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Liu X, Wang J, Sun L. Structure of the hyperosmolality-gated calcium-permeable channel OSCA1.2. Nat Commun 2018; 9:5060. [PMID: 30498218 PMCID: PMC6265326 DOI: 10.1038/s41467-018-07564-5] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/09/2018] [Indexed: 01/08/2023] Open
Abstract
In plants, hyperosmolality stimuli triggers opening of the osmosensitive channels, leading to a rapid downstream signaling cascade initiated by cytosolic calcium concentration elevation. Members of the OSCA family in Arabidopsis thaliana, identified as the hyperosmolality-gated calcium-permeable channels, have been suggested to play a key role during the initial phase of hyperosmotic stress response. Here, we report the atomic structure of Arabidopsis OSCA1.2 determined by single-particle cryo-electron microscopy. It contains 11 transmembrane helices and forms a homodimer. It is in an inactivated state, and the pore-lining residues are clearly identified. Its cytosolic domain contains a RNA recognition motif and two unique long helices. The linker between these two helices forms an anchor in the lipid bilayer and may be essential to osmosensing. The structure of AtOSCA1.2 serves as a platform for the study of the mechanism underlying osmotic stress responses and mechanosensing. In plants, hyperosmolality stimuli triggers opening of the osmosensitive channels, leading to a rapid downstream signaling cascade. Here, the authors solve the cryo-EM structure of an osmosensitive channel from Arabidopsis OSCA1.2 in its inactivated state.
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Affiliation(s)
- Xin Liu
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 230027, Hefei, China
| | - Jiawei Wang
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Centre for Structural Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China.
| | - Linfeng Sun
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 230027, Hefei, China. .,CAS Centre for Excellence in Molecular Cell Science, University of Science and Technology of China, Chinese Academy of Sciences, 230027, Hefei, China.
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Gnanasambandam R, Gottlieb PA, Sachs F. The Kinetics and the Permeation Properties of Piezo Channels. CURRENT TOPICS IN MEMBRANES 2017; 79:275-307. [PMID: 28728821 DOI: 10.1016/bs.ctm.2016.11.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Piezo channels are eukaryotic, cation-selective mechanosensitive channels (MSCs), which show rapid activation and voltage-dependent inactivation. The kinetics of these channels are largely consistent across multiple cell types and different stimulation paradigms with some minor variability. No accessory subunits that associate with Piezo channels have been reported. They are homotrimers and each ∼300kD monomer has an N-terminal propeller blade-like mechanosensing module, which can confer mechanosensing capabilities on ASIC-1 (the trimeric non-MSC, acid-sensing ion channel-1) and a C-terminal pore module, which influences conductance, selectivity, and channel inactivation. Repeated stimulation can cause domain fracture and diffusion of these channels leading to synchronous loss of inactivation. The reconstituted channels spontaneously open only in asymmetric bilayers but lack inactivation. Mutations that cause hereditary xerocytosis alter PIEZO1 kinetics. The kinetics of the wild-type PIEZO1 and alterations thereof in mutants (M2225R, R2456K, and DhPIEZO1) are summarized in the form of a quantitative model and hosted online. The pore is permeable to alkali ions although Li+ permeates poorly. Divalent cations, notably Ca2+, traverse the channel and inhibit the flux of monovalents. The large monovalent organic cations such as tetramethyl ammonium and tetraethyl ammonium can traverse the channel, but slowly, suggesting a pore diameter of ∼8Å, and the estimated in-plane area change upon opening is around 6-20nm2. Ruthenium red can enter the channel only from the extracellular side and seems to bind in a pocket close to residue 2496.
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Affiliation(s)
- R Gnanasambandam
- State University of New York at Buffalo, Buffalo, NY, United States
| | - P A Gottlieb
- State University of New York at Buffalo, Buffalo, NY, United States
| | - F Sachs
- State University of New York at Buffalo, Buffalo, NY, United States
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Cox CD, Bae C, Ziegler L, Hartley S, Nikolova-Krstevski V, Rohde PR, Ng CA, Sachs F, Gottlieb PA, Martinac B. Removal of the mechanoprotective influence of the cytoskeleton reveals PIEZO1 is gated by bilayer tension. Nat Commun 2016; 7:10366. [PMID: 26785635 PMCID: PMC4735864 DOI: 10.1038/ncomms10366] [Citation(s) in RCA: 322] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Accepted: 12/04/2015] [Indexed: 12/18/2022] Open
Abstract
Mechanosensitive ion channels are force-transducing enzymes that couple mechanical stimuli to ion flux. Understanding the gating mechanism of mechanosensitive channels is challenging because the stimulus seen by the channel reflects forces shared between the membrane, cytoskeleton and extracellular matrix. Here we examine whether the mechanosensitive channel PIEZO1 is activated by force-transmission through the bilayer. To achieve this, we generate HEK293 cell membrane blebs largely free of cytoskeleton. Using the bacterial channel MscL, we calibrate the bilayer tension demonstrating that activation of MscL in blebs is identical to that in reconstituted bilayers. Utilizing a novel PIEZO1-GFP fusion, we then show PIEZO1 is activated by bilayer tension in bleb membranes, gating at lower pressures indicative of removal of the cortical cytoskeleton and the mechanoprotection it provides. Thus, PIEZO1 channels must sense force directly transmitted through the bilayer.
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Affiliation(s)
- Charles D. Cox
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Chilman Bae
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Lynn Ziegler
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Silas Hartley
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | | | - Paul R. Rohde
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Chai-Ann Ng
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Frederick Sachs
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
- The Centre for Single Molecule Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Philip A. Gottlieb
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
- The Centre for Single Molecule Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
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Sachs F. Mechanical transduction by ion channels: A cautionary tale. World J Neurol 2015; 5:74-87. [PMID: 28078202 PMCID: PMC5221657 DOI: 10.5316/wjn.v5.i3.74] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 08/23/2014] [Accepted: 07/17/2015] [Indexed: 02/06/2023] Open
Abstract
Mechanical transduction by ion channels occurs in all cells. The physiological functions of these channels have just begun to be elaborated, but if we focus on the upper animal kingdom, these channels serve the common sensory services such as hearing and touch, provide the central nervous system with information on the force and position of muscles and joints, and they provide the autonomic system with information about the filling of hollow organs such as blood vessels. However, all cells of the body have mechanosensitive channels (MSCs), including red cells. Most of these channels are cation selective and are activated by bilayer tension. There are also K+ selective MSCs found commonly in neurons where they may be responsible for both general anesthesia and knockout punches in the boxing ring by hyperpolarizing neurons to reduce excitability. The cationic MSCs are typically inactive under normal mechanical stress, but open under pathologic stress. The channels are normally inactive because they are shielded from stress by the cytoskeleton. The cationic MSCs are specifically blocked by the externally applied peptide GsMtx4 (aka, AT-300). This is the first drug of its class and provides a new approach to many pathologies since it is nontoxic, non-immunogenic, stable in a biological environment and has a long pharmacokinetic lifetime. Pathologies involving excessive stress are common. They produce cardiac arrhythmias, contraction in stretched dystrophic muscle, xerocytotic and sickled red cells, etc. The channels seem to function primarily as “fire alarms”, providing feedback to the cytoskeleton that a region of the bilayer is under excessive tension and needs reinforcing. The eukaryotic forms of MSCs have only been cloned in recent years and few people have experience working with them. “Newbies” need to become aware of the technology, potential artifacts, and the fundamentals of mechanics. The most difficult problem in studying MSCs is that the actual stimulus, the force applied to the channel, is not known. We don’t have direct access to the channels themselves but only to larger regions of the membrane as seen in patches. Cortical forces are shared by the bilayer, the cytoskeleton and the extracellular matrix. How much of an applied stimulus reaches the channel is unknown. Furthermore, many of these channels exist in spatial domains where the forces within a domain are different from forces outside the domain, although we often hope they are proportional. This review is intended to be a guide for new investigators who want to study mechanosensitive ion channels.
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Hamilton ES, Schlegel AM, Haswell ES. United in diversity: mechanosensitive ion channels in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2014; 66:113-37. [PMID: 25494462 PMCID: PMC4470482 DOI: 10.1146/annurev-arplant-043014-114700] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Mechanosensitive (MS) ion channels are a common mechanism for perceiving and responding to mechanical force. This class of mechanoreceptors is capable of transducing membrane tension directly into ion flux. In plant systems, MS ion channels have been proposed to play a wide array of roles, from the perception of touch and gravity to the osmotic homeostasis of intracellular organelles. Three families of plant MS ion channels have been identified: the MscS-like (MSL), Mid1-complementing activity (MCA), and two-pore potassium (TPK) families. Channels from these families vary widely in structure and function, localize to multiple cellular compartments, and conduct chloride, calcium, and/or potassium ions. However, they are still likely to represent only a fraction of the MS ion channel diversity in plant systems.
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Affiliation(s)
- Eric S. Hamilton
- Department of Biology, Washington University in Saint Louis, Saint Louis, Missouri 63130
| | - Angela M. Schlegel
- Department of Biology, Washington University in Saint Louis, Saint Louis, Missouri 63130
| | - Elizabeth S. Haswell
- Department of Biology, Washington University in Saint Louis, Saint Louis, Missouri 63130
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Herold KF, Sanford RL, Lee W, Schultz MF, Ingólfsson HI, Andersen OS, Hemmings HC. Volatile anesthetics inhibit sodium channels without altering bulk lipid bilayer properties. J Gen Physiol 2014; 144:545-60. [PMID: 25385786 PMCID: PMC4242807 DOI: 10.1085/jgp.201411172] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 10/08/2014] [Indexed: 01/05/2023] Open
Abstract
Although general anesthetics are clinically important and widely used, their molecular mechanisms of action remain poorly understood. Volatile anesthetics such as isoflurane (ISO) are thought to alter neuronal function by depressing excitatory and facilitating inhibitory neurotransmission through direct interactions with specific protein targets, including voltage-gated sodium channels (Na(v)). Many anesthetics alter lipid bilayer properties, suggesting that ion channel function might also be altered indirectly through effects on the lipid bilayer. We compared the effects of ISO and of a series of fluorobenzene (FB) model volatile anesthetics on Na(v) function and lipid bilayer properties. We examined the effects of these agents on Na(v) in neuronal cells using whole-cell electrophysiology, and on lipid bilayer properties using a gramicidin-based fluorescence assay, which is a functional assay for detecting changes in lipid bilayer properties sensed by a bilayer-spanning ion channel. At clinically relevant concentrations (defined by the minimum alveolar concentration), both the FBs and ISO produced prepulse-dependent inhibition of Na(v) and shifted the voltage dependence of inactivation toward more hyperpolarized potentials without affecting lipid bilayer properties, as sensed by gramicidin channels. Only at supra-anesthetic (toxic) concentrations did ISO alter lipid bilayer properties. These results suggest that clinically relevant concentrations of volatile anesthetics alter Na(v) function through direct interactions with the channel protein with little, if any, contribution from changes in bulk lipid bilayer properties. Our findings further suggest that changes in lipid bilayer properties are not involved in clinical anesthesia.
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Affiliation(s)
- Karl F Herold
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - R Lea Sanford
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - William Lee
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Margaret F Schultz
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Helgi I Ingólfsson
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Olaf S Andersen
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Hugh C Hemmings
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065 Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
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Abstract
This chapter reviews recent evidence indicating that canonical or classical transient receptor potential (TRPC) channels are directly or indirectly mechanosensitive (MS) and can therefore be designated as mechano-operated channels (MOCs). The MS functions of TRPCs may be mechanistically related to their better known functions as store-operated and receptor-operated channels (SOCs and ROCs). Mechanical forces may be conveyed to TRPC channels through the "conformational coupling" mechanism that transmits information regarding the status of internal Ca(2+) stores. All TRPCs are regulated by receptors coupled to phospholipases that are themselves MS and can regulate channels via lipidic second messengers. Accordingly, there may be several nonexclusive mechanisms by which mechanical forces may regulate TRPC channels, including direct sensitivity to bilayer mechanics, physical coupling to internal membranes and/or cytoskeletal proteins, and sensitivity to lipidic second messengers generated by MS enzymes. Various strategies that can be used for separating out different MS-gating mechanisms and their possible role in specific TRPCs are discussed.
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Affiliation(s)
- Owen P Hamill
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Rosario Maroto
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
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Bowman CL, Gottlieb PA, Suchyna TM, Murphy YK, Sachs F. Mechanosensitive ion channels and the peptide inhibitor GsMTx-4: history, properties, mechanisms and pharmacology. Toxicon 2007; 49:249-70. [PMID: 17157345 PMCID: PMC1852511 DOI: 10.1016/j.toxicon.2006.09.030] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Sensing the energy from mechanical inputs is ubiquitous--and perhaps the oldest form of biological energy transduction. However, the tools available to probe the mechanisms of transduction are far fewer than for the chemical and electric field sensitive transducers. The one pharmacological tool available for mechansensitive ion channels (MSCs) is a peptide (GsMTx-4) isolated from venom of the tarantula, Grammostola spatulata, that blocks cationic MSCs found in non-specialized eukaryotic tissues. In this review, we summarize the current knowledge of GsMTx-4, and discuss the inevitable crosstalk between the MSC behavior and the mechanical properties of the cell cortex.
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Affiliation(s)
- Charles L Bowman
- Center for Single Molecule Biophysics and The Department of Physiology and Biophysics, SUNY at Buffalo, Buffalo, NY 14214, USA.
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