P4‐225: Therapeutic action of translation blockers on expression of the amyloid precursor protein as a central ferroxidase

Abstract

It is possible to repress amyloid precursor protein (APP) mRNA translation as both an anti-amyloid pharmacotherapy for Alzheimer's disease (AD) and also to tone oxidative ferroxidase activity from APP over-expression.This therapeutic model is consistent with cases where AD pathology is the genetic consequence of duplications of the APP gene. Our pharmacological goal is to reduce APP expression. The antioxidant N-acetyl cysteine selectively reduced APP translation in neural cells while maintaining compensatory APLP-1 /-2 levels, then this drug also limited Aβ production in vivo.Secondly, posiphen is the + enantiomer of the well-tested anti-cholinesterase phenserine, which entered phase II clinical trials for its capacity to limit amyloid in AD subjects via its action as an APP 5'UTR translation blocker. We screened two molecular compound libraries at Harvard and Columbia Universities. From our screens, thirteen top leads shared chemical features pertinent to potently blocking APP 5'UTR directed translation (1nM). Most of our lead APP translation blockers were found to be highly potent intercalators of the RNA stem loop folded from APP 5'untranslated region. All were planar and had either a benzimidazole, benzothiazole or benzoxazole ring in its backbone. Top APP 5'UTR inhibitors were 50-fold more potent blockers of Aβ precursor translation than NAC or posiphen. The most active lead was the ninth compound in the series, APP blocker-9 (“JTR-009”). Critically, JTR-009 effectively reduced APP levels in primary mouse E-18 cortical neurons at single nanomolar concentrations similar to serum concentrations of effective clinical drugs. JTR-009 was anti-amyloid and our calcein assays demonstrated it adjusted cellular iron content to promote cellular viability. Our top APP translation blocker, JTR-009, is a planar tricyclic benzimidazole that intercalates selectively into the single 146 base APP 5'UTR specific RNA stem loop. Confirming specificity and potency, we are checking how JTR-009 blocks ribosome scanning of the APP 5'UTR to impede translation (Aβ output) while not interacting with the 5'UTRs of APP-like protein (APLP-1/-2) mRNAs. This APP translation blocker adjusted the intrinsic levels of APP with its concomitant ferroxidase activity and iron export properties, thus to optimally promote neural cell viability.