The p53-activated gene, PAG608, requires a zinc finger domain for nuclear localization and oxidative stress-induced apoptosis

Expression Profiling of Blood microRNAs 885, 361, and 17 in the Patients with the Parkinson's disease: Integrating Interaction Data to Uncover the Possible Triggering Age-Related Mechanisms

MicroRNAs (miRNAs) have been reported to contribute to the pathophysiology of the Parkinson’s disease (PD), an age related-neurodegenerative disorder. The aim of present study was to compare the expression profiles of a new set of candidate miRNAs related to aging and cellular senescence in peripheral blood mononuclear cells (PBMCs) obtained from the PD patients with healthy controls and then in the early and advanced stages of the PD patients with their controls to clarify whether their expression was correlated with the disease severity. We have also proposed a consensus-based strategy to interpret the miRNAs expression data to gain a better insight into the molecular regulatory alterations during the incidence of PD. We evaluated the miRNA expression levels in the PBMCs obtained from 36 patients with PD and 16 healthy controls by the reverse transcription-quantitative real-time PCR and their performance to discriminate the PD patients from the healthy subjects assessed using the receiver operating characteristic curve analysis. Also, we applied our consensus and integration approach to construct a deregulated miRNA-based network in PD with the respective targets and transcription factors, and the enriched gene ontology and pathways using the enrichment analysis approach were obtained. There was a significant overexpression of miR-885 and miR-17 and the downregulation of miR-361 in the PD patients compared to the controls. The blood expression of miR-885 and miR-17 tended to increase along with the disease severity. On the other hand, the lower levels of miR-361 in the early stages of the PD patients, as compared to controls, and its higher levels in the advanced stages of PD patients, as compared to the early stages of the PD patients, were observed. Combination of all three miRNAs showed an appropriate value of AUC (0.985) to discriminate the PD patients from the healthy subjects. Also, the deregulated miRNAs were linked to the known PD pathways and the candidate related target genes were presented. We revealed 3 candidate biomarkers related to aging and cellular senescence for the first time in the patients with PD. Our in-silico analysis identified candidate target genes and TFs, including those related to neurodegeneration and PD. Overall, our findings provided novel insights into the probable age-regulatory mechanisms underlying PD and a rationale to further clarify the role of the identified miRNAs in the PD pathogenesis.

Significant improvement of miRNA target prediction accuracy in large datasets using meta-strategy based on comprehensive voting and artificial neural networks

BACKGROUND

Identifying mRNA targets of miRNAs is critical for studying gene expression regulation at the whole-genome level. Multiple computational tools have been developed to predict miRNA:mRNA interactions. Nonetheless, many of these tools are developed in various small datasets, which each represent a limited sample space. Thus, the prediction accuracy of these tools has not been systematically validated at a larger scale. Accordingly, comparing the prediction accuracy of these tools and determining their applicability become challenging. In addition, the accuracy of these tools, especially in large datasets, needs to be improved for broader applications.

RESULTS

In this project, a large dataset containing more than 46,600 miRNA:mRNA interactions was assembled and split into eleven subsets based on the availability of prediction scores of four individual predictors, which are miRanda, miRDB, PITA, and TargetScan. In each of these subsets, the predictive results of four individual predictors were integrated using decision-tree based artificial neural networks to make the meta-prediction. The decision-tree is used here to sort the predictive results of four individual predictors, and artificial neural networks are applied to make meta-prediction based on the outputs of individual predictors. In the decision tree, dual-threshold and two-step significance-voting were incorporated, information gain was analysed to select threshold values. The prediction performance of this new strategy was improved significantly in most of the eleven datasets comparing to the individual predictors and other meta-predictors, such as ComiR, under multi-fold cross-validation, as well as in independent datasets. The overall improvement of prediction accuracy in independent datasets is at least 9 percentile points comparing to the other predictors, and the percentage of improvement of F1 and MCC scores is at least 40% compared to the other predictors.

CONCLUSIONS

The combination of dual-threshold, two-step significance-voting, and analysis of information gain is very effective in optimizing the outcome of decision-tree, and further integration with artificial neural networks is critical for further improving the performance of meta-predictor. A new pipeline based on this integration for miRNA target prediction has been developed. A strategy using outputs of individual predictors to reorganize large-scale miRNA:mRNA interaction dataset has also been validated and used to evaluate the prediction accuracy of predictors. The predictor is available at: https://github.com/xueLab/mirTarDANN ).

