Glutamate receptor, ionotropic, delta 2, also known as GluD2, GluRδ2, or δ2, is a protein that in humans is encoded by the GRID2gene.[1][2] This protein together with GluD1 belongs to the delta receptor subtype of ionotropic glutamate receptors. They possess 14–24% sequencehomology with AMPA, kainate, and NMDA subunits, but, despite their name, do not actually bind glutamate or various other glutamate agonists.[3]
delta iGluRs have long been considered orphan receptors as their endogenousligand was unknown. They are now believed to bind glycine and D-serine but these do not result in channel opening.[4][5]
GluD2 induces synaptogenesis through interaction of its N-terminal domain with Cbln1, which in turn interacts with presynaptic neurexins, forming a bridge across cerebellar synapses.[7][8]
The main functions of GluD2 in synaptic plasticity are carried out by its intracellular C-terminus.[9] This is regulated by D-serine,[10] which binds to the ligand-binding domain and results in changes in the structure of GluD2 without opening the channel.[5] These changes may signal up to the N-terminal domain or down to the C-terminal domain to alter protein-protein interactions.
A heterozygous deletion in GRID2 in humans causes a complicated spastic paraplegia with ataxia, frontotemporal dementia, and lower motor neuron involvement[11] whereas a homozygous biallelic deletion leads to a syndrome of cerebellar ataxia with marked developmental delay, pyramidal tract involvement[12] and tonic upgaze,[13] that can be classified as an ataxia with oculomotor apraxia (AOA) and has been named spinocerebellar ataxia, autosomal recessive type 18 (SCAR18).
A gain of channel function, resulting from a point mutation in mouse GRID2, is associated with the phenotype named 'lurcher', which in the heterozygous state leads to ataxia and motor coordination deficits resulting from selective, cell-autonomous apoptosis of cerebellar Purkinje cells during postnatal development.[14][15] Mice homozygous for this mutation die shortly after birth from massive loss of mid- and hindbrain neurons during late embryogenesis.
↑Matsuda K, Yuzaki M (Mar 2012). "Cbln1 and the δ2 glutamate receptor--an orphan ligand and an orphan receptor find their partners". Cerebellum. 11 (1): 78–84. doi:10.1007/s12311-010-0186-5. PMID20535596.
↑Maier A, Klopocki E, Horn D, Tzschach A, Holm T, Meyer R, Meyer T (Feb 2014). "De novo partial deletion in GRID2 presenting with complicated spastic paraplegia". Muscle & Nerve. 49 (2): 289–92. doi:10.1002/mus.24096. PMID24122788.
↑Utine GE, Haliloğlu G, Salanci B, Çetinkaya A, Kiper PÖ, Alanay Y, Aktas D, Boduroğlu K, Alikaşifoğlu M (Jul 2013). "A homozygous deletion in GRID2 causes a human phenotype with cerebellar ataxia and atrophy". Journal of Child Neurology. 28 (7): 926–32. doi:10.1177/0883073813484967. PMID23611888.
↑Yue Z, Horton A, Bravin M, DeJager PL, Selimi F, Heintz N (Aug 2002). "A novel protein complex linking the delta 2 glutamate receptor and autophagy: implications for neurodegeneration in lurcher mice". Neuron. 35 (5): 921–33. doi:10.1016/S0896-6273(02)00861-9. PMID12372286.
↑ 18.018.1Kohda K, Kamiya Y, Matsuda S, Kato K, Umemori H, Yuzaki M (Jan 2003). "Heteromer formation of delta2 glutamate receptors with AMPA or kainate receptors". Brain Research. Molecular Brain Research. 110 (1): 27–37. doi:10.1016/S0169-328X(02)00561-2. PMID12573530.
↑Hironaka K, Umemori H, Tezuka T, Mishina M, Yamamoto T (May 2000). "The protein-tyrosine phosphatase PTPMEG interacts with glutamate receptor delta 2 and epsilon subunits". The Journal of Biological Chemistry. 275 (21): 16167–73. doi:10.1074/jbc.M909302199. PMID10748123.
