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The half-lives of platelet-derived growth factor A- and B-chain mRNAs are similar in endothelial cells and unaffected by heparin-binding growth factor-1 or cycloheximide.

Platelet-derived growth factor (PDGF) is mitogenic and chemotactic for vascular smooth muscle cells cultured in vitro, and, thus, may play a role in the smooth muscle cell proliferation and migration that occurs during atherosclerotic lesion development. Two related PDGF polypeptides, designated as the A and B chains, form functionally active PDGF-AA, AB, or BB dimers. The PDGF A- and B-chain genes are both transcribed in human umbilical vein endothelial (HUVE) cells and their expression is regulated by cytokines, growth factors, endotoxin, and phorbol ester. We reported previously that the angiogenic polypeptide heparin-binding growth factor (HBGF)-1 induces PDGF A-chain gene expression, but does not affect PDGF B-chain gene expression. In this study, we determined whether mRNA stabilization contributed to this induction by measuring the half-life of PDGF A-chain mRNA in quiescent, HBGF-1-stimulated, and proliferating HUVE cells. PDGF A-chain mRNA levels increase when quiescent HUVE cells are treated with the protein synthesis inhibitor cycloheximide; therefore, the effect of cycloheximide on PDGF A-chain mRNA decay was also investigated. The half-life of PDGF A-chain transcripts in quiescent cells was approximately 2.4 h and neither HBGF-1 nor cycloheximide significantly altered this decay rate. We also estimated the half-life of PDGF B-chain mRNA under the three different growth conditions and in the absence or presence of cycloheximide. The half-life in quiescent cells was approximately 1.8 h and was unaffected by HBGF-1 or protein synthesis inhibition. Therefore, the PDGF mRNAs have similar decay rates in HUVE cells, even though the 3' untranslated region of B-chain transcripts, but not A-chain transcripts, contains AU-rich sequence motifs postulated to confer rapid turnover in vivo.

Blotting, Northern↗

Combined effects of ionizing radiation and cycloheximide on gene expression.

We performed experiments to determine the effects of ionizing radiation exposure on expression of genes such as beta-actin, c-fos, histone H4, c-myc, c-jun, Rb, and p53 after exposure of Syrian hamster embryo (SHE) cells to the protein synthesis inhibitor cycloheximide. The purpose of these experiments was to determine the role of a labile protein in the radiation-induced response. The results revealed that when ionizing radiation (either fission-spectrum neutrons or gamma rays) was administered 15 min after cycloheximide treatment of SHE cells, the radiation exposure reduced cycloheximide-mediated gene induction of c-fos, histone H4, and c-jun. In addition, dose-rate differences were found when radiation exposure most significantly inhibited the cycloheximide response. Our results suggest that ionizing radiation does not act as a general protein-synthesis inhibitor and that the presence of a labile protein is required for the maintenance of specific gene transcription and mRNA accumulation after radiation exposure, especially at high dose-rates.

Actins↗

The effect of cycloheximide on Euglena gracilis phenylalanyl-tRNA synthetases.

The effect of cycloheximide on the chloroplastic, cytoplasmic and mitochondrial phenylalanyl-transfer RNA synthetases of Euglena gracilis was studied by growing both logarithmic and stationary phase cultures in the presence of the antibiotic. Enzyme activity was measured relative to untreated control cultures. At very low concentrations of cycloheximide (1 microgram/ml), all three log phase enzymes showed an increase in activity of 40-50%. At slightly higher concentrations (2.5 microgram/ml), the phenylalanyl-tRNA synthetase activities were comparable to those of the control cultures. At a cycloheximide concentration of 5 microgram/ml the enzyme activities from stationary phase cultures showed only very slight decreases (5-20%). The cytoplasmic and mitochondrial enzymes behaved similarly in log phase cultures at this concentration. However, the chloroplastic phenylalanyl-tRNA synthetase from log phase cultures treated with 5 microgram/ml cycloheximide showed a marked decrease in activity (70%). A further increase in antibiotic concentration to 10 microgram/ml resulted in significant losses of activity of all three enzymes, from both growth stages. The implications of the data with regard to identification of the site(s) of chloroplast enzyme synthesis are discussed.

Amino Acyl-tRNA Synthetases↗

Biochemical genetic studies of cycloheximide resistance in Neurospora crassa.

