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Nikolaev YA, Cox CD, Ridone P, Rohde PR, Cordero-Morales JF, Vásquez V, Laver DR, Martinac B. Mammalian TRP ion channels are insensitive to membrane stretch. J Cell Sci 2019; 132:jcs238360. [PMID: 31722978 PMCID: PMC6918743 DOI: 10.1242/jcs.238360] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 10/29/2019] [Indexed: 12/27/2022] Open
Abstract
TRP channels of the transient receptor potential ion channel superfamily are involved in a wide variety of mechanosensory processes, including touch sensation, pain, blood pressure regulation, bone loading and detection of cerebrospinal fluid flow. However, in many instances it is unclear whether TRP channels are the primary transducers of mechanical force in these processes. In this study, we tested stretch activation of eleven TRP channels from six mammalian subfamilies. We found that these TRP channels were insensitive to short membrane stretches in cellular systems. Furthermore, we purified TRPC6 and demonstrated its insensitivity to stretch in liposomes, an artificial bilayer system free from cellular components. Additionally, we demonstrated that, when expressed in C. elegans neurons, mouse TRPC6 restores the mechanoresponse of a touch insensitive mutant but requires diacylglycerol for activation. These results strongly suggest that the mammalian members of the TRP ion channel family are insensitive to tension induced by cell membrane stretching and, thus, are more likely to be activated by cytoplasmic tethers or downstream components and to act as amplifiers of cellular mechanosensory signaling cascades.
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Affiliation(s)
- Yury A Nikolaev
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
- Human Physiology, School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle 2308, Australia
| | - Charles D Cox
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
| | - Pietro Ridone
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
| | - Paul R Rohde
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
| | - Julio F Cordero-Morales
- Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis 38163, USA
| | - Valeria Vásquez
- Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis 38163, USA
| | - Derek R Laver
- Human Physiology, School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle 2308, Australia
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
- St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney 2052, Australia
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52
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Servin‐Vences MR, Poole K, Sporbert A, Lewin GR, Margineanu A. Collagen Organization Within the Cartilage of
Trpv4
−/−
Mice Studied with Two‐Photon Microscopy and Polarized Second Harmonic Generation. Cytometry A 2019; 97:504-514. [DOI: 10.1002/cyto.a.23900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/19/2019] [Accepted: 09/09/2019] [Indexed: 02/06/2023]
Affiliation(s)
| | - Kate Poole
- Molecular Physiology of Somatic SensationMax Delbrück Centrum Berlin Germany
| | - Anje Sporbert
- Advanced Light MicroscopyMax Delbrück Centrum Berlin Germany
| | - Gary R. Lewin
- Molecular Physiology of Somatic SensationMax Delbrück Centrum Berlin Germany
| | - Anca Margineanu
- Advanced Light MicroscopyMax Delbrück Centrum Berlin Germany
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53
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Morishita K, Watanabe K, Ichijo H. Cell volume regulation in cancer cell migration driven by osmotic water flow. Cancer Sci 2019; 110:2337-2347. [PMID: 31120184 PMCID: PMC6676112 DOI: 10.1111/cas.14079] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 05/17/2019] [Accepted: 05/21/2019] [Indexed: 12/12/2022] Open
Abstract
Cancer metastasis is the most frequent cause of death for patients with cancer. The main current treatment for cancer metastasis is chemotherapy targeting cancer cells’ ability to proliferate. However, some types of cancer cells show resistance to chemotherapy. Recently, cancer cell migration has become the subject of interest as a novel target of cancer therapy. Cell migration requires many factors, such as the cytoskeleton, cell‐matrix adhesion and cell volume regulation. Here, we focus on cell volume regulation and the role of ion/water transport systems in cell migration. Transport proteins, such as ion channels, ion carriers, and aquaporins, are indispensable for cell volume regulation under steady‐state conditions and during exposure to osmotic stress. Studies from the last ~25 years have revealed that cell volume regulation also plays an important role in the process of cell migration. Water flow in accordance with localized osmotic gradients generated by ion transport contributes to the driving force for cell migration. Moreover, it has been reported that metastatic cancer cells have higher expression of these transport proteins than nonmetastatic cancer cells. Thus, ion/water transport proteins involved in cell volume regulation and cell migration could be novel therapeutic targets for cancer metastasis. In this review, after presenting the importance of ion/water transport systems in cell volume regulation, we discuss the roles of transport proteins in a pathophysiological context, especially in the context of cancer cell migration.
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Affiliation(s)
- Kazuhiro Morishita
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Kengo Watanabe
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Hidenori Ichijo
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
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54
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Teng J, Anishkin A, Kung C, Blount P. Human mutations highlight an intersubunit cation-π bond that stabilizes the closed but not open or inactivated states of TRPV channels. Proc Natl Acad Sci U S A 2019; 116:9410-9416. [PMID: 31010928 PMCID: PMC6511060 DOI: 10.1073/pnas.1820673116] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
An adequate response of a living cell to the ever-changing environment requires integration of numerous sensory inputs. In many cases, it can be achieved even at the level of a single receptor molecule. Polymodal transient receptor potential (TRP) channels have been shown to integrate mechanical, chemical, electric, and thermal stimuli. Inappropriate gating can lead to pathologies. Among the >60 known TRP vanilloid subfamily (V) 4 mutations that interfere with bone development are Y602C or R616Q at the S4-S5 linker. A cation-π bond between the conservative residues Y602 and R616 of neighboring subunits appears likely in many homologous channel structures in a closed state. Our experiments with TRPV4 mutants indicate that the resting-closed state remains stable while the bond is substituted by a salt bridge or disulfide bond, whereas disruption of the contact by mutations like Y602C or R616Q produces gain-of-function phenotypes when TRPV4 is heterologously expressed in the Xenopus oocyte or yeast. Our data indicate that the Y602-R616 cation-π interactions link the four S4-S5 linker helices together, forming a girdle backing the closed gate. Analogous cation-π bonds and the girdle are seen in many closed TRP channel structures. This girdle is not observed in the cryo-EM structure of amphibian TRPV4 (Protein Data Bank ID code 6BBJ), which appears to be in a different impermeable state-we hypothesize this is the inactivated state.
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Affiliation(s)
- Jinfeng Teng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742;
| | - Ching Kung
- Laboratory of Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706;
- Department of Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390;
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55
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Xu B, Xing R, Huang Z, Yin S, Li X, Zhang L, Ding L, Wang P. Excessive mechanical stress induces chondrocyte apoptosis through TRPV4 in an anterior cruciate ligament-transected rat osteoarthritis model. Life Sci 2019; 228:158-166. [PMID: 31055086 DOI: 10.1016/j.lfs.2019.05.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 04/29/2019] [Accepted: 05/01/2019] [Indexed: 11/19/2022]
Abstract
AIMS Chondrocyte apoptosis is the most common pathological feature of cartilage in osteoarthritis (OA). Excessive mechanical stress can induce chondrocyte apoptosis and destroy cartilage tissue. Transient receptor potential channel vanilloid 4 (TRPV4) is a mechanosensitive ion channel that mediates chondrocyte response to mechanical stress. Here, we investigated the potential role of TRPV4 in chondrocyte apoptosis induced by excessive mechanical stress. MAIN METHODS Using a rat OA anterior cruciate-ligament transection (ALCT) model, we detected immunolocalization of calmodulin protein and mRNA and protein levels of TRPV4, calmodulin, and cleaved caspase-8 in articular cartilage. Primary chondrocytes were isolated and cultured in vitro, and Fluo-4AM staining was used to assess intracellular Ca2+ levels in order to evaluate TRPV4-mediated Ca2+ influx. Flow cytometry and western blot were performed to detect apoptosis and apoptosis-related protein levels in chondrocytes, respectively. KEY FINDINGS TRPV4 was upregulated in ALCT-induced OA articular cartilage, and we found that administration of a TRPV4 inhibitor attenuated cartilage degeneration. Additionally, TRPV4 specifically mediated extracellular Ca2+ influx, leading to chondrocyte apoptosis in vitro, which was inhibited by transfection of TRPV4 small-interfering RNA or administration of a TRPV4 inhibitor. Moreover, increased Ca2+ influx triggered apoptosis by upregulating FAS-associated protein with death domain and cleaved caspase-3, -6, -7, and -8 levels, with these effects abolished by TRPV4 knockdown or TRPV4 inhibition. SIGNIFICANCE These results indicated that TRPV4 was upregulated in OA articular cartilage, and that excessive mechanical stress might induce chondrocyte apoptosis via TRPV4-mediated Ca2+ influx, suggesting TRPV4 as a potential drug target in OA.
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Affiliation(s)
- Bo Xu
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China; Key Laboratory for Metabolic Diseases in Chinese Medicine, First College of Clinical Medicine, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Runlin Xing
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China
| | - Zhengquan Huang
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China
| | - Songjiang Yin
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China
| | - Xiaochen Li
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China
| | - Li Zhang
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China
| | - Liang Ding
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China
| | - Peimin Wang
- Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, China; Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, China.
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56
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Shear force modulates the activity of acid-sensing ion channels at low pH or in the presence of non-proton ligands. Sci Rep 2019; 9:6781. [PMID: 31043630 PMCID: PMC6494901 DOI: 10.1038/s41598-019-43097-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 04/16/2019] [Indexed: 12/17/2022] Open
Abstract
Acid-sensing ion channels (ASICs) belong to the degenerin/epithelial sodium channel protein family that form mechanosensitive ion channels. Evidence as to whether or not ASICs activity is directly modulated by mechanical force is lacking. Human ASICs (hASIC1V3, hASIC2a and hASIC3a) were heterologously expressed as homomeric channels in Xenopus oocytes and two-electrode voltage-clamp recordings were performed. hASIC3a was expressed in HEK-293 cells and currents measured by whole-cell patch-clamp recordings. ASIC currents in response to shear force (SF) were measured at pH 7.4, acidic pH, or in the presence of non-proton ligands at pH 7.4. SF was applied via a fluid stream generated through a pressurized perfusion system. No effect was observed at pH 7.4. Increased transient currents for each homomeric channel were observed when elevated SF was applied in conjunction with acidic pH (6.0-4.0). The sustained current was not (hASIC2a) or only slightly increased (hASIC1V3 and hASIC3a). SF-induced effects were not seen in water injected oocytes and were blocked by amiloride. Non-proton ligands activated a persistent current in hASIC1V3 and cASIC1 (MitTx) and hASIC3a (GMQ) at pH 7.4. Here SF caused a further current increase. Results suggest that ASICs do have an intrinsic ability to respond to mechanical force, supporting their role as mechanosensors in certain local environments.
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57
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Modulators of Transient Receptor Potential (TRP) Channels as Therapeutic Options in Lung Disease. Pharmaceuticals (Basel) 2019; 12:ph12010023. [PMID: 30717260 PMCID: PMC6469169 DOI: 10.3390/ph12010023] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 01/28/2019] [Accepted: 01/29/2019] [Indexed: 12/25/2022] Open
Abstract
The lungs are essential for gas exchange and serve as the gateways of our body to the external environment. They are easily accessible for drugs from both sides, the airways and the vasculature. Recent literature provides evidence for a role of Transient Receptor Potential (TRP) channels as chemosensors and essential members of signal transduction cascades in stress-induced cellular responses. This review will focus on TRP channels (TRPA1, TRPC6, TRPV1, and TRPV4), predominantly expressed in non-neuronal lung tissues and their involvement in pathways associated with diseases like asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), lung fibrosis, and edema formation. Recently identified specific modulators of these channels and their potential as new therapeutic options as well as strategies for a causal treatment based on the mechanistic understanding of molecular events will also be evaluated.
