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Chi P, Wang X, Li J, Yang H, Li K, Zhang Y, Lin S, Yu L, Liu S, Chen L, Ren R, Wu J, Huang Z, Geng J, Deng D. Molecular insights into the inhibition of proton-activated chloride channel by transfer RNA. Cell Res 2024; 34:743-745. [PMID: 38942816 DOI: 10.1038/s41422-024-00993-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 06/16/2024] [Indexed: 06/30/2024] Open
Affiliation(s)
- Pengliang Chi
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Xiang Wang
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Jialu Li
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Hui Yang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China
| | - Kaiju Li
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China
- Department of Laboratory Medicine, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, Sichuan, China
| | - Yuqi Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Westlake Laboratory of Life Sciences and Biomedicine, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Shiyi Lin
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Westlake Laboratory of Life Sciences and Biomedicine, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Leiye Yu
- Kobilka Institute of Innovative Drug Discovery, School of Life and Health Sciences, the Chinese University of Hong Kong, Shenzhen, Guangdong, China
- Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Fudan University, Shanghai, China
| | - Shiqi Liu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China
| | - Lu Chen
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Ruobing Ren
- Kobilka Institute of Innovative Drug Discovery, School of Life and Health Sciences, the Chinese University of Hong Kong, Shenzhen, Guangdong, China
- Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Fudan University, Shanghai, China
| | - Jianping Wu
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Westlake Laboratory of Life Sciences and Biomedicine, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China.
| | - Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China.
| | - Jia Geng
- Department of Laboratory Medicine, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, Sichuan, China.
| | - Dong Deng
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China.
- Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Sichuan University, Chengdu, Sichuan, China.
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2
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Ko W, Lee E, Kim JE, Lim HH, Suh BC. The plasma membrane inner leaflet PI(4,5)P 2 is essential for the activation of proton-activated chloride channels. Nat Commun 2024; 15:7008. [PMID: 39143141 PMCID: PMC11324729 DOI: 10.1038/s41467-024-51400-y] [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: 10/07/2023] [Accepted: 08/07/2024] [Indexed: 08/16/2024] Open
Abstract
Proton-activated chloride (PAC) channels, ubiquitously expressed in tissues, regulate intracellular Cl- levels and cell death following acidosis. However, molecular mechanisms and signaling pathways involved in PAC channel modulation are largely unknown. Herein, we determine that phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] of the plasma membrane inner leaflet is essential for the proton activation of PAC channels. PI(4,5)P2 depletion by activating phosphatidylinositol 5-phosphatases or Gq protein-coupled muscarinic receptors substantially inhibits human PAC currents. In excised inside-out patches, PI(4,5)P2 application to the cytoplasmic side increases the currents. Structural simulation reveals that the putative PI(4,5)P2-binding site is localized within the cytosol in resting state but shifts to the cell membrane's inner surface in an activated state and interacts with inner leaflet PI(4,5)P2. Alanine neutralization of basic residues near the membrane-cytosol interface of the transmembrane helice 2 significantly attenuates PAC currents. Overall, our study uncovers a modulatory mechanism of PAC channel through inner membrane PI(4,5)P2.
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Affiliation(s)
- Woori Ko
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
| | - Euna Lee
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
- Neurovascular Unit Research Group, Korea Brain Research Institute (KBRI), Daegu, 41068, Republic of Korea
| | - Jung-Eun Kim
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
| | - Hyun-Ho Lim
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
- Neurovascular Unit Research Group, Korea Brain Research Institute (KBRI), Daegu, 41068, Republic of Korea
| | - Byung-Chang Suh
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea.
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3
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Morse J, Nadiveedhi MR, Schmidt M, Tang FK, Hladun C, Ganesh P, Qiu Z, Leung K. Tunable Cytosolic Chloride Indicators for Real-Time Chloride Imaging in Live Cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.08.606814. [PMID: 39149292 PMCID: PMC11326291 DOI: 10.1101/2024.08.08.606814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
Chloride plays a crucial role in various cellular functions, and its level is regulated by a variety of chloride transporters and channels. However, to date, we still lack the capability to image instantaneous ion flux through chloride channels at single-cell level. Here, we developed a series of cell-permeable, pH-independent, chloride-sensitive fluorophores for real-time cytosolic chloride imaging, which we call CytoCl dyes. We demonstrated the ability of CytoCl dyes to monitor cytosolic chloride and used it to uncover the rapid changes and transient events of halide flux, which cannot be captured by steady-state imaging. Finally, we successfully imaged the proton-activated chloride channel-mediated ion flux at single-cell level, which is, to our knowledge, the first real-time imaging of ion flux through a chloride channel in unmodified cells. By enabling the imaging of single-cell level ion influx through chloride channels and transporters, CytoCl dyes can expand our understanding of ion flux dynamics, which is critical for characterization and modulator screening of these membrane proteins. A conjugable version of CytoCl dyes was also developed for its customization across different applications.
