Biochim. Biophys. Acta [JOURNAL]
Sun
200 papers
The importance of being (slightly) modified: The role of rRNA editing on gene expression control and its connections with cancer.
Penzo M, Galbiati A, Treré D … +1 more , Montanaro L
Biochim Biophys Acta · 2016 Dec · PMID 27815156 · Publisher ↗
In human ribosomal RNAs, over 200 residues are modified by specific, RNA-driven enzymatic complexes or stand-alone, RNA-independent enzymes. In most cases, modification sites are placed in specific positions within impor...
In human ribosomal RNAs, over 200 residues are modified by specific, RNA-driven enzymatic complexes or stand-alone, RNA-independent enzymes. In most cases, modification sites are placed in specific positions within important functional areas of the ribosome. Some evidence indicates that the altered control in ribosomal RNA modifications may affect ribosomal function during mRNA translation. Here we provide an overview of the connections linking ribosomal RNA modifications to ribosome function, and suggest how aberrant modifications may affect the control of the expression of key cancer genes, thus contributing to tumor development. In addition, the future perspectives in this field are discussed.
Yersinia YopJ negatively regulates IRF3-mediated antibacterial response through disruption of STING-mediated cytosolic DNA signaling.
Cao Y, Guan K, He X … +6 more , Wei C, Zheng Z, Zhang Y, Ma S, Zhong H, Shi W
Biochim Biophys Acta · 2016 Dec · PMID 27742471 · Publisher ↗
The Yersinia outer protein J (YopJ) plays a pivotal role in evading the host immune response and establishes a persistent infection in host cells after bacterial infection. YopJ is a cysteine protease and can act as a de...
The Yersinia outer protein J (YopJ) plays a pivotal role in evading the host immune response and establishes a persistent infection in host cells after bacterial infection. YopJ is a cysteine protease and can act as a deubiquitinating enzyme that deubiquitinates several targets in multiple signaling pathways. Stimulator of interferon genes (STING) is a critical adapter for the induction of interferon regulatory factor 3 (IRF3) phosphorylation and subsequent production of the cytokines in response to nucleic acids in the cytoplasm. Our studies demonstrate that YopJ targets STING to inhibit IRF3 signaling. Specially, YopJ interacts with STING to block its ER-to-Golgi traffic and remove its K63-linked ubiquitination chains. Deubiquited STING perturbs the formation of STING-TBK1 complex and the activation of IRF3. The 172th cysteine of YopJ mediated STING deubiquitination and IRF3 signaling inhibition. Consequently, mice infected with WT and ΔYopJ/YopJ bacteria induced lower levels of IRF3 and IFN-β, decreased inflammation and reduced staining of STING as compared to ΔYopJ and ΔYopJ/YopJ C172A strains infection. The data herein reveal a previously unrecognized mechanism by which YopJ modulates innate immune signaling.
SAGA complex and Gcn5 are necessary for respiration in budding yeast.
Canzonetta C, Leo M, Guarino SR … +3 more , Montanari A, Francisci S, Filetici P
Biochim Biophys Acta · 2016 Dec · PMID 27741413 · Publisher ↗
In budding yeast, growth through fermentation and/or respiration is dependent on the type of carbon source present in the medium. SAGA complex is the main acetylation complex and is required, together with Rtg factors, f...
In budding yeast, growth through fermentation and/or respiration is dependent on the type of carbon source present in the medium. SAGA complex is the main acetylation complex and is required, together with Rtg factors, for nucleus-mitochondria communication and transcriptional activation of specific nuclear genes. Even though acetylation is necessary for mitochondria activity and respiratory pathways the direct role of histone acetyltransferases and SAGA complex has never been investigated directly. In this study we demonstrate, for the first time, that Gcn5 and SAGA are needed for respiratory metabolism and oxygen consumption. According to a central role for acetylation in respiration we find that the Gcn5 inhibitor CPTH2 had higher efficacy on cells grown in glycerol containing media. We also demonstrated that the opposing activities of Gcn5 and Hda1 modify selectively H3-AcK18 and are essential for respiration. Taken together our results suggest a novel paradigm coupling acetyltransferase activity to respiratory metabolism. Correspondingly we propose the selective utilization of KAT inhibitor CPTH2, combined to the modulation of the respiratory metabolism of the cell, as a promising novel tool of intervention in cancer cells.
