scholarly journals Regulation of Myogenesis by Fibroblast Growth Factors Requires Beta-Gamma Subunits of Pertussis Toxin-Sensitive G Proteins

1998 ◽  
Vol 18 (10) ◽  
pp. 5780-5787 ◽  
Author(s):  
Yuri V. Fedorov ◽  
Nathan C. Jones ◽  
Bradley B. Olwin
Keyword(s):  
Skeletal Muscle ◽  
Growth Factors ◽  
Growth Factor ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Intracellular Signaling ◽  
Mapk Pathway ◽  
Myogenic Differentiation ◽  
Terminal Differentiation ◽  
Fibroblast Growth

ABSTRACT Terminal differentiation of skeletal muscle cells in culture is inhibited by a number of different growth factors whose subsequent intracellular signaling events are poorly understood. In this study, we have investigated the role of heterotrimeric G proteins in mediating fibroblast growth factor (FGF)-dependent signals that regulate myogenic differentiation. Pertussis toxin, which ADP-ribosylates and inactivates susceptible G proteins, promotes terminal differentiation in the presence of FGF-2, suggesting that Gα or Gβγ subunits or both are involved in transducing the FGF-dependent signal(s) that inhibits myogenesis. We found that Gβγ subunits are likely to be involved since the expression of the C terminus of β-adrenergic receptor kinase 1, a Gβγ subunit-sequestering agent, promotes differentiation in the presence of FGF-2, and expression of the free Gβγ dimer can replace FGF-2, rescuing cells from pertussis toxin-induced differentiation. Addition of pertussis toxin also blocked FGF-2-mediated activation of mitogen-activated protein kinases (MAPKs). Ectopic expression of dominant active mutants in the Ras/MAPK pathway rescued cells from pertussis toxin-induced terminal differentiation, suggesting that the Gβγ subunits act upstream of the Ras/MAPK pathway. It is unlikely that the pertussis toxin-sensitive pathway is activated by other, as yet unidentified FGF receptors since PDGF (platelet-derived growth factor)-stimulated MM14 cells expressing a chimeric receptor containing the FGF receptor-1 intracellular domain and the PDGF receptor extracellular domain were sensitive to pertussis toxin. Our data suggest that FGF-mediated signals involved in repression of myogenic differentiation are transduced by a pertussis toxin-sensitive G-protein-coupled mechanism. This signaling pathway requires the action of Gβγ subunits and activation of MAPKs to repress skeletal muscle differentiation.

scholarly journals The oncogenic forms of N-ras or H-ras prevent skeletal myoblast differentiation.

1987 ◽  
Vol 7 (6) ◽  
pp. 2104-2111 ◽  
Author(s):  
E N Olson ◽  
G Spizz ◽  
M A Tainsky
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Transforming Growth Factor ◽  
Myogenic Differentiation ◽  
Myoblast Differentiation ◽  
Specific Gene ◽  
Gene Products ◽  
Fibroblast Growth ◽  
Ras Genes

Differentiation of skeletal muscle involves withdrawal of myoblasts from the cell cycle, fusion to form myotubes, and the coordinate expression of a variety of muscle-specific gene products. Fibroblast growth factor and type beta transforming growth factor specifically inhibit myogenesis; however, the transmembrane signaling pathways responsible for suppression of differentiation by these growth factors remain elusive. Because ras proteins have been implicated in the transduction of growth factor signals across the plasma membrane, we used DNA-mediated gene transfer to investigate the potential involvement of this family of regulatory proteins in the control of myogenesis. Transfection of the mouse skeletal muscle cell line C2 with the oncogenic forms of H-ras or N-ras completely suppressed both myoblast fusion and induction of the muscle-specific gene products nicotinic acetylcholine receptor and creatine kinase. Inhibition of differentiation by activated ras genes occurred at the level of muscle-specific mRNA accumulation. In contrast, proto-oncogenic forms of N-ras or H-ras had no apparent effects on the ability of C2 cells to differentiate. Myoblasts transfected with activated ras genes exhibited normal growth properties and ceased proliferating in the absence of mitogens, indicating that ras inhibited differentiation through a mechanism independent of cell proliferation. These results demonstrate that activated ras gene products mimic the inhibitory effects of fibroblast growth factor and type beta transforming growth factor on myogenic differentiation and suggest that each of these regulators of myogenesis may operate through a common intracellular pathway.

