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Senescence and impaired DNA damage responses in alpha-synucleinopathy models.

ABSTRACT: α-Synuclein is a crucial element in the pathogenesis of Parkinson's disease (PD) and related neurological diseases. Although numerous studies have presented potential mechanisms underlying its pathogenesis, the understanding of α-synuclein-mediated neurodegeneration remains far from complete. Here, we show that overexpression of α-synuclein leads to impaired DNA repair and cellular senescence. Transcriptome analysis showed that α-synuclein overexpression led to cellular senescence with activation of the p53 pathway and DNA damage responses (DDRs). Chromatin immunoprecipitation analyses using p53 and γH2AX, chromosomal markers of DNA damage, revealed that these proteins bind to promoters and regulate the expression of DDR and cellular senescence genes. Cellular marker analyses confirmed cellular senescence and the accumulation of DNA double-strand breaks. The non-homologous end joining (NHEJ) DNA repair pathway was activated in α-synuclein-overexpressing cells. However, the expression of MRE11, a key component of the DSB repair system, was reduced, suggesting that the repair pathway induction was incomplete. Neuropathological examination of α-synuclein transgenic mice showed increased levels of phospho-α-synuclein and DNA double-strand breaks, as well as markers of cellular senescence, at an early, presymptomatic stage. These results suggest that the accumulation of DNA double-strand breaks (DSBs) and cellular senescence are intermediaries of α-synuclein-induced pathogenesis in PD.

SUBMITTER: Yoon YS

PROVIDER: S-EPMC8894476 | biostudies-literature | 2022 Feb

REPOSITORIES: biostudies-literature

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Senescence and impaired DNA damage responses in alpha-synucleinopathy models.

Yoon Ye-Seul YS You Jueng Soo JS Kim Tae-Kyung TK Ahn Woo Jung WJ Kim Myoung Jun MJ Son Keun Hong KH Ricarte Diadem D Ortiz Darlene D Lee Seung-Jae SJ Lee He-Jin HJ

Experimental & molecular medicine 20220208 2

α-Synuclein is a crucial element in the pathogenesis of Parkinson's disease (PD) and related neurological diseases. Although numerous studies have presented potential mechanisms underlying its pathogenesis, the understanding of α-synuclein-mediated neurodegeneration remains far from complete. Here, we show that overexpression of α-synuclein leads to impaired DNA repair and cellular senescence. Transcriptome analysis showed that α-synuclein overexpression led to cellular senescence with activatio ...[more]

PMID: 35136202

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Project description:Parkinson disease (PD) is a neurodegenerative disorder characterized by the abnormal intracellular accumulation of SNCA/α-synuclein. While the exact mechanisms underlying SNCA pathology are not fully understood, increasing evidence suggests the involvement of autophagy as well as lysosomal deficiencies. Because CTSD (cathepsin D) has been proposed to be the major lysosomal protease involved in SNCA degradation, its deficiency has been linked to the presence of insoluble SNCA conformers in the brain of mice and humans as well as to the transcellular transmission of SNCA aggregates. We here postulate that SNCA degradation can be enhanced by the application of the recombinant human proform of CTSD (rHsCTSD). Our results reveal that rHsCTSD is efficiently endocytosed by neuronal cells, correctly targeted to lysosomes and matured to an enzymatically active protease. In dopaminergic neurons derived from induced pluripotent stem cells (iPSC) of PD patients harboring the A53T mutation within the SNCA gene, we confirm the reduction of insoluble SNCA after treatment with rHsCTSD. Moreover, we demonstrate a decrease of pathological SNCA conformers in the brain and within primary neurons of a ctsd-deficient mouse model after dosing with rHsCTSD. Boosting lysosomal CTSD activity not only enhanced SNCA clearance in human and murine neurons as well as tissue, but also restored endo-lysosome and autophagy function. Our findings indicate that CTSD is critical for SNCA clearance and function. Thus, enzyme replacement strategies utilizing CTSD may also be of therapeutic interest for the treatment of PD and other synucleinopathies aiming to decrease the SNCA burden.Abbreviations: aa: amino acid; SNCA/α-synuclein: synuclein alpha; APP: amyloid beta precursor protein; BBB: blood brain barrier; BF: basal forebrain; CBB: Coomassie Brilliant Blue; CLN: neuronal ceroid lipofuscinosis; CNL10: neuronal ceroid lipofuscinosis type 10; Corr.: corrected; CTSD: cathepsin D; CTSB: cathepsin B; DA: dopaminergic; DA-iPSn: induced pluripotent stem cell-derived dopaminergic neurons; dox: doxycycline; ERT: enzyme replacement therapy; Fx: fornix, GBA/β-glucocerebrosidase: glucosylceramidase beta; h: hour; HC: hippocampus; HT: hypothalamus; i.c.: intracranially; IF: immunofluorescence; iPSC: induced pluripotent stem cell; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LSDs: lysosomal storage disorders; MAPT: microtubule associated protein tau; M6P: mannose-6-phosphate; M6PR: mannose-6-phosphate receptor; MB: midbrain; mCTSD: mature form of CTSD; neurofil.: neurofilament; PD: Parkinson disease; proCTSD: proform of CTSD; PRNP: prion protein; RFU: relative fluorescence units; rHsCTSD: recombinant human proCTSD; SAPC: Saposin C; SIM: structured illumination microscopy; T-insol: Triton-insoluble; T-sol: Triton-soluble; TEM: transmission electron microscopy, TH: tyrosine hydroxylase; Thal: thalamus.

Project description:BackgroundLysosomal dysfunction has been implicated in a number of neurodegenerative diseases such as Parkinson's disease (PD). Various molecular, clinical and genetic studies have highlighted a central role of lysosomal pathways and proteins in the pathogenesis of PD. Within PD pathology the synaptic protein alpha-synuclein (αSyn) converts from a soluble monomer to oligomeric structures and insoluble amyloid fibrils. The aim of this study was to unravel the effect of αSyn aggregates on lysosomal turnover, particularly focusing on lysosomal homeostasis and cathepsins. Since these enzymes have been shown to be directly involved in the lysosomal degradation of αSyn, impairment of their enzymatic capacity has extensive consequences.MethodsWe used patient-derived induced pluripotent stem cells and a transgenic mouse model of PD to examine the effect of intracellular αSyn conformers on cell homeostasis and lysosomal function in dopaminergic (DA) neurons by biochemical analyses.ResultsWe found impaired lysosomal trafficking of cathepsins in patient-derived DA neurons and mouse models with αSyn aggregation, resulting in reduced proteolytic activity of cathepsins in the lysosome. Using a farnesyltransferase inhibitor, which boosts hydrolase transport via activation of the SNARE protein ykt6, we enhanced the maturation and proteolytic activity of cathepsins and thereby decreased αSyn protein levels.ConclusionsOur findings demonstrate a strong interplay between αSyn aggregation pathways and function of lysosomal cathepsins. It appears that αSyn directly interferes with the enzymatic function of cathepsins, which might lead to a vicious cycle of impaired αSyn degradation. Lysosomal trafficking of cathepsin D (CTSD), CTSL and CTSB is disrupted when alpha-synuclein (αSyn) is aggregated. This results in a decreased proteolytic activity of cathepsins, which directly mediate αSyn clearance. Boosting the transport of the cathepsins to the lysosome increases their activity and thus contributes to efficient αSyn degradation.

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Senescence and impaired DNA damage responses in alpha-synucleinopathy models.

Publications

Senescence and impaired DNA damage responses in alpha-synucleinopathy models.

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