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Wong ACY, Birnbaumer L, Housley GD. Canonical transient receptor potential channel subtype 3-mediated hair cell Ca2+entry regulates sound transduction and auditory neurotransmission. Eur J Neurosci 2013; 37:1478-86. [DOI: 10.1111/ejn.12158] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/09/2013] [Accepted: 01/16/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Ann Chi Yan Wong
- Translational Neuroscience Facility and Department of Physiology; School of Medical Sciences; University of New South Wales; Sydney; 2052; NSW; Australia
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, NIH, Building 101, Room F180, 111 TW Alexander Dr; Research Triangle Park; NC 27709; USA
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology; School of Medical Sciences; University of New South Wales; Sydney; 2052; NSW; Australia
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52
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Inada H, Procko E, Sotomayor M, Gaudet R. Structural and biochemical consequences of disease-causing mutations in the ankyrin repeat domain of the human TRPV4 channel. Biochemistry 2012; 51:6195-206. [PMID: 22702953 PMCID: PMC3413242 DOI: 10.1021/bi300279b] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The TRPV4 calcium-permeable cation channel plays important
physiological
roles in osmosensation, mechanosensation, cell barrier formation,
and bone homeostasis. Recent studies reported that mutations in TRPV4,
including some in its ankyrin repeat domain (ARD), are associated
with human inherited diseases, including neuropathies and skeletal
dysplasias, probably because of the increased constitutive activity
of the channel. TRPV4 activity is regulated by the binding of calmodulin
and small molecules such as ATP to the ARD at its cytoplasmic N-terminus.
We determined structures of ATP-free and -bound forms of human TRPV4-ARD
and compared them with available TRPV-ARD structures. The third inter-repeat
loop region (Finger 3 loop) is flexible and may act as a switch to
regulate channel activity. Comparisons of TRPV-ARD structures also
suggest an evolutionary link between ARD structure and ATP binding
ability. Thermal stability analyses and molecular dynamics simulations
suggest that ATP increases stability in TRPV-ARDs that can bind ATP.
Biochemical analyses of a large panel of TRPV4-ARD mutations associated
with human inherited diseases showed that some impaired thermal stability
while others weakened ATP binding ability, suggesting molecular mechanisms
for the diseases.
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Affiliation(s)
- Hitoshi Inada
- Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
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53
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Ilatovskaya DV, Pavlov TS, Negulyaev YA, Staruschenko A. Regulation of TRPC6 Channels by Non-Steroidal Anti-Inflammatory Drugs. BIOCHEMISTRY MOSCOW SUPPLEMENT SERIES A-MEMBRANE AND CELL BIOLOGY 2012; 6:265-272. [PMID: 25279100 DOI: 10.1134/s1990747812030063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Family focal segmental glomerulosclerosis (FSGS) is characterized by sclerosis and hyalinosis of particular loops of glomeruli and is one of the causes of the nephrotic syndrome. Certain mutations in the structure of TRPC6 channels are the genetic impetus for FSGS development resulting in podocytes functional abnormalities and various nephropathies. We have recently demonstrated that non-steroid anti-inflammatory drugs (NSAID) ibuprofen and diclofenac decrease the activity of endogenous TRPC like cal cium channels in the podocytes of the freshly isolated rat glomeruli. It has also been shown that TRPC6 chan nels are expressed in the podocytes. In the current study we have functionally reconstituted TRPC6 channels in mammalian cells to investigate the effects of diclofenac on the activity of wild type TRPC6 channel and TRPC6P112Q channel containing a mutation in the N-terminus that was described in FSGS patients. Intracellular calcium level measurements in transfected cells revealed a more intensive carbachol induced increase of calcium concentration in HEK 293 cells expressing TRPC6P112Q versus the cells expressing wild-type TRPC6. We also performed patch-clamp experiments to study TRPC6 channels reconstituted in Chinese hamster ovary (CHO) cell line and found that application of diclofenac (500 μM) acutely reduced single channel activity. Preincubation with diclofenac (100 μM) also decreased the whole cell current in CHO cells overexpressing TRPC6P112Q. Therefore, our previously published data on the effects of NSAID on TRPC-like channels in the isolated rat glomeruli, along with this current investigation on the cultured overexpressed mammalian cells, allows hypothesizing that TRPC6 channels may be a target for NSAID that can be impor tant in the treatment of FSGS.
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Affiliation(s)
- D V Ilatovskaya
- Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA.,Institute of Cytology, Russian Academy of Sciences, Tikhoretskii pr. 4, St. Petersburg, 194064 Russia
| | - T S Pavlov
- Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
| | - Y A Negulyaev
- Institute of Cytology, Russian Academy of Sciences, Tikhoretskii pr. 4, St. Petersburg, 194064 Russia
| | - A Staruschenko
- Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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Freichel M, Almering J, Tsvilovskyy V. The Role of TRP Proteins in Mast Cells. Front Immunol 2012; 3:150. [PMID: 22701456 PMCID: PMC3372879 DOI: 10.3389/fimmu.2012.00150] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 05/22/2012] [Indexed: 01/16/2023] Open
Abstract
Transient receptor potential (TRP) proteins form cation channels that are regulated through strikingly diverse mechanisms including multiple cell surface receptors, changes in temperature, in pH and osmolarity, in cytosolic free Ca(2+) concentration ([Ca(2+)](i)), and by phosphoinositides which makes them polymodal sensors for fine tuning of many cellular and systemic processes in the body. The 28 TRP proteins identified in mammals are classified into six subfamilies: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. When activated, they contribute to cell depolarization and Ca(2+) entry. In mast cells, the increase of [Ca(2+)](i) is fundamental for their biological activity, and several entry pathways for Ca(2+) and other cations were described including Ca(2+) release activated Ca(2+) (CRAC) channels. Like in other non-excitable cells, TRP channels could directly contribute to Ca(2+) influx via the plasma membrane as constituents of Ca(2+) conducting channel complexes or indirectly by shifting the membrane potential and regulation of the driving force for Ca(2+) entry through independent Ca(2+) entry channels. Here, we summarize the current knowledge about the expression of individual Trp genes with the majority of the 28 members being yet identified in different mast cell models, and we highlight mechanisms how they can regulate mast cell functions. Since specific agonists or blockers are still lacking for most members of the TRP family, studies to unravel their function and activation mode still rely on experiments using genetic approaches and transgenic animals. RNAi approaches suggest a functional role for TRPC1, TRPC5, and TRPM7 in mast cell derived cell lines or primary mast cells, and studies using Trp gene knock-out mice reveal a critical role for TRPM4 in mast cell activation and for mast cell mediated cutaneous anaphylaxis, whereas a direct role of cold- and menthol-activated TRPM8 channels seems to be unlikely for the development of cold urticaria at least in mice.
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Affiliation(s)
- Marc Freichel
- Pharmakologisches Institut, Universität HeidelbergHeidelberg, Germany
| | - Julia Almering
- Pharmakologisches Institut, Universität HeidelbergHeidelberg, Germany
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Abstract
The central goal of this overview article is to summarize recent findings in renal epithelial transport,focusing chiefly on the connecting tubule (CNT) and the cortical collecting duct (CCD).Mammalian CCD and CNT are involved in fine-tuning of electrolyte and fluid balance through reabsorption and secretion. Specific transporters and channels mediate vectorial movements of water and solutes in these segments. Although only a small percent of the glomerular filtrate reaches the CNT and CCD, these segments are critical for water and electrolyte homeostasis since several hormones, for example, aldosterone and arginine vasopressin, exert their main effects in these nephron sites. Importantly, hormones regulate the function of the entire nephron and kidney by affecting channels and transporters in the CNT and CCD. Knowledge about the physiological and pathophysiological regulation of transport in the CNT and CCD and particular roles of specific channels/transporters has increased tremendously over the last two decades.Recent studies shed new light on several key questions concerning the regulation of renal transport.Precise distribution patterns of transport proteins in the CCD and CNT will be reviewed, and their physiological roles and mechanisms mediating ion transport in these segments will also be covered. Special emphasis will be given to pathophysiological conditions appearing as a result of abnormalities in renal transport in the CNT and CCD.