Genetic analysis of a number of cycloheximide-resistant mutants of Neurospora crassa has shown that resistance is controlled by several genes. Two of these appear to be located on linkage group V. Resistance to the antibiotic is dominant in wild-type-mutant heterokaryons. Two types of cycloheximide-resistant mutants were isolated: one type exhibited colonial morphology only when grown in the presence of cycloheximide and the other type maintained normal morphology even at high concentrations of the antibiotic. Reconstitution experiments with supernatant solutions and 80S monosomes prepared from wild-type and resistant mutant strains indicated that the property of cycloheximide resistance most likely is associated with the ribosomes. No electrophoretic or serological differences were found between the ribosomal proteins of the wild-type and resistant mutants.

Amino Acids↗

Cycloheximide mimics effects of oestradiol that are linked to synaptic plasticity of hypothalamic neurons.

The synaptic connectivity of the rat arcuate nucleus, a hypothalamic area rich in oestradiol receptors, is rapidly affected by physiological modifications of hormonal levels. A rise of oestradiol in plasma elicits a coordinated neuronal-glial response that begins with a rapid fall in the number of small (< 10 nm) intramembrane particles and a rapid increase in the number of large (> 10 nm) intramembrane particles in neuronal membranes, followed by a modification in the branching of astrocytic processes and finally results in decreased number of axo-somatic synapses and increased glial wrapping of the neuronal somas. In the course of a series of studies aimed to test possible non-genomic effects of oestradiol on neuronal membranes we analyzed the effect of the systemic administration of the protein synthesis inhibitor cycloheximide on the ultrastructure of arcuate neurons and granule cells of the cerebellar cortex, an area of the brain with low levels of estrogen receptors. Cycloheximide resulted in a significant inhibition of protein synthesis in hypothalmus and cerebellum of ovariectomized rats. Under these circumstances, the number of small intramembrane particles was reduced in hypothalamic and cerebellar neuronal membranes while the number of large intramembrane particles showed a decrease in cerebellar membranes and a transient increase in arcuate neuronal somas. Furthermore, cycloheximide resulted in an increased glial wrapping of arcuate neuronal somas but not of cerebellar granule cells. The ensheathing of arcuate neurons by glial was associated with a 41% decrease in the number of axo-somatic synapses. These results indicate that the protein synthesis inhibitor cycloheximide may elicit the integrated neuronal-glial response that is associated with the hormonally induced remodelling of synaptic contacts on arcuate neurons.

Animals↗

Cycloheximide treatment of cotton ovules alters the abundance of specific classes of mRNAs and generates novel ESTs for microarray expression profiling.

Fibres of cotton (Gossypium hirsutum L.) are single elongated epidermal cells that start to develop on the outer surface of cotton ovules on the day of anthesis. Little is known about the control of fibre initiation and development. As a first step towards discovering important genes involved in fibre initiation and development using a genomics approach, we report technical advances aimed at reducing redundancy and increasing coverage for anonymous cDNA microarrays in this study. Cotton ovule cDNA libraries (both normalised and un-normalised) from around the time of fibre initial formation have been prepared and partially characterised by sequencing. Re-association-based normalisation partially reduced library redundancy and increased representation of novel sequences. However, another library generated from in vitro cultured cotton ovules treated with the protein synthesis inhibitor, cycloheximide, showed a significantly altered gene representation including a greater proportion of protein phosphorylation genes, transport genes and transcription factors and a much reduced proportion of protein synthesis genes than were identified in the conventional types of libraries. Over 10,000 expressed sequence tag (EST) clones randomly selected from the three libraries were printed on microarray slides and used to assess gene expression in tissue cultured ovules with and without cycloheximide treatment. The microarray results showed that cycloheximide had a dramatic effect in modifying the pattern of the gene expression in cultured ovules, affecting the same types of genes identified in the preliminary analysis on relative EST abundance in the different ovule cDNA libraries. Cycloheximide clearly provided a simple and useful method for enriching novel gene sequences for genomic studies.

Base Sequence↗

Cycloheximide induces a subset of low temperature-inducible genes in maize.

