FRET-Based Calcium Imaging: A Tool for High-Throughput/Content Phenotypic Drug Screening in Alzheimer Disease

Perturbed intracellular store calcium homeostasis is suggested to
play a major role in the pathophysiology of Alzheimer disease (AD).
A number of mechanisms have been suggested to underlie the
impairment of endoplasmic reticulum calcium homeostasis associated
with familial AD-linked presenilin 1 mutations (FAD-PS1). Without
aiming at specifically targeting any of those pathophysiological
mechanisms in particular, we rather performed a high-throughput
phenotypic screen to identify compounds that can reverse the
exaggerated agonist-evoked endoplasmic reticulum calcium release
phenotype in HEK293 cells expressing FAD-PS1. For that purpose, we
developed a fully automated high-throughput calcium imaging assay
using a fluorescence resonance energy transfer-based calcium
indicator at single-cell resolution. This novel robust assay offers
a number of advantages compared with the conventional calcium
measurement screening technologies. The assay was employed in a
large-scale screen with a library of diverse compounds comprising
20,000 low-molecular-weight molecules, which resulted in the
identification of 52 primary hits and 4 lead structures. In a
secondary assay, several hits were found to alter the amyloid (A)
production. In view of the recent failure of AD drug candidates
identified by target-based approaches, such a phenotypic drug
discovery paradigm may present an attractive alternative for the
identification of novel AD therapeutics.