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PubMed2006

The POLARIS peptide of Arabidopsis regulates auxin transport and root growth via effects on ethylene signaling.

The rate and plane of cell division and anisotropic cell growth are critical for plant development and are regulated by diverse mechanisms involving several hormone signaling pathways. Little is known about peptide signaling in plant growth; however, Arabidopsis thaliana POLARIS (PLS), encoding a 36-amino acid peptide, is required for correct root growth and vascular development. Mutational analysis implicates a role for the peptide in hormone responses, but the basis of PLS action is obscure. Using the Arabidopsis root as a model to study PLS action in plant development, we discovered a link between PLS, ethylene signaling, auxin homeostasis, and microtubule cytoskeleton dynamics. Mutation of PLS results in an enhanced ethylene-response phenotype, defective auxin transport and homeostasis, and altered microtubule sensitivity to inhibitors. These defects, along with the short-root phenotype, are suppressed by genetic and pharmacological inhibition of ethylene action. PLS expression is repressed by ethylene and induced by auxin. Our results suggest a mechanism whereby PLS negatively regulates ethylene responses to modulate cell division and expansion via downstream effects on microtubule cytoskeleton dynamics and auxin signaling, thereby influencing root growth and lateral root development. This mechanism involves a regulatory loop of auxin-ethylene interactions.

Amino Acids, Cyclic↗
PubMed2000

Cytosolic phospholipase A(2) regulates golgi structure and modulates intracellular trafficking of membrane proteins.

The Golgi complex and the trans-Golgi network are critical cellular organelles involved in the endocytic and biosynthetic pathways of protein trafficking. Lipids have been implicated in the regulation of membrane-protein trafficking, vesicular fusion, and targeting. We have explored the role of cytosolic group IV phospholipase A(2) (cPLA(2)) in membrane-protein trafficking in kidney epithelial cells. Adenoviral expression of cPLA(2) in LLC-PK(1) kidney epithelial cells prevents constitutive trafficking to the plasma membrane of an aquaporin 2-green fluorescent protein chimera, with retention of the protein in the rough endoplasmic reticulum. Plasma membrane Na(+)-K(+)-ATPase alpha-subunit localization is markedly reduced in cells expressing cPLA(2), whereas the trafficking of a Cl(-)/HCO(3)(-) anion exchanger to the plasma membrane is not altered in these cells. Expression of cPLA(2) results in dispersion of giantin and beta-COP from their normal, condensed Golgi localization, and in marked disruption of the Golgi cisternae. cPLA(2) is present in Golgi fractions from noninfected LLC-PK(1) cells and rat kidney cortex. The distribution of tubulin and actin was not altered by cPLA(2), indicating that the microtubule and actin cytoskeleton remain intact. Total cellular protein synthesis is unaffected by the increase in cPLA(2) activity. Thus cPLA(2) plays an important role in determining Golgi architecture and selective control of constitutive membrane-protein trafficking in renal epithelial cells.

Antiporters↗
PubMed1992

Neurotoxic effects of dietary aluminium.

Neurochemical responses to chronic oral aluminium administration have been studied in rats. Aluminium (0.3%) was added to drinking water of adult rats for four weeks or longer and weanling rats were given aluminium for eight weeks. Selective cognitive impairment was demonstrated in the adult rats. Aluminium inhibited calcium flux and phosphoinositide metabolism, one product of which (inositol 1,4,5-trisphosphate) modulates intracellular calcium levels. In weanling rats aluminium decreased the in vivo concentration of inositol 1,4,5-trisphosphate in the hippocampus. An increase in cyclic AMP concentrations by 30-70% in various brain regions in adult and weanling rats was found. Aluminium enhanced agonist-stimulated but not basal cyclic AMP production in vitro. It was postulated that aluminium inhibits the GTPase activity of the stimulatory G protein, Gs, leading to prolonged activation of Gs after receptor stimulation and increased cyclic AMP production. Aluminium treatment also increased the phosphorylation of microtubule-associated protein 2 (MAP-2) and the 200 kDa neurofilament protein (NF-H) but several other phosphoproteins were unaffected. Concentrations of seven structural proteins--MAP-2, tau, NF-H, NF-M (150 kDa), NF-L (68 kDa), tubulin and spectrin--were measured in rat brain regions by immunoblot methods. MAP-2 was most consistently decreased. These studies show that chronic oral aluminium administration to rats has significant neurochemical consequences. Three sites of action are implicated: altered calcium homeostasis, enhanced cyclic AMP production, and changes in cytoskeletal protein phosphorylation states and concentrations.

