101
|
Stock C, Ludwig FT, Hanley PJ, Schwab A. Roles of ion transport in control of cell motility. Compr Physiol 2013; 3:59-119. [PMID: 23720281 DOI: 10.1002/cphy.c110056] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell motility is an essential feature of life. It is essential for reproduction, propagation, embryonic development, and healing processes such as wound closure and a successful immune defense. If out of control, cell motility can become life-threatening as, for example, in metastasis or autoimmune diseases. Regardless of whether ciliary/flagellar or amoeboid movement, controlled motility always requires a concerted action of ion channels and transporters, cytoskeletal elements, and signaling cascades. Ion transport across the plasma membrane contributes to cell motility by affecting the membrane potential and voltage-sensitive ion channels, by inducing local volume changes with the help of aquaporins and by modulating cytosolic Ca(2+) and H(+) concentrations. Voltage-sensitive ion channels serve as voltage detectors in electric fields thus enabling galvanotaxis; local swelling facilitates the outgrowth of protrusions at the leading edge while local shrinkage accompanies the retraction of the cell rear; the cytosolic Ca(2+) concentration exerts its main effect on cytoskeletal dynamics via motor proteins such as myosin or dynein; and both, the intracellular and the extracellular H(+) concentration modulate cell migration and adhesion by tuning the activity of enzymes and signaling molecules in the cytosol as well as the activation state of adhesion molecules at the cell surface. In addition to the actual process of ion transport, both, channels and transporters contribute to cell migration by being part of focal adhesion complexes and/or physically interacting with components of the cytoskeleton. The present article provides an overview of how the numerous ion-transport mechanisms contribute to the various modes of cell motility.
Collapse
Affiliation(s)
- Christian Stock
- Institute of Physiology II, University of Münster, Münster, Germany.
| | | | | | | |
Collapse
|
102
|
Križaj D, Ryskamp DA, Tian N, Tezel G, Mitchell CH, Slepak VZ, Shestopalov VI. From mechanosensitivity to inflammatory responses: new players in the pathology of glaucoma. Curr Eye Res 2013; 39:105-19. [PMID: 24144321 DOI: 10.3109/02713683.2013.836541] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
PURPOSE OF THE STUDY Many blinding diseases of the inner retina are associated with degeneration and loss of retinal ganglion cells (RGCs). Recent evidence implicates several new signaling mechanisms as causal agents associated with RGC injury and remodeling of the optic nerve head. Ion channels such as Transient receptor potential vanilloid isoform 4 (TRPV4), pannexin-1 (Panx1) and P2X7 receptor are localized to RGCs and act as potential sensors and effectors of mechanical strain, ischemia and inflammatory responses. Under normal conditions, TRPV4 may function as an osmosensor and a polymodal molecular integrator of diverse mechanical and chemical stimuli, whereas P2X7R and Panx1 respond to stretch- and/or swelling-induced adenosine triphosphate release from neurons and glia. Ca(2+) influx, induced by stimulation of mechanosensitive ion channels in glaucoma, is proposed to influence dendritic and axonal remodeling that may lead to RGC death while (at least initially) sparing other classes of retinal neuron. The secondary phase of the retinal glaucoma response is associated with microglial activation and an inflammatory response involving Toll-like receptors (TLRs), cluster of differentiation 3 (CD3) immune recognition molecules associated with the T-cell antigen receptor, complement molecules and cell type-specific release of neuroactive cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The retinal response to mechanical stress thus involves a diversity of signaling pathways that sense and transduce mechanical strain and orchestrate both protective and destructive secondary responses. CONCLUSIONS Mechanistic understanding of the interaction between pressure-dependent and independent pathways is only beginning to emerge. This review focuses on the molecular basis of mechanical strain transduction as a primary mechanism that can damage RGCs. The damage occurs through Ca(2+)-dependent cellular remodeling and is associated with parallel activation of secondary ischemic and inflammatory signaling pathways. Molecules that mediate these mechanosensory and immune responses represent plausible targets for protecting ganglion cells in glaucoma, optic neuritis and retinal ischemia.
