Biomedical subjects

S L Nutt

Publications and source records attributed to S L Nutt.

22 records · Page 2Linked to original sources

PubMed1994

Human glutamate receptor hGluR3 flip and flop isoforms: cloning and sequencing of the cDNAs and primary structure of the proteins.

Several cDNA clones encoding the human glutamate receptor subunit GluR3 flip and flop isoforms, were isolated from human hippocampus and fetal brain libraries. DNA sequence analysis revealed overlapping clones permitting the reconstruction of full-length GluR3-flip and GluR3-flop cDNAs. The GluR3 cDNAs demonstrated an 94.1-94.7% nucleotide (nt) identity with the corresponding rat cDNAs. The nt sequence of the GluR3 cDNAs would encode 894 amino acid proteins that have a 99.4% identity with the rat GluR3 isoforms. The human GluR3 cDNAs predict an additional 6 amino acid in the N-terminal signal peptide as compared to the rat GluR3.

Alternative Splicing↗

PubMed1994

Differential RNA editing efficiency of AMPA receptor subunit GluR-2 in human brain.

RNA editing in rat brain has been found to control a determinant of cation flow in alpha-amino-3-hydroxy-5-methyl-4-isoxasolepropionic acid (AMPA)-gated channels. Here we provide the first evidence that this RNA editing phenomenon occurs in human brain and is differentially regulated. Sequence analysis of human genomic DNA revealed a Q codon (CAG) in the putative channel-forming segment of human GluR-2, whereas in the majority of cDNA clones an R codon (CGG) was found. Examination of editing in various brain tissues revealed differences in the efficiency of this process. The hippocampus, cerebellum and temporal cortex harbour 100% edited GluR-2, whereas only 72% of substantia nigra, 89% of corpus striatum and 96% of fetal cDNAs have been found to be edited. This new discovery of differential efficiency of RNA editing has important implications in AMPA receptor channel-mediated calcium influx. AMPA receptors are thought to mediate the majority of the fast excitatory synaptic neurotransmission; the RNA editing process may therefore play a critical role in normal brain function and development. Dysfunction of this RNA editing process may have neuropathological consequences and could be related to certain neurodegenerative diseases.

Animals↗

PubMed1994

Functional expression and pharmacological characterization of the human EAA4 (GluR6) glutamate receptor: a kainate selective channel subunit.

A cDNA encoding an ionotropic glutamate receptor subunit protein humEAA4 (GluR6), has been cloned from a human fetal brain library. This cDNA when expressed in COS or HEK-293 cells is associated with high-affinity kainate receptor binding and ion channel formation. We have successfully established cell lines stably expressing humEAA4 in HEK-293 cells This is the first report of the establishment of stable cell lines expressing a glutamate receptor channel. The relative potency of compounds for displacing [3H]-kainate binding to humEAA4 receptors expressed in COS or HEK-293 cells is domoate > kainate > quisqualate > 6-cyano-7-nitroquinoxaline-2,3-dione > L-glutamate = 6,7- dinitroquinoxaline-2,3-dione > dihydrokainate. Applications of kainate, glutamate, and domoate but not AMPA evoked rapidly desensitizing currents in cells expressing homo-oligomeric humEAA4 in a concentration dependent manner. The order of potency was: domoate > kainate > L-glutamate. Although AMPA did not itself activate humEAA4 receptors it did reduce, to a limited extent, kainate-evoked responses. AMPA may therefore be a weak partial agonist for this receptor. To date this effect has not been demonstrated with rat GluR6. It is possible that subtle species differences may exist in the nature of agonist receptor interaction. Kainate evoked currents were attenuated by the quinoxalinediones CNQX and DNQX but not by DAP5. The receptor desensitization was attenuated on application of concanavalin A. Ion-permeability studies indicated that the receptor-linked ion channel is permeable to both Na+ and Ca2+ ions.

Amino Acid Sequence↗

PubMed1994

Molecular characterization of the human EAA5 (GluR7) receptor: a high-affinity kainate receptor with novel potential RNA editing sites.

Several cDNA clones encoding EAA5 receptor polypeptides were isolated from a human fetal brain library. The EAA5 cDNAs demonstrated an 88.7-90.1% nucleotide identity with rat GluR7 cDNAs. The nucleotide sequence of EAA5 would encode a 919-amino acid protein, that has a 97.7-98.9% identity with the rat GluR7 receptor. Two variation of the EAA5 cDNA were identified which result in amino acid substitutions in the predicted extracellular amino-terminal region; Ser310-->Ala and Arg352-->Gln. These variations can be attributed to RNA editing involving T-->G and G-->A substitutions. Both the location (with respect to glutamate receptors), and the nucleotides involved, in this putative RNA editing are novel and may therefore involve novel mechanisms. Ligand binding studies with membranes of transfected COS-1 cells expressing EAA5 polypeptides demonstrate a rank order of ligand affinity similar to that observed with the rat GluR7 receptor, and a dissociation constant for kainate (2.72 +/- 0.12 nM (n = 3)) that is approximately 20- to 30-fold higher than that observed for the rat GluR7 receptor. All of the ligands tested had a higher affinity for the human EAA5 receptor as compared to the rat GluR7 receptor. This report provides another example of pharmacological differences for similar receptors across species.

Amino Acid Sequence↗