A Carboxyl-terminal Determinant of the Neuronal Glutamate Transporter, EAAC1, Is Required for Platelet-derived Growth Factor-dependent Trafficking

Abstract

The neuronal glutamate transporter, EAAC1 (excitatory amino acid carrier 1), undergoes rapid regulation after treatment with platelet-derived growth factor (PDGF) or phorbol ester in C6 glioma cells and neurons. A large intracellular pool of EAAC1 exists, from which transporters are redistributed to the cell surface in response to these signals. Here we show that PDGF had no effect on subcellular localization of the glial glutamate transporter, GLT-1, after transfection into C6 glioma cells. Chimeras consisting of domains from EAAC1 or GLT-1 were used to investigate structural motifs involved in PDGF-dependent redistribution of EAAC1. PDGF did not induce trafficking of an EAAC1 chimera containing the carboxyl-terminal domain of GLT-1; however, it did induce trafficking of a GLT-1 chimera containing the carboxyl-terminal domain of EAAC1. A truncated mutant of EAAC1 lacking 10 carboxyl-terminal amino acids was responsive to PDGF, whereas a mutant lacking 20 residues was not. Alanine substitution mutagenesis in this region revealed a short motif, 502YVN504, necessary for regulated trafficking. This motif was also involved in protein kinase C-dependent trafficking, as mutant transporters exhibited an attenuated response to phorbol ester. Interestingly, the presence of YVN in the homologous region of a nonresponsive chimera was not sufficient to confer regulated trafficking; however, the presence of a 12-amino acid motif starting at this Tyr residue was sufficient to confer responsiveness to PDGF. These studies identify a novel motif within the carboxyl terminus of EAAC1 which is required for regulated trafficking. The possibility that this motif targets EAAC1 to an intracellular, “regulated pool” is discussed. The neuronal glutamate transporter, EAAC1 (excitatory amino acid carrier 1), undergoes rapid regulation after treatment with platelet-derived growth factor (PDGF) or phorbol ester in C6 glioma cells and neurons. A large intracellular pool of EAAC1 exists, from which transporters are redistributed to the cell surface in response to these signals. Here we show that PDGF had no effect on subcellular localization of the glial glutamate transporter, GLT-1, after transfection into C6 glioma cells. Chimeras consisting of domains from EAAC1 or GLT-1 were used to investigate structural motifs involved in PDGF-dependent redistribution of EAAC1. PDGF did not induce trafficking of an EAAC1 chimera containing the carboxyl-terminal domain of GLT-1; however, it did induce trafficking of a GLT-1 chimera containing the carboxyl-terminal domain of EAAC1. A truncated mutant of EAAC1 lacking 10 carboxyl-terminal amino acids was responsive to PDGF, whereas a mutant lacking 20 residues was not. Alanine substitution mutagenesis in this region revealed a short motif, 502YVN504, necessary for regulated trafficking. This motif was also involved in protein kinase C-dependent trafficking, as mutant transporters exhibited an attenuated response to phorbol ester. Interestingly, the presence of YVN in the homologous region of a nonresponsive chimera was not sufficient to confer regulated trafficking; however, the presence of a 12-amino acid motif starting at this Tyr residue was sufficient to confer responsiveness to PDGF. These studies identify a novel motif within the carboxyl terminus of EAAC1 which is required for regulated trafficking. The possibility that this motif targets EAAC1 to an intracellular, “regulated pool” is discussed. Excitatory neurotransmission in the mammalian central nervous system is mediated predominantly by the acidic amino acid glutamate. In addition to mediating swift synaptic depolarization, glutamatergic neurotransmission is important for physiological processes such as synapse development and synaptic plasticity (1Monaghan D.T. Bridges R.J. Cotman C.W. Annu. Rev. Pharmacol. Toxicol. 1989; 29: 365-402Crossref PubMed Scopus (2014) Google Scholar, 2Levenson J. Weeber E. Selcher J.C. Kategaya L.S. Sweatt J.D. Eskin A. Nat. Neurosci. 2001; 5: 155-161Crossref Scopus (126) Google Scholar, 3Tsvetkov E. Shin R.M. Bolshakov V.Y. Neuron. 2004; 41: 139-151Abstract Full Text Full Text PDF PubMed Scopus (102) Google Scholar). However, high levels of extracellular glutamate result in excessive activation of glutamate receptors, a factor that presumably contributes to the cytotoxicity associated with stroke, hypoglycemia, and brain injury (4Choi D.W. J. Neurobiol. 