科研之友
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摘要
The number of each subclass of ionotropic glutamate receptors (iGluRs) at the spines is differentially regulated either constitutively or in a neuronal activity-dependent manner. The delta 2 glutamate receptor (GluR delta 2) is abundantly expressed at the spines of Purkinje cell dendrites and controls synaptic plasticity in the cerebellum. To obtain clues to the trafficking mechanism of the iGluRs, we expressed wildtype or mutant GluR delta 2 in cultured hippocampal and Purkinje neurons and analyzed their intracellular localization using immunocytochemical techniques. Quantitative analysis revealed that deletion of the 20 amino acids at the center of the C terminus (region E) significantly reduced the amount of GluR delta 2 protein at the spines in both types of neurons. This effect was partially antagonized by the inhibition of endocytosis by high dose sucrose treatment or coexpression of dominant negative dynamin. In addition, mutant GluR delta 2 lacking the E region (GluR delta 2(Delta E)), but not wild-type GluR delta 2, was found to colocalize with the endosomal markers Rab4 and Rab7. Moreover, the antibody-feeding assay revealed that GluR delta 2(Delta E) was internalized more rapidly than GluR delta 2(wt). These results indicate that the E region (more specifically, a 12-amino-acid-long segment of the E2 region) is necessary for rendering GluR delta 2 resistant to endocytosis from the cell surface at the spines. Furthermore, insertion of the E2 region alone into the C terminus of the GluR1 subtype of iGluRs was sufficient to increase the amount of GluR1 proteins in the spines. Therefore, we propose that the E2 region of GluR delta 2 is necessary, and also sufficient, to inhibit endocytosis of the receptor from postsynaptic membranes.
- 出版日期2006-6-23
