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Nonclassical Ion Channels in Depression
Published in Tian-Le Xu, Long-Jun Wu, Nonclassical Ion Channels in the Nervous System, 2021
Transient receptor potential (TRP) channels—the second largest class of ion channels in humans—act as sensors in a variety of physiological processes. The TRP channels are subdivided into seven main subfamilies based on amino acid homology: TRPC (canonical), TRPM (melastatin), TRPA (ankyrin), TRPV (vanilloid), TRPN (nomp), TRPML (mucolipin), and TRPP (polycystin)80. Several TRP channels are regulated by phosphatidylinositol 4,5-bisphosphate, while most TRP channels serve as Ca2+ import pathways. Some of these channels are constitutively open, while some are typically gated by sensing the Ca2+ concentration of intracellular Ca2+ stores81.
Structural Determination of the Polycystin-2 Channel by Electron Cryo-Microscopy
Published in Jinghua Hu, Yong Yu, Polycystic Kidney Disease, 2019
The TRP channels conduct cations and are grouped into seven subfamilies according to the relatedness of their protein sequences: TRPC (canonical), TRPM (melastatin), TRPA (ankyrin), TRPV (vanilloid), TRPN (NOMPC-like), TRPML (mucolipin), and TRPP (polycystin).44,61 All TRP channel subfamilies, except for TRPN, are present in mammals. In humans, 27 TRP proteins have been identified, making the TRP family the second largest ion channel family, only outnumbered by the potassium-channel family. The TRP channels are sensory proteins that detect and integrate numerous environmental and endogenous stimuli to elicit proper cellular responses. Some TRP channels operate downstream of, or retain the ability to be regulated by, phospholipase C (PLC)-coupled receptors, as first discovered in the ancestral fly TRPs.62,63 However, for most mammalian TRP channels, the in vivo activation mechanisms are yet to be determined.64
Photobiomodulation Therapy in Orthopedics
Published in Kohlstadt Ingrid, Cintron Kenneth, Metabolic Therapies in Orthopedics, Second Edition, 2018
It is now known that TRP channel proteins are conserved throughout evolution and are found in most organisms, tissues and cell types. The TRP channel superfamily is now classified into seven related subfamilies: TRPC, TRPM, TRPV, TRPA, TRPP, TRPML and TRPN [28]. Light-sensitive ion channels are based on an opsin chromophore (isomerization of a cis-retinal molecule to the trans configuration) as illustrated in Drusophila photorecelptors [29].
Targeting thermoTRP ion channels: in silico preclinical approaches and opportunities
Published in Expert Opinion on Therapeutic Targets, 2020
Gregorio Fernández-Ballester, Asia Fernández-Carvajal, Antonio Ferrer-Montiel
The TRP channel superfamily consists of 28 ion channels grouped in 8 subfamilies, namely TRPC (canonical TRP), TRPV (vanilloid TRP), TRPM (melastatin-related TRP), TRPA (ankyrin TRP), TRPML (mucolipin TRP), TRPN (nompC TRP) and TRPY (yeast TRP) involved in sensory transduction [11]. Notably, members of the TRPV, TRPM, TRPA, and TRPC are gated by temperature changes, constituting the so-called thermoTRPs [12,13]. The TRPV1 receptor, known as the vanilloid receptor, was the founder of the thermoTRP channel family whose members sense and transduce the full spectrum of environmental temperatures, from noxious cold to harmful heat. The cloning of this first heat-sensitive receptor was the initial step for our current understanding of the molecular mechanisms behind thermal nociception [14]. The second heat-sensitive channel discovered was TRPV2 [15], followed by two cold-sensitive members, TRPM8 [16] and TRPA1 [17]. Other TRPV, TRPM, and TRPC channels were thereafter also recognized as thermoTRP channels [13]. Noteworthy, thermoTRP channels are polymodal ion channels that respond to both physical and chemical stimuli. For instance, TRPV1 can be activated by noxious temperatures (≥43ºC), vanilloids (such as capsaicin), membrane depolarization, and extracellular acidic pH. TRPM8 is activated by menthol and cold temperatures, and TRPA1 is a ligand of environmental irritants, mechanical stimuli, and noxious cold [12]. Furthermore, as integral membrane proteins, thermoTRP channels are also modulated by a variety of lipids acting as direct ligands or through modulation of the membrane physicochemical properties [18].
Mechano-gated channels in C. elegans
Published in Journal of Neurogenetics, 2020
Transient receptor potential (TRP) channels are from a family of cation channels involved in a range of sensory processes counting chemosensation, thermosensation, mechanosensation and pain sensation (Arnadottir & Chalfie, 2010; Christensen & Corey, 2007) (Figure 2). TRP channels are classified into seven subfamilies (TRPA, TRPC, TRPML, TRPM, TRPN, TRPP and TRPV), which are tetrameric cation channels that can link to other molecular complexes required in various functions (Christensen & Corey, 2007; Montell, 2005). The importance of TRP ion channels is highlighted by a plethora of diseases and channelopathies in all major organs subjected to dysfunctions or mutations (Christensen & Corey, 2007; Nilius, Voets, & Peters, 2005). Interestingly, TRP channels are also present in single-celled organisms (protozoa) like yeast but limited to only TRPL, TRPM and TRPP channels (Venkatachalam, Luo, & Montell, 2014).
C. elegans: a sensible model for sensory biology
Published in Journal of Neurogenetics, 2020
Caenorhabditis elegans research has proven indispensable in determining the transduction machinery underlying mechanical sensory modalities, such as touch and proprioception. For instance, the founding members of the mechanosensitive DEG/ENaC ion channel family were identified and characterized using genetic approaches with touch behavioral assays in C. elegans, which facilitated identification of vertebrate homologs (Driscoll & Chalfie, 1991; Goodman, 2006). The mechanosensitive TRPN/NOMPC channel TRP-4 transduces touch in CEP/ADE/PDE neurons and mediates stretch-triggered proprioception in the DVA neuron; this mechanosensitive channel is conserved between worms and other invertebrates and low vertebrates (Kang, Gao, Schafer, Xie, & Xu, 2010; Li, Feng, Sternberg, & Xu, 2006). In addition to DVA, some other neurons, such as ventral cord motor neurons, also mediate proprioception, but the underlying mechanosensitive channels remain to be identified (Wen et al., 2012). As most molecules involved in sensory transduction are evolutionarily conserved (Hobert, 2013), identifying sensory receptors, transduction channels and related molecules involved in a mechanosensory process in C. elegans often enhances our molecular understanding of mechanosensation in more complex animals.