IGF-BP3 Human Active Protein

This gene is a member of the insulin-like growth factor binding protein (IGFBP) family and encodes a protein with an IGFBP domain and a thyroglobulin type-I domain. The protein forms a ternary complex with insulin-like growth factor acid-labile subunit (IGFALS) and either insulin-like growth factor (IGF) I or II. In this form, it circulates in the plasma, prolonging the half-life of IGFs and altering their interaction with cell surface receptors. Alternate transcriptional splice variants, encoding different isoforms, have been characterized. [provided by RefSeq, Jul 2008]

Function: IGF-binding proteins prolong the half-life of the IGFs and have been shown to either inhibit or stimulate the growth promoting effects of the IGFs on cell culture. They alter the interaction of IGFs with their cell surface receptors. Also exhibits IGF-independent antiproliferative and apoptotic effects mediated by its receptor TMEM219/IGFBP-3R. Ref.17

Subunit structure: Interacts with XLKD1

By similarity. Binds IGF2 more than IGF1. Forms a ternary complex of about 140 to 150 kDa with IGF1 or IGF2 and a 85 kDa glycoprotein (ALS). Interacts with HN. Interacts with TMEM219. Ref.10 Ref.12 Ref.17

Subcellular location: Secreted Ref.17.

Tissue specificity: Expressed by most tissues. Present in plasma.

Developmental stage: IGFBP3 levels are higher during extrauterine life and peak during puberty.

Induction: Up-regulated in the presence of IGF1, insulin and other growth-stimulating factors such as growth hormone, EGF and phorbol esters.

Domain: The thyroglobulin type-1 domain mediates interaction with HN.

Post-translational modification: Phosphorylation sites are present in the extracellular medium.

Sequence similarities: Contains 1 IGFBP N-terminal domain.Contains 1 thyroglobulin type-1 domain.