Transmembrane delivery of polypeptide growth factors bypassing the intrinsic cell surface receptors: synthesis and biological activity of a conjugate of epidermal growth factor with alpha 2-macroglobulin.
Epidermal growth factor (EGF) was derivatized at the amino terminus with N-succinimidyl 3-(2-pyridyldithio)propionate and then cross-linked to the cysteinyl residues of alpha 2-macroglobulin (alpha 2M) via disulfide bonds. The EGF-alpha 2M conjugate delivered EGF into dense lysosomal fractions through binding to alpha 2M receptors in a variant of mouse Swiss/3T3 fibroblasts, NR-6, which are deficient in EGF receptors. The conjugate stimulated DNA synthesis in Swiss/3T3 cells, but it did not stimulate DNA synthesis in NR-6 cells. This differential stimulation was due to the conjugate's binding to EGF receptors since bacitracin, which completely inhibits [125I]alpha 2M binding to its receptors, inhibited conjugate binding by approximately 80%. Thus, EGF bound to and internalized through alpha 2M receptors does not function as a mediator for DNA stimulation. The mechanisms of action of the conjugate are discussed in relation to the role of receptor-mediated endocytic pathways.
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D055598:Chemical Phenomena; D002621:Chemistry; D004261:DNA Replication / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D007202:Indicators and Reagents; D007700:Kinetics; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D011971:Receptors, Immunologic / Q000302:isolation & purification / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000378:metabolism* / Q000494:pharmacology
D007202:Indicators and Reagents; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D000511:alpha-Macroglobulins; D004815:Epidermal Growth Factor