BBA - General Subjects (v.1780, #2)
Editorial Board (ii).
The Galα1,3Galβ1,4GlcNAc-R (α-Gal) epitope: A carbohydrate of unique evolution and clinical relevance by Bruce A. Macher; Uri Galili (75-88).
In 1985, we reported that a naturally occurring human antibody (anti-Gal), produced as the most abundant antibody (1% of immunoglobulins) throughout the life of all individuals, recognizes a carbohydrate epitope Galα1–3Galβ1–4GlcNAc-R (the α-gal epitope). Since that time, an extensive literature has developed on discoveries related to the α-gal epitope and the anti-Gal antibody, including the barrier they form in xenotransplantation and their reciprocity in mammalian evolution. This review covers these topics and new avenues of clinical importance related to this unique antigen/antibody system (α-gal epitope/anti-Gal) in improving the efficacy of viral vaccines and in immunotherapy against cancer.
Keywords: Anti-Gal; α-1,3galactosyltransferase; α-gal epitopes; Xenotransplantation; Cancer immunotherapy; Cancer vaccine; Viral vaccine;
The amino acids involved in the distinct carbohydrate specificities between macrophage galactose-type C-type lectins 1 and 2 (CD301a and b) of mice by Sarawut Oo-puthinan; Keisuke Maenuma; Masayoshi Sakakura; Kaori Denda-Nagai; Makoto Tsuiji; Ichio Shimada; Sachiko Nakamura-Tsuruta; Jun Hirabayashi; Nicolai V. Bovin; Tatsuro Irimura (89-100).
Binding specificities of mouse macrophage galactose-type C-type lectin 1 (MGL1/CD301a) and 2 (MGL2/CD301b) toward various oligosaccharides were compared by frontal affinity chromatography. MGL1 preferentially bound oligosaccharides containing LewisX (LeX) trisaccharides among 111 oligosaccharides tested, whereas MGL2 preferentially bound globoside Gb4. The important amino acids for the preferential bindings were investigated by pair-wise site-directed mutagenesis at positions 61, 89, 97, 100, 110–113, 115, 124, and 125 in the soluble recombinant carbohydrate recognition domains (CRD) prepared in Escherichia coli and purified with galactose-Sepharose. Mutations of Val, Ala, Thr, and Phe at positions 61, 89, 111 and 125 on MGL1 CRD caused reductions in LeX binding. Mutations of MGL2 CRD at Leu, Arg, Arg, and Tyr at positions 61, 89, 115 and 125 were implicated in the preference for β-GalNAc. LeX binding was observed with MGL2 mutants of Arg89Ala and Arg89Ala/Ser111Thr. MGL1 mutants of Ala89Arg and Ala89Arg/Pro115Arg showed β-GalNAc bindings. Molecular modeling illustrated potential direct molecular interactions of Leu61, Arg89, and His109 in MGL2 CRD with GalNAc.
Keywords: C-type lectin; Macrophage; Dendritic cells; Galactose; Carbohydrate recognition;
Mitochondrial dysfunction is responsible for the intestinal calcium absorption inhibition induced by menadione by Ana M. Marchionatti; Adriana V. Perez; Gabriela E. Diaz de Barboza; Beatriz M. Pereira; Nori G. Tolosa de Talamoni (101-107).
Menadione (MEN) inhibits intestinal calcium absorption by a mechanism not completely understood. The aim of this work was to find out the role of mitochondria in this inhibitory mechanism. Hence, normal chicks treated with one i.p. dose of MEN were studied in comparison with controls. Intestinal calcium absorption was measured by the in situ ligated intestinal segment technique. GSH, oxidoreductase activities from the Krebs cycle and enzymes of the antioxidant system were measured in isolated mitochondria. Mitochondrial membrane potential was measured by a flow cytometer technique. DNA fragmentation and cytochrome c localization were determined by immunocytochemistry. Data indicate that in 30 min, MEN decreases intestinal Ca2+ absorption, which returns to the control values after 10 h. GSH was only decreased for half an hour, while the activity of malate dehydrogenase and α-ketoglutarate dehydrogenase was diminished for 48 h. Mn2+-superoxide dismutase activity was increased in 30 min, whereas the activity of catalase and glutathione peroxidase remained unaltered. DNA fragmentation and cytochrome c release were maximal in 30 min, but were recovered after 15 h. In conclusion, MEN inhibits intestinal Ca2+ absorption by mitochondrial dysfunction as revealed by GSH depletion and alteration of the permeability triggering the release of cytochrome c and DNA fragmentation.
Keywords: Intestine; Mitochondria; Menadione; Calcium absorption; Apoptosis;
Dynamic and electrokinetic behavior of erythrocyte membrane in diabetes mellitus and diabetic cardiovascular disease by Sangeeta Adak; Subhankar Chowdhury; Maitree Bhattacharyya (108-115).
The dynamic and electrokinetic properties of erythrocyte membrane are explored as significant indices involved in the association of diabetes and diabetic cardiovascular disease. Lipid peroxidation studies reveal malondialdehyde concentration to reach a maximum in diabetic cardiovascular patients. Lower fluidity of erythrocyte membrane implies declined ability of erythrocyte to deform in pathogenic state, which is supported by decreased osmotic resistance. Membrane protein profile modification detected by Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) indicates a significant reduction in the quantity of ankyrin protein band 2.1 in diabetic subjects. In addition the reduction in an immunoreactive band against polyclonal anti-ankyrin antibody during Western blot analysis confirms the modification of ankyrin protein in diseased erythrocyte (reported for the first time). The electrokinetic behavior of erythrocyte membrane is monitored by laser Doppler velocimetry mode of the Nano-ZS. Changes in zeta potential values of the red blood cell membrane are consistent with decreased membrane fluidity in diseased erythrocytes (reported for the first time). Membrane potential values of control, diabetic and diabetic cardiovascular erythrocytes are − 37.24 ± 1.5 mV, − 28.44 ± 1.34 mV, and − 22.21 ± 1.21 mV respectively indicating a gradual lowering of zeta potential when erythrocyte membrane undergoes progressive changes – from simple agglomeration to fluid gel formation – and finally to a rigid gel.
