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Proceedings of the National Academy of... Apr 1997Mitogen-activated protein kinase kinase (MEK) is a dual-specificity protein kinase that is located primarily in the cellular cytosol, both prior to and upon mitogenic...
Mitogen-activated protein kinase kinase (MEK) is a dual-specificity protein kinase that is located primarily in the cellular cytosol, both prior to and upon mitogenic stimulation. The existence of a nuclear export signal in the N-terminal domain of MEK [Fukuda, M., Gotoh, I., Gotoh, Y. & Nishida, E. (1996) J. Biol. Chem. 271, 20024-20028] suggests that there are circumstances under which MEK enters the nucleus and must be exported. Using mutants of MEK, we show that the deletion of the nuclear export signal sequence from constitutively active MEK caused constitutive localization of MEK in the nucleus of COS7 and HEK-293T cells. However, when the same region was deleted from a catalytically inactive MEK, cytoplasmic localization was observed in resting cells, which turned nuclear upon stimulation. Confocal microscopy of COS7 cells expressing the above mutants showed localization of the active MEK in the nuclear envelope and also in the cell periphery. The differences in cellular localization between the wild-type and mutant MEKs are not due to severe changes in specificity because the recombinant, constitutively active MEK that lacked its N-terminal region exhibited the same substrate specificity as the wild-type MEK, both in vitro and in intact cells. Taken together, our results indicate that upon mitogenic stimulation, MEK, like extracellular signal responsive kinase and p90(RSK), is massively translocated to the nucleus. Rapid export from the nucleus, which is mediated by the nuclear export signal, is probably the cause for the cytoplasmic distribution observed with wild-type MEK.
Topics: Animals; Biological Transport; COS Cells; Cell Nucleus; Humans; MAP Kinase Kinase 1; Microscopy, Fluorescence; Mitogen-Activated Protein Kinase Kinases; Mitogens; Protein Serine-Threonine Kinases; Protein-Tyrosine Kinases
PubMed: 9108048
DOI: 10.1073/pnas.94.8.3742 -
Infection and Immunity Jun 2003This study investigated whether the recently recognized emergence of canine streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (NF) might be partly...
This study investigated whether the recently recognized emergence of canine streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (NF) might be partly attributed to the use of fluoroquinolones to treat Streptococcus canis infections in dogs. Both mitomycin and the fluoroquinolone enrofloxacin caused bacteriophage-induced lysis of S. canis strain 34, an isolate from a case of canine STSS and NF. Fluoroquinolone-evoked, bacteriophage-induced lysis occurred over a range of concentrations similar to those that would occur after treatment of dogs with these agents. To search for a possible bacteriophage-encoded streptococcal superantigen gene(s), a library of the 36.5 (+/-1.1)-kb bacteriophage, designated phisc1, was made by ligating 3- to 7-kb Tsp5091-digested phisc1 fragments into an EcoRI-digested lambdaZapII vector. Recombinants were screened for mitogenic activity by using canine peripheral blood lymphocytes. Of 800 recombinants screened, 11 recombinants with mitogenic effects were identified, and their inserts were sequenced. The highest homology of 11.6 kb of sequenced phisc1 DNA was to the completely sequenced Streptococcus pneumoniae bacteriophage MM1. Seven of the 11 phisc1 sequenced inserts contained a 552-bp open reading frame, scm, with 27% amino acid similarity to pokeweed (Phytolacca americana) mitogen. PCR showed this gene to be present in 22 of 23 S. canis isolates tested. Quantitative reverse transcription-PCR showed that bacteriophage induction was associated with a 58-fold enhancement of expression of this gene relative to that in a noninduced culture of a similar age. The presence of this gene on a fluoroquinolone-induced bacteriophage may explain the association observed between fluoroquinolone use in dogs and the development of canine STTS and NF.
