Transient receptor potential cation channel subfamily M member 1 is a protein that in humans is encoded by the TRPM1 gene. [5] [6] [7]
Transient receptor potential cation channel subfamily M member 1 is a protein that in humans is encoded by the TRPM1 gene. [5] [6] [7]
The protein encoded by this gene is a member of the transient receptor potential (TRP) family of non-selective cation channels. It is expressed in the retina, in a subset of bipolar cells termed ON bipolar cells. [8] [9] These cells form synapses with either rods or cones, collecting signals from them. In the dark, the signal arrives in the form of the neurotransmitter glutamate, which is detected by a G protein-coupled receptor (GPCR) signal transduction cascade. Detection of glutamate by the GPCR Metabotropic glutamate receptor 6 results in closing of the TRPM1 channel. At the onset of light, glutamate release is halted and mGluR6 is deactivated; this results in opening of the TRPM1 channel, influx of sodium and calcium, and depolarization of the bipolar cell. [10] [11]
In addition to the retina, TRPM1 is also expressed in melanocytes, which are melanin-producing cells in the skin. The expression of TRPM1 is inversely correlated with melanoma aggressiveness, suggesting that it might suppress melanoma metastasis. [12] However, subsequent work showed that a microRNA located in an intron of the TRPM1 gene, rather than the TRPM1 protein itself, is responsible for the tumor suppressor function. [13] [14] The expression of both TRPM1 and the microRNA are regulated by the Microphthalmia-associated transcription factor. [15] [16] [17] [13]
Mutations in TRPM1 are associated with congenital stationary night blindness in humans [18] [19] [20] [21] and coat spotting patterns in Appaloosa horses. [22]
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.
Transient receptor potential channels are a group of ion channels located mostly on the plasma membrane of numerous animal cell types. Most of these are grouped into two broad groups: Group 1 includes TRPC, TRPV, TRPVL, TRPM, TRPS, TRPN, and TRPA. Group 2 consists of TRPP and TRPML. Other less-well categorized TRP channels exist, including yeast channels and a number of Group 1 and Group 2 channels present in non-animals. Many of these channels mediate a variety of sensations such as pain, temperature, different kinds of tastes, pressure, and vision. In the body, some TRP channels are thought to behave like microscopic thermometers and used in animals to sense hot or cold. Some TRP channels are activated by molecules found in spices like garlic (allicin), chili pepper (capsaicin), wasabi ; others are activated by menthol, camphor, peppermint, and cooling agents; yet others are activated by molecules found in cannabis or stevia. Some act as sensors of osmotic pressure, volume, stretch, and vibration. Most of the channels are activated or inhibited by signaling lipids and contribute to a family of lipid-gated ion channels.
Nyctalopia, also called night-blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition. It can be described as insufficient adaptation to darkness.
Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the MITF gene.
Congenital stationary night blindness (CSNB) is a rare non-progressive retinal disorder. People with CSNB often have difficulty adapting to low light situations due to impaired photoreceptor transmission. These patients may also have reduced visual acuity, myopia, nystagmus, and strabismus. CSNB has two forms -- complete, also known as type-1 (CSNB1), and incomplete, also known as type-2 (CSNB2), which are distinguished by the involvement of different retinal pathways. In CSNB1, downstream neurons called bipolar cells are unable to detect neurotransmission from photoreceptor cells. CSNB1 can be caused by mutations in various genes involved in neurotransmitter detection, including NYX, GRM6, and TRPM1. In CSNB2, the photoreceptors themselves have impaired neurotransmission function; this is caused primarily by mutations in the gene CACNA1F, which encodes a voltage-gated calcium channel important for neurotransmitter release.
Rhodopsin kinase is a serine/threonine-specific protein kinase involved in phototransduction. This enzyme catalyses the following chemical reaction:
TRPM is a family of transient receptor potential ion channels. Functional TRPM channels are believed to form tetramers. The TRPM family consists of eight different channels, TRPM1–TRPM8.
Transient receptor potential cation channel, subfamily M, member 2, also known as TRPM2, is a protein that in humans is encoded by the TRPM2 gene.
Transient receptor potential cation channel subfamily M member 5 (TRPM5), also known as long transient receptor potential channel 5 is a protein that in humans is encoded by the TRPM5 gene.
Transient receptor potential cation channel subfamily M member 4 (hTRPM4), also known as melastatin-4, is a protein that in humans is encoded by the TRPM4 gene.
Transient receptor potential cation channel subfamily M (melastatin) member 8 (TRPM8), also known as the cold and menthol receptor 1 (CMR1), is a protein that in humans is encoded by the TRPM8 gene. The TRPM8 channel is the primary molecular transducer of cold somatosensation in humans. In addition, mints can desensitize a region through the activation of TRPM8 receptors.
Transient receptor potential cation channel subfamily M member 3 is a protein that in humans is encoded by the TRPM3 gene.
Transient receptor potential cation channel, subfamily M, member 7, also known as TRPM7, is a human gene encoding a protein of the same name.
Probable G-protein coupled receptor 179 is a protein that in humans is encoded by the GPR179 gene.
Glutamate receptor, metabotropic 6, also known as GRM6 or mGluR6, is a protein which in humans is encoded by the GRM6 gene.
Taste receptor type 1 member 1 is a protein that in humans is encoded by the TAS1R1 gene.
Cav1.4 also known as the calcium channel, voltage-dependent, L type, alpha 1F subunit (CACNA1F), is a human gene.
Nyctalopin is a protein located on the surface of photoreceptor-to-ON bipolar cell synapse in the retina. It is composed of 481 amino acids. and is encoded in human by the NYX gene. This gene is found on the chromosome X and has two exons. This protein is a leucine-rich proteoglycan which is expressed in the eye, spleen and brain in mice. Mutations in this gene cause congenital stationary night blindness in humans (CSNB). which is a stable retinal disorder. The consequence of this mutation results in an abnormal night vision. Nyctalopin is critical due to the fact that it generates a depolarizing bipolar cell response due to the mutation on the NYX gene. Most of the time, CSNB are associated to hygh myopia which is the result of a mutation on the same gene. Several mutations can occur on the NYX gene resulting on many form of night blindness in humans. Some studies show that these mutations are more present in Asian population than in Caucasian population. A mouse strain called nob carries a spontaneous mutation leading to a frameshift in this gene. These mice are used as an animal model for congenital stationary night blindness.
Ocular albinism type 1(OA1), is the most common type of ocular albinism, with a prevalence rate of 1:50,000. It is an inheritable classical Mendelian type X-linked recessive disorder wherein the retinal pigment epithelium lacks pigment while hair and skin appear normal. Since it is usually an X-linked disorder, it occurs mostly in males, while females are carriers unless they are homozygous. About 60 missense and nonsense mutations, insertions, and deletions have been identified in Oa1. Mutations in OA1 have been linked to defective glycosylation and thus improper intracellular transportation.
Ononetin is a natural product from the deoxybenzoin group, which is found in the Russian traditional medicine plant Ononis spinosa. It acts as an inhibitor of the transient receptor potential ion channel TRPM3 and has analgesic effects in animal studies, as well as being used for research into the role of TRPM3 in the immune system dysfunction associated with chronic fatigue syndrome.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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