Parkin Ubiquitinates and Promotes the Degradation of RanBP2

Abstract

Parkinson disease (PD) is a common neurodegenerative disorder, which involves the deterioration of dopaminergic neurons in the pars compacta of the substantia nigra. The etiology of PD is still unknown, but recent identification of mutations in familial cases of PD has advanced the understanding of the molecular mechanisms of this neurological disease. Mutations in the parkin gene, which encodes for ubiquitin-protein ligase (E3), have been implicated in autosomal recessive juvenile Parkinsonism, an early onset and common familial form of PD. Here we reported that Parkin selectively binds to RanBP2, which is localized in the cytoplasmic filament of the nuclear pore complex and belongs to the small ubiquitin-related modifier E3 ligase family. We also demonstrated that RanBP2 becomes a target for Parkin E3 ubiquitin-ligase and is processed via Parkin-mediated ubiquitination and subsequent proteasomal degradation. Furthermore, Parkin controls the intracellular levels of sumoylated HDAC4, as a result of the ubiquitination and degradation of RanBP2. Our findings suggested that the intracellular levels of RanBP2 and its functional activity may be modulated by Parkinmediated ubiquitination and proteasomal pathways. Parkinson disease (PD)2 is a major neurodegenerative disease characterized by a distinct set of movement disorders, including muscle rigidity, tremor, and bradykinesia (1). In PD, the level of dopamine is decreased in the striatum, most severely in the putamen. This is largely a result of the deterioration of dopaminergic neurons in the substantia nigra pars compacta (2-4). The etiology of PD remains poorly understood, but several genetic loci have been implicated in the pathogenesis of familial forms of PD. First, two missense mutations of ␣-synuclein have been linked to a rare dominant form of PD (5). Second, parkin has been identified as the causative gene of early onset autosomal recessive juvenile parkinsonism (AR-JP) (6), and a missense mutation in the ubiquitin (Ub) C-terminal hydrolase L1 appears to be responsible for a dominant form of PD (7). Most recently, mutations in DJ-1 and PTENinduced putative kinase-1 have been correlated with the incidences of familial PD (8, 9).The structure of Parkin contains a C-terminal RING-IBR-RING motif and an N-terminal region with homology to ubiquitin (10 -12). Proteins destined to degrade in the proteasomes are subject to covalent modification by ubiquitin as a small protein tag. Ubiquitination proceeds through a sequential enzymatic reaction composed of ubiquitinactivating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin-protein ligase (E3) (13). Based on the previous findings that numerous proteins with RING finger motifs have E3 ubiquitin-ligase activity, several studies have revealed that Parkin has an ubiquitin E3 ligase activity. The exquisite specificity for the proteins to be ubiquitinated is usually determined by a diverse family of E3s with a specific E2.Based on the functional role of Parkin, it can be surmised that the loss of Parkin resul...

Cytosolic p53 inhibits Parkin-mediated mitophagy and promotes mitochondrial dysfunction in the mouse heart

“…Mutations in the RING2 domain abolished E3 activity of Parkin and other mutations in the RING0 domain were important for the redistribution of Parkin to the damaged mitochondria 43 , consistent with our findings in which cytosolic p53 interacted with the RING0 domain to disturb Parkin translocation. RING0-mediated substrate interactions have been observed in several studies with the K161N mutation 44,45 . Among these proteins, BAG5 (bcl-2-associated athanogene 5), a BAG family member, directly interacted with Parkin residues 77-217 (including RING0) in combination with chaperone Hsp70.…”

Identification of a Novel Zn2+-binding Domain in the Autosomal Recessive Juvenile Parkinson-related E3 Ligase Parkin

“…The observation that K161N affects substrate interactions mediated by the RING0 domain is supported by several studies. Parkin interaction with the E3 Sumo ligase RanBP2 utilizes residues 78 -170 of parkin and has been proposed to mediate RanBP2 ubiquitination by parkin and parkin sumoylation via RanBP2 (59,60). This region coincides with the first zinc-binding motif in RING0.…”

“…This region coincides with the first zinc-binding motif in RING0. The interaction results in the ubiquitination and degradation of RanBP2, which reduces sumoylation of the RanBP2 substrate HDAC4 involved in cell growth and differentiation (59). The RanBP2-induced sumoylation of parkin has been shown to occur by selective association of SUMO-1 and parkin, resulting in enhanced parkin auto-ubiquitination and shuttling of parkin to the nucleous (60).…”

The PINK1/Parkin pathway regulates mitochondrial morphology

“…Although a number of substrates of PINK1 and Parkin have been described, these advances have led to dramatically varying models of pathogenesis (5,(14)(15)(16)(17)(18)(19), making it unclear precisely how PINK1 and Parkin influence neuronal integrity. Genetic studies of highly conserved Drosophila orthologs of parkin and PINK1 indicate that PINK1 acts upstream of Parkin in a common pathway that influences the integrity of flight muscle, sperm, and a subset of dopaminergic neurons in the brain (20)(21)(22)(23)(24).…”