| 1. |
- Thorsen, Michael, 1974, et al.
(författare)
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Glutathione serves an extracellular defence function to decrease arsenite accumulation and toxicity in yeast.
- 2012
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Ingår i: Molecular microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 84:6, s. 1177-88
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic is an environmental toxin and a worldwide health hazard. Since this metalloid is ubiquitous in nature, virtually all living organisms require systems for detoxification and tolerance acquisition. Here, we show that during chronic exposure to arsenite [As(III)], Saccharomyces cerevisiae (budding yeast) exports and accumulates the low-molecular-weight thiol molecule glutathione (GSH) outside of cells. Extracellular accumulation of the arsenite triglutathione complex As(GS)₃ was also detected and direct transport assays demonstrate that As(GS)₃ does not readily enter cells. Yeast cells with increased extracellular GSH levels accumulate less arsenic and display improved growth when challenged with As(III). Conversely, cells defective in export and extracellular accumulation of GSH are As(III) sensitive. Taken together, our data are consistent with a novel detoxification mechanism in which GSH is exported to protect yeast cells from arsenite toxicity by preventing its uptake.
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| 2. |
- Furukawa, Kentaro, et al.
(författare)
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Expression of the yeast aquaporin Aqy2 affects cell surface properties under the control of osmoregulatory and morphogenic signalling pathways.
- 2009
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Ingår i: Molecular microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 74:5, s. 1272-86
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Tidskriftsartikel (refereegranskat)abstract
- Aquaporins mediate rapid and selective water transport across biological membranes. The yeast Saccharomyces cerevisiae possesses two aquaporins, Aqy1 and Aqy2. Here, we show that Aqy2 is involved in controlling cell surface properties and that its expression is controlled by osmoregulatory and morphogenic signalling pathways. Deletion of AQY2 results in diminished fluffy colony morphology while overexpression of AQY2 causes strong agar invasion and adherence to plastic surfaces. Hyper-osmotic stress inhibits morphological developments including the above characteristics as well as AQY2 expression through the osmoregulatory Hog1 mitogen-activated protein kinase. Moreover, two pathways known to control morphological developments are involved in regulation of AQY2 expression: the protein kinase A pathway derepresses AQY2 expression through the Sfl1 repressor, and the filamentous growth Kss1 mitogen-activated protein kinase pathway represses AQY2 expression in a Kss1 activity-independent manner. The AQY2 expression pattern resembles in many ways that of MUC1/FLO11, which encodes a cell surface glycoprotein required for morphological developments. Our observations suggest a potential link between aquaporins and cell surface properties, and relate to the proposed role of mammalian aquaporins in tumour cell migration and invasion.
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| 3. |
- Bilsland, Elizabeth, 1973, et al.
(författare)
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Rck1 and Rck2 MAPKAP kinases and the HOG pathway are required for oxidative stress resistance
- 2004
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 53:6, s. 1743-56
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a role in oxidative and metal stress resistance for the MAPK-activated protein kinases Rck1 and Rck2 in Saccharomyces cerevisiae. We show that Hog1 is robustly phosphorylated in a Pbs2-dependent way during oxidative stress, and that Rck2 also is phosphorylated under these circumstances. Hog1 concentrates in the nucleus in oxidative stress. Hog1 localization is partially dependent on Rck2, as rck2 cells have more nuclear Hog1 than wild-type cells. We find several proteins with a role in oxidative stress resistance using Rck1 or Rck2 as baits in a two-hybrid screen. We identify the transcription factor Yap2 as a putative target for Rck1, and the Zn2+ transporter Zrc1 as a target for Rck2. Yap2 is normally cytoplasmic, but rapidly migrates to the nucleus upon exposure to oxidative stress agents. In a fraction of untreated pbs2 cells, Yap2 is nuclear. Zrc1 co-immunoprecipitates with Rck2, and ZRC1 is genetically downstream of RCK2. These data connect activation of the Hog1 MAPK cascade with effectors having a role in oxidative stress resistance.
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| 4. |
- Fredriksson, Åsa, 1968, et al.