Nuclear PTEN interferes with binding of Ku70 at double-strand breaks through post-translational poly(ADP-ribosyl)ation.
Guan J, Zhao Q, Mao W
Biochim Biophys Acta · 2016 Dec · PMID 27741411 · Publisher ↗
PTEN is a tumor suppressor gene characterized as a phosphatase that antagonizes the phosphatidylinositol 3-kinase signaling pathway in the cytoplasm. Nuclear PTEN plays roles in chromosomal stability, in which the double...
PTEN is a tumor suppressor gene characterized as a phosphatase that antagonizes the phosphatidylinositol 3-kinase signaling pathway in the cytoplasm. Nuclear PTEN plays roles in chromosomal stability, in which the double-strand breaks (DSB) repair mediated by homologous recombination (HR) and non-homologous end joining (NHEJ) is critical. Herein, the role of nuclear PTEN in DSB repair and the underlying molecular mechanism was investigated in this study. Using human breast cancer BT549 and MDA-MB-231 cell lines, we reveal a specific feature of PTEN that controls poly(ADP-ribosyl)ation of Ku70 and interferes with binding of Ku70 at DSB. Plasmid-based end joining and reporter assays showed that nuclear PTEN restrained NHEJ efficacy. Electrophoretic mobility shift assays showed that nuclear PTEN impaired Ku70 complex binding to DSB by 3-fold. Co-immunoprecipitation assay showed PTEN regulated poly(ADP-ribosyl)ation of Ku70 instead of directly interacting with Ku70, while PTEN promoted the poly(ADP-ribosyl)ation of PARP1 and induced the degradation of PARP1 in PTEN-WT cells exposed to DSB agents. Of note, the role of PTEN in DSB repair mostly depends on its nuclear localization rather than its phosphatase activity. As a result, the absence of nuclear PTEN rather than phosphatase-negative PTEN confers cell hypersensitivity to anti-tumor DNA damage drugs. This finding contributes to understanding the effect of PTEN in repair of DSB and using defined anti-tumor DSB drugs to treat tumor cells with aberrant PTEN.
Inorganic cadmium affects the fluidity and size of phospholipid based liposomes.
Kerek EM, Prenner EJ
Biochim Biophys Acta · 2016 Dec · PMID 27736635 · Publisher ↗
Following intake and absorption of Cd into the bloodstream, one possible target is the lipid membrane surrounding erythrocytes as well as kidney and liver cells where Cd accumulates. We investigated the interactions of C...
Following intake and absorption of Cd into the bloodstream, one possible target is the lipid membrane surrounding erythrocytes as well as kidney and liver cells where Cd accumulates. We investigated the interactions of Cd with model membranes from a biophysical perspective by using fluorescence spectroscopy and dynamic light scattering to monitor changes in liposome size, membrane fluidity and lipid phase transition. The fluorescent probe Laurdan was incorporated into liposomes and used to quantitate cadmium induced fluidity changes in model systems hydrated in 20mM HEPES, 100mM NaCl pH7.4. The metal effects on membranes composed of the zwitterionic phosphatidylcholine were compared to the negatively charged lipids phosphatidic acid (PA), cardiolipin (CL), phosphatidylglycerol (PG), phosphatidylserine (PS) and phosphatidylinositol (PI). The data showed that 5-2000μM Cd electrostatically targeted negatively charged lipids and increased the rigidity of these membranes whereby the gel to liquid crystalline phase of fully saturated anionic lipids was increased following the order: PG>PS>CL~PA. In addition, dynamic light scattering showed that Cd induced liposome aggregation in all negatively charged systems except for the PGs. Moreover, both effects were much stronger for saturated acyl chains versus unsaturated species. Finally, charge localization was important as lipids carrying the charge more distant from the hydrophobic core of the bilayer showed stronger interactions with Cd.
Mechanical strain stimulates vasculogenesis and expression of angiogenesis guidance molecules of embryonic stem cells through elevation of intracellular calcium, reactive oxygen species and nitric oxide generation.
Sharifpanah F, Behr S, Wartenberg M … +1 more , Sauer H
Biochim Biophys Acta · 2016 Dec · PMID 27725190 · Publisher ↗
OBJECTIVES: Differentiation of embryonic stem (ES) cells may be regulated by mechanical strain. Herein, signaling molecules underlying mechanical stimulation of vasculogenesis and expression of angiogenesis guidance cues...
