title: Role of the intracellular nucleoside transporter ENT3 in transmitter and high K+ stimulation of astrocytic ATP release investigated using siRNA against ENT3.
abstract: This study investigates the role of the intracellular adenosine transporter equilibrative nucleoside transporter 3 (ENT3) in stimulated release of the gliotransmitter adenosine triphosphate (ATP) from astrocytes. Within the past 20 years, our understanding of the importance of astrocytic handling of adenosine, its phosphorylation to ATP, and release of astrocytic ATP as an important transmitter has become greatly expanded. A recent demonstration that the mainly intracellular nucleoside transporter ENT3 shows much higher expression in freshly isolated astrocytes than in a corresponding neuronal preparation leads to the suggestion that it was important for the synthesis of gliotransmitter ATP from adenosine. This would be consistent with a previously noted delay in transmitter release of ATP in astrocytes but not in neurons. The present study has confirmed and quantitated stimulated ATP release in response to glutamate, adenosine, or an elevated K(+) concentration from well-differentiated astrocyte cultures, measured by a luciferin-luciferase reaction. It showed that the stimulated ATP release was abolished by downregulation of ENT3 with small interfering RNA (siRNA), regardless of the stimulus. The concept that transmitter ATP in mature astrocytes is synthesized directly from adenosine prior to release is supported by the postnatal development of the expression of the vesicular transporter SLC17A9 in astrocytes. In neurons, this transporter carries ATP into synaptic vesicles, but in astrocytes, its expression is pronounced only in immature cells and shows a rapid decline during the first 3 postnatal weeks so that it has almost disappeared at the end of the third week in well-differentiated astrocytes, where its role has probably been taken over by ENT3.
authors.affiliation: Laboratory of Brain Metabolic Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China.
authors.forename: Dan
authors.initials: D
authors.lastname: Song
authors.affiliation: Laboratory of Brain Metabolic Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China.
authors.forename: Junnan
authors.initials: J
authors.lastname: Xu
authors.affiliation: Laboratory of Brain Metabolic Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China.
authors.forename: Qiufang
authors.initials: Q
authors.lastname: Bai
authors.affiliation: Laboratory of Molecular Biology, Liaoning University of Traditional Chinese Medicine, Shenyang, P. R. China.
authors.forename: Liping
authors.initials: L
authors.lastname: Cai
authors.affiliation: Laboratory of Brain Metabolic Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China.
authors.forename: Leif
authors.initials: L
authors.lastname: Hertz
authors.affiliation: Laboratory of Brain Metabolic Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China.
authors.forename: Liang
authors.initials: L
authors.lastname: Peng
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D033703:Nucleoside Transport Proteins / Q000235:genetics / Q000378:metabolism*; D033704:Nucleotide Transport Proteins / Q000235:genetics / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology*; D035181:TATA-Box Binding Protein / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D000241:Adenosine; D000255:Adenosine Triphosphate; D003994:Bucladesine; D005904:Glial Fibrillary Acidic Protein; D018698:Glutamic Acid; D033703:Nucleoside Transport Proteins; D033704:Nucleotide Transport Proteins; D011189:Potassium Chloride; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D035181:TATA-Box Binding Protein; C501425:Slc29a3 protein, mouse; C529437:Slc17a9 protein, human; C578984:Slc17a9 protein, mouse
keywords: ATP release; ENT3; SLC17A9; adenosine; gliotransmitter; glutamate