The irreversible binding of amyloid peptide substrates to insulin-degrading enzyme: a biological perspective.

Insulin-degrading enzyme (IDE) is a conserved Zn(2+)metalloendopeptidase involved in insulin degradation and in the maintenance of brain steady-state levels of amyloid beta peptide (Abeta) of Alzheimer's disease (AD). Our recent demonstration that IDE and Abeta are capable of forming a stoichiometric and extremely stable complex raises several intriguing possibilities regarding the role of this unique protein-peptide interaction in physiological and pathological conditions. These include a protective cellular function of IDE as a "dead-end chaperone" alternative to its proteolytic activity and the potential impact of the irreversible binding of Abeta to IDE upon its role as a varicella zoster virus receptor. In a pathological context, the implications for insulin signaling and its relationship to AD pathogenesis are discussed. Moreover, our findings warrant further research regarding a possible general and novel interaction between amyloidogenic peptides and other Zn(2+)metallopeptidases with an IDE-like fold and a substrate conformation-dependent recognition mechanism.