Recent advances in methamphetamine neurotoxicity mechanisms and its molecular pathophysiology

Methamphetamine (METH) is a sympathomimetic amine that belongs to phenethylamine and amphetamine class of psychoactive drugs, which are widely abused for their stimulant, euphoric, empathogenic, and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, METH produces persistent damage to dopamine and serotonin release in nerve terminals, gliosis, and apoptosis. This review summarized the numerous interdependent mechanisms including excessive dopamine, ubiquitin-proteasome system dysfunction, protein nitration, endoplasmic reticulum stress, p53 expression, inflammatory molecular, D₃ receptor, microtubule deacetylation, and HIV-1 Tat protein that have been demonstrated to contribute to this damage. In addition, the feasible therapeutic strategies according to recent studies were also summarized ranging from drug and protein to gene level.

Wig-1 regulates cell cycle arrest and cell death through the p53 targets FAS and 14-3-3σ

Wig-1, also known as ZMAT3, is a p53 target gene that encodes an RNA-binding zinc-finger protein involved in the regulation of mRNA stability through binding to AU-rich elements (AREs). We have used microarray analysis to identify novel Wig-1 target mRNAs. We identified 2447 transcripts with >fourfold differential expression between Wig-1 and control small interfering (si)RNA-treated HCT116 cells. Several p53 target genes were among the deregulated transcripts. We found that Wig-1 regulates FAS and 14-3-3σ mRNA independently of p53. We show that Wig-1 binds to FAS mRNA 3'-UTR and decreases its stability through an ARE in the 3'-UTR. Depletion of Wig-1 was associated with increased cell death and reduced cell cycle arrest upon DNA damage. Our results suggest a role of Wig-1 as a survival factor that directs the p53 stress response toward cell cycle arrest rather than apoptosis through the regulation of FAS and 14-3-3σ mRNA levels.

Dual role of the caspase enzymes in satellite cells from aged and young subjects

Satellite cell (SC) proliferation and differentiation have critical roles in skeletal muscle recovery after injury and adaptation in response to hypertrophic stimuli. Normal ageing hinders SC proliferation and differentiation, and is associated with increased expression of a number of pro-apoptotic factors in skeletal muscle. In light of previous studies that have demonstrated age-related altered expression of genes involved in SC antioxidant and repair activity, this investigation was aimed at evaluating the incidence of apoptotic features in human SCs. Primary cells were obtained from vastus lateralis of nine young (27.3±2.0 years old) and nine old (71.1±1.8 years old) subjects, and cultured in complete medium for analyses at 4, 24, 48, and 72 h. Apoptosis was assessed using AnnexinV/propidium iodide staining, the terminal deoxynucleotidyl transferase dUTP nick-end labelling technique, RT-PCR, DNA microarrays, flow cytometry, and immunofluorescence analysis. There was an increased rate of apoptotic cells in aged subjects at all of the experimental time points, with no direct correlation between AnnexinV-positive cells and caspase-8 activity. On the other hand, CASP2, CASP6, CASP7, and CASP9 and a number of cell death genes were upregulated in the aged SCs. Altogether, our data show age-related enhanced susceptibility of human SCs to apoptosis, which might be responsible for their reduced response to muscle damage.

Cytoplasmic expression, antibody production, and characterization of the novel zinc finger protein 637

Zinc finger protein 637 (zfp637), belonging to the Kruppel-like protein family, comprises one atypical C(2)H(2) and six consecutive typical zinc finger motifs. Based on the structural characterization of zfp637 and its location in the cell nucleus, we predict that zfp637 might function as a DNA-binding protein to regulate gene transcription. However, the absence of both a purified zfp637 protein and any commercial antibody for detecting it in cells and tissues has limited functional studies of zfp637 to date. Here, we developed and optimized an expression system by fusing zfp637 with glutathione S-transferase (GST) to achieve a maximal yield of soluble GST-zfp637 fusion protein in Escherichia coli BL21(DE3) cells. The yield was about 10 mg/l of the original bacterial culture. The recombinant GST-zfp637 fusion protein was purified and used for polyclonal antibody production in rabbits. In addition, we developed a method to remove the anti-GST antibody component and obtained a highly purified anti-zfp637 antibody, as demonstrated by an enzyme-linked immunosorbent assay. Western blotting showed that the anti-zfp637 antibody recognized not only the recombinant zfp637 protein but also endogenous zfp637 in several cell lines. The protein was localized mainly in the cell nucleus by immunofluorescence and immunohistochemistry. The expression levels of zfp637 mRNA and protein were significantly increased in NIH3T3 cells treated with 200 μM of H(2)O(2) in a time-dependent manner. The recombinant GST-zfp637 fusion protein and our purified anti-zfp637 antibody will help in elucidating the function of zfp637.

