Cell cycle checkpoints, oncogene-induced senescence and programmed cell death represent intrinsic barriers to tumorigenesis. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of the tumour suppressor p53 and has been implicated in termination of the DNA damage response. Here, we addressed the consequences of increased PPM1D activity resulting from the gain-of-function truncating mutations in exon 6 of the PPM1D. We show that while control cells permanently exit the cell cycle and reside in senescence in the presence of DNA damage caused by ionising radiation or replication stress induced by the active RAS oncogene, RPE1-hTERT and BJ-hTERT cells carrying the truncated PPM1D continue proliferation in the presence of DNA damage, form micronuclei and accumulate genomic rearrangements revealed by karyotyping. Further, we show that increased PPM1D activity promotes cell growth in the soft agar and formation of tumours in xenograft models. Finally, expression profiling of the transformed clones revealed dysregulation of several oncogenic and tumour suppressor pathways. Our data support the oncogenic potential of PPM1D in the context of exposure to ionising radiation and oncogene-induced replication stress.
- MeSH
- buněčná smrt genetika MeSH
- lidé MeSH
- myši MeSH
- nádorová transformace buněk * genetika MeSH
- nádorový supresorový protein p53 genetika metabolismus MeSH
- poškození DNA * genetika MeSH
- proliferace buněk genetika MeSH
- proteinfosfatasa 2C * genetika metabolismus MeSH
- proteinfosfatasy genetika metabolismus MeSH
- stárnutí buněk * genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- MeSH
- buněčná diferenciace MeSH
- buněčný rodokmen MeSH
- hematopoetické kmenové buňky * cytologie metabolismus MeSH
- hematopoéza MeSH
- lidé MeSH
- proteinfosfatasy metabolismus genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- komentáře MeSH
- úvodníky MeSH
Polo-like kinases play essential roles in cell cycle control and mitosis. In contrast to other members of this kinase family, PLK3 has been reported to be activated upon cellular stress including DNA damage, hypoxia and osmotic stress. Here we knocked out PLK3 in human non-transformed RPE cells using CRISPR/Cas9-mediated gene editing. Surprisingly, we find that loss of PLK3 does not impair stabilization of HIF1α after hypoxia, phosphorylation of the c-Jun after osmotic stress and dynamics of DNA damage response after exposure to ionizing radiation. Similarly, RNAi-mediated depletion of PLK3 did not impair stress response in human transformed cell lines. Exposure of cells to various forms of stress also did not affect kinase activity of purified EGFP-PLK3. We conclude that PLK3 is largely dispensable for stress response in human cells. Using mass spectrometry, we identify protein phosphatase 6 as a new interacting partner of PLK3. Polo box domain of PLK3 mediates the interaction with the PP6 complex. Finally, we find that PLK3 is phosphorylated at Thr219 in the T-loop and that PP6 constantly dephosphorylates this residue. However, in contrast to PLK1, phosphorylation of Thr219 does not upregulate enzymatic activity of PLK3, suggesting that activation of both kinases is regulated by distinct mechanisms.
- MeSH
- buněčné linie MeSH
- fosforylace MeSH
- lidé MeSH
- poškození DNA genetika MeSH
- protein-serin-threoninkinasy metabolismus MeSH
- proteinfosfatasy metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Yeast form complex highly organized colonies in which cells undergo spatiotemporal phenotypic differentiation in response to local gradients of nutrients, metabolites, and specific signaling molecules. Colony fitness depends on cell interactions, cooperation, and the division of labor between differentiated cell subpopulations. Here, we describe the regulation and dynamics of the expansion of papillae that arise during colony aging, which consist of cells that overcome colony regulatory rules and disrupt the synchronized colony structure. We show that papillae specifically expand within the U cell subpopulation in differentiated colonies. Papillae emerge more frequently in some strains than in others. Genomic analyses further revealed that the Whi2p-Psr1p/Psr2p complex (WPPC) plays a key role in papillae expansion. We show that cells lacking a functional WPPC have a sizable interaction-specific fitness advantage attributable to production of and resistance to a diffusible compound that inhibits growth of other cells. Competitive superiority and high relative fitness of whi2 and psr1psr2 strains are particularly pronounced in dense spatially structured colonies and are independent of TORC1 and Msn2p/Msn4p regulators previously associated with the WPPC function. The WPPC function, described here, might be a regulatory mechanism that balances cell competition and cooperation in dense yeast populations and, thus, contributes to cell synchronization, pattern formation, and the expansion of cells with a competitive fitness advantage.
