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Boateng D, Li X, Zhu Y, Zhang H, Wu M, Liu J, Kang Y, Zeng H, Han L. Recent advances in flexible hydrogel sensors: Enhancing data processing and machine learning for intelligent perception. Biosens Bioelectron 2024; 261:116499. [PMID: 38896981 DOI: 10.1016/j.bios.2024.116499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 06/07/2024] [Accepted: 06/12/2024] [Indexed: 06/21/2024]
Abstract
With the advent of flexible electronics and sensing technology, hydrogel-based flexible sensors have exhibited considerable potential across a diverse range of applications, including wearable electronics and soft robotics. Recently, advanced machine learning (ML) algorithms have been integrated into flexible hydrogel sensing technology to enhance their data processing capabilities and to achieve intelligent perception. However, there are no reviews specifically focusing on the data processing steps and analysis based on the raw sensing data obtained by flexible hydrogel sensors. Here we provide a comprehensive review of the latest advancements and breakthroughs in intelligent perception achieved through the fusion of ML algorithms with flexible hydrogel sensors, across various applications. Moreover, this review thoroughly examines the data processing techniques employed in flexible hydrogel sensors, offering valuable perspectives expected to drive future data-driven applications in this field.
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Affiliation(s)
- Derrick Boateng
- College of Applied Sciences, Shenzhen University, Shenzhen, 518060, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, School of Biomedical Engineering, Shenzhen University Medical School, Shenzhen, 518060, China; College of Health Science and Environmental Engineering, Shenzhen Technology University, Shenzhen, 518188, China
| | - Xukai Li
- College of Health Science and Environmental Engineering, Shenzhen Technology University, Shenzhen, 518188, China
| | - Yuhan Zhu
- College of Health Science and Environmental Engineering, Shenzhen Technology University, Shenzhen, 518188, China
| | - Hao Zhang
- School of Physics and Optoelectronic Engineering, Hainan University, Haikou, 570228, China.
| | - Meng Wu
- Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4, Canada
| | - Jifang Liu
- The Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong, 510700, China
| | - Yan Kang
- College of Applied Sciences, Shenzhen University, Shenzhen, 518060, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, School of Biomedical Engineering, Shenzhen University Medical School, Shenzhen, 518060, China; College of Health Science and Environmental Engineering, Shenzhen Technology University, Shenzhen, 518188, China
| | - Hongbo Zeng
- Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4, Canada
| | - Linbo Han
- College of Health Science and Environmental Engineering, Shenzhen Technology University, Shenzhen, 518188, China.
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2
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Catterall WA, Gamal El-Din TM, Wisedchaisri G. The chemistry of electrical signaling in sodium channels from bacteria and beyond. Cell Chem Biol 2024; 31:1405-1421. [PMID: 39151407 DOI: 10.1016/j.chembiol.2024.07.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 06/27/2024] [Accepted: 07/22/2024] [Indexed: 08/19/2024]
Abstract
Electrical signaling is essential for all fast processes in biology, but its molecular mechanisms have been uncertain. This review article focuses on studies of bacterial sodium channels in order to home in on the essential molecular and chemical mechanisms underlying transmembrane ion conductance and voltage-dependent gating without the overlay of complex protein interactions and regulatory mechanisms in mammalian sodium channels. This minimalist approach has yielded a nearly complete picture of sodium channel function at the atomic level that are mostly conserved in mammalian sodium channels, including sodium selectivity and conductance, voltage sensing and activation, electromechanical coupling to pore opening and closing, slow inactivation, and pathogenic dysfunction in a debilitating channelopathy. Future studies of nature's simplest sodium channels may continue to yield key insights into the fundamental molecular and chemical principles of their function and further elucidate the chemical basis of electrical signaling.
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Affiliation(s)
- William A Catterall
- Department of Pharmacology, University of Washington, Seattle WA 98195-7280, USA.
| | - Tamer M Gamal El-Din
- Department of Pharmacology, University of Washington, Seattle WA 98195-7280, USA.
| | - Goragot Wisedchaisri
- Department of Pharmacology, University of Washington, Seattle WA 98195-7280, USA.
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3
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Wojciechowski MN, McKenzie CE, Hung A, Kuanyshbek A, Soh MS, Reid CA, Forster IC. Different fluorescent labels report distinct components of spHCN channel voltage sensor movement. J Gen Physiol 2024; 156:e202413559. [PMID: 38968404 PMCID: PMC11223168 DOI: 10.1085/jgp.202413559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 05/17/2024] [Accepted: 06/11/2024] [Indexed: 07/07/2024] Open
Abstract
We used voltage clamp fluorometry to probe the movement of the S4 helix in the voltage-sensing domain of the sea urchin HCN channel (spHCN) expressed in Xenopus oocytes. We obtained markedly different fluorescence responses with either ALEXA-488 or MTS-TAMRA covalently linked to N-terminal Cys332 of the S4 helix. With hyperpolarizing steps, ALEXA-488 fluorescence increased rapidly, consistent with it reporting the initial inward movement of S4, as previously described. In contrast, MTS-TAMRA fluorescence increased more slowly and its early phase correlated with that of channel opening. Additionally, a slow fluorescence component that tracked the development of the mode shift, or channel hysteresis, could be resolved with both labels. We quantitated this component as an increased deactivation tail current delay with concomitantly longer activation periods and found it to depend strongly on the presence of K+ ions in the pore. Using collisional quenching experiments and structural predictions, we established that ALEXA-488 was more exposed to solvent than MTS-TAMRA. We propose that components of S4 movement during channel activation can be kinetically resolved using different fluorescent probes to reveal distinct biophysical properties. Our findings underscore the need to apply caution when interpreting voltage clamp fluorometry data and demonstrate the potential utility of different labels to interrogate distinct biophysical properties of voltage-gated membrane proteins.
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Affiliation(s)
- Magdalena N. Wojciechowski
- Florey Institute of Neuroscience and Mental Health, Parkville, Australia
- Institut für Pharmazeutische und Medizinische Chemie, Pharmacampus, Universität Münster, Münster, Germany
| | | | - Andrew Hung
- School of Science, STEM College, RMIT University, Melbourne, Australia
| | - Alibek Kuanyshbek
- Florey Institute of Neuroscience and Mental Health, Parkville, Australia
| | - Ming S. Soh
- Florey Institute of Neuroscience and Mental Health, Parkville, Australia
| | | | - Ian C. Forster
- Florey Institute of Neuroscience and Mental Health, Parkville, Australia
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4
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Huang J, Pan X, Yan N. Structural biology and molecular pharmacology of voltage-gated ion channels. Nat Rev Mol Cell Biol 2024:10.1038/s41580-024-00763-7. [PMID: 39103479 DOI: 10.1038/s41580-024-00763-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2024] [Indexed: 08/07/2024]
Abstract
Voltage-gated ion channels (VGICs), including those for Na+, Ca2+ and K+, selectively permeate ions across the cell membrane in response to changes in membrane potential, thus participating in physiological processes involving electrical signalling, such as neurotransmission, muscle contraction and hormone secretion. Aberrant function or dysregulation of VGICs is associated with a diversity of neurological, psychiatric, cardiovascular and muscular disorders, and approximately 10% of FDA-approved drugs directly target VGICs. Understanding the structure-function relationship of VGICs is crucial for our comprehension of their working mechanisms and role in diseases. In this Review, we discuss how advances in single-particle cryo-electron microscopy have afforded unprecedented structural insights into VGICs, especially on their interactions with clinical and investigational drugs. We present a comprehensive overview of the recent advances in the structural biology of VGICs, with a focus on how prototypical drugs and toxins modulate VGIC activities. We explore how these structures elucidate the molecular basis for drug actions, reveal novel pharmacological sites, and provide critical clues to future drug discovery.
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Affiliation(s)
- Jian Huang
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Xiaojing Pan
- Institute of Bio-Architecture and Bio-Interactions (IBABI), Shenzhen Medical Academy of Research and Translation (SMART), Shenzhen, Guangdong, China.
| | - Nieng Yan
- Institute of Bio-Architecture and Bio-Interactions (IBABI), Shenzhen Medical Academy of Research and Translation (SMART), Shenzhen, Guangdong, China.
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, China.
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5
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Kim ED, Wu X, Lee S, Tibbs GR, Cunningham KP, Di Zanni E, Perez ME, Goldstein PA, Accardi A, Larsson HP, Nimigean CM. Propofol rescues voltage-dependent gating of HCN1 channel epilepsy mutants. Nature 2024; 632:451-459. [PMID: 39085604 DOI: 10.1038/s41586-024-07743-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 06/20/2024] [Indexed: 08/02/2024]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels1 are essential for pacemaking activity and neural signalling2,3. Drugs inhibiting HCN1 are promising candidates for management of neuropathic pain4 and epileptic seizures5. The general anaesthetic propofol (2,6-di-iso-propylphenol) is a known HCN1 allosteric inhibitor6 with unknown structural basis. Here, using single-particle cryo-electron microscopy and electrophysiology, we show that propofol inhibits HCN1 by binding to a mechanistic hotspot in a groove between the S5 and S6 transmembrane helices. We found that propofol restored voltage-dependent closing in two HCN1 epilepsy-associated polymorphisms that act by destabilizing the channel closed state: M305L, located in the propofol-binding site in S5, and D401H in S6 (refs. 7,8). To understand the mechanism of propofol inhibition and restoration of voltage-gating, we tracked voltage-sensor movement in spHCN channels and found that propofol inhibition is independent of voltage-sensor conformational changes. Mutations at the homologous methionine in spHCN and an adjacent conserved phenylalanine in S6 similarly destabilize closing without disrupting voltage-sensor movements, indicating that voltage-dependent closure requires this interface intact. We propose a model for voltage-dependent gating in which propofol stabilizes coupling between the voltage sensor and pore at this conserved methionine-phenylalanine interface in HCN channels. These findings unlock potential exploitation of this site to design specific drugs targeting HCN channelopathies.
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Affiliation(s)
- Elizabeth D Kim
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Xiaoan Wu
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Sangyun Lee
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Gareth R Tibbs
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Kevin P Cunningham
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
- School of Life Sciences, University of Westminster, London, UK
| | - Eleonora Di Zanni
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Marta E Perez
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Peter A Goldstein
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Alessio Accardi
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA.
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.
| | - 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.
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6
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Lin JL, Chang Y, Tewari D, Cowgill J, Chanda B. Mapping the contribution of the C-linker domain to gating polarity in CNBD channels. Biophys J 2024; 123:2176-2184. [PMID: 38678368 PMCID: PMC11309966 DOI: 10.1016/j.bpj.2024.04.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/23/2024] [Accepted: 04/22/2024] [Indexed: 04/29/2024] Open
Abstract
Ion channels of the cyclic nucleotide-binding domain (CNBD) family play a crucial role in the regulation of key biological processes, such as photoreception and pacemaking activity in the heart. These channels exhibit high sequence and structural similarity but differ greatly in their functional responses to membrane potential. The CNBD family includes hyperpolarization-activated ion channels and depolarization-activated ether-à-go-go channels. Structural and functional studies show that the differences in the coupling interface between these two subfamilies' voltage-sensing domain and pore domain may underlie their differential response to membrane polarity. However, other structural components may also contribute to defining the polarity differences in activation. Here, we focus on the role of the C-terminal domain, which interacts with elements in both the pore and voltage-sensing domains. By generating a series of chimeras involving the C-terminal domain derived from distant members of the CNBD family, we find that the nature of the C-termini profoundly influences the gating polarity of these ion channels. Scanning mutagenesis of the C-linker region, a helix-turn-helix motif connecting the pore helix to the CNBD, reveals that residues at the intersubunit interface between the C-linkers are crucial for hyperpolarization-dependent activation. These findings highlight the unique and unexpected role of the intersubunit interface of the C-linker region in regulating the gating polarity of voltage-gated ion channels.
