title: Expression of three recombinant homodimeric isoforms of PDGF in Saccharomyces cerevisiae: evidence for difference in receptor binding and functional activities.
abstract: Three recombinant homodimeric isoforms of platelet-derived growth factor (PDGF) were produced and purified in milligram quantities by expression of PDGF A- and B-chains in yeast cells. Structural analysis of the purified short and long variants of PDGF-AA (PDGF-AAS and PDGF-AAL) and PDGF-BB showed that they had been properly processed and assembled into dimers. PDGF-AAS and PDGF-AAL were found to bind only to the PDGF A-type receptor on human fibroblasts, with affinities of 0.1 and 0.2 nM, respectively. PDGF-BB bound to cells with A- and B-type receptors and to cells with B-type receptor only with affinities of 0.6 nM in both cases. Each fibroblast appeared to express about 4-5 times more B-type receptors than A-type receptors. The maximal mitogenic response to PDGF-BB of human fibroblasts was almost 2-fold higher than that induced by either of the two PDGF-AA forms. The three isoforms of PDGF also stimulated growth in soft agar of human fibroblasts with PDGF-BB inducing a higher maximal response.
authors.affiliation: Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Ostman
authors.forename: G
authors.initials: G
authors.lastname: Bäckström
authors.forename: N
authors.initials: N
authors.lastname: Fong
authors.forename: C
authors.initials: C
authors.lastname: Betsholtz
authors.forename: C
authors.initials: C
authors.lastname: Wernstedt
authors.forename: U
authors.initials: U
authors.lastname: Hellman
authors.forename: B
authors.initials: B
authors.lastname: Westermark
authors.forename: P
authors.initials: P
authors.lastname: Valenzuela
authors.forename: C H
authors.initials: CH
authors.lastname: Heldin
mesh_terms: D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects; D005822:Genetic Vectors; D006801:Humans; D066298:In Vitro Techniques; D008934:Mitogens; D008969:Molecular Sequence Data; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis* / Q000302:isolation & purification / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014170:Transformation, Genetic
chemical_list: D008934:Mitogens; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D017479:Receptors, Platelet-Derived Growth Factor