Topics: Amino Acid Sequence; Animals; Anti-Infective Agents; Blotting, Southern; DNA, Viral; Dog Diseases; Dogs; Enrofloxacin; Fluoroquinolones; Mitogens; Mitomycin; Molecular Sequence Data; Pokeweed Mitogens; Polymerase Chain Reaction; Quinolones; Streptococcal Infections; Streptococcus; Streptococcus Phages; Virulence
PubMed: 12761079
DOI: 10.1128/IAI.71.6.3028-3033.2003 -
Molecular Microbiology Mar 2003A mitogenic substance, designated Streptococcus dysgalactiae-derived mitogen (SDM), was purified from S. dysgalactiae culture supernatant, and the gene encoding the...
A mitogenic substance, designated Streptococcus dysgalactiae-derived mitogen (SDM), was purified from S. dysgalactiae culture supernatant, and the gene encoding the mitogen was cloned. Both native and recombinant SDM expressed in Escherichia coli significantly activated human V beta 1+ and V beta 23+ T cells in association with major histocompatibility complex (MHC) class II molecules on accessory cells, indicating that SDM possesses superantigenic properties. The sdm gene consists of two segments encoding a signal peptide and a mature 25 kDa protein composed of 212 amino acids. Three of 34 S. dysgalactiae strains but none of 28 Streptococcus pyogenes strains examined carried sdm. Phylogenetic analysis indicated that SDM belongs to a family distinct from established bacterial superantigens. SDM showed around 30% homology with other superantigens at the amino acid sequence level. The tertiary structure of SDM was predicted by modelling onto streptococcal pyrogenic exotoxin C and streptococcal mitogenic exotoxin Z-2, both of which share highly homologous structure-determining regions. SDM showed overall structural similarity to both these superantigens. This is the first study to characterize fully a bacterial superantigen from S. dysgalactiae.
Topics: Amino Acid Sequence; Animals; Antigens, Bacterial; Bacterial Proteins; Bacterial Toxins; Base Sequence; Escherichia coli; Exotoxins; Histocompatibility Antigens Class II; Humans; Membrane Proteins; Mitogens; Models, Molecular; Molecular Sequence Data; Phylogeny; Protein Structure, Tertiary; Receptors, Antigen, T-Cell, alpha-beta; Recombinant Proteins; Sequence Analysis; Sequence Homology, Amino Acid; Streptococcus; Structural Homology, Protein; Superantigens; T-Lymphocytes
PubMed: 12622814
DOI: 10.1046/j.1365-2958.2003.03411.x -
Molecular Oncology Aug 2021In psychotherapy, paradoxical interventions are characterized by a deliberate reinforcement of the pathological behavior to improve the clinical condition. Such a... (Review)
Review
In psychotherapy, paradoxical interventions are characterized by a deliberate reinforcement of the pathological behavior to improve the clinical condition. Such a counter-intuitive approach can be considered when more conventional interventions fail. The development of targeted cancer therapies has enabled the selective inhibition of activated oncogenic signaling pathways. However, in advanced cancers, such therapies, on average, deliver modest benefits due to the development of resistance. Here, we review the perspective of a 'paradoxical intervention' in cancer therapy: rather than attempting to inhibit oncogenic signaling, the proposed therapy would further activate mitogenic signaling to disrupt the labile homeostasis of cancer cells and overload stress response pathways. Such overactivation can potentially be combined with stress-targeted drugs to kill overstressed cancer cells. Although counter-intuitive, such an approach exploits intrinsic and ubiquitous differences between normal and cancer cells. We discuss the background underlying this unconventional approach and how such intervention might address some current challenges in cancer therapy.
Topics: Cell Proliferation; Drug Resistance, Neoplasm; Homeostasis; Humans; Mitogens; Neoplasms; Signal Transduction; Tumor Microenvironment
PubMed: 33955157
DOI: 10.1002/1878-0261.12979 -
Cellular Immunology Jan 1976
Topics: Animals; Concanavalin A; Lectins; Lymphocyte Activation; Male; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Mitogens
PubMed: 1248052
DOI: 10.1016/0008-8749(76)90340-3 -
Current Biology : CB Feb 2001Much is known about how cell proliferation is controlled at the single cell level, but much less about the control of cell numbers in developing populations. Cell number...