The LSD1-type zinc finger motifs of Pisum sativa LSD1 are a novel nuclear localization signal and interact with importin alpha

BACKGROUND

Genetic studies of the Arabidopsis mutant lsd1 highlight the important role of LSD1 in the negative regulation of plant programmed cell death (PCD). Arabidopsis thaliana LSD1 (AtLSD1) contains three LSD1-type zinc finger motifs, which are involved in the protein-protein interaction.

METHODOLOGY/PRINCIPAL FINDINGS

To further understand the function of LSD1, we have analyzed cellular localization and functional localization domains of Pisum sativa LSD1 (PsLSD1), which is a homolog of AtLSD1. Subcellular localization analysis of green fluorescent protein (GFP)-tagged PsLSD1 indicates that PsLSD1 is localized in the nucleus. Using a series of GFP-tagged PsLSD1 deletion mutants, we found that the three LSD1-type zinc finger motifs of PsLSD1 alone can target GFP to the nucleus, whereas deletion of the three zinc finger motifs or any individual zinc finger motif causes PsLSD1 to lose its nuclear localization, indicating that the three zinc finger motifs are necessary and sufficient for its nuclear localization. Moreover, site-directed mutagenesis analysis of GFP-tagged PsLSD1 indicates that tertiary structure and basic amino acids of each zinc finger motif are necessary for PsLSD1 nuclear localization. In addition, yeast two-hybrid, pull-down, and BiFC assays demonstrate that the three zinc finger motifs of PsLSD1 directly bind to importin α in vitro and in vivo.

CONCLUSIONS/SIGNIFICANCE

Our data demonstrate that the LSD1-type zinc finger motifs of PsLSD1 are a novel nuclear localization signal and directly bind to importin α, and suggest that the nuclear import of LSD1 may rely on the interaction between its zinc finger motifs and importin α. Moreover, the nuclear localization of PsLSD1 suggests that LSD1 may function as a transcription regulator involved in negatively regulating PCD.

The p53 target Wig-1: a regulator of mRNA stability and stem cell fate?

Wig-1 is a transcriptional target of the tumor suppressor p53 and encodes an unusual zinc-finger protein involved in post-transcriptional gene regulation. Wig-1 is expressed in all cell types investigated so far, with the highest levels in the brain, and is enriched in stem cells as compared with more differentiated cells of the same lineage. Wig-1 binds to both long double-stranded (ds) RNA and short microRNA-like dsRNA. We have shown that Wig-1 acts in a positive feedback loop that stabilizes p53 mRNA through an AU-rich element (ARE) in the p53 3'untranslated region. Our preliminary data indicate a more general effect of Wig-1 on ARE-containing mRNA. Here we shall summarize current knowledge about Wig-1 and discuss possible implications on p53 function and other cellular processes.

Induction of parkinsonism-related proteins in the spinal motor neurons of transgenic mouse carrying a mutant SOD1 gene

Amyotrophic lateral sclerosis is a progressive and fatal disease caused by selective death of motor neurons, and a number of these patients carry mutations in the superoxide dismutase 1 (SOD1) gene involved in ameliorating oxidative stress. Recent studies indicate that oxidative stress and disruption of mitochondrial homeostasis is a common mechanism for motor neuron degeneration in amyotrophic lateral sclerosis and the loss of midbrain dopamine neurons in Parkinson's disease. Therefore, the present study investigated the presence and alterations of familial Parkinson's disease-related proteins, PINK1 and DJ-1, in spinal motor neurons of G93ASOD1 transgenic mouse model of amyotrophic lateral sclerosis. Following onset of disease, PINK1 and DJ-1 protein expression increased in the spinal motor neurons. The activated form of p53 also increased and translocated to the nuclei of spinal motor neurons, followed by increased expression of p53-activated gene 608 (PAG608). This is the first report demonstrating that increased expression of PAG608 correlates with activation of phosphorylated p53 in spinal motor neurons of an amyotrophic lateral sclerosis model. These results provide further evidence of the profound correlations between spinal motor neurons of amyotrophic lateral sclerosis and parkinsonism-related proteins.

