title: Constitutive secretion of an endogenous insulin-like peptide binding protein with high affinity for insulin in Spodoptera frugiperda (Sf9) cell cultures.
abstract: Serum-free medium from batch cultures of Sf9 insect cells was examined for the occurrence of proteins related to the insulin-like growth factor family. We found that the Sf9 cell line constitutively produced and secreted a soluble protein with a MW of 27 kDa that exerted specific binding to human insulin-like growth factor-I (IGF-I) and -II. Moreover, the secreted protein bound human insulin and human proinsulin with higher affinity than IGF-I and -II. The order of affinity to the insulin peptides, determined by competitive inhibition of ligand binding, was: insulin > proinsulin > IGF-I >> IGF-II. The dissociation constant (k(d)) for IGF-II was 28.5 +/- 1.7 nM and for insulin 7.2 +/- 1.3 nM, as determined by Scatchard plot analysis. The results suggest that the Sf9 cells produce an insulin binding protein similar to the human insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1).
authors.affiliation: Department of Biotechnology, Royal Institute of Technology, KTH, Stockholm, SE-100 44, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Doverskog
authors.forename: M
authors.initials: M
authors.lastname: Tally
authors.forename: L
authors.initials: L
authors.lastname: Häggström
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D011485:Protein Binding; D018411:Spodoptera
chemical_list: D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D007328:Insulin; D007335:Insulin-Like Growth Factor II