Aluminum↗
PubMed2004

Proteomic analysis of brown planthopper: application to the study of carbamate toxicity.

Toxicity to o-sec-butylphenyl methylcarbamate compound (BPMC) was analyzed in the rice brown planthopper, Nilaparvata lugens, using a differential proteomics approach of identifying proteins on two dimensional-polyacrylamide gel electrophoresis (2D-PAGE). Proteome analysis from BPMC-treated brown planthopper resulted in the modulation of 22 proteins at the expression level as compared to control samples on coomassie brilliant blue (CBB) stained gels. Out of total 22 proteins, 10 proteins showed elevated expression, eight proteins showed decreased expression and four proteins showed specific expression after insecticide treatment. The N-terminal sequences of seven out of 22 proteins were determined by a gas-phase protein sequencer. The internal amino acid sequences of the 15 proteins were determined by the sequence analyses of peptides obtained by Cleveland peptide mapping method and were compared with those of the known proteins available in public databases and the EST database of the brown planthopper in our laboratory to understand the nature of the proteins. Sequence analyses revealed that the expression of putative serine/threonine protein kinase, paramyosin, HSP 90, beta-tubulin, calreticulin, ATP synthase, actin and tropomyosin was elevated, and that of beta-mitochondrial processing peptidase, dihydrolipoamide dehydrogenase, enolase and acyl-coA dehydrogenase was reduced due to the exposure of BPMC. The differential expression of these proteins reflects the overall change in cellular structure and metabolism after insecticide treatment.

Amino Acid Sequence↗
PubMed2001

Neurosteroids: beginning of the story.

Neurosteroids are synthetisized in the central and the peripheral nervous system, in glial cells, and also in neurons, from cholesterol or steroidal precursors imported from peripheral sources. They include 3 beta-hydroxy-delta 5-compounds, such as pregnenolone (PREG) and dehydroepiandrosterone, their sulfate esters, and compounds known as reduced metabolites of steroid hormones, such as the tetrahydroderivative of progesterone 3 alpha-hydroxy-5 alpha-pregnan-20-one. These neurosteroids can act as modulators of neurotransmitter receptors, such as GABAA, NMDA, and sigma 1 receptors. Progesterone itself is also a neurosteroid, and a progesterone receptor has been detected in peripheral and central glial cells. At different sites in the brain, neurosteroid concentrations vary according to environmental and behavioral circumstances, such as stress, sex recognition, or aggressiveness. A physiological function of neurosteroids in the central nervous system is strongly suggested by the role of hippocampal PREGS with respect to memory performance, observed in aging rats. In the peripheral nervous system, a role for PROG synthesized in Schwann cells has been demonstrated in remyelination after cryolesion of the sciatic nerve in vivo and in cultures of dorsal root ganglia. A new mechanism of PREG action discovered in the brain involves specific steroid binding to microtubule associated protein and increased tubulin polymerization for assembling microtubules. It may be important to study the effects of abnormal neurosteroid concentration/metabolism in view of the possible treatment of functional and trophic disturbances of the nervous system.

Animals↗
PubMed2000

Actin-dependent lamellipodia formation and microtubule-dependent tail retraction control-directed cell migration.

Migrating cells are polarized with a protrusive lamella at the cell front followed by the main cell body and a retractable tail at the rear of the cell. The lamella terminates in ruffling lamellipodia that face the direction of migration. Although the role of actin in the formation of lamellipodia is well established, it remains unclear to what degree microtubules contribute to this process. Herein, we have studied the contribution of microtubules to cell motility by time-lapse video microscopy on green flourescence protein-actin- and tubulin-green fluorescence protein-transfected melanoma cells. Treatment of cells with either the microtubule-disrupting agent nocodazole or with the stabilizing agent taxol showed decreased ruffling and lamellipodium formation. However, this was not due to an intrinsic inability to form ruffles and lamellipodia because both were restored by stimulation of cells with phorbol 12-myristate 13-acetate in a Rac-dependent manner, and by stem cell factor in melanoblasts expressing the receptor tyrosine kinase c-kit. Although ruffling and lamellipodia were formed without microtubules, the microtubular network was needed for advancement of the cell body and the subsequent retraction of the tail. In conclusion, we demonstrate that the formation of lamellipodia can occur via actin polymerization independently of microtubules, but that microtubules are required for cell migration, tail retraction, and modulation of cell adhesion.