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58
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Zakany F, Pap P, Papp F, Kovacs T, Nagy P, Peter M, Szente L, Panyi G, Varga Z. Determining the target of membrane sterols on voltage-gated potassium channels. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:312-325. [PMID: 30553843 DOI: 10.1016/j.bbalip.2018.12.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/30/2018] [Accepted: 12/12/2018] [Indexed: 12/18/2022]
Abstract
Cholesterol, an essential lipid component of cellular plasma membranes, regulates fluidity, mechanical integrity, raft structure and may specifically interact with membrane proteins. Numerous effects on ion channels by cholesterol, including changes in current amplitude, voltage dependence and gating kinetics, have been reported. We have previously described such changes in the voltage-gated potassium channel Kv1.3 of lymphocytes by cholesterol and its analog 7-dehydrocholesterol (7DHC). In voltage-gated channels membrane depolarization induces movement of the voltage sensor domains (VSD), which is transmitted by a coupling mechanism to the pore domain (PD) to open the channel. Here, we investigated whether cholesterol effects were mediated by the VSD to the pore or the PD was the direct target. Specificity was tested by comparing Kv1.3 and Kv10.1 channels having different VSD-PD coupling mechanisms. Current recordings were performed with two-electrode voltage-clamp fluorometry, where movement of the VSDs was monitored by attaching fluorophores to external cysteine residues introduced in the channel sequence. Loading the membrane with cholesterol or 7DHC using methyl-β-cyclodextrin induced changes in the steady-state and kinetic parameters of the ionic currents while leaving fluorescence parameters mostly unaffected in both channels. Non-stationary noise analysis revealed that reduction of single channel conductance rather than that of open probability caused the observed current decrease. Furthermore, confocal laser scanning and stimulated emission depletion microscopy demonstrated significant changes in the distribution of these ion channels in response to sterol loading. Our results indicate that sterol-induced effects on ion channel gating directly target the pore and do not act via the VSD.
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Affiliation(s)
- Florina Zakany
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary
| | - Pal Pap
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary; MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary
| | - Ferenc Papp
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary; MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary
| | - Tamas Kovacs
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary
| | - Peter Nagy
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary
| | - Maria Peter
- Institute of Biochemistry, Biological Research Center of the Hungarian Academy of Sciences, Temesvari Krt. 62, Szeged H-6726, Hungary
| | - Lajos Szente
- CycloLab Cyclodextrin R & D Laboratory Ltd., Illatos u. 7, Budapest H-1097, Hungary
| | - Gyorgy Panyi
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary; MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary
| | - Zoltan Varga
- Division of Biophysics, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary; MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, Egyetem ter 1, Debrecen H-4032, Hungary.
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Harraz OF, Longden TA, Hill-Eubanks D, Nelson MT. PIP 2 depletion promotes TRPV4 channel activity in mouse brain capillary endothelial cells. eLife 2018; 7:38689. [PMID: 30084828 PMCID: PMC6117155 DOI: 10.7554/elife.38689] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Accepted: 08/06/2018] [Indexed: 01/08/2023] Open
Abstract
We recently reported that the inward-rectifier Kir2.1 channel in brain capillary endothelial cells (cECs) plays a major role in neurovascular coupling (NVC) by mediating a neuronal activity-dependent, propagating vasodilatory (hyperpolarizing) signal. We further demonstrated that Kir2.1 activity is suppressed by depletion of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2). Whether cECs express depolarizing channels that intersect with Kir2.1-mediated signaling remains unknown. Here, we report that Ca2+/Na+-permeable TRPV4 (transient receptor potential vanilloid 4) channels are expressed in cECs and are tonically inhibited by PIP2. We further demonstrate that depletion of PIP2 by agonists, including putative NVC mediators, that promote PIP2 hydrolysis by signaling through Gq-protein-coupled receptors (GqPCRs) caused simultaneous disinhibition of TRPV4 channels and suppression of Kir2.1 channels. These findings collectively support the concept that GqPCR activation functions as a molecular switch to favor capillary TRPV4 activity over Kir2.1 signaling, an observation with potentially profound significance for the control of cerebral blood flow. Capillaries form branching networks that surround all cells of the body. They allow oxygen and nutrient exchange between blood and tissue, but this is not their only role. Capillaries in the brain form a tight barrier that prevents components carried in the blood from easily reaching the brain compartment. They also detect the activity of neurons and trigger on-demand increases in blood flow to active regions of the brain. This role, revealed only recently, depends upon ion channels on the surface of the capillary cells. Active neurons release potassium ions, which open a type of ion channel called Kir2.1 that allows potassium inside the cell to flow out. This process is repeated in neighboring capillary cells until it reaches an upstream vessel, where it causes the vessel to relax and increase the blood flow. Kir2.1 channels sit astride the membranes of capillary cells, where they can interact with other membrane molecules. One such molecule, called PIP2, plays several roles in relaying signals from the outside to the inside of cells. It also physically interacts with channels in the membrane, including Kir2.1 channels. If PIP2 levels are low, Kir2.1 channel activity decreases. Here, Harraz et al. discovered that capillary cells contain another type of ion channel, called TRPV4, which is also regulated by PIP2. But unlike Kir2.1, its activity increases when PIP2 levels drop. Moreover, TRPV4 channels allow sodium and calcium ions to flow into the cell, which has an effect opposite to that of potassium flowing out of the cell. Capillary cells also have receptor proteins called GqPCRs that are activated by chemical signals released by active neurons in the brain. GqPCRs break down PIP2, so their activity turns Kir2.1 channels off and TRPV4 channels on. This resets the system so that it is ready to respond to new signals from active neurons. GqPCRs work as molecular switches to control the balance between Kir2.1 and TRPV4 channels and turn brain blood flow up and down. GqPCRs and ion channels that depend on PIP2 can also be found in other types of cells. These findings could reveal clues about how signals are switched on and off in different cells. Understanding the role of PIP2 in signaling could also unveil what happens when signaling go wrong.
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Affiliation(s)
- Osama F Harraz
- Department of Pharmacology, University of Vermont, Burlington, United States
| | - Thomas A Longden
- Department of Pharmacology, University of Vermont, Burlington, United States
| | - David Hill-Eubanks
- Department of Pharmacology, University of Vermont, Burlington, United States
| | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, United States.,Institute of Cardiovascular Sciences, Manchester, United Kingdom
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60
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Servin-Vences MR, Richardson J, Lewin GR, Poole K. Mechanoelectrical transduction in chondrocytes. Clin Exp Pharmacol Physiol 2018; 45:481-488. [PMID: 29359488 DOI: 10.1111/1440-1681.12917] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 12/20/2017] [Accepted: 01/09/2018] [Indexed: 11/29/2022]
Abstract
Cartilage tissue lines the joints of mammals, helping to lubricate joint movement and distribute mechanical loads. This tissue is comprised of isolated cells known as chondrocytes which are embedded in an extracellular matrix. Chondrocytes produce and maintain the cartilage by sensing and responding to changing mechanical loads. Mechanosensitive ion channels have been implicated in chondrocyte mechanotransduction and recent studies have shown that both PIEZO1 and TRPV4 can be activated by mechanical stimuli in these cells. The 2 channels mediate separate but overlapping mechanoelectrical transduction pathways, PIEZO1 in response to stretch and substrate deflections and TRPV4 in response to substrate deflections alone. These distinct pathways of mechanoelectrical transduction suggest a mechanism by which chondrocytes can distinguish between different stimuli that arise in their complex mechanical environment.
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Affiliation(s)
| | - Jessica Richardson
- School of Medical Sciences, EMBL Australia node for Single Molecule Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Gary R Lewin
- Max Delbruck Center for Molecular Medicine, Department Neuroscience, Berlin-Buch, Germany
| | - Kate Poole
- School of Medical Sciences, EMBL Australia node for Single Molecule Sciences, University of New South Wales, Sydney, NSW, Australia
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61
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Cao S, Anishkin A, Zinkevich NS, Nishijima Y, Korishettar A, Wang Z, Fang J, Wilcox DA, Zhang DX. Transient receptor potential vanilloid 4 (TRPV4) activation by arachidonic acid requires protein kinase A-mediated phosphorylation. J Biol Chem 2018; 293:5307-5322. [PMID: 29462784 DOI: 10.1074/jbc.m117.811075] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 01/24/2018] [Indexed: 11/06/2022] Open
Abstract
Transient receptor potential vanilloid 4 (TRPV4) is a Ca2+-permeable channel of the transient receptor potential (TRP) superfamily activated by diverse stimuli, including warm temperature, mechanical forces, and lipid mediators such as arachidonic acid (AA) and its metabolites. This activation is tightly regulated by protein phosphorylation carried out by various serine/threonine or tyrosine kinases. It remains poorly understood how phosphorylation differentially regulates TRPV4 activation in response to different stimuli. We investigated how TRPV4 activation by AA, an important signaling process in the dilation of coronary arterioles, is affected by protein kinase A (PKA)-mediated phosphorylation at Ser-824. Wildtype and mutant TRPV4 channels were expressed in human coronary artery endothelial cells (HCAECs). AA-induced TRPV4 activation was blunted in the S824A mutant but was enhanced in the phosphomimetic S824E mutant, whereas the channel activation by the synthetic agonist GSK1016790A was not affected. The low level of basal phosphorylation at Ser-824 was robustly increased by the redox signaling molecule hydrogen peroxide (H2O2). The H2O2-induced phosphorylation was accompanied by an enhanced channel activation by AA, and this enhanced response was largely abolished by PKA inhibition or S824A mutation. We further identified a potential structural context dependence of Ser-824 phosphorylation-mediated TRPV4 regulation involving an interplay between AA binding and the possible phosphorylation-induced rearrangements of the C-terminal helix bearing Ser-824. These results provide insight into how phosphorylation specifically regulates TRPV4 activation. Redox-mediated TRPV4 phosphorylation may contribute to pathologies associated with enhanced TRPV4 activity in endothelial and other systems.
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Affiliation(s)
- Sheng Cao
- From the Department of Medicine, Cardiovascular Center
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | - Natalya S Zinkevich
- From the Department of Medicine, Cardiovascular Center.,Department of Health and Medicine, Carroll University, Waukesha, Wisconsin 53186, and
| | | | | | - Zhihao Wang
- From the Department of Medicine, Cardiovascular Center
| | - Juan Fang
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.,Children's Research Institute, The Children's Hospital of Wisconsin, Milwaukee, Wisconsin 53226
| | - David A Wilcox
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.,Children's Research Institute, The Children's Hospital of Wisconsin, Milwaukee, Wisconsin 53226
| | - David X Zhang
- From the Department of Medicine, Cardiovascular Center,
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62
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Caires R, Sierra-Valdez FJ, Millet JR, Herwig JD, Roan E, Vásquez V, Cordero-Morales JF. Omega-3 Fatty Acids Modulate TRPV4 Function through Plasma Membrane Remodeling. Cell Rep 2017; 21:246-258. [DOI: 10.1016/j.celrep.2017.09.029] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 07/18/2017] [Accepted: 09/07/2017] [Indexed: 12/26/2022] Open
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63
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Structural determinants of 5',6'-epoxyeicosatrienoic acid binding to and activation of TRPV4 channel. Sci Rep 2017; 7:10522. [PMID: 28874838 PMCID: PMC5585255 DOI: 10.1038/s41598-017-11274-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 08/22/2017] [Indexed: 11/08/2022] Open
Abstract
TRPV4 cation channel activation by cytochrome P450-mediated derivatives of arachidonic acid (AA), epoxyeicosatrienoic acids (EETs), constitute a major mechanisms of endothelium-derived vasodilatation. Besides, TRPV4 mechano/osmosensitivity depends on phospholipase A2 (PLA2) activation and subsequent production of AA and EETs. However, the lack of evidence for a direct interaction of EETs with TRPV4 together with claims of EET-independent mechanical activation of TRPV4 has cast doubts on the validity of this mechanism. We now report: 1) The identification of an EET-binding pocket that specifically mediates TRPV4 activation by 5',6'-EET, AA and hypotonic cell swelling, thereby suggesting that all these stimuli shared a common structural target within the TRPV4 channel; and 2) A structural insight into the gating of TRPV4 by a natural agonist (5',6'-EET) in which K535 plays a crucial role, as mutant TRPV4-K535A losses binding of and gating by EET, without affecting GSK1016790A, 4α-phorbol 12,13-didecanoate and heat mediated channel activation. Together, our data demonstrates that the mechano- and osmotransducing messenger EET gates TRPV4 by a direct action on a site formed by residues from the S2-S3 linker, S4 and S4-S5 linker.
