1
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Lin H, Li J, Zhang Q, Yang H, Chen S. C-type inactivation and proton modulation mechanisms of the TASK3 channel. Proc Natl Acad Sci U S A 2024; 121:e2320345121. [PMID: 38630723 PMCID: PMC11046659 DOI: 10.1073/pnas.2320345121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 03/19/2024] [Indexed: 04/19/2024] Open
Abstract
The TWIK-related acid-sensitive K+ channel 3 (TASK3) belongs to the two-pore domain (K2P) potassium channel family, which regulates cell excitability by mediating a constitutive "leak" potassium efflux in the nervous system. Extracellular acidification inhibits TASK3 channel, but the molecular mechanism by which channel inactivation is coupled to pH decrease remains unclear. Here, we report the cryo-electron microscopy structures of human TASK3 at neutral and acidic pH. Structural comparison revealed selectivity filter (SF) rearrangements upon acidification, characteristic of C-type inactivation, but with a unique structural basis. The extracellular mouth of the SF was prominently dilated and simultaneously blocked by a hydrophobic gate. His98 protonation shifted the conformational equilibrium between the conductive and C-type inactivated SF toward the latter by engaging a cation-π interaction with Trp78, consistent with molecular dynamics simulations and electrophysiological experiments. Our work illustrated how TASK3 is gated in response to extracellular pH change and implies how physiological stimuli might directly modulate the C-type gating of K2P channels.
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Affiliation(s)
- Huajian Lin
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai200125, China
| | - Junnan Li
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Qiansen Zhang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Shanshuang Chen
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai200125, China
- Department of Otolaryngology-Head and Neck Surgery, Ninth People’s Hospital, Shanghai200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai200125, China
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2
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Sorum B, Docter T, Panico V, Rietmeijer RA, Brohawn SG. Tension activation of mechanosensitive two-pore domain K+ channels TRAAK, TREK-1, and TREK-2. Nat Commun 2024; 15:3142. [PMID: 38605031 PMCID: PMC11009253 DOI: 10.1038/s41467-024-47208-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 03/22/2024] [Indexed: 04/13/2024] Open
Abstract
TRAAK, TREK-1, and TREK-2 are mechanosensitive two-pore domain K+ (K2P) channels that contribute to action potential propagation, sensory transduction, and muscle contraction. While structural and functional studies have led to models that explain their mechanosensitivity, we lack a quantitative understanding of channel activation by membrane tension. Here, we define the tension response of mechanosensitive K2Ps using patch-clamp recording and imaging. All are low-threshold mechanosensitive channels (T10%/50% 0.6-2.7 / 4.4-6.4 mN/m) with distinct response profiles. TRAAK is most sensitive, TREK-1 intermediate, and TREK-2 least sensitive. TRAAK and TREK-1 are activated broadly over a range encompassing nearly all physiologically relevant tensions. TREK-2, in contrast, activates over a narrower range like mechanosensitive channels Piezo1, MscS, and MscL. We further show that low-frequency, low-intensity focused ultrasound increases membrane tension to activate TRAAK and MscS. This work provides insight into tension gating of mechanosensitive K2Ps relevant to understanding their physiological roles and potential applications for ultrasonic neuromodulation.
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Affiliation(s)
- Ben Sorum
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, 08103, USA
| | - Trevor Docter
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
| | - Vincent Panico
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
| | - Robert A Rietmeijer
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
| | - Stephen G Brohawn
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA.
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA.
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3
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Fok A, Brissette B, Hallacy T, Ahamed H, Ho E, Ramanathan S, Ringstad N. High-fidelity encoding of mechanostimuli by tactile food-sensing neurons requires an ensemble of ion channels. Cell Rep 2023; 42:112452. [PMID: 37119137 DOI: 10.1016/j.celrep.2023.112452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 02/07/2023] [Accepted: 04/14/2023] [Indexed: 04/30/2023] Open
Abstract
The nematode C. elegans uses mechanosensitive neurons to detect bacteria, which are food for worms. These neurons release dopamine to suppress foraging and promote dwelling. Through a screen of genes highly expressed in dopaminergic food-sensing neurons, we identify a K2P-family potassium channel-TWK-2-that damps their activity. Strikingly, loss of TWK-2 restores mechanosensation to neurons lacking the NOMPC-like channel transient receptor potential 4 (TRP-4), which was thought to be the primary mechanoreceptor for tactile food sensing. The alternate mechanoreceptor mechanism uncovered by TWK-2 mutation requires three Deg/ENaC channel subunits: ASIC-1, DEL-3, and UNC-8. Analysis of cell-physiological responses to mechanostimuli indicates that TRP and Deg/ENaC channels work together to set the range of analog encoding of stimulus intensity and to improve signal-to-noise characteristics and temporal fidelity of food-sensing neurons. We conclude that a specialized mechanosensory modality-tactile food sensing-emerges from coordination of distinct force-sensing mechanisms housed in one type of sensory neuron.