OBJECTIVES: Differentiation of embryonic stem (ES) cells may be regulated by mechanical strain. Herein, signaling molecules underlying mechanical stimulation of vasculogenesis and expression of angiogenesis guidance cues were investigated in ES cell-derived embryoid bodies. METHODS AND RESULTS: Treatment of embryoid bodies with 10% static mechanical strain using a Flexercell strain system significantly increased CD31-positive vascular structures and the angiogenesis guidance molecules plexinB1, ephrin B2, neuropilin1 (NRP1), semaphorin 4D (sem4D) and robo4 as well as vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2) and platelet-derived growth factor-BB (PDGF-BB) as evaluated by Western blot and real time RT-PCR. In contrast ephrin type 4 receptor B (EphB4) expression was down-regulated upon mechanical strain, indicating an arterial-type differentiation. Robo1 protein expression was modestly increased with no change in mRNA expression. Mechanical strain increased intracellular calcium as well as reactive oxygen species (ROS) and nitric oxide (NO). Mechanical strain-induced vasculogenesis was abolished by the NOS inhibitor L-NAME, the NADPH oxidase inhibitor VAS2870, upon chelation of intracellular calcium by BAPTA as well as upon siRNA inactivation of ephrin B2, NRP1 and robo4. BAPTA blunted the strain-induced expression of angiogenic growth factors, the increase in NO and ROS as well as the expression of NRP1, sem4D and plexinB1, whereas ephrin B2, EphB4 as well as robo1 and robo4 expression were not impaired. CONCLUSIONS: Mechanical strain stimulates vasculogenesis of ES cells by the intracellular messengers ROS, NO and calcium as well as by upregulation of angiogenesis guidance molecules and the angiogenic growth factors VEGF, FGF-2 and PDGF-BB.
Ligand binding affinity and changes in the lateral diffusion of receptor for advanced glycation endproducts (RAGE).
Syed A, Zhu Q, Smith EA
Biochim Biophys Acta · 2016 Dec · PMID 27720951 · Publisher ↗
The effect of ligand on the lateral diffusion of receptor for advanced glycation endproducts (RAGE), a receptor involved in numerous pathological conditions, remains unknown. Single particle tracking experiments that use...
The effect of ligand on the lateral diffusion of receptor for advanced glycation endproducts (RAGE), a receptor involved in numerous pathological conditions, remains unknown. Single particle tracking experiments that use quantum dots specifically bound to hemagglutinin (HA)-tagged RAGE (HA-RAGE) are reported to elucidate the effect of ligand binding on HA-RAGE diffusion in GM07373 cell membranes. The ligand used in these studies is methylglyoxal modified-bovine serum albumin (MGO-BSA) containing advanced glycation end products modifications. The binding affinity between soluble RAGE and MGO-BSA increases by 1.8 to 9.7-fold as the percent primary amine modification increases from 24 to 74% and with increasing negative charge on the MGO-BSA. Ligand incubation affects the HA-RAGE diffusion coefficient, the radius of confinement, and duration of confinement. There is, however, no correlation between MGO-BSA ligand binding affinity with soluble RAGE and the extent of the changes in HA-RAGE lateral diffusion. The ligand induced changes to HA-RAGE lateral diffusion do not occur when cholesterol is depleted from the cell membrane, indicating the mechanism for ligand-induced changes to HA-RAGE diffusion is cholesterol dependent. The results presented here serve as a first step in unraveling how ligand influences RAGE lateral diffusion.
Role of pannexin 1 in Clostridium perfringens beta-toxin-caused cell death.
Seike S, Takehara M, Kobayashi K … +1 more , Nagahama M
Biochim Biophys Acta · 2016 Dec · PMID 27720686 · Publisher ↗
BACKGROUND: Beta-toxin produced by Clostridium perfringens is a key virulence factor of fatal hemorrhagic enterocolitis and enterotoxemia. This toxin belongs to a family of β-pore-forming toxins (PFTs). We reported recen...
