HOMER1

Homer homolog 1 (Drosophila)

PDB rendering based on 1ddv.
Identifiers
Symbols HOMER1; HOMER; HOMER1A; HOMER1B; HOMER1C; SYN47; Ves-1
External IDs OMIM: 604798 MGI: 1347345 HomoloGene: 3155 GeneCards: HOMER1 Gene
RNA expression pattern
More reference expression data
Orthologs
Species Human Mouse
Entrez 9456 26556
Ensembl ENSG00000152413 ENSMUSG00000007617
UniProt Q86YM7 Q8C655
RefSeq (mRNA) NM_004272 NM_011982
RefSeq (protein) NP_004263 NP_036112
Location (UCSC) Chr 5:
78.67 – 78.81 Mb		 Chr 13:
94.07 – 94.17 Mb
PubMed search [1] [2]

Homer protein homolog 1 or Homer1 is a neuronal protein that in humans is encoded by the HOMER1 gene.[1][2][3] Other names are Vesl and PSD-Zip45.

Contents

Domain structure

Homer1 protein has with an N-terminal EVH1 domain, involved in protein interaction, and C-terminal coiled-coil domain involved in self association. It consists of two major splice variants, short-form (Homer1a) and long-form (Homer1b and c). Homer1a has only EVH1 domain and is monomeric while Homer1b and 1c have both EVH1 and coiled-coil domains and are tetrameric.[4][5] The coiled-coil can be further separated in to N-terminal half and C-terminal half. The N-terminal half of the coiled-coil domain is predicted to be a parallel dimer while the C-terminus half is a hybrid of dimeric and anti-parallel tetrameric coiled-coil. As a whole, long Homer is predicted to have a dumbbell-like structure where two pairs of EVH1 domains are located on two sides of long (~50 nm) coiled-coil domain.[5] Mammals have Homer2 and Homer3, in addition to Homer1, which have similar domain structure. They also have similar alternatively spliced forms.

Distribution

Homer1 is expressed widely in central nervous system as well as peripheral tissue including heart, kidney, ovary, testis, and skeletal muscle. Subcellularly in neurons, Homer1 is concentrated in postsynaptic structure and consist major part of postsynaptic density.

Functions

EVH1 domain interacts with PPXXF motif. This sequence motif exists in group 1 metabotrophic glutamate receptor (mGluR1 and mGluR5), IP3 receptors (IP3R), Shank, transient receptor potential canonical (TRPC) family channels, drebrin, oligophrenin, dynamin3, CENTG1, and ryanodin receptor.[1][3][6][7][8][9] Through its tetrameric structure, long forms of Homer (such as Homer1b and Homer1c) are proposed to cross link different proteins. For example, group 1 mGluR is crossed linked with its signaling downstream, IP3 receptor.[6] Also, through crosslinking another multimeric protein Shank, it is proposed to comprise a core of the postsynaptic density.[5]

Notably, the expression of Homer1a is induced by neuronal activity while that of Homer1b and 1c are constitutive. Thus Homer1a is classified as an immediate early gene. Homer1a, acts as a natural dominant negative form that blocks interaction between long-forms and their ligand proteins by competing with the EVH1 binding site on the ligand proteins. In this way, the short form of Homer uncouples mGluR signaling and also shrinks dendritic spine structure.[2][10] Therefore, the short form of Homer is considered to be a part of a mechanism of homeostatic plasticity that dampens the neuronal responsiveness when input activity is too high.

The coiled-coil domain is reported to interact with syntaxin13 and activated Cdc42. The interaction with Cdc42 inhibit the activity of Cdc42 to remodel dendritic spine structure.

See also

References

  1. ^ a b Shiraishi-Yamaguchi Y, Furuichi T (2007). "The Homer family proteins". Genome Biol. 8 (2): 206. doi:10.1186/gb-2007-8-2-206. PMC 1852408. PMID 17316461. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1852408. 
  2. ^ a b Tu JC, Xiao B, Yuan JP, Lanahan AA, Leoffert K, Li M, Linden DJ, Worley PF (Dec 1998). "Homer binds a novel proline-rich motif and links group 1 metabotropic glutamate receptors with IP3 receptors". Neuron 21 (4): 717–26. doi:10.1016/S0896-6273(00)80589-9. PMID 9808459. 
  3. ^ a b "Entrez Gene: HOMER1 homer homolog 1 (Drosophila)". http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=9456. 
  4. ^ Hayashi MK, Ames HM, Hayashi Y (Aug 2006). "Tetrameric hub structure of postsynaptic scaffolding protein homer". J Neurosci. 26 (33): 8492–501. doi:10.1523/JNEUROSCI.2731-06.2006. PMID 16914674. 
  5. ^ a b c Hayashi MK, Tang C, Verpelli C, Narayanan R, Stearns MH, Xu RM, Li H, Sala C, Hayashi Y (Apr 2009). "The postsynaptic density proteins Homer and Shank form a polymeric network structure". Cell 137 (1): 159–71. doi:10.1016/j.cell.2009.01.050. PMC 2680917. PMID 19345194. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2680917. 
  6. ^ a b Xiao B, Tu JC, Petralia RS, Yuan JP, Doan A, Breder CD, Ruggiero A, Lanahan AA, Wenthold RJ, Worley PF (Dec 1998). "Homer regulates the association of group 1 metabotropic glutamate receptors with multivalent complexes of homer-related, synaptic proteins". Neuron 21 (4): 707–16. doi:10.1016/S0896-6273(00)80588-7. PMID 9808458. 
  7. ^ Rong, Rong; Ahn Jee-Yin, Huang Honglian, Nagata Eiichiro, Kalman Daniel, Kapp Judith A, Tu Jiancheng, Worley Paul F, Snyder Solomon H, Ye Keqiang (Nov. 2003). "PI3 kinase enhancer-Homer complex couples mGluRI to PI3 kinase, preventing neuronal apoptosis". Nat. Neurosci. (United States) 6 (11): 1153–61. doi:10.1038/nn1134. ISSN 1097-6256. PMID 14528310. 
  8. ^ Hwang, Sung-Yong; Wei Jiao, Westhoff Jens H, Duncan R Scott, Ozawa Fumiko, Volpe Pompeo, Inokuchi Kaoru, Koulen Peter (Aug. 2003). "Differential functional interaction of two Vesl/Homer protein isoforms with ryanodine receptor type 1: a novel mechanism for control of intracellular calcium signaling". Cell Calcium (Scotland) 34 (2): 177–84. doi:10.1016/S0143-4160(03)00082-4. ISSN 0143-4160. PMID 12810060. 
  9. ^ Feng, Wei; Tu Jiancheng, Yang Tianzhong, Vernon Patty Shih, Allen Paul D, Worley Paul F, Pessah Isaac N (Nov. 2002). "Homer regulates gain of ryanodine receptor type 1 channel complex". J. Biol. Chem. (United States) 277 (47): 44722–30. doi:10.1074/jbc.M207675200. ISSN 0021-9258. PMID 12223488. 
  10. ^ Sala C, Futai K, Yamamoto K, Worley PF, Hayashi Y, Sheng M (Jul 2003). "Inhibition of dendritic spine morphogenesis and synaptic transmission by activity-inducible protein Homer1a". J Neurosci 23 (15): 6327–37. PMID 12867517. 

Further reading