title: Heat shock induces the release of fibroblast growth factor 1 from NIH 3T3 cells.
abstract: Fibroblast growth factor 1 (FGF-1) is a potent angiogenic and neurotrophic factor whose structure lacks a classical signal sequence for secretion. Although the initiation of these biological activities involves the interaction between FGF-1 and cell surface receptors, the mechanism responsible for the regulation of FGF-1 secretion is unknown. We report that murine NIH 3T3 cells transfected with a synthetic gene encoding FGF-1 secrete FGF-1 into their conditioned medium in response to heat shock. The form of FGF-1 released by NIH 3T3 cells in response to increased temperature (42 degrees C, 2 hr) in vitro is not biologically active and does not associate with either heparin or the extracellular NIH 3T3 monolayer matrix. However, it was possible to derive biologically active FGF-1 from the conditioned medium of heat-shocked NIH 3T3 cell transfectants by ammonium sulfate fractionation. The form of FGF-1 exposed by ammonium sulfate fractionation is similar in size to cytosolic FGF-1 and can bind and be eluted from immobilized heparin similarly to the recombinant human FGF-1 polypeptide. Further, the release of FGF-1 by NIH 3T3 cell transfectants in response to heat shock is reduced significantly by both actinomycin D and cycloheximide. These data indicate that increased temperature may upregulate the expression of a factor responsible for the secretion of FGF-1 as a biologically inactive complex that requires an activation step to exhibit the biological activity of the extracellular polypeptide mitogen.
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002455:Cell Division; D017077:Culture Media, Conditioned; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D003609:Dactinomycin / Q000494:pharmacology; D016220:Fibroblast Growth Factor 1 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D005813:Genes, Synthetic; D006358:Hot Temperature; D015151:Immunoblotting; D007700:Kinetics; D051379:Mice; D011994:Recombinant Proteins / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014162:Transfection; D014316:Tritium
chemical_list: D017077:Culture Media, Conditioned; D011994:Recombinant Proteins; D014316:Tritium; D016220:Fibroblast Growth Factor 1; D003609:Dactinomycin; D004247:DNA; D003513:Cycloheximide; D013936:Thymidine