BACKGROUND: Beta-toxin produced by Clostridium perfringens is a key virulence factor of fatal hemorrhagic enterocolitis and enterotoxemia. This toxin belongs to a family of β-pore-forming toxins (PFTs). We reported recently that the ATP-gated P2X receptor interacts with beta-toxin. The ATP-release channel pannexin 1 (Panx1) is an important contributor to P2X receptor signaling. Hence, we investigated the involvement of Panx1 in beta-toxin-caused cell death. METHODS: We examined the effect of Panx1 in beta-toxin-induced cell death utilizing selective antagonists, knockdown of Panx1, and binding using dot-blot analysis. Localization of Panx1 and the P2X receptor after toxin treatment was determined by immunofluorescence staining. RESULTS: Selective Panx1 antagonists (carbenoxolone [CBX], probenecid, and Panx1 inhibitory peptide) prevented beta-toxin-caused cell death in THP-1 cells. CBX did not block the binding of the toxin to cells. Small interfering knockdown of Panx1 blocked beta-toxin-mediated cell death through inhibiting the oligomer formation of the toxin. Beta-toxin triggered a transient ATP release from THP-1 cells, but this early ATP release was blocked by CBX. ATP scavengers (apyrase and hexokinase) inhibited beta-toxin-induced cytotoxicity. Furthermore, co-administration of ATP with beta-toxin enhanced the binding and cytotoxicity of the toxin. CONCLUSIONS: Based on our results, Panx1 activation is achieved through the interaction of beta-toxin with the P2X receptor. Then, ATP released by the Panx1 channel opening promotes oligomer formation of the toxin, leading to cell death. GENERAL SIGNIFICANCE: Pannexin 1 is a novel candidate therapeutic target for beta-toxin-mediated disease.
Coarse-grained simulations of hemolytic peptide δ-lysin interacting with a POPC bilayer.
King MJ, Bennett AL, Almeida PF … +1 more , Lee HS
Biochim Biophys Acta · 2016 Dec · PMID 27720634 · Full text
δ-lysin, secreted by a Gram-positive bacterium Staphylococcus aureus, is a 26-residue membrane active peptide that shares many common features with antimicrobial peptides (AMPs). However, it possesses a few unique featur...
δ-lysin, secreted by a Gram-positive bacterium Staphylococcus aureus, is a 26-residue membrane active peptide that shares many common features with antimicrobial peptides (AMPs). However, it possesses a few unique features that differentiate itself from typical AMPs. In particular, δ-lysin has zero net charge, even though it has many charged residues, and it preferentially lyses eukaryotic cells over bacterial cells. Here, we present the results of coarse-grained molecular dynamics simulations of δ-lysin interacting with a zwitterionic membrane over a wide range of peptide concentrations. When the peptides concentration is low, spontaneous dimerization of peptides is observed on the membrane surface, but deep insertion of peptides or pore formation was not observed. However, the calculated free energy of peptide insertion suggests that a small fraction of peptides is likely to be present inside the membrane at the peptide concentrations typically seen in dye efflux experiments. When the simulations with multiple peptides are carried out with a single pre-inserted transmembrane peptide, spontaneous pore formation occurs with a peptide-to-lipid ratio (P/L) as low as P/L=1:42. Inter-peptide salt bridges among the transmembrane peptides seem to play a role in creating compact pores with very low level of hydration. More importantly, the transmembrane peptides making up the pore are constantly pushed to the opposite side of the membrane when the mass imbalance between the two sides of membrane is significant. Thus, the pore is very dynamic, allowing multiple peptides to translocate across the membrane simultaneously.
Eicosapentaenoic acid reduces membrane fluidity, inhibits cholesterol domain formation, and normalizes bilayer width in atherosclerotic-like model membranes.
Mason RP, Jacob RF, Shrivastava S … +2 more , Sherratt SCR, Chattopadhyay A
Biochim Biophys Acta · 2016 Dec · PMID 27718370 · Publisher ↗
Cholesterol crystalline domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol domain formation. We eva...