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Affiliation(s)
- Alexander Staruschenko
- Department of Physiology and Kidney Disease Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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Samapati R, Yang Y, Yin J, Stoerger C, Arenz C, Dietrich A, Gudermann T, Adam D, Wu S, Freichel M, Flockerzi V, Uhlig S, Kuebler WM. Lung endothelial Ca2+ and permeability response to platelet-activating factor is mediated by acid sphingomyelinase and transient receptor potential classical 6. Am J Respir Crit Care Med 2012; 185:160-70. [PMID: 22246702 DOI: 10.1164/rccm.201104-0717oc] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
RATIONALE Platelet-activating factor (PAF) increases lung vascular permeability within minutes by activation of acid sphingomyelinase (ASM) and a subsequent nitric oxide (NO)-inhibitable and Ca(2+)-dependent loss in barrier function. OBJECTIVES To elucidate the molecular mechanisms underlying this response. METHODS In isolated perfused rat and mouse lungs, endothelial Ca(2+) concentration ([Ca(2+)](i)) was quantified by real-time fluorescence imaging, and caveolae of endothelial cells were isolated and probed for Ca(2+) entry channels. Regulation of transient receptor potential classical (TRPC) 6-mediated currents in lung endothelial cells was assessed by patch clamp technique. MEASUREMENTS AND MAIN RESULTS PAF increased lung weight gain and endothelial [Ca(2+)](i). This response was abrogated by inhibitors of ASM or in ASM-deficient mice, and replicated by lung perfusion with exogenous ASM or C2-ceramide. PAF increased the caveolar abundance of TRPC6 channels, which was similarly blocked by ASM inhibition. PAF-induced increases in lung endothelial [Ca(2+)](i), vascular filtration coefficient, and edema formation were attenuated by the TRPC inhibitor SKF96365 and in TRPC6-deficient mice, whereas direct activation of TRPC6 replicated the [Ca(2+)](i) and edema response to PAF. The exogenous NO donor PapaNONOate or the cyclic guanosine 3',5'-monophosphate analog 8Br-cGMP blocked the endothelial [Ca(2+)](i) and permeability response to PAF, in that they directly blocked TRPC6 channels without interfering with their PAF-induced recruitment to caveolae. CONCLUSIONS The present findings outline a new signaling cascade in the induction of PAF-induced lung edema, in that stimulation of ASM causes recruitment of TRPC6 channels to caveolae, thus allowing for Ca(2+) influx and subsequent increases in endothelial permeability that are amplified in the absence of endothelial NO synthesis.
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Affiliation(s)
- Rudi Samapati
- Institute for Physiology, Charité - Universitätsmedizin Berlin, Germany
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Berg KA, Patwardhan AM, Akopian AN. Receptor and channel heteromers as pain targets. Pharmaceuticals (Basel) 2012; 5:249-78. [PMID: 24281378 PMCID: PMC3763638 DOI: 10.3390/ph5030249] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 02/04/2012] [Accepted: 02/15/2012] [Indexed: 12/20/2022] Open
Abstract
Recent discoveries indicate that many G-protein coupled receptors (GPCRs) and channels involved in pain modulation are able to form receptor heteromers. Receptor and channel heteromers often display distinct signaling characteristics, pharmacological properties and physiological function in comparison to monomer/homomer receptor or ion channel counterparts. It may be possible to capitalize on such unique properties to augment therapeutic efficacy while minimizing side effects. For example, drugs specifically targeting heteromers may have greater tissue specificity and analgesic efficacy. This review will focus on current progress in our understanding of roles of heteromeric GPCRs and channels in pain pathways as well as strategies for controlling pain pathways via targeting heteromeric receptors and channels. This approach may be instrumental in the discovery of novel classes of drugs and expand our repertoire of targets for pain pharmacotherapy.
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Affiliation(s)
- Kelly A. Berg
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (K.A.B.)
| | - Amol M. Patwardhan
- Department of Anesthesiology, Arizona Health Sciences Center, Tucson, AZ 85724, USA; (A.M.P.)
| | - Armen N. Akopian
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (K.A.B.)
- Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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58
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59
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Rietdorf K, Funnell TM, Ruas M, Heinemann J, Parrington J, Galione A. Two-pore channels form homo- and heterodimers. J Biol Chem 2011; 286:37058-62. [PMID: 21903581 PMCID: PMC3199452 DOI: 10.1074/jbc.c111.289835] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two-pore channels (TPCs) have been recently identified as NAADP-regulated Ca2+ release channels, which are localized on the endolysosomal system. TPCs have a 12-transmembrane domain (TMD) structure and are evolutionary intermediates between the 24-TMD α-subunits of Na+ or Ca2+ channels and the transient receptor potential channel superfamily, which have six TMDs in a single subunit and form tetramers with 24 TMDs as active channels. Based on this relationship, it is predicted that TPCs dimerize to form functional channels, but the dimerization of human TPCs has so far not been studied. Using co-immunoprecipitation studies and a mass spectroscopic analysis of the immunocomplex, we show the presence of homo- and heteromeric complexes for human TPC1 and TPC2. Despite their largely distinct localization, we identified a discrete number of endosomes that coexpressed TPC1 and TPC2. Homo- and heteromerization were confirmed by a FRET study, showing that both proteins interacted in a rotational (N- to C-terminal/head-to-tail) symmetry. This is the first report describing the presence of homomultimeric TPC1 channels and the first study showing that TPCs are capable of forming heteromers.
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Affiliation(s)
- Katja Rietdorf
- Department of Pharmacology, Oxford University, Oxford OX1 3QT, UK
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60
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Abstract
A rise in cytoplasmic [Ca2+] due to store-operated Ca2+ entry (SOCE) triggers a plethora of responses, both acute and long term. This leads to the important question of how this initial signal is decoded to regulate specific cellular functions. It is now clearly established that local [Ca2+] at the site of SOCE can vary significantly from the global [Ca2+] in the cytosol. Such Ca2+ microdomains are generated by the assembly of key Ca2+ signaling proteins within the domains. For example, GPCR, IP 3 receptors, TRPC3 channels, the plasma membrane Ca2+ pump and the endoplasmic reticulum (ER) Ca2+ pump have all been found to be assembled in a complex and all of them contribute to the Ca2+ signal. Recent studies have revealed that two other critical components of SOCE, STIM1 and Orai1, are also recruited to these regions. Thus, the entire machinery for activation and regulation of SOCE is compartmentalized in specific cellular domains which facilitates the specificity and rate of protein-protein interactions that are required for activation of the channels. In the case of TRPC1-SOC channels, it appears that specific lipid domains, lipid raft domains (LRDs), in the plasma membrane, as well as cholesterol-binding scaffolding proteins such as caveolin-1 (Cav-1), are involved in assembly of the TRPC channel complexes. Thus, plasma membrane proteins and lipid domains as well as ER proteins contribute to the SOCE-Ca2+ signaling microdomain and modulation of the Ca2+ signals per se. Of further interest is that modulation of Ca2+ signals, i.e. amplitude and/or frequency, can result in regulation of specific cellular functions. The emerging data reveal a dynamic Ca2+ signaling complex composed of TRPC1/Orai1/STIM1 that is physiologically consistent with the dynamic nature of the Ca2+ signal that is generated. This review will focus on the recent studies which demonstrate critical aspects of the TRPC1 channelosome that are involved in the regulation of TRPC1 function and TRPC1-SOC-generated Ca2+ signals.
