RT Journal Article
SR Electronic
T1 Expression of a Variant Form of the Glutamate Transporter GLT1 in Neuronal Cultures and in Neurons and Astrocytes in the Rat Brain
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2142
OP 2152
DO 10.1523/JNEUROSCI.22-06-02142.2002
VO 22
IS 6
A1 Weizhi Chen
A1 Chiye Aoki
A1 Veeravan Mahadomrongkul
A1 Christian E. Gruber
A1 Guang Jian Wang
A1 Rachel Blitzblau
A1 Nina Irwin
A1 Paul A. Rosenberg
YR 2002
UL http://www.jneurosci.org/content/22/6/2142.abstract
AB To identify glutamate transporters expressed in forebrain neurons, we prepared a cDNA library from rat forebrain neuronal cultures, previously shown to transport glutamate with high affinity and capacity. Using this library, we cloned two forms, varying in the C terminus, of the glutamate transporter GLT1. This transporter was previously found to be localized exclusively in astrocytes in the normal mature brain. Specific antibodies against the C-terminal peptides were used to show that forebrain neurons in culture express both GLT1a and GLT1b proteins. The pharmacological properties of glutamate transport mediated by GLT1a and GLT1b expressed in COS-7 cells and in neuronal cultures were indistinguishable. Both GLT1a and GLT1b were upregulated in astrocyte cultures by exposure to dibutyryl cAMP. We next investigated the expression of GLT1bin vivo. Northern blot analysis of forebrain RNA revealed two transcripts of ∼3 and 11 kb that became more plentiful with developmental age. Immunoblot analysis showed high levels of expression in the cortex, hippocampus, striatum, thalamus, and midbrain. Pre-embedding electron microscopic immunocytochemistry with silver-enhanced immunogold detection was used to localize GLT1bin vivo. In the rat somatosensory cortex, GLT1b was clearly expressed in neurons in presynaptic terminals and dendritic shafts, as well as in astrocytes. The presence of GLT1b in neurons may offer a partial explanation for the observed uptake of glutamate by presynaptic terminals, for the preservation of input specificity at excitatory synapses, and may play a role in the pathophysiology of excitotoxicity.