glutamate receptor, ionotropic kainate 1; glutamate receptor 5; GluR-5; GluR5; excitatory amino acid receptor 3; EAA3 (GRIK1, GLUR5)

Function

• non NMDA glutamate receptor subunit
• binding of the excitatory neurotransmitter L-glutamate induces a conformation change, leading to the opening of the cation channel, & thereby converts the chemical signal to an electrical impulse
• the receptor then desensitizes rapidly & enters a transient inactive state, characterized by the presence of bound agonist
• may be involved in the transmission of light information from the retina to the hypothalamus
• receptor binds domoate > kainate > L-glutamate = quisqualate > CNQX = DNQX > AMPA > dihydrokainate > NMDA

Structure

• homotetramer or heterotetramer of pore-forming glutamate receptor subunits
• tetramers may be formed by the dimerization of dimers (probable)
• belongs to the glutamate-gated ion channel (TC 1.A.10) family

Compartment

• cell membrane
• cell junction, synapse, postsynaptic cell membrane

Alternative splicing

named isoforms=2 additional isoforms seem to exist

Expression

• most abundant in the cerebellum & the suprachiasmatic nuclei (SCN) of the hypothalamus
• expressed in motor neurons

Pathology

• mutations in GluR5 may be associated with familial ALS

Genetics

• RNA editing:
  • modified positions=636, partially edited
  • the unedited version (Q) assembles into a functional kainate-gated homomeric channel, whereas the edited version (R) is unable to produce channel activity when expressed alone
  • both edited & unedited versions can form functional channels with GRIK4 & GRIK5 (putative)

More general terms

• glutamate receptor beta
• phosphoprotein
• glycoprotein

Database

• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:2897
• OMIM: https://mirror.omim.org/entry/138245
• UniProt: http://www.uniprot.org/uniprot/P39086.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=2897