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Affiliation(s)
- Hwei Ling Ong
- Secretory Physiology Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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61
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Hamaguchi Y, Tatematsu Y, Furukawa K, Matsubara T, Nakayama S. Imipramine inhibition of TRPM-like plasmalemmal Mg2+ transport in vascular smooth muscle cells. J Cell Mol Med 2011; 15:593-601. [PMID: 20132412 PMCID: PMC3922381 DOI: 10.1111/j.1582-4934.2010.01024.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Depression is associated with vascular disease, such as myocardial infarction and stroke. Pharmacological treatments may contribute to this association. On the other hand, Mg2+ deficiency is also known to be a risk factor for the same category of diseases. In the present study, we examined the effect of imipramine on Mg2+ homeostasis in vascular smooth muscle, especially via melastatin-type transient receptor potential (TRPM)-like Mg2+-permeable channels. The intracellular free Mg2+ concentration ([Mg2+]i) was measured using 31P-nuclear magnetic resonance (NMR) in porcine carotid arteries that express both TRPM6 and TRPM7, the latter being predominant. pHi and intracellular phosphorus compounds were simultaneously monitored. To rule out Na+-dependent Mg2+ transport, and to facilitate the activity of Mg2+-permeable channels, experiments were carried out in the absence of Na+ and Ca2+. Changing the extracellular Mg2+ concentration to 0 and 6 mM significantly decreased and increased [Mg2+]i, respectively, in a time-dependent manner. Imipramine statistically significantly attenuated both of the bi-directional [Mg2+]i changes under the Na+- and Ca2+-free conditions. This inhibitory effect was comparable in influx, and much more potent in efflux to that of 2-aminoethoxydiphenyl borate, a well-known blocker of TRPM7, a channel that plays a major role in cellular Mg2+ homeostasis. Neither [ATP]i nor pHi correlated with changes in [Mg2+]i. The results indicate that imipramine suppresses Mg2+-permeable channels presumably through a direct effect on the channel domain. This inhibitory effect appears to contribute, at least partially, to the link between antidepressants and the risk of vascular diseases.
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Affiliation(s)
- Yukihisa Hamaguchi
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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62
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El Hindi S, Reiser J. TRPC channel modulation in podocytes-inching toward novel treatments for glomerular disease. Pediatr Nephrol 2011; 26:1057-64. [PMID: 21161284 PMCID: PMC3098353 DOI: 10.1007/s00467-010-1718-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/29/2010] [Accepted: 11/05/2010] [Indexed: 11/08/2022]
Abstract
Glomerular kidney disease is a major healthcare burden and considered to represent a sum of disorders that evade a refined and effective treatment. Excellent biological and genetic studies have defined pathways that go awry in podocytes, which are the regulatory cells of the glomerular filter. The question now is how to define targets for novel improved therapies. In this review, we summarize critical points around targeting the TRPC6 channel in podocytes.
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Affiliation(s)
- Shafic El Hindi
- Department of Medicine, Division of Nephrology and Hypertension, Leonard Miller School of Medicine, University of Miami, Miami, FL USA
| | - Jochen Reiser
- Department of Medicine, Division of Nephrology and Hypertension, Leonard Miller School of Medicine, University of Miami, Miami, FL USA ,Department of Medicine, Miller School of Medicine, University of Miami, 1580 NW 10th Avenue, Batchelor Bldg, 6th Fl (R-762), Miami, FL 33136 USA
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63
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Wenning AS, Neblung K, Strauß B, Wolfs MJ, Sappok A, Hoth M, Schwarz EC. TRP expression pattern and the functional importance of TRPC3 in primary human T-cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:412-23. [DOI: 10.1016/j.bbamcr.2010.12.022] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 12/22/2010] [Accepted: 12/23/2010] [Indexed: 11/16/2022]
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Lambert S, Drews A, Rizun O, Wagner TFJ, Lis A, Mannebach S, Plant S, Portz M, Meissner M, Philipp SE, Oberwinkler J. Transient receptor potential melastatin 1 (TRPM1) is an ion-conducting plasma membrane channel inhibited by zinc ions. J Biol Chem 2011; 286:12221-33. [PMID: 21278253 DOI: 10.1074/jbc.m110.202945] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
TRPM1 is the founding member of the melastatin subgroup of transient receptor potential (TRP) proteins, but it has not yet been firmly established that TRPM1 proteins form ion channels. Consequently, the biophysical and pharmacological properties of these proteins are largely unknown. Here we show that heterologous expression of TRPM1 proteins induces ionic conductances that can be activated by extracellular steroid application. However the current amplitudes observed were too small to enable a reliable biophysical characterization. We overcame this limitation by modifying TRPM1 channels in several independent ways that increased the similarity to the closely related TRPM3 channels. The resulting constructs produced considerably larger currents after overexpression. We also demonstrate that unmodified TRPM1 and TRPM3 proteins form functional heteromultimeric channels. With these approaches, we measured the divalent permeability profile and found that channels containing the pore of TRPM1 are inhibited by extracellular zinc ions at physiological concentrations, in contrast to channels containing only the pore of TRPM3. Applying these findings to pancreatic β cells, we found that TRPM1 proteins do not play a major role in steroid-activated currents of these cells. The inhibition of TRPM1 by zinc ions is primarily due to a short stretch of seven amino acids present only in the pore region of TRPM1 but not of TRPM3. Combined, our data demonstrate that TRPM1 proteins are bona fide ion-conducting plasma membrane channels. Their distinct biophysical properties allow a reliable identification of endogenous TRPM1-mediated currents.
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Affiliation(s)
- Sachar Lambert
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
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TRP channels in the cardiopulmonary vasculature. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:781-810. [PMID: 21290327 DOI: 10.1007/978-94-007-0265-3_41] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Transient receptor potential (TRP) channels are expressed in almost every human tissue, including the heart and the vasculature. They play unique roles not only in physiological functions but, if over-expressed, also in pathophysiological disease states. Cardiovascular diseases are the leading cause of death in the industrialized countries. Therefore, TRP channels are attractive drug targets for more effective pharmacological treatments of these diseases. This review focuses on three major cell types of the cardiovascular system: cardiomyocytes as well as smooth muscle cells and endothelial cells from the systemic and pulmonary circulation. TRP channels initiate multiple signals in all three cell types (e.g. contraction, migration) and are involved in gene transcription leading to cell proliferation or cell death. Identification of their genes has significantly improved our knowledge of multiple signal transduction pathways in these cells. Some TRP channels are important cellular sensors and are mostly permeable to Ca(2+), while most other TRP channels are receptor activated and allow for the entry of Na(+), Ca(2+) and Mg(2+). Physiological functions of TRPA, TRPC, TRPM, TRPP and TRPV channels in the cardiovascular system, dissected by down-regulating channel activity in isolated tissues or by the analysis of gene-deficient mouse models, are reviewed. The involvement of TRPs as homomeric or heteromeric channels in pathophysiological processes in the cardiovascular system like heart failure, cardiac hypertrophy, hypertension as well as edema formation by increased endothelial permeability will be discussed.
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66
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Boesmans W, Owsianik G, Tack J, Voets T, Vanden Berghe P. TRP channels in neurogastroenterology: opportunities for therapeutic intervention. Br J Pharmacol 2011; 162:18-37. [PMID: 20804496 PMCID: PMC3012403 DOI: 10.1111/j.1476-5381.2010.01009.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 07/02/2010] [Accepted: 08/17/2010] [Indexed: 12/14/2022] Open
Abstract
The members of the superfamily of transient receptor potential (TRP) cation channels are involved in a plethora of cellular functions. During the last decade, a vast amount of evidence is accumulating that attributes an important role to these cation channels in different regulatory aspects of the alimentary tract. In this review we discuss the expression patterns and roles of TRP channels in the regulation of gastrointestinal motility, enteric nervous system signalling and visceral sensation, and provide our perspectives on pharmacological targeting of TRPs as a strategy to treat various gastrointestinal disorders. We found that the current knowledge about the role of some members of the TRP superfamily in neurogastroenterology is rather limited, whereas the function of other TRP channels, especially of those implicated in smooth muscle cell contractility (TRPC4, TRPC6), visceral sensitivity and hypersensitivity (TRPV1, TRPV4, TRPA1), tends to be well established. Compared with expression data, mechanistic information about TRP channels in intestinal pacemaking (TRPC4, TRPC6, TRPM7), enteric nervous system signalling (TRPCs) and enteroendocrine cells (TRPM5) is lacking. It is clear that several different TRP channels play important roles in the cellular apparatus that controls gastrointestinal function. They are involved in the regulation of gastrointestinal motility and absorption, visceral sensation and visceral hypersensitivity. TRP channels can be considered as interesting targets to tackle digestive diseases, motility disorders and visceral pain. At present, TRPV1 antagonists are under development for the treatment of heartburn and visceral hypersensitivity, but interference with other TRP channels is also tempting. However, their role in gastrointestinal pathophysiology first needs to be further elucidated.
