Investigation of the mechanism of action of a potent pateamine A analog, des-methyl, des-amino pateamine A (DMDAPatA)

2020 ◽  
Vol 98 (4) ◽  
pp. 502-510
Author(s):  
Sai Shilpa Kommaraju ◽  
Julieta Aulicino ◽  
Shruthi Gobbooru ◽  
Jing Li ◽  
Mingzhao Zhu ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Inhibitory Effect ◽  
Initiation Factor ◽  
Cellular Activity ◽  
Proliferating Cells ◽  
Eif4f Complex ◽  
Antiproliferative Agent ◽  
Pateamine A ◽  
The Impact

The natural product pateamineA (PatA) is a highly potent antiproliferative agent. PatA and the simplified analog desmethyl, desamino pateamineA (DMDAPatA) have exhibited cytotoxicity selective for rapidly proliferating cells, and have been shown to inhibit cap-dependent translation initiation through binding to eIF4A (eukaryotic initiation factor 4A) of the eIF4F complex. PatA and DMDAPatA are both known to stimulate the RNA-dependent ATPase, and ATP-dependent RNA helicase activities of eIF4A. The impact of other eIF4F components, eIF4E and eIF4G, on DMDAPatA action were investigated in vitro and in cultured mammalian cells. The perturbation of the eIF4A–eIF4G association was found to be eIF4E- and mRNA cap-dependent. An inhibitory effect on helicase activity of eIF4A was observed when it was part of a complex that mimicked the eIF4F complex. We propose a model of action for DMDAPatA (and by supposition PatA) where the cellular activity of the compound is dependent on an “active” eIF4F complex.

The Cellular Target Specificity of Pateamine A

2013 ◽  
Vol 68 (9-10) ◽  
pp. 406-415 ◽  
Author(s):  
James H. Matthews ◽  
David R. Maass ◽  
Peter T. Northcote ◽  
Paul H. Atkinson ◽  
Paul H. Teesdale-Spittle
Keyword(s):  
Biologically Active ◽  
Initiation Factor ◽  
Cellular Activity ◽  
Eukaryotic Initiation Factor ◽  
Cellular Target ◽  
Wide Range ◽  
Dividing Cells ◽  
Pateamine A ◽  
Mycale Hentscheli

The natural product pateamine A (pateamine) from the sponge Mycale hentscheli is active against a wide range of dividing cells and has been shown to inhibit the functions of the eukaryotic initiation factor 4A (eIF4A). We have identifi ed that pateamine is additionally able to modulate the formation of actin fi laments and microtubules in vitro but at higher concentrations than required for inhibition of eIF4A. Cell cycle analysis confi rmed that actin and tubulin are not major mediators of the cellular activity of pateamine. The range of targets identifi ed demonstrates the value of multiple approaches to determining the mode of action of biologically active compounds

scholarly journals Heavy Water Reduces GFP Expression in Prokaryotic Cell-Free Assays at the Translation Level While Stimulating Its Transcription

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Luisa S. Hohlefelder ◽  
Tobias Stögbauer ◽  
Madeleine Opitz ◽  
Thomas M. Bayerl ◽  
Joachim O. Rädler
Keyword(s):  
Gene Expression ◽  
Heavy Water ◽  
Expression System ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Gfp Expression ◽  
Antiproliferative Agent ◽  
Underlying Mechanisms ◽  
The Impact

Thein vitroproliferation of prokaryotic and eukaryotic cells is remarkably hampered in the presence of heavy water (D2O). Impairment of gene expression at the transcription or translation level can be the base for this effect. However, insights into the underlying mechanisms are lacking. Here, we employ a cell-free expression system for the quantitative analysis of the effect of increasing percentages of D2O on the kinetics ofin-vitroGFP expression. Experiments are designed to discriminate the rates of transcription, translation, and protein folding using pDNA and mRNA vectors, respectively. We find that D2O significantly stimulates GFP expression at the transcription level but acts as a suppressor at translation and maturation (folding) in a linear dose-dependent manner. At a D2O concentration of 60%, the GFP expression rate was reduced to 40% of an undisturbed sample. We observed a similar inhibition of GFP expression by D2O in a recombinantEscherichia colistrain, although the inhibitory effect is less pronounced. These results demonstrate the suitability of cell-free systems for quantifying the impact of heavy water on gene expression and establish a platform to further assess the potential therapeutic use of heavy water as antiproliferative agent.

scholarly journals Cell-derived Extracellular Matrix as maintaining Biomaterial for adipogenic differentiation

2020 ◽  
Vol 6 (3) ◽  
pp. 410-413
Author(s):  
Petra J. Kluger ◽  
Svenja Nellinger ◽  
Simon Heine ◽  
Ann-Cathrin Volz
Keyword(s):  
Tissue Engineering ◽  
Extracellular Matrix ◽  
Adipogenic Differentiation ◽  
Cellular Activity ◽  
Adipose Tissue Engineering ◽  
Physical Support ◽  
Supporting Effect ◽  
Brdu Assay ◽  
The Impact