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Affiliation(s)
- Jenna L Lin
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Graduate Program in Biochemistry, Biophysics, & Structural Biology, Washington University School of Medicine, St. Louis, Missouri
| | - Yongchang Chang
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Debanjan Tewari
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - John Cowgill
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri.
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7
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Perez-Miller S, Gomez K, Khanna R. Peptide and Peptidomimetic Inhibitors Targeting the Interaction of Collapsin Response Mediator Protein 2 with the N-Type Calcium Channel for Pain Relief. ACS Pharmacol Transl Sci 2024; 7:1916-1936. [PMID: 39022365 PMCID: PMC11249630 DOI: 10.1021/acsptsci.4c00181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/13/2024] [Accepted: 05/23/2024] [Indexed: 07/20/2024]
Abstract
Ion channels serve pleiotropic functions. Often found in complexes, their activities and functions are sculpted by auxiliary proteins. We discovered that collapsin response mediator protein 2 (CRMP2) is a binding partner and regulator of the N-type voltage-gated calcium channel (CaV2.2), a genetically validated contributor to chronic pain. Herein, we trace the discovery of a new peptidomimetic modulator of this interaction, starting from the identification and development of CBD3, a CRMP2-derived CaV binding domain peptide. CBD3 uncouples CRMP2-CaV2.2 binding to decrease CaV2.2 surface localization and calcium currents. These changes occur at presynaptic sites of nociceptive neurons and indeed, CBD3 ameliorates chronic pain in preclinical models. In pursuit of a CBD3 peptidomimetic, we exploited a unique approach to identify a dipeptide with low conformational flexibility and high solvent accessibility that anchors binding to CaV2.2. From a pharmacophore screen, we obtained CBD3063, a small-molecule that recapitulated CBD3's activity, reversing nociceptive behaviors in rodents of both sexes without sensory, affective, or cognitive effects. By disrupting the CRMP2-CaV2.2 interaction, CBD3063 exerts these effects indirectly through modulating CaV2.2 trafficking, supporting CRMP2 as an auxiliary subunit of CaV2.2. The parent peptide CBD3 was also found by us and others to have neuroprotective properties at postsynaptic sites, through N-methyl-d-aspartate receptor and plasmalemmal Na+/Ca2+ exchanger 3, potentially acting as an auxiliary subunit for these pathways as well. Our new compound is poised to address several open questions regarding CRMP2's role in regulating the CaV2.2 pathways to treat pain with the potential added benefit of neuroprotection.
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Affiliation(s)
- Samantha Perez-Miller
- Department
of Pharmacology & Therapeutics, College of Medicine, University of Florida, 1200 Newell Drive, ARB R5-234, Gainesville, Florida 32610-0267, United States
| | - Kimberly Gomez
- Department
of Pharmacology & Therapeutics, College of Medicine, University of Florida, 1200 Newell Drive, ARB R5-234, Gainesville, Florida 32610-0267, United States
| | - Rajesh Khanna
- Department
of Pharmacology & Therapeutics, College of Medicine, University of Florida, 1200 Newell Drive, ARB R5-234, Gainesville, Florida 32610-0267, United States
- Pain
and Addiction Therapeutics (PATH) Collaboratory, College of Medicine, University of Florida, Gainesville, Florida 32610, United States
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8
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Burtscher V, Mount J, Huang J, Cowgill J, Chang Y, Bickel K, Chen J, Yuan P, Chanda B. Structural basis for hyperpolarization-dependent opening of human HCN1 channel. Nat Commun 2024; 15:5216. [PMID: 38890331 PMCID: PMC11189445 DOI: 10.1038/s41467-024-49599-x] [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: 08/14/2023] [Accepted: 06/11/2024] [Indexed: 06/20/2024] Open
Abstract
Hyperpolarization and cyclic nucleotide (HCN) activated ion channels are critical for the automaticity of action potentials in pacemaking and rhythmic electrical circuits in the human body. Unlike most voltage-gated ion channels, the HCN and related plant ion channels activate upon membrane hyperpolarization. Although functional studies have identified residues in the interface between the voltage-sensing and pore domain as crucial for inverted electromechanical coupling, the structural mechanisms for this unusual voltage-dependence remain unclear. Here, we present cryo-electron microscopy structures of human HCN1 corresponding to Closed, Open, and a putative Intermediate state. Our structures reveal that the downward motion of the gating charges past the charge transfer center is accompanied by concomitant unwinding of the inner end of the S4 and S5 helices, disrupting the tight gating interface observed in the Closed state structure. This helix-coil transition at the intracellular gating interface accompanies a concerted iris-like dilation of the pore helices and underlies the reversed voltage dependence of HCN channels.
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Affiliation(s)
- Verena Burtscher
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Jonathan Mount
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jian Huang
- Department of Chemistry, University of Massachusetts, Amherst, MA, USA
| | - John Cowgill
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Yongchang Chang
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Kathleen Bickel
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Jianhan Chen
- Department of Chemistry, University of Massachusetts, Amherst, MA, USA
| | - Peng Yuan
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA.
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO, USA.
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9
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Page DA, Ruben PC. Cannabidiol potentiates hyperpolarization-activated cyclic nucleotide-gated (HCN4) channels. J Gen Physiol 2024; 156:e202313505. [PMID: 38652080 PMCID: PMC11040500 DOI: 10.1085/jgp.202313505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 03/15/2024] [Accepted: 04/09/2024] [Indexed: 04/25/2024] Open
Abstract
Cannabidiol (CBD), the main non-psychotropic phytocannabinoid produced by the Cannabis sativa plant, blocks a variety of cardiac ion channels. We aimed to identify whether CBD regulated the cardiac pacemaker channel or the hyperpolarization-activated cyclic nucleotide-gated channel (HCN4). HCN4 channels are important for the generation of the action potential in the sinoatrial node of the heart and increased heart rate in response to β-adrenergic stimulation. HCN4 channels were expressed in HEK 293T cells, and the effect of CBD application was examined using a whole-cell patch clamp. We found that CBD depolarized the V1/2 of activation in holo-HCN4 channels, with an EC50 of 1.6 µM, without changing the current density. CBD also sped activation kinetics by approximately threefold. CBD potentiation of HCN4 channels occurred via binding to the closed state of the channel. We found that CBD's mechanism of action was distinct from cAMP, as CBD also potentiated apo-HCN4 channels. The addition of an exogenous PIP2 analog did not alter the ability of CBD to potentiate HCN4 channels, suggesting that CBD also acts using a unique mechanism from the known HCN4 potentiator PIP2. Lastly, to gain insight into CBD's mechanism of action, computational modeling and targeted mutagenesis were used to predict that CBD binds to a lipid-binding pocket at the C-terminus of the voltage sensor. CBD represents the first FDA-approved drug to potentiate HCN4 channels, and our findings suggest a novel starting point for drug development targeting HCN4 channels.
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Affiliation(s)
- Dana A. Page
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Peter C. Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
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10
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Yu B, Lu Q, Li J, Cheng X, Hu H, Li Y, Che T, Hua Y, Jiang H, Zhang Y, Xian C, Yang T, Fu Y, Chen Y, Nan W, McCormick PJ, Xiong B, Duan J, Zeng B, Li Y, Fu Y, Zhang J. Cryo-EM structure of human HCN3 channel and its regulation by cAMP. J Biol Chem 2024; 300:107288. [PMID: 38636662 PMCID: PMC11126801 DOI: 10.1016/j.jbc.2024.107288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 03/30/2024] [Accepted: 04/08/2024] [Indexed: 04/20/2024] Open
Abstract
HCN channels are important for regulating heart rhythm and nerve activity and have been studied as potential drug targets for treating depression, arrhythmia, nerve pain, and epilepsy. Despite possessing unique pharmacological properties, HCN channels share common characteristics in that they are activated by hyperpolarization and modulated by cAMP and other membrane lipids. However, the mechanisms of how these ligands bind and modulate HCN channels are unclear. In this study, we solved structures of full-length human HCN3 using cryo-EM and captured two different states, including a state without any ligand bound and a state with cAMP bound. Our structures reveal the novel binding sites for cholesteryl hemisuccinate in apo state and show how cholesteryl hemisuccinate and cAMP binding cause conformational changes in different states. These findings explain how these small modulators are sensed in mammals at the molecular level. The results of our study could help to design more potent and specific compounds to influence HCN channel activity and offer new therapeutic possibilities for diseases that lack effective treatment.
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Affiliation(s)
- Bo Yu
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Qiuyuan Lu
- School of Medicine, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Jian Li
- College of Pharmacy, Gannan Medical University, Ganzhou, China
| | - Xinyu Cheng
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Han Hu
- Shenzhen Crystalo Biopharmaceutical Co, Ltd, Shenzhen, Guangdong, China
| | - Yuanshuo Li
- Shenzhen Crystalo Biopharmaceutical Co, Ltd, Shenzhen, Guangdong, China
| | - Tong Che
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Yaoguang Hua
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Haihai Jiang
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Yuting Zhang
- Shenzhen Crystalo Biopharmaceutical Co, Ltd, Shenzhen, Guangdong, China
| | - Cuiling Xian
- Shenzhen Crystalo Biopharmaceutical Co, Ltd, Shenzhen, Guangdong, China
| | - Tingting Yang
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Ying Fu
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Yixiang Chen
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Weiwei Nan
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China
| | - Peter J McCormick
- William Harvey Research Institute, Bart's and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Bing Xiong
- Department of Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Jingjing Duan
- Human Aging Research Institute (HARI), School of Life Sciences, Nanchang University, Nanchang, Jiangxi, China
| | - Bo Zeng
- Key Laboratory of Medical Electrophysiology, Ministry of Education & Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Yanyan Li
- Department of Chemical Biology, School of Life Southern University of Science and Technology, Southern University of Science and Technology, Shenzhen, Guangdong, China; Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, Guangdong, China.
| | - Yang Fu
- School of Medicine, Southern University of Science and Technology, Shenzhen, Guangdong, China.
| | - Jin Zhang
- The MOE Basic Research and Innovation Center for the Targeted Therapeutics of Solid Tumors, School of Basic Medical Sciences, Jiangxi Medical College, Nanchang University, Nanchang, China; The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China.
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11
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Wu X, Cunningham KP, Bruening-Wright A, Pandey S, Larsson HP. Loose Coupling between the Voltage Sensor and the Activation Gate in Mammalian HCN Channels Suggests a Gating Mechanism. Int J Mol Sci 2024; 25:4309. [PMID: 38673895 PMCID: PMC11050684 DOI: 10.3390/ijms25084309] [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: 03/07/2024] [Revised: 04/10/2024] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
Voltage-gated potassium (Kv) channels and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels share similar structures but have opposite gating polarity. Kv channels have a strong coupling (>109) between the voltage sensor (S4) and the activation gate: when S4s are activated, the gate is open to >80% but, when S4s are deactivated, the gate is open <10-9 of the time. Using noise analysis, we show that the coupling between S4 and the gate is <200 in HCN channels. In addition, using voltage clamp fluorometry, locking the gate open in a Kv channel drastically altered the energetics of S4 movement. In contrast, locking the gate open or decreasing the coupling between S4 and the gate in HCN channels had only minor effects on the energetics of S4 movement, consistent with a weak coupling between S4 and the gate. We propose that this loose coupling is a prerequisite for the reversed voltage gating in HCN channels.
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Affiliation(s)
- Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; (X.W.); (K.P.C.)
| | - Kevin P. Cunningham
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; (X.W.); (K.P.C.)
- School of Life Sciences, University of Westminster, London W1W 6UW, UK
| | | | - Shilpi Pandey
- Oregan National Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006, USA;
| | - H. Peter Larsson
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; (X.W.); (K.P.C.)