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Affiliation(s)
- Werend Boesmans
- TARGID – Translational Research Center for Gastrointestinal DisordersKULeuven, Leuven, Belgium
| | | | - Jan Tack
- TARGID – Translational Research Center for Gastrointestinal DisordersKULeuven, Leuven, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel ResearchKULeuven, Leuven, Belgium
| | - Pieter Vanden Berghe
- TARGID – Translational Research Center for Gastrointestinal DisordersKULeuven, Leuven, Belgium
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Heteromerization of TRP channel subunits: extending functional diversity. Protein Cell 2010; 1:802-10. [PMID: 21203922 DOI: 10.1007/s13238-010-0108-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 09/01/2010] [Indexed: 01/03/2023] Open
Abstract
Transient receptor potential (TRP) channels are widely found throughout the animal kingdom. By serving as cellular sensors for a wide spectrum of physical and chemical stimuli, they play crucial physiological roles ranging from sensory transduction to cell cycle modulation. TRP channels are tetrameric protein complexes. While most TRP subunits can form functional homomeric channels, heteromerization of TRP channel subunits of either the same subfamily or different subfamilies has been widely observed. Heteromeric TRP channels exhibit many novel properties compared to their homomeric counterparts, indicating that co-assembly of TRP channel subunits has an important contribution to the diversity of TRP channel functions.
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68
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Bomben VC, Sontheimer H. Disruption of transient receptor potential canonical channel 1 causes incomplete cytokinesis and slows the growth of human malignant gliomas. Glia 2010; 58:1145-56. [PMID: 20544850 DOI: 10.1002/glia.20994] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Despite decades of research, primary brain tumors, gliomas, lack effective treatment options and present a huge clinical challenge. Particularly, the most malignant subtype, Glioblastoma multiforme, proliferates extensively and cells often undergo incomplete cell divisions, resulting in multinucleated cells. We now present evidence that multinucleated glioma cells result from the functional loss of transient receptor potential canonical 1 (TRPC1) channels, plasma membrane proteins involved in agonist-induced calcium entry and reloading of intracellular Ca(2+) stores. Pharmacological inhibition or shRNA mediated suppression of TRPC1 causes loss of functional channels and store-operated calcium entry in D54MG glioma cells. This is associated with reduced cell proliferation and, frequently, with incomplete cell division. The resulting multinucleated cells are reminiscent of those found in patient biopsies. In a flank tumor model, tumor size was significantly decreased when TRPC1 expression was disrupted using a doxycycline inducible shRNA knockdown approach. These results suggest that TRPC1 channels play an important role in glioma cell division most likely by regulating calcium signaling during cytokinesis.
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Affiliation(s)
- Valerie C Bomben
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
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69
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Tai C, Hines DJ, Choi HB, MacVicar BA. Plasma membrane insertion of TRPC5 channels contributes to the cholinergic plateau potential in hippocampal CA1 pyramidal neurons. Hippocampus 2010; 21:958-67. [DOI: 10.1002/hipo.20807] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2010] [Indexed: 01/05/2023]
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70
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Interdomain interactions control Ca2+-dependent potentiation in the cation channel TRPV4. PLoS One 2010; 5:e10580. [PMID: 20485495 PMCID: PMC2867956 DOI: 10.1371/journal.pone.0010580] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 04/20/2010] [Indexed: 11/24/2022] Open
Abstract
Several Ca2+-permeable channels, including the non-selective cation channel TRPV4, are subject to Ca2+-dependent facilitation. Although it has been clearly demonstrated in functional experiments that calmodulin (CaM) binding to intracellular domains of TRP channels is involved in this process, the molecular mechanism remains elusive. In this study, we provide experimental evidence for a comprehensive molecular model that explains Ca2+-dependent facilitation of TRPV4. In the resting state, an intracellular domain from the channel N terminus forms an autoinhibitory complex with a C-terminal domain that includes a high-affinity CaM binding site. CaM binding, secondary to rises in intracellular Ca2+, displaces the N-terminal domain which may then form a homologous interaction with an identical domain from a second subunit. This represents a novel potentiation mechanism that may also be relevant in other Ca2+-permeable channels.
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71
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Staruschenko A, Jeske NA, Akopian AN. Contribution of TRPV1-TRPA1 interaction to the single channel properties of the TRPA1 channel. J Biol Chem 2010; 285:15167-15177. [PMID: 20231274 DOI: 10.1074/jbc.m110.106153] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Several lines of evidence suggest that TRPA1 and TRPV1 mutually control the transduction of inflammation-induced noxious stimuli in sensory neurons. It was recently shown that certain TRPA1 properties are modulated by TRPV1. However, direct interaction between TRPA1 and TRPV1 as well as regulation of TRPA1 intrinsic characteristics by the TRPV1 channel have not been examined. To address these questions, we have studied a complex formation between TRPA1 and TRPV1 and characterized the influence of TRPV1 on single channel TRPA1-mediated currents. Co-immunoprecipitation analysis revealed direct interactions between TRPA1 and TRPV1 in an expression system as well as in sensory neurons. Data generated with total internal reflection fluorescence-based fluorescence resonance energy transfer indicate that a TRPA1-TRPV1 complex can be formed on the plasma membrane. The fluorescence resonance energy transfer interaction between TRPA1 and TRPV1 channels is as effective as for TRPV1 or TRPA1 homomers. Single channel analysis in a heterologous expression system and in sensory neurons of wild type and TRPV1 knock-out mice demonstrated that co-expression of TRPV1 with TRPA1 results in outward rectification of single channel mustard oil (I(MO)) current-voltage relationships (I-V) and substantial modulation of the open probability at negative holding potentials. TRPV1 also does not influence the characteristics of single channel I(MO) in Ca(2+)-free extracellular solution. However, association of TRPA1 with TRPV1 was not affected in Ca(2+)-free media. To assess a role of intracellular Ca(2+) in TRPV1-dependent modulation of TRPA1 modulation, the TRPA1-mediated single channel WIN55,212-2-gated current (I(WIN)) was recorded in inside-out configuration. Our data indicate that single channel properties of TRPA1 are regulated by TRPV1 independently of intracellular Ca(2+). In summary, our results support the hypothesis that TRPV1 and TRPA1 form a complex and that TRPV1 influences intrinsic characteristics of the TRPA1 channel.
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Affiliation(s)
- Alexander Staruschenko
- Department of Physiology and Kidney Disease Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226-0509
| | - Nathaniel A Jeske
- Departments of Oral and Maxillofacial Surgery, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Armen N Akopian
- Departments of Endodontics, University of Texas Health Science Center, San Antonio, Texas 78229.
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Abstract
Although a unifying characteristic common to all transient receptor potential (TRP) channel functions remains elusive, they could be described as tetramers formed by subunits with six transmembrane domains and containing cation-selective pores, which in several cases show high calcium permeability. TRP channels constitute a large superfamily of ion channels, and can be grouped into seven subfamilies based on their amino acid sequence homology: the canonical or classic TRPs, the vanilloid receptor TRPs, the melastatin or long TRPs, ankyrin (whose only member is the transmembrane protein 1 [TRPA1]), TRPN after the nonmechanoreceptor potential C (nonpC), and the more distant cousins, the polycystins and mucolipins. Because of their role as cellular sensors, polymodal activation and gating properties, many TRP channels are activated by a variety of different stimuli and function as signal integrators. Thus, how TRP channels function and how function relates to given structural determinants contained in the channel-forming protein has attracted the attention of biophysicists as well as molecular and cell biologists. The main purpose of this review is to summarize our present knowledge on the structure of channels of the TRP ion channel family. In the absence of crystal structure information for a complete TRP channel, we will describe important protein domains present in TRP channels, structure-function mutagenesis studies, the few crystal structures available for some TRP channel modules, and the recent determination of some TRP channel structures using electron microscopy.