Collapse
|
103
|
Alexander R, Kerby A, Aubdool AA, Power AR, Grover S, Gentry C, Grant AD. 4α-phorbol 12,13-didecanoate activates cultured mouse dorsal root ganglia neurons independently of TRPV4. Br J Pharmacol 2013; 168:761-72. [PMID: 22928864 DOI: 10.1111/j.1476-5381.2012.02186.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 07/22/2012] [Accepted: 08/15/2012] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The Ca(2+) -permeable cation channel TRPV4 is activated by mechanical disturbance of the cell membrane and is implicated in mechanical hyperalgesia. Nerve growth factor (NGF) is increased during inflammation and causes mechanical hyperalgesia. 4α-phorbol 12,13-didecanoate (4αPDD) has been described as a selective TRPV4 agonist. We investigated NGF-induced hyperalgesia in TRPV4 wild-type (+/+) and knockout (-/-) mice, and the increases in [Ca(2+) ](i) produced by 4αPDD in cultured mouse dorsal root ganglia neurons following exposure to NGF. EXPERIMENTAL APPROACH Withdrawal thresholds to heat, von Frey hairs and pressure were measured in mice before and after systemic administration of NGF. Changes in intracellular Ca(2+) concentration were measured by ratiometric imaging with Fura-2 in cultured DRG and trigeminal ganglia (TG) neurons during perfusion of TRPV4 agonists. KEY RESULTS Administration of NGF caused a significant sensitization to heat and von Frey stimuli in TRPV4 +/+ and -/- mice, but only TRPV4 +/+ mice showed sensitization to noxious pressure. 4αPDD stimulated a dose-dependent increase in [Ca(2+) ](i) in neurons from +/+ and -/- mice, with the proportion of responding neurons and magnitude of increase unaffected by the genotype. In contrast, the selective TRPV4 agonist GSK1016790A failed to stimulate an increase in intracellular Ca(2+) in cultured neurons. Responses to 4αPDD were unaffected by pretreatment with NGF. CONCLUSIONS AND IMPLICATIONS TRPV4 contributes to mechanosensation in vivo, but there is little evidence for functional TRPV4 in cultured DRG and TG neurons. We conclude that 4αPDD activates these neurons independently of TRPV4, so it is not appropriate to refer to 4αPDD as a selective TRPV4 agonist.
Collapse
Affiliation(s)
- R Alexander
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | | | | | | | | | | | | |
Collapse
|
104
|
Phosphatidylinositol-4,5-biphosphate-dependent rearrangement of TRPV4 cytosolic tails enables channel activation by physiological stimuli. Proc Natl Acad Sci U S A 2013; 110:9553-8. [PMID: 23690576 DOI: 10.1073/pnas.1220231110] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Most transient receptor potential (TRP) channels are regulated by phosphatidylinositol-4,5-biphosphate (PIP2), although the structural rearrangements occurring on PIP2 binding are currently far from clear. Here we report that activation of the TRP vanilloid 4 (TRPV4) channel by hypotonic and heat stimuli requires PIP2 binding to and rearrangement of the cytosolic tails. Neutralization of the positive charges within the sequence (121)KRWRK(125), which resembles a phosphoinositide-binding site, rendered the channel unresponsive to hypotonicity and heat but responsive to 4α-phorbol 12,13-didecanoate, an agonist that binds directly to transmembrane domains. Similar channel response was obtained by depletion of PIP2 from the plasma membrane with translocatable phosphatases in heterologous expression systems or by activation of phospholipase C in native ciliated epithelial cells. PIP2 facilitated TRPV4 activation by the osmotransducing cytosolic messenger 5'-6'-epoxyeicosatrienoic acid and allowed channel activation by heat in inside-out patches. Protease protection assays demonstrated a PIP2-binding site within the N-tail. The proximity of TRPV4 tails, analyzed by fluorescence resonance energy transfer, increased by depleting PIP2 mutations in the phosphoinositide site or by coexpression with protein kinase C and casein kinase substrate in neurons 3 (PACSIN3), a regulatory molecule that binds TRPV4 N-tails and abrogates activation by cell swelling and heat. PACSIN3 lacking the Bin-Amphiphysin-Rvs (F-BAR) domain interacted with TRPV4 without affecting channel activation or tail rearrangement. Thus, mutations weakening the TRPV4-PIP2 interacting site and conditions that deplete PIP2 or restrict access of TRPV4 to PIP2--in the case of PACSIN3--change tail conformation and negatively affect channel activation by hypotonicity and heat.
Collapse
|
105
|
Mechanosensitive TRPC1 channels promote calpain proteolysis of talin to regulate spinal axon outgrowth. J Neurosci 2013; 33:273-85. [PMID: 23283340 DOI: 10.1523/jneurosci.2142-12.2013] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Intracellular Ca(2+) signals control the development and regeneration of spinal axons downstream of chemical guidance cues, but little is known about the roles of mechanical cues in axon guidance. Here we show that transient receptor potential canonical 1 (TRPC1) subunits assemble mechanosensitive (MS) channels on Xenopus neuronal growth cones that regulate the extension and direction of axon outgrowth on rigid, but not compliant, substrata. Reducing expression of TRPC1 by antisense morpholinos inhibits the effects of MS channel blockers on axon outgrowth and local Ca(2+) transients. Ca(2+) influx through MS TRPC1 activates the protease calpain, which cleaves the integrin adaptor protein talin to reduce Src-dependent axon outgrowth, likely through altered adhesion turnover. We found that talin accumulates at the tips of dynamic filopodia, which is lost upon cleavage of talin by active calpain. This pathway may also be important in axon guidance decisions since asymmetric inhibition of MS TRPC1 is sufficient to induce growth cone turning. Together our results suggest that Ca(2+) influx through MS TRPC1 on filopodia activates calpain to control growth cone turning during development.