Keywords: Hyperglycemia; Cardiovascular disease; Oxidative stress; Membrane fluidity; Zeta potential; Ankyrin;
Participation of chlorobiumquinone in the transplasma membrane electron transport system of Leishmania donovani promastigote: Effect of near-ultraviolet light on the redox reaction of plasma membrane by Shibendu Biswas; Rabiul Haque; Nihar R. Bhuyan; Tanmoy Bera (116-127).
The respiratory quinone composition of the parasitic protozoa Leishmania donovani promastigote was investigated. 1′-oxomenaquinone-7, a chlorobiumquinone was found to be the major isoprenoid quinone. Substantial level of ubiquinone-9 was also present. Isolation and identification of the quinone from the purified plasma membrane yielded mainly 1′-oxomenaquinone-7 and ubiquinone-9; menaquinone was not detected. Membrane bound 1′-oxomenaquinone-7 could be destroyed by near-ultraviolet irradiation, with a concomitant loss or stimulation of plasma membrane electron transport activities. The abilities of different quinones to restore α-lipoic acid and ferricyanide reductase activity in near UV-irradiated cell preparations were compared. The order was; conjugate of chlorobiumquinone and sphingosine base ≃ conjugate of 2-methyl-3-(1′-oxooctadecyl)-1,4-napthoquinone and octadecylamine >> chlorobiumquinone ≃ 2-methyl-3-(1′-oxooctadecyl)-1,4-napthoquinone > menaquinone-4 ≃ ubiquinone-10. After irradiation with near-UV light, transmembrane α-lipoic acid reduction was inhibited, while transmembrane ferricyanide reduction was stimulated. The result obtained indicates that chlorobiumquinone mediates the plasma membrane electron transport between cytosolic reductant and oxygen as well as α-lipoic acid. UV-inactivation of chlorobiumquinone shuts down the plasma membrane oxygen uptake and diverts the electron flux towards ferricyanide reduction via ubiquinone-9. Chlorobiumquinone is the only example of a polyisoprenoid quinone containing a side chain carbonyl group from photosynthetic green-sulphur bacteria. Recent work has revealed numerous genes of trypanosomatid sharing common ancestry with plants and/or bacteria. These observations pose some fascinating questions about the evolutionary biology of this important group of parasitic protozoa.
Keywords: Chlorobiumquinone; Synthesis of 2-methyl-3-(1′-oxooctadecyl)-1,4-napthoquinone; Ubiquinone; Leishmania; Plasma membrane; Transplasma membrane electron transport;
Kank proteins: A new family of ankyrin-repeat domain-containing proteins by Yun Zhu; Naoto Kakinuma; Yong Wang; Ryoiti Kiyama (128-133).
The human Kank gene was found as a candidate tumor suppressor for renal cell carcinoma, and encodes an ankyrin-repeat domain-containing protein, Kank. Here, we report a new family of proteins consisting of three Kank (Kank1)-associated members, Kank2, Kank3 and Kank4, which were found by domain and phylogenetic analyses. Besides the conserved ankyrin-repeat and coiled-coil domains, there was a conserved motif at the N-terminal (KN motif) containing potential motifs for nuclear localization and export signals. Gene expression of these genes was examined by RT-PCR at the mRNA level and by Western blotting and immunostaining at the protein level. Kank family genes showed variations in the expression level among tissues and kidney cell lines. Furthermore, the results of overexpression of these genes in NIH3T3 cells suggest that all of these family proteins have an identical role in the formation of actin stress fibers.
Keywords: Kank family protein; Ankyrin repeat; Coiled-coil domain; Actin stress fiber;
Toll-like receptor 4 and cytokine expression involved in functional immune response in an originally established porcine intestinal epitheliocyte cell line by Masayuki Moue; Masanori Tohno; Tomoyuki Shimazu; Taketomo Kido; Hisashi Aso; Tadao Saito; Haruki Kitazawa (134-144).
To study the immune responses of porcine intestinal epithelial cells to gram-negative bacteria via toll-like receptors (TLRs), originally established porcine intestinal epitheliocyte (PIE) cells were treated with lipopolysaccharide (LPS) or swine-specific enterotoxigenic Escherichia coli (ETEC). Real-time quantitative PCR revealed that PIE cells expressed TLR1-9 and MD-2 mRNAs, preferentially expressed TLR4/MD-2. Immunostaining of PIE cells revealed that TLR4 was precisely expressed in PIE cells at the protein level. PIE cells treated with LPS had up-regulated expression of several TLRs (TLR2, 3, 4, 5 and 8), type 1 helper T (Th1) cytokines (interleukin (IL)-1α, IL-1β, IL-6, IL-15, 18, leukemia inhibitory factor (LIF), and interferon (IFN)-β), and chemokines (monocyte chemoattractant protein (MCP)-1 and IL-8). ETEC enhanced the expression of TLR2, Th1 type cytokines (IL-1α, IL-12p35 and IL-6) and chemokines (MCP-1 and IL-8). These results indicate that PIE induces inflammatory responses by up-regulating Th1 cytokines and chemokines in response to LPS or ETEC, suggesting that PIE is a useful cell line for studying inflammatory responses via TLR4/MD-2 in intestinal epithelial cells.