Actins↗
PubMed1998

Characterization of microtubule binding domains in the Arabidopsis kinesin-like calmodulin binding protein.

The kinesin-like calmodulin binding protein (KCBP) is a new member of the kinesin superfamily that appears to be present only in plants. The KCBP is unique in its ability to interact with calmodulin in a Ca2+-dependent manner. To study the interaction of the KCBP with microtubules, we expressed different regions of the Arabidopsis KCBP and used the purified proteins in cosedimentation assays with microtubules. The motor domain with or without the calmodulin binding domain bound to microtubules. The binding of the motor domain containing the calmodulin binding region to microtubules was inhibited by Ca2+-calmodulin. This Ca2+-calmodulin regulation of motor domain interactions with microtubules was abolished in the presence of antibodies specific to the calmodulin binding region. In addition, the binding of the motor domain lacking the calmodulin binding region to microtubules was not inhibited in the presence of Ca2+-calmodulin, suggesting an essential role for the calmodulin binding region in Ca2+-calmodulin modulation. Results of the cosedimentation assays with the N-terminal tail suggest the presence of a second microtubule binding site on the KCBP. However, the interaction of the N-terminal tail region of the KCBP with microtubules was insensitive to ATP. These data on the interaction of the KCBP with microtubules provide new insights into the functioning of the KCBP in plants.

Animals↗
PubMed2000

Modulation of Rho and cytoskeletal protein attachment to membranes by a prenylcysteine analog.

The GTPases Rho regulate the assembly of polymerized actin structures. Their C-terminal sequences end with the CAAX motif that undergo a lipidation of the cysteine residue. Analogs to the C-terminal ends of Rho proteins, N-acetyl-S-all-trans, trans-farnesyl-L-cysteine and N-acetyl-S-all-trans-geranylgeranyl-L-cysteine, wereused to analyze the role of prenylation in their membrane association. Silver-stained gels indicated that N-acetyl-S-all-trans-geranylgeranyl-L-cysteine treatment released only a few proteins of 20, 46, and 60 kDa. Western blot analysis showed that N-acetyl-S-all-trans-geranylgeranyl-L-cysteine released RhoB (10%), RhoA (28%), and Cdc42 (95%) from membranes, whereas N-acetyl-S-all-trans and trans-farnesyl-L-cysteine did not. Rab1, which possesses two geranylgeranyl groups, was also strongly extracted by N-acetyl-S-all-trans-geranylgeranyl-L-cysteine, whereas Ras, which is farnesylated, was not. Furthermore, N-acetyl-S-all-trans-geranylgeranyl-L-cysteine was very efficient (95%) in dissociating actin and tubulin from membranes but not integral membrane protein P-glycoprotein and sodium/phosphate cotransporter NaP(i)-2. The extraction of Rho and cytoskeletal proteins occurred below the critical micellar concentration of N-acetyl-S-all-trans-geranylgeranyl-L-cysteine. Membrane treatments with 0.7 m KI totally extracted actin, whereas 70% of Cdc42 was released. Actin was, however, insoluble in Triton X-100-treated membranes, whereas this detergent extracted (80%) Cdc42. These data show that Rho proteins and actin are not physically bound together and suggest that their extraction from membranes by N-acetyl-S-all-trans-geranylgeranyl-L-cysteine likely occurs via different mechanisms.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Selective inhibition of the expression of signal transduction proteins by lithium in nerve growth factor-differentiated PC12 cells.

This investigation examined if lithium, the primary therapeutic treatment for bipolar affective disorder, modulated the levels of selected signal transduction proteins in PC12 cells. Nerve growth factor (NGF) induced differentiation of PC12 cells, and after 12 days of NGF treatment there were large increases in the levels of the heterotrimeric G protein subunits alpha o1, alpha i1, beta, and alpha s, small increases in those of alpha i2 and alpha q, and a slight decrease in that of alpha o2. Lithium (1 mM, equivalent to the therapeutic concentration) selectively reduced NGF-induced increases in levels of G protein subunits, generally having the greatest inhibition on those that were increased the most by NGF. Lithium at 5 mM had greater inhibitory effects than 1 mM lithium on NGF-induced increases in levels of G proteins, but neither concentration of lithium affected the induction of the cytoskeletal protein beta-tubulin. Examination of other proteins involved in signal transduction revealed that 12 days of NGF treatment increased the level of protein kinase C-alpha, but not those of the beta, epsilon, or zeta subtypes, and did not alter the levels of beta, gamma, or delta phospholipase C. Pretreatment with lithium inhibited the increase in content of protein kinase C-alpha induced by NGF but had little effect on the proteins not responsive to NGF except for decreasing the levels of protein kinase C-epsilon. The inhibitory effect of lithium was found not to be due to inhibition of NGF-induced tyrosine phosphorylation, which was unaffected by 5 mM lithium, or to inositol depletion. In summary, use of the dynamic system of NGF-induced PC12 cell differentiation provided a sensitive model in which to identify signal transduction proteins that were influenced by lithium treatment. The large changes caused by a therapeutically equivalent concentration of lithium lend support to the proposal that the selective inhibitory effects of lithium on subtypes of G proteins and protein kinase C may be important therapeutic targets.

