Wnt-1 has multiple effects on the expression of glutamate transporters.
Central Glia-4 (CG-4) glioma cells exhibit Na(+)-dependent glutamate uptake, and mRNA for each of the GLT, GLAST, and EAAC glutamate transporters was found in the cells by RT-PCR. However, GLT protein in CG-4 cells was not detected by Western blotting. The Wnt-1 oncogene markedly decreased the expression of the mRNAs for GLT and GLAST glutamate transporters in CG-4 glioma cells. This effect of Wnt-1 is in direct contrast to its previously published effects on C6 astrocytoma cells where Wnt-1 induces the expression of GLT, but not protein, and on PC12 pheochromocytoma cells where Wnt-1 induces GLAST. We suggest that these differences in the ability of Wnt-1 to induce or repress GLT and GLAST are due to differences in Wnt-1 dosages or Wnt-1-induced signaling pathways in these cells. The abnormal translation of the GLT RNA in Wnt-1-expressing C6 cells was ascribed to some abnormality in the processing of the GLT transcript. Consistent with this idea is the finding that GLT mRNA was translated in Wnt-1-expressing C6 cells when the GLT mRNA required no splicing before translation occurred.
Jimenez
Amie L
AL
Department of Biological Chemistry, School of Medicine, University of California, 650 Charles Young Drive, Los Angeles 90095, USA.
Chou
Alice H
AH
Khadadadi
Omid
O
Palos
Teresa P
TP
Howard
Bruce D
BD
D027322:Amino Acid Transport System X-AG / Q000096:biosynthesis*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D027342:Excitatory Amino Acid Transporter 2 / Q000096:biosynthesis*; D016716:PC12 Cells; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins
D027322:Amino Acid Transport System X-AG; D018076:DNA, Complementary; D027342:Excitatory Amino Acid Transporter 2; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495245:Wnt1 protein, rat; D029961:Zebrafish Proteins; D001224:Aspartic Acid