Beyond DNA: zinc finger domains as RNA-binding modules

Over the last 25 years, we have learned that many structural classes of zinc-binding domains (zinc fingers, ZFs) exist and it has become clear that the molecular functions of these domains are by no means limited to the sequence-specific recognition of double-stranded DNA. For example, ZFs can act as protein recognition or RNA-binding modules, and some domains can exhibit more than one function. In this chapter we describe the progress that has been made in understanding the role of ZF domains as RNA-recognition modules, and we speculate about both the prevalence of such functions and the prospects for creating designer ZFs that target RNA.

Identification of genes differentially expressed as result of adenovirus type 5- and adenovirus type 12-transformation

BACKGROUND

Cells transformed by human adenoviruses (Ad) exhibit differential capacities to induce tumours in immunocompetent rodents; for example, Ad12-transformed rodent cells are oncogenic whereas Ad5-transformed cells are not. The E1A gene determines oncogenic phenotype, is a transcriptional regulator and dysregulates host cell gene expression, a key factor in both cellular transformation and oncogenesis. To reveal differences in gene expression between cells transformed with oncogenic and non-oncogenic adenoviruses we have performed comparative analysis of transcript profiles with the aim of identifying candidate genes involved in the process of neoplastic transformation.

RESULTS

Analysis of microarray data revealed that a total of 232 genes were differentially expressed in Ad12 E1- or Ad5 E1-transformed BRK cells compared to untransformed baby rat kidney (BRK) cells. Gene information was available for 193 transcripts and using gene ontology (GO) classifications and literature searches it was possible to assign known or suggested functions to 166 of these identified genes. A subset of differentially-expressed genes from the microarray was further examined by real-time PCR and Western blotting using BRK cells immortalised by Ad12 E1A or Ad5 E1A in addition to Ad12 E1- or Ad5 E1-transformed BRK cells. Up-regulation of RelA and significant dysregulation of collagen type I mRNA transcripts and proteins were found in Ad-transformed cells.

CONCLUSION

These results suggest that a complex web of cellular pathways become altered in Ad-transformed cells and that Ad E1A is sufficient for the observed dysregulation. Further work will focus on investigating which splice variant of Ad E1A is responsible for the observed dysregulation at the pathway level, and the mechanisms of E1A-mediated transcriptional regulation.

Specific induction of PAG608 in cranial and spinal motor neurons of L-DOPA-treated parkinsonian rats

We identified p53-activated gene 608 (PAG608) as a specifically induced gene in striatal tissue of L-DOPA (100mg/kg)-injected hemi-parkinsonian rats using differential display assay. In the present study, we further examined morphological distribution of PAG608 in the central nervous system of L-DOPA-treated hemi-parkinsonian rats. PAG608 expression was markedly induced in fibers and neuronal cells of the lateral globus pallidus and reticular thalamic nucleus adjacent to internal capsule, specifically in the parkinsonian side of L-DOPA-treated models. The protein was also constitutively expressed in motor neurons specifically in either side of the pontine nucleus and motor nuclei of trigeminal and facial nerves. Furthermore, L-DOPA-induced PAG608 expression on motor neurons in the contralateral side of the ventral horn of the spinal cord and the lateral corticospinal tract without cell loss. The specific induction of PAG608 6-48h after L-DOPA injection in the extrapyramidal tracts, pyramidal tracts and corresponding lower motor neurons of the spinal cords suggests its involvement in molecular events in stimulated motor neurons. Taken together with the constitutive expression of PAG608 in the motor nuclei of cranial nerves, PAG608 may be a useful marker of stressed or activated lower motor neurons.

Suppression of p53-activated gene, PAG608, attenuates methamphetamine-induced neurotoxicity

The p53-activated gene 608 (PAG608) is a proapoptotic gene activated and regulated by p53 expression in oxidative stress-induced apoptosis of neuronal cells. In this study, we determined the role of PAG608 in methamphetamine-induced neurotoxicity. Treatment of mouse dopaminergic CATH.a cells with 2 mM methamphetamine increased PAG608 expression at 3h followed by increase in phosphorylated p53 expression. Transient transfection of PAG608 antisense cDNA or RNA interference using PAG608 small interfering RNA significantly attenuated the dose-dependent decrease in cell viability of CATH.a cells by methamphetamine (1-4 mM) exposure. In monoaminergic neuronal B65 cells, which contain serotonin rather than dopamine, methamphetamine-induced cell death was also significantly but partially protected by transient transfection of PAG608 antisense cDNA. Furthermore, cell death of PC12 cells produced by methamphetamine (1-5 mM) was almost completely prevented by stable expression of PAG608 antisense cDNA, compared with significant reduction of cell viability in control PC12 cells. Our results showed that suppression of PAG608 using transient and stable transfection with PAG608 antisense cDNA or small interfering RNA attenuates methamphetamine-induced death of various monoaminergic neuronal cells, suggesting that methamphetamine neurotoxicity in monoaminergic cells is related, at least in part, to induction of PAG608 expression.