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Toft-Bertelsen TL, Križaj D, MacAulay N. When size matters: transient receptor potential vanilloid 4 channel as a volume-sensor rather than an osmo-sensor. J Physiol 2017; 595:3287-3302. [PMID: 28295351 DOI: 10.1113/jp274135] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/07/2017] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Mammalian cells are frequently exposed to stressors causing volume changes. The transient receptor potential vanilloid 4 (TRPV4) channel translates osmotic stress into ion flux. The molecular mechanism coupling osmolarity to TRPV4 activation remains elusive. TRPV4 responds to isosmolar cell swelling and osmolarity translated via different aquaporins. TRPV4 functions as a volume-sensing ion channel irrespective of the origin of the cell swelling. ABSTRACT Transient receptor potential channel 4 of the vanilloid subfamily (TRPV4) is activated by a diverse range of molecular cues, such as heat, lipid metabolites and synthetic agonists, in addition to hyposmotic challenges. As a non-selective cation channel permeable to Ca2+ , it transduces physical stress in the form of osmotic cell swelling into intracellular Ca2+ -dependent signalling events. Its contribution to cell volume regulation might include interactions with aquaporin (AQP) water channel isoforms, although the proposed requirement for a TRPV4-AQP4 macromolecular complex remains to be resolved. To characterize the elusive mechanics of TRPV4 volume-sensing, we expressed the channel in Xenopus laevis oocytes together with AQP4. Co-expression with AQP4 facilitated the cell swelling induced by osmotic challenges and thereby activated TRPV4-mediated transmembrane currents. Similar TRPV4 activation was induced by co-expression of a cognate channel, AQP1. The level of osmotically-induced TRPV4 activation, although proportional to the degree of cell swelling, was dependent on the rate of volume changes. Importantly, isosmotic cell swelling obtained by parallel activation of the co-expressed water-translocating Na+ /K+ /2Cl- cotransporter promoted TRPV4 activation despite the absence of the substantial osmotic gradients frequently employed for activation. Upon simultaneous application of an osmotic gradient and the selective TRPV4 agonist GSK1016790A, enhanced TRPV4 activation was observed only with subsaturating stimuli, indicating that the agonist promotes channel opening similar to that of volume-dependent activation. We propose that, contrary to the established paradigm, TRPV4 is activated by increased cell volume irrespective of the molecular mechanism underlying cell swelling. Thus, the channel functions as a volume-sensor, rather than as an osmo-sensor.
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Affiliation(s)
- Trine L Toft-Bertelsen
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - David Križaj
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Nanna MacAulay
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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White JPM, Cibelli M, Urban L, Nilius B, McGeown JG, Nagy I. TRPV4: Molecular Conductor of a Diverse Orchestra. Physiol Rev 2017; 96:911-73. [PMID: 27252279 DOI: 10.1152/physrev.00016.2015] [Citation(s) in RCA: 287] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Transient receptor potential vanilloid type 4 (TRPV4) is a calcium-permeable nonselective cation channel, originally described in 2000 by research teams led by Schultz (Nat Cell Biol 2: 695-702, 2000) and Liedtke (Cell 103: 525-535, 2000). TRPV4 is now recognized as being a polymodal ionotropic receptor that is activated by a disparate array of stimuli, ranging from hypotonicity to heat and acidic pH. Importantly, this ion channel is constitutively expressed and capable of spontaneous activity in the absence of agonist stimulation, which suggests that it serves important physiological functions, as does its widespread dissemination throughout the body and its capacity to interact with other proteins. Not surprisingly, therefore, it has emerged more recently that TRPV4 fulfills a great number of important physiological roles and that various disease states are attributable to the absence, or abnormal functioning, of this ion channel. Here, we review the known characteristics of this ion channel's structure, localization and function, including its activators, and examine its functional importance in health and disease.
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Affiliation(s)
- John P M White
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Mario Cibelli
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Laszlo Urban
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Bernd Nilius
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - J Graham McGeown
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Istvan Nagy
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
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Hofmann L, Wang H, Zheng W, Philipp SE, Hidalgo P, Cavalié A, Chen XZ, Beck A, Flockerzi V. The S4---S5 linker - gearbox of TRP channel gating. Cell Calcium 2017; 67:156-165. [PMID: 28416203 DOI: 10.1016/j.ceca.2017.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/03/2017] [Accepted: 04/03/2017] [Indexed: 10/19/2022]
Abstract
Transient receptor potential (TRP) channels are cation channels which participate in a wide variety of physiological processes in organisms ranging from fungi to humans. They fulfill roles in body homeostasis, are sensors for noxious chemicals and temperature in the mammalian somatosensory system and are activated by light stimulated phospholipase C activity in Drosophila or by hypertonicity in yeast. The transmembrane topology of TRP channels is similar to that of voltage-gated cation channels. TRP proteins assemble as tetramers with each subunit containing six transmembrane helices (S1-S6) and intracellular N- and C-termini. Here we focus on the emerging functions of the cytosolic S4-S5 linker on TRP channel gating. Most of this knowledge comes from pathogenic mutations within the S4-S5 linker that alter TRP channel activities. This knowledge has stimulated forward genetic approaches to identify additional residues around this region which are essential for channel gating and is supported, in part, by recent structures obtained for TRPV1, TRPV2, TRPV6, TRPA1, and TRPP2.
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Affiliation(s)
- Laura Hofmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Hongmei Wang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Wang Zheng
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, T6G 2H7, Edmonton, AB, Canada
| | - Stephan E Philipp
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Patricia Hidalgo
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Adolfo Cavalié
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Xing-Zhen Chen
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, T6G 2H7, Edmonton, AB, Canada
| | - Andreas Beck
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Veit Flockerzi
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany.
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TRPV4 Stimulation Induced Melatonin Secretion by Increasing Arylalkymine N-acetyltransferase (AANAT) Protein Level. Int J Mol Sci 2017; 18:ijms18040746. [PMID: 28368307 PMCID: PMC5412331 DOI: 10.3390/ijms18040746] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Revised: 03/21/2017] [Accepted: 03/27/2017] [Indexed: 01/19/2023] Open
Abstract
Melatonin is a molecule which has gained a great deal of interest in many areas of science; its synthesis was classically known to be in the pineal gland. However, many organs synthesize melatonin, such as several ocular structures. Melatonin is known to participate in many functions apart from its main action regulating the circadian rhythm. It is synthesized from serotonin in two steps, with a rate-limiting step carried out by arylalkymine N-acetyltransferase (AANAT). In this report, the role of TRPV4 channel present in human ciliary body epithelial cells in AANAT production was studied. Several experiments were undertaken to verify the adequate time to reach the maximal effect by using the TRPV4 agonist GSK1016790A, together with a dose-response study. An increase of 2.4 folds in AANAT was seen after 18 h of incubation with 10 nM of GSK1016790A (p < 0.001, n = 6). This increment was verified by antagonist assays. In summary, AANAT levels and therefore melatonin synthesis change after TRPV4 channel stimulation. Using this cell model together with human ciliary body tissue it is possible to suggest that AANAT plays an important role in pathologies related to intraocular pressure.
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Grace MS, Bonvini SJ, Belvisi MG, McIntyre P. Modulation of the TRPV4 ion channel as a therapeutic target for disease. Pharmacol Ther 2017; 177:9-22. [PMID: 28202366 DOI: 10.1016/j.pharmthera.2017.02.019] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Transient Receptor Potential Vanilloid 4 (TRPV4) is a broadly expressed, polymodally gated ion channel that plays an important role in many physiological and pathophysiological processes. TRPV4 knockout mice and several synthetic pharmacological compounds that selectively target TRPV4 are now available, which has allowed detailed investigation in to the therapeutic potential of this ion channel. Results from animal studies suggest that TRPV4 antagonism has therapeutic potential in oedema, pain, gastrointestinal disorders, and lung diseases such as cough, bronchoconstriction, pulmonary hypertension, and acute lung injury. A lack of observed side-effects in vivo has prompted a first-in-human trial for a TRPV4 antagonist in healthy participants and stable heart failure patients. If successful, this would open up an exciting new area of research for a multitude of TRPV4-related pathologies. This review will discuss the known roles of TRPV4 in disease, and highlight the possible implications of targeting this important cation channel for therapy.
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Affiliation(s)
- Megan S Grace
- Baker Heart and Diabetes Institute, Melbourne, Australia; School of Health and Biomedical Sciences, RMIT University, Bundoora, Melbourne, Australia; Department of Physiology, School of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Australia.
| | - Sara J Bonvini
- Respiratory Pharmacology, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, London, UK
| | - Maria G Belvisi
- Respiratory Pharmacology, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, London, UK
| | - Peter McIntyre
- School of Health and Biomedical Sciences, RMIT University, Bundoora, Melbourne, Australia
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69
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Servin-Vences MR, Moroni M, Lewin GR, Poole K. Direct measurement of TRPV4 and PIEZO1 activity reveals multiple mechanotransduction pathways in chondrocytes. eLife 2017; 6. [PMID: 28135189 PMCID: PMC5279942 DOI: 10.7554/elife.21074] [Citation(s) in RCA: 172] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 01/03/2017] [Indexed: 12/24/2022] Open
Abstract
The joints of mammals are lined with cartilage, comprised of individual chondrocytes embedded in a specialized extracellular matrix. Chondrocytes experience a complex mechanical environment and respond to changing mechanical loads in order to maintain cartilage homeostasis. It has been proposed that mechanically gated ion channels are of functional importance in chondrocyte mechanotransduction; however, direct evidence of mechanical current activation in these cells has been lacking. We have used high-speed pressure clamp and elastomeric pillar arrays to apply distinct mechanical stimuli to primary murine chondrocytes, stretch of the membrane and deflection of cell-substrate contacts points, respectively. Both TRPV4 and PIEZO1 channels contribute to currents activated by stimuli applied at cell-substrate contacts but only PIEZO1 mediates stretch-activated currents. These data demonstrate that there are separate, but overlapping, mechanoelectrical transduction pathways in chondrocytes.