Keywords: Toll-like receptor; Cytokine; Porcine; Intestinal epitheliocyte;
Macrophage apolipoprotein-E knockdown modulates caspase-3 activation without altering sensitivity to apoptosis by David A. Elliott; Woojin S. Kim; David A. Jans; Brett Garner (145-153).
Apolipoprotein-E (apoE) expression may be associated with apoptosis resistance. Since macrophages constitutively synthesize apoE we speculated that this may contribute to apoptosis resistance. Using siRNA, human monocyte derived macrophage (hMDM) apoE mRNA and protein was reduced by 97% and 61%, respectively. ApoE knockdown increased staurosporine-induced caspase-3 activation by 78% without altering cell survival or apoptosis as assessed by TUNEL analysis and morphological changes. This result was confirmed using murine bone marrow derived macrophages (mBMDM) from apoE null and wild type mice. In these experiments, staurosporine-induced caspase-3 activation was increased by 49% in apoE null compared to wild type mBMDM and this was not associated with differences in TUNEL signal, annexin-V binding or DNA fragmentation. ApoE is also important for cholesterol transport and macrophage cholesterol can regulate apoptosis. Knockdown of hMDM apoE inhibited basal cholesterol efflux by 20% without altering apolipoprotein-AI mediated cholesterol efflux over 24 h. Similarly, in apoE null mBMDM a non significant trend for a 16% reduction in basal cholesterol efflux was observed as compared to wild type mBMDM. In conclusion, apoE expression modulates capase-3 activity, but this has no significant impact on sensitivity to apoptosis and only a moderate impact on basal cholesterol efflux.
Keywords: Apolipoprotein-E; siRNA; Macrophage; Caspase-3; Apoptosis; Cholesterol-efflux;
Endothelin-1 induction of Glut1 transcription in 3T3-L1 adipocytes involves distinct PKCε- and p42/p44 MAPK-dependent pathways by Ying-Shiun Kao; Jim C. Fong (154-159).
We have shown previously that chronic exposure to endothelin-1 (ET-1) may stimulate GLUT1-mediated glucose transport in 3T3-L1 adipocytes via both protein kinase C (PKC)- and mitogen-activated protein kinase (p42/p44 MAPK)-dependent pathways. In the present study, by using a luciferase reporter driven by Glut1 promoter and enhancers (pLuc-GT1/E1/E2) and various constitutively active and dominant negative mutants of PKC isoforms, we identified PKCε as the PKC isoform involved. In addition, we provide evidence that there is no direct interaction between ET-1 activated PKCε and MAPK, at least at the kinase activity level. Furthermore, investigations employing deletion mutants of pLuc-GT1/E1/E2 to locate the putative ET-1 responsive sites and inhibitory agents to suppress the activities of putative transcription factors suggested that transcription factors CREB, Sp1 and NF-κB were involved. In summary, the results of this study indicate that ET-1 induction of Glut1 transcription involves distinct PKCε- and MAPK-dependent pathways, as well as downstream transcription factors CREB, Sp1 and NF-κB.
Keywords: 3T3-L1 adipocyte; Glucose transport; PKC; MAPK; GLUT1; Endothelin-1;
Apoptosis as a mechanism for removal of mutated cells of Saccharomyces cerevisiae: The role of Grx2 under cadmium exposure by Débora Silva Gomes; Marcos Dias Pereira; Anita Dolly Panek; Leonardo Rodrigues Andrade; Elis Cristina Araújo Eleutherio (160-166).
Cadmium is a strong mutagen that acts by inhibiting DNA mismatch repair, while its toxic effect seems to be related to an indirect oxidative stress that involves glutathione (GSH) mobilization. Among the roles of GSH is the protection of proteins against oxidative damage, by forming reversible mixed disulfides with cysteine residues, a process known as protein glutathionylation and catalyzed by glutaredoxins (Grx). In this current study, Saccharomyces cerevisiae cells deficient in GRX2, growing in 80 μM CdSO4, showed high mitochondrial mutagenic rate, determined by frequency of mutants that had lost mitochondrial function (petite mutants), high tolerance and lower apoptosis induction. The mutant strain also showed decreased levels of glutathionylated-protein after cadmium exposure, which might difficult the signaling to apoptosis, leading to increased mutagenic rates. Taken together, these results suggest that Grx2 is involved with the apoptotic death induced by cadmium, a form of cellular suicide that might lead of removal of mutated cells.
Keywords: Glutathionylation; Grx2; Petite; Apoptosis; Cadmium; Saccharomyces cerevisiae;
Identification, cloning and functional characterization of a novel dermonecrotic toxin (phospholipase D) from brown spider (Loxosceles intermedia) venom by Marcia Helena Appel; Rafael Bertoni da Silveira; Olga Meiri Chaim; Kátia Sabrina Paludo; Dilza Trevisan Silva; Daniele M. Chaves; Paulo Henrique da Silva; Oldemir C. Mangili; Andrea Senff-Ribeiro; Waldemiro Gremski; Helena B. Nader; Silvio Sanches Veiga (167-178).
