Cloning of a putative glutamate receptor: a low affinity kainate-binding subunit.
Kainate, a glutamate receptor agonist, is a potent neuroexcitatory agent that produces epileptiform activity and selective neuronal degeneration. Binding studies using neuronal membrane homogenates or brain sections have identified sites having either high or low affinity for [3H]kainate. Here we report the cloning of a gene, GluR7, with approximately 75% sequence identity with the previously cloned GluR5 and GluR6 subunit genes. Transcripts of the GluR7 gene are evident in brain areas that bind [3H]kainate and are susceptible to kainate-induced neurotoxicity. We have performed ligand binding studies with membranes of transfected HeLa cells expressing GluR6 or GluR7 subunits. Our data show that the GluR6 and GluR7 subunits have a rank order of agonist affinity (domoate greater than kainate much greater than L-glutamate, quisqualate much greater than AMPA, NMDA) and a dissociation constant for kainate (95 and 77 nM, respectively) characteristic of the low affinity kainate-binding sites described in the brain.
Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037.
B
B
Bettler
J
J
Egebjerg
G
G
Sharma
G
G
Pecht
I
I
Hermans-Borgmeyer
C
C
Moll
C F
CF
Stevens
S
S
Heinemann
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure; D001923:Brain Chemistry; D003001:Cloning, Molecular; D005260:Female; D015870:Gene Expression / Q000235:genetics; D005971:Glutamates / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D006367:HeLa Cells; D006651:Histocytochemistry; D006801:Humans; D007267:Injections; D007608:Kainic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D009865:Oocytes / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D011485:Protein Binding; D012313:RNA / Q000235:genetics; D051381:Rats; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
D005971:Glutamates; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D012313:RNA; C012301:domoic acid; D007608:Kainic Acid