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Affiliation(s)
| | - Mirko Moroni
- Department of Neuroscience, Max Delbruck Center for Molecular Medicine, Berlin, Germany
| | - Gary R Lewin
- Department of Neuroscience, Max Delbruck Center for Molecular Medicine, Berlin, Germany
| | - Kate Poole
- Department of Neuroscience, Max Delbruck Center for Molecular Medicine, Berlin, Germany.,Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, Australia.,EMBL Australia node for Single Molecule Sciences, School of Medical Sciences, University of New South Wales, Sydney, Australia
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70
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Åkerström B, Cederlund M, Bergwik J, Manouchehrian O, Arnér K, Taylor IH, Ghosh F, Taylor L. The Role of Mitochondria, Oxidative Stress, and the Radical-binding Protein A1M in Cultured Porcine Retina. Curr Eye Res 2017; 42:948-961. [PMID: 28118055 DOI: 10.1080/02713683.2016.1254247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PURPOSE The purpose of this study was to explore the relationship between oxidative stress, antioxidant defense, mitochondrial structure, and biomechanical tissue support in the isolated porcine retina. METHODS Full-thickness retinal sheets were isolated from adult porcine eyes. Retinas were cultured for 2 or 48 h using (1) a previously established low-support explant protocol with photoreceptors positioned against the culture membrane (porous polycarbonate) or (2) a high-support procedure developed by our group, apposing the Müller cell endfeet and inner limiting membrane against the membrane. The grafts were analyzed by quantitative polymerase chain reaction (PCR), immunohistochemistry, and transmission electron microscopy (TEM), and culture medium was assayed for the cell damage and oxidative stress markers lactate dehydrogenase and protein carbonyls. RESULTS In explants cultured with physical support to the inner border, cone photoreceptors were preserved and lactate dehydrogenase levels were reduced, although an initial (2 h), transient, increased oxidative stress was observed. Elevated expression of the antioxidants α1-microglobulin and heme oxygenase-1 was seen in the mitochondria-rich inner segments after 48 h compared to low-support counterparts. Housekeeping gene expression suggested a higher degree of structural integrity of mitochondria in high-support explants, and TEM of inner segments confirmed preservation of a normal mitochondrial morphology. CONCLUSION Providing retinal explants with inner retinal support leads to mobilization of antioxidant proteins, preservation of mitochondrial function, and increased cell viability. Consequently, the failure of low-support retinal cultures to mobilize an adequate response to the oxidative environment may play a key role in their rapid demise. These findings shed new light on pathological reactions in biomechanically related conditions in vivo.
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Affiliation(s)
- Bo Åkerström
- a Section for Infection Medicine, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Martin Cederlund
- a Section for Infection Medicine, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Jesper Bergwik
- a Section for Infection Medicine, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Oscar Manouchehrian
- b Section for Ophthalmology, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Karin Arnér
- b Section for Ophthalmology, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Ingrid Holmgren Taylor
- b Section for Ophthalmology, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Fredrik Ghosh
- b Section for Ophthalmology, Department of Clinical Sciences , Lund University , Lund , Sweden
| | - Linnéa Taylor
- b Section for Ophthalmology, Department of Clinical Sciences , Lund University , Lund , Sweden
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72
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Cox CD, Bavi N, Martinac B. Origin of the Force: The Force-From-Lipids Principle Applied to Piezo Channels. CURRENT TOPICS IN MEMBRANES 2016; 79:59-96. [PMID: 28728824 DOI: 10.1016/bs.ctm.2016.09.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Piezo channels are a ubiquitously expressed, principal type of molecular force sensor in eukaryotes. They enable cells to decode a myriad of physical stimuli and are essential components of numerous mechanosensory processes. Central to their physiological role is the ability to change conformation in response to mechanical force. Here we discuss the evolutionary origin of Piezo in relation to other MS channels in addition to the force that gates Piezo channels. In particular, we discuss whether Piezo channels are inherently mechanosensitive in accordance with the force-from-lipid paradigm which has been firmly established for bacterial MS channels and two-pore domain K+ (K2P) channels. We also discuss the evidence supporting a reliance on or direct interaction with structural scaffold proteins of the cytoskeleton and extracellular matrix according to the force-from-filament principle. In doing so, we explain the false dichotomy that these distinctions represent. We also discuss the possible unifying models that shed light on channel mechanosensitivity at the molecular level.
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Affiliation(s)
- C D Cox
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; University of New South Wales, Darlinghurst, NSW, Australia
| | - N Bavi
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; University of New South Wales, Darlinghurst, NSW, Australia
| | - B Martinac
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; University of New South Wales, Darlinghurst, NSW, Australia
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Teng J, Loukin SH, Anishkin A, Kung C. A competing hydrophobic tug on L596 to the membrane core unlatches S4-S5 linker elbow from TRP helix and allows TRPV4 channel to open. Proc Natl Acad Sci U S A 2016; 113:11847-11852. [PMID: 27698146 PMCID: PMC5081603 DOI: 10.1073/pnas.1613523113] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have some generalized physical understanding of how ion channels interact with surrounding lipids but few detailed descriptions on how interactions of particular amino acids with contacting lipids may regulate gating. Here we discovered a structure-specific interaction between an amino acid and inner-leaflet lipid that governs the gating transformations of TRPV4 (transient receptor potential vanilloid type 4). Many cation channels use a S4-S5 linker to transmit stimuli to the gate. At the start of TRPV4's linker helix is leucine 596. A hydrogen bond between the indole of W733 of the TRP helix and the backbone oxygen of L596 secures the helix/linker contact, which acts as a latch maintaining channel closure. The modeled side chain of L596 interacts with the inner lipid leaflet near the polar-nonpolar interface in our model-an interaction that we explored by mutagenesis. We examined the outward currents of TRPV4-expressing Xenopus oocyte upon depolarizations as well as phenotypes of expressing yeast cells. Making this residue less hydrophobic (L596A/G/W/Q/K) reduces open probability [Po; loss-of-function (LOF)], likely due to altered interactions at the polar-nonpolar interface. L596I raises Po [gain-of-function (GOF)], apparently by placing its methyl group further inward and receiving stronger water repulsion. Molecular dynamics simulations showed that the distance between the levels of α-carbons of H-bonded residues L596 and W733 is shortened in the LOFs and lengthened in the GOFs, strengthening or weakening the linker/TRP helix latch, respectively. These results highlight that L596 lipid attraction counteracts the latch bond in a tug-of-war to tune the Po of TRPV4.
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Affiliation(s)
- Jinfeng Teng
- Laboratory of Molecular and Cell Biology, University of Wisconsin, Madison, WI 53706; Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Stephen H Loukin
- Laboratory of Molecular and Cell Biology, University of Wisconsin, Madison, WI 53706
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Ching Kung
- Laboratory of Molecular and Cell Biology, University of Wisconsin, Madison, WI 53706; Department of Genetics, University of Wisconsin, Madison, WI 53706
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Ryskamp DA, Frye AM, Phuong TTT, Yarishkin O, Jo AO, Xu Y, Lakk M, Iuso A, Redmon SN, Ambati B, Hageman G, Prestwich GD, Torrejon KY, Križaj D. TRPV4 regulates calcium homeostasis, cytoskeletal remodeling, conventional outflow and intraocular pressure in the mammalian eye. Sci Rep 2016; 6:30583. [PMID: 27510430 PMCID: PMC4980693 DOI: 10.1038/srep30583] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/04/2016] [Indexed: 01/20/2023] Open
Abstract
An intractable challenge in glaucoma treatment has been to identify druggable targets within the conventional aqueous humor outflow pathway, which is thought to be regulated/dysregulated by elusive mechanosensitive protein(s). Here, biochemical and functional analyses localized the putative mechanosensitive cation channel TRPV4 to the plasma membrane of primary and immortalized human TM (hTM) cells, and to human and mouse TM tissue. Selective TRPV4 agonists and substrate stretch evoked TRPV4-dependent cation/Ca2+ influx, thickening of F-actin stress fibers and reinforcement of focal adhesion contacts. TRPV4 inhibition enhanced the outflow facility and lowered perfusate pressure in biomimetic TM scaffolds populated with primary hTM cells. Systemic delivery, intraocular injection or topical application of putative TRPV4 antagonist prodrug analogs lowered IOP in glaucomatous mouse eyes and protected retinal neurons from IOP-induced death. Together, these findings indicate that TRPV4 channels function as a critical component of mechanosensitive, Ca2+-signaling machinery within the TM, and that TRPV4-dependent cytoskeletal remodeling regulates TM stiffness and outflow. Thus, TRPV4 is a potential IOP sensor within the conventional outflow pathway and a novel target for treating ocular hypertension.
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Affiliation(s)
- Daniel A Ryskamp
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Amber M Frye
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Tam T T Phuong
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Oleg Yarishkin
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Andrew O Jo
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Yong Xu
- Department of Medicinal Chemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Monika Lakk
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Anthony Iuso
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Sarah N Redmon
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Balamurali Ambati
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Gregory Hageman
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Center for Translational Medicine, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Glenn D Prestwich
- Department of Medicinal Chemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | | | - David Križaj
- Department of Ophthalmology &Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Center for Translational Medicine, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Department of Neurobiology &Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.,Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA
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Lau OC, Shen B, Wong CO, Tjong YW, Lo CY, Wang HC, Huang Y, Yung WH, Chen YC, Fung ML, Rudd JA, Yao X. TRPC5 channels participate in pressure-sensing in aortic baroreceptors. Nat Commun 2016; 7:11947. [PMID: 27411851 PMCID: PMC4947175 DOI: 10.1038/ncomms11947] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/13/2016] [Indexed: 11/25/2022] Open
Abstract
Blood pressure is maintained within a normal physiological range by a sophisticated regulatory mechanism. Baroreceptors serve as a frontline sensor to detect the change in blood pressure. Nerve signals are then sent to the cardiovascular control centre in the brain in order to stimulate baroreflex responses. Here, we identify TRPC5 channels as a mechanical sensor in aortic baroreceptors. In Trpc5 knockout mice, the pressure-induced action potential firings in the afferent nerve and the baroreflex-mediated heart rate reduction are attenuated. Telemetric measurements of blood pressure demonstrate that Trpc5 knockout mice display severe daily blood pressure fluctuation. Our results suggest that TRPC5 channels represent a key pressure transducer in the baroreceptors and play an important role in maintaining blood pressure stability. Because baroreceptor dysfunction contributes to a variety of cardiovascular diseases including hypertension, heart failure and myocardial infarction, our findings may have important future clinical implications. The identity of mechanosensors within aortic baroreceptors that sense fluctuations in blood pressure is unclear. Here, Lau et al. show that a cation channel TRPC5 acts as a transducer of mechanical stimuli in aortic baroreceptor neurons in rodents.
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Affiliation(s)
- On-Chai Lau
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Bing Shen
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,Department of Physiology, Anhui Medical University, Hefei 230032, China
| | - Ching-On Wong
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yung-Wui Tjong
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Chun-Yin Lo
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Hui-Chuan Wang
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yu Huang
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing-Ho Yung
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yang-Chao Chen
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Man-Lung Fung
- Department of Physiology, University of Hong Kong, Hong Kong, China
| | - John Anthony Rudd
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Xiaoqiang Yao
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
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76
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Mah W, Sonkusare SK, Wang T, Azeddine B, Pupavac M, Carrot-Zhang J, Hong K, Majewski J, Harvey EJ, Russell L, Chalk C, Rosenblatt DS, Nelson MT, Séguin C. Gain-of-function mutation in TRPV4 identified in patients with osteonecrosis of the femoral head. J Med Genet 2016; 53:705-9. [PMID: 27330106 PMCID: PMC5035228 DOI: 10.1136/jmedgenet-2016-103829] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 05/25/2016] [Indexed: 12/11/2022]
Abstract
Background Osteonecrosis of the femoral head is a debilitating disease that involves impaired blood supply to the femoral head and leads to femoral head collapse. Methods We use whole-exome sequencing and Sanger sequencing to analyse a family with inherited osteonecrosis of the femoral head and fluorescent Ca2+ imaging to functionally characterise the variant protein. Results We report a family with four siblings affected with inherited osteonecrosis of the femoral head and the identification of a c.2480_2483delCCCG frameshift deletion followed by a c.2486T>A substitution in one allele of the transient receptor potential vanilloid 4 (TRPV4) gene. TRPV4 encodes a Ca2+-permeable cation channel known to play a role in vasoregulation and osteoclast differentiation. While pathogenic TRPV4 mutations affect the skeletal or nervous systems, association with osteonecrosis of the femoral head is novel. Functional measurements of Ca2+ influx through mutant TRPV4 channels in HEK293 cells and patient-derived dermal fibroblasts identified a TRPV4 gain of function. Analysis of channel open times, determined indirectly from measurement of TRPV4 activity within a cluster of TRPV4 channels, revealed that the TRPV4 gain of function was caused by longer channel openings. Conclusions These findings identify a novel TRPV4 mutation implicating TRPV4 and altered calcium homeostasis in the pathogenesis of osteonecrosis while reinforcing the importance of TRPV4 in bone diseases and vascular endothelium.