(författare)
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Induction of the heat shock regulon in response to increased mistranslation requires oxidative modification of the malformed proteins
- 2006
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 59:1, s. 350-359
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Tidskriftsartikel (refereegranskat)abstract
- The Escherichia coli rpsD12 allele, which reduces translational fidelity and elevates expression of heat shock protein (Hsp) genes, only enhanced Hsp gene expression in the presence of oxygen. Similarly, the rpsL141 allele, which reduces mistranslation and Hsp gene expression, failed to affect the Hsp regulon in cells grown anaerobically. Increased production of Hsps in response to starvation is associated with increased mistranslation and was demonstrated to likewise require the presence of oxygen. Thus, mistranslation triggered by starvation or mutations in the accuracy centre of the ribosome appear to elevate Hsp gene expression via an oxidative modification of mistranslated proteins. In contrast, Hsp gene induction during temperature upshifts was independent of oxygen availability. The data further suggest that it is the oxidative modification of mistranslated DnaK substrates rather than oxidation of DnaK itself that triggers Hsp gene expression upon starvation
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| 5. |
- Mandal, Goutam, et al.
(författare)
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Modulation of Leishmania major aquaglyceroporin activity by a mitogen-activated protein kinase.
- 2012
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Ingår i: Molecular microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 85:6, s. 1204-1218
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Tidskriftsartikel (refereegranskat)abstract
- Leishmania major aquaglyceroporin (LmjAQP1) adventitiously facilitates the uptake of antimonite [Sb(III)], an active form of Pentostam® or Glucantime®, which are the first line of defence against all forms of leishmaniasis. The present paper shows that LmjAQP1 activity is modulated by the mitogen-activated protein kinase, LmjMPK2. Leishmania parasites coexpressing LmjAQP1 and LmjMPK2 show increased Sb(III) uptake and increased Sb(III) sensitivity. When subjected to a hypo-osmotic stress, these cells show faster volume recovery than cells expressing LmjAQP1 alone. LmjAQP1 is phosphorylated in vivo at Thr-197 and this phosphorylation requires LmjMPK2 activity. Lys-42 of LmjMPK2 is critical for its kinase activity. Cells expressing altered T197A LmjAQP1 or K42A LmjMPK2 showed decreased Sb(III) influx and a slower volume recovery than cells expressing wild-type proteins. Phosphorylation of LmjAQP1 led to a decrease in its turnover rate affecting LmjAQP1 activity. Although LmjAQP1 is localized to the flagellum of promastigotes, upon phosphorylation, it is relocalized to the entire surface of the parasite. Leishmania mexicana promastigotes with an MPK2 deletion showed reduced Sb(III) uptake and slower volume recovery than wild-type cells. This is the first report where a parasite aquaglyceroporin activity is post-translationally modulated by a mitogen-activated protein kinase.
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| 6. |
- Molin, Mikael, 1973, et al.
(författare)
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Dihydroxyacetone detoxification in Saccharomyces cerevisiae involves formaldehyde dissimilation
- 2006
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 60:4, s. 925-938
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Tidskriftsartikel (refereegranskat)abstract
- To investigate Saccharomyces cerevisiae physiology during growth on the conditionally toxic triose dihydroxyacetone (DHA), protein expression was studied in strains overexpressing either of the two dihydroxyacetone kinase isogenes, DAK1 or DAK2, that grow well utilizing DHA as a carbon and energy source. DHA metabolism was found mostly similar to ethanol utilization, involving a strong component of glucose derepression, but also involved DHA-specific regulatory changes. A specific and strong (10- to 30-fold induction of formaldehyde dehydrogenase, Fdhlp, indicated activation of the formaldehyde dissimilation pathway in DHA medium. The importance of this pathway was further supported by impaired adaptation to DHA growth and DHA survival in a glutathione-dependent formaldehyde dehydrogenase (SFA1) deletion mutant. Glutathione synthase (GSH1) deletion led to decreased DHA survival in agreement with the glutathione cofactor requirement for the SFA1-encoded activity. DHA toxicity did, however, not solely appear related to formaldehyde accumulation, because SFA1 overexpression only enhanced formaldehyde but not DHA tolerance. In further agreement with a low DHA-to-formaldehyde flux, GSH supplements in the low µM range also fully suppressed the DHA sensitivity of a gsh1Δ strain. Under growth reduction on high (100 mM) DHA medium we report increased levels of advanced glycation end-product (AGE) formation on total protein. Under these high-DHA conditions expression of several stress-related proteins, e.g. a heat-shock protein (Hsp104p) and the oxidative stress indicator, alkyl hydroperoxide reductase (Ahp1p) was also found induced. However, hallmark determinants of oxidative stress tolerance (e.g. YAP1, SKN7, HYR1/GPX3 and SOD2) were redundant for DHA tolerance, thus indicating mechanisms of DHA toxicity largely independent of central oxidative stress defence mechanisms. We conclude that mechanisms for DHA growth and detoxification appear complex and that the evolutionary strive to minimize detrimental effects of this intracellular metabolite links to both formaldehyde and glutathione metabolism
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| 7. |
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| 8. |
- Alao, John Patrick, 1973, et al.