- Department of Biomedical and Clinical Sciences, Linköping University, 58185 Linköping, Sweden
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12
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Qi ZX, Yan Q, Fan XJ, Peng JY, Zhu HX, Jiang YM, Chen L, Zhuang QX. Role of HCN channels in the functions of basal ganglia and Parkinson's disease. Cell Mol Life Sci 2024; 81:135. [PMID: 38478096 PMCID: PMC10937777 DOI: 10.1007/s00018-024-05163-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: 10/16/2023] [Revised: 01/19/2024] [Accepted: 02/06/2024] [Indexed: 03/17/2024]
Abstract
Parkinson's disease (PD) is a motor disorder resulting from dopaminergic neuron degeneration in the substantia nigra caused by age, genetics, and environment. The disease severely impacts a patient's quality of life and can even be life-threatening. The hyperpolarization-activated cyclic nucleotide-gated (HCN) channel is a member of the HCN1-4 gene family and is widely expressed in basal ganglia nuclei. The hyperpolarization-activated current mediated by the HCN channel has a distinct impact on neuronal excitability and rhythmic activity associated with PD pathogenesis, as it affects the firing activity, including both firing rate and firing pattern, of neurons in the basal ganglia nuclei. This review aims to comprehensively understand the characteristics of HCN channels by summarizing their regulatory role in neuronal firing activity of the basal ganglia nuclei. Furthermore, the distribution and characteristics of HCN channels in each nucleus of the basal ganglia group and their effect on PD symptoms through modulating neuronal electrical activity are discussed. Since the roles of the substantia nigra pars compacta and reticulata, as well as globus pallidus externus and internus, are distinct in the basal ganglia circuit, they are individually described. Lastly, this investigation briefly highlights that the HCN channel expressed on microglia plays a role in the pathological process of PD by affecting the neuroinflammatory response.
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Affiliation(s)
- Zeng-Xin Qi
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, 200030, China
- National Center for Neurological Disorders, Shanghai, 200030, China
- Shanghai Key Laboratory of Brain Function Restoration and Neural Regeneration, Shanghai, 200030, China
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200030, China
| | - Qi Yan
- Department of Physiology, School of Medicine, Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Xiu-Juan Fan
- Department of Physiology, School of Medicine, Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Jian-Ya Peng
- Department of Physiology, School of Medicine, Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Hui-Xian Zhu
- Department of Physiology, School of Medicine, Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Yi-Miao Jiang
- Department of Physiology, School of Medicine, Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Liang Chen
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, 200030, China.
- National Center for Neurological Disorders, Shanghai, 200030, China.
- Shanghai Key Laboratory of Brain Function Restoration and Neural Regeneration, Shanghai, 200030, China.
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200030, China.
| | - Qian-Xing Zhuang
- Department of Physiology, School of Medicine, Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China.
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13
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Guo SC, Shen R, Roux B, Dinner AR. Dynamics of activation in the voltage-sensing domain of Ciona intestinalis phosphatase Ci-VSP. Nat Commun 2024; 15:1408. [PMID: 38360718 PMCID: PMC10869754 DOI: 10.1038/s41467-024-45514-6] [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: 12/19/2022] [Accepted: 01/25/2024] [Indexed: 02/17/2024] Open
Abstract
The Ciona intestinalis voltage-sensing phosphatase (Ci-VSP) is a membrane protein containing a voltage-sensing domain (VSD) that is homologous to VSDs from voltage-gated ion channels responsible for cellular excitability. Previously published crystal structures of Ci-VSD in putative resting and active conformations suggested a helical-screw voltage sensing mechanism in which the S4 helix translocates and rotates to enable exchange of salt-bridge partners, but the microscopic details of the transition between the resting and active conformations remained unknown. Here, by combining extensive molecular dynamics simulations with a recently developed computational framework based on dynamical operators, we elucidate the microscopic mechanism of the resting-active transition at physiological membrane potential. Sparse regression reveals a small set of coordinates that distinguish intermediates that are hidden from electrophysiological measurements. The intermediates arise from a noncanonical helical-screw mechanism in which translocation, rotation, and side-chain movement of the S4 helix are only loosely coupled. These results provide insights into existing experimental and computational findings on voltage sensing and suggest ways of further probing its mechanism.
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Affiliation(s)
- Spencer C Guo
- Department of Chemistry, The University of Chicago, Chicago, IL, 60637, USA
- James Franck Institute, The University of Chicago, Chicago, IL, 60637, USA
| | - Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Benoît Roux
- Department of Chemistry, The University of Chicago, Chicago, IL, 60637, USA.
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA.
| | - Aaron R Dinner
- Department of Chemistry, The University of Chicago, Chicago, IL, 60637, USA.
- James Franck Institute, The University of Chicago, Chicago, IL, 60637, USA.
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA.
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14
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Liu Z, Wang F, Yuan H, Tian F, Yang C, Hu F, Liu Y, Tang M, Ping M, Kang C, Luo T, Yang G, Hu M, Gao Z, Li P. An LQT2-related mutation in the voltage-sensing domain is involved in switching the gating polarity of hERG. BMC Biol 2024; 22:29. [PMID: 38317233 DOI: 10.1186/s12915-024-01833-0] [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: 02/14/2023] [Accepted: 01/23/2024] [Indexed: 02/07/2024] Open
Abstract
BACKGROUND Cyclic Nucleotide-Binding Domain (CNBD)-family channels display distinct voltage-sensing properties despite sharing sequence and structural similarity. For example, the human Ether-a-go-go Related Gene (hERG) channel and the Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channel share high amino acid sequence similarity and identical domain structures. hERG conducts outward current and is activated by positive membrane potentials (depolarization), whereas HCN conducts inward current and is activated by negative membrane potentials (hyperpolarization). The structural basis for the "opposite" voltage-sensing properties of hERG and HCN remains unknown. RESULTS We found the voltage-sensing domain (VSD) involves in modulating the gating polarity of hERG. We identified that a long-QT syndrome type 2-related mutation within the VSD, K525N, mediated an inwardly rectifying non-deactivating current, perturbing the channel closure, but sparing the open state and inactivated state. K525N rescued the current of a non-functional mutation in the pore helix region (F627Y) of hERG. K525N&F627Y switched hERG into a hyperpolarization-activated channel. The reactivated inward current induced by hyperpolarization mediated by K525N&F627Y can be inhibited by E-4031 and dofetilide quite well. Moreover, we report an extracellular interaction between the S1 helix and the S5-P region is crucial for modulating the gating polarity. The alanine substitution of several residues in this region (F431A, C566A, I607A, and Y611A) impaired the inward current of K525N&F627Y. CONCLUSIONS Our data provide evidence that a potential cooperation mechanism in the extracellular vestibule of the VSD and the PD would determine the gating polarity in hERG.
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Affiliation(s)
- Zhipei Liu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Feng Wang
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Hui Yuan
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Fuyun Tian
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Chuanyan Yang
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Fei Hu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Yiyao Liu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Meiqin Tang
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Meixuan Ping
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chunlan Kang
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Ting Luo
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang, 550025, China
| | - Guimei Yang
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Mei Hu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Pharmacology Laboratory, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou University of Chinese Medicine, Zhongshan, 528401, China
| | - Zhaobing Gao
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China.
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China.
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Ping Li
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China.
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China.
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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15
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Porro A, Saponaro A, Castelli R, Introini B, Hafez Alkotob A, Ranjbari G, Enke U, Kusch J, Benndorf K, Santoro B, DiFrancesco D, Thiel G, Moroni A. A high affinity switch for cAMP in the HCN pacemaker channels. Nat Commun 2024; 15:843. [PMID: 38287019 PMCID: PMC10825183 DOI: 10.1038/s41467-024-45136-y] [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: 05/25/2023] [Accepted: 01/16/2024] [Indexed: 01/31/2024] Open
Abstract
Binding of cAMP to Hyperpolarization activated cyclic nucleotide gated (HCN) channels facilitates pore opening. It is unclear why the isolated cyclic nucleotide binding domain (CNBD) displays in vitro lower affinity for cAMP than the full-length channel in patch experiments. Here we show that HCN are endowed with an affinity switch for cAMP. Alpha helices D and E, downstream of the cyclic nucleotide binding domain (CNBD), bind to and stabilize the holo CNBD in a high affinity state. These helices increase by 30-fold cAMP efficacy and affinity measured in patch clamp and ITC, respectively. We further show that helices D and E regulate affinity by interacting with helix C of the CNBD, similarly to the regulatory protein TRIP8b. Our results uncover an intramolecular mechanism whereby changes in binding affinity, rather than changes in cAMP concentration, can modulate HCN channels, adding another layer to the complex regulation of their activity.
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Affiliation(s)
| | - Andrea Saponaro
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy
| | | | - Bianca Introini
- Department of Biosciences, University of Milan, Milano, Italy
| | | | - Golnaz Ranjbari
- Department of Biosciences, University of Milan, Milano, Italy
| | - Uta Enke
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Jana Kusch
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Klaus Benndorf
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Bina Santoro
- Department of Neuroscience, Zuckerman Institute, Columbia University, New York, NY, USA
| | | | - Gerhard Thiel
- Department of Biology, TU-Darmstadt, Darmstadt, Germany
| | - Anna Moroni
- Department of Biosciences, University of Milan, Milano, Italy.
- Institute of Biophysics Milan, Consiglio Nazionale delle Ricerche, Milano, Italy.
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16
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Stengl M, Schneider AC. Contribution of membrane-associated oscillators to biological timing at different timescales. Front Physiol 2024; 14:1243455. [PMID: 38264332 PMCID: PMC10803594 DOI: 10.3389/fphys.2023.1243455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 12/12/2023] [Indexed: 01/25/2024] Open
Abstract
Environmental rhythms such as the daily light-dark cycle selected for endogenous clocks. These clocks predict regular environmental changes and provide the basis for well-timed adaptive homeostasis in physiology and behavior of organisms. Endogenous clocks are oscillators that are based on positive feedforward and negative feedback loops. They generate stable rhythms even under constant conditions. Since even weak interactions between oscillators allow for autonomous synchronization, coupling/synchronization of oscillators provides the basis of self-organized physiological timing. Amongst the most thoroughly researched clocks are the endogenous circadian clock neurons in mammals and insects. They comprise nuclear clockworks of transcriptional/translational feedback loops (TTFL) that generate ∼24 h rhythms in clock gene expression entrained to the environmental day-night cycle. It is generally assumed that this TTFL clockwork drives all circadian oscillations within and between clock cells, being the basis of any circadian rhythm in physiology and behavior of organisms. Instead of the current gene-based hierarchical clock model we provide here a systems view of timing. We suggest that a coupled system of autonomous TTFL and posttranslational feedback loop (PTFL) oscillators/clocks that run at multiple timescales governs adaptive, dynamic homeostasis of physiology and behavior. We focus on mammalian and insect neurons as endogenous oscillators at multiple timescales. We suggest that neuronal plasma membrane-associated signalosomes constitute specific autonomous PTFL clocks that generate localized but interlinked oscillations of membrane potential and intracellular messengers with specific endogenous frequencies. In each clock neuron multiscale interactions of TTFL and PTFL oscillators/clocks form a temporally structured oscillatory network with a common complex frequency-band comprising superimposed multiscale oscillations. Coupling between oscillator/clock neurons provides the next level of complexity of an oscillatory network. This systemic dynamic network of molecular and cellular oscillators/clocks is suggested to form the basis of any physiological homeostasis that cycles through dynamic homeostatic setpoints with a characteristic frequency-band as hallmark. We propose that mechanisms of homeostatic plasticity maintain the stability of these dynamic setpoints, whereas Hebbian plasticity enables switching between setpoints via coupling factors, like biogenic amines and/or neuropeptides. They reprogram the network to a new common frequency, a new dynamic setpoint. Our novel hypothesis is up for experimental challenge.