1992; 23: 1261-1276Crossref PubMed Scopus (2062) Google Scholar, 5Palmer A.M. Marion D.W. Botscheller M.L. Swedlow P.E. Styren S.D. DeKosky S.T. J. Neurochem. 1993; 61: 2015-2024Crossref PubMed Scopus (365) Google Scholar, 6Nilsson P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google Scholar). Synaptic glutamate concentrations are tightly regulated by a family of high affinity, Na+-dependent glutamate transporters, ensuring crisp synaptic neurotransmission. This family consists of five members: GLAST 4The abbreviations used are: GLAST, glutamate/aspartate transporter; ANOVA, analysis of variance; CMV, cytomegalovirus; EAAC1, excitatory amino acid carrier 1; EAAT1, 2, 3, 4, and 5, excitatory amino acid transporter 1, 2, 3, 4, and 5, respectively; EEEG, chimera of three domains from EAAC1 and the final domain from GLT-1; GABA, γ-aminobutyric acid; GAT1, γ-aminobutyric acid transporter subtype 1; GGGE, chimera of three domains from GLT-1 and the final domain from EAAC1; GLT-1, glutamate transporter 1; HA, hemagglutinin; PDGF, platelet-derived growth factor; PKC, protein kinase C; PMA, phorbol 12-myristate 13-acetate. (EAAT1), GLT-1 (EAAT2), EAAC1 (EAAT3), EAAT4, and EAAT5 (for review, see Refs. 7Sims K.D. Robinson M.B. Crit. Rev. Neurobiol. PubMed Scopus Google and Neurobiol. 2001; PubMed Scopus Google Scholar). In to transporters, EAAC1 is predominantly on it is to J.D. L. L. Neuron. Full Text PDF PubMed Scopus Google Scholar, J.D. J. PubMed Scopus Google Scholar). EAAC1 is to glutamate and activation of J. Neurosci. 2001; PubMed Google Scholar). of the neuronal glutamate transporter revealed that by EAAC1 for of glutamate in the J.D. L. Neuron. 1996; 16: Full Text Full Text PDF PubMed Scopus Google an that is and to EAAC1 also on J.D. L. L. Neuron. Full Text PDF PubMed Scopus Google Scholar, A. J.D. Cereb. PubMed Scopus Google the transporter is to glutamate as a for A. J.D. J. Neurosci. PubMed Google Scholar, J. Neurosci. 23: PubMed Google Scholar). EAAC1 is also in that of the transporter is at the cell surface in C6 glioma cells and neuronal K.D. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). kinase activation with phorbol 12-myristate or PDGF activation in an in EAAC1 at the cell surface in C6 glioma K.D. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar, J.D. Robinson M.B. J. Neurosci. PubMed Google or neuronal Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, Robinson M.B. Pharmacol. PubMed Scopus Google Scholar). PDGF treatment in a in EAAC1 at the cell from of EAAC1 at the a effect on cell surface and to and to of EAAC1 Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). The effect of PDGF on glutamate transporters not The of glutamate in the is mediated by GLT-1, which is on processes that the synapse (for review, see Refs. Neurobiol. 2001; PubMed Scopus Google and M.B. Neurochem. Scopus Google Scholar). The trafficking of EAAC1 as as are by transporters to result in trafficking are In the we to identify amino acid motifs in EAAC1 which are involved in trafficking of EAAC1 to the cell residues involved in this we to trafficking of EAAC1. glioma cells were from the cell were from and were from was from transfection was from and were from PDGF was from and acid protein were from were from and were from was from was from and were from and GLT-1 were the of J.D. L. L. Neuron. Full Text PDF PubMed Scopus Google Scholar). was from and and were from was from glioma were in with and in at were used to and no or in were from of glutamate transporters were GLT-1 and EAAC1 transporter A. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar). was by EAAC1 acids into the from and truncated were by and into the with as the amino acid of acids and as the amino acid of acids acid substitution were the mutagenesis from and or chimera were by at the at the of of C6 cells were to in the of with a were with of with of in a to of cells were in containing for to treatment with PDGF or surface were as Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, J.D. Robinson M.B. J. Neurosci. PubMed Google Scholar). cell were with containing and The cells were in of in for at with The was and was by the cells with containing for at with were in of containing and and and of by were was to cell surface and of these was and such that the of in the and the in the the from is of Na+-dependent in C6 glioma was in as Robinson M.B. J. Neurochem. 