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Affiliation(s)
- Wayne Mah
- Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Swapnil K Sonkusare
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Tracy Wang
- Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Bouziane Azeddine
- Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Mihaela Pupavac
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Jian Carrot-Zhang
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada Department of Human Genetics, McGill University and Genome Québec Innovation Centre, Montreal, Quebec, Canada
| | - Kwangseok Hong
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Jacek Majewski
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada Department of Human Genetics, McGill University and Genome Québec Innovation Centre, Montreal, Quebec, Canada
| | - Edward J Harvey
- Department of Surgery, Division of Orthopaedic Surgery, McGill University Health Centre, Montreal, Quebec, Canada
| | - Laura Russell
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Colin Chalk
- Department of Neurology & Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - David S Rosenblatt
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Chantal Séguin
- Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
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77
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Stochastic model of endothelial TRPV4 calcium sparklets: effect of bursting and cooperativity on EDH. Biophys J 2016; 108:1566-1576. [PMID: 25809269 DOI: 10.1016/j.bpj.2015.01.034] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/15/2015] [Accepted: 01/27/2015] [Indexed: 01/28/2023] Open
Abstract
We examined the endothelial transient receptor vanilloid 4 (TRPV4) channel's vasodilatory signaling using mathematical modeling. The model analyzes experimental data by Sonkusare and coworkers on TRPV4-induced endothelial Ca(2+) events (sparklets). A previously developed continuum model of an endothelial and a smooth muscle cell coupled through microprojections was extended to account for the activity of a TRPV4 channel cluster. Different stochastic descriptions for the TRPV4 channel flux were examined using finite-state Markov chains. The model also took into consideration recent evidence for the colocalization of intermediate-conductance calcium-activated potassium channels (IKCa) and TRPV4 channels near the microprojections. A single TRPV4 channel opening resulted in a stochastic localized Ca(2+) increase in a small region (i.e., few μm(2) area) close to the channel. We predict micromolar Ca(2+) increases lasting for the open duration of the channel sufficient for the activation of low-affinity endothelial KCa channels. Simulations of a cluster of four TRPV4 channels incorporating burst and cooperative gating kinetics provided quantal Ca(2+) increases (i.e., steps of fixed amplitude), similar to the experimentally observed Ca(2+) sparklets. These localized Ca(2+) events result in endothelium-derived hyperpolarization (and SMC relaxation), with magnitude that depends on event frequency. The gating characteristics (bursting, cooperativity) of the TRPV4 cluster enhance Ca(2+) spread and the distance of KCa channel activation. This may amplify the EDH response by the additional recruitment of distant KCa channels.
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78
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Wheeler MA, Smith CJ, Ottolini M, Barker BS, Purohit AM, Grippo RM, Gaykema RP, Spano AJ, Beenhakker MP, Kucenas S, Patel MK, Deppmann CD, Güler AD. Genetically targeted magnetic control of the nervous system. Nat Neurosci 2016; 19:756-761. [PMID: 26950006 PMCID: PMC4846560 DOI: 10.1038/nn.4265] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 02/09/2016] [Indexed: 12/14/2022]
Abstract
Optogenetic and chemogenetic actuators are critical for deconstructing the neural correlates of behavior. However, these tools have several limitations, including invasive modes of stimulation or slow on/off kinetics. We have overcome these disadvantages by synthesizing a single-component, magnetically sensitive actuator, "Magneto," comprising the cation channel TRPV4 fused to the paramagnetic protein ferritin. We validated noninvasive magnetic control over neuronal activity by demonstrating remote stimulation of cells using in vitro calcium imaging assays, electrophysiological recordings in brain slices, in vivo electrophysiological recordings in the brains of freely moving mice, and behavioral outputs in zebrafish and mice. As proof of concept, we used Magneto to delineate a causal role of striatal dopamine receptor 1 neurons in mediating reward behavior in mice. Together our results present Magneto as an actuator capable of remotely controlling circuits associated with complex animal behaviors.
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Affiliation(s)
- Michael A. Wheeler
- Department of Biology, University of Virginia, Charlottesville, VA 22903
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA 22903
| | - Cody J. Smith
- Department of Biology, University of Virginia, Charlottesville, VA 22903
| | - Matteo Ottolini
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22903
| | - Bryan S. Barker
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA 22903
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22903
| | - Aarti M. Purohit
- Department of Biology, University of Virginia, Charlottesville, VA 22903
| | - Ryan M. Grippo
- Department of Biology, University of Virginia, Charlottesville, VA 22903
| | - Ronald P. Gaykema
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22903
| | - Anthony J. Spano
- Department of Biology, University of Virginia, Charlottesville, VA 22903
| | - Mark P. Beenhakker
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22903
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, VA 22903
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22903
| | - Manoj K. Patel
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22903
| | - Christopher D. Deppmann
- Department of Biology, University of Virginia, Charlottesville, VA 22903
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22903
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22903
| | - Ali D. Güler
- Department of Biology, University of Virginia, Charlottesville, VA 22903
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79
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Differential volume regulation and calcium signaling in two ciliary body cell types is subserved by TRPV4 channels. Proc Natl Acad Sci U S A 2016; 113:3885-90. [PMID: 27006502 DOI: 10.1073/pnas.1515895113] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Fluid secretion by the ciliary body plays a critical and irreplaceable function in vertebrate vision by providing nutritive support to the cornea and lens, and by maintaining intraocular pressure. Here, we identify TRPV4 (transient receptor potential vanilloid isoform 4) channels as key osmosensors in nonpigmented epithelial (NPE) cells of the mouse ciliary body. Hypotonic swelling and the selective agonist GSK1016790A (EC50 ∼33 nM) induced sustained transmembrane cation currents and cytosolic [Formula: see text] elevations in dissociated and intact NPE cells. Swelling had no effect on [Formula: see text] levels in pigment epithelial (PE) cells, whereas depolarization evoked [Formula: see text] elevations in both NPE and PE cells. Swelling-evoked [Formula: see text] signals were inhibited by the TRPV4 antagonist HC067047 (IC50 ∼0.9 μM) and were absent in Trpv4(-/-) NPE. In NPE, but not PE, swelling-induced [Formula: see text] signals required phospholipase A2 activation. TRPV4 localization to NPE was confirmed with immunolocalization and excitation mapping approaches, whereas in vivo MRI analysis confirmed TRPV4-mediated signals in the intact mouse ciliary body. Trpv2 and Trpv4 were the most abundant vanilloid transcripts in CB. Overall, our results support a model whereby TRPV4 differentially regulates cell volume, lipid, and calcium signals in NPE and PE cell types and therefore represents a potential target for antiglaucoma medications.
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80
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Karlin A. Membrane potential and Ca2+ concentration dependence on pressure and vasoactive agents in arterial smooth muscle: A model. ACTA ACUST UNITED AC 2016; 146:79-96. [PMID: 26123196 PMCID: PMC4485026 DOI: 10.1085/jgp.201511380] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A mathematical model incorporating junctional and stretch-activated microdomains and 37 protein components describes the myogenic response in arterial smooth muscle cells. Arterial smooth muscle (SM) cells respond autonomously to changes in intravascular pressure, adjusting tension to maintain vessel diameter. The values of membrane potential (Vm) and sarcoplasmic Ca2+ concentration (Cain) within minutes of a change in pressure are the results of two opposing pathways, both of which use Ca2+ as a signal. This works because the two Ca2+-signaling pathways are confined to distinct microdomains in which the Ca2+ concentrations needed to activate key channels are transiently higher than Cain. A mathematical model of an isolated arterial SM cell is presented that incorporates the two types of microdomains. The first type consists of junctions between cisternae of the peripheral sarcoplasmic reticulum (SR), containing ryanodine receptors (RyRs), and the sarcolemma, containing voltage- and Ca2+-activated K+ (BK) channels. These junctional microdomains promote hyperpolarization, reduced Cain, and relaxation. The second type is postulated to form around stretch-activated nonspecific cation channels and neighboring Ca2+-activated Cl− channels, and promotes the opposite (depolarization, increased Cain, and contraction). The model includes three additional compartments: the sarcoplasm, the central SR lumen, and the peripheral SR lumen. It incorporates 37 protein components. In addition to pressure, the model accommodates inputs of α- and β-adrenergic agonists, ATP, 11,12-epoxyeicosatrienoic acid, and nitric oxide (NO). The parameters of the equations were adjusted to obtain a close fit to reported Vm and Cain as functions of pressure, which have been determined in cerebral arteries. The simulations were insensitive to ±10% changes in most of the parameters. The model also simulated the effects of inhibiting RyR, BK, or voltage-activated Ca2+ channels on Vm and Cain. Deletion of BK β1 subunits is known to increase arterial–SM tension. In the model, deletion of β1 raised Cain at all pressures, and these increases were reversed by NO.
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Affiliation(s)
- Arthur Karlin
- Department of Biochemistry and Molecular Biophysics, Department of Physiology and Cellular Biophysics, and Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY 10032
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81
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Križaj D. Polymodal Sensory Integration in Retinal Ganglion Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 854:693-8. [PMID: 26427477 PMCID: PMC5111544 DOI: 10.1007/978-3-319-17121-0_92] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
An animal's ability to perceive the external world is conditioned by its capacity to extract and encode specific features of the visual image. The output of the vertebrate retina is not a simple representation of the 2D visual map generated by photon absorptions in the photoreceptor layer. Rather, spatial, temporal, direction selectivity and color "dimensions" of the original image are distributed in the form of parallel output channels mediated by distinct retinal ganglion cell (RGC) populations. We propose that visual information transmitted to the brain includes additional, light-independent, inputs that reflect the functional states of the retina, anterior eye and the body. These may include the local ion microenvironment, glial metabolism and systemic parameters such as intraocular pressure, temperature and immune activation which act on ion channels that are intrinsic to RGCs. We particularly focus on light-independent mechanical inputs that are associated with physical impact, cell swelling and intraocular pressure as excessive mechanical stimuli lead to the counterintuitive experience of "pressure phosphenes" and/or debilitating blinding disease such as glaucoma and diabetic retinopathy. We point at recently discovered retinal mechanosensitive ion channels as examples through which molecular physiology brings together Greek phenomenology, modern neuroscience and medicine. Thus, RGC output represents a unified picture of the embodied context within which vision takes place.
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Affiliation(s)
- David Križaj
- Departments of Ophthalmology & Visual Sciences, John A. Moran Eye Institute and Neurobiology & Anatomy, Univ. of Utah School of Medicine, 84132, Salt Lake City, UT, USA.
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82
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Abstract
Mechanotransduction, the conversion of physical forces into biochemical signals, is essential for various physiological processes such as the conscious sensations of touch and hearing, and the unconscious sensation of blood flow. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels.
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Affiliation(s)
- Sanjeev S Ranade
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Ruhma Syeda
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Ardem Patapoutian
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA.
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83
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Galindo-Villegas J, Montalban-Arques A, Liarte S, de Oliveira S, Pardo-Pastor C, Rubio-Moscardo F, Meseguer J, Valverde MA, Mulero V. TRPV4-Mediated Detection of Hyposmotic Stress by Skin Keratinocytes Activates Developmental Immunity. THE JOURNAL OF IMMUNOLOGY 2015; 196:738-49. [PMID: 26673139 DOI: 10.4049/jimmunol.1501729] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 11/11/2015] [Indexed: 11/19/2022]
Abstract
As an organism is exposed to pathogens during very early development, specific defense mechanisms must take effect. In this study, we used a germ-free zebrafish embryo model to show that osmotic stress regulates the activation of immunity and host protection in newly hatched embryos. Mechanistically, skin keratinocytes were responsible for both sensing the hyposmolarity of the aquatic environment and mediating immune effector mechanisms. This occurred through a transient potential receptor vanilloid 4/Ca(2+)/TGF-β-activated kinase 1/NF-κB signaling pathway. Surprisingly, the genes encoding antimicrobial effectors, which do not have the potential to cause tissue damage, are constitutively expressed during development, independently of both commensal microbes and osmotic stress. Our results reveal that osmotic stress is associated with the induction of developmental immunity in the absence of tissue damage and point out to the embryo skin as the first organ with full capacities to mount an innate immune response.