Collapse
|
106
|
Nilius B, Voets T. The puzzle of TRPV4 channelopathies. EMBO Rep 2013; 14:152-63. [PMID: 23306656 DOI: 10.1038/embor.2012.219] [Citation(s) in RCA: 234] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 12/10/2012] [Indexed: 11/09/2022] Open
Abstract
Hereditary channelopathies, that is, mutations in channel genes that alter channel function and are causal for the pathogenesis of the disease, have been described for several members of the transient receptor potential channel family. Mutations in the TRPV4 gene, encoding a polymodal Ca(2+) permeable channel, are causative for several human diseases, which affect the skeletal system and the peripheral nervous system, with highly variable phenotypes. In this review, we describe the phenotypes of TRPV4 channelopathies and overlapping symptoms. Putative mechanisms to explain the puzzle, and how mutations in the same region of the channel cause different diseases, are discussed and experimental approaches to tackle this surprising problem are suggested.
Collapse
Affiliation(s)
- Bernd Nilius
- KU Leuven, Department of Cellular & Molecular Medicine, Laboratory of Ion Channel Research, Campus Gasthuisberg, Leuven, Belgium.
| | | |
Collapse
|
107
|
Kang SS, Shin SH, Auh CK, Chun J. Human skeletal dysplasia caused by a constitutive activated transient receptor potential vanilloid 4 (TRPV4) cation channel mutation. Exp Mol Med 2012; 44:707-22. [PMID: 23143559 PMCID: PMC3538978 DOI: 10.3858/emm.2012.44.12.080] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2012] [Indexed: 12/23/2022] Open
Abstract
The transient receptor potential vanilloid 4 (TRPV4) cation channel, a member of the TRP vanilloid subfamily, is expressed in a broad range of tissues where it participates in the generation of Ca²⁺ signals and/or depolarization of the membrane potential. Regulation of TRPV4 abundance at the cell surface is critical for osmo- and mechanotransduction. Defects in TRPV4 are the cause of several human diseases, including brachyolmia type 3 (MIM:113500) (also known as brachyrachia or spondylometaphyseal dysplasia Kozlowski type [MIM:118452]), and metatropic dysplasia (MIM:156530) (also called metatropic dwarfism or parastremmatic dwarfism [MIM:168400]). These bone dysplasia mutants are characterized by severe dwarfism, kyphoscoliosis, distortion and bowing of the extremities, and contractures of the large joints. These diseases are characterized by a combination of decreased bone density, bowing of the long bones, platyspondyly, and striking irregularities of endochondral ossification with areas of calcific stippling and streaking in radiolucent epiphyses, metaphyses, and apophyses. In this review, we discuss the potential effect of the mutation on the regulation of TRPV4 functions, which are related to human diseases through deviated function. In particular, we emphasize how the constitutive active TRPV4 mutant affects endochondral ossification with a reduced number of hypertrophic chondrocytes and the presence of cartilage islands within the zone of primary mineralization. In addition, we summarize current knowledge about the role of TRPV4 in the pathogenesis of several diseases.
Collapse
Affiliation(s)
- Sang Sun Kang
- Department of Biology Education Chungbuk National University Cheongju 361-763, Korea.
| | | | | | | |
Collapse
|
108
|
Vasquez I, Tan N, Boonyasampant M, Koppitch KA, Lansman JB. Partial opening and subconductance gating of mechanosensitive ion channels in dystrophic skeletal muscle. J Physiol 2012; 590:6167-85. [PMID: 22966155 PMCID: PMC3530124 DOI: 10.1113/jphysiol.2012.240044] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 09/03/2012] [Indexed: 12/31/2022] Open
Abstract
We recorded the activity of single mechanosensitive (MS) ion channels in skeletal muscle from the mdx mouse, a deletion mutant that lacks the cytoskeletal protein, dystrophin. Experiments were designed to examine the influence of dystrophin, a major component of skeletal muscle costameres, on the behaviour of single MS channels. In the majority of recordings from cell-attached patches, MS channels have a conductance of ∼23 pS. Recordings from some patches, however, showed a smaller conductance channel of ∼7-14 pS. Large and small conductance channels were detected in a single patch and showed serial, non-random gating, suggesting different opening levels of a single channel. Analysis of the distribution of current amplitudes within the open channel showed MS channels fluctuate between subconductance levels. MS channels in dystrophic muscle spend ∼60% of the time at smaller subconductance levels, often failing to reach the fully open level. Applying pressure to the membrane of mdx fibres increases in a graded manner occupancy of the fully open state, while reducing occupancy of subconductance levels. Recordings also show partial openings of MS channels in both wild-type and mdx muscle that fail to reach the fully open state. Partial openings occur at a higher frequency in mdx muscle and reflect occupancy of subconductance levels seen during complete activations. In muscle from mdx/utrn(-/-) double knockout mice, MS channels also spend more time at subconductance levels than the fully open state. Conductance variability of MS channels may represent gating of a heteromeric protein composed of different channel subunits. The results also show that partial opening and prolonged burst duration are distinct mechanisms that contribute to excess Ca(2+) entry in dystrophic muscle.