Cholesterol crystalline domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol domain formation. We evaluated non-peroxidation-mediated effects of eicosapentaenoic acid (EPA), other TG-lowering agents, docosahexaenoic acid (DHA), and other long-chain fatty acids on membrane fluidity, bilayer width, and cholesterol domain formation in model membranes. In membranes prepared at 1.5:1 cholesterol-to-phospholipid (C/P) mole ratio (creating pre-existing domains), EPA, glycyrrhizin, arachidonic acid, and alpha linolenic acid promoted the greatest reductions in cholesterol domains (by 65.5%, 54.9%, 46.8%, and 45.2%, respectively) compared to controls; other treatments had modest effects. EPA effects on cholesterol domain formation were dose-dependent. In membranes with 1:1 C/P (predisposing domain formation), DHA, but not EPA, dose-dependently increased membrane fluidity. DHA also induced cholesterol domain formation without affecting temperature-induced changes in-bilayer unit cell periodicity relative to controls (d-space; 57Å-55Å over 15-30°C). Together, these data suggest simultaneous formation of distinct cholesterol-rich ordered domains and cholesterol-poor disordered domains in the presence of DHA. By contrast, EPA had no effect on cholesterol domain formation and produced larger d-space values relative to controls (60Å-57Å; p<0.05) over the same temperature range, suggesting a more uniform maintenance of lipid dynamics despite the presence of cholesterol. These data indicate that EPA and DHA had different effects on membrane bilayer width, membrane fluidity, and cholesterol crystalline domain formation; suggesting omega-3 fatty acids with differing chain length or unsaturation may differentially influence membrane lipid dynamics and structural organization as a result of distinct phospholipid/sterol interactions.
Cytoplasmic RNA decay pathways - Enzymes and mechanisms.
Łabno A, Tomecki R, Dziembowski A
Biochim Biophys Acta · 2016 Dec · PMID 27713097 · Publisher ↗
RNA decay plays a crucial role in post-transcriptional regulation of gene expression. Work conducted over the last decades has defined the major mRNA decay pathways, as well as enzymes and their cofactors responsible for...
RNA decay plays a crucial role in post-transcriptional regulation of gene expression. Work conducted over the last decades has defined the major mRNA decay pathways, as well as enzymes and their cofactors responsible for these processes. In contrast, our knowledge of the mechanisms of degradation of non-protein coding RNA species is more fragmentary. This review is focused on the cytoplasmic pathways of mRNA and ncRNA degradation in eukaryotes. The major 3' to 5' and 5' to 3' mRNA decay pathways are described with emphasis on the mechanisms of their activation by the deprotection of RNA ends. More recently discovered 3'-end modifications such as uridylation, and their relevance to cytoplasmic mRNA decay in various model organisms, are also discussed. Finally, we provide up-to-date findings concerning various pathways of non-coding RNA decay in the cytoplasm.
Regulation of Mitofusin1 by Mahogunin Ring Finger-1 and the proteasome modulates mitochondrial fusion.
Mukherjee R, Chakrabarti O
Biochim Biophys Acta · 2016 Dec · PMID 27713096 · Publisher ↗
Health and homoeostasis are maintained by a dynamic balance between mitochondrial fission and fusion. Mitochondrial fusion machinery is largely unknown in mammals. Only a few reports have illustrated the role of Fzo1 in...
Health and homoeostasis are maintained by a dynamic balance between mitochondrial fission and fusion. Mitochondrial fusion machinery is largely unknown in mammals. Only a few reports have illustrated the role of Fzo1 in mitochondrial fusion known in Saccharomyces cerevisiae. We demonstrate that the ubiquitin ligase Mahogunin Ring Finger-1 (MGRN1) interacts with and constitutively ubiquitinates the mammalian homolog, Mitofusin1 (Mfn1) via K63 linkages. In mice models, loss of Mgrn1 function leads to severe developmental defects and adult-onset spongiform neurodegeneration, similar to prion diseases. The tethering of mitochondria to form the ~180kDa Mfn1 complex is independent of MGRN1-mediated ubiquitination. However, successful mitochondrial fusion requires formation of higher oligomers of Mfn1 which in turn needs GTPase activity, intact heptad repeats of Mfn1 and ubiquitination by MGRN1. Following ubiquitination, proteasomal processing of Mfn1 completes the mitochondrial fusion process. This step requires functional p97 activity. These findings suggest a sequence of events where GTPase activity of Mfn1 and tethering of adjacent mitochondria precedes its MGRN1-mediated ubiquitination and proteasomal degradation culminating in mitochondrial fusion.
Corrigendum to "The transport mechanism of the mitochondrial ADP/ATP carrier" [Biochim. Biophys. Acta 1863/10 (2016) 2379-2393].
Kunji ER, Aleksandrova A, King MS … +8 more , Majd H, Ashton VL, Cerson E, Springett R, Kibalchenko M, Tavoulari S, Crichton PG, Ruprecht JJ
Biochim Biophys Acta · 2016 Dec · PMID 27713079 · Publisher ↗
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Cardiac ankyrin repeat protein attenuates cardiomyocyte apoptosis by upregulation of Bcl-2 expression.
