Effect of Cerophyl growth medium on exocytosis in Tetrahymena thermophila

1985 ◽  
Vol 78 (1) ◽  
pp. 23-48
Author(s):  
D.M. Pesciotta ◽  
B.H. Satir
Keyword(s):  
Cell Division ◽  
De Novo ◽  
Tetrahymena Thermophila ◽  
Freeze Fracture ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Particle Array ◽  
Proteose Peptone ◽  
Section Electron ◽  
Cell Changes

Culturing the ciliate Tetrahymena thermophila in Cerophyl has provided an opportunity for studying the assembly and/or synthesis of the intramembrane particle array, the rosette, which marks the site of exocytosis in these cells. Cultures grown in this medium cease cell division after only 12h and enter ‘stationary phase’ earlier (12h of growth) relative to growth in standard medium (proteose peptone). In addition, the cell changes from the normally observed pear-shaped body to a thinner more ellipsoid form. Despite the initial similarities to starving cells, several differences are observed in the Cerophyl-grown cells. One is that cell size remains constant for at least 72h in contrast to starved cells. Secondly, in spite of this block in cell division, results from freeze-fracture replicas of the cell membrane of these cells show that they continue to assemble rosettes, the number of which increases approximately six times, from 0.34 rosette/microgram2 to 2.1 rosettes/microgram2. Addition of the protein synthesis inhibitor, cycloheximide (6h exposure), during growth in Cerophyl shows that 70% of rosettes can be assembled, despite the blockage of translation, by using pre-existing component(s) from a pool. The remaining 30% must involve de novo synthesis of one or more components; this percentage can be increased with longer exposure to the drug. Thirdly, an apparent increase in the number of mucocysts is observed by thin-section electron microscopy. At first (12–24h) only docked mucocysts seem to accumulate in the cell. However, by 36h a considerable increase seems to have taken place, particularly in the number of mucocysts located in the cytoplasm. In the cycloheximide-treated cells this increase in mucocysts begins to be blocked after 6h of exposure to the drug. These observations are in agreement with the results obtained from the freeze-fracture data on the concomitant increase in number of rosettes. This system therefore offers the first possibility of exploring the biosynthesis of these components.

Determinants of kinin release in isolated rat hindquarters

1998 ◽  
Vol 274 (1) ◽  
pp. R120-R125 ◽  
Author(s):  
Tohru Sakakibara ◽  
Thomas H. Hintze ◽  
Alberto Nasjletti
Keyword(s):  
Protein Synthesis ◽  
Trypsin Inhibitor ◽  
De Novo ◽  
Soybean Trypsin Inhibitor ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Bicarbonate Buffer ◽  
Kallikrein Inhibitor ◽  
Isolated Rat

We studied the determinants of kinin release into the venous effluent of rat hindquarters perfused with Krebs bicarbonate buffer. Kinin release in preparations perfused with control media (14.6 ± 2.5–20.7 ± 6.7 pg/15 min) was surpassed by that in preparations perfused with media containing kininase inhibitors (243 ± 53 to 276 ± 78 pg/15 min). Kinin release increased when purified kininogen (from 242 ± 43 to 3,365 ± 725 pg/15 min) or kallikrein (from 270 ± 49 to 30,649 ± 8,040 pg/15 min) was added to the perfusate. Conversely, kinin release fell when the kallikrein inhibitor aprotinin (from 272 ± 58 to 122 ± 27 pg/15 min) or soybean trypsin inhibitor (from 273 ± 52 to 195 ± 25 pg/15 min) was added. Both basal and kininogen-induced kinin release were attenuated in preparations perfused with media containing cycloheximide, a protein synthesis inhibitor, but kallikrein-induced kinin release was not. These data suggest that kinin release from perfused rat hindquarters reflects the activity of both the kinin-degrading and kinin-generating pathways and that the latter is sustained by a kallikrein manufactured de novo and by preexistent kininogen(s).

scholarly journals ON THE MECHANISM OF ADAPTATION TO PROTEIN SYNTHESIS INHIBITORS BY TETRAHYMENA