Collapse
Affiliation(s)
- Ivan Vasquez
- Department of Cellular & Molecular Pharmacology, School of Medicine, University of California, San Francisco, CA 94143-0450, USA
| | | | | | | | | |
Collapse
|
109
|
Single Mechanosensitive and Ca2+-Sensitive Channel Currents Recorded from Mouse and Human Embryonic Stem Cells. J Membr Biol 2012. [DOI: 10.1007/s00232-012-9523-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
|
110
|
Dahan D, Ducret T, Quignard JF, Marthan R, Savineau JP, Estève E. Implication of the ryanodine receptor in TRPV4-induced calcium response in pulmonary arterial smooth muscle cells from normoxic and chronically hypoxic rats. Am J Physiol Lung Cell Mol Physiol 2012; 303:L824-33. [DOI: 10.1152/ajplung.00244.2011] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is a growing body of evidence indicating that transient receptor potential (TRP) channels are implicated in calcium signaling and various cellular functions in the pulmonary vasculature. The aim of this study was to investigate the expression, functional role, and coupling to reticulum calcium channels of the type 4 vanilloid TRP subfamily (TRPV4) in the pulmonary artery from both normoxic (Nx) and chronically hypoxic (CH) rats. Activation of TRPV4 with the specific agonist 4α-phorbol-12,13-didecanoate (4α-PDD, 5 μM) increased the intracellular calcium concentration ([Ca2+]i). This effect was significantly reduced by a high concentration of ryanodine (100 μM) or chronic caffeine (5 mM) that blocked ryanodine receptor (RyR) but was insensitive to xestospongin C (10 μM), an inositol trisphosphate receptor antagonist. Inhibition of RyR1 and RyR3 only with 10 μM of dantrolene did not attenuate the 4α-PDD-induced [Ca2+]i increase. Western blotting experiments revealed the expression of TRPV4 and RyR2 with an increase in both receptors in pulmonary arteries from CH rats vs. Nx rats. Accordingly, the 4α-PDD-activated current, measured with patch-clamp technique, was increased in pulmonary artery smooth muscle cells (PASMC) from CH rats vs. Nx rats. 4α-PDD increased isometric tension in artery rings, and this response was also potentiated under chronic hypoxia conditions. 4α-PDD-induced calcium response, current, and contraction were all inhibited by the selective TRPV4 blocker HC-067047. Collectively, our findings provide evidence of the interplay between TRPV4 and RyR2 in the Ca2+ release mechanism and contraction in PASMC. This study provides new insights onto the complex calcium signaling in PASMC and point out the importance of the TRPV4-RyR2 signaling pathway under hypoxic conditions that may lead to pulmonary hypertension.
Collapse
Affiliation(s)
- Diana Dahan
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France
- Institut National de la Santé et de la Recherche Médicale, U 1045, Bordeaux, France; and
| | - Thomas Ducret
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France
- Institut National de la Santé et de la Recherche Médicale, U 1045, Bordeaux, France; and
| | - Jean-François Quignard
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France
- Institut National de la Santé et de la Recherche Médicale, U 1045, Bordeaux, France; and
| | - Roger Marthan
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France
- Institut National de la Santé et de la Recherche Médicale, U 1045, Bordeaux, France; and
| | - Jean-Pierre Savineau
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France
- Institut National de la Santé et de la Recherche Médicale, U 1045, Bordeaux, France; and
| | - Eric Estève
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France
- Institut National de la Santé et de la Recherche Médicale, U 1045, Bordeaux, France; and
- Université Grenoble 1 UJF, Institut National de la Santé et de la Recherche Médicale U1042, La Tronche, France
| |
Collapse
|
111
|
Premkumar LS, Abooj M. TRP channels and analgesia. Life Sci 2012; 92:415-24. [PMID: 22910182 DOI: 10.1016/j.lfs.2012.08.010] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 07/25/2012] [Accepted: 08/02/2012] [Indexed: 01/07/2023]
Abstract
Since cloning and characterizing the first nociceptive ion channel Transient Receptor Potential (TRP) Vanilloid 1 (TRPV1), other TRP channels involved in nociception have been cloned and characterized, which include TRP Vanilloid 2 (TRPV2), TRP Vanilloid 3 (TRPV3), TRP Vanilloid 4 (TRPV4), TRP Ankyrin 1 (TRPA1) and TRP Melastatin 8 (TRPM8), more recently TRP Canonical 1, 5, 6 (TRPC1, 5, 6), TRP Melastatin 2 (TRPM2) and TRP Melastatin 3 (TRPM3). These channels are predominantly expressed in C and Aδ nociceptors and transmit noxious thermal, mechanical and chemical sensitivities. TRP channels are modulated by pro-inflammatory mediators, neuropeptides and cytokines. Significant advances have been made targeting these receptors either by antagonists or agonists to treat painful conditions. In this review, we will discuss TRP channels as targets for next generation analgesics and the side effects that may ensue as a result of blocking/activating these receptors, because they are also involved in physiological functions such as release of vasoactive neuropeptides and regulation of vascular tone, maintenance of the body temperature, gastrointestinal motility, urinary bladder control, etc.
