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1.A.10.1.11
GriK2; GluK2; GluR6 glutamate receptor, ionotropic kainate 2. The 3-d structure is known (2XXY_A). The domain organization and function have been analyzed by Das et al. (2010).  Two auxiliary subunits, Neto1 and Neto2 (Neuropilin and tolloid-like proteins) alter the trafficking, channel kinetics and pharmacology of the receptors (Howe 2014).  They reduce inward rectification without altering calcium permeability (Fisher and Mott 2012). Interactions between the pore helix (M2) and adjacent segments of the transmembrane inner (M3) and outer (M1) helices may be involved in gating (Lopez et al. 2013). Mutations in the human GRIK2 (GLUR6) cause moderate-to-severe nonsyndromic autosomal recessive mental retardation (Motazacker et al. 2007). Kainate receptors regulate KCC2 (TC# 1.A.10.1.11) expression in the hippocampus (Pressey et al. 2017). GluR6, carrying the pore loop plus adjacent transmembrane domains of the prokaryotic, glutamate-gated, K+-selective GluR0 (TC# 1.A.10.2.1), adopted several electrophysiological properties of the donor pore upon pore transplantation (Hoffmann et al. 2006). Clustered mutations in the GRIK2 kainate receptor subunit gene underlie diverse neurodevelopmental disorders (Stolz et al. 2021). Concanavalin A modulation of kainate receptor function is mediated by a shift in the conformation of the kainate receptor toward a tightly packed extracellular domain (Gonzalez et al. 2021). Partial agonism in heteromeric GLUK2/GLUK5 kainate receptor has been documented, and partial agonism observed with AMPA binding is mediated primarily due to differences in the GluK2 subunit, highlighting the distinct contributions of the subunits towards activation (Paudyal et al. 2023).  Kainate receptors (KARs) are a subtype of ionotropic glutamate receptor (iGluR) channels, a superfamily of ligand-gated ion channels which mediate the majority of excitatory neurotransmission in the central nervous system. KARs modulate neuronal circuits and plasticity during development and are implicated in neurological disorders, including epilepsy, depression, schizophrenia, anxiety, and autism (Gangwar et al. 2024). Calcium-permeable KARs undergo ion channel block. Gangwar et al. 2024 presented closed-state structures of GluK2 KAR homotetramers in complex with ion channel blockers NpTx-8, PhTx-74, Kukoamine A, and spermine. Blockers reside inside the GluK2 ion channel pore, intracellular to the closed M3 helix bundle-crossing gate, with their hydrophobic heads filling the central cavity and positively charged polyamine tails spanning the selectivity filter. Molecular dynamics (MD) simulations of our structures illuminate interactions responsible for different affinity and binding poses of the blockers. The structures elucidate the trapping mechanism of KAR channel block and provide a template for designing new blockers that can selectively target calcium-permeable KARs in neuropathologies (Gangwar et al. 2024).

Accession Number:P42260
Protein Name:Glutamate receptor, ionotropic kainate 2
Length:908
Molecular Weight:102470.00
Species:Rattus norvegicus (Rat) [10116]
Number of TMSs:4
Location1 / Topology2 / Orientation3: Cell membrane1 / Multi-pass membrane protein2
Substrate ion

Cross database links:

DIP: DIP-29256N
Entrez Gene ID: 54257   
Pfam: PF01094    PF00060    PF10613   
KEGG: rno:54257   

Gene Ontology

GO:0030054 C:cell junction
GO:0032839 C:dendrite cytoplasm
GO:0043204 C:perikaryon
GO:0045211 C:postsynaptic membrane
GO:0043195 C:terminal button
GO:0005234 F:extracellular-glutamate-gated ion channel activity
GO:0015277 F:kainate selective glutamate receptor activity
GO:0030165 F:PDZ domain binding
GO:0042803 F:protein homodimerization activity
GO:0031624 F:ubiquitin conjugating enzyme binding
GO:0031625 F:ubiquitin protein ligase binding
GO:0051967 P:negative regulation of synaptic transmission, glutamatergic
GO:0051402 P:neuron apoptosis
GO:0043113 P:receptor clustering
GO:0046328 P:regulation of JNK cascade

