title: A soluble dominant negative fibroblast growth factor receptor 4 isoform in human MCF-7 breast cancer cells.
abstract: Fibroblast growth factor receptors (FGFRs) are receptor tyrosine kinases encoded by four closely related genes. FGFR 1, 2, and 3 have a number of isoforms derived by alternative splicing, alternative initiation and exon switching; however, FGFR4 has been reported to encode a single intact receptor with three extracellular immunoglobulin (Ig)-like domains, a transmembrane domain, and a split intracellular kinase. Here we describe a novel C-terminally truncated soluble isoform of FGFR4 expressed by human epithelial breast cancer MCF-7 cells. This isoform results from failure of splicing of intron 4 resulting in an mRNA species that encodes an in-frame premature stop codon. Cells transfected with the corresponding cDNA containing intron 4 express a truncated releasable protein that is identified in conditioned media. This soluble FGFR4 isoform (sFGFR4) abrogates the effect of FGF-1-induced MAPK phosphorylation and PRL gene activation. These findings represent the first description of an endogenous soluble C-terminally truncated FGFR4 isoform with FGF modulatory properties.
authors.affiliation: Department of Medicine, University of Toronto, 600 University Avenue, Toronto, Ontario, Canada M5G-1X5. sezzat@mtsinai.on.ca
authors.forename: S
authors.initials: S
authors.lastname: Ezzat
authors.forename: L
authors.initials: L
authors.lastname: Zheng
authors.forename: S
authors.initials: S
authors.lastname: Yu
authors.forename: S L
authors.initials: SL
authors.lastname: Asa
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D016220:Fibroblast Growth Factor 1; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D007438:Introns / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D012326:RNA Splicing; D051499:Receptor, Fibroblast Growth Factor, Type 4; D017468:Receptors, Fibroblast Growth Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012995:Solubility; D014407:Tumor Cells, Cultured
chemical_list: D020033:Protein Isoforms; D017468:Receptors, Fibroblast Growth Factor; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; C496371:FGFR4 protein, human; C496372:Fgfr4 protein, mouse; D051499:Receptor, Fibroblast Growth Factor, Type 4