The oncogenic forms of N-ras or H-ras prevent skeletal myoblast differentiation

1987 ◽  
Vol 7 (6) ◽  
pp. 2104-2111
Author(s):  
E N Olson ◽  
G Spizz ◽  
M A Tainsky
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Transforming Growth Factor ◽  
Myogenic Differentiation ◽  
Myoblast Differentiation ◽  
Specific Gene ◽  
Gene Products ◽  
Fibroblast Growth ◽  
Ras Genes

Differentiation of skeletal muscle involves withdrawal of myoblasts from the cell cycle, fusion to form myotubes, and the coordinate expression of a variety of muscle-specific gene products. Fibroblast growth factor and type beta transforming growth factor specifically inhibit myogenesis; however, the transmembrane signaling pathways responsible for suppression of differentiation by these growth factors remain elusive. Because ras proteins have been implicated in the transduction of growth factor signals across the plasma membrane, we used DNA-mediated gene transfer to investigate the potential involvement of this family of regulatory proteins in the control of myogenesis. Transfection of the mouse skeletal muscle cell line C2 with the oncogenic forms of H-ras or N-ras completely suppressed both myoblast fusion and induction of the muscle-specific gene products nicotinic acetylcholine receptor and creatine kinase. Inhibition of differentiation by activated ras genes occurred at the level of muscle-specific mRNA accumulation. In contrast, proto-oncogenic forms of N-ras or H-ras had no apparent effects on the ability of C2 cells to differentiate. Myoblasts transfected with activated ras genes exhibited normal growth properties and ceased proliferating in the absence of mitogens, indicating that ras inhibited differentiation through a mechanism independent of cell proliferation. These results demonstrate that activated ras gene products mimic the inhibitory effects of fibroblast growth factor and type beta transforming growth factor on myogenic differentiation and suggest that each of these regulators of myogenesis may operate through a common intracellular pathway.

scholarly journals Fibroblast growth factor and cyclic AMP (cAMP) synergistically activate gene expression at a cAMP response element

1994 ◽  
Vol 14 (11) ◽  
pp. 7546-7556
Author(s):  
Y Tan ◽  
K G Low ◽  
C Boccia ◽  
J Grossman ◽  
M J Comb
Keyword(s):  
Gene Expression ◽  
Growth Factors ◽  
Growth Factor ◽  
Cyclic Amp ◽  
Signaling Pathways ◽  
Intracellular Signaling ◽  
Gene Activation ◽  
Fibroblast Growth ◽  
Camp Response Element ◽  
Intracellular Signaling Pathways

Growth factors and cyclic AMP (cAMP) are known to activate distinct intracellular signaling pathways. Fibroblast growth factor (FGF) activates ras-dependent kinase cascades, resulting in the activation of MAP kinases, whereas cAMP activates protein kinase A. In this study, we report that growth factors and cAMP act synergistically to stimulate proenkephalin gene expression. Positive synergy between growth factor- and cAMP-activated signaling pathways on gene expression has not been previously reported, and we suggest that these synergistic interactions represent a useful model for analyzing interactions between these pathways. Transfection and mutational studies indicate that both FGF-dependent gene activation and cAMP-dependent gene activation require cAMP response element 2 (CRE-2), a previously characterized cAMP-dependent regulatory element. Furthermore, multiple copies of this element are sufficient to confer FGF regulation upon a minimal promoter, indicating that FGF and cAMP signaling converge upon transcription factors acting at CRE-2. Among many different ATF/AP-1 factors tested, two factors, ATF-3 and c-Jun, stimulate proenkephalin transcription in an FGF- or Ras-dependent fashion. Finally, we show that ATF-3 and c-Jun form heterodimeric complexes in SK-N-MC cells and that the levels of both proteins are increased in response to FGF but not cAMP. Together, these results indicate that growth factor- and cAMP-dependent signaling pathways converge at CRE-2 to synergistically stimulate gene expression and that ATF-3 and c-Jun regulate proenkephalin transcription in response to both growth factor- and cAMP-dependent intracellular signaling pathways.