1974 ◽  
Vol 62 (3) ◽  
pp. 707-716 ◽  
Author(s):  
Charles T. Roberts ◽  
Eduardo Orias
Keyword(s):  
Protein Synthesis ◽  
Cell Division ◽  
Protein Synthesis Inhibitor ◽  
Protein Synthesis Inhibitors ◽  
Cellular Functions ◽  
Synthesis Inhibitor ◽  
Experimental Conditions ◽  
Cellular Machinery ◽  
Time Required ◽  
Sublethal Concentrations

Tetrahymena is able to adapt to the presence of sublethal concentrations of many drugs which inhibit a wide variety of cellular functions. In spite of the generality of this phenomenon in Tetrahymena, the mechanism of adaptation at the cellular and molecular levels is unknown. This study deals mainly with adaptation to the protein synthesis inhibitors, cycloheximide and emetine. The physiological response of Tetrahymena to sublethal concentrations of these drugs is an immediate cessation of cell division for a period of time dependent on the drug concentration, followed by an abrupt resumption of exponential growth at a constant rate. By measuring the length of the growth lags under a variety of experimental conditions, we have confirmed several observations made by Frankel and coworkers, and provide evidence for two new phenomena associated with adaptation to cycloheximide: (a) adaptation to cycloheximide also results in adaptation of cells to emetine, another protein synthesis inhibitor not closely related structurally to cycloheximide. We have termed this phenomenon cross adaptation, (b) exposure to concentrations of cycloheximide too low to cause any growth lags or inhibition of protein synthesis significantly shortens the time required by cells to adapt to higher concentrations of cycloheximide. We have termed this phenomenon facilitation. Facilitation shows some degree of specificity in that facilitation with cycloheximide has no effect on adaptation to emetine. From this, we infer the existence of two distinct systems involved in adaptation to cycloheximide, one of which shows a higher degree of specificity towards cycloheximide than the other. We also show that transfer of adapted or facilitated cells to drug-free medium results in a gradual but complete resensitization. The kinetics of resensitization suggest that the cellular machinery responsible for adaptation and facilitation does not leave the cell, but is simply diluted out during cell division.

scholarly journals Natural and environmental oestrogens induce TGFB1 synthesis in oviduct cells

Reproduction ◽  
2018 ◽  
Vol 155 (3) ◽  
pp. 233-244 ◽  
Author(s):  
Barbara P S Cometti ◽  
Raghvendra K Dubey ◽  
Bruno Imthurn ◽  
Marinella Rosselli
Keyword(s):  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
De Novo ◽  
Embryo Implantation ◽  
Early Embryo ◽  
Biochanin A ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Paracrine Factors ◽  
Aryl Hydrocarbon

Autocrine/paracrine factors generated in response to 17β-oestradiol (E2), within the oviduct, facilitate early embryo development for implantation. Since transforming growth factor beta 1 (TGFB1) plays a key role in embryo implantation, regulation of its synthesis by E2 may be of biological/pathophysiological relevance. Here, we investigated whether oviduct cells synthesize TGFB1 and whether E2 and environmental oestrogens (EOEs; xenoestrogens and phytoestrogens) modulate its synthesis. Under basal conditions, bovine oviduct cells (OCs; oviduct epithelial cells and oviduct fibroblasts; 1:1 ratio) synthesized TGFB1. E2 concentration-dependent induced TGFB1 levels in OCs and these effects were mimicked by some, but not all EOEs (genistein, biochanin A and 4-hydroxy-2′,4′,6′-trichlorobiphenyl, 4-hydroxy-2′,4′,6′-dichlorobiphenyl); moreover, EOEs enhanced (P < 0.05) the stimulatory effects of E2 on TGFB1 synthesis. The OCs expressed oestrogen receptors alpha and beta and aryl hydrocarbon; moreover, co-treatment with ER antagonist ICI182780 blocked the stimulatory effects of E2 and EOEs on TGFB1 synthesis. Treatment with non-permeable E2-BSA failed to induce TGFB1, thereby ruling out the involvement of membrane ERs. Cycloheximide (protein synthesis inhibitor) blocked E2-induced TGFB1 synthesis providing evidence forde novosynthesis. The stimulatory effects of E2 and EOEs, were inhibited (P < 0.05) by MAPK inhibitor (PD98059), whereas intracellular-Ca2+chelator (BAPTA-AM) and adenylyl cyclase inhibitor (SQ22536) abrogated the effects of E2, but not EOEs, suggesting that post-ER effects of E2 and EOEs involve different pathways. Our results provide the first evidence that in OCs, E2 and EOEs stimulate TGFB1 synthesis via an ER-dependent pathway. Exposure of the oviduct to EOEs may result in continuous/sustained induction of TGFB1 levels in a non-cyclic fashion and may induce deleterious effects on reproduction.