JAZ mediates G1 cell-cycle arrest and apoptosis by positively regulating p53 transcriptional activity

We previously identified JAZ as a novel zinc finger (ZF) protein by screening a murine interleukin-3 (IL-3)-dependent NFS/N1.H7 myeloid cell cDNA library. JAZ is a member of a new class of ZFPs that is evolutionarily conserved and preferentially binds to dsRNA, but its function was unknown. Now, we report that the stress of IL-3 growth factor withdrawal up-regulates JAZ expression in hematopoietic cells in association with p53 activation and induction of cell death. Biochemical analysis reveals that JAZ associates with p53 to stimulate its transcriptional activity in p53-expressing cells, but not in p53-null cells unless complemented with p53. JAZ functions to mediate G1 cell-cycle arrest followed by apoptosis in a p53-dependent mechanism that is associated with up-regulation of p21 and BAX, dephosphorylation of Rb, and repression of cyclin A. Of importance, siRNA "knockdown" of endogenous JAZ inhibits p53 transcriptional activity, decreases the G1/G0 population, and attenuates stress-induced cell death. While JAZ directly binds p53 in vitro in a mechanism requiring p53's C-terminal regulatory domain but independent of dsRNA, the dsRNA-binding ZF domains are required for JAZ's stimulatory role of p53 in vivo by dictating its nuclear localization. Thus, JAZ is a novel negative regulator of cell growth by positively regulating p53.

Molecular basis of 6-hydroxydopamine-induced caspase activations due to increases in oxidative stress in the mouse striatum

To clarify the possible role of in the in vivo toxic effects of 6-hydroxydopamine (6-OHDA), especially caspase activations, we examined its effects on striatal lipid peroxidation (LPO) and caspase activations in 6-OHDA-lesioned mice. Both dopamine (DA) levels and DA turnover were significantly changed by the 6-OHDA i.c.v. injection compared with the pre-injection level in the striatum. In addition, the striatal glutathione (GSH) content fluctuated and was significantly decreased both at 3 and 14 days after 6-OHDA i.c.v. injection. Moreover, superoxide dismutase (SOD) activity at 7 days after 6-OHDA i.c.v. injection was transiently and significantly increased compared with the pre-injection level. The levels of thiobarbituric acid-reactive substances (TBA-RS) were significantly increased at 1, 3 and 14 days. 6-OHDA significantly increased the activities of all three caspases, except for the caspase-3 activity at 7 days throughout the experimental period compared with the pre-injection level. In conclusion, 6-OHDA-induced dopaminergic dysfunction is mainly due to caspase activations by increases in oxidative stress in the mouse striatum.

Puma and p53 play required roles in death evoked in a cellular model of Parkinson disease

6-Hydroxydopamine (6-OHDA) is widely used in vivo and in vitro to mimic the selective neuronal degeneration that characterizes Parkinson disease (PD). To uncover candidate genes that may mediate neuron death in PD, we previously used SAGE to identify transcripts that are rapidly induced by 6-OHDA in neuronally differentiated PC12 cells. Among induced pro-apoptotic genes was that encoding the BH3-only protein PUMA. Here, we confirm that 6-OHDA induces both PUMA mRNA and protein. 6-OHDA additionally induced Bim, another pro-apoptotic BH3-only protein. Using specific siRNAs, we demonstrate that PUMA, but not Bim, is required for death evoked by 6-OHDA. PUMA is a target of p53, a transcription factor activated by 6-OHDA. Involvement of p53 in 6-OHDA evoked death was confirmed by the protective actions of a DN p53 and pifithrin alpha, inhibitors of p53 signaling. Our findings thus indicate that p53 and PUMA play required roles in a cellular model of PD.

