Transient receptor potential calcium channel family

Last updated
TRPA1 ion channel
Identifiers
SymbolTRP-CC
Pfam PF00520
InterPro IPR005821
SMART SM00248
PROSITE PS50088
TCDB 1.A.4
OPM superfamily 8
OPM protein 3j9p
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary
PDB 3J9P

The transient receptor potential Ca2+ channel (TRP-CC) family (TC# 1.A.4) is a member of the voltage-gated ion channel (VIC) superfamily and consists of cation channels conserved from worms to humans. [1] The TRP-CC family also consists of seven subfamilies (TRPC, TRPV, TRPM, TRPN, TRPA, TRPP, and TRPML) based on their amino acid sequence homology:

Contents

  1. the canonical or classic TRPs,
  2. the vanilloid receptor TRPs,
  3. the melastatin or long TRPs,
  4. ankyrin (whose only member is the transmembrane protein 1 [TRPA1])
  5. TRPN after the nonmechanoreceptor potential C (nonpC), and the more distant cousins,
  6. the polycystins
  7. and mucolipins.

A representative list of members belonging to the TRP-CC family can be found in the Transporter Classification Database.

Function

Members of the TRP-CC family are characterized as cellular sensors with polymodal activation and gating properties. Many TRP channels are activated by a variety of different stimuli and function as signal integrators. [2] [3] [4] These mammalian proteins have been tabulated revealing their accepted designations, activators and inhibitors, putative interacting proteins and proposed functions. [5] The founding members of the TRP superfamily are the TRPC (TRP canonical) channels, which can be activated following the stimulation of phospholipase C and/or depletion of internal calcium stores. [3] However, the precise mechanisms leading to TRPC activation remain unclear. TRPC channels regulate nicotine-dependent behavior. [6]

One member of the TRP-CC family, TRP-PLIK (1862 aas; AF346629), has been implicated in the regulation of cell division. It has an N-terminal TRP-CC-like sequence and a C-terminal protein kinase-like sequence. It was shown to autophosphorylate and exhibits an ATP phosphorylation-dependent, non-selective, Ca2+-permeable, outward rectifying conductance. [7] Another long homologue, Melastatin, is associated with melanocytic tumor progression whereas another homologue, MTR1, is associated with Beckwith-Wiedemann syndrome and a predisposition for neoplasia. Each of these proteins may be present in the cell as several splice variants.

The ability to detect variations in humidity is critical for many animals. Birds, reptiles and insects all show preferences for specific humidities that influence their mating, reproduction and geographic distribution. Because of their large surface area to volume ratio, insects are particularly sensitive to humidity, and its detection can influence their survival. Two types of hygroreceptors exist in insects: one responds to an increase (moist receptor) and the other to a reduction (dry receptor) in humidity. Although previous data indicated that mechanosensation might contribute to hygrosensation, the cellular basis of hygrosensation and the genes involved in detecting humidity remain unknown. To understand better the molecular bases of humidity sensing, investigated several genes encoding channels associated with mechanosensation, thermosensing or water transport. [8]

Transport reaction

The generalized transport reaction catalyzed by TRP-CC family members is:

Ca2+ (out) ⇌ Ca2+ (in)

or

C+ and Ca2+ (out) ⇌ C+ and Ca2+ (in).

Anesthesia

Most local anaesthetics used clinically are relatively hydrophobic molecules that gain access to their blocking site on the sodium channel by diffusing into or through the cell membrane. These anaesthetics block sodium channels and the excitability of neurons. Binshtok et al. (2007) tested the possibility that the excitability of primary sensory nociceptor (pain-sensing) neurons could be blocked by introducing the charged, membrane-impermeant lidocaine derivative QX-314 through the pore of the noxious-heat-sensitive TRPV1 channel (TC #1.A.4.2.1). [9] They found that charged sodium-channel blockers can be targeted into nociceptors by the application of TRPV1 agonists to produce a pain-specific local anaesthesia. QX-314 applied externally had no effect on the activity of sodium channels in small sensory neurons when applied alone, but when applied in the presence of the TRPV1 agonist capsaicin, QX-314 blocked sodium channels and inhibited excitability. [9]

Structure

Members of the VIC (TC# 1.A.1), RIR-CaC (TC# 2.A.3) and TRP-CC (TC# 1.A.4) families have similar transmembrane domain structures, but very different cytosolic domain structures. [10]