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Affiliation(s)
- Jared Morse
- Department of Chemistry & Biochemistry, Clarkson University, NY 13676, United States
| | | | - Matthias Schmidt
- Department of Chemistry & Biochemistry, Clarkson University, NY 13676, United States
| | - Fung-Kit Tang
- Department of Chemistry & Biochemistry, Clarkson University, NY 13676, United States
| | - Colby Hladun
- Department of Chemistry & Biochemistry, Clarkson University, NY 13676, United States
| | - Prasanna Ganesh
- Department of Chemistry & Biochemistry, Clarkson University, NY 13676, United States
| | - Zhaozhu Qiu
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, MD 21205, United States
| | - Kaho Leung
- Department of Chemistry & Biochemistry, Clarkson University, NY 13676, United States
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4
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Kang H, Han AR, Zhang A, Jeong H, Koh W, Lee JM, Lee H, Jo HY, Maria-Solano MA, Bhalla M, Kwon J, Roh WS, Yang J, An HJ, Choi S, Kim HM, Lee CJ. GolpHCat (TMEM87A), a unique voltage-dependent cation channel in Golgi apparatus, contributes to Golgi-pH maintenance and hippocampus-dependent memory. Nat Commun 2024; 15:5830. [PMID: 38992057 PMCID: PMC11239671 DOI: 10.1038/s41467-024-49297-8] [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: 12/14/2023] [Accepted: 05/30/2024] [Indexed: 07/13/2024] Open
Abstract
Impaired ion channels regulating Golgi pH lead to structural alterations in the Golgi apparatus, such as fragmentation, which is found, along with cognitive impairment, in Alzheimer's disease. However, the causal relationship between altered Golgi structure and cognitive impairment remains elusive due to the lack of understanding of ion channels in the Golgi apparatus of brain cells. Here, we identify that a transmembrane protein TMEM87A, renamed Golgi-pH-regulating cation channel (GolpHCat), expressed in astrocytes and neurons that contributes to hippocampus-dependent memory. We find that GolpHCat displays unique voltage-dependent currents, which is potently inhibited by gluconate. Additionally, we gain structural insights into the ion conduction through GolpHCat at the molecular level by determining three high-resolution cryogenic-electron microscopy structures of human GolpHCat. GolpHCat-knockout mice show fragmented Golgi morphology and altered protein glycosylation and functions in the hippocampus, leading to impaired spatial memory. These findings suggest a molecular target for Golgi-related diseases and cognitive impairment.
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Affiliation(s)
- Hyunji Kang
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
- IBS School, University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea
| | - Ah-Reum Han
- Center for Biomolecular and Cellular Structure, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Aihua Zhang
- Global AI Drug Discovery Center, College of Pharmacy and Graduate School of Pharmaceutical Science, Ewha Womans University, Seoul, 03760, Republic of Korea
| | - Heejin Jeong
- Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, 34134, Korea
| | - Wuhyun Koh
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Jung Moo Lee
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Hayeon Lee
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Hee Young Jo
- Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, 34134, Korea
| | - Miguel A Maria-Solano
- Global AI Drug Discovery Center, College of Pharmacy and Graduate School of Pharmaceutical Science, Ewha Womans University, Seoul, 03760, Republic of Korea
| | - Mridula Bhalla
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Jea Kwon
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Woo Suk Roh
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Jimin Yang
- Center for Biomolecular and Cellular Structure, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - Hyun Joo An
- Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, 34134, Korea
| | - Sun Choi
- Global AI Drug Discovery Center, College of Pharmacy and Graduate School of Pharmaceutical Science, Ewha Womans University, Seoul, 03760, Republic of Korea.
| | - Ho Min Kim
- Center for Biomolecular and Cellular Structure, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea.
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - C Justin Lee
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea.
- IBS School, University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea.