Animals↗
PubMed1998

Induction of matrix metalloproteinase-9 requires a polymerized actin cytoskeleton in human malignant glioma cells.

Alterations in cytoskeleton and subsequent cell shape changes exert specific effects on the expression of various genes. Our previous results suggested that malignant human gliomas express elevated levels of matrix metalloproteinases compared with normal brain tissue and low grade gliomas. To understand the role of cell shape changes on matrix metalloproteinase expression in human glioma cells, we treated SNB19 cells with cytochalasin-D, an inhibitor of actin polymerization, and colchicine-B, a tubulin inhibitor, in the presence of phorbol 12-myristate 13-acetate. Cytochalasin-D treatment of SNB19 cells resulted in the loss of phorbol 12-myristate 13-acetate-induced matrix metalloproteinase-9 (also known as gelatinase-B) expression and coincided with inhibition of actin polymerization, resulting in cell rounding. Moreover, compared with monolayers, cells grown as spheroids or cell aggregates failed to express matrix metalloproteinase-9 in the presence of phorbol 12-myristate 13-acetate. Matrix metalloproteinase-9 expression was also inhibited by calphostin-C, a protein kinase inhibitor, suggesting the involvement of protein kinase C in matrix metalloproteinase-9 expression. Phorbol 12-myristate 13-acetate-induced invasion of SNB19 cells through Matrigel was inhibited by cytochalasin-D and calphostin-C. These results suggest that the actin polymerization transduces signals that modulate the expression of matrix metalloproteinase-9 expression and the subsequent invasion of human glioma cells.

Actins↗
PubMed1988

Release of intact microtubule-capping structures from Tetrahymena cilia.

The distal ends of ciliary microtubules are attached to the membrane by microtubule-capping structures. The capping structures are located at the sites of tubulin addition and loss in vivo and may be part of the regulatory system that directs ciliary and flagellar microtubule assembly. This study describes conditions for the release and stabilization of microtubule capping structures as a first step in their purification. Two types of capping structures, the distal filaments and the central microtubule caps, are selectively and independently released from the axoneme by CaCl2 and MgCl2 but not by MgSO4, ZnCl2, NaCl, KCl, or KI. The release of the caps and filaments is specific for Ca+2, Mg+2, and Cl- and is not simply a function of ionic strength. The capping structures are released without major disruption of the axonemal structure. In addition to providing a means to purify and identify the cap and filament components, these results suggest ways in which their binding to the axoneme may be modulated during periods of microtubule growth or shortening. This report also reveals that the distal filaments are composed of two separable components, a small bead inserted into the end of each A-tubule and a "Y"-shaped plug and filament that slips through the bead.

Animals↗
PubMed2000

Z-1,1-Dichloro-2,3-diphenylcyclopropanes block human prostate carcinoma cell proliferation, inhibit prostate-specific antigen expression, and initiate apoptosis.