Brown spider bites are associated with lesions including dermonecrosis, gravitational spreading and a massive inflammatory response, along with systemic problems that may include hematological disturbances and renal failure. The mechanisms by which the venom exerts its noxious effects are currently under investigation. It is known that the venom contains a major toxin (dermonecrotic toxin, biochemically a phospholipase D) that can experimentally induce dermonecrosis, inflammatory response, animal mortality and platelet aggregation. Herein, we describe cloning, heterologous expression, purification and functionality of a novel isoform of the 33 kDa dermonecrotic toxin. Circular dichroism analysis evidenced correct folding for the toxin. The recombinant toxin was recognized by whole venom serum antibodies and by a specific antibody to a previously described dermonecrotic toxin. The identified toxin was found to display phospholipase activity and dermonecrotic properties. Additionally, the toxin caused a massive inflammatory response in rabbit skin dermis, evoked platelet aggregation, increased vascular permeability, caused edema and death in mice. These characteristics in combination with functional studies for other dermonecrotic toxins illustrate that a family of dermonecrotic toxins exists, and includes a novel member with high activity that may be useful for future structural and functional studies.
Keywords: Dermonecrotic toxin; Phospholipase D; Sphingomyelinase; Loxosceles; Venom;
Effect of low pH on organization of the actin cytoskeleton in Saccharomyces cerevisiae by M. Motizuki; S. Yokota; K. Tsurugi (179-184).
Cell growth in the yeast Saccharomyces cerevisiae depends on polarization of the actin cytoskeleton. In this study, we investigated how the cell regulates the distribution of actin in response to low pH conditions, focusing on the role of mitogen-activated protein kinases, Hog1 and Slt2. Changing the extracellular pH from 6.0 to 3.0 caused a transient depolarization of the actin cytoskeleton. Actin cables were no longer visible, and actin patches appeared randomly distributed after 30 min at pH 3.0. The deletion strain hog1Δ did not show this low-pH phenotype, suggesting that Hog1 is involved in depolarization of the actin cytoskeleton in response to low-pH stress. Yeast cells incubated at pH 3.0 also showed markedly increased endocytosis compared with the control at neutral pH, as indicated by the uptake of Lucifer Yellow (LY). Both the hog1Δ and slt2Δ mutants took up LY into the vacuole to a similar extent as the wild-type strain. In addition, cells grown at pH 3.0 showed a 2-fold increase in phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) levels, as did the hog1Δ or slt2Δ cells. Efficient uptake of LY and actin repolarization at pH 3.0 might therefore require activation of PI(4,5)P2 synthesis.
Keywords: Saccharomyces cerevisiae; Low pH; Cell wall stress; Actin polarization; Endocytosis; Mitogen activated protein kinase; PI(4,5)P2; Actin cytoskeleton; MAP kinase; Yeast;
Regulation of Akt during hibernation in Richardson's ground squirrels by Khalil Abnous; Christopher A. Dieni; Kenneth B. Storey (185-193).
Akt (or protein kinase B) plays a central role in coordinating growth, survival and anti-apoptotic responses in cells and we hypothesized that changes in Akt activity and properties would aid the reprioritization of metabolic functions that occurs during mammalian hibernation. Akt was analyzed in skeletal muscle and liver of Richardson's ground squirrels, Spermophilus richardsonii, comparing the enzyme from euthermic and hibernating states. Akt activity, measured with a synthetic peptide substrate, decreased by 60–65% in both organs during hibernation. Western blotting showed that total Akt protein did not change in hibernation but active, phosphorylated Akt (Ser 473) was reduced by 40% in muscle compared with euthermic controls and was almost undetectable in liver. Kinetic analysis of muscle Akt showed that S 0.5 values for Akt peptide were 28% lower during hibernation, compared with the euthermic enzyme, whereas S 0.5 ATP increased by 330%. Assay at 10 °C also elevated S 0.5 ATP of euthermic Akt by 350%. Changes in ATP affinity would limit Akt function in the hibernator since the muscle adenylate pool size is also strongly suppressed during cold torpor. Other parameters of euthermic and hibernator Akt were the same including activation energy calculated from Arrhenius plots and sensitivity to urea denaturation. DEAE Sephadex chromatography of muscle extracts revealed three peaks of Akt activity in euthermia but only two during hibernation suggesting isozymes are differentially dephosphorylated during torpor. Altered enzyme properties and suppression of Akt activity would contribute to the coordinated suppression of energy-expensive anabolic and growth processes that is needed to maintain viability during over weeks of winter torpor.
Keywords: Protein kinase B; Metabolic rate depression; Torpor; Reversible protein phosphorylation; Spermophilus richardsonii;
Regulation of hyaluronan and versican deposition by growth factors in fibrosarcoma cell lines by A. Berdiaki; A. Zafiropoulos; E. Fthenou; P. Katonis; A. Tsatsakis; N.K. Karamanos; G.N. Tzanakakis (194-202).
Versican, a large chondroitin sulphate proteoglycan and hyaluronan (HA), a non-sulphated glycosaminoglycan are major constituents of the pericellular matrix. In many neoplastic tissues, changes in the expression of versican and HA affect tumour progression. Here, we analyse the synthesis of versican and hyaluronan by fibrosarcoma cells, and document how the latter is affected by PDGF-BB, bFGF and TGFB2, growth factors endogenously produced by these cells. Fibrosarcoma cell lines B6FS and HT1080 were utilised and compared with normal lung fibroblasts (DLF). The major versican isoforms expressed by DLF and B6FS cells were V0 and V1. Treatment of B6FS cells with TGFB2 showed a significant increase of V0 and V1 mRNAs. Versican expression in HT1080 cells was not significantly affected by any of the growth factors. In addition, TGFB2 treatment increased versican protein in DLF cells. HA, showed approximately a 2-fold and a 9-fold higher production in DLF cells compared to B6FS and HT1080 cells, respectively. In HT1080 cells, HA biosynthesis was significantly increased by bFGF, whereas, in B6FS cells it was increased by TGFB2 and PDGF-BB. Furthermore, analysis of HA synthases (HAS) expression indicated that HT1080 expressed similar levels of all three HAS isoforms in the following order: HAS2> HAS3> HAS1. bFGF shifted that balance by increasing the abundance of HAS1. The major HAS isoform expressed by B6FS cells was HAS2. PDGF-BB and TGFB2 showed the most prominent effects by increasing both HAS2 and HAS1 isoforms. In conclusion, these growth factors modulated, through upregulation of specific HAS isoforms, HA synthesis, secretion and net deposition to the pericellular matrix.