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73
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Lu Y, Ma X, Sabharwal R, Snitsarev V, Morgan D, Rahmouni K, Drummond HA, Whiteis CA, Costa V, Price M, Benson C, Welsh MJ, Chapleau MW, Abboud FM. The ion channel ASIC2 is required for baroreceptor and autonomic control of the circulation. Neuron 2010; 64:885-97. [PMID: 20064394 DOI: 10.1016/j.neuron.2009.11.007] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2009] [Indexed: 12/18/2022]
Abstract
Arterial baroreceptors provide a neural sensory input that reflexly regulates the autonomic drive of circulation. Our goal was to test the hypothesis that a member of the acid-sensing ion channel (ASIC) subfamily of the DEG/ENaC superfamily is an important determinant of the arterial baroreceptor reflex. We found that aortic baroreceptor neurons in the nodose ganglia and their terminals express ASIC2. Conscious ASIC2 null mice developed hypertension, had exaggerated sympathetic and depressed parasympathetic control of the circulation, and a decreased gain of the baroreflex, all indicative of an impaired baroreceptor reflex. Multiple measures of baroreceptor activity each suggest that mechanosensitivity is diminished in ASIC2 null mice. The results define ASIC2 as an important determinant of autonomic circulatory control and of baroreceptor sensitivity. The genetic disruption of ASIC2 recapitulates the pathological dysautonomia seen in heart failure and hypertension and defines a molecular defect that may be relevant to its development.
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Affiliation(s)
- Yongjun Lu
- Department of Internal Medicine and Cardiovascular Research Center, University of Iowa, Iowa City, IA 52242, USA
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Lev S, Zeevi DA, Frumkin A, Offen-Glasner V, Bach G, Minke B. Constitutive activity of the human TRPML2 channel induces cell degeneration. J Biol Chem 2010; 285:2771-82. [PMID: 19940139 PMCID: PMC2807332 DOI: 10.1074/jbc.m109.046508] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 11/19/2009] [Indexed: 01/01/2023] Open
Abstract
The mucolipin (TRPML) ion channel proteins represent a distinct subfamily of channel proteins within the transient receptor potential (TRP) superfamily of cation channels. Mucolipin 1, 2, and 3 (TRPML1, -2, and -3, respectively) are channel proteins that share high sequence homology with each other and homology in the transmembrane domain with other TRPs. Mutations in the TRPML1 protein are implicated in mucolipidosis type IV, whereas mutations in TRPML3 are found in the varitint-waddler mouse. The properties of the wild type TRPML2 channel are not well known. Here we show functional expression of the wild type human TRPML2 channel (h-TRPML2). The channel is functional at the plasma membrane and characterized by a significant inward rectification similar to other constitutively active TRPML mutant isoforms. The h-TRPML2 channel displays nonselective cation permeability, which is Ca(2+)-permeable and inhibited by low extracytosolic pH but not Ca(2+) regulated. In addition, constitutively active h-TRPML2 leads to cell death by causing Ca(2+) overload. Furthermore, we demonstrate by functional mutation analysis that h-TRPML2 shares similar characteristics and structural similarities with other TRPML channels that regulate the channel in a similar manner. Hence, in addition to overall structure, all three TRPML channels also share common modes of regulation.
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Affiliation(s)
- Shaya Lev
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of the Hebrew University, and
| | - David A. Zeevi
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Ayala Frumkin
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Vered Offen-Glasner
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Gideon Bach
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Baruch Minke
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of the Hebrew University, and
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75
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Gaudet R. Divide and conquer: high resolution structural information on TRP channel fragments. ACTA ACUST UNITED AC 2009; 133:231-7. [PMID: 19237587 PMCID: PMC2654082 DOI: 10.1085/jgp.200810137] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 01238, USA.
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76
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Identification of dimer interactions required for the catalytic activity of the TRPM7 alpha-kinase domain. Biochem J 2009; 420:115-22. [PMID: 19228120 DOI: 10.1042/bj20081405] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
TRPM7 (transient receptor potential melastatin) combines an ion channel domain with a C-terminal protein kinase domain that belongs to the atypical alpha-kinase family. The TRPM7 alpha-kinase domain assembles into a dimer through the exchange of an N-terminal segment that extends from residue 1551 to residue 1577 [Yamaguchi, Matsushita, Nairn and Kuriyan (2001) Mol. Cell 7, 1047-1057]. Here, we show, by analysis of truncation mutants, that residues 1553-1562 of the N-terminus are essential for kinase activity but not dimer formation. Within this 'activation sequence', site-directed mutagenesis identified Tyr-1553 and Arg-1558 as residues critical for activity. Examination of the TRPM7 kinase domain structure suggests that the activation sequence interacts with the other subunit to help position a catalytic loop that contains the invariant Asp-1765 residue. Residues 1563-1570 of the N-terminal segment are critical for dimer assembly. Mutation of Leu-1564, Ile-1568 or Phe-1570 to alanine abolished both kinase activity and dimer formation. The activity of a monomeric TRPM7 kinase domain lacking the entire N-terminal segment was rescued by a GST (glutathione transferase) fusion protein containing residues 1548-1576 of TRPM7, showing that all interactions essential for activity are provided by the N-terminal segment. Activity was also restored by GST fused to the N-terminal segment of TRPM6 (residues 1711-1740), demonstrating the feasibility of forming functional TRPM6-TRPM7 alpha-kinase domain heterodimers. It is proposed that covalent modifications or binding interactions that alter the conformation of the N-terminal exchanged segment may provide a means to regulate TRPM7 kinase activity.
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77
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Kauer JA, Gibson HE. Hot flash: TRPV channels in the brain. Trends Neurosci 2009; 32:215-24. [PMID: 19285736 DOI: 10.1016/j.tins.2008.12.006] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2008] [Revised: 12/08/2008] [Accepted: 12/09/2008] [Indexed: 01/27/2023]
Abstract
TRPV1 (transient receptor potential, vanilloid) channels belong to a family of ligand-gated ion channels gated not only by the binding of certain lipophilic molecules but also by extracellular protons and physical stimuli such as heat or osmotic pressure changes. These nonselective cation channels are permeable to Na(+) and K(+) and are also very Ca(2+) permeable; in fact, TRPV1 is as Ca(2+) permeable as the NMDA receptor channel and can, thus, act as a trigger for Ca(2+)-mediated cell signaling. Although these channels are highly expressed in primary sensory afferents, accumulating evidence indicates that TRPV family channels are also present in the brain. Here, we review evidence that TRPV channels in the central nervous system might contribute to many basic neuronal functions including resting membrane potential, neurotransmitter release and synaptic plasticity.
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Affiliation(s)
- Julie A Kauer
- Brown University, Department of Molecular Pharmacology, Physiology and Biotechnology, Providence, RI 02912, USA.
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78
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Lepage PK, Lussier MP, McDuff FO, Lavigne P, Boulay G. The self-association of two N-terminal interaction domains plays an important role in the tetramerization of TRPC4. Cell Calcium 2009; 45:251-9. [DOI: 10.1016/j.ceca.2008.11.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/30/2008] [Accepted: 11/03/2008] [Indexed: 11/28/2022]
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79
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Vassort G, Alvarez J. Transient receptor potential: a large family of new channels of which several are involved in cardiac arrhythmiaThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 1 of a 2-part Special Issue). Can J Physiol Pharmacol 2009; 87:100-7. [DOI: 10.1139/y08-112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The transient receptor potential (TRP) family of ion channels comprises more than 50 cation-permeable channels expressed throughout the animal kingdom. TRPs can be grouped into 7 main subfamilies according to structural homology: the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), TRPA (ankyrin), and TRPN (NO mechanopotential). During the past 20 years, the cloning and characterization after reexpression of most members of these cation channels have led to a plethora of data and more recently to some understanding of their roles in various cells and tissues. Specifically in the heart, TRPs are known to be involved in various diseases, including hypertrophy, heart failure, and arrhythmia. The later part of this review focuses on the potential contribution of TRPs to cardiac rhythm and their potential proarrhythmic effects. Furthermore, several neurotransmitters that activate the formation of diacylglycerol could modulate cardiac rhythm or, like ATP, induce arrhythmia.
