Pertussis toxin-sensitive modulation of glutamate transport by endothelin-1 type A receptors in glioma cells.
Endothelin-1 (ET-1) is a 21 amino acids peptide that exerts several biological activities through interaction with specific G-protein coupled receptors. Increased ET-1 expression is frequently associated with pathological situations involving alterations in glutamate levels. In the present study, a brief exposure to ET-1 was found to increase aspartate uptake in C6 glioma cells, which endogenously express the neuronal glutamate transporter EAAC1 (pEC50 of 9.89). The stimulatory effect of ET-1 mediated by ETA receptors corresponds to a 62% increase in the Vmax with no modification of the affinity for the substrate. While protein kinase C activity is known to participate in the regulation of EAAC1, the effect of ET-1 on the glutamate uptake was found to be independent of this kinase activation. In contrast, the inactivation of Go/i type G-protein dependent signaling with pertussis toxin was found to impair ET-1-mediated regulation of EAAC1. An examination of the cell surface expression of EAAC1 by protein biotinylation studies or by confocal analysis of immuno-fluorescence staining demonstrated that ET-1 stimulates EAAC1 translocation to the cell surface. Hence, the disruption of the cytoskeleton with cytochalasin D prevented ET-1-stimulated aspartate uptake. Together, the data presented in the current study suggest that ET-1 participates in the acute regulation of glutamate transport in glioma cells. Considering the documented role of glutamate excitotoxicity in the development of brain tumors, endothelinergic system constitutes a putative target for the pharmacological control of glutamate transmission at the vicinity of glioma cells.
Najimi
Mustapha
M
Laboratoire de Pharmacologie Expérimentale, Université Catholique de Louvain, 54.10, Avenue Hippocrate 54, 1200 Bruxelles, Belgium. mustapha.najimi@farl.ucl.ac.be
Maloteaux
Jean-Marie
JM
Hermans
Emmanuel
E
D027322:Amino Acid Transport System X-AG / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D019332:Endothelin-1 / Q000494:pharmacology*; D050580:Excitatory Amino Acid Transporter 3; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology*; D051381:Rats; D044022:Receptor, Endothelin A / Q000378:metabolism*; D027981:Symporters / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D027322:Amino Acid Transport System X-AG; D019332:Endothelin-1; D050580:Excitatory Amino Acid Transporter 3; D050491:Glutamate Plasma Membrane Transport Proteins; D044022:Receptor, Endothelin A; C493398:Slc1a1 protein, rat; D027981:Symporters; D018698:Glutamic Acid; D037342:Pertussis Toxin