Biology:Transient receptor potential calcium channel family

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TRPA1 ion channel
Identifiers
SymbolTRP-CC
PfamPF00520
InterProIPR005821
SMARTSM00248
PROSITEPS50088
TCDB1.A.4
OPM superfamily8
OPM protein3j9p

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:

  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

References

  1. ↑ "TRPs in the Brain". Reviews of Physiology, Biochemistry and Pharmacology 163: 27–64. 2012-01-01. doi:10.1007/112_2012_8. ISBN 978-3-642-33520-4. PMID 23184016. 
  2. ↑ "Structure-functional intimacies of transient receptor potential channels". Quarterly Reviews of Biophysics 42 (3): 201–46. August 2009. doi:10.1017/S0033583509990072. PMID 20025796. 
  3. ↑ 3.0 3.1 "The TRP superfamily of cation channels". Science's STKE 2005 (272): re3. February 2005. doi:10.1126/stke.2722005re3. PMID 15728426. 
  4. ↑ "An introduction to TRP channels". Annual Review of Physiology 68: 619–47. 2006-01-01. doi:10.1146/annurev.physiol.68.040204.100431. PMID 16460286. 
  5. ↑ "SnapShot: mammalian TRP channels". Cell 129 (1): 220.e1–220.e2. April 2007. doi:10.1016/j.cell.2007.03.034. PMID 17418797. 
  6. ↑ "A C. elegans model of nicotine-dependent behavior: regulation by TRP-family channels". Cell 127 (3): 621–33. November 2006. doi:10.1016/j.cell.2006.09.035. PMID 17081982. 
  7. ↑ "TRP-PLIK, a bifunctional protein with kinase and ion channel activities". Science 291 (5506): 1043–7. February 2001. doi:10.1126/science.1058519. PMID 11161216. Bibcode: 2001Sci...291.1043R. 
  8. ↑ "Drosophila hygrosensation requires the TRP channels water witch and nanchung". Nature 450 (7167): 294–8. November 2007. doi:10.1038/nature06223. PMID 17994098. Bibcode: 2007Natur.450..294L. 
  9. ↑ 9.0 9.1 "Inhibition of nociceptors by TRPV1-mediated entry of impermeant sodium channel blockers". Nature 449 (7162): 607–10. October 2007. doi:10.1038/nature06191. PMID 17914397. Bibcode: 2007Natur.449..607B. 
  10. ↑ "Structure of six-transmembrane cation channels revealed by single-particle analysis from electron microscopic images". Journal of Synchrotron Radiation 15 (Pt 3): 211–4. May 2008. doi:10.1107/S0909049508004640. PMID 18421141. Bibcode: 2008JSynR..15..211M. 
  11. ↑ "Outer pore topology of the ECaC-TRPV5 channel by cysteine scan mutagenesis". The Journal of Biological Chemistry 279 (8): 6853–62. February 2004. doi:10.1074/jbc.M310534200. PMID 14630907. 
  12. ↑ "Biogenesis and topology of the transient receptor potential Ca2+ channel TRPC1". The Journal of Biological Chemistry 279 (13): 12242–8. March 2004. doi:10.1074/jbc.M312456200. PMID 14707123. 
  13. ↑ "Novel Ca2+ channels underlying transduction in Drosophila photoreceptors: implications for phosphoinositide-mediated Ca2+ mobilization". Trends in Neurosciences 16 (9): 371–6. September 1993. doi:10.1016/0166-2236(93)90095-4. PMID 7694408. 
  14. ↑ "Structural analyses of the ankyrin repeat domain of TRPV6 and related TRPV ion channels". Biochemistry 47 (8): 2476–84. February 2008. doi:10.1021/bi702109w. PMID 18232717. 
  15. ↑ "Voltage Sensing in Thermo-TRP Channels". Transient Receptor Potential Channels. Advances in Experimental Medicine and Biology. 704. 2011-01-01. pp. 517–30. doi:10.1007/978-94-007-0265-3_28. ISBN 978-94-007-0264-6. 
  16. ↑ 16.0 16.1 Hu, Hongzhen; Bandell, Michael; Grandl, Jorg; Petrus, Matt (2011-01-01). Zhu, Michael X.. ed. High-Throughput Approaches to Studying Mechanisms of TRP Channel Activation. Boca Raton (FL): CRC Press/Taylor & Francis. ISBN 9781439818602. https://www.ncbi.nlm.nih.gov/books/NBK92822/. 

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