The intracrine hypothesis: an update

The intracellular actions of peptide hormones, growth factors, as well as of extracellular-signaling enzymes and DNA-binding proteins, either within target cells or within their cells of synthesis has been called intracrine action. Although these intracrine moieties are structurally diverse, they share certain characteristics of synthesis and function. This has given rise to the development of a theory of intracrine action which permits testable predictions to be made regarding the functioning of these peptides/proteins. Here the intracrine hypothesis is briefly described and then recent experimental findings which bear on predictions made earlier on the basis of the theory are discussed. These findings provide new support for the intracrine hypothesis.

Prednisolone inhibits proliferation of cultured pulmonary artery smooth muscle cells of patients with idiopathic pulmonary arterial hypertension

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is associated with proliferation of smooth muscle cells (SMCs) in small pulmonary arteries. There is no therapy that specifically inhibits SMC proliferation. Recent studies reported that prednisolone (PSL) inhibits the postangioplasty proliferation of SMCs in atherosclerotic arteries. In this study, we tested the hypothesis that PSL has antiproliferative effects on pulmonary artery SMCs of patients with IPAH.

METHODS AND RESULTS

Pulmonary artery SMCs were harvested from the pulmonary arteries of 6 patients with IPAH who underwent lung transplantation. Control SMCs were obtained from 5 patients with bronchogenic carcinoma who underwent lung lobectomy. After incubation in the presence of platelet-derived growth factor (PDGF), PSL was added at different concentrations and cell proliferation was assessed by 3H-thymidine incorporation. PSL (2x10(-4) and 2x10(-3) mol/L) significantly inhibited PDGF-stimulated proliferation (P<0.05) of SMCs from patients with IPAH but did not affect cell viability of SMCs, as confirmed by trypan blue staining. In cell cycle analysis using a microscope-based multiparameter laser scanning cytometer, PSL inhibited the progression of SMCs from G(0)/G1 to the S phase. This inhibition was associated with increased p27 expression level. PSL (2x10(-4) mol/L) also inhibited PDGF-induced SMC migration.

CONCLUSIONS

Our results indicate that PSL has an antiproliferative effect on cultured SMCs of pulmonary arteries from patients with IPAH and suggest that PSL may be potentially useful therapeutically in patients with IPAH.

Analysis of gene expression changes in a cellular model of Parkinson disease

We employed Serial Analysis of Gene Expression to identify transcriptional changes in a cellular model of Parkinson Disease (PD). The model consisted of neuronally differentiated PC12 cells compared before and after 8 hours' exposure to 6-hydroxydopamine. Approximately 1200 transcripts were significantly induced by 6-OHDA and approximately 500 of these are currently matched to known genes. Here, we categorize the regulated genes according to known functional activities and discuss their potential roles in neuron death and survival and in PD. We find induction of multiple death-associated genes as well as many with the capacity for neuroprotection. This suggests that survival or death of individual neurons in PD may reflect an integrated response to both protective and destructive gene changes. Our findings identify a number of regulated genes as candidates for involvement in PD and therefore as potential targets for therapeutic intervention. Such intervention may include both inhibiting the induction/activity of death-promoting genes and enhancing those with neuroprotective activity.

Parkin attenuates manganese-induced dopaminergic cell death

Manganese as environmental factor is considered to cause parkinsonism and induce endoplasmic reticulum stress-mediated dopaminergic cell death. We examined the effects of manganese on parkin, identified as the gene responsible for familial Parkinson's disease, and the role of parkin in manganese-induced neuronal cell death. Manganese dose-dependently induced cell death of dopaminergic SH-SY5Y and CATH.a cells and cholinergic Neuro-2a cells, and that the former two cell types were more sensitive to manganese toxicity than Neuro-2a cells. Moreover, manganese increased the expression of endoplasmic reticulum stress-associated genes, including parkin, in SH-SY5Y cells and CATH.a cells, but not in Neuro-2a cells. Treatment with manganese resulted in accumulation of parkin protein in SH-SY5Y cells and its redistribution to the perinuclear region, especially aggregated Golgi complex, while in Neuro-2a cells neither expression nor redistribution of parkin was noted. Manganese showed no changes in proteasome activities in either cell. Transient transfection of parkin gene inhibited manganese- or manganese plus dopamine-induced cell death of SH-SY5Y cells, but not of Neuro-2a cells. Our results suggest that the attenuating effects of parkin against manganese- or manganese plus dopamine-induced cell death are dopaminergic cell-specific compensatory reactions associated with its accumulation and redistribution to perinuclear regions but not with proteasome system.