- MeSH
- membránové proteiny genetika metabolismus MeSH
- proliferace buněk fyziologie MeSH
- proteinfosfatasy genetika metabolismus MeSH
- regulace genové exprese u hub fyziologie MeSH
- Saccharomyces cerevisiae - proteiny genetika metabolismus MeSH
- Saccharomyces cerevisiae genetika metabolismus MeSH
- signální transdukce fyziologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: Reversible protein phosphorylation catalyzed by protein kinases and phosphatases is the primary mechanism for signal transduction in all living organisms. Streptococcus pneumoniae encodes a single Ser/Thr protein kinase, StkP, which plays a role in virulence, stress resistance and the regulation of cell wall synthesis and cell division. However, the role of its cognate phosphatase, PhpP, is not well defined. RESULTS: Here, we report the successful construction of a ΔphpP mutant in the unencapsulated S. pneumoniae Rx1 strain and the characterization of its phenotype. We demonstrate that PhpP negatively controls the level of protein phosphorylation in S. pneumoniae both by direct dephosphorylation of target proteins and by dephosphorylation of its cognate kinase, StkP. Catalytic inactivation or absence of PhpP resulted in the hyperphosphorylation of StkP substrates and specific phenotypic changes, including sensitivity to environmental stresses and competence deficiency. The morphology of the ΔphpP cells resembled the StkP overexpression phenotype and conversely, overexpression of PhpP resulted in cell elongation mimicking the stkP null phenotype. Proteomic analysis of the phpP knock-out strain permitted identification of a novel StkP/PhpP substrate, Spr1851, a putative RNA-binding protein homologous to Jag. Here, we show that pneumococcal Jag is phosphorylated on Thr89. Inactivation of jag confers a phenotype similar to the phpP mutant strain. CONCLUSIONS: Our results suggest that PhpP and StkP cooperatively regulate cell division of S. pneumoniae and phosphorylate putative RNA binding protein Jag.
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- buněčná stěna metabolismus MeSH
- buněčné dělení fyziologie MeSH
- fenotyp MeSH
- fosforylace MeSH
- genový knockout MeSH
- mutantní proteiny genetika metabolismus MeSH
- oxidační stres fyziologie MeSH
- protein-serin-threoninkinasy genetika metabolismus MeSH
- proteinfosfatasy genetika metabolismus MeSH
- proteiny vázající RNA metabolismus MeSH
- rekombinantní fúzní proteiny metabolismus MeSH
- sekvenční delece MeSH
- signální transdukce MeSH
- Streptococcus pneumoniae cytologie enzymologie genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
Cells are constantly challenged by DNA damage and protect their genome integrity by activation of an evolutionary conserved DNA damage response pathway (DDR). A central core of DDR is composed of a spatiotemporally ordered net of post-translational modifications, among which protein phosphorylation plays a major role. Activation of checkpoint kinases ATM/ATR and Chk1/2 leads to a temporal arrest in cell cycle progression (checkpoint) and allows time for DNA repair. Following DNA repair, cells re-enter the cell cycle by checkpoint recovery. Wip1 phosphatase (also called PPM1D) dephosphorylates multiple proteins involved in DDR and is essential for timely termination of the DDR. Here we have investigated how Wip1 is regulated in the context of the cell cycle. We found that Wip1 activity is downregulated by several mechanisms during mitosis. Wip1 protein abundance increases from G(1) phase to G(2) and declines in mitosis. Decreased abundance of Wip1 during mitosis is caused by proteasomal degradation. In addition, Wip1 is phosphorylated at multiple residues during mitosis, and this leads to inhibition of its enzymatic activity. Importantly, ectopic expression of Wip1 reduced γH2AX staining in mitotic cells and decreased the number of 53BP1 nuclear bodies in G(1) cells. We propose that the combined decrease and inhibition of Wip1 in mitosis decreases the threshold necessary for DDR activation and enables cells to react adequately even to modest levels of DNA damage encountered during unperturbed mitotic progression.
- MeSH
- DNA primery genetika MeSH
- fluorescenční protilátková technika MeSH
- fosforylace MeSH
- hmotnostní spektrometrie MeSH
- kontrolní body M fáze buněčného cyklu fyziologie MeSH
- kvantitativní polymerázová řetězová reakce MeSH
- lidé MeSH
- malá interferující RNA genetika MeSH
- mitóza fyziologie MeSH
- nádorové buněčné linie MeSH
- poškození DNA * MeSH
- proteinfosfatasy metabolismus MeSH
- regulace genové exprese fyziologie MeSH
- signální transdukce fyziologie MeSH
- transfekce MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The effects of gemfibrozil (GFZ), an antihyperlipidemic agent, on the anionic transport of the human red blood cells (RBC) during the oxygenation-deoxygenation cycle were examined. Gemfibrozil clearly plays a role in the modulation of the anionic flux in erythrocytes; in fact it causes a strong increment of anions transport when the RBCs are in the high-oxygenation state (HOS). Such an effect is remarkably reduced in the lowoxygenation state (LOS). With the aim of identifying the dynamics of fibrate action, this effect has been investigated also in human ghost and chicken erythrocytes. These latter, in fact, are known to possess a B3 (anion transporter or Band 3) modified at the cytoplasmic domain (cdb3) which plays a significant role in the metabolic modulation of red blood cells. The results were analyzed taking into account the well-known interactions between fibrates and both conformational states of hemoglobin i.e. the T state (deoxy-conformation) and the R state (oxy-conformation). The effect of gemfibrozil on anionic influx appears to be due to a wide interaction involving a “multimeric” Hb-GFZ-cdb3 macromolecular complex.