AbstractThe extracellular matrix (ECM) naturally surrounds cells in humans, and therefore represents the ideal biomaterial for tissue engineering. ECM from different tissues exhibit different composition and physical characteristics. Thus, ECM provides not only physical support but also contains crucial biochemical signals that influence cell adhesion, morphology, proliferation and differentiation. Next to native ECM from mature tissue, ECM can also be obtained from the in vitro culture of cells. In this study, we aimed to highlight the supporting effect of cell-derived- ECM (cdECM) on adipogenic differentiation. ASCs were seeded on top of cdECM from ASCs (scdECM) or pre-adipocytes (acdECM). The impact of ECM on cellular activity was determined by LDH assay, WST I assay and BrdU assay. A supporting effect of cdECM substrates on adipogenic differentiation was determined by oil red O staining and subsequent quantification. Results revealed no effect of cdECM substrates on cellular activity. Regarding adipogenic differentiation a supporting effect of cdECM substrates was obtained compared to control. With these results, we confirm cdECM as a promising biomaterial for adipose tissue engineering.

scholarly journals Circadian clock control of eIF2α phosphorylation is necessary for rhythmic translation initiation

2020 ◽  
Vol 117 (20) ◽  
pp. 10935-10945 ◽  
Author(s):  
Shanta Karki ◽  
Kathrina Castillo ◽  
Zhaolan Ding ◽  
Olivia Kerr ◽  
Teresa M. Lamb ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Nutrient Metabolism ◽  
Eif2α Phosphorylation ◽  
Eif2α Kinase ◽  
The Impact

The circadian clock in eukaryotes controls transcriptional and posttranscriptional events, including regulation of the levels and phosphorylation state of translation factors. However, the mechanisms underlying clock control of translation initiation, and the impact of this potential regulation on rhythmic protein synthesis, were not known. We show that inhibitory phosphorylation of eIF2α (P-eIF2α), a conserved translation initiation factor, is clock controlled in Neurospora crassa, peaking during the subjective day. Cycling P-eIF2α levels required rhythmic activation of the eIF2α kinase CPC-3 (the homolog of yeast and mammalian GCN2), and rhythmic activation of CPC-3 was abolished under conditions in which the levels of charged tRNAs were altered. Clock-controlled accumulation of P-eIF2α led to reduced translation during the day in vitro and was necessary for the rhythmic synthesis of select proteins in vivo. Finally, loss of rhythmic P-eIF2α levels led to reduced linear growth rates, supporting the idea that partitioning translation to specific times of day provides a growth advantage to the organism. Together, these results reveal a fundamental mechanism by which the clock regulates rhythmic protein production, and provide key insights into how rhythmic translation, cellular energy, stress, and nutrient metabolism are linked through the levels of charged versus uncharged tRNAs.

scholarly journals Generation of a mutant form of protein synthesis initiation factor eIF-2 lacking the site of phosphorylation by eIF-2 kinases.

1988 ◽  
Vol 8 (2) ◽  
pp. 993-995 ◽  
Author(s):  
V K Pathak ◽  
D Schindler ◽  
J W Hershey
Keyword(s):  
Protein Synthesis ◽  
Mammalian Cells ◽  
Covalent Modification ◽  
Site Directed Mutagenesis ◽  
Initiation Factor ◽  
Alpha Subunit ◽  
Mutant Form ◽  
Two Dimensional Gel Electrophoresis ◽  
Reticulocyte Lysate

The phosphorylation of the alpha-subunit of initiation factor eIF-2 leads to an inhibition of protein synthesis in mammalian cells. We have performed site-directed mutagenesis on a cDNA encoding the alpha-subunit of human eIF-2 and have replaced the candidate sites of phosphorylation, Ser-48 and Ser-51, with alanines. The cDNAs were expressed in vitro by SP6 polymerase transcription and rabbit reticulocyte lysate translation, and the radiolabeled protein products were analyzed by high-resolution two-dimensional gel electrophoresis. The wild-type and Ser-48 mutant proteins became extensively phosphorylated by eIF-2 kinases present in the reticulocyte lysate, and when additional heme-controlled repressor or double-stranded RNA-activated kinase was present, phosphorylation of the proteins was enhanced. The Ser-51 mutant showed little covalent modification by the endogenous enzymes and showed no increase in the acidic variant with additional eIF-2 kinases, thereby suggesting that Ser-51 is the site of phosphorylation leading to repression of protein synthesis.

scholarly journals Autophosphorylation sites participate in the activation of the double-stranded-RNA-activated protein kinase PKR.