Effects of growth factors on myogenic differentiation

1989 ◽  
Vol 256 (4) ◽  
pp. C701-C711 ◽  
Author(s):  
J. R. Florini ◽  
K. A. Magri
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Myogenic Differentiation ◽  
Terminal Differentiation ◽  
Muscle Cells ◽  
Tgf Beta ◽  
Molecular Events ◽  
Control Terminal

It has now been well established that the terminal differentiation of muscle cells in culture is subject to control by hormones and growth factors in the incubation medium. Thus far the most potent and most extensively studied agents are fibroblast growth factor (FGF), the insulinlike growth factors (IGFs), and transforming growth factor-beta (TGF-beta). Independent reports from several laboratories have established that both FGF and TGF-beta are potent inhibitors of differentiation and both appear to act at early stages of commitment to differentiation. Stimulation of differentiation by the IGFs (and by insulin at concentrations in the microgram/ml range) has also been observed and confirmed repeatedly. FGF and IGF are mitogenic for muscle cells, and TGF-beta either has no effect or suppresses cell proliferation, so previous generalizations that mitogens inhibit myogenic differentiation are clearly not valid when results with purified agents in well-defined media are considered. Work with oncogenes and specific toxins is beginning to reveal the mechanisms by which these agents might affect differentiation, and there is reason for optimism that an understanding of the molecular events that control terminal differentiation may be attained in the near future.

scholarly journals Growth factor control of skeletal muscle differentiation: commitment to terminal differentiation occurs in G1 phase and is repressed by fibroblast growth factor.

1987 ◽  
Vol 105 (2) ◽  
pp. 949-956 ◽  
Author(s):  
C H Clegg ◽  
T A Linkhart ◽  
B B Olwin ◽  
S D Hauschka
Keyword(s):  
Cell Cycle ◽  
Skeletal Muscle ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Muscle Development ◽  
Terminal Differentiation ◽  
Maximal Activity ◽  
G1 Phase ◽  
Fibroblast Growth ◽  
Regulatory Commitment

Analysis of MM14 mouse myoblasts demonstrates that terminal differentiation is repressed by pure preparations of both acidic and basic fibroblast growth factor (FGF). Basic FGF is approximately 30-fold more potent than acidic FGF and it exhibits half maximal activity in clonal assays at 0.03 ng/ml (2 pM). FGF repression occurs only during the G1 phase of the cell cycle by a mechanism that appears to be independent of ongoing cell proliferation. When exponentially growing myoblasts are deprived of FGF, cells become postmitotic within 2-3 h, express muscle-specific proteins within 6-7 h, and commence fusion within 12-14 h. Although expression of these three terminal differentiation phenotypes occurs at different times, all are initiated by a single regulatory "commitment" event in G1. The entire population commits to terminal differentiation within 12.5 h of FGF removal as all cells complete the cell cycle and move into G1. Differentiation does not require a new round of DNA synthesis. Comparison of MM14 behavior with other myoblast types suggests a general model for skeletal muscle development in which specific growth factors serve the dual role of stimulating myoblast proliferation and directly repressing terminal differentiation.

scholarly journals p42/mitogen-activated protein kinase as a converging target for different growth factor signaling pathways: use of pertussis toxin as a discrimination factor.

1991 ◽  
Vol 2 (8) ◽  
pp. 675-684 ◽  
Author(s):  
G L'Allemain ◽  
J Pouyssegur ◽  
M J Weber
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Protein Kinase ◽  
Map Kinase ◽  
Signaling Pathways ◽  
Fibroblast Growth Factor ◽  
Tyrosine Phosphorylation ◽  
Pertussis Toxin ◽  
Fibroblast Growth ◽  
Mitogen Activated Protein

Mitogen-activated protein (MAP) kinase is a 42-kDa serine/threonine-specific protein kinase that requires phosphorylation on both tyrosine and threonine residues for activity. This enzyme is rapidly and transiently activated in quiescent cells after addition of various agonists, including insulin, epidermal growth factor, platelet-derived growth factor, and phorbol esters. We show here that addition of the growth factors thrombin or basic fibroblast growth factor to CCL39 fibroblasts rapidly induces tyrosine phosphorylation of the p42 MAP kinase protein and concomitantly stimulates MAP kinase enzymatic activity. To elucidate the signaling pathways utilized in this activation, we took advantage of the sensitivity of CCL39 cells to the toxin of bordetella pertussis, which ADP-ribosylates two Gi proteins in this cell system. We show that pretreatment of cells with the toxin inhibited thrombin stimulation of MAP kinase by greater than 75% but had no detectable effect on the stimulation induced by basic fibroblast growth factor. We also demonstrate that these two growth factors that synergize for mitogenicity are able to cooperate in activation of MAP kinase and that this synergism is partially sensitive to pertussis toxin. Finally, we describe a 44-kDa protein, the tyrosine phosphorylation of which appears to be coregulated with p42 MAP kinase. We conclude that p42 MAP kinase (and the pp44 protein) are at or are downstream from a point of convergence of two different receptor-induced signaling pathways and might well play a key role in integrating those signals.

scholarly journals Fibroblast growth factor and cyclic AMP (cAMP) synergistically activate gene expression at a cAMP response element.

