12. The formation of stable complex between Aß and insulin-degrading enzyme: a possible trans-acting pathway of amyloid self-propagation in the brain.

LOVERA, RE; ALONSO, L; FERNANDEZ-GAMBA,A; DI TULLIO, M; PRAT-GAY, G; MORELLI, L; CASTAÑO, EM

Pinamar, Argentina

Congreso; PABMB 10th Congress, SAIB 41th Annual Meeting and SAN 20th Annual Meeting; 2005

The accumulation of aggregated amyloid b of 40-42 residues in the brain is a major pathogenic mechanism in several neurodegenerative diseases. Insulin degrading enzyme (IDE) is a zinc-metalloendopeptidase that removes brain soluble Ab under physiologic conditions. In the course of our study of Ab-IDE interaction, we found that upon incubation in vitro, in presence or absence of specific inhibitor for IDE, Ab was capable of forming a complex with the enzyme that resisted boiling in 4% SDS-0.1M DTT. Moreover, this component was not dissociated in 8 M urea or 70% formic acid, underscoring its high stability. We further mapped the interaction to the region 16-28 of Ab, by using an N-terminal fluorescein-labeled Ab16-28. We found that complex formation was a very slow process (t1/2~ 45 min) and it was specifically out competed with insulin, another substrate of IDE. These findings suggest that although the formation of stable Ab-IDE complexes may not be dependent on the catalytic mechanism, it requires the interaction of the central region of Ab with the substrate binding site of IDE, or at least a part of it. The full characterization of a non-productive pathway in Ab-IDE interaction and its detection in vivo may provide novel insights about the self-propagation of the amyloidogenic process in the brain. (Alzheimer’s Association IIRG035312, PICT2002-10599)