scholarly journals Social Fear Memory Requires Two Stages of Protein Synthesis in Mice

2020 ◽  
Vol 21 (15) ◽  
pp. 5537
Author(s):  
Johannes Kornhuber ◽  
Iulia Zoicas
Keyword(s):  
Protein Synthesis ◽  
Temporal Dynamics ◽  
De Novo ◽  
Fear Memory ◽  
Protein Synthesis Inhibitor ◽  
Dependent Manner ◽  
Synthesis Inhibitor ◽  
Systemic Injection ◽  
Social Fear ◽  
Two Stages

It is well known that long-term consolidation of newly acquired information, including information related to social fear, require de novo protein synthesis. However, the temporal dynamics of protein synthesis during the consolidation of social fear memories is unclear. To address this question, mice received a single systemic injection with the protein synthesis inhibitor, anisomycin, at different time-points before or after social fear conditioning (SFC), and memory was assessed 24 h later. We showed that anisomycin impaired the consolidation of social fear memories in a time-point-dependent manner. Mice that received anisomycin 20 min before, immediately after, 6 h, or 8 h after SFC showed reduced expression of social fear, indicating impaired social fear memory, whereas anisomycin caused no effects when administered 4 h after SFC. These results suggest that consolidation of social fear memories requires two stages of protein synthesis: (1) an initial stage starting during or immediately after SFC, and (2) a second stage starting around 6 h after SFC and lasting for at least 5 h.

scholarly journals Signal transduction for chemotaxis and haptotaxis by matrix molecules in tumor cells.

1990 ◽  
Vol 110 (4) ◽  
pp. 1427-1438 ◽  
Author(s):  
S Aznavoorian ◽  
M L Stracke ◽  
H Krutzsch ◽  
E Schiffmann ◽  
L A Liotta
Keyword(s):  
Protein Synthesis ◽  
Matrix Protein ◽  
Type Iv Collagen ◽  
De Novo ◽  
Protein Synthesis Inhibitor ◽  
Dependent Manner ◽  
Recognition Sequence ◽  
Synthesis Inhibitor ◽  
Concentration Dependent Manner ◽  
Type Iv