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Affiliation(s)
- Jorge Galindo-Villegas
- Department of Cell Biology and Histology, Faculty of Biology, Institute of Biomedical Research of Murcia-Arrixaca, Espinardo Campus, University of Murcia, 30100 Murcia, Spain; and
| | - Ana Montalban-Arques
- Department of Cell Biology and Histology, Faculty of Biology, Institute of Biomedical Research of Murcia-Arrixaca, Espinardo Campus, University of Murcia, 30100 Murcia, Spain; and
| | - Sergio Liarte
- Department of Cell Biology and Histology, Faculty of Biology, Institute of Biomedical Research of Murcia-Arrixaca, Espinardo Campus, University of Murcia, 30100 Murcia, Spain; and
| | - Sofia de Oliveira
- Department of Cell Biology and Histology, Faculty of Biology, Institute of Biomedical Research of Murcia-Arrixaca, Espinardo Campus, University of Murcia, 30100 Murcia, Spain; and
| | - Carlos Pardo-Pastor
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Pompeu Fabra University, 08002 Barcelona, Spain
| | - Fanny Rubio-Moscardo
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Pompeu Fabra University, 08002 Barcelona, Spain
| | - José Meseguer
- Department of Cell Biology and Histology, Faculty of Biology, Institute of Biomedical Research of Murcia-Arrixaca, Espinardo Campus, University of Murcia, 30100 Murcia, Spain; and
| | - Miguel A Valverde
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Pompeu Fabra University, 08002 Barcelona, Spain
| | - Victoriano Mulero
- Department of Cell Biology and Histology, Faculty of Biology, Institute of Biomedical Research of Murcia-Arrixaca, Espinardo Campus, University of Murcia, 30100 Murcia, Spain; and
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84
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Wilson C, Saunter CD, Girkin JM, McCarron JG. Pressure-dependent regulation of Ca2+ signalling in the vascular endothelium. J Physiol 2015; 593:5231-53. [PMID: 26507455 PMCID: PMC4704526 DOI: 10.1113/jp271157] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 10/19/2015] [Indexed: 12/19/2022] Open
Abstract
Key points Increased pressure suppresses endothelial control of vascular tone but it remains uncertain (1) how pressure is sensed by the endothelium and (2) how the vascular response is inhibited. This study used a novel imaging method to study large numbers of endothelial cells in arteries that were in a physiological configuration and held at normal blood pressures. Increased pressure suppressed endothelial IP3‐mediated Ca2+ signals. Pressure modulated endothelial cell shape. The changes in cell shape may alter endothelial Ca2+ signals by modulating the diffusive environment for Ca2+ near IP3 receptors. Endothelial pressure‐dependent mechanosensing may occur without a requirement for a conventional molecular mechanoreceptor.
Abstract The endothelium is an interconnected network upon which haemodynamic mechanical forces act to control vascular tone and remodelling in disease. Ca2+ signalling is central to the endothelium's mechanotransduction and networked activity. However, challenges in imaging Ca2+ in large numbers of endothelial cells under conditions that preserve the intact physical configuration of pressurized arteries have limited progress in understanding how pressure‐dependent mechanical forces alter networked Ca2+ signalling. We developed a miniature wide‐field, gradient‐index (GRIN) optical probe designed to fit inside an intact pressurized artery that permitted Ca2+ signals to be imaged with subcellular resolution in a large number (∼200) of naturally connected endothelial cells at various pressures. Chemical (acetylcholine) activation triggered spatiotemporally complex, propagating inositol trisphosphate (IP3)‐mediated Ca2+ waves that originated in clusters of cells and progressed from there across the endothelium. Mechanical stimulation of the artery, by increased intraluminal pressure, flattened the endothelial cells and suppressed IP3‐mediated Ca2+ signals in all activated cells. By computationally modelling Ca2+ release, endothelial shape changes were shown to alter the geometry of the Ca2+ diffusive environment near IP3 receptor microdomains to limit IP3‐mediated Ca2+ signals as pressure increased. Changes in cell shape produce a geometric microdomain regulation of IP3‐mediated Ca2+ signalling to explain macroscopic pressure‐dependent, endothelial mechanosensing without the need for a conventional mechanoreceptor. The suppression of IP3‐mediated Ca2+ signalling may explain the decrease in endothelial activity as pressure increases. GRIN imaging provides a convenient method that gives access to hundreds of endothelial cells in intact arteries in physiological configuration. Increased pressure suppresses endothelial control of vascular tone but it remains uncertain (1) how pressure is sensed by the endothelium and (2) how the vascular response is inhibited. This study used a novel imaging method to study large numbers of endothelial cells in arteries that were in a physiological configuration and held at normal blood pressures. Increased pressure suppressed endothelial IP3‐mediated Ca2+ signals. Pressure modulated endothelial cell shape. The changes in cell shape may alter endothelial Ca2+ signals by modulating the diffusive environment for Ca2+ near IP3 receptors. Endothelial pressure‐dependent mechanosensing may occur without a requirement for a conventional molecular mechanoreceptor.
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Affiliation(s)
- Calum Wilson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, SIPBS Building, 161 Cathedral Street, Glasgow, G4 0RE, UK
| | - Christopher D Saunter
- Centre for Advanced Instrumentation, Biophysical Sciences Institute, Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
| | - John M Girkin
- Centre for Advanced Instrumentation, Biophysical Sciences Institute, Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
| | - John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, SIPBS Building, 161 Cathedral Street, Glasgow, G4 0RE, UK
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85
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Qi Y, Li Z, Kong CW, Tang NL, Huang Y, Li RA, Yao X. Uniaxial cyclic stretch stimulates TRPV4 to induce realignment of human embryonic stem cell-derived cardiomyocytes. J Mol Cell Cardiol 2015; 87:65-73. [DOI: 10.1016/j.yjmcc.2015.08.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 08/01/2015] [Accepted: 08/06/2015] [Indexed: 12/28/2022]
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86
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Jo AO, Ryskamp DA, Phuong TTT, Verkman AS, Yarishkin O, MacAulay N, Križaj D. TRPV4 and AQP4 Channels Synergistically Regulate Cell Volume and Calcium Homeostasis in Retinal Müller Glia. J Neurosci 2015; 35:13525-37. [PMID: 26424896 PMCID: PMC4588615 DOI: 10.1523/jneurosci.1987-15.2015] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 08/26/2015] [Accepted: 08/27/2015] [Indexed: 11/21/2022] Open
Abstract
Brain edema formation occurs after dysfunctional control of extracellular volume partly through impaired astrocytic ion and water transport. Here, we show that such processes might involve synergistic cooperation between the glial water channel aquaporin 4 (AQP4) and the transient receptor potential isoform 4 (TRPV4), a polymodal swelling-sensitive cation channel. In mouse retinas, TRPV4 colocalized with AQP4 in the end feet and radial processes of Müller astroglia. Genetic ablation of TRPV4 did not affect the distribution of AQP4 and vice versa. However, retinas from Trpv4(-/-) and Aqp4(-/-) mice exhibited suppressed transcription of genes encoding Trpv4, Aqp4, and the Kir4.1 subunit of inwardly rectifying potassium channels. Swelling and [Ca(2+)]i elevations evoked in Müller cells by hypotonic stimulation were antagonized by the selective TRPV4 antagonist HC-067047 (2-methyl-1-[3-(4-morpholinyl)propyl]-5-phenyl-N-[3-(trifluoromethyl)phenyl]-1H-pyrrole-3-carboxamide) or Trpv4 ablation. Elimination of Aqp4 suppressed swelling-induced [Ca(2+)]i elevations but only modestly attenuated the amplitude of Ca(2+) signals evoked by the TRPV4 agonist GSK1016790A [(N-((1S)-1-{[4-((2S)-2-{[(2,4-dichlorophenyl)sulfonyl]amino}-3-hydroxypropanoyl)-1-piperazinyl]carbonyl}-3-methylbutyl)-1-benzothiophene-2-carboxamide]. Glial cells lacking TRPV4 but not AQP4 showed deficits in hypotonic swelling and regulatory volume decrease. Functional synergy between TRPV4 and AQP4 during cell swelling was confirmed in the heterologously expressing Xenopus oocyte model. Importantly, when the swelling rate was osmotically matched for AQP4-positive and AQP4-negative oocytes, TRPV4 activation became independent of AQP4. We conclude that AQP4-mediated water fluxes promote the activation of the swelling sensor, whereas Ca(2+) entry through TRPV4 channels reciprocally modulates volume regulation, swelling, and Aqp4 gene expression. Therefore, TRPV4-AQP4 interactions constitute a molecular system that fine-tunes astroglial volume regulation by integrating osmosensing, calcium signaling, and water transport and, when overactivated, triggers pathological swelling. Significance statement: We characterize the physiological features of interactions between the astroglial swelling sensor transient receptor potential isoform 4 (TRPV4) and the aquaporin 4 (AQP4) water channel in retinal Müller cells. Our data reveal an elegant and complex set of mechanisms involving reciprocal interactions at the level of glial gene expression, calcium homeostasis, swelling, and volume regulation. Specifically, water influx through AQP4 drives calcium influx via TRPV4 in the glial end foot, which regulates expression of Aqp4 and Kir4.1 genes and facilitates the time course and amplitude of hypotonicity-induced swelling and regulatory volume decrease. We confirm the crucial facets of the signaling mechanism in heterologously expressing oocytes. These results identify the molecular mechanism that contributes to dynamic regulation of glial volume but also provide new insights into the pathophysiology of glial reactivity and edema formation.
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Affiliation(s)
- Andrew O Jo
- Department of Ophthalmology and Visual Sciences, Moran Eye Institute
| | - Daniel A Ryskamp
- Department of Ophthalmology and Visual Sciences, Moran Eye Institute, Interdepartmental Program in Neuroscience, and
| | - Tam T T Phuong
- Department of Ophthalmology and Visual Sciences, Moran Eye Institute
| | - Alan S Verkman
- Department of Medicine, University of California San Francisco, San Francisco, California 94143, and
| | - Oleg Yarishkin
- Department of Ophthalmology and Visual Sciences, Moran Eye Institute
| | - Nanna MacAulay
- Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - David Križaj
- Department of Ophthalmology and Visual Sciences, Moran Eye Institute, Interdepartmental Program in Neuroscience, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132,
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87
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Loukin SH, Teng J, Kung C. A channelopathy mechanism revealed by direct calmodulin activation of TrpV4. Proc Natl Acad Sci U S A 2015; 112:9400-5. [PMID: 26170305 PMCID: PMC4522800 DOI: 10.1073/pnas.1510602112] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ca(2+)-calmodulin (CaM) regulates varieties of ion channels, including Transient Receptor Potential vanilloid subtype 4 (TrpV4). It has previously been proposed that internal Ca(2+) increases TrpV4 activity through Ca(2+)-CaM binding to a C-terminal Ca(2+)-CaM binding domain (CBD). We confirmed this model by directly presenting Ca(2+)-CaM protein to membrane patches excised from TrpV4-expressing oocytes. Over 50 TRPV4 mutations are now known to cause heritable skeletal dysplasia (SD) and other diseases in human. We have previously examined 14 SD alleles and found them to all have gain-of-function effects, with the gain of constitutive open probability paralleling disease severity. Among the 14 SD alleles examined, E797K and P799L are located immediate upstream of the CBD. They not only have increase basal activity, but, unlike the wild-type or other SD-mutant channels examined, they were greatly reduced in their response to Ca(2+)-CaM. Deleting a 10-residue upstream peptide (Δ795-804) that covers the two SD mutant sites resulted in strong constitutive activity and the complete lack of Ca(2+)-CaM response. We propose that the region immediately upstream of CBD is an autoinhibitory domain that maintains the closed state through electrostatic interactions, and adjacent detachable Ca(2+)-CaM binding to CBD sterically interferes with this autoinhibition. This work further supports the notion that TrpV4 mutations cause SD by constitutive leakage. However, the closed conformation is likely destabilized by various mutations by different mechanisms, including the permanent removal of an autoinhibition documented here.