Zhang N, Ye F, Zhu W … +12 more , Hu D, Xiao C, Nan J, Su S, Wang Y, Liu M, Gao K, Hu X, Chen J, Yu H, Xie X, Wang J
Biochim Biophys Acta · 2016 Dec · PMID 27713078 · Publisher ↗
Cardiac ankyrin repeat protein (CARP) is a nuclear transcriptional co-factor that has additional functions in the myoplasm as a component of the muscle sarcomere. Previous studies have demonstrated increased expression o...
Cardiac ankyrin repeat protein (CARP) is a nuclear transcriptional co-factor that has additional functions in the myoplasm as a component of the muscle sarcomere. Previous studies have demonstrated increased expression of CARP in cardiovascular diseases, however, its role in cardiomyocyte apoptosis is unclear and controversial. In the present study, we investigated possible roles of CARP in hypoxia/reoxygenation (H/R) -induced cardiomyocyte apoptosis and the underlying mechanisms. Neonatal mouse ventricular cardiomyocytes were isolated and infected with adenovirus encoding Flag-tagged CARP (Ad-CARP) and lentivirus encoding CARP targeted shRNA (sh-CARP), respectively. Cardiomyocyte apoptosis induced by exposure to H/R conditions was evaluated by TUNEL staining and western blot analysis of cleaved caspase-3. The results showed that H/R-induced apoptosis was significantly decreased in Ad-CARP cardiomyocytes and increased in sh-CARP cardiomyocytes, suggesting a protective anti-apoptosis role for CARP. Interestingly, over-expressed CARP was mainly distributed in the nucleus, consistent with its role in regulating transcriptional activity. qPCR analysis showed that Bcl-2 transcripts were significantly increased in Ad-CARP cardiomyocytes. ChIP and co-IP assays confirmed the binding of CARP to the Bcl-2 promoter through interaction with transcription factor GATA4. Collectively, our results suggest that CARP can protect against H/R induced cardiomyocyte apoptosis, possibly through increasing anti-apoptosis Bcl-2 gene expression.
Differential subcellular distribution of four phospholipase C isoforms and secretion of GPI-PLC activity.
Staudt E, Ramasamy P, Plattner H … +1 more , Simon M
Biochim Biophys Acta · 2016 Dec · PMID 27693913 · Publisher ↗
Phospholipase C (PLC) is an important enzyme of signal transduction pathways by generation of second messengers from membrane lipids. PLCs are also indicated to cleave glycosylphosphatidylinositol (GPI)-anchors of surfac...
Phospholipase C (PLC) is an important enzyme of signal transduction pathways by generation of second messengers from membrane lipids. PLCs are also indicated to cleave glycosylphosphatidylinositol (GPI)-anchors of surface proteins thus releasing these into the environment. However, it remains unknown whether this enzymatic activity on the surface is due to distinct PLC isoforms in higher eukaryotes. Ciliates have, in contrast to other unicellular eukaryotes, multiple PLC isoforms as mammals do. Thus, Paramecium represents a perfect model to study subcellular distribution and potential surface activity of PLC isoforms. We have identified distinct subcellular localizations of four PLC isoforms indicating functional specialization. The association with different calcium release channels (CRCs) argues for distinct subcellular functions. They may serve as PI-PLCs in microdomains for local second messenger responses rather than free floating IP. In addition, all isoforms can be found on the cell surface and they are found together with GPI-cleaved surface proteins in salt/ethanol washes of cells. We can moreover show them in medium supernatants of living cells where they have access to GPI-anchored surface proteins. Among the isoforms we cannot assign GPI-PLC activity to specific PLC isoforms; rather each PLC is potentially responsible for the release of GPI-anchored proteins from the surface.
Inhibition of CDK7 bypasses spindle assembly checkpoint via premature cyclin B degradation during oocyte meiosis.
Wang H, Jo YJ, Sun TY … +4 more , Namgoong S, Cui XS, Oh JS, Kim NH
Biochim Biophys Acta · 2016 Dec · PMID 27693251 · Publisher ↗
To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) delays anaphase onset by preventing the premature activation of anaphase-promoting complex/cyclosome (APC/C) until all kinetochores are att...