Collapse
Affiliation(s)
- Louis S Premkumar
- Department of Pharmacology, Southern Illinois University School of Medicine Springfield, IL 62702, USA.
| | | |
Collapse
|
112
|
Involvement of TRPV1 and TRPV4 channels in migration of rat pulmonary arterial smooth muscle cells. Pflugers Arch 2012; 464:261-72. [PMID: 22820913 DOI: 10.1007/s00424-012-1136-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 06/26/2012] [Indexed: 12/11/2022]
Abstract
Pulmonary hypertension, the main disease of the pulmonary circulation, is characterized by an increase in pulmonary vascular resistance, involving proliferation and migration of pulmonary arterial smooth muscle cells (PASMC). However, cellular and molecular mechanisms underlying these phenomena remain to be identified. In the present study, we thus investigated in rat intrapulmonary arteries (1) the expression and the functional activity of TRPV1 and TRPV4, (2) the PASMC migration triggered by these TRPV channels, and (3) the associated reorganization of the cytoskeleton. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated expression of TRPV1 and TRPV4 mRNA in rat intrapulmonary arteries. These results were confirmed at the protein level by western blot. Using microspectrofluorimetry (indo-1), we show that capsaicin and 4α-phorbol-12,13-didecanoate (4α-PDD), selective agonists of TRPV1 and TRPV4, respectively, increased the intracellular calcium concentration of PASMC. Furthermore, stimulation of TRPV1 and TRPV4 induced PASMC migratory responses, as assessed by two different methods (a modified Boyden chamber assay and a wound-healing migration assay). This response cannot seem to be attributed to a proliferative effect as assessed by BrdU and Wst-1 colorimetric methods. Capsaicin- and 4α-PDD-induced calcium and migratory responses were inhibited by the selective TRPV1 and TRPV4 blockers, capsazepine and HC067047, respectively. Finally, as assessed by immunostaining, these TRPV-induced migratory responses were associated with reorganization of the F-actin cytoskeleton and the tubulin and intermediate filament networks. In conclusion, these data point out, for the first time, the implication of TRPV1 and TRPV4 in rat PASMC migration, suggesting the implication of these TRPV channels in the physiopathology of pulmonary hypertension.
Collapse
|
113
|
Su Z, Anishkin A, Kung C, Saimi Y. The core domain as the force sensor of the yeast mechanosensitive TRP channel. ACTA ACUST UNITED AC 2012; 138:627-40. [PMID: 22124118 PMCID: PMC3226973 DOI: 10.1085/jgp.201110693] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Stretch-activated conductances are commonly encountered in careful electric recordings. Those of known proteins (TRP, MscL, MscS, K2p, Kv, etc.) all share a core, which houses the ion pathway and the gate, but no recognizable force-sensing domain. Like animal TRPs, the yeast TRPY1 is polymodal, activated by stretch force, Ca2+, etc. To test whether its S5–S6 core senses the stretch force, we tried to uncouple it from the peripheral domains by strategic peptide insertions to block the covalent core–periphery interactions. Insertion of long unstructured peptides should distort, if not disrupt, protein structures that transmit force. Such insertions between S6 and the C-terminal tail largely removed Ca2+ activation, showing their effectiveness. However, such insertions as well as those between S5 and the N-terminal region, which includes S1–S4, did not significantly alter mechanosensitivity. Even insertions at both locations flanking the S5–S6 core did not much alter mechanosensitivity. Tryptophan scanning mutations in S5 were also constructed to perturb possible noncovalent core–periphery contacts. The testable tryptophan mutations also have little or no effects on mechanosensitivity. Boltzmann fits of the wild-type force–response curves agree with a structural homology model for a stretch-induced core expansion of ∼2 nm2 upon opening. We hypothesize that membrane tension pulls on S5–S6, expanding the core and opening the TRPY1 gate. The core being the major force sensor offers the simplest, though not the only, explanation of why so many channels of disparate designs are mechanically sensitive. Compared with the bacterial MscL, TRPY1 is much less sensitive to force, befitting a polymodal channel that relies on multiple stimuli.
Collapse
Affiliation(s)
- Zhenwei Su
- Laboratory of Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | | | | | |
Collapse
|
114
|
Sonkusare SK, Bonev AD, Ledoux J, Liedtke W, Kotlikoff MI, Heppner TJ, Hill-Eubanks DC, Nelson MT. Elementary Ca2+ signals through endothelial TRPV4 channels regulate vascular function. Science 2012; 336:597-601. [PMID: 22556255 DOI: 10.1126/science.1216283] [Citation(s) in RCA: 447] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Major features of the transcellular signaling mechanism responsible for endothelium-dependent regulation of vascular smooth muscle tone are unresolved. We identified local calcium (Ca(2+)) signals ("sparklets") in the vascular endothelium of resistance arteries that represent Ca(2+) influx through single TRPV4 cation channels. Gating of individual TRPV4 channels within a four-channel cluster was cooperative, with activation of as few as three channels per cell causing maximal dilation through activation of endothelial cell intermediate (IK)- and small (SK)-conductance, Ca(2+)-sensitive potassium (K(+)) channels. Endothelial-dependent muscarinic receptor signaling also acted largely through TRPV4 sparklet-mediated stimulation of IK and SK channels to promote vasodilation. These results support the concept that Ca(2+) influx through single TRPV4 channels is leveraged by the amplifier effect of cooperative channel gating and the high Ca(2+) sensitivity of IK and SK channels to cause vasodilation.