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Affiliation(s)
- Stephen H Loukin
- Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706;
| | - Jinfeng Teng
- Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706
| | - Ching Kung
- Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706; Department of Genetics, University of Wisconsin, Madison, WI 53706
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88
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Mueller-Tribbensee SM, Karna M, Khalil M, Neurath MF, Reeh PW, Engel MA. Differential Contribution of TRPA1, TRPV4 and TRPM8 to Colonic Nociception in Mice. PLoS One 2015. [PMID: 26207981 PMCID: PMC4514604 DOI: 10.1371/journal.pone.0128242] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Background Various transient receptor potential (TRP) channels in sensory neurons contribute to the transduction of mechanical stimuli in the colon. Recently, even the cold-sensing menthol receptor TRPM(melastatin)8 was suggested to be involved in murine colonic mechano-nociception. Methods To analyze the roles of TRPM8, TRPA1 and TRPV4 in distension-induced colonic nociception and pain, TRP-deficient mice and selective pharmacological blockers in wild-type mice (WT) were used. Visceromotor responses (VMR) to colorectal distension (CRD) in vivo were recorded and distension/pressure-induced CGRP release from the isolated murine colon ex vivo was measured by EIA. Results Distension-induced colonic CGRP release was markedly reduced in TRPA1-/- and TRPV4-/- mice at 90/150 mmHg compared to WT. In TRPM8-deficient mice the reduction was only distinct at 150 mmHg. Exposure to selective pharmacological antagonists (HC030031, 100 μM; RN1734, 10 μM; AMTB, 10 μM) showed corresponding effects. The unselective TRP blocker ruthenium red (RR, 10 μM) was as efficient in inhibiting distension-induced CGRP release as the unselective antagonists of mechanogated DEG/ENaC (amiloride, 100 μM) and stretch-activated channels (gadolinium, 50 μM). VMR to CRD revealed prominent deficits over the whole pressure range (up to 90 mmHg) in TRPA1-/- and TRPV4-/- but not TRPM8-/- mice; the drug effects of the TRP antagonists were again highly consistent with the results from mice lacking the respective TRP receptor gene. Conclusions TRPA1 and TRPV4 mediate colonic distension pain and CGRP release and appear to govern a wide and congruent dynamic range of distensions. The role of TRPM8 seems to be confined to signaling extreme noxious distension, at least in the healthy colon.
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Affiliation(s)
- Sonja M. Mueller-Tribbensee
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Manoj Karna
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Mohammad Khalil
- Department of Medicine 1, Universitätsklinikum Erlangen, Erlangen, Germany
| | - Markus F. Neurath
- Department of Medicine 1, Universitätsklinikum Erlangen, Erlangen, Germany
| | - Peter W. Reeh
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Matthias A. Engel
- Department of Medicine 1, Universitätsklinikum Erlangen, Erlangen, Germany
- * E-mail:
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89
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Nikolaev YA, Dosen PJ, Laver DR, van Helden DF, Hamill OP. Single mechanically-gated cation channel currents can trigger action potentials in neocortical and hippocampal pyramidal neurons. Brain Res 2015; 1608:1-13. [PMID: 25765154 DOI: 10.1016/j.brainres.2015.02.051] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 02/26/2015] [Indexed: 02/04/2023]
Abstract
The mammalian brain is a mechanosensitive organ that responds to different mechanical forces ranging from intrinsic forces implicated in brain morphogenesis to extrinsic forces that can cause concussion and traumatic brain injury. However, little is known of the mechanosensors that transduce these forces. In this study we use cell-attached patch recording to measure single mechanically-gated (MG) channel currents and their affects on spike activity in identified neurons in neonatal mouse brain slices. We demonstrate that both neocortical and hippocampal pyramidal neurons express stretch-activated MG cation channels that are activated by suctions of ~25mm Hg, have a single channel conductance for inward current of 50-70pS and show weak selectivity for alkali metal cations (i.e., Na(+)<K(+)<Cs(+)). Significantly, single MG channel currents activated on the soma trigger spiking/action potentials in both neocortical and hippocampal pyramidal neurons. Not all neuron types studied here expressed MG channel currents. In particular, locus coeruleus and cerebellar Purkinje neurons showed no detectable MG channel activity. Moreover their robust rhythmic spike activity was resistant to mechanical modulation. Our observation that a single MG channel current can trigger spiking predicates the need for reassessment of the long held view that the impulse output of central neurons depends only upon their intrinsic voltage-gated channels and/or their integrated synaptic input.
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Affiliation(s)
- Yury A Nikolaev
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia; Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia
| | - Peter J Dosen
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | - Owen P Hamill
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia; Department of Neuroscience and Cell Biology, UTMB, Galveston, TX 77555, USA.
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90
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L596-W733 bond between the start of the S4-S5 linker and the TRP box stabilizes the closed state of TRPV4 channel. Proc Natl Acad Sci U S A 2015; 112:3386-91. [PMID: 25737550 DOI: 10.1073/pnas.1502366112] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Unlike other cation channels, each subunit of most transient receptor potential (TRP) channels has an additional TRP-domain helix with an invariant tryptophan immediately trailing the gate-bearing S6. Recent cryo-electron microscopy of TRP vanilloid subfamily, member 1 structures revealed that this domain is a five-turn amphipathic helix, and the invariant tryptophan forms a bond with the beginning of the four-turn S4-S5 linker helix. By homology modeling, we identified the corresponding L596-W733 bond in TRP vanilloid subfamily, member 4 (TRPV4). The L596P mutation blocks bone development in Kozlowski-type spondylometaphyseal dysplasia in human. Our previous screen also isolated W733R as a strong gain-of-function (GOF) mutation that suppresses growth when the W733R channel is expressed in yeast. We show that, when expressed in Xenopus oocytes, TRPV4 with the L596P or W733R mutation displays normal depolarization-induced activation and outward rectification. However, these mutant channels have higher basal open probabilities and limited responses to the agonist GSK1016790A, explaining their biological GOF phenotypes. In addition, W733R current fails to inactivate during depolarization. Systematic replacement of W733 with amino acids of different properties produced similar electrophysiological and yeast phenotypes. The results can be interpreted consistently in the context of the homology model of TRPV4 molecule we have developed and refined using simulations in explicit medium. We propose that this bond maintains the orientation of the S4-S5 linker to keep the S6 gate closed. Further, the two partner helices, both amphipathic and located at the polar-nonpolar interface of the inner lipid monolayer, may receive and integrate various physiological stimuli.
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91
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Swelling and eicosanoid metabolites differentially gate TRPV4 channels in retinal neurons and glia. J Neurosci 2015; 34:15689-700. [PMID: 25411497 DOI: 10.1523/jneurosci.2540-14.2014] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Activity-dependent shifts in ionic concentrations and water that accompany neuronal and glial activity can generate osmotic forces with biological consequences for brain physiology. Active regulation of osmotic gradients and cellular volume requires volume-sensitive ion channels. In the vertebrate retina, critical support to volume regulation is provided by Müller astroglia, but the identity of their osmosensor is unknown. Here, we identify TRPV4 channels as transducers of mouse Müller cell volume increases into physiological responses. Hypotonic stimuli induced sustained [Ca(2+)]i elevations that were inhibited by TRPV4 antagonists and absent in TRPV4(-/-) Müller cells. Glial TRPV4 signals were phospholipase A2- and cytochrome P450-dependent, characterized by slow-onset and Ca(2+) waves, and, in excess, were sufficient to induce reactive gliosis. In contrast, neurons responded to TRPV4 agonists and swelling with fast, inactivating Ca(2+) signals that were independent of phospholipase A2. Our results support a model whereby swelling and proinflammatory signals associated with arachidonic acid metabolites differentially gate TRPV4 in retinal neurons and glia, with potentially significant consequences for normal and pathological retinal function.
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92
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Nilius B, Szallasi A. Transient receptor potential channels as drug targets: from the science of basic research to the art of medicine. Pharmacol Rev 2014; 66:676-814. [PMID: 24951385 DOI: 10.1124/pr.113.008268] [Citation(s) in RCA: 377] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2025] Open
Abstract
The large Trp gene family encodes transient receptor potential (TRP) proteins that form novel cation-selective ion channels. In mammals, 28 Trp channel genes have been identified. TRP proteins exhibit diverse permeation and gating properties and are involved in a plethora of physiologic functions with a strong impact on cellular sensing and signaling pathways. Indeed, mutations in human genes encoding TRP channels, the so-called "TRP channelopathies," are responsible for a number of hereditary diseases that affect the musculoskeletal, cardiovascular, genitourinary, and nervous systems. This review gives an overview of the functional properties of mammalian TRP channels, describes their roles in acquired and hereditary diseases, and discusses their potential as drug targets for therapeutic intervention.
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Affiliation(s)
- Bernd Nilius
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, Campus Gasthuisberg, Leuven, Belgium (B.N.); and Department of Pathology, Monmouth Medical Center, Long Branch, New Jersey (A.S.)
| | - Arpad Szallasi
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, Campus Gasthuisberg, Leuven, Belgium (B.N.); and Department of Pathology, Monmouth Medical Center, Long Branch, New Jersey (A.S.)
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93
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Teng J, Loukin S, Anishkin A, Kung C. The force-from-lipid (FFL) principle of mechanosensitivity, at large and in elements. Pflugers Arch 2014; 467:27-37. [PMID: 24888690 DOI: 10.1007/s00424-014-1530-2] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 04/29/2014] [Accepted: 05/05/2014] [Indexed: 12/27/2022]
Abstract
Focus on touch and hearing distracts attention from numerous subconscious force sensors, such as the vital control of blood pressure and systemic osmolarity, and sensors in nonanimals. Multifarious manifestations should not obscure invariant and fundamental physicochemical principles. We advocate that force from lipid (FFL) is one such principle. It is based on the fact that the self-assembled bilayer necessitates inherent forces that are large and anisotropic, even at life's origin. Functional response of membrane proteins is governed by bilayer force changes. Added stress can redirect these forces, leading to geometric changes of embedded proteins such as ion channels. The FFL principle was first demonstrated when purified bacterial mechanosensitive channel of large conductance (MscL) remained mechanosensitive (MS) after reconstituting into bilayers. This key experiment has recently been unequivocally replicated with two vertebrate MS K2p channels. Even the canonical Kv and the Drosophila canonical transient receptor potentials (TRPCs) have now been shown to be MS in biophysical and in physiological contexts, supporting the universality of the FFL paradigm. We also review the deterministic role of mechanical force during stem cell differentiation as well as the cell-cell and cell-matrix tethers that provide force communications. In both the ear hair cell and the worm's touch neuron, deleting the cadherin or microtubule tethers reduces but does not eliminate MS channel activities. We found no evidence to distinguish whether these tethers directly pull on the channel protein or a surrounding lipid platform. Regardless of the implementation, pulling tether tenses up the bilayer. Membrane tenting is directly visible at the apexes of the stereocilia.
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Affiliation(s)
- Jinfeng Teng
- Laboratory of Molecular Biology, University of Wisconsin, Madison, WI, 53706, USA
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94
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Feeling the hidden mechanical forces in lipid bilayer is an original sense. Proc Natl Acad Sci U S A 2014; 111:7898-905. [PMID: 24850861 DOI: 10.1073/pnas.1313364111] [Citation(s) in RCA: 213] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Life's origin entails enclosing a compartment to hoard material, energy, and information. The envelope necessarily comprises amphipaths, such as prebiotic fatty acids, to partition the two aqueous domains. The self-assembled lipid bilayer comes with a set of properties including its strong anisotropic internal forces that are chemically or physically malleable. Added bilayer stretch can alter force vectors on embedded proteins to effect conformational change. The force-from-lipid principle was demonstrated 25 y ago when stretches opened purified Escherichia coli MscL channels reconstituted into artificial bilayers. This reductionistic exercise has rigorously been recapitulated recently with two vertebrate mechanosensitive K(+) channels (TREK1 and TRAAK). Membrane stretches have also been known to activate various voltage-, ligand-, or Ca(2+)-gated channels. Careful analyses showed that Kv, the canonical voltage-gated channel, is in fact exquisitely sensitive even to very small tension. In an unexpected context, the canonical transient-receptor-potential channels in the Drosophila eye, long presumed to open by ligand binding, is apparently opened by membrane force due to PIP2 hydrolysis-induced changes in bilayer strain. Being the intimate medium, lipids govern membrane proteins by physics as well as chemistry. This principle should not be a surprise because it parallels water's paramount role in the structure and function of soluble proteins. Today, overt or covert mechanical forces govern cell biological processes and produce sensations. At the genesis, a bilayer's response to osmotic force is likely among the first senses to deal with the capricious primordial sea.
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95
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Miyamoto T, Mochizuki T, Nakagomi H, Kira S, Watanabe M, Takayama Y, Suzuki Y, Koizumi S, Takeda M, Tominaga M. Functional role for Piezo1 in stretch-evoked Ca²⁺ influx and ATP release in urothelial cell cultures. J Biol Chem 2014; 289:16565-75. [PMID: 24759099 DOI: 10.1074/jbc.m113.528638] [Citation(s) in RCA: 243] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The urothelium is a sensory structure that contributes to mechanosensation in the urinary bladder. Here, we provide evidence for a critical role for the Piezo1 channel, a newly identified mechanosensory molecule, in the mouse bladder urothelium. We performed a systematic analysis of the molecular and functional expression of Piezo1 channels in the urothelium. Immunofluorescence examination demonstrated abundant expression of Piezo1 in the mouse and human urothelium. Urothelial cells isolated from mice exhibited a Piezo1-dependent increase in cytosolic Ca(2+) concentrations in response to mechanical stretch stimuli, leading to potent ATP release; this response was suppressed in Piezo1-knockdown cells. In addition, Piezo1 and TRPV4 distinguished different intensities of mechanical stimulus. Moreover, GsMTx4, an inhibitor of stretch-activated channels, attenuated the Ca(2+) influx into urothelial cells and decreased ATP release from them upon stretch stimulation. These results suggest that Piezo1 senses extension of the bladder urothelium, leading to production of an ATP signal. Thus, inhibition of Piezo1 might provide a promising means of treating bladder dysfunction.
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Affiliation(s)
- Tatsuya Miyamoto
- From the Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898
| | - Tsutomu Mochizuki
- From the Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898,
| | - Hiroshi Nakagomi
- From the Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898
| | - Satoru Kira
- From the Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898
| | - Masaki Watanabe
- the Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, Aichi 444-8787
| | - Yasunori Takayama
- the Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, Aichi 444-8787
| | - Yoshiro Suzuki
- the Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, Aichi 444-8787, the Department of Physiological Sciences, Graduate University for Advanced Studies, Okazaki 444-8585, and
| | - Schuichi Koizumi
- the Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Masayuki Takeda
- From the Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898
| | - Makoto Tominaga
- the Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, Aichi 444-8787, the Department of Physiological Sciences, Graduate University for Advanced Studies, Okazaki 444-8585, and
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96
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Taylor L, Arnér K, Taylor IH, Ghosh F. Feet on the ground: Physical support of the inner retina is a strong determinant for cell survival and structural preservation in vitro. Invest Ophthalmol Vis Sci 2014; 55:2200-13. [PMID: 24595389 DOI: 10.1167/iovs.13-13535] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The purpose of this study was to explore the importance of local physical tissue support for homeostasis in the isolated retina. METHODS Full-thickness retinal sheets were isolated from adult porcine eyes. Retinas were cultured for 5 or 10 days using the previously established explant protocol with photoreceptors positioned against the culture membrane (porous polycarbonate) or the Müller cell endfeet and inner limiting membrane (ILM) apposed against the membrane. The explants were analyzed morphologically using hematoxylin and eosin staining, immunohistochemistry, TUNEL labeling, and transmission electron microscopy (TEM). RESULTS Standard cultures displayed a progressive loss of retinal lamination and extensive cell death, with activated, hypertrophic Müller cells. In contrast, explants cultured with the ILM facing the membrane displayed a maintenance of the retinal laminar architecture, and a statistically significant attenuation of photoreceptor and ganglion cell death. Transmission electron microscopy revealed intact synapses as well as preservation of normal cellular membrane structures. Immunohistochemistry showed no signs of Müller cell activation (glial fibrillary acidic protein [GFAP]), with maintained expression of important metabolic markers (glutamine synthetae [GS], bFGF). CONCLUSIONS Providing physical support to the inner but not the outer retina appears to prevent the tissue collapse resulting from perturbation of the normal biomechanical milieu in the isolated retinal sheet. Using this novel paradigm, gliotic reactions are attenuated and metabolic processes vital for tissue health are preserved, which significantly increases neuronal cell survival. This finding opens up new avenues of adult retinal tissue culture research and increases our understanding of pathological reactions in biomechanically related conditions in vivo.
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Affiliation(s)
- Linnéa Taylor
- Department of Ophthalmology, Lund University Hospital, Lund, Sweden
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97
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Mechanosensitive Ion Channels in Cardiovascular Physiology. Exp Clin Cardiol 2014; 20:6550-6560. [PMID: 26778915 PMCID: PMC4713040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
EC coupling is subjected to a mechanical feedback, which originates from physical force-sensing ion channels in the pericardium and elsewhere. Reviewed here are the most recent developments that greatly advanced our understanding of these mechanosensitive (MS) channels, including TRPs and K2p's. Patch clamp has continued to demonstrate the direct channel activation by membrane stretch. Crystallography and cryo-electron microscopy have revealed the structures of several MS channels at atomic resolution. Some have been purified to homogeneity, reconstituted into lipid bilayer, and still retain their ability to respond to stretch force. A force-from-lipid (FFL) theory has been advanced that emphasizes the strong binding between channel proteins and lipids. Through these bonds, the sharp lateral tension (akin to surface tension) of the bilayer can transmit added force to the channel protein. Like temperature sensitivity, sensitivity to mechanical force is far more pervasive than we previously realize, and is especially important to the beating heart.
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98
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Abstract
The widely distributed TRPV4 cationic channel participates in the transduction of both physical (osmotic, mechanical, and heat) and chemical (endogenous, plant-derived, and synthetic ligands) stimuli. In this chapter we will review TRPV4 expression, biophysics, structure, regulation, and interacting partners as well as physiological and pathological insights obtained in TRPV4 animal models and human genetic studies.
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99
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Teng J, Loukin S, Zhou X, Kung C. Yeast luminometric and Xenopus oocyte electrophysiological examinations of the molecular mechanosensitivity of TRPV4. J Vis Exp 2013:50816. [PMID: 24637628 PMCID: PMC4396860 DOI: 10.3791/50816] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
TRPV4 (Transient Receptor Potentials, vanilloid family, type 4) is widely expressed in vertebrate tissues and is activated by several stimuli, including by mechanical forces. Certain TRPV4 mutations cause complex hereditary bone or neuronal pathologies in human. Wild-type or mutant TRPV4 transgenes are commonly expressed in cultured mammalian cells and examined by Fura-2 fluorometry and by electrodes. In terms of the mechanism of mechanosensitivity and the molecular bases of the diseases, the current literature is confusing and controversial. To complement existing methods, we describe two additional methods to examine the molecular properties of TRPV4. (1) Rat TRPV4 and an aequorin transgene are transformed into budding yeast. A hypo-osmtic shock of the transformant population yields a luminometric signal due to the combination of aequorin with Ca(2+), released through the TRPV4 channel. Here TRPV4 is isolated from its usual mammalian partner proteins and reveals its own mechanosensitivity. (2) cRNA of TRPV4 is injected into Xenopus oocytes. After a suitable period of incubation, the macroscopic TRPV4 current is examined with a two-electrode voltage clamp. The current rise upon removal of inert osmoticum from the oocyte bath is indicative of mechanosensitivity. The microAmpere (10(-6) to 10(-4) A) currents from oocytes are much larger than the subnano- to nanoAmpere (10(-10) to 10(-9) A) currents from cultured cells, yielding clearer quantifications and more confident assessments. Microscopic currents reflecting the activities of individual channel proteins can also be directly registered under a patch clamp, in on-cell or excised mode. The same oocyte provides multiple patch samples, allowing better data replication. Suctions applied to the patches can activate TRPV4 to directly assess mechanosensitivity. These methods should also be useful in the study of other types of TRP channels.
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Affiliation(s)
- Jinfeng Teng
- Laboratory of Cell and Molecular Biology, University of Wisconsin - Madison
| | - Stephen Loukin
- Laboratory of Cell and Molecular Biology, University of Wisconsin - Madison
| | - Xinliang Zhou
- Laboratory of Cell and Molecular Biology, University of Wisconsin - Madison
| | - Ching Kung
- Laboratory of Cell and Molecular Biology, University of Wisconsin - Madison; Department of Genetics, University of Wisconsin - Madison;
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Klausen TK, Janssens A, Prenen J, Owsianik G, Hoffmann EK, Pedersen SF, Nilius B. Single point mutations of aromatic residues in transmembrane helices 5 and -6 differentially affect TRPV4 activation by 4α-PDD and hypotonicity: implications for the role of the pore region in regulating TRPV4 activity. Cell Calcium 2013; 55:38-47. [PMID: 24342753 DOI: 10.1016/j.ceca.2013.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 11/08/2013] [Indexed: 12/20/2022]
Abstract
The importance of the TRPV4 channel for human physiology has been highlighted in recent years with the identification of an increasing number of hereditary diseases associated with mutations of this channel. However, the functional understanding of TRPV4 associated pathologies remains a puzzle due to incomplete understanding of the polymodal regulation of TRPV4 channels and lack of insight into the structure-function relationship of the channel. In this work, we identified a series of highly conserved aromatic residues in transmembrane (TM) helices 5-6 with profound importance for TRPV4 activity. Substituting F617, Y621 or F624 in TM5 with leucine reduced channel sensitivity to the agonist 4α-PDD and heat, yet two of these mutants - F617L and Y621L - showed increased activation in response to cell swelling. In TM6, a Y702L mutation significantly reduced sensitivity to all of the above stimuli. In conclusion, we have identified residues in TM5-6 which differentially affect heat and agonist activation, and we have demonstrated distinct activation pathways for 4α-PDD and osmolarity.
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Affiliation(s)
- Thomas Kjær Klausen
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49, Bus 802, Leuven, Belgium; Department of Biology, The August Krogh Building, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark.
| | - Annelies Janssens
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49, Bus 802, Leuven, Belgium
| | - Jean Prenen
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49, Bus 802, Leuven, Belgium
| | - Grzegorz Owsianik
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49, Bus 802, Leuven, Belgium
| | - Else Kay Hoffmann
- Department of Biology, The August Krogh Building, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
| | - Stine Falsig Pedersen
- Department of Biology, The August Krogh Building, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
| | - Bernd Nilius
- KU Leuven, Department of Cellular and Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49, Bus 802, Leuven, Belgium
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