To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) delays anaphase onset by preventing the premature activation of anaphase-promoting complex/cyclosome (APC/C) until all kinetochores are attached to the spindle. Although an escape from mitosis in the presence of unsatisfied SAC has been shown in several cancer cells, it has not been reported in oocyte meiosis. Here, we show that CDK7 activity is required to prevent a bypass of SAC during meiosis I in mouse oocytes. Inhibition of CDK7 using THZ1 accelerated the first meiosis, leading to chromosome misalignment, lag of chromosomes during chromosome segregation, and a high incidence of aneuploidy. Notably, this acceleration occurred in the presence of SAC proteins including Mad2 and Bub3 at the kinetochores. However, inhibition of APC/C-mediated cyclin B degradation blocked the THZ1-induced premature polar body extrusion. Moreover, chromosomal defects mediated by THZ1 were rescued when anaphase onset was delayed. Collectively, our results show that CDK7 activity is required to prevent premature anaphase onset by suppressing the bypass of SAC, thus ensuring chromosome alignment and proper segregation. These findings reveal new roles of CDK7 in the regulation of meiosis in mammalian oocytes.
Mastoparan is a membranolytic anti-cancer peptide that works synergistically with gemcitabine in a mouse model of mammary carcinoma.
Hilchie AL, Sharon AJ, Haney EF … +5 more , Hoskin DW, Bally MB, Franco OL, Corcoran JA, Hancock REW
Biochim Biophys Acta · 2016 Dec · PMID 27693190 · Full text
Anti-cancer peptides (ACPs) are small cationic and hydrophobic peptides that are more toxic to cancer cells than normal cells. ACPs kill cancer cells by causing irreparable membrane damage and cell lysis, or by inducing...
Anti-cancer peptides (ACPs) are small cationic and hydrophobic peptides that are more toxic to cancer cells than normal cells. ACPs kill cancer cells by causing irreparable membrane damage and cell lysis, or by inducing apoptosis. Direct-acting ACPs do not bind to a unique receptor, but are rather attracted to several different molecules on the surface of cancer cells. Here we report that an amidated wasp venom peptide, Mastoparan, exhibited potent anti-cancer activities toward leukemia (IC~8-9.2μM), myeloma (IC~11μM), and breast cancer cells (IC~20-24μM), including multidrug resistant and slow growing cancer cells. Importantly, the potency and mechanism of cancer cell killing was related to the amidation of the C-terminal carboxyl group. Mastoparan was less toxic to normal cells than it was to cancer cells (e.g., IC to PBMC=48μM). Mastoparan killed cancer cells by a lytic mechanism. Moreover, Mastoparan enhanced etoposide-induced cell death in vitro. Our data also suggest that Mastoparan and gemcitabine work synergistically in a mouse model of mammary carcinoma. Collectively, these data demonstrate that Mastoparan is a broad-spectrum, direct-acting ACP that warrants additional study as a new therapeutic agent for the treatment of various cancers.
TonB-dependent ligand trapping in the BtuB transporter.
Mills A, Le HT, Duong F
Biochim Biophys Acta · 2016 Dec · PMID 27693114 · Publisher ↗
TonB-dependent transporters are β-barrel outer membrane proteins occluded by a plug domain. Upon ligand binding, these transporters extend a periplasmic motif termed the TonB box. The TonB box permits the recruitment of...
TonB-dependent transporters are β-barrel outer membrane proteins occluded by a plug domain. Upon ligand binding, these transporters extend a periplasmic motif termed the TonB box. The TonB box permits the recruitment of the inner membrane protein complex TonB-ExbB-ExbD, which drives import of ligands in the cell periplasm. It is unknown precisely how the plug domain is moved aside during transport nor have the intermediate states between TonB recruitment and plug domain movement been characterized biochemically. Here we employ nanodiscs, native gel electrophoresis, and scintillation proximity assays to determine the binding kinetics of vitamin B to BtuB. The results show that ligand-bound BtuB recruits a monomer of TonB (TonB), which in turn increases retention of vitamin B within the transporter. The TonB box and the extracellular residue valine 90 that forms part of the vitamin B binding site are essential for this event. These results identify a novel step in the TonB-dependent transport process. They show that TonB binding to BtuB trap the ligand, possibly until the ExbB-ExbD complex is activated or recruited to ensure subsequent transport.