Transduction of signals initiating motility by extracellular matrix (ECM) molecules differed depending on the type of matrix molecule and whether the ligand was in solution or bound to a substratum. Laminin, fibronectin, and type IV collagen stimulated both chemotaxis and haptotaxis of the A2058 human melanoma cell line. Peak chemotactic responses were reached at 50-200 nM for laminin, 50-100 nM for fibronectin, and 200-370 nM for type IV collagen. Checkerboard analysis of each attractant in solution demonstrated a predominantly directional (chemotactic) response, with a minor chemokinetic component. The cells also migrated in a concentration-dependent manner to insoluble step gradients of substratum-bound attractant (haptotaxis). The haptotactic responses reached maximal levels at coating concentrations of 20 nM for laminin and type IV collagen, and from 30 to 45 nM for fibronectin. Pretreatment of cells with the protein synthesis inhibitor, cycloheximide (5 micrograms/ml), resulted in a 5-30% inhibition of both chemotactic and haptotactic responses to each matrix protein, indicating that de novo protein synthesis was not required for a significant motility response. Pretreatment of cells with 50-500 micrograms/ml of synthetic peptides containing the fibronectin cell-recognition sequence GRGDS resulted in a concentration-dependent inhibition of fibronectin-mediated chemotaxis and haptotaxis (70-80% inhibition compared to control motility); negative control peptide GRGES had only a minimal effect. Neither GRGDS nor GRGES significantly inhibited motility to laminin or type IV collagen. Therefore, these results support a role for the RGD-directed integrin receptor in both types of motility response to fibronectin. After pretreatment with pertussis toxin (PT), chemotactic responses to laminin, fibronectin, and type IV collagen were distinctly different. Chemotaxis to laminin was intermediate in sensitivity; chemotaxis to fibronectin was completely insensitive; and chemotaxis to type IV collagen was profoundly inhibited by PT. In marked contrast to the inhibition of chemotaxis, the hepatotactic responses to all three ligands were unaffected by any of the tested concentrations of PT. High concentrations of cholera toxin (CT; 10 micrograms/ml) or the cAMP analogue, 8-Br-cAMP (0.5 mM), did not significantly affect chemotactic or haptotactic motility to any of the attractant proteins, ruling out the involvement of cAMP in the biochemical pathway initiating motility in these cells. The sensitivity of chemotaxis induced by laminin and type IV collagen, but not fibronectin, to PT indicates the involvement of a PT-sensitive G protein in transduction of the signals initiating motility to soluble laminin and type IV collagen.(ABSTRACT TRUNCATED AT 400 WORDS)

TISSUE PLASMINOGEN ACTIVATOR (T-PA) PRODUCTION BY HUMAN EMBRYONIC FIBROBLASTS, IMR-90, STIMULATED BY PROTEOSE PEPTONE

1987 ◽  
Author(s):  
Y Itagaki ◽  
A Suzuki ◽  
K Higashio
Keyword(s):  
Arachidonic Acid ◽  
Fatty Acid ◽  
Phospholipase A2 ◽  
Plasminogen Activator ◽  
Unsaturated Fatty Acid ◽  
De Novo ◽  
Calf Serum ◽  
Synthesis Inhibitor ◽  
Proteose Peptone ◽  
Fibrin Plate

In order to study the mechanisms by which t-PA production by IMR-90 cells are induced, lactalbumin hydrolysates, yeast extracts, and peptones were tested for their ability to induce t-PA production by IMR-90 cells. IMR-90 cells were grown to confluency in Dulbecco's modified Eagle's medium(DMEM) supplemented with 10% fetal calf serum at 37°C in 5% CO2 in air. And the cells were maintained in serum free medium containing 1% of each additive. The plasminogen activator activity was determined by fibrin plate method, using urokinase or t-PA from WHO as a standard. It was found that proteose peptone (Difco) and neopeptone (Difco) strongly induced the t-PA production by IMR-90 cells. The t-PA production in DMEM containing 1% proteose peptone reached approx. 200IU/ml after incubation at 37°C for 6 days and was from twenty to fifty times higher than that in DMEM only (control medium). The t-PA production by IMR-90 cells stimulated by proteose peptone was strongly inhibited by RNA synthesis inhibitor(actinomycin D) or prorein synthesis inhibitor (cycloheximide). Hence, t-PA production by IMR-90 cells stimulated by proteose peptone was mediated by de novo synthesis. Chelating reagent (EGTA), Ca2+ entry blocker (verapamil), inhibitor of phospholipase A2 (quinacrine) and inhibitor of lipoxygenase (NDGA) strongly inhibited the t-PA production by IMR-90 cells stimulated by proteose peptone. Inhibitor of cyclooxygenase (indomethacin) was inert. On the contrary, activators of phospholipase A2(Ca2+,melittin) and hydroxy-unsaturated fatty acid (5-HETE) derived from arachidonic acid by lipoxygenase strongly enhanced t-PA production by IMR-90 cells stimulated by proteose peptone. These results suggest that the t-PA production by IMR-90 cells stimulated by proteose peptone is mediated by arachidonate cascade involving the following pathway; (1) proteose peptone stimulates the membrane of IMR-90, (2) this stimulus causes Ca2+ influx, (3) Ca2+ ion activates phopholipase A2, (4) activated phospholipase A2 liberates arachidonic acid from phospholipids in ceil membrane and (5) lipoxygenase converts arachidonic acid into the hydroxy-unsaturated fatty acid.

scholarly journals Granulocyte/macrophage colony-stimulating factor stimulates the expression of the 5-lipoxygenase-activating protein (FLAP) in human neutrophils.

