| Summary: | 碩士 === 國立清華大學 === 分子與細胞生物研究所 === 94 === L-glutamate is the major excitatory neurotransmitter in the vertebrate central nervous system. Ionotropic glutamate receptors are divided into three subtypes, AMPA-, kainate- and NMDA-preferring receptors. Oreochomis mossambicus (tilapia) expresses eight AMPA receptor subunits (fGluR1~4a and fGluR1~4b). The glutamate-activated currents of fGluR1a(i), i represents the flip form, were only detected in the presence of the desensitization blocker, cyclothiazide. The goals of this research are to study if the tilapia fGluR1a(i) can form heteromeric receptors with other AMPA subunits, and the properties of the heteromeric AMPA receptors containing fGluR1a(i). The current-voltage (I-V) relationships of fGluR2b(i)/fGluR3a(o), o represents the flop form, and fGluR1a(o)/fGluR2b(i) were determined in Xenopus oocytes co-injected with the mixed cRNA in various ratios. The results demonstrated that fGluR3a(o) and fGluR1a(o) could individually form heteromeric receptors with fGluR2b(i). Moreover, the I-V relationships of the tilapia fGluR2b(i)/fGluR3a(o) and fGluR1a(o)/fGluR2b(i) were similar to the mammalian GluR2/GluR3 and GluR1/GluR2 receptors. Similar analysis indicated that fGluR1a(i)/fGluR2b(i) and fGluR1aR(i)/fGluR3a(o) could form heteromeric receptors; however, unlike the mammalian GluR1/GluR2 and GluR2/GluR3 receptors, the channel activities of fGluR1a(i)/fGluR2b(i) and fGluR1aR(i)/fGluR3a(o) were very low.
GluRd2 is one of the ionotropic glutamate receptors. The channel activity of GluRd2 has not been successfully detected by application of any known glutamate receptor agonists at present. On the other hand, a spontaneous GluRd2 mutation of mouse, the GluRd2Lc, has been shown to express a constitutive cation channel. Here, we also studied the zebrafish GluRd2 and GluRd2Lc. Xenoupus oocytes expressing these zebrafish GluRd2 channels displayed properties similar to their mammalian counterparts.
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