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The lethal expression of the GluR2flip/GluR4flip AMPA receptor in HEK293 cells
Author(s) -
Iizuka Masaki,
Nishimura Seiichiro,
Wakamori Minoru,
Akiba Isamu,
Imoto Keiji,
Barsoumian Edward L.
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00270.x
Subject(s) - ampa receptor , hek 293 cells , microbiology and biotechnology , neuroscience , biology , receptor , chemistry , genetics , glutamate receptor
α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) ‐type glutamate receptors play a critical role in excitotoxicity associated with cerebral hypoxia, ischaemia and other acute brain insults. AMPA receptors are composed of GluR1–GluR4 subunits in homomeric and heteromeric assemblies, forming nonselective cation channels. In addition, each subunit has alternative splice variants, flip and flop forms. Heterologous expression studies showed that the AMPA receptor channels exhibit diverse properties depending on subunit/variant composition. For example, the absence of the GluR2 subunit makes AMPA receptor assemblies Ca 2+ ‐permeable. Excitotoxicity induced by activating AMPA receptor channels has been linked to excessive Ca 2+ influx through the GluR2‐lacking channels. Here we demonstrate that coexpression of the AMPA receptor GluR2flip and GluR4flip subunits exerts a lethal effect on HEK293 cells, whereas no lethal activity is observed in other homomeric or heteromeric combinations of AMPA receptor subunits. Patch clamp recordings and Ca 2+ imaging analyses have revealed that this GluR2flip/GluR4flip receptor exhibits a low Ca 2+ permeability. This subunit combination, however, showed prolonged Na + influx following AMPA stimulation, even in the absence of cyclothiazide, which attenuates AMPA receptor desensitization. Furthermore, the GluR2flip/GluR4flip‐mediated lethality was potentiated by the interruption of cellular Na + extrusion mechanisms using ouabain or benzamil. These observations suggest that the GluR2flip/GluR4flip receptor‐mediated excitotoxicity is attributed to Na + overload, but not Ca 2+ influx.