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Affiliation(s)
- Guy Vassort
- INSERM U-637 Physiopathologie cardiovasculaire, CHU Arnaud de Villeneuve, Montpellier Cedex 05, 34295 France
- Laboratorio de Electrofisiologia, Instituto de Cardiologia, La Habana 10400, Cuba
| | - Julio Alvarez
- INSERM U-637 Physiopathologie cardiovasculaire, CHU Arnaud de Villeneuve, Montpellier Cedex 05, 34295 France
- Laboratorio de Electrofisiologia, Instituto de Cardiologia, La Habana 10400, Cuba
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80
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Liu D, Zhu Z, Tepel M. The Role of Transient Receptor Potential Channels in Metabolic Syndrome. Hypertens Res 2008; 31:1989-95. [DOI: 10.1291/hypres.31.1989] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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81
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Hamaguchi Y, Matsubara T, Amano T, Uetani T, Asano H, Iwamoto T, Furukawa K, Murohara T, Nakayama S. Na(+)-independent Mg(2+) transport sensitive to 2-aminoethoxydiphenyl borate (2-APB) in vascular smooth muscle cells: involvement of TRPM-like channels. J Cell Mol Med 2008; 12:962-74. [PMID: 18494937 PMCID: PMC4401140 DOI: 10.1111/j.1582-4934.2008.00157.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Magnesium is associated with several important cardiovascular diseases. There is an accumulating body of evidence verifying the important roles of Mg2+-permeable channels. In the present study, we estimated the intracellular free Mg2+ concentration ([Mg2+]i) using 31P-nuclear magnetic resonance (31P-NMR) in porcine carotid arteries. pHi and intracellular phosphorus compounds were simultaneously monitored. Removal of extracellular divalent cations (Ca2+ and Mg2+) in the absence of Na+ caused a gradual decrease in [Mg2+]i to ∼60% of the control value after 125 min. On the other hand, the simultaneous removal of extracellular Ca2+ and Na+ in the presence of Mg2+ gradually increased [Mg2+]i in an extracellular Mg2+-dependent manner. 2-aminoethoxydiphenyl borate (2-APB) attenuated both [Mg2+]i load and depletion caused under Na+- and Ca2+-free conditions. Neither [ATP]i nor pHi correlated with changes in [Mg2+]i. RT-PCR detected transcripts of both TRPM6 and TRPM7, although TRPM7 was predominant. In conclusion, the results suggest the presence of Mg2+-permeable channels of TRPM family that contribute to Mg2+ homeostasis in vascular smooth muscle cells. The low, basal [Mg2+]i level in vascular smooth muscle cells is attributable to the relatively low activity of this Mg2+ entry pathway.
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Affiliation(s)
- Yukihisa Hamaguchi
- Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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82
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Köttgen M, Buchholz B, Garcia-Gonzalez MA, Kotsis F, Fu X, Doerken M, Boehlke C, Steffl D, Tauber R, Wegierski T, Nitschke R, Suzuki M, Kramer-Zucker A, Germino GG, Watnick T, Prenen J, Nilius B, Kuehn EW, Walz G. TRPP2 and TRPV4 form a polymodal sensory channel complex. ACTA ACUST UNITED AC 2008; 182:437-47. [PMID: 18695040 PMCID: PMC2500130 DOI: 10.1083/jcb.200805124] [Citation(s) in RCA: 308] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The primary cilium has evolved as a multifunctional cellular compartment that decorates most vertebrate cells. Cilia sense mechanical stimuli in various organs, but the molecular mechanisms that convert the deflection of cilia into intracellular calcium transients have remained elusive. Polycystin-2 (TRPP2), an ion channel mutated in polycystic kidney disease, is required for cilia-mediated calcium transients but lacks mechanosensitive properties. We find here that TRPP2 utilizes TRPV4 to form a mechano- and thermosensitive molecular sensor in the cilium. Depletion of TRPV4 in renal epithelial cells abolishes flow-induced calcium transients, demonstrating that TRPV4, like TRPP2, is an essential component of the ciliary mechanosensor. Because TRPV4-deficient zebrafish and mice lack renal cysts, our findings challenge the concept that defective ciliary flow sensing constitutes the fundamental mechanism of cystogenesis.
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Affiliation(s)
- Michael Köttgen
- Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany
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83
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Guibert C, Ducret T, Savineau JP. Voltage-independent calcium influx in smooth muscle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:10-23. [DOI: 10.1016/j.pbiomolbio.2008.05.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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84
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Haswell ES, Peyronnet R, Barbier-Brygoo H, Meyerowitz EM, Frachisse JM. Two MscS homologs provide mechanosensitive channel activities in the Arabidopsis root. Curr Biol 2008; 18:730-734. [PMID: 18485707 DOI: 10.1016/j.cub.2008.04.039] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 04/09/2008] [Accepted: 04/11/2008] [Indexed: 10/22/2022]
Abstract
In bacterial and animal systems, mechanosensitive (MS) ion channels are thought to mediate the perception of pressure, touch, and sound [1-3]. Although plants respond to a wide variety of mechanical stimuli, and although many mechanosensitive channel activities have been characterized in plant membranes by the patch-clamp method, the molecular nature of mechanoperception in plant systems has remained elusive [4]. Likely candidates are relatives of MscS (Mechanosensitive channel of small conductance), a well-characterized MS channel that serves to protect E. coli from osmotic shock [5]. Ten MscS-Like (MSL) proteins are found in the genome of the model flowering plant Arabidopsis thaliana[4, 6, 7]. MSL2 and MSL3, along with MSC1, a MscS family member from green algae, are implicated in the control of organelle morphology [8, 9]. Here, we characterize MSL9 and MSL10, two MSL proteins found in the plasma membrane of root cells. We use a combined genetic and electrophysiological approach to show that MSL9 and MSL10, along with three other members of the MSL family, are required for MS channel activities detected in protoplasts derived from root cells. This is the first molecular identification and characterization of MS channels in plant membranes.
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Affiliation(s)
- Elizabeth S Haswell
- Division of Biology 156-29, California Institute of Technology, Pasadena, California 91125.
| | - Rémi Peyronnet
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Hélène Barbier-Brygoo
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Elliot M Meyerowitz
- Division of Biology 156-29, California Institute of Technology, Pasadena, California 91125
| | - Jean-Marie Frachisse
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
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85
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TRPC channels and diacylglycerol dependent calcium signaling in rat sensory neurons. Histochem Cell Biol 2008; 130:655-67. [DOI: 10.1007/s00418-008-0477-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/03/2008] [Indexed: 10/21/2022]
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86
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87
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Wang Y, Fu X, Gaiser S, Köttgen M, Kramer-Zucker A, Walz G, Wegierski T. OS-9 Regulates the Transit and Polyubiquitination of TRPV4 in the Endoplasmic Reticulum. J Biol Chem 2007; 282:36561-70. [DOI: 10.1074/jbc.m703903200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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88
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A role of the transient receptor potential domain of vanilloid receptor I in channel gating. J Neurosci 2007; 27:11641-50. [PMID: 17959807 DOI: 10.1523/jneurosci.2457-07.2007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transient receptor potential vanilloid receptor subtype 1 (TRPV1) is an ionotropic receptor activated by temperature and chemical stimuli. The C-terminal region that is adjacent to the channel gate, recognized as the TRP domain, is a molecular determinant of receptor assembly. However, the role of this intracellular domain in channel function remains elusive. Here, we show that replacement of the TRP domain of TRPV1 with the cognate region of TRPV channels (TRPV2-TRPV6) did not affect receptor assembly and trafficking to the cell surface, although those receptors containing the TRP domain of the distantly related TRPV5 and TRPV6 did not display ion channel activity. Notably, functional chimeras exhibited an impaired sensitivity to the activating stimuli, consistent with a significant contribution of this protein domain to channel function. At variance with TRPV1, voltage-dependent gating of chimeric channels could not be detected in the absence of capsaicin and/or heat. Biophysical analysis of functional chimeras revealed that the TRP domain appears to act as a molecular determinant of the activation energy of channel gating. Together, these findings uncover a role of the TRP domain in intersubunit interactions near the channel gate that contribute to the coupling of stimulus sensing to channel opening.
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89
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Levine JD, Alessandri-Haber N. TRP channels: Targets for the relief of pain. Biochim Biophys Acta Mol Basis Dis 2007; 1772:989-1003. [PMID: 17321113 DOI: 10.1016/j.bbadis.2007.01.008] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 01/12/2007] [Accepted: 01/16/2007] [Indexed: 02/01/2023]
Abstract
Patients with inflammatory or neuropathic pain experience hypersensitivity to mechanical, thermal and/or chemical stimuli. Given the diverse etiologies and molecular mechanisms of these pain syndromes, an approach to developing successful therapies may be to target ion channels that contribute to the detection of thermal, mechanical and chemical stimuli and promote the sensitization and activation of nociceptors. Transient Receptor Potential (TRP) channels have emerged as a family of evolutionarily conserved ligand-gated ion channels that contribute to the detection of physical stimuli. Six TRPs (TRPV1, TRPV2, TRPV3, TRPV4, TRPM8 and TRPA1) have been shown to be expressed in primary afferent nociceptors, pain sensing neurons, where they act as transducers for thermal, chemical and mechanical stimuli. This short review focuses on their contribution to pain hypersensitivity associated with peripheral inflammatory and neuropathic pain states.