1994 ◽  
Vol 179 (4) ◽  
pp. 1225-1232 ◽  
Author(s):  
M Pouliot ◽  
P P McDonald ◽  
P Borgeat ◽  
S R McColl
Keyword(s):  
De Novo ◽  
Human Neutrophils ◽  
Protein Synthesis Inhibitor ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Synthesis Inhibitor ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

The synthesis of leukotrienes in human blood neutrophils chiefly relies on the activity of two enzymes, phospholipase A2 and 5-lipoxygenase (5-LO). In turn, the activation of the 5-LO requires the participation of a recently characterized membrane-bound protein, the 5-LO-activating protein (FLAP). In this study, we have investigated conditions under which FLAP expression in neutrophils may be modulated. Of several cytokines tested, only granulocyte/macrophage colony-stimulating factor (GM-CSF) (and to a lesser extent tumor necrosis factor alpha) significantly increased expression of FLAP. GM-CSF increased FLAP mRNA steady-state levels in a time- and dose-dependent manner. The stimulatory effect of GM-CSF on FLAP mRNA was inhibited by prior treatment of the cells with the transcription inhibitor, actinomycin D, and pretreatment of the cells with the protein synthesis inhibitor, cycloheximide, failed to prevent the increase in FLAP mRNA induced by GM-CSF. The accumulation of newly synthesized FLAP, as determined by immunoprecipitation after incorporation of 35S-labeled amino acids, was also increased after incubation of neutrophils with GM-CSF. In addition, the total level of FLAP protein was increased in GM-CSF-treated neutrophils, as determined by two-dimensional gel electrophoresis, followed by Western blot. GM-CSF did not alter the stability of the FLAP protein, indicating that the effect of GM-CSF on FLAP accumulation was the consequence of increased de novo synthesis as opposed to decreased degradation of FLAP. Finally, incubation of neutrophils with the synthetic glucocorticoid dexamethasone directly stimulated the upregulation of FLAP mRNA and protein, and enhanced the effect of GM-CSF. Taken together, these data demonstrate that FLAP expression may be upmodulated after appropriate stimulation of neutrophils. The increase in FLAP expression induced by GM-CSF in inflammatory conditions could confer upon neutrophils a prolonged capacity to synthesize leukotrienes.

scholarly journals Removal of peptidoglycan and inhibition of active cellular processes leads to daptomycin tolerance in Enterococcus faecalis

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254796
Author(s):  
Rachel D. Johnston ◽  
Brittni M. Woodall ◽  
Johnathan Harrison ◽  
Shawn R. Campagna ◽  
Elizabeth M. Fozo
Keyword(s):  
Enterococcus Faecalis ◽  
Fatty Acid Biosynthesis ◽  
De Novo ◽  
Intact Cell ◽  
Growth Conditions ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Cellular Processes ◽  
Peptidoglycan Synthesis ◽  
Cyclic Lipopeptide

