suggested that mitochondrial dysfunction and the resulting oxidative damage are associated with PD. This is supported by a large number of reports demonstrating impaired mitochondrial functions in PD patients (22)(23)(24)(25)(26). Mitochondria undergo frequent fission, fusion, and redistribution throughout the cytoplasm in response to the energy needs (27,28). Either disruption of the fusion process or enhancement of the fission process renders the normal, tubular network of mitochondria to fragment into short rods or spheres (29). Abnormal...

Parkin Mediates Proteasome-dependent Protein Degradation and Rupture of the Outer Mitochondrial Membrane

“…During revision of this study, three independent groups reported that OMM proteins including mitofusin 1/2, Tom20, Tom70, and VDAC can be degraded in a Parkin-and proteasome-dependent manner (17,41,45). Two of them suggest that degradation of mitofusin or other OMM proteins could promote mitophagy (41,45).…”

“…However, the precise role of Parkin in the induction of mitophagy has not been fully elucidated. To date, several mitochondrial proteins, voltage-dependent anion channel 1 (VDAC1) (8), mitofusin (a mitochondrial pro-fusion factor) (11,14,15), Bcl-2 (16), and Drp1 (17), have been shown to be ubiquitinated by Parkin. Ubiquitination of VDAC1 may recruit the autophagy adaptor p62, which interacts with microtubule-associated protein light chain 3 (LC3) on the autophagosomal membrane (8); however, the requirement of p62 remains controversial (18 -21).…”

A chemical genetic approach to probe the function of PINK1 in regulating mitochondrial dynamics

“…The PINK1-Parkin pathway has also been implicated in modulating mitochondrial fission/fusion dynamics by inducing ubiquitination of Drp1 or Mitofusins [1,14,15]. Indeed, in MEF cells expressing hPINK1 AS , mitochondria are predominantly fragmented (Supplementary information, Figure S1M).…”

Mitochondria dynamism: of shape, transport and cell migration

“…Indeed, it has been recently demonstrated, by pull-down assay and co-immunoprecipitation experiments, that the cytosolic e3-ubiquitin ligase Parkin directly interacts with DRP1 [22] to ubiquitinate it, so leading to its proteasome-dependent degradation. In this way, the ubiquitin-proteasome pathway can also influence mitochondrial morphology through modulation of DRP1 levels.…”