Collapse
Affiliation(s)
- Swapnil K Sonkusare
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA
| | | | | | | | | | | | | | | |
Collapse
|
115
|
Maksaev G, Haswell ES. Expression and characterization of the bacterial mechanosensitive channel MscS in Xenopus laevis oocytes. ACTA ACUST UNITED AC 2011; 138:641-9. [PMID: 22084416 PMCID: PMC3226970 DOI: 10.1085/jgp.201110723] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have successfully expressed and characterized mechanosensitive channel of small conductance (MscS) from Escherichia coli in oocytes of the African clawed frog, Xenopus laevis. MscS expressed in oocytes has the same single-channel conductance and voltage dependence as the channel in its native environment. Two hallmarks of MscS activity, the presence of conducting substates at high potentials and reversible adaptation to a sustained stimulus, are also exhibited by oocyte-expressed MscS. In addition to its ease of use, the oocyte system allows the user to work with relatively large patches, which could be an advantage for the visualization of membrane deformation. Furthermore, MscS can now be compared directly to its eukaryotic homologues or to other mechanosensitive channels that are not easily studied in E. coli.
Collapse
Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | | |
Collapse
|
116
|
Adapala RK, Talasila PK, Bratz IN, Zhang DX, Suzuki M, Meszaros JG, Thodeti CK. PKCα mediates acetylcholine-induced activation of TRPV4-dependent calcium influx in endothelial cells. Am J Physiol Heart Circ Physiol 2011; 301:H757-65. [PMID: 21705673 PMCID: PMC3302191 DOI: 10.1152/ajpheart.00142.2011] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 06/16/2011] [Indexed: 11/22/2022]
Abstract
Transient receptor potential vanilloid channel 4 (TRPV4) is a polymodally activated nonselective cationic channel implicated in the regulation of vasodilation and hypertension. We and others have recently shown that cyclic stretch and shear stress activate TRPV4-mediated calcium influx in endothelial cells (EC). In addition to the mechanical forces, acetylcholine (ACh) was shown to activate TRPV4-mediated calcium influx in endothelial cells, which is important for nitric oxide-dependent vasodilation. However, the molecular mechanism through which ACh activates TRPV4 is not known. Here, we show that ACh-induced calcium influx and endothelial nitric oxide synthase (eNOS) phosphorylation but not calcium release from intracellular stores is inhibited by a specific TRPV4 antagonist, AB-159908. Importantly, activation of store-operated calcium influx was not altered in the TRPV4 null EC, suggesting that TRPV4-dependent calcium influx is mediated through a receptor-operated pathway. Furthermore, we found that ACh treatment activated protein kinase C (PKC) α, and inhibition of PKCα activity by the specific inhibitor Go-6976, or expression of a kinase-dead mutant of PKCα but not PKCε or downregulation of PKCα expression by chronic 12-O-tetradecanoylphorbol-13-acetate treatment, completely abolished ACh-induced calcium influx. Finally, we found that ACh-induced vasodilation was inhibited by the PKCα inhibitor Go-6976 in small mesenteric arteries from wild-type mice, but not in TRPV4 null mice. Taken together, these findings demonstrate, for the first time, that a specific isoform of PKC, PKCα, mediates agonist-induced receptor-mediated TRPV4 activation in endothelial cells.
Collapse
Affiliation(s)
- Ravi K Adapala
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, Ohio 44272, USA
| | | | | | | | | | | | | |
Collapse
|
117
|
Abstract
Transient receptor potential channels, of the vanilloid subtype (TRPV), act as sensory mediators, being activated by endogenous ligands, heat, mechanical and osmotic stress. Within the vasculature, TRPV channels are expressed in smooth muscle cells, endothelial cells, as well as in peri-vascular nerves. Their varied distribution and polymodal activation properties make them ideally suited to a role in modulating vascular function, perceiving and responding to local environmental changes. In endothelial cells, TRPV1 is activated by endocannabinoids, TRPV3 by dietary agonists and TRPV4 by shear stress, epoxyeicosatrienoic acids (EETs) and downstream of Gq-coupled receptor activation. Upon activation, these channels contribute to vasodilation via nitric oxide, prostacyclin and intermediate/small conductance potassium channel-dependent pathways. In smooth muscle, TRPV4 is activated by endothelial-derived EETs, leading to large conductance potassium channel activation and smooth muscle hyperpolarization. Conversely, smooth muscle TRPV2 channels contribute to global calcium entry and may aid constriction. TRPV1 and TRPV4 are expressed in sensory nerves and can cause vasodilation through calcitonin gene-related peptide and substance P release as well as mediating vascular function via the baroreceptor reflex (TRPV1) or via increasing sympathetic outflow during osmotic stress (TRPV4). Thus, TRPV channels play important roles in the regulation of normal and pathological cellular function in the vasculature.
