Identification of vitronectin as a novel insulin-like growth factor-II binding protein.
We have previously reported the presence of a 70 kDa insulin-like growth factor (IGF)-II-specific binding protein in chicken serum using Western ligand blotting approaches. In order to ascertain the identity of this 70 kDa IGF-II binding species, the protein has been purified from chicken serum using a combination of ion-exchange and gel-permeation chromatography. Interestingly, amino acid sequencing of the purified protein revealed that it has the same N-terminal sequence as chicken vitronectin (VN). The protein has the ability to specifically bind IGF-II and not IGF-I as determined by ligand blotting, cross-linking and competitive binding assay approaches. In addition, the protein binds 125I-des(1-6)-IGF-II, suggesting that the interaction with IGF-II is different to those with other characterized IGF-binding proteins. Importantly, we have ascertained that both human and bovine VN also specifically bind IGF-II. These results are particularly relevant in the light of the recent report that the urokinase-type plasminogen activator receptor, a protein that also binds VN, has been shown to associate with the cation-independent mannose-6-phosphate/IGF-II receptor and suggest a possible role for IGF-II in cell adhesion and invasion.
Upton
Z
Z
Cooperative Research Centre for Tissue Growth and Repair and CSIRO Human Nutrition, Adelaide BC, SA, Australia. zee.upton@flinders.edu.au
Webb
H
H
Hale
K
K
Yandell
C A
CA
McMurtry
J P
JP
Francis
G L
GL
Ballard
F J
FJ
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002645:Chickens; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D019096:Vitronectin / Q000378:metabolism*
D018969:Insulin-Like Growth Factor Binding Proteins; D019096:Vitronectin; D007335:Insulin-Like Growth Factor II