title: Insulin-like growth factor binding proteins 4-6.
abstract: Insulin-like growth factor binding proteins (IGFBPs) 4-6 have important roles as modulators of IGF actions. IGFBP-4 and IGFBP-6 predominantly inhibit IGF actions, whereas IGFBP-5 may enhance these actions under some circumstances. IGFBP-6 is unique among the IGFBPs for its marked IGF-II binding preference. IGFBPs 4-6 are found in the circulation as binary complexes with IGFs that can enter tissues. Additionally, about half of the circulating IGFBP-5 is found in ternary complexes with IGFs and an acid labile subunit; this high molecular complex cannot leave the circulation and acts as an IGF reservoir. IGFBPs 4-6 also have IGF-independent actions. These IGFBPs are regulated in a cell-specific manner and their dysregulation may play a role in a range of diseases including cancer. However, there is no clear clinical indication for measuring serum levels of these IGFBPs at present.
authors.affiliation: Department of Medicine (Alfred), Monash University, Prahran, 3181, Australia; Department of Endocrinology and Diabetes, Alfred Hospital, Melbourne, 3004, Australia. Electronic address: leon.bach@monash.edu.
authors.forename: Leon A
authors.initials: LA
authors.lastname: Bach
mesh_terms: D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood / Q000378:metabolism*; D015398:Signal Transduction; D013002:Somatomedins / Q000378:metabolism
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins
keywords: binding protein; cellular action; insulin-like growth factor; protein structure; regulation