title: EGFR ligands exhibit functional differences in models of paracrine and autocrine signaling.
abstract: Epidermal growth factor (EGF) family peptides are ligands for the EGF receptor (EGFR). Here, we elucidate functional differences among EGFR ligands and mechanisms underlying these distinctions. In 32D/EGFR myeloid and MCF10A breast cells, soluble amphiregulin (AR), transforming growth factor alpha (TGFα), neuregulin 2 beta, and epigen stimulate greater EGFR coupling to cell proliferation and DNA synthesis than do EGF, betacellulin, heparin-binding EGF-like growth factor, and epiregulin. EGF competitively antagonizes AR, indicating that its functional differences reflect dissimilar intrinsic activity at EGFR. EGF stimulates much greater phosphorylation of EGFR Tyr1045 than does AR. Moreover, the EGFR Y1045F mutation and z-cbl dominant-negative mutant of the c-cbl ubiquitin ligase potentiate the effect of EGF but not of AR. Both EGF and AR stimulate phosphorylation of EGFR Tyr992. However, the EGFR Y992F mutation and phospholipase C gamma inhibitor U73122 reduce the effect of AR much more than that of EGF. Expression of TGFα in 32D/EGFR cells causes greater EGFR coupling to cell proliferation than does expression of EGF. Moreover, expression of EGF in 32D/EGFR cells causes these cells to be largely refractory to stimulation with soluble EGF. Thus, EGFR ligands are functionally distinct in models of paracrine and autocrine signaling and EGFR coupling to biological responses may be specified by competition among functionally distinct EGFR ligands.
authors.affiliation: Purdue University College of Pharmacy, Purdue University Center for Cancer Research, West Lafayette, IN 47907-2064, USA.
authors.forename: Kristy J
authors.initials: KJ
authors.lastname: Wilson
authors.forename: Christopher
authors.initials: C
authors.lastname: Mill
authors.forename: Sydney
authors.initials: S
authors.lastname: Lambert
authors.forename: Jennifer
authors.initials: J
authors.lastname: Buchman
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Wilson
authors.forename: Victor
authors.initials: V
authors.lastname: Hernandez-Gordillo
authors.forename: Richard M
authors.initials: RM
authors.lastname: Gallo
authors.forename: Laura M C
authors.initials: LM
authors.lastname: Ades
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Settleman
authors.forename: David J
authors.initials: DJ
authors.lastname: Riese
mesh_terms: D000818:Animals; D019898:Autocrine Communication / Q000502:physiology*; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D051379:Mice; D019899:Paracrine Communication / Q000502:physiology*; D010766:Phosphorylation; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D008024:Ligands; D014443:Tyrosine; D004815:Epidermal Growth Factor; D050721:Proto-Oncogene Proteins c-cbl; D066246:ErbB Receptors