Altered regulation of the Spry2/Dyrk1A/PP2A triad by homocysteine impairs neural progenitor cell proliferation.
Rabaneda LG, Geribaldi-Doldán N, Murillo-Carretero M … +4 more , Carrasco M, Martínez-Salas JM, Verástegui C, Castro C
Biochim Biophys Acta · 2016 Dec · PMID 27686255 · Publisher ↗
Hyperhomocysteinemia reduces neurogenesis in the adult mouse brain. Homocysteine (Hcy) inhibits postnatal neural progenitor cell (NPC) proliferation by specifically impairing the fibroblast growth factor receptor (FGFR)-...
Hyperhomocysteinemia reduces neurogenesis in the adult mouse brain. Homocysteine (Hcy) inhibits postnatal neural progenitor cell (NPC) proliferation by specifically impairing the fibroblast growth factor receptor (FGFR)-Erk1/2-cyclin E signaling pathway. We demonstrate herein that the inhibition of FGFR-dependent NPC proliferation induced by Hcy is mediated by its capacity to alter the cellular methylation potential. Our results show that this alteration modified the expression pattern and activity of Sprouty2 (Spry2), a negative regulator of the above mentioned pathway. Both elevated concentrations of Hcy and methyltransferase activity inhibition induced Spry2 promoter demethylation in NPC cultures leading to a sustained upregulation of the expression of Spry2 mRNA and protein. In addition, protein levels of two kinases responsible for Spry2 activation/deactivation were altered by Hcy: Spry2 kinase Dyrk1A levels diminished while Spry2 phosphatase PP2A increased, leading to changes in the phosphorylation pattern, activity and stability of Spry2. In conclusion, Hcy inhibits NPC proliferation by indirect mechanisms involving alterations in DNA methylation, gene expression, and Spry2 function, causing FGFR signaling impairment.
The poly(ADP-ribosyl)ation of FoxO3 mediated by PARP1 participates in isoproterenol-induced cardiac hypertrophy.
Lu J, Zhang R, Hong H … +7 more , Yang Z, Sun D, Sun S, Guo X, Ye J, Li Z, Liu P
Biochim Biophys Acta · 2016 Dec · PMID 27686254 · Publisher ↗
The Forkhead box-containing protein, O subfamily 3 (FoxO3) transcription factor negatively regulates myocardial hypertrophy, and its transcriptional activity is finely conditioned by diverse posttranslational modificatio...
The Forkhead box-containing protein, O subfamily 3 (FoxO3) transcription factor negatively regulates myocardial hypertrophy, and its transcriptional activity is finely conditioned by diverse posttranslational modifications, such as phosphorylation, acetylation, ubiquitination, methylation and glycosylation. Here, we introduce a novel modification of the FoxO3 protein in cardiomyocytes: poly(ADP-ribosyl)ation (PARylation) mediated by poly(ADP-ribose) polymerase-1 (PARP1). This process catalyzes the NAD-dependent synthesis of polymers of ADP-ribose (PAR) and their subsequent attachment to target proteins by PARPs. Primary-cultured neonatal rat cardiomyocytes were incubated with isoproterenol (ISO) to induce hypertrophy, or were infected with recombinant adenovirus vectors harboring PARP1 cDNA (Ad-PARP1). Sprague-Dawley (SD) rats were treated with ISO to induce cardiac hypertrophy, or were injected with Ad-PARP1 into the anterior and posterior left ventricular walls. Cardiomyocyte surface area, the mRNA expression of hypertrophic biomarkers, echocardiography, morphometry of the hearts were measured. The PARP1 activity was tested by cellular PAR levels. Interactions of PARP1 and FoxO3 were investigated by co-immunoprecipitation and immunofluorescence technique. PARylation of FoxO3 mediated by PARP1 facilitated its phosphorylation at the T32, S252 and S314 sites, triggered its nucleus export and suppressed its transcriptional activity and target genes expression, ultimately inducing cardiac hypertrophy. Additionally, PARP1 silencing or specific inhibition by 3-Aminobenzamide (3AB) and veliparib (ABT-888) alleviated the inhibition of FoxO3 activity by ISO, thus suppressing ISO-induced cardiac hypertrophy. Our data provide the first evidence that PARP1 exacerbates cardiac hypertrophy by PARylation of FoxO3.
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