Trans-inhibition of glutamate transport prevents excitatory amino acid-induced glycolysis in astrocytes.
Previous studies have demonstrated that activation of glutamate transporters promotes glycolysis in astrocytes. Current evidence indicates that compounds such as threo-beta-hydroxyaspartate (THA) are both competitive inhibitors and substrates for glutamate transporters. In this study, we have analyzed the effect of THA on excitatory amino acid (EAA) transport and on EAA-induced glycolysis in mouse primary astrocyte cultures. In agreement with previous studies in rat astrocytes, THA competitively inhibited 3H-D-aspartate (3H-D-Asp) uptake with an IC50 of 319 microM (Ki = 36.6 microM). In contrast, it did not prevent D-aspartate-induced 3H-2-deoxyglucose (2DG) uptake in these conditions. Preexposure of cells to THA for at least 15 min revealed another form of glutamate transport inhibition. This effect was concentration-dependent with an apparent IC50 of 47.7 microM and showed kinetic characteristics consistent with a mechanism of trans-inhibition. Preincubation with THA also inhibited D-aspartate-induced 3H-2DG uptake in a concentration-dependent manner with an apparent IC50 of 59.8 microM. Comparison with other transportable analogues reveals that they share with THA the ability to cause trans-inhibition of glutamate transport and to prevent glutamate-stimulated glycolysis; THA, however, is unique in that it has no effect alone on glucose utilization after preexposure. These data indicate that trans-inhibition of glutamate transport may be a mechanism by which certain glutamate transport inhibitors can prevent the stimulation of aerobic glycolysis by glutamate in astrocytes.
Debernardi
R
R
Institut de Physiologie, CHUV, Faculté de Médecine, Université de Lausanne, Switzerland.
Magistretti
P J
PJ
Pellerin
L
L
D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors*; D027322:Amino Acid Transport System X-AG; D000818:Animals; D000831:Animals, Newborn; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects; D003847:Deoxyglucose / Q000378:metabolism; D018846:Excitatory Amino Acids / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects*; D007700:Kinetics; D051379:Mice; D010766:Phosphorylation; D013237:Stereoisomerism
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D000900:Anti-Bacterial Agents; D018846:Excitatory Amino Acids; C011274:3-hydroxyaspartic acid; D001224:Aspartic Acid; D003847:Deoxyglucose; D005947:Glucose