Crystal structure of human insulin degrading enzyme in complex with insulin-like growth factor II
[IGF2_HUMAN] Epigenetic changes of DNA hypomethylation in IGF2 are a cause of Silver-Russell syndrome (SRS) [MIM:180860]. A clinically heterogeneous condition characterized by severe intrauterine growth retardation, poor postnatal growth, craniofacial features such as a triangular shaped face and a broad forehead, body asymmetry, and a variety of minor malformations. The phenotypic expression changes during childhood and adolescence, with the facial features and asymmetry usually becoming more subtle with age.
[IGF2_HUMAN] The insulin-like growth factors possess growth-promoting activity. In vitro, they are potent mitogens for cultured cells. IGF-II is influenced by placental lactogen and may play a role in fetal development. Preptin undergoes glucose-mediated co-secretion with insulin, and acts as physiological amplifier of glucose-mediated insulin secretion. Exhibits osteogenic properties by increasing osteoblast mitogenic activity through phosphoactivation of MAPK1 and MAPK3.
Publication Abstract from PubMed
Insulin-degrading enzyme (IDE) is involved in the clearance of many bioactive peptide substrates, including insulin and amyloid-beta, peptides vital to the development of diabetes and Alzheimer's disease, respectively. IDE can also rapidly degrade hormones that are held together by intramolecular disulfide bond(s) without their reduction. Furthermore, IDE exhibits a remarkable ability to preferentially degrade structurally similar peptides such as the selective degradation of insulin-like growth factor (IGF)-II and transforming growth factor-alpha (TGF-alpha) over IGF-I and epidermal growth factor, respectively. Here, we used high-accuracy mass spectrometry to identify the cleavage sites of human IGF-II, TGF-alpha, amylin, reduced amylin, and amyloid-beta by human IDE. We also determined the structures of human IDE-IGF-II and IDE-TGF-alpha at 2.3 A and IDE-amylin at 2.9 A. We found that IDE cleaves its substrates at multiple sites in a biased stochastic manner. Furthermore, the presence of a disulfide bond in amylin allows IDE to cut at an additional site in the middle of the peptide (amino acids 18-19). Our amylin-bound IDE structure offers insight into how the structural constraint from a disulfide bond in amylin can alter IDE cleavage sites. Together with NMR structures of amylin and the IGF and epidermal growth factor families, our work also reveals the structural basis of how the high dipole moment of substrates complements the charge distribution of the IDE catalytic chamber for the substrate selectivity. In addition, we show how the ability of substrates to properly anchor their N-terminus to the exosite of IDE and undergo a conformational switch upon binding to the catalytic chamber of IDE can also contribute to the selective degradation of structurally related growth factors.
Molecular basis for the recognition and cleavages of IGF-II, TGF-alpha, and amylin by human insulin-degrading enzyme.,Guo Q, Manolopoulou M, Bian Y, Schilling AB, Tang WJ J Mol Biol. 2010 Jan 15;395(2):430-43. Epub 2009 Nov 5. PMID:19896952
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.