Biology:OPN5

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Short description: Protein-coding gene in the species Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

Opsin-5, also known as G-protein coupled receptor 136 or neuropsin is a protein that in humans is encoded by the OPN5 gene. Opsin-5 is a member of the opsin subfamily of the G protein-coupled receptors.[1][2][3] It is a photoreceptor protein sensitive to ultraviolet (UV) light. The OPN5 gene was discovered in mouse and human genomes and its mRNA expression was also found in neural tissues. Neuropsin is bistable at 0 °C and activates a UV-sensitive, heterotrimeric G protein Gi-mediated pathway in mammalian and avian tissues.[4][5]

Function

Human neuropsin is expressed in the eye, brain, testes, and spinal cord. Neuropsin belongs to the seven-exon subfamily of mammalian opsin genes that includes peropsin (RRH) and retinal G protein coupled receptor (RGR). Neuropsin has different isoforms created by alternative splicing.[3]

Photochemistry

When reconstituted with 11-cis-retinal, mouse and human neuropsins absorb maximally at 380 nm. When illuminated these neuropsins are converted into blue-absorbing photoproducts (470 nm), which are stable in the dark. The photoproducts are converted back to the UV-absorbing form, when they are illuminated with orange light (> 520 nm).[4]

Species distribution

Neuropsins are known from echinoderms,[6] annelids, arthropods, brachiopods, tardigrades, mollusks, and most are known from craniates.[7] The craniates are the taxon that contains mammals and with them humans. However, neuropsin orthologs have only been experimentally verified in a small number of animals, among them human, mouse (Mus musculus),[1] chicken (Gallus gallus domesticus),[5][8] the Japanese quail (Coturnix japonica),[9] the European brittle star Amphiura filiformis (related to starfish),[6] the tardigrade water bear (Hypsibius dujardini),[10] and the tadpole of Xenopus laevis.[11]

Searches of publicly available databases of genetic sequences have found putative neuropsin orthologs in both major branches of Bilateria: protostomes and deuterostomes. Among protostomes, putative neuropsins have been found in the molluscs owl limpet (Lottia gigantea) (a species of sea snail) and Pacific oyster (Crassostrea gigas), in the water flea (Daphnia pulex) (an arthropod), and in the annelid worm Capitella teleta.[10]

Phylogeny

The neuropsins are one of three subgroups of the tetraopsins (also known as RGR/Go or Group 4 opsins). The other groups are the chromopsins and the Go-opsins. The tetraopsins are one of the five major groups of the animal opsins, also known as type 2 opsins). The other groups are the ciliary opsins (c-opsins, cilopsins), the rhabdomeric opsins (r-opsins, rhabopsins), the xenopsins, and the nessopsins. Four of these subclades occur in Bilateria (all but the nessopsins).[7][12] However, the bilaterian clades constitute a paraphyletic taxon without the opsins from the cnidarians.[7][12][13][14]

The phylogenetic relationship of the neuropsins to the other opsins
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    Phylogenetic reconstruction of the opsins. The outgroup contains other G protein-coupled receptors. The frame highlights the tetraopsins, which are expanded in the next image.

  • Phylogenetic reconstruction of the tetraopsins. The outgroup contains other G protein-coupled receptors including the other opsins. The frame highlights the neuropsins, which are expanded in the next image.

In the phylogeny above, Each clade contains sequences from opsins and other G protein-coupled receptors. The number of sequences and two pie charts are shown next to the clade. The first pie chart shows the percentage of a certain amino acid at the position in the sequences corresponding to position 296 in cattle rhodopsin. The amino acids are color-coded. The colors are red for lysine (K), purple for glutamic acid (E), dark and mid-gray for other amino acids, and light gray for sequences that have no data at that position. The second pie chart gives the taxon composition for each clade, green stands for craniates, dark green for cephalochordates, mid green for echinoderms, pale pink for annelids, dark blue for arthropods, light blue for mollusks, and purple for cnidarians. The branches branches to the clades have pie charts, which give support values for the branches. The values are from right to left SH-aLRT/aBayes/UFBoot. The branches are considered supported when SH-aLRT ≥ 80%, aBayes ≥ 0.95, and UFBoot ≥ 95%. If a support value is above its threshold the pie chart is black otherwise gray.[7]