1994 ◽  
Vol 14 (11) ◽  
pp. 7546-7556 ◽  
Author(s):  
Y Tan ◽  
K G Low ◽  
C Boccia ◽  
J Grossman ◽  
M J Comb
Keyword(s):  
Gene Expression ◽  
Growth Factors ◽  
Growth Factor ◽  
Cyclic Amp ◽  
Signaling Pathways ◽  
Intracellular Signaling ◽  
Gene Activation ◽  
Fibroblast Growth ◽  
Camp Response Element ◽  
Intracellular Signaling Pathways

Growth factors and cyclic AMP (cAMP) are known to activate distinct intracellular signaling pathways. Fibroblast growth factor (FGF) activates ras-dependent kinase cascades, resulting in the activation of MAP kinases, whereas cAMP activates protein kinase A. In this study, we report that growth factors and cAMP act synergistically to stimulate proenkephalin gene expression. Positive synergy between growth factor- and cAMP-activated signaling pathways on gene expression has not been previously reported, and we suggest that these synergistic interactions represent a useful model for analyzing interactions between these pathways. Transfection and mutational studies indicate that both FGF-dependent gene activation and cAMP-dependent gene activation require cAMP response element 2 (CRE-2), a previously characterized cAMP-dependent regulatory element. Furthermore, multiple copies of this element are sufficient to confer FGF regulation upon a minimal promoter, indicating that FGF and cAMP signaling converge upon transcription factors acting at CRE-2. Among many different ATF/AP-1 factors tested, two factors, ATF-3 and c-Jun, stimulate proenkephalin transcription in an FGF- or Ras-dependent fashion. Finally, we show that ATF-3 and c-Jun form heterodimeric complexes in SK-N-MC cells and that the levels of both proteins are increased in response to FGF but not cAMP. Together, these results indicate that growth factor- and cAMP-dependent signaling pathways converge at CRE-2 to synergistically stimulate gene expression and that ATF-3 and c-Jun regulate proenkephalin transcription in response to both growth factor- and cAMP-dependent intracellular signaling pathways.

Loss of fibroblast growth factor receptors is necessary for terminal differentiation of embryonic limb muscle

Development ◽  
1996 ◽  
Vol 122 (1) ◽  
pp. 291-300 ◽  
Author(s):  
N. Itoh ◽  
T. Mima ◽  
T. Mikawa
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Muscle Mass ◽  
Terminal Differentiation ◽  
Limb Bud ◽  
Fibroblast Growth ◽  
Limb Muscle ◽  
Fgf Signaling ◽  
Myotomal Muscle

Early in embryogenesis, precursors of the limb musculature are generated in the somite, migrate to the limb buds and undergo terminal differentiation. Although myogenic differentiation in culture is affected by several growth factors including fibroblast growth factor (FGF), it remains uncertain whether migration and differentiation of myogenic cells in vivo are directly regulated by such growth factors. To investigate the roles of FGF signaling in the regulation of myogenesis both in the somite and the limb bud, mosaic chicken embryos were generated that consist of somitic cells carrying transgenes expressing one of the following: FGF1, FGF4, the FGF receptor type-1 (FGFR1) or its dominant negative mutant (delta FGFR1). Cells infected with virus producing FGF ligand migrated into the somatopleure without differentiating into myotomal muscle, but differentiated into muscle fibers when they arrived in the limb bud. In contrast, cells overexpressing FGFR1 migrated into the limb muscle mass but remained as undifferentiated myoblasts. Cells infected with the delta FGFR1-producing virus failed to migrate to the somatopleure but were capable of differentiating into myotomal muscle within the somites. These results suggest that the FGFR-mediated FGF signaling (1) blocks terminal differentiation of myogenic cells within the somite and (2) sustains myoblast migration to limb buds from the somite, and that (3) down-regulation of FGFRs or FGFR signaling is involved in mechanisms triggering terminal differentiation of the limb muscle mass during avian embryogenesis.

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