1996 ◽  
Vol 16 (11) ◽  
pp. 6295-6302 ◽  
Author(s):  
D R Taylor ◽  
S B Lee ◽  
P R Romano ◽  
D R Marshak ◽  
A G Hinnebusch ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Initiation Factor ◽  
Double Stranded Rna ◽  
Catalytic Domains ◽  
Dependent Protein ◽  
Mutant Kinase

The interferon-induced RNA-dependent protein kinase PKR is found in cells in a latent state. In response to the binding of double-stranded RNA, the enzyme becomes activated and autophosphorylated on several serine and threonine residues. Consequently, it has been postulated that autophosphorylation is a prerequisite for activation of the kinase. We report the identification of PKR sites that are autophosphorylated in vitro concomitantly with activation and examine their roles in the activation of PKR. Mutation of one site, threonine 258, results in a kinase that is less efficient in autophosphorylation and in phosphorylating its substrate, the initiation factor eIF2, in vitro. The mutant kinase is also impaired in vivo, displaying reduced ability to inhibit protein synthesis in yeast and mammalian cells and to induce a slow-growth phenotype in Saccharomyces cerevisiae. Mutations at two neighboring sites, serine 242 and threonine 255, exacerbated the effect. Taken together with earlier results (S. B. Lee, S. R. Green, M. B. Mathews, and M. Esteban, Proc. Natl. Acad. Sci. USA 91:10551-10555, 1994), these data suggest that the central part of the PKR molecule, lying between its RNA-binding and catalytic domains, regulates kinase activity via autophosphorylation.

scholarly journals Simple Silica Column–Based Method to Quantify Inorganic Polyphosphates in Cartilage and Other Tissues

Cartilage ◽  
2017 ◽  
Vol 9 (4) ◽  
pp. 417-427 ◽  
Author(s):  
Whitaik David Lee ◽  
Rahul Gawri ◽  
Toshikazu Shiba ◽  
Ae-Ri Ji ◽  
William L. Stanford ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Inhibitory Effect ◽  
Proteinase K ◽  
Inorganic Polyphosphates ◽  
Column Method ◽  
Spin Column ◽  
Mammalian Tissues ◽  
Biological Sources ◽  
Low Levels

Objective. Inorganic polyphosphates (polyP) play a multitude of roles in mammalian biology. PolyP research is hindered by the lack of a simple and sensitive quantification method. The aim of this study was to develop a robust method for quantifying the low levels of polyP in mammalian tissue such as cartilage, which is rich in macromolecules that interfere with its determination. Design. Native and in vitro formed tissues were digested with proteinase K to release sequestrated polyP. The tissue digest was loaded on to silica spin columns, followed by elution of bound polyP and various treatments were assessed to minimize non-polyP fluorescence. The eluent was then quantified for polyP content using fluorometry based on DAPI (4′,6-diamidino-2-phenylindole) fluorescence shift occurring with polyP. Results. Proteinase K pretreatment reduced the inhibitory effect of proteins on polyP recovery. The eluent was contaminated with nucleic acids and glycosaminoglycans, which cause extraneous fluorescence signals. These were then effectively eliminated by nucleases treatment and addition of concentrated Tris buffer. PolyP levels were quantified and recovery ratio determined using samples spiked with a known amount of polyP. This silica spin column method was able to recover at least 80% of initially loaded polyP, and detect as little as 10−10 mol. Conclusions. This sensitive, reproducible, easy to do method of quantifying polyP will be a useful tool for investigation of polyP biology in mammalian cells and tissues. Although the protocol was developed for mammalian tissues, this method should be able to quantify polyP in most biological sources, including fluid samples such as blood and serum.

DAPI Method: A Novel Assay to Evaluate the In vitro Impact of Nanomaterials on Mammalian Cells

2006 ◽  
Vol 951 ◽  
Author(s):  
Pavan M. V. Raja ◽  
Jennifer Connolley ◽  
Pulickel M. Ajayan ◽  
Omkaram Nalamasu ◽  
Deanna M. Thompson
Keyword(s):  
Image Analysis ◽  
Mammalian Cells ◽  
Biological Impact ◽  
Simple Estimate ◽  
Aortic Smooth Muscle ◽  
Diphenyltetrazolium Bromide ◽  
Wide Range ◽  
The Impact ◽  
Non Destructive

