Type Ialpha collagen is an IGFBP-3 binding protein.
Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) possesses both growth-inhibitory and -potentiating effects on cells, which are independent of IGF action and mediated through specific IGFBP-3 binding proteins/receptors located at the cell membrane, cytosol, or nuclear compartments as well as in the extracellular matrix. We here characterized type Ialpha collagen as one of these IGFBP-3 binding proteins. Human serum was fractionated over an IGFBP-3 affinity column, and bands at 70-100 kDa were eluted as IGFBP-3 ligands. The 100-kDa band was extracted, subjected to N-terminal amino acid sequencing, and identified through database searching as the N-terminal chain of type Ialpha collagen protein. In a separate screening approach, using a yeast two-hybrid system, we cloned the type Ialpha collagen cDNA from a human liver cDNA library as an IGFBP-3 protein partner. Anti-IGFBP-3 antibodies co-immunoprecipitated type Ialpha collagen and IGFBP-3 from the conditioned media of human fibroblasts and vice versa. We demonstrated through ligand dot blot analysis that type Ialpha collagen binds IGFBP-3. IGFBP-3 mutants, with altered sequence at the nuclear localization sequence, bound type Ialpha collagen poorly. Western immunoblot showed that type Ialpha collagen binds only IGFBP-3 but not IGF-I, suggesting an IGF-I-independent mechanism of this interaction. Physiological effects of IGFBP-3-collagen interactions may include modulation of cell adhesion and migration.
David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
Bingrong
B
Liu
Stuart A
SA
Weinzimer
Tara Beers
TB
Gibson
Desmond
D
Mascarenhas
Pinchas
P
Cohen
D001665:Binding Sites; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009154:Mutation; D019913:Nuclear Localization Signals; D011233:Precipitin Tests; D011485:Protein Binding; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000235:genetics
D024042:Collagen Type I; D018972:Insulin-Like Growth Factor Binding Protein 3; D019913:Nuclear Localization Signals; D007334:Insulin-Like Growth Factor I