Characterization of a membrane receptor for transforming growth factor-beta in normal rat kidney fibroblasts.
A procedure has been developed for the iodination of human transforming growth factor-beta (TGF-beta) with full retention of biological activity. Using the iodinated peptide, saturable receptors have been found for TGF-beta on normal rat kidney fibroblasts, a cell line that will grow in soft agar in the presence of TGFs but not in their absence. Scatchard analysis of the binding data showed a high affinity binding site (dissociation constant equal to 25 to 30 pM with approximately 17,000 receptors per cell). The receptor was specific for TGF-beta with epidermal growth factor, insulin, insulin-like growth factors I and II, platelet-derived growth factor, and TGF-alpha being unable to compete for the binding of 125I-TGF-beta to the receptor. The binding of TGF-beta was a time- and temperature-dependent process. At 37 degrees C, maximal binding was attained within 45 to 60 min after addition of 125I-TGF-beta followed by a rapid decline in cell-associated radioactivity due to degradation of the 125I-TGF-beta. As demonstrated using ammonium acetate, a compound known to inhibit lysosomal enzymes, this degradation was most likely due to the action of proteolytic enzymes found in the lysosome. At 0 degrees C, binding reached a plateau within 2 to 3 h and maintained this level with no apparent drop during the 4-h incubation period. The receptor could be down-regulated by TGF-beta, but not by epidermal growth factor, to approximately 50% of the level initially observed.
D001667:Binding, Competitive; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D066246:ErbB Receptors; D005347:Fibroblasts / Q000378:metabolism; D006133:Growth Substances / Q000302:isolation & purification; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D010455:Peptides / Q000302:isolation & purification / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D015291:Transforming Growth Factors
D006133:Growth Substances; D010455:Peptides; D011956:Receptors, Cell Surface; D015291:Transforming Growth Factors; D066246:ErbB Receptors