30 research outputs found

    Yeast peroxisomes:de novo formation and maintenance

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    Peroxisomen zijn belangrijke organellen in eukaryote cellen. Ze bestaan uit een enkele membraan met een eiwitrijke matrix. Belangrijke peroxisomale processen zijn de β-oxidatie van vetzuren en de afbraak van waterstofperoxide. Momenteel is er veel discussie over de wijze waarop peroxisomen worden gevormd. In wild-type gisten worden ze voornamelijk aangemaakt door deling van al aanwezige organellen. Er bestaan echter mutanten waarin peroxisomen volledig afwezig zijn (b.v. in pex3 of pex19 mutanten). Tot nu toe werd gedacht dat na het herintroduceren van het PEX3 of PEX19 gen in deze mutanten nieuwe peroxisomen werden gevormd vanuit het endoplasmatisch reticulum (ER). Experimenten die beschreven zijn in dit proefschrift wezen uit dat in pex3 en pex19 mutanten wel degelijk peroxisomale membraan structuren aanwezig zijn. Deze structuren zijn de basis voor de vorming van nieuwe peroxisomen als het PEX3 of PEX19 gen wordt geherintroduceerd. Onder deze omstandigheden worden peroxisomen dus niet uit het ER gevormd. Peroxisoom homeostase omvat een nauwkeurige balans tussen de vorming en afbraak (pexofagie) van peroxisomen. We hebben laten zien dat de aanwezigheid van eiwitaggregaten slecht is voor cellen en leidt tot verhoogde niveaus van zuurstof radicalen. Deze eiwitaggregaten stimuleerden asymmetrische deling van peroxisomen en afbraak van de aggregaat bevattende organellen. Tenslotte hebben we een nieuwe functie gevonden voor het peroxisomale membraan eiwit Wsc. Dit eiwit speelt een rol in de deling en overerving van peroxisomen in gisten die groeien op glucose

    The Impact of Peroxisomes on Cellular Aging and Death

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    Peroxisomes are ubiquitous eukaryotic organelles, which perform a plethora of functions including hydrogen peroxide metabolism and β-oxidation of fatty acids. Reactive oxygen species produced by peroxisomes are a major contributing factor to cellular oxidative stress, which is supposed to significantly accelerate aging and cell death according to the free radical theory of aging. However, relative to mitochondria, the role of the other oxidative organelles, the peroxisomes, in these degenerative pathways has not been extensively investigated. In this contribution we discuss our current knowledge on the role of peroxisomes in aging and cell death, with focus on studies performed in yeast

    Hansenula polymorpha Pex37 is a peroxisomal membrane protein required for organelle fission and segregation

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    Here, we describe a novel peroxin, Pex37, in the yeast Hansenula polymorpha. H. polymorpha Pex37 is a peroxisomal membrane protein, which belongs to a protein family that includes, among others, the Neurospora crassa Woronin body protein Wsc, the human peroxisomal membrane protein PXMP2, the Saccharomyces cerevisiae mitochondrial inner membrane protein Sym1, and its mammalian homologue MPV17. We show that deletion of H. polymorpha PEX37 does not appear to have a significant effect on peroxisome biogenesis or proliferation in cells grown at peroxisome‐inducing growth conditions (methanol). However, the absence of Pex37 results in a reduction in peroxisome numbers and a defect in peroxisome segregation in cells grown at peroxisome‐repressing conditions (glucose). Conversely, overproduction of Pex37 in glucose‐grown cells results in an increase in peroxisome numbers in conjunction with a decrease in their size. The increase in numbers in PEX37‐overexpressing cells depends on the dynamin‐related protein Dnm1. Together our data suggest that Pex37 is involved in peroxisome fission in glucose‐grown cells. Introduction of human PXMP2 in H. polymorpha pex37 cells partially restored the peroxisomal phenotype, indicating that PXMP2 represents a functional homologue of Pex37. H.polymorpha pex37 cells did not show aberrant growth on any of the tested carbon and nitrogen sources that are metabolized by peroxisomal enzymes, suggesting that Pex37 may not fulfill an essential function in transport of these substrates or compounds required for their metabolism across the peroxisomal membrane.This work was supported by a grant from the Marie Curie Initial Training Networks (ITN) program PerFuMe (Grant Agreement Number 316723) to RS, NB, DPD, and IJvdK.Peer reviewe

    Combined Vorinostat and Chloroquine Inhibit Sodium Iodide Symporter Endocytosis and Enhance Radionuclide Uptake In Vivo