1996; PubMed Scopus (126) Google Scholar). with PDGF, C6 cells were in a were with of or and with for These and result in a the of treatment with PDGF and of the of transporter of the cells were and were for analysis of in a Na+-dependent was as the in in the presence and of C6 cells were with and in of containing and were by with of at for and of cell protein was at with or or of or were by with of for at were with and at for in of were on to and for in containing were with the or were and with or were with was see an at which to EAAC1 and a at which to EAAC1 K.D. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar, J. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). the of and were and used to EAAC1 of the in cell or intracellular was to the of in the The of transporter in a was as a of transporter in the was used as a and to that cells were the in which was with cell were on this of were In the did not to for in were not are as the and with analysis or These were to the effect of PDGF on transporters to the effect of PDGF on In for we the of PDGF a with the of a of of PDGF on EAAC1 and we that C6 glioma with PDGF in an in Na+-dependent This is associated with an in EAAC1 at the cell as by and analysis K.D. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar). The central nervous C6 glioma cell is an system to EAAC1 in it EAAC1 of the glutamate transporter J.D. Robinson M.B. J. Neurosci. PubMed Google Scholar). In and EAAC1 cell surface were after a treatment with however, were not the effect of PDGF on EAAC1 was C6 cells were with PDGF for and cell surface was by and with had no effect on cell surface of EAAC1 at not PDGF cell surface of EAAC1 of at 1, A and PDGF glutamate of at however, and a with glutamate in a the of treatment with PDGF and of the of transporter the at and were after of PDGF a on EAAC1 and the of PDGF on EAAC1 are it was PDGF the glutamate transporter, the effect of PDGF on GLT-1, C6 cells were with a GLT-1, and cell surface was by and of GLT-1 was to the in the 1), and was no in cell surface GLT-1 with PDGF treatment of 2, A and In of EAAC1 was at the cell surface in the 1), and PDGF cell surface of EAAC1 to of 2, and in with studies K.D. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). in to on EAAC1, PDGF had no effect on subcellular localization of transporter and of PDGF on transporter C6 glioma were with transporter transporter is the of transporter in the after as a of The effect of PDGF on cell surface is as a of that in cells. are the the of is in transporter of PDGF on transporter of of P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google E. Shin R.M. Bolshakov V.Y. Neuron. 2004; 41: 139-151Abstract Full Text Full Text PDF PubMed Scopus (102) Google (4Choi D.W. J. Neurobiol. 1992; 23: 1261-1276Crossref PubMed Scopus (2062) Google Neurobiol. 2001; PubMed Scopus Google 10 Neurobiol. 2001; PubMed Scopus Google P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google 10 J. Neurosci. 23: PubMed Google 10 Neurobiol. 2001; PubMed Scopus Google K.D. Robinson M.B. Crit. Rev. Neurobiol. PubMed Scopus Google Neurobiol. 2001; PubMed Scopus Google Neurobiol. 2001; PubMed Scopus Google A. J.D. J. Neurosci. PubMed Google K.D. Robinson M.B. Crit. Rev. Neurobiol. PubMed Scopus Google K.D. Robinson M.B. Crit. Rev. Neurobiol. PubMed Scopus Google K.D. Robinson M.B. Crit. Rev. Neurobiol. PubMed Scopus Google P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google 10 P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google (4Choi D.W. J. Neurobiol. 1992; 23: 1261-1276Crossref PubMed Scopus (2062) Google 10 P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google P. Laursen H. Hillered L. Hansen A.J. J. Cereb. Blood Flow Metab. 1996; 16: 262-270Crossref PubMed Scopus (103) Google in a The of EAAC1 for on the of the of a glutamate transporter E. 2004; PubMed Scopus Google these glutamate transporters are to with amino and carboxyl The mammalian of this family (for review, see Neurobiol. 2001; PubMed Scopus Google that the effect of PDGF to in of these the effect of PDGF was used to motifs of EAAC1 involved in In an consisting of domains from EAAC1 or GLT-1 were used to identify structural motifs required for regulation of GLT-1 A. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google Scholar). Chimeras containing the carboxyl terminus of EAAC1 were with an to from EAAC1. PDGF had no effect on cell surface of GLT-1, substitution of an EAAC1 domain with an domain of GLT-1 to that EAAC1 domain was necessary for PDGF-dependent C6 glioma were with transporters, and trafficking was by of cell surface and PDGF cell surface of to of that the did not with this regulated trafficking of EAAC1. we is that C6 cells a to the which is the transporter however, we were to the and from this was in an to the the and transporter to GLT-1, containing GLT-1 domains a of transporters at the cell surface in the However, was intracellular transporter for were for to PDGF to EAAC1 not However, the was to of the in response to PDGF with EAAC1. PDGF had no effect on cell surface of of which from the at the cell surface of EAAC1 or 3, and residues within the carboxyl-terminal amino acids of EAAC1 are required for PDGF-dependent The consists of three GLT-1 domains and the carboxyl terminus of EAAC1. PDGF cell surface of to of 3, and which was not from the in cell surface EAAC1 or the carboxyl-terminal residues of EAAC1 are sufficient to confer trafficking to of this transporter for PDGF-dependent of EAAC1 were to on the carboxyl terminus of EAAC1. These were with the C6 glioma did not with the C6 cells were with EAAC1, lacking the 10 or the 20 amino acids trafficking was by and PDGF at the cell surface to of 4, and the 10 amino acids of the carboxyl terminus are not required for this In PDGF did not cell surface of 4, and that amino acids are necessary for trafficking. this motif is for PDGF or required for regulated the of on truncated transporters were In EAAC1 cell surface within Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). we that cell surface of to of that the 10 residues are not required for the in cell surface Interestingly, the in cell surface of was attenuated of with the in However, not is that to the of transporter in the for of the The was not to mutant transporter and and was not in PDGF is that this effect from protein and of the transporter this possibility is that the of the is by the and the the was the was transporter that in the in the However, the in transporter in the with treatment was not possibility is that the of the it residues that by for transporter in the the cell surface was also to the of transporter in the the cell surface were for in the cell surface of to of did not cell surface of which was from with the were of the it that amino acids are also required for of PDGF or on EAAC1 or substitution and of PDGF on or substitution C6 cells were with or EAAC1 cells were with PDGF or for cell surface were and with at as were by were with and of the carboxyl-terminal amino acids of EAAC1, with the for and acids in were in of three to the of PDGF or on for that PDGF did not cell surface of of a of with in cell surface of by PDGF with with cell surface of transporter in with cell surface of transporter in cells of of with in cell surface of by in with cell surface of transporter in cells. with cell surface of transporter in cells. of PDGF on or substitution of the of a of with cell surface of transporter in with cell surface of transporter in cells PDGF it was not The of in is for it did not with 20 A for of identify amino acids involved in trafficking this acid was In a residue is amino acids of the of and is the possibility that the transporter at this of these these and were also in this substitution of three amino acids were to in C6 glioma were with or mutant transporters, and trafficking was by by The did not with trafficking, as PDGF cell surface of to of 5, and The of PDGF on mutant transporters were in with the effect of PDGF on PDGF cell surface of to of that residues are not required for this or to to attenuated the in transporter at the cell surface was from and PDGF surface with Interestingly, was to PDGF had no effect on cell surface of the transporter of 5, and amino acids as for trafficking. also this motif is for PDGF, or these residues are involved in trafficking of EAAC1 as cell surface of to of which was attenuated with the in in of it these residues are also involved in trafficking of EAAC1. However, at the cell surface residues are involved in regulation of EAAC1. EAAC1 on Tyr after PDGF the the of residues for trafficking of EAAC1 was of within this motif a PDGF activation and transporter studies on the transporter, GAT1, that of residues in is required for the in at the cell in this the from J. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). of EAAC1 from or C6 glioma was of EAAC1, or was after PDGF treatment by transporter and with that EAAC1 1), or was was no of transporter on with or PDGF for of the EAAC1 not with from or C6 cells was by with or were no transporter with or PDGF that of the transporters was with for EAAC1, for for not a in were and with In with PDGF, a at to PDGF was that the was to In from C6 cells were with and were with A to was in in which was used for as a was a of that was this was in from in which was used as the not However, this was not a and the was the as that in the In this did not with PDGF treatment and was not in from cells. was a of transporter the from the that EAAC1 not and PDGF treatment not result in of EAAC1. In these the that of Tyr within is a necessary for EAAC1 trafficking. of within PDGF-dependent of it that of within the motif is not required for PDGF-dependent trafficking of EAAC1, we to residues within the motif were required for substitution mutant and three were were to was to and was to of with the residue was to the that of C6 glioma were with or mutant transporters, and trafficking was by by The of PDGF on mutant transporters were in with the effect of PDGF on PDGF cell surface of to of PDGF cell surface of mutant and it that of the motif is necessary to PDGF-dependent trafficking of EAAC1. to to the for EAAC1 and GLT-1 are within EAAC1 with within the nonresponsive transporter, EEEG, the carboxyl terminus of GLT-1, and of we to in the the response to PDGF The was and transporter trafficking was by and PDGF did not cell surface of of PDGF did not cell surface of containing of EAAC1 residues for GLT-1 residues in the or However, 10 amino acids were in that the 12-amino acid motif of EAAC1 was in the carboxyl terminus of EEEG, PDGF cell surface of the transporter of and this motif in EAAC1, is sufficient to confer trafficking to a nonresponsive these studies that this 12-amino acid motif sufficient to confer regulated trafficking to a nonresponsive transporter, we the possibility that motifs are also we these residues the carboxyl terminus of an The of were by the mutant protein was by after transfection in C6 cells an The of and transfection were no was a we that the after transfection in a cell that to of protein at it is not to this motif is sufficient to confer PDGF-dependent trafficking an protein C6 In the we that PDGF had on EAAC1 and GLT-1; PDGF cell surface of EAAC1, whereas it had no effect on subcellular localization of GLT-1 is for the of glutamate the (for review, see Neurobiol. 2001; PubMed Scopus Google whereas the of EAAC1 to glutamate is in the it for of glutamate J.D. L. Neuron. 1996; 16: Full Text Full Text PDF PubMed Scopus Google Scholar). is the of a large intracellular pool of EAAC1 in A. J.D. Cereb. PubMed Scopus Google Scholar, J.D. Robinson M.B. J. Neurosci. PubMed Google Scholar). EAAC1 to a in glutamate at excitatory J. Weeber E. Selcher J.C. Kategaya L.S. Sweatt J.D. Eskin A. Nat. Neurosci. 2001; 5: 155-161Crossref Scopus (126) Google that of was associated with of EAAC1 from the cell to the cell surface and that also glutamate and EAAC1 at the Interestingly, M.L. in a that of EAAC1 in high The effect of PDGF on EAAC1 and GLT-1 that these transporters regulated a to of glutamate these cell and The transporter undergoes a of regulation in response to in (for review, see Rev. 2004; PubMed Scopus Google Scholar). to identify domains important for this is no of of residues within to trafficking, whereas a of studies motifs important for to a regulated that motifs within the amino and carboxyl are important for trafficking, with the motif involved in of J. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, PubMed Scopus Google and a motif with acidic residues to to the PubMed Scopus Google Scholar, J. PubMed Google Scholar). motifs within the carboxyl terminus also as important for in the A.M. J. PubMed Scopus Google Scholar). Interestingly, the carboxyl terminus of EAAC1 was to necessary for transporter trafficking to the cell surface in response to PDGF as PDGF did not cell surface of the In PDGF did cell surface of the substitution with the carboxyl terminus of EAAC1 to confer trafficking to a nonresponsive transporter, GLT-1, it is that within GLT-1 also we that the subcellular localization the responsiveness of the transporter to PDGF. of GLT-1 is at the cell whereas of EAAC1 is GLT-1, transporters also a of transporters at the cell However, of was at the cell surface in the intracellular transporters in response to PDGF This to