Chapter 44 - Alzheimer’s Dementia Drug Discovery: Targeting Synaptic Glutamate Uptake

Abstract

According to the hypothesis, amyloid Alzheimer's dementia (AD) begins in the brain with Aβ peptides accumulation and amyloid formation. However, all clinical trials targeting Aβ peptides and brain amyloid have failed to help anybody living with AD. Instead of repeating similar trial failures, we need to discover new drug targets if we want to prevent, delay, and cure dementia. In the brain, glutamate is the synaptic signaling molecule of neurons. As soon as the glutamate signaling starts it is stopped in 0.1–2ms by astrocytes, which take up and clear glutamate from synapses. This prevents glutamate neurotoxicity causing synapse loss and neuron cell death. Astrocytes express excitatory amino acid transporter-2 (EAAT2), the major glutamate transporter, and 1% of brain protein. In AD, astrocytes are impaired in synaptic glutamate uptake. In experimental mouse models of AD, increasing EAAT2 expression slows dementia progression. Here, I describe a simple assay to discover drugs that activate EAAT2. The assay directly targets the EAAT2 protein reconstituted in liposomes and measures glutamate uptake with Oxonol VI red fluorescent dye. Importantly, the assay should limit “off-targeting” of drugs and adverse events, which remain the main problems in AD drug discovery and clinical development. For efficacy, specificity, and safety, EAAT2-activating drugs are studied in experimental Caenorhabditis elegans models of AD and neurodegenerative diseases.