BACKGROUND
Much is known about how cell proliferation is controlled at the single cell level, but much less about the control of cell numbers in developing populations. Cell number might be determined by an intracellular division limiter or, alternatively, by the availability of mitogens or other factors outside the cell. We investigated the relative importance of intracellular and extracellular controls for one well-defined population of neural precursor cells, namely the glial progenitors that give rise to oligodendrocytes in the mouse spinal cord.
RESULTS
We found by cumulative BrdU labeling in vivo that the progenitor cell division cycle slows down markedly as their numbers increase during embryogenesis. When cultured in saturating PDGF, the main mitogen for these cells, their cell cycle accelerated and was independent of their prior rate of division in vivo. This shows that mitogens are limiting in vivo, and suggests that division normally slows down because the PDGF concentration declines. In PDGF-transgenic mice, cell number was proportional to the PDGF supply and apparently unsaturable; at ten times the normal rate of supply, cell number was still increasing but the animals were no longer viable.
CONCLUSIONS
Progenitor cell proliferation in the embryo is limited by environmental factors, not a cell-intrinsic mechanism. The linear relationship between PDGF supply and final cell number strongly suggests that cells deplete the mitogenic activity in their environment at a rate proportional to the total number of cells. The cells might simply consume the available PDGF or they might secrete autocrine inhibitors, or both.
Topics: Animals; Cell Count; Cell Cycle; Cells, Cultured; Dose-Response Relationship, Drug; Embryonic and Fetal Development; Mice; Mitogens; Oligodendroglia; Platelet-Derived Growth Factor; Spinal Cord; Stem Cells; Time Factors
PubMed: 11250151
DOI: 10.1016/s0960-9822(01)00075-6 -
Journal of Dairy Science Jun 1993A substance, active as a B-cell mitogen, was isolated from the slime products produced by Lactococcus lactis ssp. cremoris KVS20. The mitogenic substance was prepared by... (Comparative Study)
Comparative Study
A substance, active as a B-cell mitogen, was isolated from the slime products produced by Lactococcus lactis ssp. cremoris KVS20. The mitogenic substance was prepared by anion-exchange chromatography and gel filtration chromatography and then purified by proteinase digestion and HPLC. Chemical analysis determined that the mitogenic substance was a phosphopolysaccharide and consisted of rhamnose, glucose, galactose, and phosphorus. The activity of the mitogenic substance was higher than that of the slime products. The optimal concentration for the activity was approximately 120 micrograms/ml. The mitogenic substance also had substantial mitogenic activity to spleen cells from C3H/HeJ mice, which are resistant to lipopolysaccharide. The findings indicated that a B-cell mitogen different from lipopolysaccharide is produced from L. lactis ssp. cremoris KVS20.
Topics: Animals; B-Lymphocytes; Chromatography, Gel; Lactococcus lactis; Lipopolysaccharides; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Nude; Milk; Mitogens; Spleen
PubMed: 8326024
DOI: 10.3168/jds.S0022-0302(93)77483-4 -
American Journal of Reproductive... Nov 1999The purpose of this study was the isolation and characterization of decidual extract proteins that exhibit mitogenicity on endothelial cells.
PROBLEM
The purpose of this study was the isolation and characterization of decidual extract proteins that exhibit mitogenicity on endothelial cells.
METHOD OF STUDY
A partially purified extract (F1 fraction) was obtained from human decidua of the first trimester of pregnancy. F1 was separated by heparin-sepharose column and showed significant mitogenicity on bovine brain capillary endothelial (BBCE) cells in vitro, using methylene blue stain nuclear assay. Sodium-dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed four fractions with MW less than 30 KDa.