BACKGROUND: Z-1,1-Dichloro-2,3-diphenylcyclopropane (A(II)) has long been known to be active against models of breast carcinoma. Microtubule perturbation and interaction at type II estrogen binding sites mediate its actions. METHODS: Since these targets are potentially useful for treatment of prostate tumors, we studied the drug's effects on androgen-sensitive (LNCaP) and -independent (PC-3) human prostatic carcinoma lines. Effects on cell growth and morphology, prostate-specific antigen (PSA) expression, and cell cycle kinetics were determined by microscopy, antibody-based methods, flow cytometry, and electrophoresis. RESULTS: At 100 microM, A(II) reduced survival of both lines by 50% in 12-24 hr, whereas 10 microM A(II) caused a prolonged block of proliferation in both lines, and parallel and complete block of PSA in LNCaP cells. At 10 microM, A(II) caused no major changes in chromatin, morphology or cell cycle distributions, whereas 100 microM drug caused rapid, large-scale cell detachment, nuclear and internucleosomal DNA fragmentation, and hypodiploidy. These effects were also accompanied by dissolution of cellular microtubule arrays. A more potent tubulin assembly-inhibiting congener of A(II), Z-1, 1-dichloro-2-(4-methoxy-phenyl)-3-phenylcyclopropane, slightly more effectively inhibited cell growth, caused little hypodiploidy, but potently and dose-dependently caused G(2)/M accumulation. CONCLUSIONS: These and previous data suggest that the Z-1, 1-dichloro-2,3-diarylcyclo-propanes may be useful in the treatment of human prostate disease.

Androgens↗
PubMed2004

Surfing, regulating and capturing: are all microtubule-tip-tracking proteins created equal?

A diverse group of microtubule-binding proteins has been linked through live-cell imaging of green fluorescent protein (GFP) fusion proteins. These proteins share the ability to associate with the plus ends of elongating microtubules and track with these tips as the microtubules grow, in a process known as "tip tracking". Several models have been proposed to explain the significance of this activity, including roles in delivering proteins to the cell periphery and in modulating microtubule dynamics. However, the recent observation that some of the tip trackers colocalize on structures undergoing search-capture suggests that tip tracking could be a fundamental aspect of the search-capture process. Focusing on the shared ability of these proteins to undergo tip tracking, this article is intended to place the search-capture model in the context of other proposed functions and to stimulate discussion in this area.

Dyneins↗
PubMed1998

Proteasome activator (PA28) subunits, alpha, beta and gamma (Ki antigen) in NT2 neuronal precursor cells and HeLa S3 cells.

The catalytic activity of the 20S proteasome can be modulated by endogenous proteins. A proteasome activator protein termed PA28 or 11S regulator, composed of two homologous subunits (alpha and beta) and a separate but related protein termed Ki antigen or PA28gamma have been characterized. To explore the functional relationship of these proteins, NT2 clone D1 human neuronal precursor cells, as well as HeLa S3 cells were labeled by immunofluorescence and immunoelectron microscopy with three different antisera directed against peptides derived from their sequences. It was found that both PA28alpha and PA28beta antisera label the cytoplasm and the nucleoli. In contrast, the PA28gamma antiserum labels the nucleus but not the nucleoli while in the cytoplasm it labels two different classes of structures identified as microtubular-like extensions and inclusion bodies that are most likely autophagosomes. The latter do not contain proteasome delta subunit antigen. The microtubular-like structures colocalize with beta-tubulin, are dispersed by nocodazole and are not affected by brefeldin A treatment. PA28alpha and PA28beta are co-localized in the cell whereas PA28gamma has a different distribution. PA28gamma complexed with the proteasome may serve a function other than or in addition to activation and may also have a proteasome-independent function.

Autoantigens↗
PubMed2001

Interaction between pyrin and the apoptotic speck protein (ASC) modulates ASC-induced apoptosis.

Patients with familial Mediterranean fever suffer sporadic inflammatory attacks characterized by fever and intense pain (in joints, abdomen, or chest). Pyrin, the product of the MEFV locus, is a cytosolic protein whose function is unknown. Using pyrin as a "bait" to probe a yeast two-hybrid library made from neutrophil cDNA, we isolated apoptotic speck protein containing a caspase recruitment domain (CARD) (ASC), a proapoptotic protein that induces the formation of large cytosolic "specks" in transfected cells. We found that when HeLa cells are transfected with ASC, specks are formed. After co-transfection of cells with ASC plus wild type pyrin, an increase in speck-positive cells is found, and speck-positive cells show increased survival. Immunofluorescence studies show that pyrin co-localizes with ASC in specks. Speck localization requires exon 1 of pyrin, but exon 1 alone of pyrin does not result in an increase in the number of specks. Exon 1 of pyrin and exon 1 of ASC show 42% sequence similarity and resemble death domain-related structures in modeling studies. These findings link pyrin to apoptosis pathways and suggest that the modulation of cell survival may be a component of the pathophysiology of familial Mediterranean fever.

Actins↗
PubMed1994

Clinical, toxicological and pharmaceutical aspects of the antineoplastic drug taxol: a review.

