Project description:Using longitudinal metabolic labeling in a knock-out mouse model we assessed the effects of parkin insufficiency on the half-lives of mitochondrial proteins in vivo.
Project description:Purpose: The E3 ubiquitin ligase Parkin is a well-characterized regulator of mitochondrial autophagy (mitophagy); however, it is becoming increasingly appreciated to perform additional roles in various compartments of the cell. Our laboratory confirmed the presence of Parkin in the nucleus of various tissues (biochemical fractionations) and cell types (immunofluorescent imaging). Hypoxia-induced nuclear translocation of Parkin occured independent of the mitophagy regulator PINK1, and Parkinson's disease-associated mutants were restricted from the nuclueus. Accordingly, we inserted a nuclear localization sequence (NLS) at the n-terminus of Parkin and overexpressed both NLS Parkin and the wild-type protein in HeLa cells cultured at normoxia and hypoxia. Next-generation RNA-sequencing (RNA-seq) was used to determine the effect of nuclear Parkin on cellular transcription. Methods: mCherry-tagged NLS and wild-type Parkin were overexpressed in HeLa cells. Differential expression analyses were performed on Parkin vs. mCherry control cells and NLS Parkin vs. mCherry control cells at normoxia and following 12hr of hypoxia (n=3/group/condition). Paired-end sequencing was performed using the HiSeq4000. FastQC v0.11.3 was used for quality control, Trimmomatic v0.36 was used to trim reads which were aligned to the human genome (GRCh37.p13) using the STAR aligner v2.5.3a. Read quantification was performed with RSEM v 1.3.0 and the Gencode release 19. The R BioConductor packages edgeR and limma were used to implement the limma-voom method for differential expression analysis. Results: During normoxia, Parkin had no effect on basal transcription; however, overexpression of NLS Parkin was associated with 168 differentially expressed genes (DEGs: fold-change </= 1.5, FDR < 0.05) relative to mCherry control cells. Following hypoxia, the transcriptome associated with the overexpression of wild-type Parkin more closely resembled that of NLS Parkin. Along these lines, Parkin overexpression during hypoxia coincided with a total of 158 DEGs, 37% of which were shared with NLS Parkin. Overlapping and shared DEGs among Parkin and NLS Parkin were implicated in cellular metabolism, HIF1 signaling and survival. Our follow up co-immunoprecipitation and real-time quantitative PCR studies demonstrated that Parkin interacts with the Estrogen Related Receptor Alpha (ERRa) to promote the induction of its downstream target genes. Conclusions: Nuclear translocation of Parkin is a novel means by which this cytoprotective protein contributes to cellular homeostasis and especially critical during hypoxia.
Project description:Mutations in the parkin gene, which encodes a ubiquitin ligase, are a major genetic cause of parkinsonism. Interestingly, parkin also plays a role in cancer as a putative tumor suppressor, and the gene is frequently targeted by deletion and inactivation in human malignant tumors. Here, we investigated a potential tumor suppressor role for parkin in gliomas. We found that parkin expression was dramatically reduced in glioma cells. Restoration of parkin expression promoted G1 phase cell cycle arrest and mitigated the proliferation rate of glioma cells in vitro and in vivo. Notably, parkin-expressing glioma cells showed a reduction in levels of cyclin D1, but not cyclin E, and a selective downregulation of Akt serine-473 phosphorylation and VEGF receptor levels. In accordance, cells derived from a parkin null mouse model exhibited increased levels of cyclin D1, VEGF receptor and Akt phosphorylation and divided significantly faster when compared with wild type cells, with suppressionof these changes following parkin re-introduction. Clinically, analysis of parkin pathway activation was predictive for the survival outcome of glioma patients. Taken together, our study provides mechanistic insight into the tumor suppressor function of parkin in brain tumors, and suggests that measurement of parkin pathway activation may be used clinically as a prognostic tool in brain tumor patients.
Project description:Dysfunctional Parkin-mediated mitophagic culling of senescent or damaged mitochondria is a major pathological process underlying Parkinson disease and a potential genetic mechanism of cardiomyopathy. Despite epidemiological associations between Parkinson disease and heart failure, the role of Parkin and mitophagic quality control in maintaining normal cardiac homeostasis is poorly understood.We used germline mutants and cardiac-specific RNA interference to interrogate Parkin regulation of cardiomyocyte mitochondria and examine functional crosstalk between mitophagy and mitochondrial dynamics in Drosophila heart tubes. 5 wild-type mouse hearts; 4 germline Parkin knockout mouse hearts Please note that the mouse cardiac examples were an adjunct to the Drosophila studies that comprised most of the associated publication. However, mRNA-sequencing was only performed on the mouse samples, not the Drosophila heart tubes.