ABSTRACTThe increasing importance of nanomaterial-related applications has given rise to concerns pertaining to their impact on human health. In vitro mammalian cell-based assays can provide a quick and simple estimate of the possible adverse effects of the nanomaterials. However, recent studies have questioned the efficacy of traditional assays such as the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, in evaluating cell-nanomaterial interactions, implying the need for alternate methods. We applied image analysis to enumerate the DAPI (2-[4-(Aminomethyl) phenyl]-1H-indole-6-carboximidamide, dihydrochloride) – stained cellular nuclei. Image analysis, being non-destructive, capable of automation, and applicable over a wide range of cell seeding densities, offers several advantages compared to older methods like the MTT assay and hemocytometry. Using image analysis, the impact of singlewalled carbon nanotubes (SWNT) on rat aortic smooth muscle cell (SMC) growth kinetics, were examined. Despite the carbon nanomaterial presence, the fluorescent signal from the nuclei was not noticeably impacted over the SWNT range examined (0.00-0.10 mg/ml). We anticipate that this method can also be applied to evaluate the biological impact of other nanomaterials.

scholarly journals A feedback transcriptional mechanism controls the level of the arginine/lysine transporter cat-1 during amino acid starvation

2007 ◽  
Vol 402 (1) ◽  
pp. 163-173 ◽  
Author(s):  
Alex B. Lopez ◽  
Chuanping Wang ◽  
Charlie C. Huang ◽  
Ibrahim Yaman ◽  
Yi Li ◽  
...  
Keyword(s):  
Amino Acid ◽  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Mammalian Cells ◽  
Leucine Zipper ◽  
Amino Acid Starvation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Basic Leucine Zipper

The adaptive response to amino acid limitation in mammalian cells inhibits global protein synthesis and promotes the expression of proteins that protect cells from stress. The arginine/lysine transporter, cat-1, is induced during amino acid starvation by transcriptional and post-transcriptional mechanisms. It is shown in the present study that the transient induction of cat-1 transcription is regulated by the stress response pathway that involves phosphorylation of the translation initiation factor, eIF2 (eukaryotic initiation factor-2). This phosphorylation induces expression of the bZIP (basic leucine zipper protein) transcription factors C/EBP (CCAAT/enhancer-binding protein)-β and ATF (activating transcription factor) 4, which in turn induces ATF3. Transfection experiments in control and mutant cells, and chromatin immunoprecipitations showed that ATF4 activates, whereas ATF3 represses cat-1 transcription, via an AARE (amino acid response element), TGATGAAAC, in the first exon of the cat-1 gene, which functions both in the endogenous and in a heterologous promoter. ATF4 and C/EBPβ activated transcription when expressed in transfected cells and they bound as heterodimers to the AARE in vitro. The induction of transcription by ATF4 was inhibited by ATF3, which also bound to the AARE as a heterodimer with C/EBPβ. These results suggest that the transient increase in cat-1 transcription is due to transcriptional activation caused by ATF4 followed by transcriptional repression by ATF3 via a feedback mechanism.

scholarly journals Binding and Nuclear Relocalization of Protein Kinase R by Human Cytomegalovirus TRS1

2006 ◽  
Vol 80 (23) ◽  
pp. 11817-11826 ◽  
Author(s):  
Morgan Hakki ◽  
Emily E. Marshall ◽  
Katherine L. De Niro ◽  
Adam P. Geballe
Keyword(s):  
Protein Kinase ◽  
Human Cytomegalovirus ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Underlying Mechanism ◽  
Cellular Protein ◽  
Initiation Factor ◽  
Protein Kinase R ◽  
Double Stranded Rna

ABSTRACT The human cytomegalovirus (HCMV) TRS1 and IRS1 genes block the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α) and the consequent shutoff of cellular protein synthesis that occur during infection with vaccinia virus (VV) deleted of the double-stranded RNA binding protein gene E3L (VVΔE3L). To further define the underlying mechanism, we first evaluated the effect of pTRS1 on protein kinase R (PKR), the double-stranded RNA (dsRNA)-dependent eIF2α kinase. Immunoblot analyses revealed that pTRS1 expression in the context of a VVΔE3L recombinant decreased levels of PKR in the cytoplasm and increased its levels in the nucleus of infected cells, an effect not seen with wild-type VV or a VVΔE3L recombinant virus expressing E3L. This effect of pTRS1 was confirmed by visualizing the nuclear relocalization of PKR-EGFP expressed by transient transfection. PKR present in both the nuclear and cytoplasmic fractions was nonphosphorylated, indicating that it was unactivated when TRS1 was present. PKR also accumulated in the nucleus during HCMV infection as determined by indirect immunofluorescence and immunoblot analysis. Binding assays revealed that pTRS1 interacted with PKR in mammalian cells and in vitro. This interaction required the same carboxy-terminal region of pTRS1 that is necessary to rescue VVΔE3L replication in HeLa cells. The carboxy terminus of pIRS1 was also required for rescue of VVΔE3L and for mediating an interaction of pIRS1 with PKR. These results suggest that these HCMV genes directly interact with PKR and inhibit its activation by sequestering it in the nucleus, away from both its activator, cytoplasmic dsRNA, and its substrate, eIF2α.

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