DJ-1 is a multifunctional protein that plays roles in transcriptional regulation and antioxidative stress, and loss of its function is thought to result in the onset of Parkinson's disease (PD). Here, we report that DJ-1 was sumoylated on a lysine residue at amino-acid number 130 (K130) by PIASxa or PIASy. The K130 mutation abrogated all of the functions of DJ-1, including ras-dependent transformation, cell growth promotion and anti-UV-induced apoptosis activities. Sumoylation of DJ-1 was increased after UV irradiation concomitant with a pI shift to an acidic point of DJ-1. Furthermore, L166P, a mutant DJ-1 found in PD patients, and K130RX, an artificial mutant containing four mutations in DJ-1, were improperly sumoylated, and they became insoluble, partly localized in the mitochondria and degraded by the proteasome system. Both L166P-expressing cells and DJ-1-knockdown cells were found to be highly susceptible to UV-induced cell apoptosis.

Parkinson's disease (PD) is caused by neuronal cell death, and oxidative stress and mitochondrial dysfunction are thought to be responsible for onset of PD. DJ-1, a causative gene product of a familial form of Parkinson's disease, PARK7, plays roles in transcriptional regulation and anti-oxidative stress. The possible mitochondrial function of DJ-1 has been proposed, but its exact function remains unclear. In this study, we found that DJ-1 directly bound to NDUFA4 and ND1, nuclear and mitochondrial DNA-encoding subunits of mitochondrial complex I, respectively, and was co-localized with complex I and that complex I activity was reduced in DJ-1-knockdown NIH3T3 and HEK293cells. These findings suggest that DJ-1 is an integral mitochondrial protein and that DJ-1 plays a role in maintenance of mitochondrial complex I activity.

DJ-1 is a novel oncogene and also a causative gene for familial Parkinson’s disease (park7). DJ-1 has multiple functions that include transcriptional regulation, anti-oxidative reaction and chaperone and mitochondrial regulation. Mitochondrial dysfunction is observed in DJ-1-knockout mice and fry, and mitochondrial DJ-1 is more protective against oxidative stress-induced cell death. Although translocation of DJ-1 into mitochondria is enhanced by oxidative stress that leads to oxidation of cysteine 106 (C106) of DJ-1, the characteristics of mitochondrial DJ-1 and the mechanism by which DJ-1 is translocated into mitochondria are poorly understood. In this study, immunostaining, co-immunoprecipitation, cell fractionation and pull-down experiments showed that mutants of glutamine 18 (E18) DJ-1 are localized in mitochondria and do not make homodimers. Likewise, DJ-1 with mutations of two cysteines located in the dimer interface, C46S and C53A, and pathogenic mutants, M26I and L166P DJ-1, were found to be localized in mitochondria and not to make homodimers. Mutant DJ-1 harboring both E18A and C106S, in which C106 is not oxidized, was also localized in mitochondria, indicating that oxidation of C106 is important but not essential for mitochondrial localization of DJ-1. It should be noted that E18A DJ-1 was translocated from mitochondria to the cytoplasm when mitochondrial membrane potential was reduced by treatment of cells with CCCP, an uncoupler of the oxidative phosphorylation system in mitochondria. Furthermore, deletion or substitution of the N-terminal 12 amino acids in DJ-1 resulted in re-localization of E18A, M26I and L166P DJ-1 from mitochondria into the cytoplasm. These findings suggest that a monomer and the N-terminal 12 amino acids are necessary for mitochondrial localization of DJ-1 mutants and that conformation change induced by C106 oxidation or by E18 mutation leads to translocation of DJ-1 into mitochondria.

Parkinson disease (PD) is caused by loss of dopamine, which is synthesized from tyrosine by two enzymes, tyrosine hydroxylase (TH) and 4-dihydroxy-L-phenylalanine decarboxylase (DDC).DJ-1 is a causative gene for the familial form of PD, but little is known about the roles of DJ-1 in dopamine synthesis. In this study, we found that DJ-1 directly bound to TH and DDC and positively regulated their activities in human dopaminergic cells. Mutants of DJ-1 found in PD patients, including heterozygous mutants, lost their activity and worked as dominant-negative forms toward wild-type DJ-1. When cells were treated with H 2 O 2 , 6-hydroxydopamine, or 1-methyl-4-phenylpyridinium, changes in activities of TH and DDC accompanied by oxidation of cysteine 106 of DJ-1 occurred. It was found that DJ-1 possessing Cys-106 with SH and SOH forms was active and that DJ-1 possessing Cys-106 with SO 2 H and SO 3 H forms was inactive in terms of stimulation of TH and DDC activities. These findings indicate an essential role of DJ-1 in dopamine synthesis and contribution of DJ-1 to the sporadic form of PD. Parkinson disease (PD)2 is a neurodegenerative disease that occurs by reduction of the dopamine level through dopaminergic cell death in the substantia nigra. Genetic and environmental factors are thought to be triggers for the onset of PD, but the precise molecular mechanisms are still not known. Dopamine is synthesized by the following two steps: tyrosine is converted to L-DOPA by tyrosine hydroxylase (TH) and then L-DOPA is converted to dopamine by L-dopa decarboxylase (DDC). TH is therefore a key enzyme for dopamine synthesis and is used as a marker for dopaminergic neurons.DJ-1 was first identified by our group as a novel candidate of the oncogene that transformed mouse NIH3T3 cells in cooperation with activated ras (1). Deletion and point (L166P) mutations of DJ-1 have been shown to be responsible for onset of familial Parkinson disease, PARK7 (2), and other homozygous and heterozygous mutations of DJ-1 have been identified in patients with familial or sporadic Parkinson disease (3-6). DJ-1 is a multifunctional protein and plays roles in transcriptional regulation and anti-oxidative stress function, and loss of its functions is thought to lead to the onset of Parkinson disease and cancer. DJ-1 has three cysteine residues at positions 46, 53, and 106 (Cys-46, Cys-53, and Cys-106, respectively), and these cysteine residues are oxidized after cells receive oxidative stress, resulting in scavenging of reactive oxidative species (7-12). Although DJ-1 does not directly bind to DNA, DI-1 acts as a co-activator to activate various transcription factors, including the androgen receptor and p53 tumor suppressor, PSF and Nrf2, by sequestering their inhibitory factors (13-18). The anti-oxidative stress function of DJ-1 is therefore thought to be carried out both by self-oxidation of cysteine residues and by activation of redox-related genes.It has been reported that PSF, a transcription repressor, binds to the promoter region of the TH gene...

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