that amino acid motifs within the carboxyl terminus of EAAC1 were involved in trafficking of the the carboxyl we that amino acids were required for trafficking of EAAC1, as PDGF cell surface of not These residues were also involved in trafficking the effect of on cell surface was a short amino acid motif, 502YVN504, that is for trafficking, as PDGF treatment had no effect on subcellular localization of were not from the in and exhibited a an attenuated response to PDGF, that in addition to 502YVN504, residues within the motif also involved in the PDGF-dependent In of the motif, was necessary to confer trafficking to a nonresponsive transporter, the for was to trafficking or the motif was involved in regulated trafficking. Interestingly, this motif also to involved in trafficking the in at the cell surface was to residues within the motif were required for of EAAC1. that or to or to did not PDGF-dependent trafficking. In of to also did not PDGF-dependent trafficking of EAAC1. the motif to PDGF-dependent trafficking is However, is not the motif sufficient to confer PDGF-dependent trafficking to the nonresponsive transporter, amino acids of EAAC1, are required in for the transporter to to PDGF. are in which this motif involved in trafficking of EAAC1. the residues by of PDGF, to of EAAC1. this motif required for regulated trafficking by EAAC1 to an intracellular, regulated Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google that intracellular and regulated trafficking of EAAC1. In these and regulated trafficking of EAAC1 to to the or in cell surface EAAC1 had no effect on This that required for the or EAAC1 to a regulated pool and the a in which this pool in response to these signals. The of PDGF and are not K.D. Robinson M.B. J. Full Text Full Text PDF PubMed Scopus Google this is with the possibility that on the pool of transporter for of by was in was no of of EAAC1 or after PDGF the that PDGF trafficking by a that on The with were we that a of the transporter with the not with the the EAAC1 not to on residues in the or after PDGF it is that of is required for trafficking of EAAC1. In of Tyr within is in GLT-1 transporter that not to whereas and are not. PDGF cell surface of that Tyr on not required for PDGF-dependent possibility is that the 12-amino acid motif to EAAC1 to an intracellular, regulated this motif, residues were for the response of EAAC1 to PDGF. the of transporter at the cell surface in the was for EAAC1, or that the of transporter was in the to cell surface from intracellular to within the intracellular transporter In of the the of PDGF or were in and that these residues involved in EAAC1 to an intracellular, regulated The effect of PDGF on cell surface was whereas the effect of on cell surface was However, this is not a that and PDGF the of regulated trafficking of EAAC1 PDGF and to the of of EAAC1 to the however, in addition to the on to of the transporter Robinson M.B. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). in a in cell surface of EAAC1 PDGF which result from the effect of on and of EAAC1 at the domains required for the of on of EAAC1. the effect of on of the transporter for the effect of on it is that amino acids are as of a 12-amino acid motif to EAAC1 to an intracellular pool that regulated by of the motif is required to PDGF-dependent trafficking, possibility is that the motif as a for that are required for the transporter to a regulated Interestingly, the 12-amino acid motif is also in a motif, J. Neurosci. PubMed Google that this motif is a motif required for of the of EAAC1, in cells and in neurons. this motif, and to residues for of The motif with the motif in this as sufficient for trafficking of a nonresponsive motifs within the carboxyl-terminal important for regulated trafficking of EAAC1 and of In these motifs of localization and to a regulated In we that the glutamate transporter, GLT-1, not to the cell surface in response to PDGF also that the carboxyl terminus of EAAC1 is necessary for PDGF-dependent trafficking to the In we within the carboxyl terminus as necessary for regulated trafficking and sufficient to confer trafficking to a nonresponsive this motif, residues were for the also that of within this motif is not required for PDGF-dependent redistribution of EAAC1. The of this motif not to trafficking; it the transporter to an intracellular which regulated by activation of PDGF or for the transporters and for the of and also for the of glutamate E. for