A permeable FGF-1 nuclear localization sequence peptide induces DNA synthesis independently of Ras activation.
A 26-amino-acid peptide (designated PFNP) composed of the nuclear localization signal of fibroblast growth factor (FGF)-1 and a membrane-permeable peptide is known to mimic FGF-1's ability to stimulate DNA synthesis in various cell types at low cell densities. The underlying molecular mechanism is unknown, however. Here we show that PFNP activity is inhibited in murine fibroblasts by a tyrosine kinase inhibitor, that PFNP does not bind to the FGF receptor, and that PFNP does not induce phosphorylation of the FGF receptor substrate. In addition, expression of a dominant-negative form of Ras, which abolished the activities of epidermal growth factor (EGF) and heparin-binding EGF, had no affect on PFNP-induced DNA synthesis. Despite this apparent Ras independence, PFNP activity correlated with phosphorylation of ERK1/2 MAP kinases and was concentration dependently inhibited by inhibitors of ERK1/2 MAP kinase phosphorylation. These results indicate that whereas Ras activation is dispensable for PFNP-induced DNA synthesis, activation of tyrosine kinases and ERK1/2 kinases, albeit independently of the FGF receptor system, is crucial. Interestingly, FGF-1 signaling was predominantly Ras-independent when the cell density was optimum for PFNP, suggesting that PFNP and FGF-1 share the same signaling mechanism.
Komi
Akiko
A
Age Dimension Research Center, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Ishisaki
Akira
A
Suzuki
Masashi
M
Imamura
Toru
T
D016475:3T3 Cells; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000235:genetics; D002451:Cell Compartmentation / Q000235:genetics; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis* / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005057:Eukaryotic Cells / Q000187:drug effects / Q000378:metabolism*; D016220:Fibroblast Growth Factor 1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017468:Receptors, Fibroblast Growth Factor / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014443:Tyrosine / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D017468:Receptors, Fibroblast Growth Factor; D016220:Fibroblast Growth Factor 1; D014443:Tyrosine; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins