Effects of ethanol on the rat glutamate excitatory amino acid transporter type 3 expressed in Xenopus oocytes: role of protein kinase C and phosphatidylinositol 3-kinase |
| |
Authors: | Kim Jin-Hee Lim Young-Jin Ro Young-Jin Min Seong-Won Kim Chong-Soo Do Sang-Hwan Kim Yong-Lak Zuo Zhiyi |
| |
Affiliation: | Department of Anesthesiology (J-HK, Y-JR, S-WM, C-SK), Seoul City Boramae Hospital, Seoul, Korea;Department of Anesthesiology (Y-JL, Y-JR, S-WM, C-SK, S-HD, Y-LK), Seoul National University College of Medicine, Seoul, Korea;and Department of Anesthesiology (ZZ), University of Virginia Health System, Charlottesville, Virginia. |
| |
Abstract: | Background: Glutamate is a major excitatory neurotransmitter in the central nervous system. Glutamate transporters play a critical role in maintaining extracellular glutamate concentrations. We investigated the effects of ethanol on a neuronal glutamate transporter, excitatory amino acid transporter type 3 (EAAT3), and the role of protein kinase C (PKC) and phosphatidylinositol 3‐kinase (PI3 K) in mediating these effects. Methods: EAAT3 was expressed in Xenopus oocytes by injection of EAAT3 messenger RNA. By using a two‐electrode voltage clamp, membrane currents were recorded after the application of l‐glutamate. Responses were quantified by integration of the current trace and reported as microcoulombs. Data are mean ± SEM. Results: Ethanol enhanced EAAT3 activity in a concentration‐dependent manner. At 25, 50, 100, and 200 mM of ethanol, the responses were significantly increased compared with control values. Kinetic study demonstrated that ethanol (50 mM) significantly increased Vmax (3.48 ± 0.2 μC for control versus 4.16 ± 0.24 μC for ethanol; n= 19; p < 0.05) without a significant change in the Km (65.6 ± 11.1 μM for control versus 55.8 ± 9.6 μM for ethanol; n= 19; p > 0.05) of EAAT3 for glutamate. Preincubation of the oocytes with phorbol‐12‐myristate‐13‐acetate (PMA) significantly increased EAAT3 activity (0.98 ± 0.08 μC for control versus 1.28 ± 0.09 μC for ethanol; n= 19; p < 0.05). However, there was no statistical difference among the responses of EAAT3 to PMA, ethanol, or PMA plus ethanol. Although the PKC inhibitors chelerythrine and staurosporine did not decrease the basal EAAT3 activity, they abolished the enhancement of EAAT3 activity by ethanol. Pretreatment with wortmannin, a PI3 K inhibitor, also abolished the ethanol‐enhanced EAAT3 activity. Conclusions: These results suggest that acute ethanol exposure increases EAAT3 activity at clinically relevant concentrations and that PKC and PI3 K may be involved in mediating these ethanol effects. |
| |
Keywords: | Ethanol Glutamate Transporter EAAT3 Protein Kinase C Phosphatidylinositol 3-Kinase |
本文献已被 PubMed 等数据库收录! |
|