(författare)
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Caffeine stabilizes Cdc25 independently of Rad3 in Schizosaccharomyces pombe contributing to checkpoint override
- 2014
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 92:4, s. 777-796
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Tidskriftsartikel (refereegranskat)abstract
- Cdc25 is required for Cdc2 dephosphorylation and is thus essential for cell cycle progression. Checkpoint activation requires dual inhibition of Cdc25 and Cdc2 in a Rad3-dependent manner. Caffeine is believed to override activation of the replication and DNA damage checkpoints by inhibiting Rad3-related proteins in both Schizosaccharomyces pombe and mammalian cells. In this study, we have investigated the impact of caffeine on Cdc25 stability, cell cycle progression and checkpoint override. Caffeine induced Cdc25 accumulation in S.pombe independently of Rad3. Caffeine delayed cell cycle progression under normal conditions but advanced mitosis in cells treated with replication inhibitors and DNA-damaging agents. In the absence of Cdc25, caffeine inhibited cell cycle progression even in the presence of hydroxyurea or phleomycin. Caffeine induces Cdc25 accumulation in S.pombe by suppressing its degradation independently of Rad3. The induction of Cdc25 accumulation was not associated with accelerated progression through mitosis, but rather with delayed progression through cytokinesis. Caffeine-induced Cdc25 accumulation appears to underlie its ability to override cell cycle checkpoints. The impact of Cdc25 accumulation on cell cycle progression is attenuated by Srk1 and Mad2. Together our findings suggest that caffeine overrides checkpoint enforcement by inducing the inappropriate nuclear localization of Cdc25.
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| 9. |
- Furukawa, Kentaro, et al.
(författare)
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Synthetic biology: lessons from engineering yeast MAPK signalling pathways.
- 2013
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Ingår i: Molecular microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 88:1, s. 5-19
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Tidskriftsartikel (refereegranskat)abstract
- All living cells respond to external stimuli and execute specific physiological responses through signal transduction pathways. Understanding the mechanisms controlling signalling pathways is important for diagnosing and treating diseases and for reprogramming cells with desired functions. Although many of the signalling components in the budding yeast Saccharomyces cerevisiae have been identified by genetic studies, many features concerning the dynamic control of pathway activity, cross-talk, cell-to-cell variability or robustness against perturbation are still incompletely understood. Comparing the behaviour of engineered and natural signalling pathways offers insight complementary to that achievable with standard genetic and molecular studies. Here, we review studies that aim at a deeper understanding of signalling design principles and generation of novel signalling properties by engineering the yeast mitogen-activated protein kinase (MAPK) pathways. The underlying approaches can be applied to other organisms including mammalian cells and offer opportunities for building synthetic pathways and functionalities useful in medicine and biotechnology.
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| 10. |
- Mattola, S., et al.
(författare)
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Nuclear entry and egress of parvoviruses
- 2022
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 118:4, s. 295-308
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Forskningsöversikt (refereegranskat)abstract
- Parvoviruses are small non-enveloped single-stranded DNA viruses, which depend on host cell nuclear transcriptional and replication machinery. After endosomal exposure of nuclear localization sequence and a phospholipase A(2) domain on the capsid surface, and escape into the cytosol, parvovirus capsids enter the nucleus. Due to the small capsid diameter of 18-26 nm, intact capsids can potentially pass into the nucleus through nuclear pore complexes (NPCs). This might be facilitated by active nuclear import, but capsids may also follow an alternative entry pathway that includes activation of mitotic factors and local transient disruption of the nuclear envelope. The nuclear entry is followed by currently undefined events of viral genome uncoating. After genome release, viral replication compartments are initiated and infection proceeds. Parvoviral genomes replicate during cellular S phase followed by nuclear capsid assembly during virus-induced S/G2 cell cycle arrest. Nuclear egress of capsids occurs upon nuclear envelope degradation during apoptosis and cell lysis. An alternative pathway for nuclear export has been described using active transport through the NPC mediated by the chromosome region maintenance 1 protein, CRM1, which is enhanced by phosphorylation of the N-terminal domain of VP2. However, other alternative but not yet uncharacterized nuclear export pathways cannot be excluded.
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