Retinal G protein coupled receptor

Last updated

RGR
Identifiers
Aliases RGR , RP44, Retinal G protein coupled receptor
External IDs OMIM: 600342; MGI: 1929473; HomoloGene: 37709; GeneCards: RGR; OMA:RGR - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001012720
NM_001012722
NM_002921

NM_001301692
NM_001301694
NM_021340

RefSeq (protein)

NP_001012738
NP_001012740
NP_002912

NP_001288621
NP_001288623
NP_067315

Location (UCSC) Chr 10: 84.23 – 84.26 Mb Chr 14: 36.76 – 36.77 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

RPE-retinal G protein-coupled receptor also known as RGR-opsin is a protein that in humans is encoded by the RGR gene. [5] [6] RGR-opsin is a member of the rhodopsin-like receptor subfamily of GPCR. Like other opsins which bind retinaldehyde, it contains a conserved lysine residue in the seventh transmembrane domain. [7] [8] RGR-opsin comes in different isoforms produced by alternative splicing. [6]

Contents

Function

RGR-opsin preferentially binds all-trans-retinal, [8] which is the dominant form in the dark adapted retina, upon light exposure it is isomerized to 11-cis-retinal. [9] Therefore, RGR-opsin presumably acts as a photoisomerase to convert all-trans-retinal to 11-cis-retinal, similar to retinochrome in invertebrates. 11-cis-retinal is isomerized back within rhodopsin and the iodopsins in the rods and cones of the retina. RGR-opsin is exclusively expressed in tissue close to the rods and cones, the retinal pigment epithelium (RPE) and Müller cells. [7]

Phylogeny

The RGR-opsins are restricted to the echinoderms, the hemichordates the craniates. [10] The craniates are the taxon that contains mammals and with them humans. The RGR-opsins are one of the seven subgroups of the chromopsins. The other groups are the peropsins, the retinochromes, the nemopsins, the astropsins, the varropsins, and the gluopsins. [10] The chromopsins are one of three subgroups of the tetraopsins (also known as RGR/Go or Group 4 opsins). The other groups are the neuropsins 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). [10] [11] However, the bilaterian clades constitute a paraphyletic taxon without the opsins from the cnidarians. [10] [11] [12] [13]

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), orange for arginine (R), 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, brown for nematodes, pale pink for annelids, dark blue for arthropods, light blue for mollusks, and purple for cnidarians. The 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. [10]

Clinical significance

RGR-opsin may be associated with autosomal recessive and autosomal dominant retinitis pigmentosa (arRP and adRP, respectively). [14] [6]

Interactions

RGR-opsin has been shown to interact with KIAA1279. [15]

Related Research Articles

<span class="mw-page-title-main">Rhodopsin</span> Light-sensitive receptor protein

Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene and a G-protein-coupled receptor (GPCR). It is the opsin of the rod cells in the retina and a light-sensitive receptor protein that triggers visual phototransduction in rods. Rhodopsin mediates dim light vision and thus is extremely sensitive to light. When rhodopsin is exposed to light, it immediately photobleaches. In humans, it is regenerated fully in about 30 minutes, after which the rods are more sensitive. Defects in the rhodopsin gene cause eye diseases such as retinitis pigmentosa and congenital stationary night blindness.

<span class="mw-page-title-main">Retinitis pigmentosa</span> Gradual retinal degeneration leading to progressive sight loss

Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision. As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon. Onset of symptoms is generally gradual and often begins in childhood.

<span class="mw-page-title-main">Opsin</span> Class of light-sensitive proteins

Animal opsins are G-protein-coupled receptors and a group of proteins made light-sensitive via a chromophore, typically retinal. When bound to retinal, opsins become retinylidene proteins, but are usually still called opsins regardless. Most prominently, they are found in photoreceptor cells of the retina. Five classical groups of opsins are involved in vision, mediating the conversion of a photon of light into an electrochemical signal, the first step in the visual transduction cascade. Another opsin found in the mammalian retina, melanopsin, is involved in circadian rhythms and pupillary reflex but not in vision. Humans have in total nine opsins. Beside vision and light perception, opsins may also sense temperature, sound, or chemicals.

Rhodopsin kinase is a serine/threonine-specific protein kinase involved in phototransduction. This enzyme catalyses the following chemical reaction:

The visual cycle is a process in the retina that replenishes the molecule retinal for its use in vision. Retinal is the chromophore of most visual opsins, meaning it captures the photons to begin the phototransduction cascade. When the photon is absorbed, the 11-cis retinal photoisomerizes into all-trans retinal as it is ejected from the opsin protein. Each molecule of retinal must travel from the photoreceptor cell to the RPE and back in order to be refreshed and combined with another opsin. This closed enzymatic pathway of 11-cis retinal is sometimes called Wald's visual cycle after George Wald (1906–1997), who received the Nobel Prize in 1967 for his work towards its discovery.

<span class="mw-page-title-main">Photoreceptor cell-specific nuclear receptor</span> Protein-coding gene in the species Homo sapiens

The photoreceptor cell-specific nuclear receptor (PNR), also known as NR2E3, is a protein that in humans is encoded by the NR2E3 gene. PNR is a member of the nuclear receptor super family of intracellular transcription factors.

