Language：English   Publishing type：Research paper (scientific journal)  

The nucleolus serves a multifaceted role encompassing not only rRNA transcription and ribosome synthesis, but also the intricate orchestration of cell cycle regulation and the modulation of cellular senescence. G-patch domain containing 4 (GPATCH4) stands as one among the nucleolar proteins; however, its functional significances remain still unclear. In order to elucidate the functions of GPATCH4, we examined the effects of its dysfunction on cellular proliferation, alterations in nucleolar architecture, apoptotic events, and cellular senescence. Through experimentation conducted on cultured neuroblastoma SH-SY5Y cells, the reduction of GPATCH4 caused inhibition of cellular proliferation, concurrently fostering escalated apoptotic susceptibilities upon exposure to high-dose etoposide. In the realm of nucleolar morphology comparisons, a discernible decline was noted in the count of nucleoli per nucleus, concomitant with a significant expansion in the area occupied by individual nucleoli. Upon induction of senescence prompted by low-dose etoposide, GPATCH4 knockdown resulted in decreased cell viability and increased expression of senescence-associated markers, namely senescence-associated β-galactosidase (SA-β-GAL) and p16. Furthermore, GPATCH4 dysfunction elicited alterations in the gene expression profile of the ribosomal system. In sum, our findings showed that GPATCH4 is a pivotal nucleolar protein that regulates nucleolar morphology and is correlated with cell viability.

DOI： 10.1016/j.bbrc.2023.149384

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

α-Synuclein accumulates in Lewy bodies, and this accumulation is a pathological hallmark of Parkinson's disease (PD). Previous studies have indicated a causal role of α-synuclein in the pathogenesis of PD. However, the molecular and cellular mechanisms of α-synuclein toxicity remain elusive. Here, we describe a novel phosphorylation site of α-synuclein at T64 and the detailed characteristics of this post-translational modification. T64 phosphorylation was enhanced in both PD models and human PD brains. T64D phosphomimetic mutation led to distinct oligomer formation, and the structure of the oligomer was similar to that of α-synuclein oligomer with A53T mutation. Such phosphomimetic mutation induced mitochondrial dysfunction, lysosomal disorder, and cell death in cells and neurodegeneration in vivo, indicating a pathogenic role of α-synuclein phosphorylation at T64 in PD.

DOI： 10.1073/pnas.2214652120

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVES: Parkinson's disease is a neurodegenerative disorder that causes motor and nonmotor symptoms due to the loss of dopaminergic nerves and is characterized by the presence of Lewy bodies, which are mainly composed of α-synuclein. Glucosylceramidase beta (GBA), which is a causative gene of autosomal recessive Gaucher disease, is also known to be a risk gene for Parkinson's disease. In this study, we tried to detect synergistic effects of α-synuclein accumulation and gba depletion on dopaminergic neurodegeneration in zebrafish. METHODS: We generated a transgenic line of zebrafish overexpressing the A53T α-synuclein and gba mutant fish, and analyzed pathologies of α-synuclein aggregation and neurodegeneration. RESULTS: Zebrafish overexpressing the A53T α-synuclein did not exhibit α-synuclein aggregate formation. After the loss of gba function in this mutant α-synuclein transgenic line, we observed the marked presence of α-synuclein aggregates. Loss of gba function in zebrafish resulted in dopaminergic and noradrenergic neurodegeneration but this level of neurodegeneration was not exacerbated by overexpression of mutant α-synuclein. CONCLUSIONS: These results indicate that loss of gba function was sufficient to generate a neurodegenerative phenotype in zebrafish regardless of the expression of α-synuclein.

DOI： 10.1097/WNR.0000000000001788

PubMed

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Publishing type：Research paper (scientific journal)  

The presence of ectopic DNA in the cytoplasm induces inflammation and cell death. It has been widely reported that leakage of nuclear DNA into the cytoplasm can mainly be sensed by cyclic GMP-AMP synthase (cGAS). We recently reported that mitochondria-derived cytoplasmic double-stranded DNA (dsDNA) that has escaped lysosomal degradation induces significant cytotoxicity in cultured cells and in vivo. Cytoplasmic mitochondrial DNA is assumed to be involved in various diseases and disorders, and more and more papers have been published confirming this. On the other hand, the current method for evaluating mitochondrial DNA in the cytoplasm may not be quantitative. Here, we introduce in detail a method to evaluate ectopic mitochondrial DNA in cells. This method is useful in basic research as well as in the study of aging, Parkinson’s disease, Alzheimer’s disease, heart failure, autoimmune diseases, cancer, and other conditions.

DOI： 10.3390/cimb44030080

Scopus

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

<title>Abstract</title>Mitochondrial dysfunction and lysosomal dysfunction have been implicated in Parkinson’s disease (PD), but the links between these dysfunctions in PD pathogenesis are still largely unknown. Here we report that cytosolic dsDNA of mitochondrial origin escaping from lysosomal degradation was shown to induce cytotoxicity in cultured cells and PD phenotypes in vivo. The depletion of PINK1, GBA and/or ATP13A2 causes increases in cytosolic dsDNA of mitochondrial origin and induces type I interferon (IFN) responses and cell death in cultured cell lines. These phenotypes are rescued by the overexpression of DNase II, a lysosomal DNase that degrades discarded mitochondrial DNA, or the depletion of IFI16, which acts as a sensor for cytosolic dsDNA of mitochondrial origin. Reducing the abundance of cytosolic dsDNA by overexpressing human DNase II ameliorates movement disorders and dopaminergic cell loss in gba mutant PD model zebrafish. Furthermore, IFI16 and cytosolic dsDNA puncta of mitochondrial origin accumulate in the brain of patients with PD. These results support a common causative role for the cytosolic leakage of mitochondrial DNA in PD pathogenesis.

DOI： 10.1038/s41467-021-23452-x

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Other Link： http://www.nature.com/articles/s41467-021-23452-x