Characterization and distribution of the neuronal glutamate transporter eaac1 in rat brain. Velaz-Faircloth, Maria, Tanya S. McGraw, Marc S. Malandro, Robert T. Fremeau, Jr, Michael S. Kilberg And, Kevin J. Anderson. Departments of Pharmacology and Neurobiology, Duke University, Durham, NC; Departments of Neuroscience, Biochemistry & Molecular Biology and Physiological Sciences, University of Florida, Gainesville, FL, USA
APStracts 2:0265C, 1995.
The extracellular concentration of glutamate and other related excitatory amino acids is regulated by the action of transporter proteins located either on presynaptic terminals or adjacent astroglial processes. Recent molecular advances have led to the cloning of three separate cDNAs encoding for sodium-dependent glutamate transporters; two are thought to be primarily glial in origin (GLAST and GLT-1), while the third (EAAC1) is localized to neurons in the brain as well as other non-neural tissues. An EAAC1 cDNA was initially cloned from rabbit small intestine (13); in this study, we report isolation and characterization of the homologous clone from rat brain. Northern blot hybridization revealed high levels of EAAC1 mRNA in rat brain and kidney and low levels in heart, lung and skeletal muscle. Transient expression of EAAC1 in HeLa cells resulted in an increase in Na+-dependent high affinity L -[3H]glutamate and D-[3H]aspartate transport. The pharmacological profile of EAAC1 was very similar to that reported for the rabbit and human EAAC1 homologs. Transport activity was potently inhibited by D- and L-threo-b-hydroxyaspartate and L-trans-pyrrolodine-2,4 -dicarboxylate. Dihydrokainate and L-a-aminoadipate did not inhibit transport at concentrations below 1 mM. Oligonucleotide cDNA probes (45 mer) were constructed and labeled with [35S]ATP for film and emulsion-based in situ hybridization of rat brain. EAAC1 mRNA had the highest density in the cerebellar granule cell layer, hippocampus, superior colliculus and neocortex. Sections that were emulsion-dipped and counter-stained with cresyl violet revealed EAAC1 labeling localized exclusively over neuronal cell bodies, including some non -glutamatergic neurons such as spinal cord ventral horn cells. 

Received 6 March 1995; accepted in final form 3 July 1995.
APS Manuscript Number C128-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.