- Klíčová slova
- Sulfate transport, Oxygenation - deoxygenation,
- MeSH
- dospělí MeSH
- erytrocytární membrána MeSH
- erytrocyty metabolismus účinky léků MeSH
- financování organizované MeSH
- gemfibrozil farmakologie MeSH
- hemoglobiny metabolismus MeSH
- hypolipidemika farmakologie MeSH
- indikátory a reagencie MeSH
- kalibrace MeSH
- kinetika MeSH
- konformace proteinů MeSH
- lidé středního věku MeSH
- lidé MeSH
- proteinfosfatasy metabolismus MeSH
- pufry MeSH
- sírany krev MeSH
- spotřeba kyslíku fyziologie účinky léků MeSH
- vanadáty farmakologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
Levels of Rb2/p130 protein are increased 5-10-fold following all-trans-retinoic acid (ATRA) treatment of the retinoid-sensitive ovarian adenocarcinoma cell line CAOV3, but not the retinoid-resistant adenocarcinoma cell line SKOV3. We found that this increase in Rb2/p130 protein levels in ATRA-treated CAOV3 cells was the result of an increased protein stability. Moreover, Rb2/p130 exhibited a decreased ubiquitination following ATRA treatment. Because phosphorylation frequently mediates ubiquitination of proteins, we examined the serine/threonine phosphatase activity in our CAOV3 cells following ATRA treatment. A significant increase in Ser/Thr phosphatase activity was found, which correlated with a rise in the level of protein phosphatase 2A (PP2A) catalytic subunit-alpha. In addition, co-immunoprecipitation and glutathione S-transferase pull-down studies demonstrated that PP2A and Rb2/p130 associate. We have made use of a battery of Rb2/p130 mutants to determine the sites dephosphorylated in response to ATRA treatment of CAOV3 cells. Obligate CDK4 phosphorylation sites seemed most important to the stability of the protein and are among the candidate sites that are dephosphorylated by PP2A following ATRA treatment. Finally, using both small interfering RNA specific to the catalytic subunit of PP2A and a variant of the SKOV3 cell line that overexpresses PP2A, we have shown that modulation of PP2A protein levels correlates with the ability of ATRA to inhibit growth of ovarian carcinoma cells. Our data suggest that ATRA mediates growth inhibition by stabilizing Rb2/p130 via a mechanism that involves induction of PP2A, an enzyme that can potentially dephosphorylate Rb2/p130, thereby protecting it from degradation by the proteasome.
- MeSH
- buněčné dělení účinky léků MeSH
- endopeptidasy metabolismus MeSH
- fosfoproteiny metabolismus účinky léků MeSH
- fosforylace MeSH
- lidé MeSH
- nádorové buněčné linie MeSH
- nádory vaječníků metabolismus patologie MeSH
- protein p130 podobný retinoblastomu MeSH
- proteinfosfatasa 2 MeSH
- proteinfosfatasy * fyziologie metabolismus MeSH
- proteiny * MeSH
- tretinoin * farmakologie MeSH
- ubikvitiny metabolismus MeSH
- upregulace účinky léků MeSH
- vazba proteinů fyziologie účinky léků MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
PTEN, a tumor suppressor commonly targeted in human cancer, possesses phosphatase activities toward both protein and lipid substrates. While PTEN suppresses gliomas through cell cycle inhibition which requires its lipid phosphatase activity, PTEN's effects on other tumor types and the role of its protein phosphatase activity are controversial or unknown. Here we show that exogenous wild-type PTEN arrests some, but not all human breast cancer cell lines in G1, in a manner independent of endogenous PTEN. Unexpectedly, the G129E mutant of PTEN selectively deficient in the lipid phosphatase activity still blocked the cell cycle of MCF-7 cells, while the G129R and H123Y mutants lacking both phosphatase activities were ineffective. These results suggest that PTEN's protein phosphatase activity likely contributes to its tumor suppressor function in subsets of tumors and that elucidation of downstream targets which dictate cellular responses to PTEN may have important implications for future cancer treatment strategies. Copyright 2000 Academic Press.
- MeSH
- buněčný cyklus MeSH
- elektroforéza v polyakrylamidovém gelu MeSH
- fosfatasy fyziologie genetika MeSH
- fosfohydroláza PTEN MeSH
- lidé MeSH
- mutace MeSH
- nádorové buňky kultivované MeSH
- nádorové supresorové proteiny * MeSH
- proteinfosfatasy * metabolismus MeSH
- tumor supresorové geny * MeSH
- western blotting MeSH
- Check Tag
- lidé MeSH
