Program of the 2004 East Coast Worm Meeting - Caenorhabditis ...

25. Knockout of GLT-3 C. elegans Glutamate Transporter: A Genetic Approach to Study
Excitotoxic Neurodegeneration
Itzhak Mano 1 , Sarah Straud 2 , Monica Driscoll 1
1Mol Biol & Biochem, Rutgers University, Piscataway, NJ
2Mol Biol, University of Texas Southwestern Medical Center, Dallas, TX
In stroke, injury, and several neurodegenerative diseases such as ALS, over-stimulation of
neurons by glutamate (Glu) hyperactivates postsynaptic Glu receptors (GluRs) and triggers a
process of necrotic neuronal death termed excitotoxicity. Malfunction of surface glutamate
transporters (sGluTs), which normally remove glutamate from the synapse, makes critical
contributions to this process. To model sGluT malfunction in an in vivo physiological context and
apply the power of genetics to the study of excitotoxicity we generated sGluT knockout strains in
C. elegans. After establishing that sGluT knockout causes Glu overstimulation, we document the
first definitive case of excitotoxic-like condition in C. elegans. We show that disruption of the
sGluT gene glt-3 acts synergistically with activated GalphaS* signaling to promote
neurodegeneration. We demonstrate that the Glu-dependent effect is mediated through GluRs of
the AMPA subtype and a Type 9 adenylyl cyclase, assigning the latter a novel role in an
excitotoxic-like condition. Our observations suggest that in addition to the other well-appreciated
mechanisms, AMPA receptor-cAMP synergism may be critical to excitotoxicity, a hypothesis with
significant clinical implications.