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Affiliation(s)
- Monika Stengl
- Department of Biology, Animal Physiology/Neuroethology, University of Kassel, Kassel, Germany
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17
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Shen R, Roux B, Perozo E. Anionic omega currents from single countercharge mutants in the voltage-sensing domain of Ci-VSP. J Gen Physiol 2024; 156:e202213311. [PMID: 38019193 PMCID: PMC10686229 DOI: 10.1085/jgp.202213311] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 06/08/2023] [Accepted: 10/30/2023] [Indexed: 11/30/2023] Open
Abstract
The S4 segment of voltage-sensing domains (VSDs) directly responds to voltage changes by reorienting within the electric field as a permion. A narrow hydrophobic "gasket" or charge transfer center at the core of most VSDs focuses the electric field into a narrow region and catalyzes the sequential and reversible translocation of S4 positive gating charge residues across the electric field while preventing the permeation of physiological ions. Mutating specific S4 gating charges can cause ionic leak currents through the VSDs. These gating pores or omega currents play important pathophysiological roles in many diseases of excitability. Here, we show that mutating D129, a key countercharge residue in the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP), leads to the generation of unique anionic omega currents. Neutralizing D129 causes a dramatic positive shift of activation, facilitates the formation of a continuous water path through the VSD, and creates a positive electrostatic potential landscape inside the VSD that contributes to its unique anionic selectivity. Increasing the population or dwell time of the conducting state by a high external pH or an engineered Cd2+ bridge markedly increases the current magnitude. Our findings uncover a new role of countercharge residues in the impermeable VSD of Ci-VSP and offer insights into mechanisms of the conduction of anionic omega currents linked to countercharge residue mutations.
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Affiliation(s)
- Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
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18
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Huang Y, Ma D, Yang Z, Zhao Y, Guo J. Voltage-gated potassium channels KCNQs: Structures, mechanisms, and modulations. Biochem Biophys Res Commun 2023; 689:149218. [PMID: 37976835 DOI: 10.1016/j.bbrc.2023.149218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/19/2023] [Accepted: 11/03/2023] [Indexed: 11/19/2023]
Abstract
KCNQ (Kv7) channels are voltage-gated, phosphatidylinositol 4,5-bisphosphate- (PIP2-) modulated potassium channels that play essential roles in regulating the activity of neurons and cardiac myocytes. Hundreds of mutations in KCNQ channels are closely related to various cardiac and neurological disorders, such as long QT syndrome, epilepsy, and deafness, which makes KCNQ channels important drug targets. During the past several years, the application of single-particle cryo-electron microscopy (cryo-EM) technique in the structure determination of KCNQ channels has greatly advanced our understanding of their molecular mechanisms. In this review, we summarize the currently available structures of KCNQ channels, analyze their special voltage gating mechanism, and discuss their activation mechanisms by both the endogenous membrane lipid and the exogenous synthetic ligands. These structural studies of KCNQ channels will guide the development of drugs targeting KCNQ channels.
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Affiliation(s)
- Yuan Huang
- Department of Cardiology, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Demin Ma
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Zhenni Yang
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Yiwen Zhao
- The Key Laboratory of Neural and Vascular Biology, The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Ministry of Education, Hebei Medical University, Shijiazhuang, 050011, China
| | - Jiangtao Guo
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China.
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19
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Hu Z, Yang J. Structural basis of properties, mechanisms, and channelopathy of cyclic nucleotide-gated channels. Channels (Austin) 2023; 17:2273165. [PMID: 37905307 PMCID: PMC10761061 DOI: 10.1080/19336950.2023.2273165] [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: 09/07/2023] [Accepted: 10/07/2023] [Indexed: 11/02/2023] Open
Abstract
Recent years have seen an outpouring of atomic or near atomic resolution structures of cyclic nucleotide-gated (CNG) channels, captured in closed, transition, pre-open, partially open, and fully open states. These structures provide unprecedented molecular insights into the activation, assembly, architecture, regulation, and channelopathy of CNG channels, as well as mechanistic explanations for CNG channel biophysical and pharmacological properties. This article summarizes recent advances in CNG channel structural biology, describes key structural features and elements, and illuminates a detailed conformational landscape of activation by cyclic nucleotides. The review also correlates structures with findings and properties delineated in functional studies, including nonselective monovalent cation selectivity, Ca2+ permeation and block, block by L-cis-diltiazem, location of the activation gate, lack of voltage-dependent gating, and modulation by lipids and calmodulin. A perspective on future research is also offered.
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Affiliation(s)
- Zhengshan Hu
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY, USA
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20
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Mishra P, Narayanan R. The enigmatic HCN channels: A cellular neurophysiology perspective. Proteins 2023. [PMID: 37982354 DOI: 10.1002/prot.26643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 10/24/2023] [Accepted: 11/09/2023] [Indexed: 11/21/2023]
Abstract
What physiological role does a slow hyperpolarization-activated ion channel with mixed cation selectivity play in the fast world of neuronal action potentials that are driven by depolarization? That puzzling question has piqued the curiosity of physiology enthusiasts about the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are widely expressed across the body and especially in neurons. In this review, we emphasize the need to assess HCN channels from the perspective of how they respond to time-varying signals, while also accounting for their interactions with other co-expressing channels and receptors. First, we illustrate how the unique structural and functional characteristics of HCN channels allow them to mediate a slow negative feedback loop in the neurons that they express in. We present the several physiological implications of this negative feedback loop to neuronal response characteristics including neuronal gain, voltage sag and rebound, temporal summation, membrane potential resonance, inductive phase lead, spike triggered average, and coincidence detection. Next, we argue that the overall impact of HCN channels on neuronal physiology critically relies on their interactions with other co-expressing channels and receptors. Interactions with other channels allow HCN channels to mediate intrinsic oscillations, earning them the "pacemaker channel" moniker, and to regulate spike frequency adaptation, plateau potentials, neurotransmitter release from presynaptic terminals, and spike initiation at the axonal initial segment. We also explore the impact of spatially non-homogeneous subcellular distributions of HCN channels in different neuronal subtypes and their interactions with other channels and receptors. Finally, we discuss how plasticity in HCN channels is widely prevalent and can mediate different encoding, homeostatic, and neuroprotective functions in a neuron. In summary, we argue that HCN channels form an important class of channels that mediate a diversity of neuronal functions owing to their unique gating kinetics that made them a puzzle in the first place.
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Affiliation(s)
- Poonam Mishra
- Department of Neuroscience, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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21
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Kuwabara MF, Haddad BG, Lenz-Schwab D, Hartmann J, Longo P, Huckschlag BM, Fuß A, Questino A, Berger TK, Machtens JP, Oliver D. Elevator-like movements of prestin mediate outer hair cell electromotility. Nat Commun 2023; 14:7145. [PMID: 37932294 PMCID: PMC10628124 DOI: 10.1038/s41467-023-42489-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 10/12/2023] [Indexed: 11/08/2023] Open
Abstract
The outstanding acuity of the mammalian ear relies on cochlear amplification, an active mechanism based on the electromotility (eM) of outer hair cells. eM is a piezoelectric mechanism generated by little-understood, voltage-induced conformational changes of the anion transporter homolog prestin (SLC26A5). We used a combination of molecular dynamics (MD) simulations and biophysical approaches to identify the structural dynamics of prestin that mediate eM. MD simulations showed that prestin samples a vast conformational landscape with expanded (ES) and compact (CS) states beyond previously reported prestin structures. Transition from CS to ES is dominated by the translational-rotational movement of prestin's transport domain, akin to elevator-type substrate translocation by related solute carriers. Reversible transition between CS and ES states was supported experimentally by cysteine accessibility scanning, cysteine cross-linking between transport and scaffold domains, and voltage-clamp fluorometry (VCF). Our data demonstrate that prestin's piezoelectric dynamics recapitulate essential steps of a structurally conserved ion transport cycle.
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Affiliation(s)
- Makoto F Kuwabara
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Bassam G Haddad
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany
| | - Dominik Lenz-Schwab
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Julia Hartmann
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Piersilvio Longo
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany
| | - Britt-Marie Huckschlag
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Anneke Fuß
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Annalisa Questino
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Thomas K Berger
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Jan-Philipp Machtens
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany.
- Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany.
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany.
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps University, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), Universities of Marburg and Giessen, Marburg, Germany.
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22
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Zhang XY, Tang LH, Nie JW, Zhang CR, Han X, Li QY, Qin L, Wang MH, Huang X, Yu F, Su M, Wang Y, Xu RM, Guo Y, Xie Q, Chen YH. Structure and activation mechanism of the rice Salt Overly Sensitive 1 (SOS1) Na +/H + antiporter. NATURE PLANTS 2023; 9:1924-1936. [PMID: 37884653 DOI: 10.1038/s41477-023-01551-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 09/27/2023] [Indexed: 10/28/2023]
Abstract
Salinity is one of the most severe abiotic stresses that adversely affect plant growth and agricultural productivity. The plant Na+/H+ antiporter Salt Overly Sensitive 1 (SOS1) located in the plasma membrane extrudes excess Na+ out of cells in response to salt stress and confers salt tolerance. However, the molecular mechanism underlying SOS1 activation remains largely elusive. Here we elucidate two cryo-electron microscopy structures of rice (Oryza sativa) SOS1, a full-length protein in an auto-inhibited state and a truncated version in an active state. The SOS1 forms a dimeric architecture, with an NhaA-folded transmembrane domain portion in the membrane and an elongated cytosolic portion of multiple regulatory domains in the cytoplasm. The structural comparison shows that SOS1 adopts an elevator transport mechanism accompanied by a conformational transition of the highly conserved Pro148 in the unwound transmembrane helix 5 (TM5), switching from an occluded conformation in the auto-inhibited state to a conducting conformation in the active state. These findings allow us to propose an inhibition-release mechanism for SOS1 activation and elucidate how SOS1 controls Na+ homeostasis in response to salt stress.
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Affiliation(s)
- Xiang-Yun Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ling-Hui Tang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jia-Wei Nie
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Chun-Rui Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiaonan Han
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Qi-Yu Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Li Qin
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Mei-Hua Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiahe Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Feifei Yu
- College of Grassland Science and Technology, China Agricultural University, Beijing, China
| | - Min Su
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Yingchun Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Rui-Ming Xu
- University of Chinese Academy of Sciences, Beijing, China
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yan Guo
- State Key Laboratory of Plant Environmental Resilience, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Qi Xie
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China
- National Center of Technology Innovation for Maize, State Key Laboratory of Crop Germplasm Innovation and Molecular Breeding, Syngenta Group China, Beijing, China
| | - Yu-Hang Chen
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
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23
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Kalienkova V, Peter MF, Rheinberger J, Paulino C. Structures of a sperm-specific solute carrier gated by voltage and cAMP. Nature 2023; 623:202-209. [PMID: 37880361 PMCID: PMC10620091 DOI: 10.1038/s41586-023-06629-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 09/08/2023] [Indexed: 10/27/2023]
Abstract
The newly characterized sperm-specific Na+/H+ exchanger stands out by its unique tripartite domain composition1,2. It unites a classical solute carrier unit with regulatory domains usually found in ion channels, namely, a voltage-sensing domain and a cyclic-nucleotide binding domain1,3, which makes it a mechanistic chimera and a secondary-active transporter activated strictly by membrane voltage. Our structures of the sea urchin SpSLC9C1 in the absence and presence of ligands reveal the overall domain arrangement and new structural coupling elements. They allow us to propose a gating model, where movements in the voltage sensor indirectly cause the release of the exchanging unit from a locked state through long-distance allosteric effects transmitted by the newly characterized coupling helices. We further propose that modulation by its ligand cyclic AMP occurs by means of disruption of the cytosolic dimer interface, which lowers the energy barrier for S4 movements in the voltage-sensing domain. As SLC9C1 members have been shown to be essential for male fertility, including in mammals2,4,5, our structure represents a potential new platform for the development of new on-demand contraceptives.