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Affiliation(s)
- Jon D Levine
- Department of Oral and Maxillofacial Surgery, Box 0440, University of California, San Francisco, 521 Parnassus Avenue, San Francisco, CA 94143-0440, USA
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90
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Sinani D, Adle DJ, Kim H, Lee J. Distinct mechanisms for Ctr1-mediated copper and cisplatin transport. J Biol Chem 2007; 282:26775-26785. [PMID: 17627943 DOI: 10.1074/jbc.m703973200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Ctr1 family of integral membrane proteins is necessary for high affinity copper uptake in eukaryotes. Ctr1 is also involved in cellular accumulation of cisplatin, a platinum-based anticancer drug. Although the physiological role of Ctr1 has been revealed, the mechanism of action of Ctr1 remains to be elucidated. To gain a better understanding of Ctr1-mediated copper and cisplatin transport, we have monitored molecular dynamics and transport activities of yeast Saccharomyces cerevisiae Ctr1 and its mutant alleles. Co-expression of functional Ctr1 monomers fused with either cyan or yellow fluorescent protein resulted in fluorescence resonance energy transfer (FRET), which is consistent with multimer assembly of Ctr1. Copper near the K(m) value of Ctr1 enhanced FRET in a manner that correlated with cellular copper transport. In vitro cross-linking of Ctr1 confirmed that copper-induced FRET reflects conformational changes within pre-existing Ctr1 complexes. FRET assays in membrane-disrupted cells and protein extracts showed that intact cell structure is necessary for Ctr1 activity. Despite Ctr1-dependent cellular accumulation, cisplatin did not change Ctr1 FRET nor did it attenuate copper-induced FRET. A Ctr1 allele defective in copper transport enhanced cellular cisplatin accumulation. N-terminal methionine-rich motifs that are dispensable for copper transport play a critical role for cisplatin uptake. Taken together, our data reveal functional roles for structural remodeling of the Ctr1 multimeric complex in copper transport and suggest distinct mechanisms employed by Ctr1 for copper and cisplatin transport.
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Affiliation(s)
- Devis Sinani
- Redox Biology Center, Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664
| | - David J Adle
- Redox Biology Center, Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664
| | - Heejeong Kim
- Redox Biology Center, Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664
| | - Jaekwon Lee
- Redox Biology Center, Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664.
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91
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Christensen AP, Corey DP. TRP channels in mechanosensation: direct or indirect activation? Nat Rev Neurosci 2007; 8:510-21. [PMID: 17585304 DOI: 10.1038/nrn2149] [Citation(s) in RCA: 329] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ion channels of the transient receptor potential (TRP) superfamily are involved in a wide variety of neural signalling processes, most prominently in sensory receptor cells. They are essential for mechanosensation in systems ranging from fruitfly hearing, to nematode touch, to mouse mechanical pain. However, it is unclear in many instances whether a TRP channel directly transduces the mechanical stimulus or is part of a downstream signalling pathway. Here, we propose criteria for establishing direct mechanical activation of ion channels and review these criteria in a number of mechanosensory systems in which TRP channels are involved.
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Affiliation(s)
- Adam P Christensen
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, Massachusetts 02115, USA.
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92
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Cheng W, Yang F, Takanishi CL, Zheng J. Thermosensitive TRPV channel subunits coassemble into heteromeric channels with intermediate conductance and gating properties. ACTA ACUST UNITED AC 2007; 129:191-207. [PMID: 17325193 PMCID: PMC2151614 DOI: 10.1085/jgp.200709731] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Heat-sensitive transient receptor potential (TRP) channels (TRPV1–4) form the major cellular sensors for detecting temperature increases. Homomeric channels formed by thermosensitive TRPV subunits exhibit distinct temperature thresholds. While these subunits do share significant sequence similarity, whether they can coassemble into heteromeric channels has been controversial. In the present study we investigated the coassembly of TRPV subunits using both spectroscopy-based fluorescence resonance energy transfer (FRET) and single-channel recordings. Fluorescent protein–tagged TRPV subunits were coexpressed in HEK 293 cells; FRET between different subunits was measured as an indication of the formation of heteromeric channels. We observed strong FRET when fluorescence signals were collected selectively from the plasma membrane using a “spectra FRET” approach but much weaker or no FRET from intracellular fluorescence. In addition, no FRET was detected when TRPV subunits were coexpressed with members of the TRPM subfamily or CLC-0 chloride channel subunits. These results indicate that a substantial fraction of TRP channels in the plasma membrane of cotransfected cells were heteromeric. Single-channel recordings confirmed the existence of multiple heteromeric channel forms. Interestingly, heteromeric TRPV channels exhibit intermediate conductance levels and gating kinetic properties. As these subunits coexpress both in sensory neurons and in other tissues, including heart and brain, coassembly between TRPV subunits may contribute to greater functional diversity.
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Affiliation(s)
- Wei Cheng
- Department of Physiology and Membrane Biology, University of California, School of Medcine, Davis, CA 95616
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93
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Ambudkar IS, Ong HL. Organization and function of TRPC channelosomes. Pflugers Arch 2007; 455:187-200. [PMID: 17486362 DOI: 10.1007/s00424-007-0252-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Accepted: 03/10/2007] [Indexed: 12/20/2022]
Abstract
TRPC proteins constitute a family of conserved Ca2+-permeable cation channels which are activated in response to agonist-stimulated PIP2 hydrolysis. These channels were initially proposed to be components of the store-operated calcium entry channel (SOC). Subsequent studies have provided substantial evidence that some TRPCs contribute to SOC activity. TRPC proteins have also been shown to form agonist-stimulated calcium entry channels that are not store-operated but are likely regulated by PIP2 or diacylglycerol. Further, and consistent with the presently available data, selective homomeric or heteromeric interactions between TRPC monomers generate distinct agonist-stimulated cation permeable channels. We suggest that interaction between TRPC monomers, as well as the association of these channels with accessory proteins, determines their mode of regulation as well as their cellular localization and function. Currently identified accessory proteins include key Ca2+ signaling proteins as well as proteins involved in vesicle trafficking, cytoskeletal interactions, and scaffolding. Studies reported until now demonstrate that TRPC proteins are segregated into specific Ca2+ signaling complexes which can generate spatially and temporally controlled [Ca2+]i signals. Thus, the functional organization of TRPC channelosomes dictates not only their regulation by extracellular stimuli but also serves as a platform to coordinate specific downstream cellular functions that are regulated as a consequence of Ca2+ entry. This review will focus on the accessory proteins of TRPC channels and discuss the functional implications of TRPC channelosomes and their assembly in microdomains.
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Affiliation(s)
- Indu S Ambudkar
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
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94
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Chapleau MW, Lu Y, Abboud FM. Mechanosensitive Ion Channels in Blood Pressure‐Sensing Baroreceptor Neurons. CURRENT TOPICS IN MEMBRANES 2007; 59:541-67. [DOI: 10.1016/s1063-5823(06)59021-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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95
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Abstract
Transient receptor potential (TRP) channels are members of a relatively newly described family of cation channels that display a wide range of properties and mechanisms of activation. The exact physiological function and regulation of most of these channels have not yet been conclusively determined. Studies over the past decade have revealed important features of the channels that contribute to their function. These include homomeric interactions between TRP monomers, selective heteromeric interactions within members of the same subfamily, interactions of TRPs with accessory proteins and assembly into macromolecular signaling complexes, and regulation within functionally distinct cellular microdomains. Further, distinct constitutive and regulated vesicular trafficking mechanisms have a critical role not only in controlling the surface expression of TRP channels but also their activation in response to stimuli. A number of cellular components such as cytoskeletal and scaffolding proteins also contribute to TRP channel trafficking. Thus, mechanisms involved in the assembly and trafficking of TRP channels control their plasma membrane expression and critically impact their function and regulation.