To investigate further the signal transduction pathway that mediates the cold-stress response in maize, we isolated a low temperature-inducible cDNA clone (ZmCDPK1) that encodes a calcium-dependent protein kinase. Time-course experiments revealed that the low-temperature induction of ZmCDPK1 precedes that of mlip15, another cold-inducible gene that codes for a DNA-binding protein of the basic region/leucine zipper (bZIP) type, indicating that ZmCDPK1 might be located upstream of mlip15 in the cold-stress signal transduction pathway. We observed that the steady-state mRNA level of mlip15 drastically increased after cycloheximide treatment. In addition to mlip15, cycloheximide elevates the transcript levels of two other low temperature-induced genes, ZmCDPK1, and Adh1, which encodes alcohol dehydrogenase 1. In contrast, the chalcone synthase gene was only inducible by low temperature. The accumulation of the mlip15 transcript at low temperatures and in response to cycloheximide was significantly reduced by pretreatment with a calcium chelator, suggesting that calcium is involved in both cases of mlip15 induction. The signal transduction pathways triggered by low temperature and cycloheximide are discussed in relation to these observations.

Amino Acid Sequence↗

Differential effects of analogs of cycloheximide on protein and RNA synthesis in Achlya.

Analogs of the glutarimide antibiotic cycloheximide were tested for their effect on growth and incorporation of proline and uridine into acid-insoluble material in Achlya bisexualis. Each of the compounds tested had reduced antibiotic activity as compared to cycloheximide. The effects of the antibiotics on protein and RNA synthesis were varied. While cycloheximide inhibited both protein and RNA synthesis immediately, two of the analogs inhibited proline incorporation without effect on uridine incorporation, while three, each representing a modification of the hydroxyl of cycloheximide, stimulated uridine incorporation and either had no effect on or inhibited protein synthesis. These results indicate that the control of RNA synthesis by protein synthesis in Achlya can be released by glutarimide antibiotics.

Antifungal Agents↗

Evidence for cycloheximide acting as a glutamine analogue in plant tissue.

In growing maize root tissue [14C]asparagine formation in inhibited and [14C]glutamine accumulation stimulated by treatment with cycloheximide or glutamine analogs such as azaserine. In contrast, puromycin enhances the accumulation of [14C]asparagine but not [14C]glutamine. Cycloheximide and puromycin alone inhibit protein synthesis. This is interpreted to mean that the alteration in amide metabolism following cycloheximide treatment is a direct result of the antibiotic acting as a glutamine analog. While cycloheximide is often the cytoplasmic protein synthesis inhibitor of choice due to its potency and rapid action, its assumed specificity of action of eukaryotes is doubtful.

Asparagine↗

Cycloheximide effect on DNA degradation and delta-crystallin synthesis in terminally differentiating lens cells.

Low concentrations of a protein synthesis inhibitor, cycloheximide, were added throughout the process of in vitro differentiation of 11-day old embryonic chick lens cells. We found with low concentrations of cycloheximide (0.01 to 0.03 microgram/ml, 3 days of culture), that there was an almost complete delay of DNA degradation as observed on alkaline sucrose gradient. Identical concentrations and exposure time had no blocking effect on increased delta-crystallin synthesis as detected by immunoprecipitation and electrophoresis. Higher concentrations of cycloheximide (0.1 to 1 microgram/ml) showed a marked effect on DNA size and a net inhibition on delta-crystallin synthesis. Thus a selective effect of low doses of cycloheximide was observed on terminal differentiation suggesting that there was not a relationship between DNA degradation and delta-crystallin synthesis in these short term experiments. The investigations of minor proteins could be of interest as they may have a crucial role in intact nuclei cataracts.

Animals↗

cDNA cloning of mRNAS which increase rapidly in human lymphocytes cultured with concanavalin-A and cycloheximide.

To induce or "superexpress" genes involved in the entry of cultured GO lymphocytes into the G1-phase of the cell cycle, the cells were treated for 2 hours with a lectin (concanavalin-A) and a protein synthesis inhibitor (cycloheximide). A cDNA library was generated from small quantities of RNA by the high efficiency method of Gubler & Hoffman (1). 30,000 colonies were screened for differential hybridization to cDNA corresponding to treated cultures, but not to cDNA corresponding to control cultures. 50 recombinants were identified on this basis. One recombinant (#7) corresponded to mRNA (2150 base pairs) which was increased by cycloheximide alone, but was not increased by concanavalin A. Another recombinant (#19) corresponded to 2 mRNAs (980 and 1120 base pairs) one or both of which were increased either by concanavalin-A or by cycloheximide. It is speculated that the latter mRNAs are products of a locus which is activated when the concentration of a repressor is decreased by concanavalin-A or cycloheximide.

