Inward rectification of both AMPA and kainate subtype glutamate receptors generated by polyamine-mediated ion channel block.
CA2+-permeable glutamate receptors assembled from subunits containing a GLN residue at the RNA editing site in membrane domain 2 show strong inward rectification. In HEK 293 cells transfected with the kainate receptor subunit GluR6(Q), inward rectification is lost in outside-out patches, suggesting a role for diffusible, cytoplasmic factors. Inclusion of different polyamines in the internal solution restored inward rectification, whereas Mg2+ (1 mM) was inactive. Spermidine (Kd[0 mV] = 5.5 microM) was of higher affinity than spermidine (Kd[0 mV] = 25.4 microM) or putrescine (Kd[0 mV] = 1.2 mM). AMPA receptors assembled from GluRA(flip) showed even higher affinity for spermine (Kd[0 mV] = 1.5 microM). Analysis of the voltage dependence of whole-cell responses predicted intracellular free spermine and spermidine concentrations of 51 and 153 muM, respectively.
Bowie
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D
Laboratory of Cellular and Molecular Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Mayer
M L
ML
D002118:Calcium / Q000502:physiology; D002461:Cell Line, Transformed; D018698:Glutamic Acid / Q000494:pharmacology; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry; D015640:Ion Channel Gating / Q000187:drug effects*; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007668:Kidney; D008274:Magnesium / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011700:Putrescine / Q000494:pharmacology*; D018091:Receptors, AMPA / Q000187:drug effects* / Q000502:physiology; D018092:Kainic Acid Receptors / Q000187:drug effects* / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013095:Spermidine / Q000494:pharmacology*; D013096:Spermine / Q000494:pharmacology*; D014162:Transfection
D002118:Calcium; D018698:Glutamic Acid; D007608:Kainic Acid; D008274:Magnesium; D011700:Putrescine; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D011993:Recombinant Fusion Proteins; D013095:Spermidine; D013096:Spermine; C012301:domoic acid