Keywords: Fibrosarcoma; Versican; Hyaluronan; Basic fibroblast growth factor; Transforming growth factor B2; Platelet derived growth factor BB; Hyaluronan synthases;
Coenzyme Q10 as a potent compound that inhibits Cdt1–geminin interaction by Yoshiyuki Mizushina; Toshifumi Takeuchi; Yoichi Takakusagi; Yuko Yonezawa; Takeshi Mizuno; Ken-ichiro Yanagi; Naoko Imamoto; Fumio Sugawara; Kengo Sakaguchi; Hiromi Yoshida; Masatoshi Fujita (203-213).
A human replication initiation protein Cdt1 is a very central player in the cell cycle regulation of DNA replication, and geminin down-regulates Cdt1 function by directly binding to it. It has been demonstrated that Cdt1 hyperfunction resulting from Cdt1–geminin imbalance, for example by geminin silencing with siRNA, induces DNA re-replication and eventual cell death in some cancer-derived cell lines. In the present study, we first established a high throughput screening system based on modified ELISA (enzyme linked immunosorbent assay) to identify compounds that interfere with human Cdt1–geminin binding. Using this system, we found that coenzyme Q10 (CoQ10) can inhibit Cdt1–geminin interaction in vitro. CoQ compound is an isoprenoid quinine that functions as an electron carrier in the mitochondrial respiratory chain in eukaryotes. CoQ10, having a longer isoprenoid chain, was the strongest inhibitor of Cdt1–geminin binding in the tested CoQs, with 50% inhibition observed at concentrations of 16.2 μM. Surface plasmon resonance analysis demonstrated that CoQ10 bound selectively to Cdt1, but did not interact with geminin. Moreover, CoQ10 had no influence on the interaction between Cdt1 and mini-chromosome maintenance (MCM)4/6/7 complexes. These results suggested that CoQ10 inhibits Cdt1–geminin complex formation by binding to Cdt1 and thereby could liberate Cdt1 from inhibition by geminin. Using three-dimensional computer modeling analysis, CoQ10 was considered to interact with the geminin interaction interface on Cdt1, and was assumed to make hydrogen bonds with the residue of Arg243 of Cdt1. CoQ10 could prevent the growth of human cancer cells, although only at high concentrations, and it remains unclear whether such an inhibitory effect is associated with the interference with Cdt1–geminin binding. The application of inhibitors for the formation of Cdt1–geminin complex is discussed.
Keywords: Coenzyme Q10; Cdt1; Geminin; Cdt1–geminin complex; The binding inhibitor; Docking simulation; Interaction interface;
RNA association or phosphorylation of the RS domain prevents aggregation of RS domain-containing proteins by Eleni Nikolakaki; Victoria Drosou; Ioannis Sanidas; Philippos Peidis; Thomais Papamarcaki; Lilia M. Iakoucheva; Thomas Giannakouros (214-225).
Domains rich in alternating arginine and serine residues (RS domains) are found in a large number of eukaryotic proteins involved in several cellular processes. According to the prevailing view RS domains function as protein interaction domains, thereby promoting the assembly of higher-order cellular structures. Furthermore, recent data demonstrated that the RS regions of several SR splicing factors directly contact the pre-mRNA in a nonsequence specific but functionally important fashion. Using a variety of biochemical approaches, we now demonstrate that the RS domains of three proteins, not directly associated with the splicing reaction, such as lamin b receptor, acinus and peroxisome proliferator-activated receptor gamma coactivator-1 alpha, associate mainly with nuclear RNA and that this association is conducive in retaining the proteins in a soluble form. Phosphorylation by SRPK1 prevents RNA association, yet it greatly increases the fraction of the proteins recovered in soluble form, thereby mimicking the RNA effect. Based on these results we propose that the tendency to self-associate and form aggregates is a general property of RS domain-containing proteins and could be attributed to their disordered structure. RNA binding or SRPK1-mediated phosphorylation prevents aggregation and may serve to modulate the RS domain interaction modes.
Keywords: RS domain; LBR; Acinus; PGC-1a; SRPK1; Intrinsic disorder;
Periplasmic Cu,Zn superoxide dismutase and cytoplasmic Dps concur in protecting Salmonella enterica serovar Typhimurium from extracellular reactive oxygen species by Francesca Pacello; Pierpaolo Ceci; Serena Ammendola; Paolo Pasquali; Emilia Chiancone; Andrea Battistoni (226-232).