Cloning, Molecular↗

Effect of cycloheximide administered to rats in early postnatal life: prolonged inhibition of DNA synthesis in the developing brain.

Administration of cycloheximide in a single dose of 0.6 mg/kg to 7-day-old rats was used to induce short-term inhibition of protein synthesis at the period of brain 'growth spurt'. Measurement of the rate of [14C]lysine incorporation indicated that the initial inhibition of protein synthesis in the brain (by 75%) was released within about 12 h. The normal rate of protein synthesis was attained by 48 h after cycloheximide administration; there was no sign of protein synthesis stimulation. The estimation of [14C]thymidine incorporation into brain DNA showed that inhibition of DNA synthesis was greater and longer lasting in the forebrain and olfactory bulbs (by about 80%) than in the cerebellum (by about 40%). Similar differential inhibition of thymidine kinase activity was observed in the olfactory bulbs (by 75%) and cerebellum (by 30%) at 24 h after cycloheximide, suggesting that the formation of [14C]thymidine nucleotides may have been impaired. However, a retardation of DNA accumulation was found in the forebrain and cerebellum at 72 h after cycloheximide. Thus, the short-term inhibition of protein synthesis produced prolonged inhibition of DNA synthesis and altered cell proliferation in the developing brain.

Animals↗

On the interaction between nicotine and cycloheximide.

This study examined whether the nicotine-induced reversal of the amnestic effect of cycloheximide is due to an interaction between nicotine and cycloheximide on brain protein synthesis, and whether it involves the sites in brain that saturably bind [3H]nicotine. Nicotine did not reverse the cycloheximide-induced inhibition of protein synthesis, both in in vivo (intact animal) and in vitro (brain slice), suggesting that on-going protein synthesis is not necessarily involved in memory consolidation. The nicotine binding sites were not affected by in vivo or in vitro treatment with cycloheximide in the presence or absence of nicotine.

Animals↗

Phase shifting the circadian clock with cycloheximide: response of hamsters with an intact or a split rhythm of locomotor activity.

Systemic administration of the protein synthesis inhibitor, cycloheximide, induced both phase advances and phase delays in the circadian rhythm of wheel-running activity in hamsters (Mesocricetus auratus) maintained in constant darkness or constant light. The magnitude and direction of the phase shifts were dependent on the circadian time (CT) of drug treatment. The phase response curves in constant darkness and constant light were of similar general shape, but they differed in the overall mean amplitude of the phase shifts. Maximal phase advances were observed after injections around CT 6-8, maximal delays at CT 0-2. Injections of various doses of cycloheximide at CT 0 induced a dose-dependent phase delay in the rhythm with a maximum delay induced by 10 mg cycloheximide. Injections of cycloheximide in animals with a split activity rhythm caused phase shifts of both components in the same direction (20/39) and in different directions (10/39). The results support the hypothesis that 80S ribosomal protein synthesis plays an important role in the biochemical mechanisms of circadian systems.

Animals↗

Effects of cycloheximide on delayed neuronal death in rat hippocampus.

The effect of cycloheximide, a protein synthesis inhibitor, on hippocampal selective neuronal death was morphologically studied in rats subjected to 10 min forebrain ischemia using a 4-vessel occlusion model. Neuronal damage in the hippocampal CA1 subfield 72 h after ischemic insult was dramatically decreased by the lasting inhibition of protein synthesis through consecutive administration of cycloheximide. Cycloheximide, which was administered once within the first 24 h of recirculation, showed protective action on ischemic cell necrosis and its most potent effect was observed when injected at 12 h of post-ischemia. After 36 h of recirculation, however, treatment with cycloheximide could no longer prevent cell death. The possibility is considered that hippocampal delayed neuronal death following transient ischemia is caused by abnormal protein(s).

Animals↗

Attachment of ribosomes to endoplasmic membranes in mouse pancreas. Degranulation in vivo caused by the inducers of autophagocytosis neutral red, vinblastine, puromycin, and cadmium ions, and prevention by cycloheximide.