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Affiliation(s)
- Alice Fok
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, and Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
| | - Benjamin Brissette
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, and Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
| | - Tim Hallacy
- Harvard University, Departments of Molecular and Cell Biology, Stem Cell and Regenerative Biology and Applied Physics, Cambridge, MA 10238, USA
| | - Hassan Ahamed
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, and Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
| | - Elver Ho
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, and Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
| | - Sharad Ramanathan
- Harvard University, Departments of Molecular and Cell Biology, Stem Cell and Regenerative Biology and Applied Physics, Cambridge, MA 10238, USA
| | - Niels Ringstad
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, and Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA.
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4
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Schmidpeter PAM, Petroff JT, Khajoueinejad L, Wague A, Frankfater C, Cheng WWL, Nimigean CM, Riegelhaupt PM. Membrane phospholipids control gating of the mechanosensitive potassium leak channel TREK1. Nat Commun 2023; 14:1077. [PMID: 36841877 PMCID: PMC9968290 DOI: 10.1038/s41467-023-36765-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 02/15/2023] [Indexed: 02/27/2023] Open
Abstract
Tandem pore domain (K2P) potassium channels modulate resting membrane potentials and shape cellular excitability. For the mechanosensitive subfamily of K2Ps, the composition of phospholipids within the bilayer strongly influences channel activity. To examine the molecular details of K2P lipid modulation, we solved cryo-EM structures of the TREK1 K2P channel bound to either the anionic lipid phosphatidic acid (PA) or the zwitterionic lipid phosphatidylethanolamine (PE). At the extracellular face of TREK1, a PA lipid inserts its hydrocarbon tail into a pocket behind the selectivity filter, causing a structural rearrangement that recapitulates mutations and pharmacology known to activate TREK1. At the cytoplasmic face, PA and PE lipids compete to modulate the conformation of the TREK1 TM4 gating helix. Our findings demonstrate two distinct pathways by which anionic lipids enhance TREK1 activity and provide a framework for a model that integrates lipid gating with the effects of other mechanosensitive K2P modulators.
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Affiliation(s)
| | - John T Petroff
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Leila Khajoueinejad
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Aboubacar Wague
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Cheryl Frankfater
- Department of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Wayland W L Cheng
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
- Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA
| | - Paul M Riegelhaupt
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA.
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5
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Young MN, Sindoni MJ, Lewis AH, Zauscher S, Grandl J. The energetics of rapid cellular mechanotransduction. Proc Natl Acad Sci U S A 2023; 120:e2215747120. [PMID: 36795747 PMCID: PMC9974467 DOI: 10.1073/pnas.2215747120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 01/18/2023] [Indexed: 02/17/2023] Open
Abstract
Cells throughout the human body detect mechanical forces. While it is known that the rapid (millisecond) detection of mechanical forces is mediated by force-gated ion channels, a detailed quantitative understanding of cells as sensors of mechanical energy is still lacking. Here, we combine atomic force microscopy with patch-clamp electrophysiology to determine the physical limits of cells expressing the force-gated ion channels (FGICs) Piezo1, Piezo2, TREK1, and TRAAK. We find that, depending on the ion channel expressed, cells can function either as proportional or nonlinear transducers of mechanical energy and detect mechanical energies as little as ~100 fJ, with a resolution of up to ~1 fJ. These specific energetic values depend on cell size, channel density, and cytoskeletal architecture. We also make the surprising discovery that cells can transduce forces either nearly instantaneously (<1 ms) or with a substantial time delay (~10 ms). Using a chimeric experimental approach and simulations, we show how such delays can emerge from channel-intrinsic properties and the slow diffusion of tension in the membrane. Overall, our experiments reveal the capabilities and limits of cellular mechanosensing and provide insights into molecular mechanisms that different cell types may employ to specialize for their distinct physiological roles.