Several bacteria possess periplasmic Cu,Zn superoxide dismutases which can confer protection from extracellular reactive oxygen species. Thus, deletion of the sodC1 gene reduces Salmonella enterica serovar Typhimurium ability to colonize the spleens of wild type mice, but enhances virulence in p47phox mutant mice. To look into the role of periplamic Cu,Zn superoxide dismutase and into possible additive effects of the ferritin-like Dps protein involved in hydrogen peroxide detoxification, we have analyzed bacterial survival in response to extracellular sources of superoxide and/or hydrogen peroxide. Exposure to extracellular superoxide of Salmonella Typhimurium mutant strains lacking the sodC1 and sodC2 genes and/or the dps gene does not cause direct killing of bacteria, indicating that extracellular superoxide is poorly bactericidal. In contrast, all mutant strains display a sharp hydrogen peroxide-dependent loss of viability, the dps,sodC1,sodC2 mutant being less resistant than the dps or the sodC1,sodC2 mutants. These findings suggest that the role of Cu,Zn superoxide dismutase in bacteria is to remove rapidly superoxide from the periplasm to prevent its reaction with other reactive molecules. Moreover, the nearly additive effect of the sodC and dps mutations suggests that localization of antioxidant enzymes in different cellular compartments is required for bacterial resistance to extracytoplasmic oxidative attack.
Keywords: Cu,Zn superoxide dismutase; Dps, sodC, Salmonella enterica; Oxidative damage; NADPH oxidase;
Factors affecting struvite (MgNH4PO4·6H2O) crystallization in feline urine by Kayo Matsumoto; Masayuki Funaba (233-239).
Factors affecting struvite, a magnesium–ammonium–phosphate complex (MgNH4PO4 • 6H2O), in feline urine were evaluated. Incubation of just “urine mineral (UM)” solution, in which mineral concentrations are compatible with those in feline urine, for 4 h at 37 °C did not induce the formation of crystals. Similarly, incubation of urine alone did not produce crystals. However, struvite crystals were formed by the addition of urine to UM solution. Mg, NH3 and P were all required for urine-induced struvite crystallization. The lower molecular weight (LMW) fraction of urine was essential for struvite crystal formation, and the higher molecular weight (HMW) fraction enhanced formation of LMW-induced struvite crystals. The effects of urine proteins further fractionated by column chromatography were examined. A protein at > 250 kDa and cauxin, a major urine protein recently identified as a regulator of felinine production, potentiated struvite crystal formation induced by the LMW fraction. In contrast, Tamm–Horsfall glycoprotein, a urine protein thought to promote struvite crystallization, did not have this activity. The present study reveals a novel mechanism of feline struvite crystallization.
Keywords: Struvite; Crystal; Protein; Cauxin; Tamm–Horsfall glycoprotein; Cat;
Neuronal calcium sensor proteins are unable to modulate NFAT activation in mammalian cells by Daniel J. Fitzgerald; Robert D. Burgoyne; Lee P. Haynes (240-248).
Calcium activated gene transcription through Nuclear Factor of Activated T-cells, (NFAT) proteins, is emerging as a ubiquitous mechanism for the control of important physiological processes. Of the five mammalian NFAT isoforms, transcriptional activities of NFATs 1-4 are stimulated by a calcium driven association between the ubiquitous phosphatase calcineurin and the calcium-sensing protein calmodulin. Published in vitro evidence has suggested that other members of the calmodulin super-family, in particular the neuronal calcium sensor (NCS) proteins, can similarly modulate calcineurin activity. In this study we have assessed the ability of NCS proteins to interact directly with calcineurin in vitro and report a specific if weak association between various NCS proteins and the phosphatase. In an extension to these analyses we have also examined the effects of over-expression of NCS-1 or NCS-1 mutants on calcineurin signalling in HeLa cells in experiments examining the dephosphorylation of an NFAT-GFP reporter construct as a readout of calcineurin activity. Results from these experiments indicate that NCS-1 was not able to detectably modulate calcineurin/NFAT signalling in a live mammalian cell system, findings that are consistent with the idea that calmodulin and not NCS-1 or other NCS family proteins is the physiologically relevant modulator of calcineurin activity.
Keywords: NCS family proteins; Calmodulin; Calcineurin activity; NFAT signaling;
N-acetylcysteine amide (AD4) attenuates oxidative stress in beta-thalassemia blood cells by Johnny Amer; Daphne Atlas; Eitan Fibach (249-255).
Many aspects of the pathology in β-hemoglobinopathies (β-thalassemia and sickle cell anemia) are mediated by oxidative stress. In the present study we tested a novel thiol compound, N-acetylcysteine amide (AD4), the amide form of N-acetyl cysteine (NAC) for its antioxidant effects. Using flow-cytometry, we showed that in vitro treatment of blood cells from β-thalassemic patients with AD4 elevated the reduced glutathione (GSH) content of red blood cells (RBC), platelets and polymorphonuclear (PMN) leukocytes, and reduced their ROS. These effects resulted in a significant reduced sensitivity of thalassemic RBC to hemolysis and phagocytosis by macrophages. Intra-peritoneal injection of AD4 to β-thalassemic mice (150 mg/kg) reduced the parameters of oxidative stress (p < 0.001). Our results show the superiority of AD4, compared to NAC, in reducing oxidative stress markers in thalassemic cells both in vitro and in vivo.
Keywords: Hemoglobinopathies; Free radicals; Oxidative stress; N-acetylcysteine amide; Reduced glutathione; Flow cytometry;
Characterization of a novel vanadium-binding protein (VBP-129) from blood plasma of the vanadium-rich ascidian Ascidia sydneiensis samea by Masao Yoshihara; Tatsuya Ueki; Nobuo Yamaguchi; Kei Kamino; Hitoshi Michibata (256-263).