RESULTS
Mitogenic fraction, E11-12 (eluted at 1.5 M NaCl) was identified as basic fibroblast growth factor (bFGF). Vascular endothelial growth factor (VEGF) and acidic (a)FGF were not identified as one of the mitogenic fractions. However, fractions E5-6, and E7-8 induced statistically significant mitogenicity at concentration of 1 pg/mL, which is 10(3) times lower than bFGF. Sequencing of E5-6 fraction identified NKG5 protein, a putative secreted polypeptide derived from human natural killer (NK) cells and activated T cells of unknown function.
CONCLUSION
This work demonstrates that NKG5 stimulates mitogenicity of endothelial cells and may be involved in angiogenesis.
Topics: Angiogenesis Inducing Agents; Animals; Antigens, Differentiation, T-Lymphocyte; Cattle; Cells, Cultured; Chemical Fractionation; Decidua; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Female; Fibroblast Growth Factor 2; Humans; Mitogens; Molecular Weight; Pregnancy; Receptors, Immunologic
PubMed: 10584980
DOI: 10.1111/j.1600-0897.1999.tb00100.x -
American Journal of Physiology. Cell... Aug 2001The coagulation cascade protease thrombin is a fibroblast mitogen, but the proliferative potential of other coagulation proteases is not known. In this study we show...
The coagulation cascade protease thrombin is a fibroblast mitogen, but the proliferative potential of other coagulation proteases is not known. In this study we show that factor Xa stimulated human fetal lung fibroblast DNA synthesis in a concentration-dependent manner from 1 nM onward with a fourfold increase at 200 nM. The mitogenic effect of factor Xa was confirmed using a colorimetric proliferation assay and direct cell counting. Factor Xa and thrombin had equivalent potencies, and their stimulatory effects followed a similar time course. Comparable results were also obtained with primary human adult fibroblasts derived from lung, kidney, heart, skin, and liver. Factor VIIa also stimulated fibroblast proliferation, but only at concentrations >10 nM, whereas factor IXa had no effect. To begin to address the mechanism by which factor Xa is acting, we show that human fibroblasts express effector-cell protease receptor-1 and that blocking antibodies to this receptor and the catalytic site of factor Xa inhibited its mitogenic effect. Furthermore, factor Xa upregulated platelet-derived growth factor-A (PDGF-A) mRNA expression, whereas PDGF-B could not be detected, and a blocking antibody to PDGF inhibited the mitogenic effect of factor Xa. We conclude that factor Xa acts as a fibroblast mitogen via binding to effector-cell protease receptor-1 and the autocrine release of PDGF.
Topics: Adult; Autocrine Communication; Cell Division; Factor IXa; Factor VIIa; Factor Xa; Fibroblasts; Humans; Inhibitor of Apoptosis Proteins; Male; Mitogens; Peptide Hydrolases; Platelet-Derived Growth Factor; Receptors, Cell Surface; Survivin; Thrombin
PubMed: 11443067
DOI: 10.1152/ajpcell.2001.281.2.C681 -
Cancer Letters Mar 2002Research into the molecular basis of cancer has a central tenet. Cancer arises from genetic alterations that disconnect growth and differentiation signaling pathways... (Review)
Review
Research into the molecular basis of cancer has a central tenet. Cancer arises from genetic alterations that disconnect growth and differentiation signaling pathways from the machinery that regulates cellular proliferation. In multi-cellular eukaryotes, proliferation is regulated by external signals, such as the availability of growth factors and nutrients and by internal signals, such as those sensing cellular integrity. Cellular stress created either by lack of mitogens or damage to cellular components, such as DNA, stimulates responses that enforce temporal or permanent withdrawal from the cell cycle. Although these stress responses stem from different sources and activate distinct pathways, they converge on the same components of the cell cycle machinery in the G1 phase of the cell cycle. This review will highlight and compare aspects of the G1 arrest in response to stress generated either by lack of mitogens or damage to DNA.
Topics: Animals; DNA Damage; G1 Phase; Humans; Mitogens; Mitosis; Signal Transduction
PubMed: 11825657
DOI: 10.1016/s0304-3835(01)00785-6