| Description: |
Transient receptor potential (TRP) channels can be described as tetramers formed by subunits with six transmembrane domains and containing cation-selective pores, which in several cases show high calcium permeability. The molecular architecture of TRP channels is reminiscent ofvoltage-gated channels and comprises six putative transmembrane segments (S1-S6), intracellular N- and C-termini, and a pore-forming reentrant loop between S5 and S6 [].TRP channels represent a superfamily conserved from worms to humans that comprise seven subfamilies []: TRPC (canonical), TRPV (vanilloid), TRPM (melastatin or long TRPs), TRPA (ankyrin, whose only member is Transient receptor potential cation channel subfamily A member 1, TrpA1), TRPP (polycystin), TRPML (mucolipin) and TRPN (Nomp-C homologues), which has a single member that can be found in worms, flies, and zebrafish. TRPs are classified essentially according to their primary amino acid sequence rather than selectivity or ligand affinity, due to their heterogeneous properties and complex regulation.TRP channels are involved in many physiological functions, ranging from pure sensory functions, such as pheromone signalling, taste transduction, nociception, and temperature sensation, over homeostatic functions, such as Ca2+ and Mg2+ reabsorption and osmoregulation, to many other motile functions, such as muscle contraction and vaso-motor control [].The TRPV (vanilloid) subfamily can be divided into two distinct groups. The first, which comprises TrpV1, TrpV2, TrpV3, and TrpV4, with nonselective cation conducting pores, has members which can be activated by temperature as well as chemical stimuli. They are involved in a range of functions including nociception, thermosensing and osmolarity sensing. The second group, which consists of TrpV5 and TrpV6, (also known as epithelial calcium channels 1 and 2), highly calcium selective, are involved in renal Ca2+ absorption/reabsorption [, ].TRPV1 was the first vanilloid receptor identified. It is a nonselective cation channel with a preference for calcium and is activated by noxious stimuli, heat, protons, pH 5.9, and various, mostly obnoxious, natural products []. TRPV1 is predominantly expressed in sensory neurons []and is believed to play a crucial role in temperature sensing and nociception [], qualifying therefore as a molecular target for pain treatment. |