The present investigation was undertaken to discover whether in vivo inducers of autophagocytosis such as neutral red (0.40 mg/g body weight), cadmium chloride (0.15 mg/animal), vinblastine sulfate (7.5 mg/kg b.w.), and puromycin dihydrochloride (0.20 mg/g b.w.) are able to produce degranulation of rough surfaced endoplasmic reticulum (ER) of pancreatic acinar cells as we suggested earlier. Using a modified method of Blobel and Potter about 30% of the total ribosomes of untreated control pancreas were recovered in the free form, and 70% in the membrane-bound form. Cycloheximide (0.20 mg/g body weight) had no effect on this distribution of ribosomes, while neutral red, cadmium ions, vinblastine, and puromycin led to the presence of more free ribosomes: thus up to 70% of the total cytoplasmic ribosomes were recovered in the free form 30 to 60 min after treatments with the autophagic inducers. Pretreatments with cycloheximide prevented this shift and the distribution of ribosomes remained normal. On the basis of these and previous results we conclude that in pancreas an initial degranulation of the ER caused by these agents is a precondition of membrane transformation in autophagocytosis which is preventable by cycloheximide. Confirming the ultrastructural data of Longnecker et al. on rat pancreas, puromycin was shown to cause different forms of cellular injury including autophagocytosis. All forms of cellular injury were also prevented by pretreatment with cycloheximide in mouse pancreas.

Animals↗

Aging-related changes and topology of adhesion responses sensitive to cycloheximide on collagen substrata by human dermal fibroblasts.

Human dermal fibroblasts (both papillary and reticular) were tested during in vivo or in vitro aging for their responses on collagen and/or fibronectin (FN) substrata, as well as on topologically mixed substrata. Cycloheximide treatments were used to evaluate whether receptors to these matrix molecules, mediating F-actin reorganization into stress fibers, are altered during aging processes. Late-passage (but not mid-passage) papillary and reticular cells from both an elderly male and a newborn infant spread effectively on collagen +/- FN but failed to generate stress fibers after lengthy pretreatment of cells with cycloheximide. In contrast, treatment with cycloheximide only when cells were reattaching was not inhibitory. None of the treatments had any effect on stress fiber formation of cells on FN-only substrata, demonstrating that drug sensitivity was specific for collagen responses. The inhibition could be reversed by rinsing cycloheximide out of cultures and could be prevented by prior growth of cells in ascorbate-supplemented medium to stimulate production/maturation of collagen and possibly collagen-specific receptors. Adjacent regions of coverslips were adsorbed with collagen and a proteolytic fragment of plasma FN lacking the collagen-binding domain but retaining other binding domains; cells bridging the interface were of special interest. When fragment F155 containing both the RGDS cell-binding and the heparin II-binding domains was tested in this paradigm, cells generated stress fibers continuous from the collagen-facing side into the F155-facing side of the same cell, consistent with the compatability of both collagen and FN receptors in generating the same stress fiber. However, F110 lacking the heparin II domain was incapable of facilitating stress fiber formation; fibers formed effectively on the collagen side and terminated abruptly at the collagen:F110 interface. These experiments demonstrate stringent regulation of where stress fibers begin, span, and terminate in the cytoplasm by matrix receptors at the cell's undersurface and establish that there are alterations of collagen-specific receptors as a consequence of in vitro aging, but not of in vivo aging, in both papillary and reticular human dermal fibroblasts.

Aging↗

Cycloheximide inhibits cellular, but not SV40, DNA replication.

We have prepared extracts from cycloheximide-treated cells for the study of simian-virus-40 (SV40)-DNA replication in vitro. When supplemented with the viral initiator protein (large T antigen), these extracts fully supported SV40-DNA replication. We also determined that SV40-DNA replication in vivo is much more resistant to cycloheximide than cellular DNA replication. SV40 encodes its own initiator protein, T antigen, which also functions as a DNA helicase, but depends on cellular functions for all additional replication reactions. Therefore, it appears to be quite likely that cycloheximide affects cellular DNA replication by blocking the synthesis of (a) cellular function(s) that is(are) performed by T antigen in SV40-DNA replication. Indeed, DNA fiber autoradiography and alkaline sucrose gradient centrifugation of pulse-labeled cellular DNA showed that cycloheximide treatment almost completely suppressed replicon initiation and reduced the rate of replication fork movement to about one third of the control.

Antigens, Polyomavirus Transforming↗