Abstract
Ionotropic glutamate receptors (iGluRs) mediate the synaptic and metabolic actions of glutamate. These iGluRs are classified within the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type, kainate-type, and N-methyl-d-aspartate (NMDA)-type functional receptor families. The iGluR assemblies are regulated by transcription, alternative splicing, and cytoplasmic post-translational modifications. The iGluR subunit proteins are transported from the endoplasmic reticulum, inserted into the synaptic membranes, and anchored at their action site by different scaffolding and interacting proteins. The functional properties of iGluRs depend on their subunit composition, the amino acid sequence of the protein domains, and the scaffolding proteins in the synaptic membranes. The iGluRs are removed from the membranes by enzymatic action and endocytosis. Hippocampal iGluRs are rearranged through the upregulation and downregulation of the subunits following deafferentation and epileptic seizures. The rearrangement of iGluRs and the alteration of their subunit composition transform neurons into “pathological” cells, determining the further plasticity or pathology of the hippocampal formation. In the present review, we summarize the expression of AMPA, kainate, and NMDA receptor subunits following deafferentation, repeated mild seizures, and status epilepticus. We compare our results to literature descriptions, and draw conclusions as to the reactive plasticity of iGluRs in the hippocampus.
Highlights
Glutamic acid (Glu) is the main excitatory neurotransmitter in the mammalian brain
The present review focuses on the ionotropic glutamate receptors (iGluRs) family members, treating the possible
This study suggested the presence of AMPA receptors (AMPARs) in some interneurons of the pyramidal layer and alveus of CA1 [34]
Summary
Glutamic acid (Glu) is the main excitatory neurotransmitter in the mammalian brain. Neurons, astrocytes, and probably other glial cells use Glu for information processing [1,2]. The short-term and long-term synaptic effects of Glu are mediated by ionotropic and metabotropic Glu receptors (iGluRs and mGluRs) [1,3,6]. There are three main structurally and pharmacologically different iGluR classes in the adult mammalian brain: α-amGliun; oTthh-e3er-eehfxoycrideta,rttoohrxeyygn-re5euy-mrmoteartatthnesrymol-fi4stsh-iioesnrooixndaetznhoteblcereanpitnrraoclopnnietoarvinnoisuchsaisgcyhisdtaemm(Ao(uMCnNtPoSA)f ii)sGrllaeurcRgesepl(yFtiomgruasri,netk1aa)i.niTendhaebtreye receptors, and N-metahreytlh-Dree-amspaianrsttartuect(uNraMllyDanAd)prheacrempatcoorlosg[i1ca,3ll,y6]d.ifAferpeanrttiGfrluoRmcltahsseesseinmtahejoardiuGltlumRams,mtahleiarne are some ill-charactebrraiizne: dα-a“mdienlot-a3-”hytdyrpoexyo-5r-m“eothryplh-4a-inso”xarzeocleeprtooprison(iGc alcuidD(1AManPAd) GrecleupDto2rs),, kwainhaitcehrecsehpatorers,structural homologyatnodAN-MmePtAhyla-Dn-daskpaaritnataet(eNrMecDeAp)troercsep; thoorsw[1e,3v,6e]r.,Athpaeryt farorme nthoetsegmataejodr ibGyluGRsl,ut,hearnedarde osomnoet function ill-characterized “delta” type or “orphan” receptors (GluD1 and GluD2), which share structural as cation chhoamnonloeglys.toIAnMstPeAadan, dthkeaiynacteonrenceepcttorps;rheoswynevaepr,ttihceyanarde npoot sgtasteydnbaypGtilcu,ealnedmdeonntost fwunitchtiotnhe help of an extracelalsuclaatriognlcyhcaonpnerlos.teIninste[a1d7,]t.hey connect presynaptic and postsynaptic elements with the help of an extracellular glycoprotein [17]. The iGluRs are heterotetramers consisting of four transmembrane proteins with a large extracellular ligand-binding domain, a common pore-forming transmembrane domain, and an intracellular C-terminal domain: these transmembrane proteins are the receptor subunits [1,3,18]. There are multiple subunit variants due to the alternative splicing and editing of the RNA transcripts; these are listed in more comprehensive reviews [1]
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