ENT1 regulates ethanol-sensitive EAAT2 expression and function in astrocytes.
BACKGROUND
Equilibrative nucleoside transporter 1 (ENT1) and excitatory amino acid transporter 2 (EAAT2) are predominantly expressed in astrocytes where they are thought to regulate synaptic adenosine and glutamate levels. Because mice lacking ENT1 display increased glutamate levels in the ventral striatum, we investigated whether ENT1 regulates the expression and function of EAAT2 in astrocytes, which could contribute to altered glutamate levels in the striatum.


METHODS
We examined the effect of ENT1 inhibition and overexpression on the expression of EAAT2 using quantitative real-time PCR and measured glutamate uptake activity in cultured astrocytes. We also examined the effect of 0 to 200 mM ethanol doses for 0 to 24 hours of ethanol exposure on EAAT2 expression and glutamate uptake activity. We further examined the effect of ENT1 knockdown by a specific siRNA on ethanol-induced EAAT2 expression.


RESULTS
An ENT1-specific antagonist and siRNA treatments significantly reduced both EAAT2 expression and glutamate uptake activity while ENT1 overexpression up-regulated EAAT2 mRNA expression. Interestingly, 100 or 200 mM ethanol exposure increased EAAT2 mRNA expression as well as glutamate uptake activity. Moreover, we found that ENT1 knockdown inhibited the ethanol-induced EAAT2 up-regulation.


CONCLUSIONS
Our results suggest that ENT1 regulates glutamate uptake activity by altering EAAT2 expression and function, which might be implicated in ethanol intoxication and preference.
Wu
Jinhua
J
Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Lee
Moonnoh R
MR
Choi
Sun
S
Kim
Taehyun
T
Choi
Doo-Sup
DS
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D002460:Cell Line; D002492:Central Nervous System Depressants / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D033721:Equilibrative Nucleoside Transporter 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D051379:Mice; D034741:RNA, Small Interfering / Q000494:pharmacology; D013868:Thioinosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors
D002492:Central Nervous System Depressants; D033721:Equilibrative Nucleoside Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D034741:RNA, Small Interfering; C498476:SLC29A1 protein, mouse; C493396:Slc1a2 protein, mouse; D013873:Thionucleotides; D000431:Ethanol; D018698:Glutamic Acid; D013868:Thioinosine; C028318:nitrobenzylthioinosine 5'-monophosphate