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5
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Howard MK, Hoppe N, Huang XP, Macdonald CB, Mehrota E, Grimes PR, Zahm A, Trinidad DD, English J, Coyote-Maestas W, Manglik A. Molecular basis of proton-sensing by G protein-coupled receptors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.17.590000. [PMID: 38659943 PMCID: PMC11042331 DOI: 10.1101/2024.04.17.590000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Three proton-sensing G protein-coupled receptors (GPCRs), GPR4, GPR65, and GPR68, respond to changes in extracellular pH to regulate diverse physiology and are implicated in a wide range of diseases. A central challenge in determining how protons activate these receptors is identifying the set of residues that bind protons. Here, we determine structures of each receptor to understand the spatial arrangement of putative proton sensing residues in the active state. With a newly developed deep mutational scanning approach, we determined the functional importance of every residue in proton activation for GPR68 by generating ~9,500 mutants and measuring effects on signaling and surface expression. This unbiased screen revealed that, unlike other proton-sensitive cell surface channels and receptors, no single site is critical for proton recognition in GPR68. Instead, a network of titratable residues extend from the extracellular surface to the transmembrane region and converge on canonical class A GPCR activation motifs to activate proton-sensing GPCRs. More broadly, our approach integrating structure and unbiased functional interrogation defines a new framework for understanding the rich complexity of GPCR signaling.
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Affiliation(s)
- Matthew K. Howard
- Tetrad graduate program, University of California, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
- Department of Bioengineering and Therapeutic Science, University of California, San Francisco, CA, USA
| | - Nicholas Hoppe
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
- Biophysics graduate program, University of California, San Francisco, CA, USA
| | - Xi-Ping Huang
- Department of Pharmacology and the National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Christian B. Macdonald
- Department of Bioengineering and Therapeutic Science, University of California, San Francisco, CA, USA
| | - Eshan Mehrota
- Tetrad graduate program, University of California, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
- Medical Scientist Training Program, University of California, San Francisco, CA, USA
| | | | - Adam Zahm
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Donovan D. Trinidad
- Department of Medicine, Division of Infectious Disease, University of California, San Francisco, United States
| | - Justin English
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Willow Coyote-Maestas
- Department of Bioengineering and Therapeutic Science, University of California, San Francisco, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
- Quantitative Biosciences Institute, University of California, San Francisco, USA
| | - Aashish Manglik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
- Quantitative Biosciences Institute, University of California, San Francisco, USA
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
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6
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Kang H, Lee CJ. Transmembrane proteins with unknown function (TMEMs) as ion channels: electrophysiological properties, structure, and pathophysiological roles. Exp Mol Med 2024; 56:850-860. [PMID: 38556553 PMCID: PMC11059273 DOI: 10.1038/s12276-024-01206-1] [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: 07/06/2023] [Revised: 12/27/2023] [Accepted: 01/19/2024] [Indexed: 04/02/2024] Open
Abstract
A transmembrane (TMEM) protein with an unknown function is a type of membrane-spanning protein expressed in the plasma membrane or the membranes of intracellular organelles. Recently, several TMEM proteins have been identified as functional ion channels. The structures and functions of these proteins have been extensively studied over the last two decades, starting with TMEM16A (ANO1). In this review, we provide a summary of the electrophysiological properties of known TMEM proteins that function as ion channels, such as TMEM175 (KEL), TMEM206 (PAC), TMEM38 (TRIC), TMEM87A (GolpHCat), TMEM120A (TACAN), TMEM63 (OSCA), TMEM150C (Tentonin3), and TMEM43 (Gapjinc). Additionally, we examine the unique structural features of these channels compared to those of other well-known ion channels. Furthermore, we discuss the diverse physiological roles of these proteins in lysosomal/endosomal/Golgi pH regulation, intracellular Ca2+ regulation, spatial memory, cell migration, adipocyte differentiation, and mechanical pain, as well as their pathophysiological roles in Parkinson's disease, cancer, osteogenesis imperfecta, infantile hypomyelination, cardiomyopathy, and auditory neuropathy spectrum disorder. This review highlights the potential for the discovery of novel ion channels within the TMEM protein family and the development of new therapeutic targets for related channelopathies.
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Affiliation(s)
- Hyunji Kang
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea.