Collapse
Affiliation(s)
- R L Baylie
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, USA.
| | | |
Collapse
|
118
|
Holzer P. Transient receptor potential (TRP) channels as drug targets for diseases of the digestive system. Pharmacol Ther 2011; 131:142-70. [PMID: 21420431 PMCID: PMC3107431 DOI: 10.1016/j.pharmthera.2011.03.006] [Citation(s) in RCA: 183] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 03/01/2011] [Indexed: 12/12/2022]
Abstract
Approximately 20 of the 30 mammalian transient receptor potential (TRP) channel subunits are expressed by specific neurons and cells within the alimentary canal. They subserve important roles in taste, chemesthesis, mechanosensation, pain and hyperalgesia and contribute to the regulation of gastrointestinal motility, absorptive and secretory processes, blood flow, and mucosal homeostasis. In a cellular perspective, TRP channels operate either as primary detectors of chemical and physical stimuli, as secondary transducers of ionotropic or metabotropic receptors, or as ion transport channels. The polymodal sensory function of TRPA1, TRPM5, TRPM8, TRPP2, TRPV1, TRPV3 and TRPV4 enables the digestive system to survey its physical and chemical environment, which is relevant to all processes of digestion. TRPV5 and TRPV6 as well as TRPM6 and TRPM7 contribute to the absorption of Ca²⁺ and Mg²⁺, respectively. TRPM7 participates in intestinal pacemaker activity, and TRPC4 transduces muscarinic acetylcholine receptor activation to smooth muscle contraction. Changes in TRP channel expression or function are associated with a variety of diseases/disorders of the digestive system, notably gastro-esophageal reflux disease, inflammatory bowel disease, pain and hyperalgesia in heartburn, functional dyspepsia and irritable bowel syndrome, cholera, hypomagnesemia with secondary hypocalcemia, infantile hypertrophic pyloric stenosis, esophageal, gastrointestinal and pancreatic cancer, and polycystic liver disease. These implications identify TRP channels as promising drug targets for the management of a number of gastrointestinal pathologies. As a result, major efforts are put into the development of selective TRP channel agonists and antagonists and the assessment of their therapeutic potential.
Collapse
Key Words
- chemesthesis
- chemosensation
- gastrointestinal cancer
- gastrointestinal motility
- hypersensitivity
- hyperalgesia
- inflammation
- inflammatory bowel disease
- mechanosensation
- pain
- taste
- transducers
- trpa1
- trpc4
- trpc6
- trpm5
- trpm6
- trpv1
- trpv4
- trpv6
- aitc, allyl isothiocyanate
- cck, cholecystokinin
- cgrp, calcitonin gene-related peptide
- drg, dorsal root ganglion
- dss, dextran sulfate sodium
- gi, gastrointestinal
- gpcr, g protein-coupled receptor
- 5-ht, 5-hydroxytryptamine
- icc, interstitial cell of cajal
- mrna, messenger ribonucleic acid
- par, protease-activated receptor
- pkd, polycystic kidney disease
- rna, ribonucleic acid
- sirna, small interfering ribonucleic acid
- tnbs, trinitrobenzene sulfonic acid
- trp, transient receptor potential
- trpa, transient receptor potential ankyrin
- trpc, transient receptor potential canonical (or classical)
- trpm, transient receptor potential melastatin
- trpp, transient receptor potential polycystin
- trpv, transient receptor potential vanilloid
Collapse
Affiliation(s)
- Peter Holzer
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
| |
Collapse
|
119
|
Ryskamp DA, Witkovsky P, Barabas P, Huang W, Koehler C, Akimov NP, Lee SH, Chauhan S, Xing W, Rentería RC, Liedtke W, Križaj D. The polymodal ion channel transient receptor potential vanilloid 4 modulates calcium flux, spiking rate, and apoptosis of mouse retinal ganglion cells. J Neurosci 2011; 31:7089-101. [PMID: 21562271 PMCID: PMC3109951 DOI: 10.1523/jneurosci.0359-11.2011] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 03/10/2011] [Accepted: 03/26/2011] [Indexed: 12/18/2022] Open
Abstract
Sustained increase in intraocular pressure represents a major risk factor for eye disease, yet the cellular mechanisms of pressure transduction in the posterior eye are essentially unknown. Here we show that the mouse retina expresses mRNA and protein for the polymodal transient receptor potential vanilloid 4 (TRPV4) cation channel known to mediate osmotransduction and mechanotransduction. TRPV4 antibodies labeled perikarya, axons, and dendrites of retinal ganglion cells (RGCs) and intensely immunostained the optic nerve head. Müller glial cells, but not retinal astrocytes or microglia, also expressed TRPV4 immunoreactivity. The selective TRPV4 agonists 4α-PDD and GSK1016790A elevated [Ca2+]i in dissociated RGCs in a dose-dependent manner, whereas the TRPV1 agonist capsaicin had no effect on [Ca2+](RGC). Exposure to hypotonic stimulation evoked robust increases in [Ca2+](RGC). RGC responses to TRPV4-selective agonists and hypotonic stimulation were absent in Ca2+ -free saline and were antagonized by the nonselective TRP channel antagonists Ruthenium Red and gadolinium, but were unaffected by the TRPV1 antagonist capsazepine. TRPV4-selective agonists increased the spiking frequency recorded from intact retinas recorded with multielectrode arrays. Sustained exposure to TRPV4 agonists evoked dose-dependent apoptosis of RGCs. Our results demonstrate functional TRPV4 expression in RGCs and suggest that its activation mediates response to membrane stretch leading to elevated [Ca2+]i and augmented excitability. Excessive Ca2+ influx through TRPV4 predisposes RGCs to activation of Ca2+ -dependent proapoptotic signaling pathways, indicating that TRPV4 is a component of the response mechanism to pathological elevations of intraocular pressure.
