Effects of 18-kDa translocator protein knockdown on gene expression of glutamate receptors, transporters, and metabolism, and on cell viability affected by glutamate.
OBJECTIVE
Previously, several important roles for glutamate have been described for the biology of primary brain tumors. For example, glutamate has been suggested to promote glioma cell proliferation by the activation of the 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid (AMPA) subtype of glutamate receptors. In the present study, we determined the potential regulatory roles of the 18-kDa translocator protein (TSPO) in the glutamatergic system in relation to cell death of brain tumor cells through knockdown of the TSPO by genetic manipulation.


METHODS
With microarray analysis and validation of gene expression of particular genes using real-time PCR, we found effects because of small inhibitory RNA knockdown of the TSPO in human U118MG glioblastoma cells on gene expression of glutamate receptors, glutamate transporters, and enzymes for glutamate metabolism. We also applied antisense RNA to silence TSPO in rat C6 glioblastoma cells and assayed the effects on DNA fragmentation, indicative of apoptosis, because of glutamate exposure.


RESULTS
In particular, the effects of TSPO silencing in human U118MG cells related to glutamate metabolism indicate a net effect of a reduction in glutamate levels, which may potentially protect the cells in question from cell death. The TSPO knockdown in C6 cells showed that TSPO is required for the induction of apoptosis because of glutamate exposure.


CONCLUSIONS
These findings show that interactions between the TSPO and the glutamatergic system may play a role in tumor development of glioblastoma cells. This may also have implications for our understanding of the involvement of the TSPO in secondary brain damage and neurodegenerative diseases.
Department of Molecular Pharmacology, Technion-Israel Institute of Technology, Faculty of Medicine, Haifa, Israel.
Leo
L
Veenman
Julia
J
Bode
Michal
M
Gaitner
Beatriz
B
Caballero
Yelena
Y
Peʼer
Sivan
S
Zeno
Silke
S
Kietz
Wilfried
W
Kugler
Max
M
Lakomek
Moshe
M
Gavish
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001932:Brain Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D055785:Gene Knockdown Techniques; D005909:Glioblastoma; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D034741:RNA, Small Interfering; D051381:Rats; D018079:Receptors, GABA / Q000235:genetics / Q000378:metabolism; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism
D034741:RNA, Small Interfering; D018079:Receptors, GABA; D017470:Receptors, Glutamate; C499229:TSPO protein, human; D018698:Glutamic Acid