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Interaction of insulin-like growth factor binding protein-3 with latent transforming growth factor-beta binding
1Department of Physiology, University of Manitoba, Bannatyne Campus, Winnipeg, Canada.
Abstract:
Insulin-like growth factor binding protein-3 (IGFBP-3) inhibits the replication and promotes apoptosis in various cell lines in an IGF-independent manner. We utilized a yeast two-hybrid system to identify binding partners for IGFBP-3 in a mouse embryo cDNA library. A partial cDNA encoding mouse latent transforming growth factor beta (TGF-beta) binding protein-1 (LTBP-1) was identified. This cDNA encoded a mouse LTBP-1 mRNA fragment corresponding to amino acid residues 1160-1712. Analysis of C-terminal deleted mutants indicated that the IGFBP-3 interacting domain resides in the 552 residue C-terminal fragment encoding amino acids 831-1383. The interaction of IGFBP-3 with recombinant human LTBP-1 immobilized on nitrocellulose was also demonstrated. Neither binding of IGF-1 to IGFBP-3 nor binding of latency associated protein (LAP) with LTBP-1 inhibited the interaction of IGFBP-3 with LTBP-1. Furthermore the large latent complex, 125I-TGF-beta/LAP/LTBP-1 was able to bind to immobilized IGFBP-3. These data demonstrate that IGFBP-3 can bind to LTBP-1 and provide a potential mechanism whereby IGFBP-3 can interact with the TGF-beta system.
Insights
Insulin-like growth factor binding protein-3 (IGFBP-3) binds to latent transforming growth factor beta binding protein-1 (LTBP-1). This interaction suggests IGFBP-3 influences the transforming growth factor beta (TGF-beta) system.
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Insulin-like growth factor binding protein-3 (IGFBP-3) exhibits IGF-independent inhibition of cell replication and promotion of apoptosis.
- The interaction partners and mechanisms of IGFBP-3 are not fully elucidated.
Purpose of the Study:
- To identify binding partners of IGFBP-3 using a yeast two-hybrid system.
- To investigate the interaction between IGFBP-3 and latent transforming growth factor beta binding protein-1 (LTBP-1).
Main Methods:
- Yeast two-hybrid screening of a mouse embryo cDNA library.
- Analysis of C-terminal deletion mutants to map the IGFBP-3 binding domain on LTBP-1.
- Immobilization assays using recombinant human LTBP-1 and 125I-labeled TGF-beta/LAP/LTBP-1 complex.
Main Results:
- A partial cDNA encoding mouse LTBP-1 was identified as an IGFBP-3 binding partner.
- The C-terminal fragment of LTBP-1 (residues 831-1383) contains the IGFBP-3 interacting domain.
- IGFBP-3 binds to LTBP-1 independently of IGF-1/IGFBP-3 and LAP/LTBP-1 interactions.
- The large latent complex of TGF-beta (125I-TGF-beta/LAP/LTBP-1) binds to IGFBP-3.
Conclusions:
- IGFBP-3 directly binds to LTBP-1.
- This interaction provides a potential molecular mechanism for IGFBP-3 to modulate the TGF-beta signaling pathway.