Taxol, a diterpene alkaloid isolated from the bark of Taxus brevifolia, has a unique mechanism of action. The drug promotes the formation of microtubule polymers in a cell, by reversibly and specifically binding the beta-subunit of tubulin. Taxol is administered intravenously by a 3-24-hour infusion at 3-week intervals. Myelosuppression, especially neutropenia, appears to be the dose limiting toxicity in solid tumours at 200-250 mg/m2. Furthermore, side effects such as sensory neurotoxicity (with typical numbness, tingling and painful paraesthesiae in the extremities), diarrhoea and alopecia appear frequently. Mucositis appears to be the non-haematological dose limiting side effect at 390 mg/m2 that has been determined in patients with leukaemia. Hypersensitivity reactions, which have been fatal in individual cases, might be schedule dependent. Furthermore, antiallergic prophylaxis must be given, although this precaution might not be considered to be fully protective. Phase I studies performed with combinations of taxol and cisplatin, doxorubicin or cyclophosphamide have indicated the feasibility of these regimens and show promise for future investigations. Addition of granulocyte-colony stimulating factor (G-CSF), aimed at modulating myelosuppressive toxicity, showed in Phase I studies that the taxol dose could be increased to 250 mg/m2, with peripheral neuropathy as the dose limiting toxicity. In Phase II studies, taxol has been shown to be effective, including producing complete tumour remission, in advanced drug refractory ovarian carcinoma (19%-36% response rate), previously treated patients with metastatic breast carcinoma (27%-62% response rate), advanced non-small lung cancer (21%-24% response rate), advanced small cell lung cancer (37% response rate) and advanced head and neck cancer (34% response rate).(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

A novel 205-kilodalton testis-specific serine/threonine protein kinase associated with microtubules of the spermatid manchette.

To identify proteins which interact with and potentially modulate the function of microtubules during spermatogenesis, we prepared a total testis MAP (microtubule-associated protein) antiserum and used it to isolate cDNA clones from a mouse testis cDNA expression library. Antibodies affinity purified by using one expression clone recognized a 205-kDa protein, termed MAST205, which colocalizes with the spermatid manchette. Sequencing of full-length cDNA clones encoding MAST205 revealed it to be a novel serine/threonine kinase with a catalytic domain related to those of the A and C families. The testis-specific MAST205 RNA increases in abundance during prepuberal testis development, peaking at the spermatid stage. The microtubule-binding region of MAST205 occupies a central region of the molecule including the kinase domain and sequences C terminal to this domain. Binding of MAST205 to microtubules requires interaction with other MAPs, since it does not bind to MAP-free tubulin. A 75-kDa protein associated with immunoprecipitates of MAST205 from extracts of both whole testis and testis microtubules becomes phosphorylated in in vitro kinase assays. This 75-kDa substrate of the MAST205 kinase may form part of the MAST205 protein complex which binds microtubules. The MAST205 protein complex may function to link the signal transduction pathway with the organization of manchette microtubules.

Amino Acid Sequence↗
PubMed2005

In vitro and in vivo effects of deoxynivalenol (DNV) on regulators of cap dependent translation control in porcine endometrium.

Deoxynivalenol (DNV) is the most frequently encountered trichothecene in grain-based foods, and is able to produce toxic effects resulting in various diseases in farm and laboratory animals. The molecular mechanisms that control this mycotoxin mediated effects in porcine endometrial cells are far from being completely understood. Recent results show that DNV inhibits protein synthesis in actively proliferating tissues. Therefore, the present study investigated the effects of this mycotoxin on a cellular level in an in vivo and in vitro system. The abundance and phosphorylation state (activity) of the cell cycle dependent kinases MAPk and Akt (PKB) and their potential targets eIF-4E (eukaryotic initiation factor 4E) and 4E-BP1 (4E binding protein, eIF4E repressor protein) were examined. In previous investigations it was found that these factors are involved in initiation of mRNA translation. The results show that DNV in vitro strongly reduce the abundance of p38 MAPk, protein kinase Akt and the alpha- and beta-4E-BP1 bands. The phosphorylation state of these proteins was obviously not modulated. In contrast, the eIF4E phosphorylation was strongly reduced in DNV treated cells. In summary, our in vitro results let assume that DNV potentially influences gene expression, but this work does not present a direct proof that DNV alters processes, which are involved in the initiation of mRNA translation. Surprisingly in vivo, an influence of DNV feeding on the investigated molecular events could not be demonstrated.

Animals↗