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Affiliation(s)
- Michael N. Young
- Department of Neurobiology, Duke University Medical Center, Durham, NC27710
| | - Michael J. Sindoni
- Department of Neurobiology, Duke University Medical Center, Durham, NC27710
| | - Amanda H. Lewis
- Department of Neurobiology, Duke University Medical Center, Durham, NC27710
| | - Stefan Zauscher
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC27710
| | - Jörg Grandl
- Department of Neurobiology, Duke University Medical Center, Durham, NC27710
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6
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Sorum B, Docter T, Panico V, Rietmeijer RA, Brohawn SG. Pressure and ultrasound activate mechanosensitive TRAAK K + channels through increased membrane tension. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.11.523644. [PMID: 36712118 PMCID: PMC9882092 DOI: 10.1101/2023.01.11.523644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
TRAAK is a mechanosensitive two-pore domain K + (K2P) channel found in nodes of Ranvier within myelinated axons. It displays low leak activity at rest and is activated up to one hundred-fold by increased membrane tension. Structural and functional studies have led to physical models for channel gating and mechanosensitivity, but no quantitative analysis of channel activation by tension has been reported. Here, we use simultaneous patch-clamp recording and fluorescent imaging to determine the tension response characteristics of TRAAK. TRAAK shows high sensitivity and a broad response to tension spanning nearly the entire physiologically relevant tension range. This graded response profile distinguishes TRAAK from similarly low-threshold mechanosensitive channels Piezo1 and MscS, which activate in a step-like fashion over a narrow tension range. We further use patch imaging to show that ultrasonic activation of TRAAK and MscS is due to increased membrane tension. Together, these results provide mechanistic insight into TRAAK tension gating, a framework for exploring the role of mechanosensitive K + channels at nodes of Ranvier, and biophysical context for developing ultrasound as a mechanical stimulation technique for neuromodulation.
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Affiliation(s)
- Ben Sorum
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, California 94720, USA.,Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA
| | - Trevor Docter
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, California 94720, USA.,Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA
| | - Vincent Panico
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, California 94720, USA.,Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA
| | - Robert A. Rietmeijer
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, California 94720, USA.,Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA
| | - Stephen G. Brohawn
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, California 94720, USA.,Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA.,Correspondence:
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7
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Turney TS, Li V, Brohawn SG. Structural Basis for pH-gating of the K + channel TWIK1 at the selectivity filter. Nat Commun 2022; 13:3232. [PMID: 35680900 PMCID: PMC9184524 DOI: 10.1038/s41467-022-30853-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 05/20/2022] [Indexed: 11/11/2022] Open
Abstract
TWIK1 (K2P1.1, KCNK1) is a widely expressed pH-gated two-pore domain K+ channel (K2P) that contributes to cardiac rhythm generation and insulin release from pancreatic beta cells. TWIK1 displays unique properties among K2Ps including low basal activity and inhibition by extracellular protons through incompletely understood mechanisms. Here, we present cryo-EM structures of TWIK1 in lipid nanodiscs at high and low pH that reveal a previously undescribed gating mechanism at the K+ selectivity filter. At high pH, TWIK1 adopts an open conformation. At low pH, protonation of an extracellular histidine results in a cascade of conformational changes that close the channel by sealing the top of the selectivity filter, displacing the helical cap to block extracellular ion access pathways, and opening gaps for lipid block of the intracellular cavity. These data provide a mechanistic understanding for extracellular pH-gating of TWIK1 and illustrate how diverse mechanisms have evolved to gate the selectivity filter of K+ channels.
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Affiliation(s)
- Toby S Turney
- Biophysics Graduate Program, University of California Berkeley, Berkeley, CA, 94720, USA
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California Berkeley, Berkeley, CA, 94720, USA
| | - Vivian Li
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California Berkeley, Berkeley, CA, 94720, USA
| | - Stephen G Brohawn
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA.
- California Institute for Quantitative Biosciences (QB3), University of California Berkeley, Berkeley, CA, 94720, USA.
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8
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Panasawatwong A, Pipatpolkai T, Tucker SJ. Transition between conformational states of the TREK-1 K2P channel promoted by interaction with PIP 2. Biophys J 2022; 121:2380-2388. [PMID: 35596528 DOI: 10.1016/j.bpj.2022.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/02/2022] [Accepted: 05/16/2022] [Indexed: 11/02/2022] Open
Abstract
Members of the TREK family of two-pore domain (K2P) potassium channels are highly sensitive to regulation by membrane lipids, including phosphatidylinositol-4,5-bisphosphate (PIP2). Previous studies have demonstrated that PIP2 increases TREK1 channel activity, however, the mechanistic understanding of the conformational transitions induced by PIP2 remain unclear. Here, we used coarse-grained molecular dynamics (CG-MD) and atomistic MD simulations to model the PIP2 binding site on both the up and down state conformations of TREK-1. We also calculated the free energy of PIP2 binding relative to other anionic phospholipids in both conformational states using potential of mean force (PMF) and free energy perturbation (FEP) calculations. Our results identify state-dependent binding of PIP2 to sites involving the proximal C-terminus and we show that PIP2 promotes a conformational transition from a down state towards an intermediate that resembles the up state. These results are consistent with functional data for PIP2 regulation and together provide evidence for a structural mechanism of TREK-1 channel activation by phosphoinositides.
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Affiliation(s)
| | - Tanadet Pipatpolkai
- Department of Physiology Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, U.K.; Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, U.K.; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, U.K..
| | - Stephen J Tucker
- Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, U.K.; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, U.K.; Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, U.K..
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