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Affiliation(s)
- I S Ambudkar
- Secretory Physiology Section, NIH, Building 10, Room 1N-113, Bethesda, MD 20892, USA.
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96
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Ambudkar IS, Bandyopadhyay BC, Liu X, Lockwich TP, Paria B, Ong HL. Functional organization of TRPC-Ca2+ channels and regulation of calcium microdomains. Cell Calcium 2006; 40:495-504. [PMID: 17030060 DOI: 10.1016/j.ceca.2006.08.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 08/23/2006] [Indexed: 10/24/2022]
Abstract
TRP family of proteins are components of unique cation channels that are activated in response to diverse stimuli ranging from growth factor and neurotransmitter stimulation of plasma membrane receptors to a variety of chemical and sensory signals. This review will focus on members of the TRPC sub-family (TRPC1-TRPC7) which currently appear to be the strongest candidates for the enigmatic Ca(2+) influx channels that are activated in response to stimulation of plasma membrane receptors which result in phosphatidyl inositol-(4,5)-bisphosphate (PIP(2)) hydrolysis, generation of IP(3) and DAG, and IP(3)-induced Ca(2+) release from the intracellular Ca(2+) store via inositol trisphosphate receptor (IP(3)R). Homomeric or selective heteromeric interactions between TRPC monomers generate distinct channels that contribute to store-operated as well as store-independent Ca(2+) entry mechanisms. The former is regulated by the emptying/refilling of internal Ca(2+) store(s) while the latter depends on PIP(2) hydrolysis (due to changes in PIP(2) per se or an increase in diacylglycerol, DAG). Although the exact physiological function of TRPC channels and how they are regulated has not yet been conclusively established, it is clear that a variety of cellular functions are controlled by Ca(2+) entry via these channels. Thus, it is critical to understand how cells coordinate the regulation of diverse TRPC channels to elicit specific physiological functions. It is now well established that segregation of TRPC channels mediated by interactions with signaling and scaffolding proteins, determines their localization and regulation in functionally distinct cellular domains. Furthermore, both protein and lipid components of intracellular and plasma membranes contribute to the organization of these microdomains. Such organization serves as a platform for the generation of spatially and temporally dictated [Ca(2+)](i) signals which are critical for precise control of downstream cellular functions.
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Affiliation(s)
- Indu S Ambudkar
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
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97
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Tsuruda PR, Julius D, Minor DL. Coiled coils direct assembly of a cold-activated TRP channel. Neuron 2006; 51:201-12. [PMID: 16846855 PMCID: PMC3014052 DOI: 10.1016/j.neuron.2006.06.023] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 04/11/2006] [Accepted: 06/09/2006] [Indexed: 11/20/2022]
Abstract
Transient receptor potential (TRP) channels mediate numerous sensory transduction processes and are thought to function as tetramers. TRP channel physiology is well studied; however, comparatively little is understood regarding TRP channel assembly. Here, we identify an autonomously folded assembly domain from the cold- and menthol-gated channel TRPM8. We show that the TRPM8 cytoplasmic C-terminal domain contains a coiled coil that is necessary for channel assembly and sufficient for tetramer formation. Cell biological experiments indicate that coiled-coil formation is required for proper channel maturation and trafficking and that the coiled-coil domain alone can act as a dominant-negative inhibitor of functional channel expression. Our data define an authentic TRP modular assembly domain, establish a clear role for coiled coils in ion channel assembly, demonstrate that coiled-coil assembly domains are a general feature of TRPM channels, and delineate a new tool that should be of general use in dissecting TRPM channel function.
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Affiliation(s)
- Pamela R. Tsuruda
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California 94158
| | - David Julius
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California 94158
| | - Daniel L. Minor
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California 94158
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94158
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California 94158
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California 94158
- Correspondence:
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98
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Lepage PK, Lussier MP, Barajas-Martinez H, Bousquet SM, Blanchard AP, Francoeur N, Dumaine R, Boulay G. Identification of two domains involved in the assembly of transient receptor potential canonical channels. J Biol Chem 2006; 281:30356-64. [PMID: 16916799 DOI: 10.1074/jbc.m603930200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transient receptor potential canonical (TRPC) channels are associated with calcium entry activity in nonexcitable cells. TRPCs can form homo- or heterotetrameric channels, in which case they can assemble together within a subfamily groups. TRPC1, 4, and 5 represent one group, and TRPC3, 6, and 7 represent the other. The molecular determinants involved in promoting subunit tetramerization are not known. To identify them, we generated chimeras by swapping the different domains of TRPC4 with the same regions in TRPC6. We showed that TRPC4 coimmunoprecipitated with the chimeras containing the ankyrin repeats and coiled-coil domains of TRPC4 into TRPC6. However, chimeras containing only the ankyrin repeats or only the coiled-coil domain of TRPC4 did not coimmunoprecipitate with TRPC4. We also showed that a second domain of interaction composed of the pore region and the C-terminal tail is involved in the oligomerization of TRPC4. However, chimeras containing only the pore region or only the C-terminal tail of TRPC4 did not coimmunoprecipitate with TRPC4. Furthermore, we showed that the N terminus of TRPC6 coimmunoprecipitated with the C terminus of TRPC6. Overexpression in HEK293T cells of chimeras that contained an N terminus and a C terminus from different subfamily groups increased intracellular calcium entry subsequent to stimulation of G(q) protein-coupled receptors. These results suggest that two types of interactions are involved in the assembly of the four subunits of the TRPC channel. The first interaction occurs between the N termini and involves two regions. The second interaction occurs between the N terminus and the C terminus and does not appear to be necessary for the activity of TRPCs.
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Affiliation(s)
- Pascale K Lepage
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
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99
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Dietrich A, Chubanov V, Kalwa H, Rost BR, Gudermann T. Cation channels of the transient receptor potential superfamily: their role in physiological and pathophysiological processes of smooth muscle cells. Pharmacol Ther 2006; 112:744-60. [PMID: 16842858 DOI: 10.1016/j.pharmthera.2006.05.013] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Accepted: 05/30/2006] [Indexed: 10/24/2022]
Abstract
Smooth muscle cells (SMC) are essential components of many tissues of the body. Ion channels regulate their membrane potential, the intracellular Ca(2+) concentration ([Ca(2+)](i)) and their contractility. Among the ion channels expressed in SMC cation channels of the transient receptor potential (TRP) superfamily allow the entry of Na(+), Ca(2+) and Mg(2+). Members of the TRP superfamily are essential constituents of tonically active channels (TAC), receptor-operated channels (ROC), store-operated channels (SOC) and stretch-activated channels (SAC). This review focusses on TRP channels (TRPC1, TRPC3, TRPC4, TRPC5, TRPC6, TRPC7, TRPV2, TRPV4, TRPM4, TRPM7, TRPP2) whose physiological functions in SMC were dissected by downregulating channel activity in isolated tissues or by the analysis of gene-deficient mouse models. Their possible functional role and physiological regulation as homomeric or heteromeric channels in SMC are discussed. Moreover, TRP channels may also be responsible for pathophysiological processes involving SMC-like airway hyperresponsiveness and pulmonary hypertension. Therefore, they present important drug targets for future pharmacological interventions.
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Affiliation(s)
- Alexander Dietrich
- Institut für Pharmakologie und Toxikologie, Philipps-Universität Marburg, Karl-von-Frisch Str. 1, 35043 Marburg, Germany.
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100
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Abstract
Cochlear hair cells respond with phenomenal speed and sensitivity to sound vibrations that cause submicron deflections of their hair bundle. Outer hair cells are not only detectors, but also generate force to augment auditory sensitivity and frequency selectivity. Two mechanisms of force production have been proposed: contractions of the cell body or active motion of the hair bundle. Here, we describe recently identified proteins involved in the sensory and motor functions of auditory hair cells and present evidence for each force generator. Both motor mechanisms are probably needed to provide the high sensitivity and frequency discrimination of the mammalian cochlea.
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Affiliation(s)
- Robert Fettiplace
- Department of Physiology, University of Wisconsin Medical School, 185 Medical Sciences Building, 1300 University Avenue, Madison, Wisconsin 53706, USA.
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