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Affiliation(s)
- Valeria Kalienkova
- Groningen Biomolecular Sciences and Biotechnology, University of Groningen, Groningen, The Netherlands
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Martin F Peter
- Groningen Biomolecular Sciences and Biotechnology, University of Groningen, Groningen, The Netherlands
- Biochemistry Center, Heidelberg University, Heidelberg, Germany
| | - Jan Rheinberger
- Biochemistry Center, Heidelberg University, Heidelberg, Germany
| | - Cristina Paulino
- Groningen Biomolecular Sciences and Biotechnology, University of Groningen, Groningen, The Netherlands.
- Biochemistry Center, Heidelberg University, Heidelberg, Germany.
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24
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Handlin LJ, Dai G. Direct regulation of the voltage sensor of HCN channels by membrane lipid compartmentalization. Nat Commun 2023; 14:6595. [PMID: 37852983 PMCID: PMC10584925 DOI: 10.1038/s41467-023-42363-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 10/09/2023] [Indexed: 10/20/2023] Open
Abstract
Ion channels function within a membrane environment characterized by dynamic lipid compartmentalization. Limited knowledge exists regarding the response of voltage-gated ion channels to transmembrane potential within distinct membrane compartments. By leveraging fluorescence lifetime imaging microscopy (FLIM) and Förster resonance energy transfer (FRET), we visualized the localization of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in membrane domains. HCN4 exhibits a greater propensity for incorporation into ordered lipid domains compared to HCN1. To investigate the conformational changes of the S4 helix voltage sensor of HCN channels, we used dual stop-codon suppression to incorporate different noncanonical amino acids, orthogonal click chemistry for site-specific fluorescence labeling, and transition metal FLIM-FRET. Remarkably, altered FRET levels were observed between VSD sites within HCN channels upon disruption of membrane domains. We propose that the voltage-sensor rearrangements, directly influenced by membrane lipid domains, can explain the heightened activity of pacemaker HCN channels when localized in cholesterol-poor, disordered lipid domains, leading to membrane hyperexcitability and diseases.
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Affiliation(s)
- Lucas J Handlin
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1100 South Grand Blvd., St. Louis, MO, 63104, USA
| | - Gucan Dai
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1100 South Grand Blvd., St. Louis, MO, 63104, USA.
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25
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Han X, Lu T, Zhang Z, Wang H, Lu S. Tremella polysaccharide-based conductive hydrogel with anti-freezing and self-healing ability for motion monitoring and intelligent interaction. Int J Biol Macromol 2023; 248:125987. [PMID: 37516220 DOI: 10.1016/j.ijbiomac.2023.125987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/20/2023] [Accepted: 07/23/2023] [Indexed: 07/31/2023]
Abstract
The application of conductive hydrogels in flexible wearable devices has garnered significant attention. In this study, a self-healing, anti-freezing, and fire-resistant hydrogel strain sensor is successfully synthesized by incorporating sustainable natural biological materials, viz. Tremella polysaccharide and silk fiber, into a polyvinyl alcohol matrix with borax cross-linking. The resulting hydrogel exhibits excellent transparency, thermoplasticity, and remarkable mechanical properties, including a notable elongation (1107.3 %) and high self-healing rate (91.11 %) within 5 min, attributed to the dynamic cross-linking effect of hydrogen bonds and borax. A strain sensor based on the prepared hydrogel sensor can be used to accurately monitor diverse human movements, while maintaining exceptional sensing stability and durability under repeated strain cycles. Additionally, a hydrogel touch component is designed that can successfully interact with intelligent electronic devices, encompassing functions like clicking, writing, and drawing. These inherent advantages make the prepared hydrogel a promising candidate for applications in human health monitoring and intelligent electronic device interaction.
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Affiliation(s)
- Xiaokun Han
- Key Laboratory of Rubber-Plastics of Ministry of Education/Shandong Provincial Key Laboratory of Rubber, Plastics, School of Polymer Science and Engineering, Qingdao University of Science & Technology, Qingdao 266061, PR China; Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, School of Material Science and Engineering, Guilin University of Technology, Guilin 541004, PR China
| | - Tianyun Lu
- Key Laboratory of Rubber-Plastics of Ministry of Education/Shandong Provincial Key Laboratory of Rubber, Plastics, School of Polymer Science and Engineering, Qingdao University of Science & Technology, Qingdao 266061, PR China
| | - Zuocai Zhang
- Shenzhen Key Laboratory of Polymer Science and Technology, Guangdong Research Center for Interfacial Engineering of Functional Materials, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - He Wang
- Key Laboratory of Rubber-Plastics of Ministry of Education/Shandong Provincial Key Laboratory of Rubber, Plastics, School of Polymer Science and Engineering, Qingdao University of Science & Technology, Qingdao 266061, PR China
| | - Shaorong Lu
- Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, School of Material Science and Engineering, Guilin University of Technology, Guilin 541004, PR China.
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26
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Burtscher V, Mount J, Cowgill J, Chang Y, Bickel K, Yuan P, Chanda B. Structural Basis for Hyperpolarization-dependent Opening of the Human HCN1 Channel. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.17.553623. [PMID: 37645882 PMCID: PMC10462129 DOI: 10.1101/2023.08.17.553623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Hyperpolarization and cyclic-nucleotide (HCN) activated ion channels play a critical role in generating self-propagating action potentials in pacemaking and rhythmic electrical circuits in the human body. Unlike most voltage-gated ion channels, the HCN channels activate upon membrane hyperpolarization, but the structural mechanisms underlying this gating behavior remain unclear. Here, we present cryo-electron microscopy structures of human HCN1 in Closed, Intermediate, and Open states. Our structures reveal that the inward motion of two gating charges past the charge transfer center (CTC) and concomitant tilting of the S5 helix drives the opening of the central pore. In the intermediate state structure, a single gating charge is positioned below the CTC and the pore appears closed, whereas in the open state structure, both charges move past CTC and the pore is fully open. Remarkably, the downward motion of the voltage sensor is accompanied by progressive unwinding of the inner end of S4 and S5 helices disrupting the tight gating interface that stabilizes the Closed state structure. This "melting" transition at the intracellular gating interface leads to a concerted iris-like displacement of S5 and S6 helices, resulting in pore opening. These findings reveal key structural features that are likely to underlie reversed voltage-dependence of HCN channels.
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Affiliation(s)
- Verena Burtscher
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jonathan Mount
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - John Cowgill
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Yongchang Chang
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Kathleen Bickel
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO, USA
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27
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Catacuzzeno L, Conti F, Franciolini F. Fifty years of gating currents and channel gating. J Gen Physiol 2023; 155:e202313380. [PMID: 37410612 PMCID: PMC10324510 DOI: 10.1085/jgp.202313380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/12/2023] [Accepted: 06/02/2023] [Indexed: 07/08/2023] Open
Abstract
We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Franco Conti
- Department of Physics, University of Genova, Genova, Italy
| | - Fabio Franciolini
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
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28
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Wojciechowski MN, Schreiber S, Jose J. A Novel Flow Cytometry-Based Assay for the Identification of HCN4 CNBD Ligands. Pharmaceuticals (Basel) 2023; 16:ph16050710. [PMID: 37242492 DOI: 10.3390/ph16050710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/25/2023] [Accepted: 05/03/2023] [Indexed: 05/28/2023] Open
Abstract
Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are promising therapeutic targets because of their association with the genesis of several diseases. The identification of selective compounds that alter cAMP-induced ion channel modulation by binding to the cyclic nucleotide-binding domain (CNBD) will facilitate HCN channel-specific drug development. In this study, a fast and protein purification-free ligand-binding approach with a surface-displayed HCN4 C-Linker-CNBD on E. coli is presented. 8-Fluo-cAMP ligand binding was monitored by single-cell analysis via flow cytometry, and a Kd-value of 173 ± 46 nM was determined. The Kd value was confirmed by ligand depletion analysis and equilibrium state measurements. Applying increasing concentrations of cAMP led to a concentration-dependent decrease in fluorescence intensity, indicating a displacement of 8-Fluo-cAMP. A Ki-value of 8.5 ± 2 µM was determined. The linear relationship of IC50 values obtained for cAMP as a function of ligand concentration confirmed the competitive binding mode: IC50: 13 ± 2 µM/16 ± 3 µM/23 ± 1 µM/27 ± 1 µM for 50 nM/150 nM/250 nM/500 nM 8-Fluo-cAMP. A similar competitive mode of binding was confirmed for 7-CH-cAMP, and an IC50 value of 230 ± 41 nM and a Ki of 159 ± 29 nM were determined. Two established drugs were tested in the assay. Ivabradine, an approved HCN channel pore blocker and gabapentin, is known to bind to HCN4 channels in preference to other isoforms with an unknown mode of action. As expected, ivabradine had no impact on ligand binding. In addition, gabapentin had no influence on 8-Fluo-cAMP's binding to HCN4-CNBD. This is the first indication that gabapentin is not interacting with this part of the HCN4 channel. The ligand-binding assay as described can be used to determine binding constants for ligands such as cAMP and derivatives. It could also be applied for the identification of new ligands binding to the HCN4-CNBD.
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Affiliation(s)
- Magdalena N Wojciechowski
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, Pharmacampus, 48149 Münster, Germany
| | - Sebastian Schreiber
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, Pharmacampus, 48149 Münster, Germany
| | - Joachim Jose
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, Pharmacampus, 48149 Münster, Germany
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29
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Wu X, Cunningham KP, Ramentol R, Perez ME, Larsson HP. Similar voltage-sensor movement in spHCN channels can cause closing, opening, or inactivation. J Gen Physiol 2023; 155:e202213170. [PMID: 36752823 PMCID: PMC9948645 DOI: 10.1085/jgp.202213170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 11/22/2022] [Accepted: 01/27/2023] [Indexed: 02/09/2023] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels contribute to the rhythmic firing of pacemaker neurons and cardiomyocytes. Mutations in HCN channels are associated with cardiac arrhythmia and epilepsy. HCN channels belong to the superfamily of voltage-gated K+ channels, most of which are activated by depolarization. HCN channels, however, are activated by hyperpolarization. The mechanism behind this reversed gating polarity of HCN channels is not clear. We here show that sea urchin HCN (spHCN) channels with mutations in the C-terminal part of the voltage sensor use the same voltage-sensor movement to either close or open in response to hyperpolarizations depending on the absence or presence of cAMP. Our results support that non-covalent interactions at the C-terminal end of the voltage sensor are critical for HCN gating polarity. These interactions are also critical for the proper closing of the channels because these mutations exhibit large constitutive currents. Since a similar voltage-sensor movement can cause both depolarization- and hyperpolarization-activation in the same channel, this suggests that the coupling between the voltage sensor and the pore is changed to create channels opened by different polarities. We also show an identical voltage-sensor movement in activated and inactivated spHCN channels and suggest a model for spHCN activation and inactivation. Our results suggest the possibility that channels open by opposite voltage dependence, such as HCN and the related EAG channels, use the same voltage-sensor movement but different coupling mechanisms between the voltage sensor and the gate.