References

  1. ↑ 1.0 1.1 "Neuropsin (Opn5): a novel opsin identified in mammalian neural tissue". FEBS Letters 554 (3): 410–6. Nov 2003. doi:10.1016/S0014-5793(03)01212-2. PMID 14623103. 
  2. ↑ "Seven evolutionarily conserved human rhodopsin G protein-coupled receptors lacking close relatives". FEBS Letters 554 (3): 381–8. Nov 2003. doi:10.1016/S0014-5793(03)01196-7. PMID 14623098. 
  3. ↑ 3.0 3.1 "Entrez Gene: OPN5 opsin 5". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=221391. 
  4. ↑ 4.0 4.1 "UV-sensitive photoreceptor protein OPN5 in humans and mice". PLOS ONE 6 (10): e26388. 2011. doi:10.1371/journal.pone.0026388. PMID 22043319. Bibcode: 2011PLoSO...626388K. 
  5. ↑ 5.0 5.1 "Opn5 is a UV-sensitive bistable pigment that couples with Gi subtype of G protein". Proceedings of the National Academy of Sciences of the United States of America 107 (51): 22084–22089. December 2010. doi:10.1073/pnas.1012498107. PMID 21135214. Bibcode: 2010PNAS..10722084Y. 
  6. ↑ 6.0 6.1 "High opsin diversity in a non-visual infaunal brittle star". BMC Genomics 15 (1): 1035. 2014. doi:10.1186/1471-2164-15-1035. PMID 25429842. 
  7. ↑ 7.0 7.1 7.2 7.3 "The Gluopsins: Opsins without the Retinal Binding Lysine". Cells 11 (15): 2441. August 2022. doi:10.3390/cells11152441. PMID 35954284.  CC-BY icon.svg Material was copied and adapted from this source, which is available under a Creative Commons Attribution 4.0 International License.
  8. ↑ "Expression patterns of the opsin 5-related genes in the developing chicken retina". Developmental Dynamics 237 (7): 1910–22. Jul 2008. doi:10.1002/dvdy.21611. PMID 18570255. 
  9. ↑ "A mammalian neural tissue opsin (Opsin 5) is a deep brain photoreceptor in birds". Proceedings of the National Academy of Sciences of the United States of America 107 (34): 15264–8. Aug 2010. doi:10.1073/pnas.1006393107. PMID 20679218. Bibcode: 2010PNAS..10715264N. 
  10. ↑ 10.0 10.1 "Analysis of the opsin repertoire in the tardigrade Hypsibius dujardini provides insights into the evolution of opsin genes in panarthropoda". Genome Biology and Evolution 6 (9): 2380–91. Sep 2014. doi:10.1093/gbe/evu193. PMID 25193307. 
  11. ↑ "Deep-brain photoreception links luminance detection to motor output in Xenopus frog tadpoles". Proceedings of the National Academy of Sciences of the United States of America 113 (21): 6053–6058. May 2016. doi:10.1073/pnas.1515516113. PMID 27166423. Bibcode: 2016PNAS..113.6053C. 
  12. ↑ 12.0 12.1 "The last common ancestor of most bilaterian animals possessed at least 9 opsins". Genome Biology and Evolution: evw248. 26 October 2016. doi:10.1093/gbe/evw248. PMID 27797948. 
  13. ↑ "Shedding new light on opsin evolution". Proceedings. Biological Sciences 279 (1726): 3–14. January 2012. doi:10.1098/rspb.2011.1819. PMID 22012981. 
  14. ↑ "Cubozoan genome illuminates functional diversification of opsins and photoreceptor evolution". Scientific Reports 5: 11885. July 2015. doi:10.1038/srep11885. PMID 26154478. Bibcode: 2015NatSR...511885L. 

Further reading

This article incorporates text from the United States National Library of Medicine, which is in the public domain.




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