|WikiProject Molecular and Cellular Biology||(Rated Start-class, Low-importance)|
|WikiProject Neuroscience||(Rated C-class, High-importance)|
While the link refers to an interesting paper involving AMPA receptors (actually not even the actual study, just a commentary), PubMed lists about 5,348 published articles on AMPA receptors. It is unfair to highlight one specific one, especially since it is not of a general article or a review. Thus I removed the link. Nrets 01:34, 10 August 2005 (UTC)
I'm pretty sure that they form only pentamers, but I wasn't certain so I didn't want to change it. Anyone have updated info? Delldot
- What source are you basing this on? My understanding was that it was still up in the air, but I'll double check. Nrets 14:24, 10 October 2005 (UTC)
- Quick search, because I actually thought everyone pretty much accepted the tetrameric structure now:
- - Shi et al, 1998 (Rapid Spine Delivery and Redistribution of AMPA Receptors After Synaptic NMDA Receptor Activation) sidesteps the issue and refers to them as "oligomers".
- - Song and Huganir, 2002 (Regulation of AMPA receptors during synaptic plasticity) refer to them as tetramers
- - The MRC site says 2four or five".
- - Rosenmund et al, 1998 (The Tetrameric Structure of a Glutamate Receptor Channel) obviously puports to have described tetramers
- - I did find one reference (Prekumar & Auerbach, 1998; Stoichiometry of Recombinant NMDA Receptor Channels Inferred from Single-channel Current Patterns) which suggested a possible pentameric structure for AMPA.
- I think "may form tetramers or pentamers" is probably the best you're going to get; but most of the reviews I've read tentatively assume a tetrameric structure.
- Confuseddave 15:21, 22 January 2006 (UTC)
- in fact, the more I look, the more I see people assuming tetrameric structure. Have yet to come across more than one paper which says five. Confuseddave 15:33, 22 January 2006 (UTC)
Genes vs. Proteins
Hello there. The entire article refers to the subunits as GRIA1-4. My knowledge and all references I can find indicate that the subunits are GluR1-4 (Hollmann et al., and many others, 1990) or GluRA-D (Keinänen et al., and marginally fewer others, 1990) while the genes from which they are transcribed/translated are GRIA1-4. A pubmed search for GluR1 yields 1156 results while a search for GRIA1 in the same place yields 10 results. Consequently, I've changed it all over to GluR1-4, and put in a bit about the coding genes. Hope that's ok and that I'm not massively wrong. I'm currently writing my thesis about the beasts, so if I am, please tell me asap! HilJackson 15:40, 22 May 2006 (UTC)
You are entirely correct. GRIA1-4 are the genes, and technically they should be italicized. I'm doing a thesis on iGluRs myself.
You are right. GRIA1-4 are the genes and GluR1-4 the proteins. Additionally i would like to point out, that IUPHAR changed the nomenclature of the ionotropic glutamate receptors. GluR1-4 are now called GluA1-4. See the new nomenclature in the IUPHAR Database. —Preceding unsigned comment added by 220.127.116.11 (talk) 11:19, 9 June 2010 (UTC)
Two binding sites?
As everyone agrees that these receptors are tetrameric, and we know that each subunit has a binding site for glutamate, I think it's safest to say that AMPA-receptors have four binding sites. It is probable that the receptor can activate with only a couple of these binding sites occupied. I have changed the article to reflect this. Aplested 02:40, 18 August 2006 (UTC)
This is correct. "Unlike the cys-loop receptors, in which ligand-binding sites are formed at the interface between subunits, in iGluRs the ligand-binding cores are discrete domains, one copy of which is present in each subunit." Mayer, M. L. (2005). Glutamate receptor ion channels. Current Opinion in Neurobiology, 15 (3), 282-288.
inwardly rectifying potassium channels
In reference to the GluR2's rectification properties, it stated that "non-GLuR2 containing AMPAR's stop outward flow of ions once depolarized" and not specifically potassium which is the only ion that would make sense in that context so i changed it to that. perhaps a bit redundant but informative for those who don't know any better or are unsrue of what they know. maybe i don't know any better... anyone's thoughts? —The preceding unsigned comment was added by 18.104.22.168 (talk) 01:04, 16 April 2007 (UTC).
You're right; the inward rectifying current is one of K+.
receptor subunit composition
The article states that AMPARs are usually homotetrameric assemblies of GluR1s or GluR4s (no citation), but I found several references that they tend to form heterotetramers (the "dimer of dimers" mentioned in the article). I'm going to change this, but if anyone is aware of studies that contradict this, please correct me. Here are some references regarding heterotetrameric AMPAR structure:
Kew, J. N. C. & Kemp, J. A. (2005). Ionotropic and metabotropic glutamate receptor structure and pharmacology. Psychopharmacology, 179, 4 - 29.
Gregor, I. H., Ziff, E. B., & Penn, A. C. (2007). Molecular determinants of AMPA receptor subunit assembly. Trends in Neurosciences, 30 (8), 407-416.
Mayer, M. L. (2005). Glutamate receptor ion channels. Current Opinion in Neurobiology, 15 (3), 282-288.
structure and function needs a reference
"The conformation of the subunit protein in the plasma membrane caused controversy for some time. While the amino acid sequence of the subunit indicated that there were four transmembrane domains (parts of the protein that pass through the plasma membrane), proteins interacting with the subunit indicated that the N-terminus was extracellular while the C-terminus was intracellular. If each of the four transmembrane domains went all the way through the plasma membrane, then the two termini would have to be on the same side of the membrane"
There are two errors in the "Synaptic Plasticity" section
- NMDARs can only open when a depolarization from the AMPAR activation leads to repulsion of the Mg2+ cation. They can also open when the membrane is depolarized by the neighbouring regions and/or by pairing with a very strong signal.
- Unlike AMPARs, though, NMDARs are permeable to both Na+ and Ca2+. Though not entirely inaccurate, a better way to phrase it would be Although both AMPARs and NMDARs are permeable to Na+, NMDARs are further permeable to Ca2+, whereas the presence of the GluR2 subunit renders the AMPARs impermeable to Ca2+ —Preceding unsigned comment added by Paskari (talk • contribs) 12:02, 8 July 2008 (UTC)
In A 38-amino acid sequence found prior to (i.e., towards the C-terminus of) the 4th membranous domain the use of "prior" is against the convention that proteins start at the N-terminus and end at the C-terminus. So I'm not sure whether the author confused something here. Icek (talk) 20:36, 21 July 2010 (UTC)