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Affiliation(s)
- Xiaoan Wu
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Kevin P. Cunningham
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Rosamary Ramentol
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Marta E. Perez
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - H. Peter Larsson
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
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30
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Zhang M, Shan Y, Pei D. Mechanism underlying delayed rectifying in human voltage-mediated activation Eag2 channel. Nat Commun 2023; 14:1470. [PMID: 36928654 PMCID: PMC10020445 DOI: 10.1038/s41467-023-37204-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 03/07/2023] [Indexed: 03/18/2023] Open
Abstract
The transmembrane voltage gradient is a general physico-chemical cue that regulates diverse biological function through voltage-gated ion channels. How voltage sensing mediates ion flows remains unknown at the molecular level. Here, we report six conformations of the human Eag2 (hEag2) ranging from closed, pre-open, open, and pore dilation but non-conducting states captured by cryo-electron microscopy (cryo-EM). These multiple states illuminate dynamics of the selectivity filter and ion permeation pathway with delayed rectifier properties and Cole-Moore effect at the atomic level. Mechanistically, a short S4-S5 linker is coupled with the constrict sites to mediate voltage transducing in a non-domain-swapped configuration, resulting transitions for constrict sites of F464 and Q472 from gating to open state stabilizing for voltage energy transduction. Meanwhile, an additional potassium ion occupied at positions S6 confers the delayed rectifier property and Cole-Moore effects. These results provide insight into voltage transducing and potassium current across membrane, and shed light on the long-sought Cole-Moore effects.
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Affiliation(s)
- Mingfeng Zhang
- Fudan University, 200433, Shanghai, China
- Laboratory of Cell Fate Control, School of Life Sciences, Westlake University, 310000, Hangzhou, China
| | - Yuanyue Shan
- Fudan University, 200433, Shanghai, China
- Laboratory of Cell Fate Control, School of Life Sciences, Westlake University, 310000, Hangzhou, China
| | - Duanqing Pei
- Laboratory of Cell Fate Control, School of Life Sciences, Westlake University, 310000, Hangzhou, China.
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31
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Willems A, Kalaw A, Ecer A, Kotwal A, Roepe LD, Roepe PD. Structures of Plasmodium falciparum Chloroquine Resistance Transporter (PfCRT) Isoforms and Their Interactions with Chloroquine. Biochemistry 2023; 62:1093-1110. [PMID: 36800498 PMCID: PMC10950298 DOI: 10.1021/acs.biochem.2c00669] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 02/02/2023] [Indexed: 02/19/2023]
Abstract
Using a recently elucidated atomic-resolution cryogenic electron microscopy (cryo-EM) structure for the Plasmodium falciparum chloroquine resistance transporter (PfCRT) protein 7G8 isoform as template [Kim, J.; Nature 2019, 576, 315-320], we use Monte Carlo molecular dynamics (MC/MD) simulations of PfCRT embedded in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane to solve energy-minimized structures for 7G8 PfCRT and two additional PfCRT isoforms that harbor 5 or 7 amino acid substitutions relative to 7G8 PfCRT. Guided by drug binding previously defined using chloroquine (CQ) photoaffinity probe labeling, we also use MC/MD energy minimization to elucidate likely CQ binding geometries for the three membrane-embedded isoforms. We inventory salt bridges and hydrogen bonds in these structures and summarize how the limited changes in primary sequence subtly perturb local PfCRT isoform structure. In addition, we use the "AlphaFold" artificial intelligence AlphaFold2 (AF2) algorithm to solve for domain structure that was not resolved in the previously reported 7G8 PfCRT cryo-EM structure, and perform MC/MD energy minimization for the membrane-embedded AF2 structures of all three PfCRT isoforms. We compare energy-minimized structures generated using cryo-EM vs AF2 templates. The results suggest how amino acid substitutions in drug resistance-associated isoforms of PfCRT influence PfCRT structure and CQ transport.
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Affiliation(s)
| | | | - Ayse Ecer
- Departments of Chemistry
and Biochemistry and Cellular and Molecular Biology, Georgetown University, 37th and O Streets NW, Washington, District of Columbia 20057, United States
| | - Amitesh Kotwal
- Departments of Chemistry
and Biochemistry and Cellular and Molecular Biology, Georgetown University, 37th and O Streets NW, Washington, District of Columbia 20057, United States
| | | | - Paul D. Roepe
- Departments of Chemistry
and Biochemistry and Cellular and Molecular Biology, Georgetown University, 37th and O Streets NW, Washington, District of Columbia 20057, United States
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32
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Abstract
Voltage-dependent ion channels regulate the opening of their pores by sensing the membrane voltage. This process underlies the propagation of action potentials and other forms of electrical activity in cells. The voltage dependence of these channels is governed by the transmembrane displacement of the positive charged S4 helix within their voltage-sensor domains. We use cryo-electron microscopy to visualize this movement in the mammalian Eag voltage-dependent potassium channel in lipid membrane vesicles with a voltage difference across the membrane. Multiple structural configurations show that the applied electric field displaces S4 toward the cytoplasm by two helical turns, resulting in an extended interfacial helix near the inner membrane leaflet. The position of S4 in this down conformation is sterically incompatible with an open pore, thus explaining how movement of the voltage sensor at hyperpolarizing membrane voltages locks the pore shut in this kind of voltage-dependent K+ (Kv) channel. The structures solved in lipid bilayer vesicles detail the intricate interplay between Kv channels and membranes, from showing how arginines are stabilized deep within the membrane and near phospholipid headgroups, to demonstrating how the channel reshapes the inner leaflet of the membrane itself.
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33
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Gating intermediates reveal inhibitory role of the voltage sensor in a cyclic nucleotide-modulated ion channel. Nat Commun 2022; 13:6919. [PMID: 36376326 PMCID: PMC9663499 DOI: 10.1038/s41467-022-34673-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/02/2022] [Indexed: 11/16/2022] Open
Abstract
Understanding how ion channels gate is important for elucidating their physiological roles and targeting them in pathophysiological states. Here, we used SthK, a cyclic nucleotide-modulated channel from Spirochaeta thermophila, to define a ligand-gating trajectory that includes multiple on-pathway intermediates. cAMP is a poor partial agonist for SthK and depolarization increases SthK activity. Tuning the energy landscape by gain-of-function mutations in the voltage sensor domain (VSD) allowed us to capture multiple intermediates along the ligand-activation pathway, highlighting the allosteric linkage between VSD, cyclic nucleotide-binding (CNBD) and pore domains. Small, lateral displacements of the VSD S4 segment were necessary to open the intracellular gate, pointing to an inhibitory VSD at rest. We propose that in wild-type SthK, depolarization leads to such VSD displacements resulting in release of inhibition. In summary, we report conformational transitions along the activation pathway that reveal allosteric couplings between key sites integrating to open the intracellular gate.
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34
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Schmidpeter PAM, Wu D, Rheinberger J, Riegelhaupt PM, Tang H, Robinson CV, Nimigean CM. Anionic lipids unlock the gates of select ion channels in the pacemaker family. Nat Struct Mol Biol 2022; 29:1092-1100. [PMID: 36352139 PMCID: PMC10022520 DOI: 10.1038/s41594-022-00851-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 09/25/2022] [Indexed: 11/11/2022]
Abstract
Lipids play important roles in regulating membrane protein function, but the molecular mechanisms used are elusive. Here we investigated how anionic lipids modulate SthK, a bacterial pacemaker channel homolog, and HCN2, whose activity contributes to pacemaking in the heart and brain. Using SthK allowed the reconstitution of purified channels in controlled lipid compositions for functional and structural assays that are not available for the eukaryotic channels. We identified anionic lipids bound tightly to SthK and their exact binding locations and determined that they potentiate channel activity. Cryo-EM structures in the most potentiating lipids revealed an open state and identified a nonannular lipid bound with its headgroup near an intersubunit salt bridge that clamps the intracellular channel gate shut. Breaking this conserved salt bridge abolished lipid modulation in SthK and eukaryotic HCN2 channels, indicating that anionic membrane lipids facilitate channel opening by destabilizing these interactions. Our findings underline the importance of state-dependent protein-lipid interactions.
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Affiliation(s)
| | - Di Wu
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Jan Rheinberger
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, USA
- Department of Structural Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | | | - Haiping Tang
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, USA.
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35
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Mechanism of voltage gating in the voltage-sensing phosphatase Ci-VSP. Proc Natl Acad Sci U S A 2022; 119:e2206649119. [PMID: 36279472 PMCID: PMC9636939 DOI: 10.1073/pnas.2206649119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conformational changes in voltage-sensing domains (VSDs) are driven by the transmembrane electric field acting on the protein charges. Yet, the overall energetics and detailed mechanism of this process are not fully understood. Here, we determined free energy and displacement charge landscapes as well as the major conformations visited during a complete functional gating cycle in the isolated VSD of the phosphatase Ci-VSP (Ci-VSD) comprising four transmembrane helices (segments S1 to S4). Molecular dynamics simulations highlight the extent of S4 movements. In addition to the crystallographically determined activated “Up” and resting “Down” states, the simulations predict two Ci-VSD conformations: a deeper resting state (“down-minus”) and an extended activated (“up-plus”) state. These additional conformations were experimentally probed via systematic cysteine mutagenesis with metal-ion bridges and the engineering of proton conducting mutants at hyperpolarizing voltages. The present results show that these four states are visited sequentially in a stepwise manner during voltage activation, each step translocating one arginine or the equivalent of ∼1
e
0
across the membrane electric field, yielding a transfer of ∼3
e
0
charges in total for the complete process.
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36
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Dickinson MS, Pourmal S, Gupta M, Bi M, Stroud RM. Symmetry Reduction in a Hyperpolarization-Activated Homotetrameric Ion Channel. Biochemistry 2022; 61:2177-2181. [PMID: 34964607 PMCID: PMC9931035 DOI: 10.1021/acs.biochem.1c00654] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Plants obtain nutrients from the soil via transmembrane transporters and channels in their root hairs, from which ions radially transport in toward the xylem for distribution across the plant body. We determined structures of the hyperpolarization-activated channel AKT1 from Arabidopsis thaliana, which mediates K+ uptake from the soil into plant roots. These structures of AtAKT1 embedded in lipid nanodiscs show that the channel undergoes a reduction of C4 to C2 symmetry, possibly to regulate its electrical activation.
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Affiliation(s)
- Miles Sasha Dickinson
- Department of Biochemistry and Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94158, United States
- Chemistry and Chemical Biology Graduate Program, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94143, United States
| | - Sergei Pourmal
- Department of Biochemistry and Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94158, United States
- Chemistry and Chemical Biology Graduate Program, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94143, United States
| | - Meghna Gupta
- Department of Biochemistry and Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94158, United States
| | - Maxine Bi
- Department of Biochemistry and Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94158, United States
- Graduate Group in Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94143, United States
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94158, United States
- Chemistry and Chemical Biology Graduate Program, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94143, United States
- Graduate Group in Biophysics, University of California San Francisco, Genentech Hall, 600 16th Street, San Francisco, California 94143, United States
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37
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Structural basis for the activity regulation of a potassium channel AKT1 from Arabidopsis. Nat Commun 2022; 13:5682. [PMID: 36167696 PMCID: PMC9515098 DOI: 10.1038/s41467-022-33420-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 09/16/2022] [Indexed: 11/25/2022] Open
Abstract
The voltage-gated potassium channel AKT1 is responsible for primary K+ uptake in Arabidopsis roots. AKT1 is functionally activated through phosphorylation and negatively regulated by a potassium channel α-subunit AtKC1. However, the molecular basis for the modulation mechanism remains unclear. Here we report the structures of AKT1, phosphorylated-AKT1, a constitutively-active variant, and AKT1-AtKC1 complex. AKT1 is assembled in 2-fold symmetry at the cytoplasmic domain. Such organization appears to sterically hinder the reorientation of C-linkers during ion permeation. Phosphorylated-AKT1 adopts an alternate 4-fold symmetric conformation at cytoplasmic domain, which indicates conformational changes associated with symmetry switch during channel activation. To corroborate this finding, we perform structure-guided mutagenesis to disrupt the dimeric interface and identify a constitutively-active variant Asp379Ala mediates K+ permeation independently of phosphorylation. This variant predominantly adopts a 4-fold symmetric conformation. Furthermore, the AKT1-AtKC1 complex assembles in 2-fold symmetry. Together, our work reveals structural insight into the regulatory mechanism for AKT1. Arabidopsis thaliana potassium channel AKT1 is responsible for primary K + uptake from soil, which is functionally activated through phosphorylation and negatively regulated by an α-subunit AtKC1. Here, the authors report the structures of AKT1 at different states, revealing a 2- fold to 4-fold symmetry switch at cytoplasmic domain associated with AKT1 activity regulation.