Daptomycin is a cyclic lipopeptide antibiotic used in the clinic for treatment of severe enterococcal infections. Recent reports indicate that daptomycin targets active cellular processes, specifically, peptidoglycan biosynthesis. Within, we examined the efficacy of daptomycin against Enterococcus faecalis under a range of environmental growth conditions including inhibitors that target active cellular processes. Daptomycin was far less effective against cells in late stationary phase compared to cells in exponential phase, and this was independent of cellular ATP levels. Further, the addition of either the de novo protein synthesis inhibitor chloramphenicol or the fatty acid biosynthesis inhibitor cerulenin induced survival against daptomycin far better than controls. Alterations in metabolites associated with peptidoglycan synthesis correlated with protection against daptomycin. This was further supported as removal of peptidoglycan induced physiological daptomycin tolerance, a synergistic relation between daptomycin and fosfomycin, an inhibitor of the fist committed step peptidoglycan synthesis, was observed, as well as an additive effect when daptomycin was combined with ampicillin, which targets crosslinking of peptidoglycan strands. Removal of the peptidoglycan of Enterococcus faecium, Staphylococcus aureus, and Bacillus subtilis also resulted in significant protection against daptomycin in comparison to whole cells with intact cell walls. Based on these observations, we conclude that bacterial growth phase and metabolic activity, as well as the presence/absence of peptidoglycan are major contributors to the efficacy of daptomycin.

scholarly journals Isolation and ultrastructural characterization of secretory mutants of Tetrahymena thermophila

1983 ◽  
Vol 64 (1) ◽  
pp. 49-67 ◽  
Author(s):  
E. Orias ◽  
M. Flacks ◽  
B.H. Satir
Keyword(s):  
Electron Microscopy ◽  
Tetrahymena Thermophila ◽  
Freeze Fracture ◽  
Regulatory Mechanisms ◽  
Genetic Dissection ◽  
Intramembrane Particle ◽  
Particle Array ◽  
Normal Number ◽  
Ultrastructural Characterization

Isolation of 14-secretory mutants (exo-) of Tetrahymena thermophila and ultrastructural characterization (freeze-fracture and thin-section) of two of these (SB255 and SB258) are described. The site of secretion is marked by an intramembrane particle array, the rosette, beneath which the secretory organelle rests. Using Alcian Blue (8GS) as a secretagogue, a screening procedure for exo- cells was developed. Of the resulting 14 clones isolated, 10 are stable and have a tight mutant phenotype. Two of these, SB255 and SB258, lack assembled rosettes. Electron microscopy shows that SB255 has a reduced total number of mucocysts, whereas SB258 appears to have the normal number. This study demonstrates a useful eukaryotic model with which to study by genetic dissection the regulatory mechanisms involved in membrane events in secretion.

scholarly journals Oxidative and Electrophilic Stresses Activate Nrf2 through Inhibition of Ubiquitination Activity of Keap1

2006 ◽  
Vol 26 (1) ◽  
pp. 221-229 ◽  
Author(s):  
Akira Kobayashi ◽  
Moon-Il Kang ◽  
Yoriko Watai ◽  
Kit I. Tong ◽  
Takahiro Shibata ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
De Novo ◽  
Degradation Mechanism ◽  
Nuclear Accumulation ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Nrf2 Activation ◽  
Nrf2 Protein

ABSTRACT The Keap1-Nrf2 system is the major regulatory pathway of cytoprotective gene expression against oxidative and/or electrophilic stresses. Keap1 acts as a stress sensor protein in this system. While Keap1 constitutively suppresses Nrf2 activity under unstressed conditions, oxidants or electrophiles provoke the repression of Keap1 activity, inducing the Nrf2 activation. However, the precise molecular mechanisms behind the liberation of Nrf2 from Keap1 repression in the presence of stress remain to be elucidated. We hypothesized that oxidative and electrophilic stresses induce the nuclear accumulation of Nrf2 by affecting the Keap1-mediated rapid turnover of Nrf2, since such accumulation was diminished by the protein synthesis inhibitor cycloheximide. While both the Cys273 and Cys288 residues of Keap1 are required for suppressing Nrf2 nuclear accumulation, treatment of cells with electrophiles or mutation of these cysteine residues to alanine did not affect the association of Keap1 with Nrf2 either in vivo or in vitro. Rather, these treatments impaired the Keap1-mediated proteasomal degradation of Nrf2. These results support the contention that Nrf2 protein synthesized de novo after exposure to stress accumulates in the nucleus by bypassing the Keap1 gate and that the sensory mechanism of oxidative and electrophilic stresses is closely linked to the degradation mechanism of Nrf2.

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