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    Purpose Patients with aggressive thyroid cancer are frequently failed by the central therapy of ablative radioiodide (RAI) uptake, due to reduced plasma membrane (PM) localization of the sodium/iodide symporter (NIS). We aimed to understand how NIS is endocytosed away from the PM of human thyroid cancer cells, and whether this was druggable in vivo.Experimental DesignInformed by analysis of endocytic gene expression in patients with aggressive thyroid cancer, we used mutagenesis, NanoBiT interaction assays, cell surface biotinylation assays, RAI uptake and NanoBRET to understand the mechanisms of NIS endocytosis in transformed cell lines and patient-derived human primary thyroid cells. Systemic drug responses were monitored via 99mTc pertechnetate gamma counting and gene expression in BALB/c mice.ResultsWe identify an acidic dipeptide within the NIS C-terminus which mediates binding to the 2 subunit of the Adaptor Protein 2 (AP2) heterotetramer. We discovered that the FDA-approved drug chloroquine modulates NIS accumulation at the PM in a functional manner that is AP2 dependent. In vivo, chloroquine treatment of BALB/c mice significantly enhanced thyroidal uptake of 99mTc pertechnetate in combination with the histone deacetylase (HDAC) inhibitor vorinostat/ SAHA, accompanied by increased thyroidal NIS mRNA. Bioinformatic analyses validated the clinical relevance of AP2 genes with disease-free survival in RAI-treated DTC, enabling construction of an AP2 gene-related risk score classifier for predicting recurrence.ConclusionsNIS internalisation is specifically druggable in vivo. Our data therefore provide new translatable potential for improving RAI therapy using FDA-approved drugs in patients with aggressive thyroid cancer.<br/

    Yeast peroxisomes

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    Peroxisomen zijn belangrijke organellen in eukaryote cellen. Ze bestaan uit een enkele membraan met een eiwitrijke matrix. Belangrijke peroxisomale processen zijn de β-oxidatie van vetzuren en de afbraak van waterstofperoxide. Momenteel is er veel discussie over de wijze waarop peroxisomen worden gevormd. In wild-type gisten worden ze voornamelijk aangemaakt door deling van al aanwezige organellen. Er bestaan echter mutanten waarin peroxisomen volledig afwezig zijn (b.v. in pex3 of pex19 mutanten). Tot nu toe werd gedacht dat na het herintroduceren van het PEX3 of PEX19 gen in deze mutanten nieuwe peroxisomen werden gevormd vanuit het endoplasmatisch reticulum (ER). Experimenten die beschreven zijn in dit proefschrift wezen uit dat in pex3 en pex19 mutanten wel degelijk peroxisomale membraan structuren aanwezig zijn. Deze structuren zijn de basis voor de vorming van nieuwe peroxisomen als het PEX3 of PEX19 gen wordt geherintroduceerd. Onder deze omstandigheden worden peroxisomen dus niet uit het ER gevormd. Peroxisoom homeostase omvat een nauwkeurige balans tussen de vorming en afbraak (pexofagie) van peroxisomen. We hebben laten zien dat de aanwezigheid van eiwitaggregaten slecht is voor cellen en leidt tot verhoogde niveaus van zuurstof radicalen. Deze eiwitaggregaten stimuleerden asymmetrische deling van peroxisomen en afbraak van de aggregaat bevattende organellen. Tenslotte hebben we een nieuwe functie gevonden voor het peroxisomale membraan eiwit Wsc. Dit eiwit speelt een rol in de deling en overerving van peroxisomen in gisten die groeien op glucose. Peroxisomes are important eukaryotic organelles, consisting of a protein rich matrix, surrounded by a single membrane. Generalized functions include β-oxidation of fatty acids and detoxification of hydrogen peroxide. Currently, it is highly debated how peroxisomes are formed. In wild-type yeast cells the organelles primarily develop by fission of pre-existing ones. However, it has been proposed that they can also form de novo from the endoplasmic reticulum (ER) in mutant cells fully lacking peroxisomal membrane structures (e.g. pex3 or pex19), upon reintroduction of the corresponding genes. Studies described in this thesis revealed, however, in these mutants, pre-peroxisomal structures are present, which serve as template for re-introduction of peroxisomes. Hence, under these conditions peroxisomes do not derive from the ER. Peroxisome homeostasis involves a delicate balance between peroxisome biogenesis and degradation (pexophagy). We demonstrate that the presence of protein aggregates in the peroxisomal matrix had physiological disadvantages as it affected growth of the cells and caused enhanced levels of reactive oxygen species. These protein aggregates promoted asymmetric peroxisome fission and degradation of peroxisomes containing protein aggregates via autophagy Finally, this thesis describes a novel function for the peroxisomal membrane protein Wsc, which is important for peroxisome fission and segregation in glucose-grown yeast cells.
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