The proteins of the TRP-CC family exhibit the same topological organization with a probable KscA-type 3-dimensional structure. [11] [12] They consist of about 700-800 (VR1, SIC or ECaC) or 1300 (TRP proteins) amino acyl residues (aas) with six transmembrane spanners (TMSs) as well as a short hydrophobic 'loop' region between TMSs 5 and 6. This loop region may dip into the membrane and contribute to the ion permeation pathway. [13]

All members of the vanilloid family of TRP channels (TRPV) possess an N-terminal ankyrin repeat domain (ARD), which regulates calcium uptake and homeostasis. It is essential for channel assembly and regulation. The 1.7 Å crystal structure of the TRPV6-ARD revealed conserved structural elements unique to the ARDs of TRPV proteins. First, a large twist between the fourth and fifth repeats is induced by residues conserved in all TRPV ARDs. Second, the third finger loop is the most variable region in sequence, length and conformation. In TRPV6, a number of putative regulatory phosphorylation sites map to the base of this third finger. The TRPV6-ARD does not assemble as a tetramer and is monomeric in solution. [14] Voltage sensing in thermo-TRP channels has been reviewed by Brauchi et al. [15]

TRP channels have six TMS helices. [16] These channels can be classified to six groups: TRPV (1-6), TRPM (1-8), TRPC (1-7), TRPA1, TRPP (1-3), and TRPML (1-3). TRP channels are involved in intracellular calcium mobilization and reabsorption. TRP channelopathies are involved in neurodegenerative disorders, diabetes mellitus, bowel diseases, epilepsy and cancer. Some TRP receptors act as molecular thermometers of the body. Some of them also play a role in pain and nociception. [16]

Crystal structures

There are several crystal structures available for members of the TRP-CC family. Some of these include:

VR1: PDB: 2NYJ , 2NYN , 3J5P , 3J5Q , 3J5R

TRPV2 aka VRL-1: PDB: 2F37

Transient receptor potential cation channel subfamily A member 1: PDB: 3J9P

See also

Related Research Articles

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<span class="mw-page-title-main">Thermoreceptor</span> Receptive portion of a sensory neuron

A thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range. In the mammalian peripheral nervous system, warmth receptors are thought to be unmyelinated C-fibres, while those responding to cold have both C-fibers and thinly myelinated A delta fibers. The adequate stimulus for a warm receptor is warming, which results in an increase in their action potential discharge rate. Cooling results in a decrease in warm receptor discharge rate. For cold receptors their firing rate increases during cooling and decreases during warming. Some cold receptors also respond with a brief action potential discharge to high temperatures, i.e. typically above 45 °C, and this is known as a paradoxical response to heat. The mechanism responsible for this behavior has not been determined.

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.

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<span class="mw-page-title-main">TRPV1</span> Human protein for regulating body temperature

The transient receptor potential cation channel subfamily V member 1 (TRPV1), also known as the capsaicin receptor and the vanilloid receptor 1, is a protein that, in humans, is encoded by the TRPV1 gene. It was the first isolated member of the transient receptor potential vanilloid receptor proteins that in turn are a sub-family of the transient receptor potential protein group. This protein is a member of the TRPV group of transient receptor potential family of ion channels. And a receptor being clearly present in bacteria, the oldest organisms on Earth known to express phosphatidylethanolamine, the precursor to endocannabinoids, in their cytoplasmic membranes, and fatty acid metabolites with affinity for this CB receptor are produced by cyanobacteria, which diverged from eukaryotes at least 2000 million years ago (MYA).

TRPC is a family of transient receptor potential cation channels in animals.

<span class="mw-page-title-main">TRPV</span> Subgroup of TRP cation channels named after the vanilloid receptor

TRPV is a family of transient receptor potential cation channels in animals. All TRPVs are highly calcium selective.

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<span class="mw-page-title-main">TRPC1</span> Protein and coding gene in humans

Transient receptor potential canonical 1 (TRPC1) is a protein that in humans is encoded by the TRPC1 gene.

<span class="mw-page-title-main">TRPC4</span> Protein and coding gene in humans

The short transient receptor potential channel 4 (TrpC4), also known as Trp-related protein 4, is a protein that in humans is encoded by the TRPC4 gene.

<span class="mw-page-title-main">TRPM5</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">TRPV2</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">TRPM8</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">TRPM3</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">TRPV5</span> Protein-coding gene in the species Homo sapiens

Transient receptor potential cation channel subfamily V member 5 is a calcium channel protein that in humans is encoded by the TRPV5 gene.

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References

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