Biochemical and functional analysis of a conserved IGF-binding protein isolated from rainbow trout (Oncorhynchus mykiss) hepatoma cells.
Rainbow trout (Oncorhynchus mykiss) serum contains several IGF-binding proteins (IGFBPs) that specifically bind to IGFs. The structures of these fish IGFBPs have not been determined and their physiological functions are poorly defined. In this study, we identified a 30 kDa IGFBP present in rainbow trout serum and secreted by cultured trout hepatoma cells. This IGFBP binds to IGFs but not to insulin. This IGFBP was purified to homogeneity using a three-step procedure involving Phenyl-Sepharose chromatography, IGF-I affinity chromatography and reverse-phase HPLC. Affinity cross-linking studies indicated that this IGFBP binds to IGF-I with a higher affinity than to IGF-II. N-terminal sequence analysis of the trout IGFBP suggests that it shares high sequence identity with that of human IGFBP-1 in the N-terminal region. When added to cultured fish and human cells, the trout IGFBP inhibited IGF-I-stimulated DNA synthesis and cell proliferation in a concentration-dependent manner. The inhibitory effect of the fish IGFBP was comparable to those of human IGFBP-1 and -4. These results indicate that the IGFBP molecule is structurally and functionally conserved in evolutionarily ancient vertebrate species such as bony fish.
Bauchat
J R
JR
Department of Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.
Busby
W H
WH
Garmong
A
A
Swanson
P
P
Moore
J
J
Lin
M
M
Duan
C
C
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002846:Chromatography, Affinity; D002847:Chromatography, Agarose; D002851:Chromatography, High Pressure Liquid; D017124:Conserved Sequence; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II