<span class="mw-page-title-main">RRH</span> Protein-coding gene in the species Homo sapiens

Peropsin, a visual pigment-like receptor, is a protein that in humans is encoded by the RRH gene. It belongs like other animal opsins to the G protein-coupled receptors. Even so, the first peropsins were already discovered in mice and humans in 1997, not much is known about them.

<span class="mw-page-title-main">OPN5</span> Protein-coding gene in the species Homo sapiens

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. 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.

<span class="mw-page-title-main">OPN1LW</span> Protein-coding gene in humans

OPN1LW is a gene on the X chromosome that encodes for long wave sensitive (LWS) opsin, or red cone photopigment. It is responsible for perception of visible light in the yellow-green range on the visible spectrum. The gene contains 6 exons with variability that induces shifts in the spectral range. OPN1LW is subject to homologous recombination with OPN1MW, as the two have very similar sequences. These recombinations can lead to various vision problems, such as red-green colourblindness and blue monochromacy. The protein encoded is a G-protein coupled receptor with embedded 11-cis-retinal, whose light excitation causes a cis-trans conformational change that begins the process of chemical signalling to the brain.

<span class="mw-page-title-main">Peripherin 2</span> Protein-coding gene in the species Homo sapiens

Peripherin-2 is a protein, that in humans is encoded by the PRPH2 gene. Peripherin-2 is found in the rod and cone cells of the retina of the eye. Defects in this protein result in one form of retinitis pigmentosa, an incurable blindness.

<span class="mw-page-title-main">RPE65</span> Protein-coding gene in humans

Retinal pigment epithelium-specific 65 kDa protein is a retinoid isomerohydrolase enzyme of the vertebrate visual cycle. RPE65 is expressed in the retinal pigment epithelium and is responsible for the conversion of all-trans-retinyl esters to 11-cis-retinol during phototransduction. 11-cis-retinol is then used in visual pigment regeneration in photoreceptor cells. RPE65 belongs to the carotenoid oxygenase family of enzymes.

<span class="mw-page-title-main">Retinaldehyde-binding protein 1</span> Protein-coding gene in the species Homo sapiens

Retinaldehyde-binding protein 1 (RLBP1) also known as cellular retinaldehyde-binding protein (CRALBP) is a 36-kD water-soluble protein that in humans is encoded by the RLBP1 gene.

<span class="mw-page-title-main">RDH5</span> Protein-coding gene in humans

11-cis retinol dehydrogenase is an enzyme that in humans is encoded by the RDH5 gene.

<span class="mw-page-title-main">CRB1</span> Protein-coding gene in the species Homo sapiens

Crumbs homolog 1 is a protein that in humans is encoded by the CRB1 gene.

<span class="mw-page-title-main">MERTK</span> Protein-coding gene in humans

Proto-oncogene tyrosine-protein kinase MER is an enzyme that in humans is encoded by the MERTK gene.

<span class="mw-page-title-main">RP1</span> Protein-coding gene in humans

Oxygen-regulated protein 1 also known as retinitis pigmentosa 1 protein (RP1) is a protein that in humans is encoded by the RP1 gene.

<span class="mw-page-title-main">Retinal degeneration (rhodopsin mutation)</span> Retinopathy

Retinal degeneration is a retinopathy which consists in the deterioration of the retina caused by the progressive death of its cells. There are several reasons for retinal degeneration, including artery or vein occlusion, diabetic retinopathy, R.L.F./R.O.P., or disease. These may present in many different ways such as impaired vision, night blindness, retinal detachment, light sensitivity, tunnel vision, and loss of peripheral vision to total loss of vision. Of the retinal degenerative diseases retinitis pigmentosa (RP) is a very important example.

Retinal gene therapy holds a promise in treating different forms of non-inherited and inherited blindness.

Nematode chemoreceptors are chemoreceptors of nematodes. Animals recognise a wide variety of chemicals using their senses of taste and smell. The nematode Caenorhabditis elegans has only 14 types of chemosensory neuron, yet is able to respond to dozens of chemicals because each neuron detects several stimuli. More than 40 highly divergent transmembrane proteins that could contribute to this functional diversity have been described. Most of the candidate receptor genes are in clusters of similar genes; 11 of these appear to be expressed in small subsets of chemosensory neurons. A single type of neuron can potentially express at least 4 different receptor genes. Some of these might encode receptors for water-soluble attractants, repellents and pheromones, which are divergent members of the G-protein-coupled receptor family. Sequences of the Sra family of C. elegans receptor-like proteins contain 6-7 hydrophobic, putative transmembrane, regions. These can be distinguished from other 7TM proteins by their own characteristic TM signatures.

<span class="mw-page-title-main">Vertebrate visual opsin</span>

Vertebrate visual opsins are a subclass of ciliary opsins and mediate vision in vertebrates. They include the opsins in human rod and cone cells. They are often abbreviated to opsin, as they were the first opsins discovered and are still the most widely studied opsins.

References

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Further reading

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