Araki K, Meguro H, Kushiya E, Takayama C, Inoue Y, Mishina M (Dec 1993). "Selective expression of the glutamate receptor channel delta 2 subunit in cerebellar Purkinje cells". Biochemical and Biophysical Research Communications. 197 (3): 1267–76. doi:10.1006/bbrc.1993.2614. PMID7506541.
Hu W, Zuo J, De Jager PL, Heintz N (Jan 1998). "The human glutamate receptor delta 2 gene (GRID2) maps to chromosome 4q22". Genomics. 47 (1): 143–5. doi:10.1006/geno.1997.5108. PMID9465309.
Sanger Centre, The; Washington University Genome Sequencing Cente, The (Nov 1998). "Toward a complete human genome sequence". Genome Research. 8 (11): 1097–108. doi:10.1101/gr.8.11.1097. PMID9847074.
Roche KW, Ly CD, Petralia RS, Wang YX, McGee AW, Bredt DS, Wenthold RJ (May 1999). "Postsynaptic density-93 interacts with the delta2 glutamate receptor subunit at parallel fiber synapses". The Journal of Neuroscience. 19 (10): 3926–34. PMID10234023.
Hironaka K, Umemori H, Tezuka T, Mishina M, Yamamoto T (May 2000). "The protein-tyrosine phosphatase PTPMEG interacts with glutamate receptor delta 2 and epsilon subunits". The Journal of Biological Chemistry. 275 (21): 16167–73. doi:10.1074/jbc.M909302199. PMID10748123.
Miyagi Y, Yamashita T, Fukaya M, Sonoda T, Okuno T, Yamada K, Watanabe M, Nagashima Y, Aoki I, Okuda K, Mishina M, Kawamoto S (Feb 2002). "Delphilin: a novel PDZ and formin homology domain-containing protein that synaptically colocalizes and interacts with glutamate receptor delta 2 subunit". The Journal of Neuroscience. 22 (3): 803–14. PMID11826110.
Ly CD, Roche KW, Lee HK, Wenthold RJ (Feb 2002). "Identification of rat EMAP, a delta-glutamate receptor binding protein". Biochemical and Biophysical Research Communications. 291 (1): 85–90. doi:10.1006/bbrc.2002.6413. PMID11829466.
Yue Z, Horton A, Bravin M, DeJager PL, Selimi F, Heintz N (Aug 2002). "A novel protein complex linking the delta 2 glutamate receptor and autophagy: implications for neurodegeneration in lurcher mice". Neuron. 35 (5): 921–33. doi:10.1016/S0896-6273(02)00861-9. PMID12372286.
Kohda K, Kamiya Y, Matsuda S, Kato K, Umemori H, Yuzaki M (Jan 2003). "Heteromer formation of delta2 glutamate receptors with AMPA or kainate receptors". Brain Research. Molecular Brain Research. 110 (1): 27–37. doi:10.1016/S0169-328X(02)00561-2. PMID12573530.
Yap CC, Muto Y, Kishida H, Hashikawa T, Yano R (Feb 2003). "PKC regulates the delta2 glutamate receptor interaction with S-SCAM/MAGI-2 protein". Biochemical and Biophysical Research Communications. 301 (4): 1122–8. doi:10.1016/S0006-291X(03)00070-6. PMID12589829.
Sonoda T, Mochizuki C, Yamashita T, Watanabe-Kaneko K, Miyagi Y, Shigeri Y, Yazama F, Okuda K, Kawamoto S (Nov 2006). "Binding of glutamate receptor delta2 to its scaffold protein, Delphilin, is regulated by PKA". Biochemical and Biophysical Research Communications. 350 (3): 748–52. doi:10.1016/j.bbrc.2006.09.109. PMID17027646.