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7
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Kashlan OB, Wang XP, Sheng S, Kleyman TR. Epithelial Na + Channels Function as Extracellular Sensors. Compr Physiol 2024; 14:1-41. [PMID: 39109974 PMCID: PMC11309579 DOI: 10.1002/cphy.c230015] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
The epithelial Na + channel (ENaC) resides on the apical surfaces of specific epithelia in vertebrates and plays a critical role in extracellular fluid homeostasis. Evidence that ENaC senses the external environment emerged well before the molecular identity of the channel was reported three decades ago. This article discusses progress toward elucidating the mechanisms through which specific external factors regulate ENaC function, highlighting insights gained from structural studies of ENaC and related family members. It also reviews our understanding of the role of ENaC regulation by the extracellular environment in physiology and disease. After familiarizing the reader with the channel's physiological roles and structure, we describe the central role protein allostery plays in ENaC's sensitivity to the external environment. We then discuss each of the extracellular factors that directly regulate the channel: proteases, cations and anions, shear stress, and other regulators specific to particular extracellular compartments. For each regulator, we discuss the initial observations that led to discovery, studies investigating molecular mechanism, and the physiological and pathophysiological implications of regulation. © 2024 American Physiological Society. Compr Physiol 14:5407-5447, 2024.
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Affiliation(s)
- Ossama B. Kashlan
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Computational and Systems Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania
| | - Xue-Ping Wang
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shaohu Sheng
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Thomas R. Kleyman
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh,
Pittsburgh, Pennsylvania
- Department of Pharmacology and Chemical Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania
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8
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Kappel S, Melek K, Ross-Kaschitza D, Hauert B, Gerber CE, Lochner M, Peinelt C. CBA (4-chloro-2-(2-chlorophenoxy)acetamido) benzoic acid) inhibits TMEM206 mediated currents and TMEM206 does not contribute to acid-induced cell death in colorectal cancer cells. Front Pharmacol 2024; 15:1369513. [PMID: 38515848 PMCID: PMC10955468 DOI: 10.3389/fphar.2024.1369513] [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: 01/12/2024] [Accepted: 02/08/2024] [Indexed: 03/23/2024] Open
Abstract
Introduction: Upon activation at low pH, TMEM206 conducts Cl- ions across plasma and vesicular membranes. In a (patho)physiological context, TMEM206 was reported to contribute to acid-induced cell death in neurons, kidney and cervical epithelial cells. We investigated the role of TMEM206 in acid-induced cell death in colorectal cancer cells. In addition, we studied CBA as a new small molecule inhibitor for TMEM206. Methods: The role of TMEM206 in acid-induced cell death was studied with CRISPR/Cas9-mediated knockout and FACS analysis. The pharmacology of TMEM206 was determined with the patch clamp technique. Results: In colorectal cancer cells, TMEM206 is not a critical mediator of acid-induced cell death. CBA is a small molecule inhibitor of TMEM206 (IC50 = 9.55 µM) at low pH, at pH 6.0 inhibition is limited. Conclusion: CBA demonstrates effective and specific inhibition of TMEM206; however, its inhibitory efficacy is limited at pH 6.0. Despite this limitation, CBA is a potent inhibitor for functional studies at pH 4.5 and may be a promising scaffold for the development of future TMEM206 inhibitors.
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Affiliation(s)
| | | | | | | | | | | | - Christine Peinelt
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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9
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Kostritskaia Y, Klüssendorf M, Pan YE, Hassani Nia F, Kostova S, Stauber T. Physiological Functions of the Volume-Regulated Anion Channel VRAC/LRRC8 and the Proton-Activated Chloride Channel ASOR/TMEM206. Handb Exp Pharmacol 2024; 283:181-218. [PMID: 37468723 DOI: 10.1007/164_2023_673] [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] [Indexed: 07/21/2023]
Abstract
Volume-regulated anion channels (VRACs) and the acid-sensitive outwardly rectifying anion channel (ASOR) mediate flux of chloride and small organic anions. Although known for a long time, they were only recently identified at the molecular level. VRACs are heteromers consisting of LRRC8 proteins A to E. Combining the essential LRRC8A with different LRRC8 paralogues changes key properties of VRAC such as conductance or substrate selectivity, which is how VRACs are involved in multiple physiological functions including regulatory volume decrease, cell proliferation and migration, cell death, purinergic signalling, fat and glucose metabolism, insulin signalling, and spermiogenesis. VRACs are also involved in pathological conditions, such as the neurotoxic release of glutamate and aspartate. Certain VRACs are also permeable to larger, organic anions, including antibiotics and anti-cancer drugs, making them an interesting therapeutic target. ASOR, also named proton-activated chloride channel (PAC), is formed by TMEM206 homotrimers on the plasma membrane and on endosomal compartments where it mediates chloride flux in response to extracytosolic acidification and plays a role in the shrinking and maturation of macropinosomes. ASOR has been shown to underlie neuronal swelling which causes cell death after stroke as well as promoting the metastasis of certain cancers, making them intriguing therapeutic targets as well.