The ascidians, the so-called sea squirts, accumulate high levels of vanadium, a transition metal. Since Henze first observed this physiologically unusual phenomenon about one hundred years ago, it has attracted interdisciplinary attention from chemists, physiologists, and biochemists. The maximum concentration of vanadium in ascidians can reach 350 mM, and most of the vanadium ions are stored in the + 3 oxidation state in the vacuoles of vanadium-accumulating blood cells known as vanadocytes. Many proteins involved in the accumulation and reduction of vanadium in the vanadocytes, blood plasma, and digestive tract have been identified. However, the process by which vanadium is taken in prior to its accumulation in vanadocytes has not been elucidated. In the present study, a novel vanadium-binding protein, designated VBP-129, was identified from blood plasma of the vanadium-rich ascidian Ascidia sydneiensis samea. Although VBP-129 mRNA was transcribed in all A. sydneiensis samea tissues examined, the VBP-129 protein was exclusively localized in blood plasma and muscle cells of this ascidian. It bound not only to VO2+ but also to Fe3+, Co2+, Cu2+, and Zn2+; on the other hand, a truncated form of VBP-129, designated VBP-88, bound only to Co2+, Cu2+ and Zn2+. In a pull-down assay, an interaction between VanabinP and VBP-129 occurred both in the presence and the absence of VO2+. These results suggest that VBP-129 and VanabinP function cooperatively as metallochaperones in blood plasma.
Keywords: Ascidian; Vanadium; Metal accumulation; Blood plasma;
Differential regulation of apolipoprotein A-I gene expression by vitamin D receptor modulators by Kent R. Wehmeier; Angela Mazza; Sahar Hachem; Ken Ligaray; Arshag D. Mooradian; Norman C.W. Wong; Michael J. Haas (264-273).
We have found that 1,25-dihydroxy-cholecalciferol (1,25-(OH)2D3) represses the expression of the apolipoprotein A-I (apo A-I) gene in hepatocytes. In this manuscript we examined the effects of the vitamin D receptor (VDR) modulators EB1089 (EB) and ZK191784 (ZK) on expression of the apo A-I gene in liver (HepG2) and in intestinal (Caco-2) cells. In HepG2 cells, EB and ZK induced apo A-I secretion and gene promoter activity in a dose-dependent manner. This induction did not require the VDR since antisense-mediated inhibition of VDR had no appreciable effect on apo A-I promoter activity in cells treated with EB or ZK. Although repression of apo A-I gene expression by 1,25-(OH)2D3 in hepatocytes required nuclear receptor binding to site A in the promoter, this cis-element was insufficient for induction of apo-AI by EB and ZK. In Caco-2 cells, treatment with 1,25-(OH)2D3 had no effect on apo A-I protein secretion or promoter activity while EB induced and ZK inhibited apo A-I gene expression. Gel shift assays showed that none of the treatments resulted in a change in site A binding activity. These results indicate that VDR modulators in hepatocytes and intestinal cells differentially regulate expression of the apo A-I gene.
Keywords: Apolipoprotein A-I; Vitamin D; Gene expression; Receptor modulator;
U7 snRNA acts as a transcriptional regulator interacting with an inverted CCAAT sequence-binding transcription factor NF-Y by Takashi Higuchi; Kaijiro Anzai; Shunsuke Kobayashi (274-281).
An inverted CCAAT sequence is recognized by both transcription factors NF-Y and DNA/RNA binding protein YB-1. In the process of examining the effect of nuclear RNA on an inverted CCAAT-containing promoter of MDR1 gene, we found that U7 snRNA inhibits NF-Y and suppresses the promoter activity both in vitro and in NG108-15 tumor cells. Analysis using a designed RNA, which was structurally unrelated to U7 snRNA, revealed that RNA binding by YB-1 is not specific and that the protein is not involved in the transcription. Furthermore, we demonstrated that in the nucleus of doxorubicin-treated cells, DNA binding by NF-Y and transcriptional activity of the promoter were inhibited without either a decrease of NF-Y or an increase of the p53 tumor suppressor, which is known to inhibit DNA binding by NF-Y. In these cells, U7 snRNA was specifically increased and associated with NF-Y, and treatment with RNase A eliminated the inhibition of NF-Y activity. These results suggest that U7 snRNA has a novel function as a transcriptional regulator to control NF-Y.
Keywords: U7 snRNA; Inverted CCAAT sequence; NF-Y; Transcriptional regulator;
DNA–DNA cross-linking mediated by bifunctional [SalenAlIII]+ complex by Arivazhagan Rajendran; Chinnian J. Magesh; Paramasivan T. Perumal (282-288).
The aluminum (III) complex [SalenAlIII]Cl (1), (Salen = (R,R)-N,N′-bis[5-methyl-3-(4-methylpiperazinyl)-salicylidene]-1,2-diphenylethanediamine) has been synthesized and characterized by elemental analysis, FT-IR, 1H and 13C NMR measurements. The interaction of complex (1) with calf thymus (CT) DNA has been studied extensively by experimental techniques. Thermal denaturation study of DNA with (1) revealed the ΔT m of 5 ± 0.2 °C. Viscosity and steady-state fluorescence measurements showed that the complex cross-links DNA and the metal center is interacting with DNA during the cross-linking. Also, the phenyl ring in the complex may intercalate between the base pairs of the DNA during the cross-linking. Competitive binding study shows that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of the metal complex indicating that it displaces EB from its binding site in DNA and the apparent binding constant has been estimated to be (2.8 ± 0.2) × 105 M− 1. Further, time-resolved fluorescence experiments confirm the binding of (1) with DNA and its cross-linking nature. Aluminum ions shown to precipitate DNA completely above the pH 6.0, but no such precipitation was observed with complex (1). The DNA–DNA cross-linking mediated by (1) is further confirmed by gel electrophoresis.
Keywords: Metal–Salen complex; Al(III) complex; DNA-binding; DNA–DNA cross-linking;
Aggregation dependent enhancement of trehalose-6-phosphate synthase activity in Saccharomyces cerevisiae by Paramita Chaudhuri; Arghya Basu; Anil K. Ghosh (289-297).
