TY - JOUR
T1 - Neuronal regulation of glutamate transporter subtype expression in astrocytes
AU - Swanson, Raymond A.
AU - Liu, Jialing
AU - Miller, Johann W.
AU - Rothstein, Jeffrey D.
AU - Farrell, Kevin
AU - Stein, Becky A.
AU - Longuemare, Maria C.
PY - 1997
Y1 - 1997
N2 - GLT-1, GLAST, and EAAC1 are high-affinity, Na+-dependent glutamate transporters identified in rat forebrain. The expression of these transporter subtypes was characterized in three preparations: undifferentiated rat cortical astrocyte cultures, astrocytes cocultured with cortical neurons, and astrocyte cultures differentiated with dibutyryl cyclic AMP (dBcAMP). The undifferentiated astrocyte monocultures expressed only the GLAST subtype. Astrocytes cocultured with neurons developed a stellate morphology and expressed both GLAST and GLT-1; neurons expressed only the EAAC1 transporter, and rare microglia in these cultures expressed GLT-1. Treatment of astrocyte cultures with dBcAMP induced expression of GLT-1 and increased expression of GLAST. These effects of dBcAMP on transporter expression were qualitatively similar to those resulting from coculture with neurons, but immunocytochemistry showed the pattern of transporter expression to be more complex in the coculture preparations. Compared with astrocytes expressing only GLAST, the dBcAMP-treated cultures expressing both GLAST and GLT-1 showed an increase in glutamate uptake V(max), but no change in the glutamate K(m) and no increased sensitivity to inhibition by dihydrokainate. Pyrrolidine-2,4-dicarboxylic acid and threo-β-hydroxyaspartic acid caused relatively less inhibition of transport in cultures expressing both GLAST and GLT-1, suggesting a weaker effect at GLT-1 than at GLAST. These studies show that astrocyte expression of glutamate transporter subtypes is influenced by neurons, and that dBcAMP can partially mimic this influence. Manipulation of transporter expression in astrocyte cultures may permit identification of factors regulating the expression and function of GLAST and GLT-1 in their native cell type.
AB - GLT-1, GLAST, and EAAC1 are high-affinity, Na+-dependent glutamate transporters identified in rat forebrain. The expression of these transporter subtypes was characterized in three preparations: undifferentiated rat cortical astrocyte cultures, astrocytes cocultured with cortical neurons, and astrocyte cultures differentiated with dibutyryl cyclic AMP (dBcAMP). The undifferentiated astrocyte monocultures expressed only the GLAST subtype. Astrocytes cocultured with neurons developed a stellate morphology and expressed both GLAST and GLT-1; neurons expressed only the EAAC1 transporter, and rare microglia in these cultures expressed GLT-1. Treatment of astrocyte cultures with dBcAMP induced expression of GLT-1 and increased expression of GLAST. These effects of dBcAMP on transporter expression were qualitatively similar to those resulting from coculture with neurons, but immunocytochemistry showed the pattern of transporter expression to be more complex in the coculture preparations. Compared with astrocytes expressing only GLAST, the dBcAMP-treated cultures expressing both GLAST and GLT-1 showed an increase in glutamate uptake V(max), but no change in the glutamate K(m) and no increased sensitivity to inhibition by dihydrokainate. Pyrrolidine-2,4-dicarboxylic acid and threo-β-hydroxyaspartic acid caused relatively less inhibition of transport in cultures expressing both GLAST and GLT-1, suggesting a weaker effect at GLT-1 than at GLAST. These studies show that astrocyte expression of glutamate transporter subtypes is influenced by neurons, and that dBcAMP can partially mimic this influence. Manipulation of transporter expression in astrocyte cultures may permit identification of factors regulating the expression and function of GLAST and GLT-1 in their native cell type.
KW - GLAST
KW - GLT-1
KW - PDC
KW - dibutyryl cAMP
KW - dihydrokainate
KW - glutamate uptake
KW - microglia
KW - pyrrolidine-2,4-dicarboxylate
KW - threo-β-hydroxyaspartate
UR - http://www.scopus.com/inward/record.url?scp=0031020015&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031020015&partnerID=8YFLogxK
U2 - 10.1523/jneurosci.17-03-00932.1997
DO - 10.1523/jneurosci.17-03-00932.1997
M3 - Article
C2 - 8994048
AN - SCOPUS:0031020015
SN - 0270-6474
VL - 17
SP - 932
EP - 940
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 3
ER -