Collapse
Affiliation(s)
- Daniel A. Ryskamp
- Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center
- Interdepartmental Program in Neuroscience, and
| | - Paul Witkovsky
- Department of Ophthalmology, New York University School of Medicine, New York, New York 10016
| | - Peter Barabas
- Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center
| | - Wei Huang
- Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center
| | - Christopher Koehler
- Department of Physiology and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas, and
| | - Nikolay P. Akimov
- Department of Physiology and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas, and
| | - Suk Hee Lee
- Department of Medicine and Neurobiology, and Center for Translational Neuroscience, Duke University Medical Center, Durham, North Carolina 27710
| | - Shiwani Chauhan
- Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center
| | - Wei Xing
- Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center
| | - René C. Rentería
- Department of Physiology and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas, and
| | - Wolfgang Liedtke
- Department of Medicine and Neurobiology, and Center for Translational Neuroscience, Duke University Medical Center, Durham, North Carolina 27710
| | - David Križaj
- Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center
- Interdepartmental Program in Neuroscience, and
- Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah 84132
| |
Collapse
|
120
|
Loukin S, Su Z, Kung C. Increased basal activity is a key determinant in the severity of human skeletal dysplasia caused by TRPV4 mutations. PLoS One 2011; 6:e19533. [PMID: 21573172 PMCID: PMC3088684 DOI: 10.1371/journal.pone.0019533] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 04/04/2011] [Indexed: 02/01/2023] Open
Abstract
TRPV4 is a mechanically activated Ca2+-passing channel implicated in the sensing of forces, including those acting on bones. To date, 33 mutations are known to affect human bone development to different extents. The spectrum of these skeletal dysplasias (SD) ranges from dominantly inherited mild brachylomia (BO) to neonatal lethal forms of metatropic dysplasia (MD). Complexities of the results from fluorescence and electrophysiological studies have led to questions on whether channel activity is a good predictor of disease severity. Here we report on a systematic examination of 14 TRPV4 mutant alleles covering the entire SD spectrum. Expressed in Xenopus oocyte and without any stimulation, the wild-type channel had a ∼1% open probability (Po) while those of most of the lethal MD channels approached 100%. All mutant channels had higher basal open probabilities, which limited their further increase by agonist or hypotonicity. The magnitude of this limitation revealed a clear correlation between the degree of over-activity (the molecular phenotype) and the severity of the disease over the entire spectrum (the biological phenotype). Thus, while other factors are at play, our results are consistent with the increased TRPV4 basal activity being a critical determinant of the severity of skeletal dysplasia. We discuss how the channel over-activity may lead to the “gain-of-function” phenotype and speculate that the function of wild-type TRPV4 may be secondary in normal bone development but crucial in an acute process such as fracture repair in the adult.
Collapse
Affiliation(s)
- Stephen Loukin
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- * E-mail:
| | - Zhenwei Su
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Ching Kung
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- Department of Genetics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| |
Collapse
|
121
|
Fecto F, Shi Y, Huda R, Martina M, Siddique T, Deng HX. Mutant TRPV4-mediated toxicity is linked to increased constitutive function in axonal neuropathies. J Biol Chem 2011; 286:17281-91. [PMID: 21454511 DOI: 10.1074/jbc.m111.237685] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in TRPV4 have been linked to three distinct axonal neuropathies. However, the pathogenic mechanism underlying these disorders remains unclear. Both gain and loss of calcium channel activity of the mutant TRPV4 have been suggested. Here, we show that the three previously reported TRPV4 mutant channels have a physiological localization and display an increased calcium channel activity, leading to increased cytotoxicity in three different cell types. Patch clamp experiments showed that cells expressing mutant TRPV4 have much larger whole-cell currents than those expressing the wild-type TRPV4 channel. Single channel recordings showed that the mutant channels have higher open probability, due to a modification of gating, and no change in single-channel conductance. These data support the hypothesis that a "gain of function" mechanism, possibly leading to increased intracellular calcium influx, underlies the pathogenesis of the TRPV4-linked axonal neuropathies, and may have immediate implications for designing rational therapies.
Collapse
Affiliation(s)
- Faisal Fecto
- Division of Neuromuscular Medicine, Davee Department of Neurology and Clinical Neurosciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
| | | | | | | | | | | |
Collapse
|
122
|
|