The basic fibroblast growth factor-saporin mitotoxin acts through the basic fibroblast growth factor receptor.
We have confirmed the hypothesis that a mitotoxin resulting from the conjugation of basic fibroblast growth factor and saporin exerts its cytotoxic effect through specific interaction with the basic fibroblast growth factor (FGF) receptor. Accordingly, the mitotoxin stimulates tyrosine phosphorylation of the 90 kD substrate that characterizes the initial cellular response to basic FGF. Cross-linking experiments show that radio-labeled basic fibroblast growth factor-saporin (FGF-SAP) binds to the receptor. Suramin, an inhibitor of growth factor receptor binding, inhibits the cytotoxicity of basic FGF-SAP. In a study of 4 different cell types, there is a decrease in the ED50 of the mitotoxin as the receptor number per cell increases. We have verified the cytotoxicity of the mitotoxin in 3 different assay systems. As expected, it is effective in the inhibition of protein synthesis and DNA synthesis, as well as of cell count. Binding of basic FGF-SAP which will result in cytotoxicity occurs very rapidly; 5 minutes of incubation of 10 nM basic FGF-SAP with cells results in 80% inhibition of cell count. The in vitro data indicate that the basic FGF-SAP is a receptor specific and potent suicide antagonist of basic FGF. Its potential as an anti-FGF for therapeutic and research uses in vivo is discussed.
Lappi
D A
DA
Department of Molecular and Cellular Growth Biology, Whittier Institute for Diabetes and Endocrinology, La Jolla, California 92037.
Maher
P A
PA
Martineau
D
D
Baird
A
A
D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D003432:Cross-Linking Reagents; D003603:Cytotoxins; D004247:DNA / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D016222:Fibroblast Growth Factor 2 / Q000737:chemistry* / Q000378:metabolism; D000922:Immunotoxins; D066298:In Vitro Techniques; D009699:N-Glycosyl Hydrolases; D010940:Plant Proteins / Q000008:administration & dosage* / Q000737:chemistry; D014176:Protein Biosynthesis; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017468:Receptors, Fibroblast Growth Factor; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D013498:Suramin / Q000494:pharmacology
D003432:Cross-Linking Reagents; D003603:Cytotoxins; D000922:Immunotoxins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D017468:Receptors, Fibroblast Growth Factor; D054789:Ribosome Inactivating Proteins, Type 1; D016222:Fibroblast Growth Factor 2; D013498:Suramin; D004247:DNA; D011505:Protein-Tyrosine Kinases; D009699:N-Glycosyl Hydrolases; D000076985:Saporins