Trehalose-6-phosphate synthase (TPS) is one of the key subunits of the trehalose synthase complex, responsible for synthesis of trehalose in Saccharomyces cerevisiae. Different laboratories have tried to purify TPS, but have been unable to separate it from the complex. During the present study, active TPS has been isolated from the trehalose synthase complex as a free 59kDa protein. A 158 fold purification was achieved with over 84% recovery of active TPS. N-terminal sequence confirmed the 59kDa protein to be TPS. It was revealed to be a highly hydrophobic protein by amino acid analysis data. Activity of TPS was identified to be governed by association–dissociation of protein components. TPS activity of the isolated enzyme was highly unstable due to dissociation of the protein from the complex. Aggregation of active molecules was also seen to enhance as well as stabilize enzyme activity. This aggregation was concentration dependent and activity was seen to be enhanced by increasing the number of active molecules and fell with dilution. The association of the active complex was also found to be governed by ionic interactions.
Keywords: Trehalose-6-phosphate synthase; Enzyme aggregation; Association–dissociation; Saccharomyces cerevisiae;
Thermodynamics of the binding of cytotoxic protoberberine molecule coralyne to deoxyribonucleic acids by Kakali Bhadra; Motilal Maiti; Gopinatha Suresh Kumar (298-306).
The binding thermodynamics of the interaction of protoberberine molecule coralyne to various DNAs have been investigated. Thermodynamic data revealed that the binding was enthalpy driven in GC rich DNA and GC polynucleotides while the same was favored by both negative enthalpy and positive entropy changes in the AT rich DNA and AT polymers. Parsing the free energy change of the binding in terms of polyelectrolytic and nonpolyelectrolytic contribution showed the involvement of major contributions from the later. The heat capacity change (ΔC p°) for the binding of coralyne to calf thymus DNA and Micrococcus lysodeikticus DNA was − 147 and − 190cal/(mol K) respectively. The binding data in these systems also showed significant enthalpy–entropy compensation confirming the involvement of multiplicity of weak non-covalent interactions in agreement with the negative heat capacity data. Circular dichroic studies revealed that the binding was accompanied by moderate conformational change of B-form structure and more importantly the achiral alkaloid molecules acquired strong induced optical activity. These results contribute to the understanding of energetics of coralyne-DNA complexation that will guide synthetic efforts of medicinal chemists for developing better therapeutic agents.
Keywords: Coralyne; DNA; Thermodynamics; Melting studies;
Glycated human serum albumin enhances macrophage inflammatory protein-1β mRNA expression through protein kinase C-δ and NADPH oxidase in macrophage-like differentiated U937 cells by Koji Higai; Misaki Satake; Haruka Nishioka; Yutaro Azuma; Kojiro Matsumoto (307-314).
In a previous report (Higai K et al., Biol Pharm Bull, 2007), glycated human serum albumin (Glc-HSA) was found to induce interleukin-8 (IL-8) mRNA expression in human monocyte-derived U937 cells through a reactive oxygen species (ROS)-dependent pathway; however, Glc-HSA signaling has not been elucidated in macrophages.U937 cells were differentiated by treatment with 50 ng/mL phorbol 12-myristate 13-acetate (PMA) for 2 days and the macrophage-like differentiated U937 (differentiated U937) cells were stimulated with Glc-HSA and glycolaldehyde dimer-modified HSA (GA-HSA) in the presence of various signaling inhibitors. Macrophage inflammatory protein-1β (MIP-1β) mRNA expression was determined by real-time PCR. Intracellular ROS generation was estimated by confocal laser microscopy.Glc-HSA and GA-HSA markedly enhanced MIP-1β mRNA expression in differentiated U937 cells. Enhanced MIP-1β mRNA expression was completely suppressed by the ROS scavenger N-acetyl-l-cysteine, the NADPH oxidase inhibitors diphenylene iodonium and apocynin, and the protein kinase C (PKC)-δ inhibitor rottlerin. Furthermore, ROS generation was suppressed completely by rottlerin but not by the PKC-γ inhibitor Ro318425 or the PKC-α, -β1 and -μ inhibitor Go6976.Glc-HSA and GA-HSA enhance MIP-1β mRNA expression in differentiated U937 cells through PKC-δ-dependent activation of NADPH oxidase.
Keywords: Glycated albumin; MIP; NADPH oxidase; Protein kinase C; NFκB; AP-1;
Identification of a functional allene oxide synthase-lipoxygenase fusion protein in the soft coral Gersemia fruticosa suggests the generality of this pathway in octocorals by Helike Lõhelaid; Reet Järving; Karin Valmsen; Külliki Varvas; Malle Kreen; Ivar Järving; Nigulas Samel (315-321).
The conversion of fatty acid hydroperoxides to allene epoxides is catalysed by a cytochrome P450 in plants. In contrast, in the coral Plexaura homomalla, a catalase-related hemoprotein fused to the lipoxygenase (LOX) was found to function as an allene oxide synthase. This work reports the homology-based RT-PCR cloning and functional expression of a Gersemia fruticosa analogue of the allene oxide synthase-lipoxygenase (AOS-LOX) fusion protein. The G. fruticosa mRNA codes for a protein with 84% sequence identity to the P. homomalla AOS-LOX. Our data indicate that the AOS-LOX fusion protein pathway is used by another coral and P. homomalla represents no exception.
Keywords: Allene oxide synthase; AOS-LOX; Lipoxygenase-peroxidase fusion protein; Coral; Gersemia fruticosa; HETE; Lipoxygenase; LC-MS;