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38
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Yüksel S, Bonus M, Schwabe T, Pfleger C, Zimmer T, Enke U, Saß I, Gohlke H, Benndorf K, Kusch J. Uncoupling of Voltage- and Ligand-Induced Activation in HCN2 Channels by Glycine Inserts. Front Physiol 2022; 13:895324. [PMID: 36091400 PMCID: PMC9452628 DOI: 10.3389/fphys.2022.895324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 06/20/2022] [Indexed: 11/24/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetramers that generate electrical rhythmicity in special brain neurons and cardiomyocytes. The channels are activated by membrane hyperpolarization. The binding of cAMP to the four available cyclic nucleotide-binding domains (CNBD) enhances channel activation. We analyzed in the present study the mechanism of how the effect of cAMP binding is transmitted to the pore domain. Our strategy was to uncouple the C-linker (CL) from the channel core by inserting one to five glycine residues between the S6 gate and the A′-helix (constructs 1G to 5G). We quantified in full-length HCN2 channels the resulting functional effects of the inserted glycines by current activation as well as the structural dynamics and statics using molecular dynamics simulations and Constraint Network Analysis. We show functionally that already in 1G the cAMP effect on activation is lost and that with the exception of 3G and 5G the concentration-activation relationships are shifted to depolarized voltages with respect to HCN2. The strongest effect was found for 4G. Accordingly, the activation kinetics were accelerated by all constructs, again with the strongest effect in 4G. The simulations reveal that the average residue mobility of the CL and CNBD domains is increased in all constructs and that the junction between the S6 and A′-helix is turned into a flexible hinge, resulting in a destabilized gate in all constructs. Moreover, for 3G and 4G, there is a stronger downward displacement of the CL-CNBD than in HCN2 and the other constructs, resulting in an increased kink angle between S6 and A′-helix, which in turn loosens contacts between the S4-helix and the CL. This is suggested to promote a downward movement of the S4-helix, similar to the effect of hyperpolarization. In addition, exclusively in 4G, the selectivity filter in the upper pore region and parts of the S4-helix are destabilized. The results provide new insights into the intricate activation of HCN2 channels.
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Affiliation(s)
- Sezin Yüksel
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Michele Bonus
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Tina Schwabe
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Christopher Pfleger
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Thomas Zimmer
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Uta Enke
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Inga Saß
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Holger Gohlke
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Institute of Biological Information Processing (IBI-7: Structural Biochemistry) and Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Jülich, Germany
- *Correspondence: Holger Gohlke, ; Klaus Benndorf, ; Jana Kusch,
| | - Klaus Benndorf
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
- *Correspondence: Holger Gohlke, ; Klaus Benndorf, ; Jana Kusch,
| | - Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
- *Correspondence: Holger Gohlke, ; Klaus Benndorf, ; Jana Kusch,
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39
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Abstract
In neurosecretion, allosteric communication between voltage sensors and Ca2+ binding in BK channels is crucially involved in damping excitatory stimuli. Nevertheless, the voltage-sensing mechanism of BK channels is still under debate. Here, based on gating current measurements, we demonstrate that two arginines in the transmembrane segment S4 (R210 and R213) function as the BK gating charges. Significantly, the energy landscape of the gating particles is electrostatically tuned by a network of salt bridges contained in the voltage sensor domain (VSD). Molecular dynamics simulations and proton transport experiments in the hyperpolarization-activated R210H mutant suggest that the electric field drops off within a narrow septum whose boundaries are defined by the gating charges. Unlike Kv channels, the charge movement in BK appears to be limited to a small displacement of the guanidinium moieties of R210 and R213, without significant movement of the S4.
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40
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Ye W, Zhao H, Dai Y, Wang Y, Lo YH, Jan LY, Lee CH. Activation and closed-state inactivation mechanisms of the human voltage-gated K V4 channel complexes. Mol Cell 2022; 82:2427-2442.e4. [PMID: 35597238 DOI: 10.1016/j.molcel.2022.04.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 03/03/2022] [Accepted: 04/24/2022] [Indexed: 12/30/2022]
Abstract
The voltage-gated ion channel activity depends on both activation (transition from the resting state to the open state) and inactivation. Inactivation is a self-restraint mechanism to limit ion conduction and is as crucial to membrane excitability as activation. Inactivation can occur when the channel is open or closed. Although open-state inactivation is well understood, the molecular basis of closed-state inactivation has remained elusive. We report cryo-EM structures of human KV4.2 channel complexes in inactivated, open, and closed states. Closed-state inactivation of KV4 involves an unprecedented symmetry breakdown for pore closure by only two of the four S4-S5 linkers, distinct from known mechanisms of open-state inactivation. We further capture KV4 in a putative resting state, revealing how voltage sensor movements control the pore. Moreover, our structures provide insights regarding channel modulation by KChIP2 and DPP6 auxiliary subunits. Our findings elucidate mechanisms of closed-state inactivation and voltage-dependent activation of the KV4 channel.
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Affiliation(s)
- Wenlei Ye
- Department of Physiology, University of California, San Francisco, CA 94158, USA
| | - Hongtu Zhao
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Yaxin Dai
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Yingdi Wang
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Yu-Hua Lo
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Lily Yeh Jan
- Department of Physiology, University of California, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, CA 94158, USA.
| | - Chia-Hsueh Lee
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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41
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Kondapuram M, Frieg B, Yüksel S, Schwabe T, Sattler C, Lelle M, Schweinitz A, Schmauder R, Benndorf K, Gohlke H, Kusch J. Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels. Commun Biol 2022; 5:430. [PMID: 35534535 PMCID: PMC9085832 DOI: 10.1038/s42003-022-03360-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
Hyperpolarization-activated and cyclic nucleotide (HCN) modulated channels are tetrameric cation channels. In each of the four subunits, the intracellular cyclic nucleotide-binding domain (CNBD) is coupled to the transmembrane domain via a helical structure, the C-linker. High-resolution channel structures suggest that the C-linker enables functionally relevant interactions with the opposite subunit, which might be critical for coupling the conformational changes in the CNBD to the channel pore. We combined mutagenesis, patch-clamp technique, confocal patch-clamp fluorometry, and molecular dynamics (MD) simulations to show that residue K464 of the C-linker is relevant for stabilizing the closed state of the mHCN2 channel by forming interactions with the opposite subunit. MD simulations revealed that in the K464E channel, a rotation of the intracellular domain relative to the channel pore is induced, which is similar to the cAMP-induced rotation, weakening the autoinhibitory effect of the unoccupied CL-CNBD region. We suggest that this CL-CNBD rotation is considerably involved in activation-induced affinity increase but only indirectly involved in gate modulation. The adopted poses shown herein are in excellent agreement with previous structural results. Interactions between opposite subunits of HCN channels are relevant for stabilizing the auto-inhibited state of the channel. Like cAMP-binding, K464E-mutation breaks these interactions to favor a channel’s pre-activated state.
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Affiliation(s)
- Mahesh Kondapuram
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Benedikt Frieg
- John von Neumann-Institut für Computing (NIC), Jülich Supercomputing Centre (JSC), and Institut für Biologische Informationsprozesse (IBI-7: Strukturbiochemie), Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Sezin Yüksel
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Tina Schwabe
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Christian Sattler
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Marco Lelle
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Andrea Schweinitz
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Ralf Schmauder
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Klaus Benndorf
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Holger Gohlke
- John von Neumann-Institut für Computing (NIC), Jülich Supercomputing Centre (JSC), and Institut für Biologische Informationsprozesse (IBI-7: Strukturbiochemie), Forschungszentrum Jülich GmbH, Jülich, Germany. .,Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany. .,Institut für Bio- und Geowissenschaften (IBG-4: Bioinformatik), Forschungszentrum Jülich GmbH, Jülich, Germany.
| | - Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany.
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42
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Ahrari S, Ozturk TN, D'Avanzo N. ION BEHAVIOUR IN THE SELECTIVITY FILTER OF HCN1 CHANNELS. Biophys J 2022; 121:2206-2218. [PMID: 35474263 DOI: 10.1016/j.bpj.2022.04.024] [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: 12/02/2021] [Revised: 02/20/2022] [Accepted: 04/20/2022] [Indexed: 11/26/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated channels (HCNs) are responsible for the generation of pacemaker currents (If or Ih) in cardiac and neuronal cells. Despite the overall structural similarity to voltage-gated potassium (Kv) channels, HCNs show much lower selectivity for K+ over Na+ ions. This increased permeability to Na+ is critical to their role in membrane depolarization. HCNs can also select between Na+ and Li+ ions. Here we investigate the unique ion selectivity properties of HCNs using molecular dynamics simulations. Our simulations suggest that the HCN1 pore is flexible and dilated compared to Kv channels with only one stable ion binding site within the selectivity filter. We also observe that ion coordination and hydration differ within the HCN1 selectivity filter compared to those in Kv and CNG channels. Additionally, the C358T mutation further stabilizes the symmetry of the binding site and provides a more fit space for ion coordination, particularly for Li+. STATEMENT OF SIGNIFICANCE: Hyperpolarization-activated cyclic-nucleotide gated (HCN) channels represent the molecular correlate of the currents If or Ih in cardiomyocytes and neurons. Here we study the unique low conductance and semi-selective properties of HCNs. The conductance and selectivity mechanisms of ion channels are tightly associated with their physiological role and contribute to the specific properties of the excitable cells in which they are expressed.
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Affiliation(s)
- Sajjad Ahrari
- Département de pharmacologie et physiologie, Université de Montréal, 2960 Chemin de la Tour, Montréal, Canada, H3T 1J4
| | - Tugba N Ozturk
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, 223 McDonnell Sciences Building, St. Louis, US, 63110; Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bethesda, Maryland, 20814
| | - Nazzareno D'Avanzo
- Département de pharmacologie et physiologie, Université de Montréal, 2960 Chemin de la Tour, Montréal, Canada, H3T 1J4.
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43
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Bauer D, Wissmann J, Moroni A, Thiel G, Hamacher K. Weak Cation Selectivity in HCN Channels Results From K +-Mediated Release of Na + From Selectivity Filter Binding Sites. FUNCTION (OXFORD, ENGLAND) 2022; 3:zqac019. [PMID: 36156894 PMCID: PMC9492253 DOI: 10.1093/function/zqac019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/04/2022] [Accepted: 04/11/2022] [Indexed: 01/07/2023]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate the pacemaker current which plays an important role in the timing of various biological processes like the heart beat. We used umbrella sampling to explore the potential of mean force for the conduction of potassium and sodium through the open HCN4 pore. Our data explain distinct functional features like low unitary conductance and weak selectivity as a result of high energetic barriers inside the selectivity filter of this channel. They exceed the 3-5 kJ/mol threshold which is presumed as maximal barrier for diffusion-limited conductance. Furthermore, simulations provide a thermodynamic explanation for the weak cation selectivity of HCN channels that contain only two ion binding sites in the selectivity filter (SF). We find that sodium ions bind more strongly to the SF than potassium and are easier released by binding of potassium than of another sodium. Hence ion transport and selectivity in HCN channels is not determined by the same mechanism as in potassium-selective channels; it rather relies on sodium as a weak blocker that can only be released by potassium.
