title: Regulation of the glutamate transporter EAAT3 by mammalian target of rapamycin mTOR.
abstract: The serine/threonine kinase mammalian target of rapamycin (mTOR) is stimulated by insulin, growth factors and nutrients and confers survival of several cell types. The kinase has previously been shown to stimulate amino acid uptake. In neurons, the cellular uptake of glutamate by the excitatory amino-acid transporters (EAATs) decreases excitation and thus confers protection against excitotoxicity. In epithelia, EAAT3 accomplishes transepithelial glutamate and aspartate transport. The present study explored, whether mTOR regulates EAAT3 (SLC1A1). To this end, cRNA encoding EAAT3 was injected into Xenopus oocytes with or without cRNA encoding mTOR and the glutamate induced current (I(glu)), a measure of glutamate transport, determined by dual electrode voltage clamp. Moreover, EAAT3 protein abundance was determined utilizing chemiluminescence. As a result, I(glu) was observed in Xenopus oocytes expressing EAAT3 but not in water injected oocytes. Coexpression of mTOR significantly increased I(glu), an effect reversed by rapamycin (100 nM). mTOR coexpression increased EAAT3 protein abundance in the cell membrane. The decay of I(glu) following inhibition of carrier insertion with brefeldin A in oocytes coexpressing EAAT3 with mTOR was similar in the presence and absence of rapamycin (100 nM). In conclusion, mTOR is a novel powerful regulator of EAAT3 and may thus contribute to protection against neuroexcitotoxicity.
authors.affiliation: Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Almilaji
authors.forename: Tatsiana
authors.initials: T
authors.lastname: Pakladok
authors.forename: Anne
authors.initials: A
authors.lastname: Guo
authors.forename: Carlos
authors.initials: C
authors.lastname: Munoz
authors.forename: Michael
authors.initials: M
authors.lastname: Föller
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D050580:Excitatory Amino Acid Transporter 3 / Q000096:biosynthesis* / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D009865:Oocytes; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
chemical_list: D050580:Excitatory Amino Acid Transporter 3; C493400:SLC1A1 protein, human; D018698:Glutamic Acid; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus