1
|
Miles L, Powell J, Kozak C, Song Y. Mechanosensitive Ion Channels, Axonal Growth, and Regeneration. Neuroscientist 2022:10738584221088575. [PMID: 35414308 PMCID: PMC9556659 DOI: 10.1177/10738584221088575] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cells sense and respond to mechanical stimuli by converting those stimuli into biological signals, a process known as mechanotransduction. Mechanotransduction is essential in diverse cellular functions, including tissue development, touch sensitivity, pain, and neuronal pathfinding. In the search for key players of mechanotransduction, several families of ion channels were identified as being mechanosensitive and were demonstrated to be activated directly by mechanical forces in both the membrane bilayer and the cytoskeleton. More recently, Piezo ion channels were discovered as a bona fide mechanosensitive ion channel, and its characterization led to a cascade of research that revealed the diverse functions of Piezo proteins and, in particular, their involvement in neuronal repair.
Collapse
Affiliation(s)
- Leann Miles
- The Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, PA, USA
| | - Jackson Powell
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Casey Kozak
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Yuanquan Song
- The Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, PA, USA.,Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| |
Collapse
|
2
|
Hamza A, Amit J, Elizabeth L E, Medha M P, Michael D C, Wendy F L. Ion channel mediated mechanotransduction in immune cells. CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE 2021; 25. [PMID: 35645593 PMCID: PMC9131931 DOI: 10.1016/j.cossms.2021.100951] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The immune system performs critical functions to defend against invading pathogens and maintain tissue homeostasis. Immune cells reside within or are recruited to a host of mechanically active tissues throughout the body and, as a result, are exposed to varying types and degrees of mechanical stimuli. Despite their abundance in such tissues, the role of mechanical stimuli in influencing immune cell function and the molecular mechanisms responsible for mechanics-mediated changes are still poorly understood. The recent emergence of mechanically-gated ion channels, particularly Piezo1, has provided an exciting avenue of research within the fields of mechanobiology and immunology. Numerous studies have identified roles for mechanically-gated ion channels in mechanotransduction within various different cell types, with a few recent studies in immune cells. These initial studies provide strong evidence that mechanically-gated ion channels play pivotal roles in regulating the immune system. In this review, we discuss characteristics of ion channel mediated force transduction, review the current techniques used to quantify and visualize ion channel activity in response to mechanical stimuli, and finally we provide an overview of recent studies examining the role of mechanically-gated ion channels in modulating immune cell function.
Collapse
Affiliation(s)
- Atcha Hamza
- Department of Biomedical Engineering, University of California Irvine, Irvine, USA
- The Edwards Lifesciences Center for Advanced Cardiovascular Technology, University of California Irvine, Irvine, USA
| | - Jairaman Amit
- Department of Physiology and Biophysics, University of California Irvine, Irvine, USA
| | - Evans Elizabeth L
- Department of Physiology and Biophysics, University of California Irvine, Irvine, USA
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, USA
| | - Pathak Medha M
- Department of Biomedical Engineering, University of California Irvine, Irvine, USA
- Department of Physiology and Biophysics, University of California Irvine, Irvine, USA
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, USA
| | - Cahalan Michael D
- Department of Physiology and Biophysics, University of California Irvine, Irvine, USA
| | - Liu Wendy F
- Department of Biomedical Engineering, University of California Irvine, Irvine, USA
- The Edwards Lifesciences Center for Advanced Cardiovascular Technology, University of California Irvine, Irvine, USA
- Department of Chemical and Biomolecular Engineering, University of California Irvine, Irvine, USA
| |
Collapse
|
3
|
Guo Y, Merten AL, Schöler U, Yu ZY, Cvetkovska J, Fatkin D, Feneley MP, Martinac B, Friedrich O. In vitro cell stretching technology (IsoStretcher) as an approach to unravel Piezo1-mediated cardiac mechanotransduction. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 159:22-33. [PMID: 32763257 DOI: 10.1016/j.pbiomolbio.2020.07.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 07/09/2020] [Accepted: 07/13/2020] [Indexed: 12/12/2022]
Abstract
The transformation of electrical signals into mechanical action of the heart underlying blood circulation results in mechanical stimuli during active contraction or passive filling distention, which conversely modulate electrical signals. This feedback mechanism is known as cardiac mechano-electric coupling (MEC). The cardiac MEC involves complex activation of mechanical biosensors initiating short-term and long-term effects through Ca2+ signals in cardiomyocytes in acute and chronic pressure overload scenarios (e.g. cardiac hypertrophy). Although it is largely still unknown how mechanical forces alter cardiac function at the molecular level, mechanosensitive channels, including the recently discovered family of Piezo channels, have been thought to play a major role in the cardiac MEC and are also suspected to contribute to development of cardiac hypertrophy and heart failure. The earliest reports of mechanosensitive channel activity recognized that their gating could be controlled by membrane stretch. In this article, we provide an overview of the stretch devices, which have been employed for studies of the effects of mechanical stimuli on muscle and heart cells. We also describe novel experiments examining the activity of Piezo1 channels under multiaxial stretch applied using polydimethylsiloxane (PDMS) stretch chambers and IsoStretcher technology to achieve isotropic stretching stimulation to cultured HL-1 cardiac muscle cells which express an appreciable amount of Piezo1.
Collapse
Affiliation(s)
- Yang Guo
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Cardiac Physiology and Transplantation Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia
| | - Anna-Lena Merten
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; Muscle Research Center Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Ulrike Schöler
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; Muscle Research Center Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Ze-Yan Yu
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Cardiac Physiology and Transplantation Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia
| | - Jasmina Cvetkovska
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Diane Fatkin
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia; Department of Cardiology, St Vincent's Hospital, Darlinghurst, NSW, Australia
| | - Michael P Feneley
- Cardiac Physiology and Transplantation Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia; Department of Cardiology, St Vincent's Hospital, Darlinghurst, NSW, Australia
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia.
| | - Oliver Friedrich
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; Muscle Research Center Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| |
Collapse
|
4
|
Suchyna TM. Piezo channels and GsMTx4: Two milestones in our understanding of excitatory mechanosensitive channels and their role in pathology. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:244-253. [PMID: 28778608 DOI: 10.1016/j.pbiomolbio.2017.07.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 07/17/2017] [Accepted: 07/21/2017] [Indexed: 12/19/2022]
Abstract
Discovery of Piezo channels and the reporting of their sensitivity to the inhibitor GsMTx4 were important milestones in the study of non-selective cationic mechanosensitive channels (MSCs) in normal physiology and pathogenesis. GsMTx4 had been used for years to investigate the functional role of cationic MSCs, especially in muscle tissue, but with little understanding of its target or inhibitory mechanism. The sensitivity of Piezo channels to bilayer stress and its robust mechanosensitivity when expressed in heterologous systems were keys to determining GsMTx4's mechanism of action. However, questions remain regarding Piezo's role in muscle function due to the non-selective nature of GsMTx4 inhibition toward membrane mechanoenzymes and the implication of MCS channel types by genetic knockdown. Evidence supporting Piezo like activity, at least in the developmental stages of muscle, is presented. While the MSC targets of GsMTx4 in muscle pathology are unclear, its muscle protective effects are clearly demonstrated in two recent in situ studies on normal cardiomyocytes and dystrophic skeletal muscle. The muscle protective function may be due to the combined effect of GsMTx4's inhibitory action on cationic MSCs like Piezo and TRP, and its potentiation of repolarizing K+ selective MSCs like K2P and SAKCa. Paradoxically, the potent in vitro action of GsMTx4 on many physiological functions seems to conflict with its lack of in situ side-effects on normal animal physiology. Future investigations into cytoskeletal control of sarcolemma mechanics and the suspected inclusion of MSCs in membrane micro/nano sized domains with distinct mechanical properties will aide our understanding of this dichotomy.
Collapse
Affiliation(s)
- Thomas M Suchyna
- University of Buffalo, Dept. of Physiology and Biophysics, Buffalo, NY, USA.
| |
Collapse
|
5
|
|
6
|
Bae C, Sachs F, Gottlieb PA. Protonation of the human PIEZO1 ion channel stabilizes inactivation. J Biol Chem 2015; 290:5167-5173. [PMID: 25561736 DOI: 10.1074/jbc.m114.604033] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
PIEZO1 is a recently cloned eukaryotic cation-selective channel that opens with mechanical force. We found that extracellular protonation inhibits channel activation by ≈90% by increased occupancy in the closed or the inactivated state. Titration between pH 6.3 and 8.3 exhibited a pK of ≈6.9. The steepness of the titration data suggests positive cooperativity, implying the involvement of at least two protonation sites. Whole-cell recordings yielded results similar to patches, and pH 6.5 reduced whole-cell currents by >80%. The effects were reversible. To assess whether pH acts on the open or the inactivated state, we tested a double-mutant PIEZO1 that does not inactivate. Cell-attached patches and whole-cell currents from this mutant channel were pH-insensitive. Thus, protonation appears to be associated with domain(s) of the channel involved with inactivation. pH also did not affect mutant channels with point mutations at position 2456 that are known to exhibit slow inactivation. To determine whether the physical properties of the membrane are altered by pH and thereby affect channel gating, we measured patch capacitance during mechanical stimuli at pH 6.5 and 7.3. The rate constants for changes in patch capacitance were independent of pH, suggesting that bilayer mechanics are not involved. In summary, low pH stabilizes the inactivated state. This effect may be important when channels are activated under pathological conditions in which the pH is reduced, such as during ischemia.
Collapse
Affiliation(s)
- Chilman Bae
- From the Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214
| | - Frederick Sachs
- From the Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214
| | - Philip A Gottlieb
- From the Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214.
| |
Collapse
|
7
|
Bae C, Gottlieb PA, Sachs F. Human PIEZO1: removing inactivation. Biophys J 2014; 105:880-6. [PMID: 23972840 DOI: 10.1016/j.bpj.2013.07.019] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 07/12/2013] [Accepted: 07/16/2013] [Indexed: 01/23/2023] Open
Abstract
PIEZO1 is an inactivating eukaryotic cation-selective mechanosensitive ion channel. Two sites have been located in the channel that when individually mutated lead to xerocytotic anemia by slowing inactivation. By introducing mutations at two sites, one associated with xerocytosis and the other artificial, we were able to remove inactivation. The double mutant (DhPIEZO1) has a substitution of arginine for methionine (M2225R) and lysine for arginine (R2456K). The loss of inactivation was accompanied by ∼30-mmHg shift of the activation curve to lower pressures and slower rates of deactivation. The slope sensitivity of gating was the same for wild-type and mutants, indicating that the dimensional changes between the closed and open state are unaffected by the mutations. The unitary channel conductance was unchanged by mutations, so these sites are not associated with pore. DhPIEZO1 was reversibly inhibited by the peptide GsMTx4 that acted as a gating modifier. The channel kinetics were solved using complex stimulus waveforms and the data fit to a three-state loop in detailed balance. The reaction had two pressure-dependent rates, closed to open and inactivated to closed. Pressure sensitivity of the opening rate with no sensitivity of the closing rate means that the energy barrier between them is located near the open state. Mutant cycle analysis of inactivation showed that the two sites interacted strongly, even though they are postulated to be on opposite sides of the membrane.
Collapse
Affiliation(s)
- Chilman Bae
- Department of Physiology and Biophysics, State University of New York, Buffalo, NY, USA
| | | | | |
Collapse
|
8
|
Huang H, Bae C, Sachs F, Suchyna TM. Caveolae regulation of mechanosensitive channel function in myotubes. PLoS One 2013; 8:e72894. [PMID: 24023653 PMCID: PMC3758351 DOI: 10.1371/journal.pone.0072894] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/15/2013] [Indexed: 01/07/2023] Open
Abstract
Mutations that lead to muscular dystrophy often create deficiencies in cytoskeletal support of the muscle sarcolemma causing hyperactive mechanosensitive cation channel (MSC) activity and elevated intracellular Ca(2+). Caveolae are cholesterol-rich microdomains that form mechanically deformable invaginations of the sarcolemma. Mutations to caveolin-3, the main scaffolding protein of caveolae in muscle, cause Limbe-Girdle muscular dystrophy. Using genetic and acute chemical perturbations of developing myotubes we investigated whether caveolae are functionally linked to MSCs. MSC sensitivity was assayed using suction application to patches and probe-induced indentation during whole-cell recordings. Membrane mechanical stress in patches was monitored using patch capacitance/impedance. Cholesterol depletion disrupted caveolae and caused a large increase in MSC current. It also decreased the membrane mechanical relaxation time, likely reflecting cytoskeleton dissociation from the bilayer. Reduction of Cav3 expression with miRNA also increased MSC current and decreased patch relaxation time. In contrast Cav3 overexpression produced a small decrease in MSC currents. To acutely and specifically inhibit Cav3 interactions, we made a chimeric peptide containing the antennapedia membrane translocation domain and the Cav3 scaffolding domain (A-CSD3). A-CSD3 action was time dependent initially producing a mild Ca(2+) leak and increased MSC current, while longer exposures decreased MSC currents coinciding with increased patch stiffening. Images of GFP labeled Cav3 in patches showed that Cav3 doesn't enter the pipette, showing patch composition differed from the cell surface. However, disruption via cholesterol depletion caused Cav3 to become uniformly distributed over the sarcolemma and Cav3 appearance in the patch dome. The whole-cell indentation currents elicited under the different caveolae modifying conditions mirror the patch response supporting the role of caveolae in MSC function. These studies show that normal expression levels of Cav3 are mechanoprotective to the sarcolemma through multiple mechanisms, and Cav3 upregulation observed in some dystrophies may compensate for other mechanical deficiencies.
Collapse
Affiliation(s)
- Haixia Huang
- Capital Medical University, Department of Physiology, Beijing, China
| | - Chilman Bae
- SUNY at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America
| | - Frederick Sachs
- SUNY at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America
| | - Thomas M. Suchyna
- SUNY at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America
| |
Collapse
|
9
|
Single Mechanosensitive and Ca2+-Sensitive Channel Currents Recorded from Mouse and Human Embryonic Stem Cells. J Membr Biol 2012. [DOI: 10.1007/s00232-012-9523-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
|
10
|
Urteaga P, Bou-Ali MM, Alonso de Mezquia D, Santamaría J, Santamaría C, Madariaga JA, Bataller H. Measurement of thermodiffusion coefficient of hydrocarbon binary mixtures under pressure with the thermogravitational technique. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:074903. [PMID: 22852714 DOI: 10.1063/1.4737628] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
It was designed and constructed a new thermogravitational column able to operate at high pressures (up to 50 MPa). This new thermogravitational column is of the cylindrical type with closed ends. It is made of stainless steel. The length of the column is 0.5 m and the gap between its two walls is variable. First, the column was validated at atmospheric pressure by means of measurements of the thermodiffusion coefficient of well-known binary mixtures. Then, this new thermogravitational column was used to measure the thermodiffusion coefficient of the binary mixtures 1,2,3,4-tetrahydronaphtalene/isobutylbenzene, 1,2,3,4-tetrahydronaphtalene/n-dodecane, and isobutylbenzene/n-dodecane at high pressures and within the pressure range between 0.1 and 20 MPa at a mean temperature of 25 °C. We have found a linear dependence between the thermodiffusion coefficient and the pressure.
Collapse
Affiliation(s)
- P Urteaga
- Mechanical and Manufacturing Department, Engineering Faculty, Mondragon Unibertsitatea, Loramendi 4 Apdo. 20500 Mondragon, Spain
| | | | | | | | | | | | | |
Collapse
|
11
|
Abstract
Piezo ion channels have been found to be essential for mechanical responses in cells. These channels were first shown to exist in Neuro2A cells, and the gene was identified by siRNAs that diminished the mechanical response. Piezo channels are approximately 2500 amino acids long, have between 24-32 transmembrane regions, and appear to assemble into tetramers and require no other proteins for activity. They have a reversal potential around 0 mV and show voltage dependent inactivation. The channel is constitutively active in liposomes, indicating that no cytoskeletal elements are required. Heterologous expression of the Piezo protein can create mechanical sensitivity in otherwise insensitive cells. Piezo1 currents in outside-out patches were blocked by the extracellular MSC inhibitor peptide GsMTx4. Both enantiomeric forms of GsMTx4 inhibited channel activity in a manner similar to endogenous mechanical channels. Piezo1 can adopt a tonic (non-inactivating) form with repeated stimulation. The transition to the non-inactivating form generally occurs in large groups of channels, indicating that the channels exist in domains, and once the domain is compromised, the members simultaneously adopt new properties. Piezo proteins are associated with physiological responses in cells, such as the reaction to noxious stimulus of Drosophila larvae. Recent work measuring cell crowding, shows that Piezo1 is essential for the removal of extra cells without apoptosis. Piezo1 mutations have also been linked to the pathological response of red blood cells in a genetic disease called Xerocytosis. These finding suggest that Piezo1 is a key player in cells' responses to mechanical stimuli.
Collapse
|
12
|
Gottlieb PA, Bae C, Sachs F. Gating the mechanical channel Piezo1: a comparison between whole-cell and patch recording. Channels (Austin) 2012; 6:282-9. [PMID: 22790451 PMCID: PMC3508907 DOI: 10.4161/chan.21064] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Piezo1 is a eukaryotic cation-selective mechanosensitive ion channel. To understand channel function in vivo, we first need to analyze and compare the response in the whole cell and the patch. In patches, Piezo1 inactivates and the current is fit well by a 3-state model with a single pressure-dependent rate. However, repeated stimulation led to an irreversible loss of inactivation. Remarkably, the loss of inactivation did not occur on a channel-by-channel basis but on all channels at the same time. Thus, the channels are in common mechanical domain. Divalent ions decreased the unitary conductance from ~68 pS to ~37 pS, irrespective of the cation species. Mg and Ca did not affect inactivation rates, but Zn caused a 3-fold slowing. CytochalasinD (cytoD) does not alter inactivation rates or the transition to the non-inactivating mode but does reduce the steady-state response. Whole-cell currents were similar to patch currents but also had significant differences. In contrast to the patch, cytoD inhibited the current suggesting that the activating forces were transmitted through the actin cytoskeleton. Hypotonic swelling that prestressed the cytoskeleton and the bilayer greatly increased the sensitivity of both control and cytoD cells so there are two pathways to transmit force to the channels. In contrast to patch, removing divalent ions decreased the whole-cell current. The difference between whole cell and patch properties provide new insights into our understanding of the Piezo1 gating mechanisms and cautions against generalization to in situ behavior.
Collapse
Affiliation(s)
- Philip A Gottlieb
- Center for Single Molecule Biophysics, Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA.
| | | | | |
Collapse
|
13
|
Beyder A, Strege PR, Bernard C, Farrugia G. Membrane permeable local anesthetics modulate Na(V)1.5 mechanosensitivity. Channels (Austin) 2012; 6:308-16. [PMID: 22874086 PMCID: PMC3508909 DOI: 10.4161/chan.21202] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Voltage-gated sodium selective ion channel NaV1.5 is expressed in the heart and the gastrointestinal tract, which are mechanically active organs. NaV1.5 is mechanosensitive at stimuli that gate other mechanosensitive ion channels. Local anesthetic and antiarrhythmic drugs act upon NaV1.5 to modulate activity by multiple mechanisms. This study examined whether NaV1.5 mechanosensitivity is modulated by local anesthetics. NaV1.5 channels wereexpressed in HEK-293 cells, and mechanosensitivity was tested in cell-attached and excised inside-out configurations. Using a novel protocol with paired voltage ladders and short pressure pulses, negative patch pressure (-30 mmHg) in both configurations produced a hyperpolarizing shift in the half-point of the voltage-dependence of activation (V1/2a) and inactivation (V1/2i) by about -10 mV. Lidocaine (50 µM) inhibited the pressure-induced shift of V1/2a but not V1/2i. Lidocaine inhibited the tonic increase in pressure-induced peak current in a use-dependence protocol, but it did not otherwise affect use-dependent block. The local anesthetic benzocaine, which does not show use-dependent block, also effectively blocked a pressure-induced shift in V1/2a. Lidocaine inhibited mechanosensitivity in NaV1.5 at the local anesthetic binding site mutated (F1760A). However, a membrane impermeable lidocaine analog QX-314 did not affect mechanosensitivity of F1760A NaV1.5 when applied from either side of the membrane. These data suggest that the mechanism of lidocaine inhibition of the pressure-induced shift in the half-point of voltage-dependence of activation is separate from the mechanisms of use-dependent block. Modulation of NaV1.5 mechanosensitivity by the membrane permeable local anesthetics may require hydrophobic access and may involve membrane-protein interactions.
Collapse
Affiliation(s)
- Arthur Beyder
- Division of Gastroenterology and Hepatology, Enteric Neuroscience Program, Mayo Clinic, Rochester, MN, USA
| | | | | | | |
Collapse
|
14
|
Corbitt C, Farinelli F, Brownell WE, Farrell B. Tonotopic relationships reveal the charge density varies along the lateral wall of outer hair cells. Biophys J 2012; 102:2715-24. [PMID: 22735521 DOI: 10.1016/j.bpj.2012.04.054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 04/27/2012] [Accepted: 04/30/2012] [Indexed: 01/12/2023] Open
Abstract
Outer hair cells amplify and improve the frequency selectivity of sound within the mammalian cochlea through a sound-evoked receptor potential that induces an electromechanical response in their lateral wall membrane. We experimentally show that the membrane area and linear membrane capacitance of outer hair cells increases exponentially with the electrically evoked voltage-dependent charge movement (Q(T)) and peak membrane capacitance (C(peak)). We determine the size of the different functional regions (e.g., lateral wall, synaptic basal pole) of the polarized cells from the tonotopic relationships. We then establish that Q(T) and C(peak) increase with the logarithm of the lateral wall area (A(LW)) and determine from the functions that the charge (σ(LW,) pC/μm(2)) and peak (ρ(LW,) pF/μm(2)) densities vary inversely with A(LW) (σ(LW) = 1.3/A(LW) and ρ(LW) = 9/A(LW)). This shows contrary to conventional wisdom that σ(LW) and ρ(LW) are not constant along the length of an individual outer hair cell.
Collapse
Affiliation(s)
- Christian Corbitt
- Bobby R. Alford Department of Otolaryngology-Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, USA
| | | | | | | |
Collapse
|
15
|
Bae C, Markin V, Suchyna T, Sachs F. Modeling ion channels in the gigaseal. Biophys J 2012; 101:2645-51. [PMID: 22261052 DOI: 10.1016/j.bpj.2011.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 10/26/2011] [Accepted: 11/02/2011] [Indexed: 11/30/2022] Open
Abstract
The ability to form gigaseals is essential for patch-clamp electrophysiology; however, ion channels located in the seal can produce measureable currents. To explore the expected properties of channels in the seal (i.e., rim channels), we created a mathematical model. The seal was a two-dimensional cable filled with saline and bounded on one side by membrane (with resistance and capacitance) and on the other side by glass (nonconductive and noncapacitive). We included ion depletion/accumulation around the channels. The channels were ohmic with a conductance that increased with the concentration of permeant ions. The aqueous seal thickness was set nominally to 1 nm. Imaging with fluorescent dyes in the pipette showed that the hydrophilic dye Alexa 488 is impermeant, but lipophilic FM1-43 labels the seal. The model showed that to obtain high-resistance seals, the conductivity of the seal media has to be <10% that of the bath. Stimulus voltages decreased with distance down the seal. In agreement with results in the literature, channels in the seal can produce currents similar to those in the pipette-spanning dome. The transition times of currents are slower due to membrane capacitance. If channel densities are uniform, patch currents are dominated by channels in the dome.
Collapse
Affiliation(s)
- Chilman Bae
- Department of Physiology and Biophysics, State University of New York, Buffalo, New York, USA
| | | | | | | |
Collapse
|
16
|
Fernández P, Pullarkat PA. The role of the cytoskeleton in volume regulation and beading transitions in PC12 neurites. Biophys J 2011; 99:3571-9. [PMID: 21112281 DOI: 10.1016/j.bpj.2010.10.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 10/07/2010] [Accepted: 10/08/2010] [Indexed: 10/18/2022] Open
Abstract
We present investigations on volume regulation and beading shape transitions in PC12 neurites, conducted using a flow-chamber technique. By disrupting the cell cytoskeleton with specific drugs, we investigate the role of its individual components in the volume regulation response. We find that microtubule disruption increases both swelling rate and maximum volume attained, but does not affect the ability of the neurite to recover its initial volume. In addition, investigation of axonal beading-also known as pearling instability-provides additional clues on the mechanical state of the neurite. We conclude that volume recovery is driven by passive diffusion of osmolites, and propose that the initial swelling phase is mechanically slowed down by microtubules. Our experiments provide a framework to investigate the role of cytoskeletal mechanics in volume homeostasis.
Collapse
Affiliation(s)
- Pablo Fernández
- E27 Lehrstuhl für Zellbiophysik, Technische Universität München, Garching, Germany.
| | | |
Collapse
|
17
|
Kamaraju K, Gottlieb PA, Sachs F, Sukharev S. Effects of GsMTx4 on bacterial mechanosensitive channels in inside-out patches from giant spheroplasts. Biophys J 2011; 99:2870-8. [PMID: 21044584 DOI: 10.1016/j.bpj.2010.09.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 09/07/2010] [Accepted: 09/13/2010] [Indexed: 01/13/2023] Open
Abstract
GsMTx4 is a 34-residue peptide isolated from the tarantula Grammostola spatulata folded into an inhibitory cysteine knot and it selectively affects gating of some mechanosensitive channels. Here we report the effects of cytoplasmic GsMTx4 on the two bacterial channels, MscS and MscL, in giant Escherichia coli spheroplasts. In excised inside-out patches, GsMTx4 sensitized both channels to tension by increasing the opening rate and decreasing the closing rate. With ascending and descending pressure ramps, GsMTx4 increased the gating hysteresis for MscS, a consequence of slower gating kinetics. Quantitative kinetic analysis of the primary C↔O transition showed that the hysteresis is a result of the decreased closing rate. The gating barrier location relative to the open state energy well was unaffected by GsMTx4. A reconstructed energy profile suggests that the peptide prestresses the resting state of MscS, lowering the net barrier to opening and stabilizes the open conformation by ∼8 kT. In excised patches, both MscL and MscS exhibit reversible adaptation, a process separable from inactivation for MscS. GsMTx4 decreased the rate of reversible adaptation for both channels and the MscS recovery rate from the inactivation. These measurements support a mechanism where GsMTx4 binds to the lipid interface of the channel, increasing the local stress that is sensed by the channels and stabilizing the expanded conformations.
Collapse
Affiliation(s)
- Kishore Kamaraju
- Department of Biology, University of Maryland, College Park, Maryland, USA
| | | | | | | |
Collapse
|
18
|
Maksaev G, Milac A, Anishkin A, Guy HR, Sukharev S. Analyses of gating thermodynamics and effects of deletions in the mechanosensitive channel TREK-1: comparisons with structural models. Channels (Austin) 2011; 5:34-42. [PMID: 21057213 DOI: 10.4161/chan.5.1.13906] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
TREK-1, a mechanosensitive K channel from the two-pore family (K(2)P), is involved in protective regulation of the resting potential in CNS neurons and other tissues. The structure of TREK-1 and the basis of its sensitivity to stretch and variety of lipid-soluble factors remain unknown. Using existing K channel structures as modeling templates, TREK-1 was envisioned as a two-fold symmetrical complex with the gate formed primarily by the centrally positioned TM2b helices of the second homologous repeat. Opening was modeled as a conical expansion of the barrel separating TM2b's accompanied by extension of TM2a helices with the cytoplasmic TM2a-TM1b connector. Seeking first experimental support to the models we have accomplished thermodynamic analysis of mouse TREK-1 gating and functional testing of several deletion mutants. The predicted increase of the channel in-plane area (ΔA) of ~5 nm(2) in models was supported by the experimental ΔA of ~4 nm(2) derived from the slope of open probability versus membrane tension in HEK-293T cells and their cytoskeleton-depleted blebs. In response to steps of suction, wild-type channel produced transient currents in cell-attached patches and mostly sustained currents upon patch excision. TREK-1 motifs not present in canonical K channels include divergent cytoplasmic N- and C-termini, and a characteristic 50-residue extracellular loop in the first homologous repeat. Deletion of the extracellular loop (Δ76-124) reduced the average current density in patches, increased spontaneous activity and generated a larger sub-population of high-conductance channels, while activation by tension augmented by arachidonic acid was fully retained. Further deletion of the C-terminal end (Δ76-124/Δ334-411) removed voltage dependency but otherwise produced no additional effect. In an attempt to generate a cysteine-free version of the channel, we mutated two remaining cysteines 159 and 219 in the transmembrane region. C219A did not compromise channel activity, whereas the C159A/S mutants were essentially inactive. Treatment with β-mercaptoethanol suggested that none of these cysteines form functionally-important disulfides.
Collapse
Affiliation(s)
- Grigory Maksaev
- Department of Biology, University of Maryland, College Park, USA
| | | | | | | | | |
Collapse
|
19
|
Belyy V, Kamaraju K, Akitake B, Anishkin A, Sukharev S. Adaptive behavior of bacterial mechanosensitive channels is coupled to membrane mechanics. ACTA ACUST UNITED AC 2010; 135:641-52. [PMID: 20513760 PMCID: PMC2888061 DOI: 10.1085/jgp.200910371] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mechanosensitive channel of small conductance (MscS), a tension-driven osmolyte release valve residing in the inner membrane of Escherichia coli, exhibits a complex adaptive behavior, whereas its functional counterpart, mechanosensitive channel of large conductance (MscL), was generally considered nonadaptive. In this study, we show that both channels exhibit similar adaptation in excised patches, a process that is completely separable from inactivation prominent only in MscS. When a membrane patch is held under constant pressure, adaptation of both channels is manifested as a reversible current decline. Their dose–response curves recorded with 1–10-s ramps of pressure are shifted toward higher tension relative to the curves measured with series of pulses, indicating decreased tension sensitivity. Prolonged exposure of excised patches to subthreshold tensions further shifts activation curves for both MscS and MscL toward higher tension with similar magnitude and time course. Whole spheroplast MscS recordings performed with simultaneous imaging reveal activation curves with a midpoint tension of 7.8 mN/m and the slope corresponding to ∼15-nm2 in-plane expansion. Inactivation was retained in whole spheroplast mode, but no adaptation was observed. Similarly, whole spheroplast recordings of MscL (V23T mutant) indicated no adaptation, which was present in excised patches. MscS activities tried in spheroplast-attached mode showed no adaptation when the spheroplasts were intact, but permeabilized spheroplasts showed delayed adaptation, suggesting that the presence of membrane breaks or edges causes adaptation. We interpret this in the framework of the mechanics of the bilayer couple linking adaptation of channels in excised patches to the relaxation of the inner leaflet that is not in contact with the glass pipette. Relaxation of one leaflet results in asymmetric redistribution of tension in the bilayer that is less favorable for channel opening.
Collapse
Affiliation(s)
- Vladislav Belyy
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | | | | | | | | |
Collapse
|
20
|
Hua SZ, Gottlieb PA, Heo J, Sachs F. A mechanosensitive ion channel regulating cell volume. Am J Physiol Cell Physiol 2010; 298:C1424-30. [PMID: 20457830 DOI: 10.1152/ajpcell.00503.2009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Cells respond to a hyposmotic challenge by swelling and then returning toward the resting volume, a process known as the regulatory volume decrease or RVD. The sensors for this process have been proposed to include cationic mechanosensitive ion channels that are opened by membrane tension. We tested this hypothesis using a microfluidic device to measure cell volume and the peptide GsMTx4, a specific inhibitor of cationic mechanosensitive channels. GsMTx4 had no effect on RVD in primary rat astrocytes or Madin-Darby canine kidney (MDCK) cells but was able to completely inhibit RVD and the associated Ca(2+) uptake in normal rat kidney (NRK-49F) cells in a dose-dependent manner. Gadolinium (Gd(3+)), a nonspecific blocker of many mechanosensitive channels, inhibited RVD and Ca(2+) uptake in all three cell types, demonstrating the existence of at least two types of volume sensors. Single-channel stretch-activated currents are present in outside-out patches from NRK-49F, MDCK, and astrocytes, and they are reversibly inhibited by GsMTx4. While mechanosensitive channels are involved in volume regulation, their role for volume sensing is specialized. The NRK cells form a stable platform from which to screen drugs that affect volume regulation via mechanosensory channels and as a sensitive system to clone the channel.
Collapse
Affiliation(s)
- Susan Z Hua
- Department of Physiology and Biophysics, SUNY, Buffalo, NY 14214, USA.
| | | | | | | |
Collapse
|
21
|
Abstract
Mechanosensitive ion channels (MSCs) exist in all cells, but mechanosensitivity is a phenotype not a genotype. Specialized mechanoreceptors such as the hair cells of the cochlea require elaborate mechanical impedance matching to couple the channels to the external stress. In contrast, MSCs in nonspecialized cells appear activated by stress in the bilayer local to the channel--within about three lipids. Local mechanical stress can be produced by far-field tension, amphipaths, phase separations, the cytoskeleton, the extracellular matrix, and the adhesion energy between the membrane and a patch pipette. Understanding MSC function requires under standing the stimulus.
Collapse
|
22
|
Herce HD, Garcia AE, Litt J, Kane RS, Martin P, Enrique N, Rebolledo A, Milesi V. Arginine-rich peptides destabilize the plasma membrane, consistent with a pore formation translocation mechanism of cell-penetrating peptides. Biophys J 2009; 97:1917-25. [PMID: 19804722 DOI: 10.1016/j.bpj.2009.05.066] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 05/22/2009] [Accepted: 05/29/2009] [Indexed: 10/20/2022] Open
Abstract
Recent molecular-dynamics simulations have suggested that the arginine-rich HIV Tat peptides translocate by destabilizing and inducing transient pores in phospholipid bilayers. In this pathway for peptide translocation, Arg residues play a fundamental role not only in the binding of the peptide to the surface of the membrane, but also in the destabilization and nucleation of transient pores across the bilayer. Here we present a molecular-dynamics simulation of a peptide composed of nine Args (Arg-9) that shows that this peptide follows the same translocation pathway previously found for the Tat peptide. We test experimentally the hypothesis that transient pores open by measuring ionic currents across phospholipid bilayers and cell membranes through the pores induced by Arg-9 peptides. We find that Arg-9 peptides, in the presence of an electrostatic potential gradient, induce ionic currents across planar phospholipid bilayers, as well as in cultured osteosarcoma cells and human smooth muscle cells. Our results suggest that the mechanism of action of Arg-9 peptides involves the creation of transient pores in lipid bilayers and cell membranes.
Collapse
Affiliation(s)
- H D Herce
- Department of Physics, Rensselaer Polytechnic Institute, Troy, New York, USA
| | | | | | | | | | | | | | | |
Collapse
|
23
|
Rugiero F, Drew LJ, Wood JN. Kinetic properties of mechanically activated currents in spinal sensory neurons. J Physiol 2009; 588:301-14. [PMID: 19948656 DOI: 10.1113/jphysiol.2009.182360] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Dorsal root ganglion neurons in vitro express a number of types of mechanically activated currents that are thought to underlie somatic mechanosensory transduction in vivo. We have studied the inactivation properties of these currents to assess how they might influence the electrophysiological responses of dorsal root ganglion (DRG) neurons to mechanical stimulation. We show that the speed of ramp-like mechanical stimulation determines the dynamics of mechanically activated current responses and hence the type of DRG neuron most likely to be activated. We also show that both rapidly and slowly adapting currents inactivate as a function of membrane stretch. However, the rapidly adapting current inactivation time course is mainly dependent on channel opening whilst slowly adapting current kinetics are dependent on membrane stretch. In response to repeated stimulation, slowly adapting currents inactivate less and recover more quickly than rapidly adapting currents. Therefore, vibratory stimuli tend to inactivate rapidly adapting currents whilst static stimuli tend to inactivate slowly adapting currents. Current clamp experiments show that, physiologically, the response of different types of sensory neurons is dictated primarily by the static or dynamic nature of the mechanical stimulus and the interplay between voltage-gated and mechanically gated ion channels expressed in these neurons.
Collapse
Affiliation(s)
- François Rugiero
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London, UK.
| | | | | |
Collapse
|
24
|
Suchyna TM, Markin VS, Sachs F. Biophysics and structure of the patch and the gigaseal. Biophys J 2009; 97:738-47. [PMID: 19651032 DOI: 10.1016/j.bpj.2009.05.018] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2009] [Revised: 05/02/2009] [Accepted: 05/04/2009] [Indexed: 01/13/2023] Open
Abstract
Interpreting channel behavior in patches requires an understanding of patch structure and dynamics, especially in studies of mechanosensitive channels. High resolution optical studies show that patch formation occurs via blebbing that disrupts normal membrane structure and redistributes in situ components including ion channels. There is a 1-2 microm region of the seal below the patch where proteins are excluded and this may consist of extracted lipids that form the gigaseal. Patch domes often have complex geometries with inhomogeneous stresses due to the membrane-glass adhesion energy (E(a)), cytoskeletal forces, and possible lipid subdomains. The resting tension in the patch dome ranges from 1-4 mN/m, a significant fraction of the lytic tension of a bilayer ( approximately 10 mN/m). Thus, all patch experiments are conducted under substantial, and uneven, resting tension that may alter the kinetics of many channels. E(a) seems dominated by van der Waals attraction overlaid with a normally repulsive Coulombic force. High ionic strength pipette saline increased E(a) and, surprisingly, increased cytoskeletal rigidity in cell-attached patches. Low pH pipette saline also increased E(a) and reduced the seal selectivity for cations, presumably by neutralizing the membrane surface charge. The seal is a negatively charged, cation selective, space with a resistance of approximately 7 gigohm/microm in 100 mM KCl, and the high resistivity of the space may result from the presence of high viscosity glycoproteins. Patches creep up the pipette over time with voltage independent and voltage dependent components. Voltage-independent creep is expected from the capillary attraction of E(a) and the flow of fresh lipids from the cell. Voltage-dependent creep seems to arise from electroosmosis in the seal. Neutralization of negative charges on the seal membrane with low pH decreased the creep rate and reversed the direction of creep at positive pipette potentials.
Collapse
Affiliation(s)
- Thomas M Suchyna
- State University of New York at Buffalo, Department of Physiology and Biophysics, Buffalo, New York 14214, USA.
| | | | | |
Collapse
|
25
|
Huang H, Wei H, Liu P, Wang W, Sachs F, Niu W. A simple automated stimulator of mechanically induced arrhythmias in the isolated rat heart. Exp Physiol 2009; 94:1054-61. [PMID: 19592413 DOI: 10.1113/expphysiol.2009.048660] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Transient stretching of the ventricle can trigger arrhythmias and evoke ventricular fibrillation, especially when the stimulation occurs in the vulnerable period. To explore the sensitivity of small hearts we used a commercial pressure servo to study the kinetic relationship of left ventricular pressure to excitability and arrhythmias in the rat heart. Stimulation protocols were readily composed on the computer and programmed to vary the stimulus amplitude and timing relative to pacing. The pressure-induced premature ventricular excitations were similar to those observed in larger hearts, but the convenience of using small hearts allows the use of inexpensive transgenic animals to explore the molecular basis of transduction.
Collapse
Affiliation(s)
- Haixia Huang
- Department of Physiology and Pathophysiology, Capital Medical University, Beijing 100069, People's Republic of China
| | | | | | | | | | | |
Collapse
|
26
|
Kockskämper J, von Lewinski D, Khafaga M, Elgner A, Grimm M, Eschenhagen T, Gottlieb PA, Sachs F, Pieske B. The slow force response to stretch in atrial and ventricular myocardium from human heart: functional relevance and subcellular mechanisms. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:250-67. [PMID: 18466959 DOI: 10.1016/j.pbiomolbio.2008.02.026] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Mechanical load is an important regulator of cardiac force. Stretching human atrial and ventricular trabeculae elicited a biphasic force increase: an immediate increase (Frank-Starling mechanism) followed by a further slow increase (slow force response, SFR). In ventricle, the SFR was unaffected by AT- and ET-receptor antagonism, by inhibition of protein-kinase-C, PI-3-kinase, and NO-synthase, but attenuated by inhibition of Na+/H+- (NHE) and Na+/Ca2+ exchange (NCX). In atrium, however, neither NHE- nor NCX-inhibition affected the SFR. Stretch elicited a large NHE-dependent [Na+]i increase in ventricle but only a small, NHE-independent [Na+]i increase in atrium. Stretch-activated non-selective cation channels contributed to basal force development in atrium but not ventricle and were not involved in the SFR in either tissue. Interestingly, inhibition of AT receptors or pre-application of angiotensin II or endothelin-1 reduced the atrial SFR. Furthermore, stretch increased phosphorylation of atrial myosin light chain 2 (MLC2) and inhibition of myosin light chain kinase (MLCK) attenuated the SFR in atrium and ventricle. Thus, in human heart both atrial and ventricular myocardium exhibit a stretch-dependent SFR that might serve to adjust cardiac output to increased workload. In ventricle, there is a robust NHE-dependent (but angiotensin II- and endothelin-1-independent) [Na+]i increase that is translated into a [Ca2+]i and force increase via NCX. In atrium, on the other hand, there is an angiotensin II- and endothelin-dependent (but NHE- and NCX-independent) force increase. Increased myofilament Ca2+ sensitivity through MLCK-induced phosphorylation of MLC2 is a novel mechanism contributing to the SFR in both atrium and ventricle.
Collapse
Affiliation(s)
- Jens Kockskämper
- Department of Cardiology, Medical University of Graz, Auenbruggerplatz 15, Graz, Austria
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Porto BN, Alves LS, Fernández PL, Dutra TP, Figueiredo RT, Graça-Souza AV, Bozza MT. Heme induces neutrophil migration and reactive oxygen species generation through signaling pathways characteristic of chemotactic receptors. J Biol Chem 2007; 282:24430-6. [PMID: 17581818 DOI: 10.1074/jbc.m703570200] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hemolysis or extensive cell damage can lead to high concentrations of free heme, causing oxidative stress and inflammation. Considering that heme induces neutrophil chemotaxis, we hypothesize that heme activates a G protein-coupled receptor. Here we show that similar to heme, several heme analogs were able to induce neutrophil migration in vitro and in vivo. Mesoporphyrins, molecules lacking the vinyl groups in their rings, were not chemotactic for neutrophils and selectively inhibited heme-induced migration. Moreover, migration of neutrophils induced by heme was abolished by pretreatment with pertussis toxin, an inhibitor of Galpha inhibitory protein, and with inhibitors of phosphoinositide 3-kinase, phospholipase Cbeta, mitogen-activated protein kinases, or Rho kinase. The induction of reactive oxygen species by heme was dependent of Galpha inhibitory protein and phosphoinositide 3-kinase and partially dependent of phospholipase Cbeta, protein kinase C, mitogen-activated protein kinases, and Rho kinase. Together, our results indicate that heme activates neutrophils through signaling pathways that are characteristic of chemoattractant molecules and suggest that mesoporphyrins might prove valuable in the treatment of the inflammatory consequences of hemorrhagic and hemolytic disorders.
Collapse
Affiliation(s)
- Bárbara N Porto
- Departamento de Imunologia, Instituto de Microbiologia, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, 21.941-590 Brasil
| | | | | | | | | | | | | |
Collapse
|
28
|
Gottlieb PA, Suchyna TM, Sachs F. Properties and Mechanism of the Mechanosensitive Ion Channel Inhibitor GsMTx4, a Therapeutic Peptide Derived from Tarantula Venom. CURRENT TOPICS IN MEMBRANES 2007; 59:81-109. [PMID: 25168134 DOI: 10.1016/s1063-5823(06)59004-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Mechanosensitive ion channels (MSCs) are found in all types of cells ranging from Escherichia coli to morning glories to humans. They seem to fall into two families: those in specialized receptors, such as the hair cells of the cochlea, and those in cells not clearly differentiated for sensory duty. The physiological function of the channels in nonspecialized cells has not been demonstrated, although their activity has been demonstrated innumerable times in vitro. The only specific reagent to block MSCs isGsMTx4, a 4-kDa peptide isolated from tarantula venom. Despite being isolated from venom, it is nontoxic to mice. GsMTx4 is specific for an MSC subtype, the nonselective cation channels that may be members of the transient receptor potential (TRP) family. GsMTx4 acts as a gating modifier, increasing the energy of the open state relative to the closed state. The mirror image D enantiomer of GsMTx4 is equally active, so mode of action is not via the traditional lock and key model. GsMTx4 probably acts in the boundary lipid of the channel by changing local curvature and mechanically stressing the channel toward the closed state. Despite the lack of definitive physiological data on the function of the cationic MSCs, GsMTx4 may prove useful as a drug or lead compound that can affect physiological processes. These processes would be those driven by mechanical stress, such as blood vessel autoregulation, stress-induced contraction of smooth muscle, and Ca(2+) loading in muscular dystrophy.
Collapse
Affiliation(s)
- Philip A Gottlieb
- The Department of Physiology and Biophysics, Center for Single Molecule Biophysics, SUNY at Buffalo, Buffalo, New York 14214
| | - Thomas M Suchyna
- The Department of Physiology and Biophysics, Center for Single Molecule Biophysics, SUNY at Buffalo, Buffalo, New York 14214
| | - Frederick Sachs
- The Department of Physiology and Biophysics, Center for Single Molecule Biophysics, SUNY at Buffalo, Buffalo, New York 14214
| |
Collapse
|
29
|
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.
Collapse
Affiliation(s)
- Charles L Bowman
- Center for Single Molecule Biophysics and The Department of Physiology and Biophysics, SUNY at Buffalo, Buffalo, NY 14214, USA.
| | | | | | | | | |
Collapse
|
30
|
Suchyna TM, Sachs F. Mechanosensitive channel properties and membrane mechanics in mouse dystrophic myotubes. J Physiol 2007; 581:369-87. [PMID: 17255168 PMCID: PMC2075208 DOI: 10.1113/jphysiol.2006.125021] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Muscular dystrophy is associated with increased activity of mechanosensitive channels (MSCs) and increased cell calcium levels. MSCs in patches from mdx mouse myotubes have higher levels of resting activity, compared to patches from wild-type mice, and a pronounced latency of activation and deactivation. Measurements of patch capacitance and geometry reveal that the differences are linked to cortical membrane mechanics rather than to differences in channel gating. We found unexpectedly that patches from mdx mice are strongly curved towards the pipette tip by actin pulling normal to the membrane. This force produces a substantial tension (approximately 5 mN m(-1)) that can activate MSCs in the absence of overt stimulation. The inward curvature of patches from mdx mice is eliminated by actin inhibitors. Applying moderate suction to the pipette flattens the membrane, reducing tension, and making the response appear to be stretch inactivated. The pronounced latency to activation in patches from mdx mice is caused by the mechanical relaxation time required to reorganize the cortex from inward to outward curvature. The increased latency is equivalent to a three-fold increase in cortical viscosity. Disruption of the cytoskeleton by chemical or mechanical means eliminates the differences in kinetics and curvature between patches from wild-type and mdx mice. The stretch-induced increase in specific capacitance of the patch, approximately 80 fF microm(-2), far exceeds the specific capacitance of bilayers, suggesting the presence of stress-sensitive access to large pools of membrane, possibly caveoli, T-tubules or portions of the gigaseal. In mdx mouse cells the intrinsic gating property of fast voltage-sensitive inactivation is lost. It is robust in wild-type mouse cells (observed in 50% of outside-out patches), but never observed in mdx cells. This link between dystrophin and inactivation may lead to increased background cation currents and Ca2+ influx. Spontaneous Ca2+ transients in mdx mouse cells are sensitive to depolarization and are inhibited by the specific MSC inhibitor GsMTx4, in both the D and L forms.
Collapse
Affiliation(s)
- Thomas M Suchyna
- Department of Physiology and Biophysics, Center for Single Molecule Biophysics, State University New York (SUNY) at Buffalo, Buffalo, NY 14214, USA.
| | | |
Collapse
|
31
|
|
32
|
Pickard BG. Delivering Force and Amplifying Signals in Plant Mechanosensing. MECHANOSENSITIVE ION CHANNELS, PART A 2007. [DOI: 10.1016/s1063-5823(06)58014-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
33
|
Hamill OP. Twenty odd years of stretch-sensitive channels. Pflugers Arch 2006; 453:333-51. [PMID: 17021800 DOI: 10.1007/s00424-006-0131-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 06/27/2006] [Indexed: 01/15/2023]
Abstract
After formation of the giga-seal, the membrane patch can be stimulated by hydrostatic or osmotic pressure gradients applied across the patch. This feature led to the discovery of stretch-sensitive or mechanosensitive (MS) channels, which are now known to be ubiquitously expressed in cells representative of all the living kingdoms. In addition to mechanosensation, MS channels have been implicated in many basic cell functions, including regulation of cell volume, shape, and motility. The successful cloning, overexpression, and crystallization of bacterial MS channel proteins combined with patch clamp and modeling studies have provided atomic insight into the working of these nanomachines. In particular, studies of MS channels have revealed new understanding of how the lipid bilayer modulates membrane protein function. Three major membrane protein families, transient receptor potential, 2 pore domain K(+), and the epithelial Na(+) channels, have been shown to form MS channels in animal cells, and their polymodal activation embrace fields far beyond mechanosensitivity. The discovery of new drugs highly selective for MS channels ("mechanopharmaceutics") and the demonstration of MS channel involvement in several major human diseases ("mechanochannelopathies") provide added motivation for devising new techniques and approaches for studying MS channels.
Collapse
Affiliation(s)
- O P Hamill
- Neurosciences and Cell Biology, UTMB, Galveston, TX, 77555, USA.
| |
Collapse
|
34
|
Petrov AG. Electricity and mechanics of biomembrane systems: Flexoelectricity in living membranes. Anal Chim Acta 2006; 568:70-83. [PMID: 17761248 DOI: 10.1016/j.aca.2006.01.108] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Revised: 01/25/2006] [Accepted: 01/28/2006] [Indexed: 11/18/2022]
Abstract
Flexoelectricity provides a reciprocal relationship between electricity and mechanics in membranes, i.e., between membrane curvature and polarization. Experimental evidence of biomembrane flexoelectricity (including direct and converse flexoelectric effect) is reviewed. Biological implications of flexoelectricity in membrane transport, membrane contact, mechanosensitivity, electromotility and hearing are underlined. Flexoelectricity enables membrane structures to function like soft micro- and nano-machines, sensors and actuators, thus providing important input to molecular electronics applications.
Collapse
Affiliation(s)
- Alexander G Petrov
- Biomolecular Layers Department, Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria.
| |
Collapse
|
35
|
Honoré E, Patel AJ, Chemin J, Suchyna T, Sachs F. Desensitization of mechano-gated K2P channels. Proc Natl Acad Sci U S A 2006; 103:6859-64. [PMID: 16636285 PMCID: PMC1458984 DOI: 10.1073/pnas.0600463103] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The neuronal mechano-gated K2P channels TREK-1 and TRAAK show pronounced desensitization within 100 ms of membrane stretch. Desensitization persists in the presence of cytoskeleton disrupting agents, upon patch excision, and when channels are expressed in membrane blebs. Mechanosensitive currents evoked with a variety of complex stimulus protocols were globally fit to a four-state cyclic kinetic model in detailed balance, without the need to introduce adaptation of the stimulus. However, we show that patch stress can be a complex function of time and stimulation history. The kinetic model couples desensitization to activation, so that gentle conditioning stimuli do not cause desensitization. Prestressing the channels with pressure, amphipaths, intracellular acidosis, or the E306A mutation reduces the peak-to-steady-state ratio by changing the preexponential terms of the rate constants, increasing the steady-state current amplitude. The mechanical responsivity can be accounted for by a change of in-plane area of approximately 2 nm2 between the closed and open conformations. Desensitization and its regulation by chemical messengers is predicted to condition the physiological role of K2P channels.
Collapse
Affiliation(s)
- Eric Honoré
- *Institut de Pharmacologie Moléculaire et Cellulaire, Unité Mixte de Recherche 6097, Centre National de la Recherche Scientifique, 660 Route des Lucioles, 06560 Valbonne, France; and
- To whom correspondence may be addressed. E-mail:
or
| | - Amanda Jane Patel
- *Institut de Pharmacologie Moléculaire et Cellulaire, Unité Mixte de Recherche 6097, Centre National de la Recherche Scientifique, 660 Route des Lucioles, 06560 Valbonne, France; and
| | - Jean Chemin
- L’Institut de Génétique Humaine, Unité Propre de Recherche 1142, Centre National de la Recherche Scientifique, 141 Rue de la Cardonille, 34396 Montpellier Cedex 5, France
| | - Thomas Suchyna
- Single Molecule Biophysics, 301 Cary Hall, University at Buffalo, State University of New York, Buffalo, NY 14214
| | - Frederick Sachs
- Single Molecule Biophysics, 301 Cary Hall, University at Buffalo, State University of New York, Buffalo, NY 14214
- To whom correspondence may be addressed. E-mail:
or
| |
Collapse
|
36
|
Morris CE, Juranka PF, Lin W, Morris TJ, Laitko U. Studying the mechanosensitivity of voltage-gated channels using oocyte patches. Methods Mol Biol 2006; 322:315-29. [PMID: 16739733 DOI: 10.1007/978-1-59745-000-3_22] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The mechanosensitivity of voltage-gated (VG) channels is of biophysical, physiological. and pathophysiological interest. Xenopus oocytes offer a critical advantage for investigating the electrophysiology of recombinant VG channels subjected to membrane stretch, namely, the ability to monitor macroscopic current from membrane patches. High-density channel expression in oocytes makes for macroscopic current in conventional-size, mechanically sturdy patches. With the patch configuration, precisely the same membrane that is voltage-clamped is the membrane subjected to on-off stretch stimuli. With patches, meaningful stretch dose responses are possible. Experimental design should facilitate within-patch comparisons wherever possible. The mechanoresponses of some VG channels depend critically on patch history. Methods for minimizing and coping with interference from endogenous voltage-dependent and stretch-activated endogenous channels are described.
Collapse
|
37
|
Staruschenko A, Negulyaev YA, Morachevskaya EA. Actin cytoskeleton disassembly affects conductive properties of stretch-activated cation channels in leukaemia cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1669:53-60. [PMID: 15842999 DOI: 10.1016/j.bbamem.2005.02.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2004] [Revised: 02/08/2005] [Accepted: 02/24/2005] [Indexed: 11/23/2022]
Abstract
Mechanosensitive channels in various eucaryotic cells are thought to be functionally and structurally coupled to the cortical cytoskeleton. However, the results of electrophysiological studies are rather controversial and the functional impact of cytoskeleton assembly-disassembly on stretch-activated channel properties remains unclear. Here, the possible involvement of cytoskeletal elements in the regulation of stretch-activated Ca2+-permeable channels was studied in human leukaemia K562 cells with the use of agents that selectively modify the actin or tubulin system. F-actin disassembly resulted in a considerable reduction of the amplitude of stretch-activated currents without significant change in channel open probability. The effects of treatments with cytochalasins or latrunculin were principally similar, developed gradually and consisted a strong decrease of single channel conductance. Microtubule disruption did not affect stretch-activated channels. The data presented here are in principal agreement with the general conclusion that mechanosensitive channel functions are largely dependent on the integrity of the cortical actin cytoskeleton. Specifically, changes in conductive properties of the pore may provide an essential mechanism of channel regulation underlying functional modulation of membrane currents. Our results allow one to speculate that microfilament organization may be an important determinant in modulating biophysical characteristics of stretch-activated cation channels in cells of blood origin.
Collapse
|
38
|
Abstract
Connexins form gap junction channels that provide a hydrophilic path between cell interiors. Some connexins, particularly the lens connexins, Cx46 and Cx50 and their orthologs, can form functional hemichannels in nonjunctional membranes. These hemichannels are a nonselective conduit to the extracellular medium and may jeopardize cell survival. The physiological function of hemichannels has remained elusive, but it has been postulated that hemichannels are involved in ATP-release caused by mechanical stimulation. Here we show with single-channel and whole cell electrophysiological studies that Cx46 hemichannels are mechanosensitive, like other families of ion channels and membrane-bound enzymes. The hemichannel response to mechanical stress is bipolar. At negative potentials stress opens the channel, and at positive potentials stress closes it. Physiologically, Cx46 hemichannels may assist accommodation of the ocular lens by providing a transient path for volume flow as the lens changes shape.
Collapse
Affiliation(s)
- Li Bao
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136, USA
| | | | | |
Collapse
|
39
|
Suchyna TM, Tape SE, Koeppe RE, Andersen OS, Sachs F, Gottlieb PA. Bilayer-dependent inhibition of mechanosensitive channels by neuroactive peptide enantiomers. Nature 2004; 430:235-40. [PMID: 15241420 DOI: 10.1038/nature02743] [Citation(s) in RCA: 233] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2004] [Accepted: 06/03/2004] [Indexed: 01/17/2023]
Abstract
The peptide GsMTx4, isolated from the venom of the tarantula Grammostola spatulata, is a selective inhibitor of stretch-activated cation channels (SACs). The mechanism of inhibition remains unknown; but both GsMTx4 and its enantiomer, enGsMTx4, modify the gating of SACs, thus violating a trademark of the traditional lock-and-key model of ligand-protein interactions. Suspecting a bilayer-dependent mechanism, we examined the effect of GsMTx4 and enGsMTx4 on gramicidin A (gA) channel gating. Both peptides are active, and the effect increases with the degree of hydrophobic mismatch between bilayer thickness and channel length, meaning that GsMTx4 decreases the energy required to deform the boundary lipids adjacent to the channel. GsMTx4 decreases inward SAC single-channel currents but has no effect on outward currents, suggesting it is located within a Debye length of the outer vestibule of the SACs, but significantly farther from the inner vestibule. Likewise, GsMTx4 decreases gA single-channel currents. Our results suggest that modulation of membrane proteins by amphipathic peptides--mechanopharmacology--involves not only the protein itself but also the surrounding lipids. The surprising efficacy of the d form of GsMTx4 peptide has important therapeutic implications, because d peptides are not hydrolysed by endogenous proteases and may be administered orally.
Collapse
Affiliation(s)
- Thomas M Suchyna
- Department of Physiology and Biophysics, SUNY at Buffalo, Buffalo, New York 14214, USA
| | | | | | | | | | | |
Collapse
|