Skip Header

You are using a version of browser that may not display all the features of this website. Please consider upgrading your browser.

Characterization of the insulin inhibition of the peptidolytic activities of the insulin-degrading enzyme-proteasome complex.

Bennett R.G., Hamel F.G., Duckworth W.C.

Insulin-degrading enzyme (IDE) is a component of a cytosolic complex that includes multicatalytic proteinase (MCP), the major cytoplasmic proteolytic activity. Insulin, the primary substrate for IDE, inhibits the proteolytic activity of the IDE-MCP complex but not of purified MCP. This provides a regulatory role for IDE in cellular proteolysis and a potential mechanism for intracellular insulin action. To examine the specificity and to explore the mechanisms for the IDE-MCP interaction, we studied the functional interaction of a variety of peptides with the complex. Atrial natriuretic peptide (ANP), relaxin, glucagon, proinsulin, and insulin-like growth factor II (IGF-II) bind to and are degraded by IDE. These peptides have significant inhibitory effects on the chymotrypsin-like and trypsin-like MCP catalytic activities but not the peptidyl-glutamyl hydrolyzing activity. A panel of peptides that are not ligands of IDE had no effect. To explore the potential mechanism for the IDE control of MCP activity, dose response curves for insulin-like growth factor I (IGF-I) and IGF-II effects on MCP chymotrypsin-like activity were determined. IGF-II, which (similar to insulin) is a good substrate for IDE, had a substantial inhibitory effect, whereas IGF-I, which is bound but poorly degraded, had little inhibitory activity on MCP. Proinsulin, another ligand of IDE that is tightly bound but poorly degraded, had a partial effect on MCP activity, but inhibited the full insulin effect. These data suggest a requirement for both the binding and degradation of IDE ligands for the full inhibition of MCP. Insulin-sized degradation products, substrates of IDE, also inhibited MCP activity. Further examination of the insulin effect on MCP included kinetic studies. Insulin produced a noncompetitive inhibition of both the chymotrypsin-like and trypsin-like activities of MCP. These data suggest that the insulin-IDE effect on MCP is due to conformational changes in the IDE-MCP complex and provide an intracellular mechanism of action for insulin.

Diabetes 46:197-203(1997) [PubMed] [Europe PMC]

We'd like to inform you that we have updated our Privacy Notice to comply with Europe’s new General Data Protection Regulation (GDPR) that applies since 25 May 2018.

Do not show this banner again
UniProt is an ELIXIR core data resource
Main funding by: National Institutes of Health