Characterization of a stable complex between inactive insulin-degrading enzyme with Aß peptide.

DE TULIO M; LLOVERA RE; MORELLI L; CASTAÑO EM

Mar del Plata

Congreso; SAIB 43th Annual Meeting; 2007

Sociedad Argentina de Bioquímica y Biología MOlecular

Insulin degrading enzyme (IDE) is central in the turnover of amyloid b (Ab) in the mammalian brain. Biochemical and genetic data support that IDE may play a role in late onset Alzheimer’s disease (AD) by preventing Ab aggregation, one of the characteristically process observed in AD. We have reported that the catalytic domain of natively folded recombinant wild-type IDE (wt-IDE) was capable of forming a stable complex with Ab (IDE-AbCx) that resisted dissociation after treatment with denaturing agents. To study the nature of this interaction independent of degradation, we generated a catalytically inactive IDE mutant IDE-E111Q. Biochemical and biophysical analyses showed that this IDE mutant had identical folding to wt-IDE but lacked proteolytic activity. The kinetic of IDE-AbCx formation showed that although wt-IDE and IDE-E111Q had a similar t1/2 (~ 30 min) the latter exhibited a 5-fold increase in the yield of IDE-AbCx. Isolation by size exclusion chromatography and a time-course analysis by Western blot showed that IDE-AbCx was irreversible under physiological conditions. Moreover, dynamic light scattering and electron microscopy revealed that IDE-E111Q altered the kinetic and morphological characteristics of Ab aggregation by reducing amyloid fibril formation. Our results suggest an unprecedented dead-end interaction between IDE and Ab with implications in the pathogenesis of AD.