title: Interaction of insulin-like growth factor II (IGF-II) with multiple plasma proteins: high affinity binding of plasminogen to IGF-II and IGF-binding protein-3.
abstract: In the circulation, most of the insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs), and IGFBP proteases are bound in high molecular mass complexes of > or =150 kDa. To investigate molecular interactions between proteins involved in IGF.IGFBP complexes, Cohn fraction IV of human plasma was subjected to IGF-II affinity chromatography followed by reversed-phase high pressure liquid chromatography and analysis of bound proteins. Mass spectrometry and Western blotting revealed the presence of IGFBP-3, IGFBP-5, transferrin, plasminogen, prekallikrein, antithrombin III, and the soluble IGF-II/mannose 6-phosphate receptor in the eluate. Furthermore, an IGFBP-3 protease cleaving also IGFBP-2 but not IGFBP-4 was co-purified from the IGF-II column. Inhibitor studies and IGFBP-3 zymography have demonstrated that the 92-kDa IGFBP-3 protease belongs to the class of serine-dependent proteases. IGF-II ligand blotting and surface plasmon resonance spectrometry have been used to identify plasminogen as a novel high affinity IGF-II-binding protein capable of binding to IGFBP-3 with 50-fold higher affinity than transferrin. In combination with transferrin, the overall binding constant of plasminogen/transferrin for IGF-II was reduced 7-fold. Size exclusion chromatography of the IGF-II matrix eluate revealed that transferrin, plasminogen, and the IGFBP-3 protease are present in different high molecular mass complexes of > or =440 kDa. The present data indicate that IGFs, low and high affinity IGFBPs, several IGFBP-associated proteins, and IGFBP proteases can interact, which may result in the formation of binary, ternary, and higher molecular weight complexes capable of modulating IGF binding properties and the stability of IGFBPs.
authors.affiliation: University Hospital Hamburg Eppendorf, Children's Hospital, Department of Biochemistry, Martinistrasse 52, D-20246 Hamburg, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Oesterreicher
authors.forename: Werner F
authors.initials: WF
authors.lastname: Blum
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmidt
authors.forename: Thomas
authors.initials: T
authors.lastname: Braulke
authors.forename: Bernd
authors.initials: B
authors.lastname: Kübler
mesh_terms: D000990:Antithrombin III / Q000378:metabolism; D001798:Blood Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D015153:Blotting, Western; D002845:Chromatography; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000378:metabolism; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007700:Kinetics; D013058:Mass Spectrometry; D010958:Plasminogen / Q000737:chemistry* / Q000378:metabolism; D011288:Prekallikrein / Q000378:metabolism; D011485:Protein Binding; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D020349:Surface Plasmon Resonance; D014168:Transferrin / Q000737:chemistry / Q000378:metabolism
chemical_list: D001798:Blood Proteins; C032309:Cohn fraction IV; D003432:Cross-Linking Reagents; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D017527:Receptor, IGF Type 2; D011994:Recombinant Proteins; D014168:Transferrin; D012694:Serine; D007335:Insulin-Like Growth Factor II; D000990:Antithrombin III; D010958:Plasminogen; D011288:Prekallikrein