References (10)

[1] “Cloning of a cDNA for a glutamate receptor subunit activated by kainate but not AMPA.”  Egebjerg J.et.al.   1648177
[2] “High-affinity kainate and domoate receptors in rat brain.”  Lomeli H.et.al.   1322826
[3] “Determinants of Ca2+ permeability in both TM1 and TM2 of high affinity kainate receptor channels: diversity by RNA editing.”  Koehler M.et.al.   7681676
[4] “The PDZ1 domain of SAP90. Characterization of structure and binding.”  Piserchio A.et.al.   11744724
[5] “Actinfilin is a Cul3 substrate adaptor, linking GluR6 kainate receptor subunits to the ubiquitin-proteasome pathway.”  Salinas G.D.et.al.   17062563
[6] “SUMOylation regulates kainate-receptor-mediated synaptic transmission.”  Martin S.et.al.   17486098
[7] “A transmembrane accessory subunit that modulates kainate-type glutamate receptors.”  Zhang W.et.al.   19217376
[8] “Crystal structures of the GluR5 and GluR6 ligand binding cores: molecular mechanisms underlying kainate receptor selectivity.”  Mayer M.L.et.al.   15721240
[9] “Structure of the kainate receptor subunit GluR6 agonist-binding domain complexed with domoic acid.”  Nanao M.H.et.al.   15677325
[10] “Conformational restriction blocks glutamate receptor desensitization.”  Weston M.C.et.al.   17115050
Structure:
1S50   1S7Y   1S9T   1SD3   1TT1   1YAE   2I0B   2I0C   2XXR   2XXT   [...more]

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MKIISPVLSN LVFSRSIKVL LCLLWIGYSQ GTTHVLRFGG IFEYVESGPM GAEELAFRFA 
61:	VNTINRNRTL LPNTTLTYDT QKINLYDSFE ASKKACDQLS LGVAAIFGPS HSSSANAVQS 
121:	ICNALGVPHI QTRWKHQVSD NKDSFYVSLY PDFSSLSRAI LDLVQFFKWK TVTVVYDDST 
181:	GLIRLQELIK APSRYNLRLK IRQLPADTKD AKPLLKEMKR GKEFHVIFDC SHEMAAGILK 
241:	QALAMGMMTE YYHYIFTTLD LFALDVEPYR YSGVNMTGFR ILNTENTQVS SIIEKWSMER 
301:	LQAPPKPDSG LLDGFMTTDA ALMYDAVHVV SVAVQQFPQM TVSSLQCNRH KPWRFGTRFM 
361:	SLIKEAHWEG LTGRITFNKT NGLRTDFDLD VISLKEEGLE KIGTWDPASG LNMTESQKGK 
421:	PANITDSLSN RSLIVTTILE EPYVLFKKSD KPLYGNDRFE GYCIDLLREL STILGFTYEI 
481:	RLVEDGKYGA QDDVNGQWNG MVRELIDHKA DLAVAPLAIT YVREKVIDFS KPFMTLGISI 
541:	LYRKPNGTNP GVFSFLNPLS PDIWMYILLA YLGVSCVLFV IARFSPYEWY NPHPCNPDSD 
601:	VVENNFTLLN SFWFGVGALM QQGSELMPKA LSTRIVGGIW WFFTLIIISS YTANLAAFLT 
661:	VERMESPIDS ADDLAKQTKI EYGAVEDGAT MTFFKKSKIS TYDKMWAFMS SRRQSVLVKS 
721:	NEEGIQRVLT SDYAFLMEST TIEFVTQRNC NLTQIGGLID SKGYGVGTPM GSPYRDKITI 
781:	AILQLQEEGK LHMMKEKWWR GNGCPEEESK EASALGVQNI GGIFIVLAAG LVLSVFVAVG 
841:	EFLYKSKKNA QLEKRSFCSA MVEELRMSLK CQRRLKHKPQ APVIVKTEEV INMHTFNDRR 
901:	LPGKETMA