Project description:Dysfunctional Parkin-mediated mitophagic culling of senescent or damaged mitochondria is a major pathological process underlying Parkinson disease and a potential genetic mechanism of cardiomyopathy. Despite epidemiological associations between Parkinson disease and heart failure, the role of Parkin and mitophagic quality control in maintaining normal cardiac homeostasis is poorly understood.We used germline mutants and cardiac-specific RNA interference to interrogate Parkin regulation of cardiomyocyte mitochondria and examine functional crosstalk between mitophagy and mitochondrial dynamics in Drosophila heart tubes.
Project description:Analysis of whole genome gene expression in control and PARKIN patient lines. The hypothesis tested in the present study was that the deficient of PARKIN expression affects multiple pathways. Results provide important information on relationship between PARKIN and mitochondria related gene expression.
Project description:Loss-of-function variants in the PRKN gene encoding the ubiquitin E3 ligase PARKIN cause autosomal recessive early-onset Parkinson’s disease (PD). Extensive in vitro and in vivo studies have reported that PARKIN is involved in multiple pathways of mitochondrial quality control, including mitochondrial degradation and biogenesis. However, these findings are surrounded by substantial controversy due to conflicting experimental data. In addition, the existing PARKIN-deficient mouse models have failed to faithfully recapitulate PD phenotypes. Therefore, we have investigated the mitochondrial role of PARKIN during ageing and in response to stress by employing a series of conditional Parkin knockout mice. We report that PARKIN loss does not affect oxidative phosphorylation (OXPHOS) capacity and mitochondrial DNA (mtDNA) levels in the brain, heart, and skeletal muscle of aged mice. We also demonstrate that PARKIN deficiency does not exacerbate the brain defects and the pro-inflammatory phenotype observed in mice carrying high levels of mtDNA mutations. To rule out compensatory mechanisms activated during embryonic development of Parkin-deficient mice, we generated a mouse model where loss of PARKIN was induced in adult dopaminergic (DA) neurons. Surprisingly, also these mice did not show motor impairment or neurodegeneration, and no major transcriptional changes were found in isolated midbrain DA neurons. Finally, we report a patient with compound heterozygous PRKN pathogenic variants that lacks PARKIN and has developed PD. The PARKIN deficiency did not impair OXPHOS activities or induce mitochondrial pathology in skeletal muscle from the patient. Altogether, our results argue that PARKIN is dispensable for OXPHOS function in adult mammalian tissues.
Project description:More than half of disease-causing missense variants are thought to lead to protein degradation, but the molecular mechanism of how these variants are recognized by the cell remains enigmatic. To approach this issue we have applied deep mutational scanning experiments to test the degradation of thousands of missense protein variants in large multiplexed experiments in cultured human cells. As a model protein we selected the ubiquitin-protein ligase Parkin, where known missense variants result in an autosomal recessive early onset Parkinsonism. The resulting mutational map comprises 9219 out of the 9300 (>99%) possible single-amino-acid substitution and nonsense Parkin variants. With a few notable exceptions, the majority of the destabilizing mutations are located within the structured domains of the protein, while the flexible linker regions are more tolerant to mutations. The cellular abundance data correlate with Parkin structural stability, evolutionary conservation, and separates known disease-linked variants from benign variants. Systematic mapping of degradation signals (degrons) shows that inherent primary degrons in Parkin largely overlap with regions that are highly sensitive to mutations. We identify a degron region proximal to the ACT element, which is enhanced by substitutions to hydrophobic residues. The vast majority of unstable Parkin variants are degraded through the ubiquitin-proteasome system and are stabilized at lowered temperatures. In conclusion, in addition to providing a diagnostic tool for rare genetic disorders, deep mutational scanning technologies have the potential to reveal both protein specific and general information on the specificity of the protein quality control network and the ubiquitin-proteasome system.
Project description:Parkin is an E3 ubiquitin ligase belonging to the RING-between-RING family. Mutations in the Parkin-encoding gene PARK2 are associated with familial Parkinson’s Disease. Here, we investigate the interplay between Parkin / Parkin-S65P and the inflammatory cytokine-induced ubiquitin-like modifier FAT10.
Project description:To provide an insight into the molecular mechanism by which parkin deficiency contributes to hepatocarcinogenesis, we analyzed gene expression profiles of nontumorous and tumorous liver tissues from parkin–/– mice using cDNA microarray analyses. Keywords: genetic alteration