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Affiliation(s)
- Daniel Bauer
- Department of Biology and Centre for Synthetic Biology, TU Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Jan Wissmann
- Department of Physics, TU Darmstadt, Schlossgartenstrasse 7, 64289 Darmstadt, Germany
| | - Anna Moroni
- Department of Biosciences, University of Milan, via Celoria 26, 20133 Milan, Italy
| | | | - Kay Hamacher
- Department of Biology and Centre for Synthetic Biology, TU Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany,Department of Physics, TU Darmstadt, Schlossgartenstrasse 7, 64289 Darmstadt, Germany
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Wisedchaisri G, Gamal El-Din TM. Druggability of Voltage-Gated Sodium Channels-Exploring Old and New Drug Receptor Sites. Front Pharmacol 2022; 13:858348. [PMID: 35370700 PMCID: PMC8968173 DOI: 10.3389/fphar.2022.858348] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 03/01/2022] [Indexed: 01/12/2023] Open
Abstract
Voltage-gated ion channels are important drug targets because they play crucial physiological roles in both excitable and non-excitable cells. About 15% of clinical drugs used for treating human diseases target ion channels. However, most of these drugs do not provide sufficient specificity to a single subtype of the channels and their off-target side effects can be serious and sometimes fatal. Recent advancements in imaging techniques have enabled us for the first time to visualize unique and hidden parts of voltage-gated sodium channels in different structural conformations, and to develop drugs that further target a selected functional state in each channel subtype with the potential for high precision and low toxicity. In this review we describe the druggability of voltage-gated sodium channels in distinct functional states, which could potentially be used to selectively target the channels. We review classical drug receptors in the channels that have recently been structurally characterized by cryo-electron microscopy with natural neurotoxins and clinical drugs. We further examine recent drug discoveries for voltage-gated sodium channels and discuss opportunities to use distinct, state-dependent receptor sites in the voltage sensors as unique drug targets. Finally, we explore potential new receptor sites that are currently unknown for sodium channels but may be valuable for future drug discovery. The advancement presented here will help pave the way for drug development that selectively targets voltage-gated sodium channels.
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Affiliation(s)
- Goragot Wisedchaisri
- Department of Pharmacology, University of Washington, Seattle, WA, United States
| | - Tamer M Gamal El-Din
- Department of Pharmacology, University of Washington, Seattle, WA, United States
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Claveras Cabezudo A, Feriel Khoualdi A, D’Avanzo N. Computational Prediction of Phosphoinositide Binding to Hyperpolarization-Activated Cyclic-Nucleotide Gated Channels. Front Physiol 2022; 13:859087. [PMID: 35399260 PMCID: PMC8990809 DOI: 10.3389/fphys.2022.859087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 02/25/2022] [Indexed: 12/31/2022] Open
Abstract
Protein-lipid interactions are key regulators of ion channel function. Numerous ion channels, including hyperpolarization-activated cyclic-nucleotide gated (HCN) channels have been shown to be regulated by phosphoinositides (PIPs), with important implications in cardiac and neuronal function. Specifically, PIPs have been shown to enhance HCN activation. Using computational approaches, we aim to identify potential binding sites for HCN1-PIP interactions. Computational docking and coarse-grained simulations indicate that PIP binding to HCN1 channels is not well coordinated, but rather occurs over a broad surface of charged residues primarily in the HCN-domain, S2 and S3 helices that can be loosely organized in 2 or 3 overlapping clusters. Thus, PIP-HCN1 interactions are more resembling of electrostatic interactions that occur in myristoylated alanine-rich C kinase substrate (MARCKS) proteins, than the specifically coordinated interactions that occur in pleckstrin homology domains (PH domains) or ion channels such as inward rectifier potassium (Kir) channels. Our results also indicate that phosphatidylinositol (PI) interactions with HCN1 are even lower affinity, explaining why unphosphorylated PI have no effect on HCN1 activation unlike phosphorylated PIPs.
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Affiliation(s)
- Ainara Claveras Cabezudo
- Institute of Pharmacy and Molecular Biotechnology (IPMB), Heidelberg University, Heidelberg, Germany
- Département de Pharmacologie et Physiologie, Université de Montréal, Montréal, QC, Canada
| | - Asma Feriel Khoualdi
- Département de Pharmacologie et Physiologie, Université de Montréal, Montréal, QC, Canada
| | - Nazzareno D’Avanzo
- Département de Pharmacologie et Physiologie, Université de Montréal, Montréal, QC, Canada
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Chen J, Vishweshwaraiah YL, Dokholyan NV. Design and engineering of allosteric communications in proteins. Curr Opin Struct Biol 2022; 73:102334. [PMID: 35180676 PMCID: PMC8957532 DOI: 10.1016/j.sbi.2022.102334] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/30/2021] [Accepted: 01/05/2022] [Indexed: 01/26/2023]
Abstract
Allostery in proteins plays an important role in regulating protein activities and influencing many biological processes such as gene expression, enzyme catalysis, and cell signaling. The process of allostery takes place when a signal detected at a site on a protein is transmitted via a mechanical pathway to a functional site and, thus, influences its activity. The pathway of allosteric communication consists of amino acids that form a network with covalent and non-covalent bonds. By mutating residues in this allosteric network, protein engineers have successfully established novel allosteric pathways to achieve desired properties in the target protein. In this review, we highlight the most recent and state-of-the-art techniques for allosteric communication engineering. We also discuss the challenges that need to be overcome and future directions for engineering protein allostery.
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Affiliation(s)
- Jiaxing Chen
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA. https://twitter.com/JiaxingChen18
| | - Yashavantha L Vishweshwaraiah
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA. https://twitter.com/IAmYashHegde
| | - Nikolay V Dokholyan
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA; Department of Biochemistry & Molecular Biology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA; Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA; Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, 16802, USA.
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Structural and functional approaches to studying cAMP regulation of HCN channels. Biochem Soc Trans 2021; 49:2573-2579. [PMID: 34812892 DOI: 10.1042/bst20210290] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/19/2021] [Accepted: 10/25/2021] [Indexed: 11/17/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are primarily activated by voltage and further modulated by cAMP. While cAMP binding alone does not open the channel, its presence facilitates the action of voltage, increasing channel open probability. Functional results indicate that the membrane-based voltage sensor domain (VSD) communicates with the cytosolic cyclic nucleotide-binding domain (CNBD), and vice-versa. Yet, a mechanistic explanation on how this could occur in structural terms is still lacking. In this review, we will discuss the recent advancement in understanding the molecular mechanisms connecting the VSD with the CNBD in the tetrameric organization of HCN channels unveiled by the 3D structures of HCN1 and HCN4. Data show that the HCN domain transmits cAMP signal to the VSD by bridging the cytosolic to the membrane domains. Furthermore, a metal ion coordination site connects the C-linker to the S4-S5 linker in HCN4, further facilitating cAMP signal transmission to the VSD in this isoform.
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Voltage-gating and cytosolic Ca 2+ activation mechanisms of Arabidopsis two-pore channel AtTPC1. Proc Natl Acad Sci U S A 2021; 118:2113946118. [PMID: 34845029 DOI: 10.1073/pnas.2113946118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2021] [Indexed: 11/18/2022] Open
Abstract
Arabidopsis thaliana two-pore channel AtTPC1 is a voltage-gated, Ca2+-modulated, nonselective cation channel that is localized in the vacuolar membrane and responsible for generating slow vacuolar (SV) current. Under depolarizing membrane potential, cytosolic Ca2+ activates AtTPC1 by binding at the EF-hand domain, whereas luminal Ca2+ inhibits the channel by stabilizing the voltage-sensing domain II (VSDII) in the resting state. Here, we present 2.8 to 3.3 Å cryoelectron microscopy (cryo-EM) structures of AtTPC1 in two conformations, one in closed conformation with unbound EF-hand domain and resting VSDII and the other in a partially open conformation with Ca2+-bound EF-hand domain and activated VSDII. Structural comparison between the two different conformations allows us to elucidate the structural mechanisms of voltage gating, cytosolic Ca2+ activation, and their coupling in AtTPC1. This study also provides structural insight into the general voltage-gating mechanism among voltage-gated ion channels.
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Xiao HL, Xiao YJ, Wang Q, Chen ML, Jiang AL. Moxibustion Regulates Gastrointestinal Motility via HCN1 in Functional Dyspepsia Rats. Med Sci Monit 2021; 27:e932885. [PMID: 34845181 PMCID: PMC8642983 DOI: 10.12659/msm.932885] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Background Moxibustion therapy has been found to ameliorate clinical symptoms of functional dyspepsia (FD). We aimed to examine the regulatory effect of moxibustion on the gastrointestinal (GI) motility in FD and explore the underlying mechanism based on the hyperpolarization-activated cyclic nucleotide-gated cation channel 1 (HCN1). Material/Methods Moxibustion therapy was used in FD rats induced by using classic tail-pinch and irregular feeding. Weight gain and food intake were recorded weekly, followed by detecting gastric residual rate (GRR) and small intestine propulsion rate (IPR). Next, western blotting was performed to determine the expression levels of HCN1 in the gastric antrum. qRT-PCR was used to detect HCN1 in the small intestine and hypothalamic satiety center. Double immunolabeling was used for HCN1 and ICCs in gastric antrum and small intestine. Results The obtained results suggested that moxibustion treatment could increase weight gain and food intake in FD rats. The GRR and IPR were compared among the groups, which showed that moxibustion treatment could decrease GRR and increase IPR. Moxibustion increased the expression of HCN1 in the gastric antrum, small intestine, and hypothalamic satiety center. Histologically, the co-expressions of HCN1 and ICCs tended to increase in gastric antrum and small intestine. Meanwhile, HCN channel inhibitor ZD7288 prevented the above-mentioned therapeutic effects of moxibustion. Conclusions The results of the present study suggest that moxibustion can effectively improve the GI motility of FD rats, which may be related to the upregulation of HCN1 expression in gastric antrum, small intestine, and satiety center.
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Affiliation(s)
- Hong-Ling Xiao
- School of Nursing, Second Military Medical University, Shanghai, China (mainland).,School of Nursing, Tianjin University of Chinese Medicine, Tianjin, China (mainland)
| | - Yun-Jiu Xiao
- School of Nursing, Anhui University of Chinese Medicine, Hefei, Anhui, China (mainland)
| | - Qian Wang
- School of Nursing, Anhui University of Chinese Medicine, Hefei, Anhui, China (mainland)
| | - Mei-Ling Chen
- School of Nursing, Anhui University of Chinese Medicine, Hefei, Anhui, China (mainland)
| | - An-Li Jiang
- School of Nursing, Second Military Medical University, Shanghai, China (mainland)
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Priest MF, Lee EE, Bezanilla F. Tracking the movement of discrete gating charges in a voltage-gated potassium channel. eLife 2021; 10:58148. [PMID: 34779404 PMCID: PMC8635975 DOI: 10.7554/elife.58148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/08/2021] [Indexed: 01/18/2023] Open
Abstract
Positively charged amino acids respond to membrane potential changes to drive voltage sensor movement in voltage-gated ion channels, but determining the displacements of voltage sensor gating charges has proven difficult. We optically tracked the movement of the two most extracellular charged residues (R1 and R2) in the Shaker potassium channel voltage sensor using a fluorescent positively charged bimane derivative (qBBr) that is strongly quenched by tryptophan. By individually mutating residues to tryptophan within the putative pathway of gating charges, we observed that the charge motion during activation is a rotation and a tilted translation that differs between R1 and R2. Tryptophan-induced quenching of qBBr also indicates that a crucial residue of the hydrophobic plug is linked to the Cole-Moore shift through its interaction with R1. Finally, we show that this approach extends to additional voltage-sensing membrane proteins using the Ciona intestinalis voltage-sensitive phosphatase (CiVSP).
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Affiliation(s)
- Michael F Priest
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Elizabeth El Lee
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Francisco Bezanilla
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States.,Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, United States
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