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Affiliation(s)
- Yulia Kostritskaia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Malte Klüssendorf
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Yingzhou Edward Pan
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Fatemeh Hassani Nia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Simona Kostova
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Tobias Stauber
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany.
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10
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Xu F, Yu F. Sensing and regulation of plant extracellular pH. TRENDS IN PLANT SCIENCE 2023; 28:1422-1437. [PMID: 37596188 DOI: 10.1016/j.tplants.2023.06.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 06/03/2023] [Accepted: 06/19/2023] [Indexed: 08/20/2023]
Abstract
In plants, pH determines nutrient acquisition and sensing, and triggers responses to osmotic stress, whereas pH homeostasis protects the cellular machinery. Extracellular pH (pHe) controls the chemistry and rheology of the cell wall to adjust its elasticity and regulate cell expansion in space and time. Plasma membrane (PM)-localized proton pumps, cell-wall components, and cell wall-remodeling enzymes jointly maintain pHe homeostasis. To adapt to their environment and modulate growth and development, plant cells must sense subtle changes in pHe caused by the environment or neighboring cells. Accumulating evidence indicates that PM-localized cell-surface peptide-receptor pairs sense pHe. We highlight recent advances in understanding how plants perceive and maintain pHe, and discuss future perspectives.
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Affiliation(s)
- Fan Xu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha 410082, PR China
| | - Feng Yu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha 410082, PR China.
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11
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Zhao Y, Jiang H, Yu J, Wang L, Du J. Engineered Histidine-Rich Peptides Enhance Endosomal Escape for Antibody-Targeted Intracellular Delivery of Functional Proteins. Angew Chem Int Ed Engl 2023; 62:e202304692. [PMID: 37283024 DOI: 10.1002/anie.202304692] [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: 04/03/2023] [Revised: 06/04/2023] [Accepted: 06/05/2023] [Indexed: 06/08/2023]
Abstract
Currently, the clinical application of protein/peptide therapeutics is mainly limited to the modulation of diseases in extracellular spaces. Intracellular targets are hardly accessed, owing largely to the endosomal entrapment of internalized proteins/peptides. Here, we report a strategy to design and construct peptides that enable endosome-to-cytosol delivery based on an extension of the "histidine switch" principle. By substituting the Arg/Lys residues in cationic cell-penetrating peptides (CPPs) with histidine, we obtained peptides with pH-dependent membrane-perturbation activity. These peptides do not randomly penetrate cells like CPPs, but imitate the endosomal escape of CPPs following cellular uptake. Working with one such 16-residue peptide (hsLMWP) with high endosomal escape capacity, we engineered modular fusion proteins and achieved antibody-targeted delivery of diverse protein cargoes-including the pro-apoptotic protein BID (BH3-interacting domain death agonist) and Cre recombinase-into the cytosol of multiple cancer cell types. After extensive in vitro testing, an in vivo analysis with xenograft mice ultimately demonstrated that a trastuzumab-hsLMWP-BID fusion conferred strong anti-tumor efficacy without apparent side effects. Notably, our fusion protein features a modular design, allowing flexible applications for any antibody/cargo combination of choice. Therefore, the potential applications extend throughout life science and biomedicine, including gene editing, cancer treatment, and immunotherapy.
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Affiliation(s)
- Yan Zhao
- School of Pharmaceutical Sciences, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing, 100084, China
- Peking University-Tsinghua University-National Institute Biological Sciences (PTN) Joint Graduate Program, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Haolin Jiang
- School of Pharmaceutical Sciences, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing, 100084, China
- Academy for Advanced Interdisciplinary Studies (AAIS), Peking University-Tsinghua University-National Institute Biological Sciences (PTN) Joint Graduate Program, Peking University, Beijing, 100871, China
| | - Jiazhen Yu
- School of Pharmaceutical Sciences, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing, 100084, China
| | - Luyao Wang
- School of Pharmaceutical Sciences, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing, 100084, China
| | - Juanjuan Du
- School of Pharmaceutical Sciences, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing, 100084, China
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12
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Zhao P, Tang C, Yang Y, Xiao Z, Perez-Miller S, Zhang H, Luo G, Liu H, Li Y, Liao Q, Yang F, Dong H, Khanna R, Liu Z. A new polymodal gating model of the proton-activated chloride channel. PLoS Biol 2023; 21:e3002309. [PMID: 37713449 PMCID: PMC10529583 DOI: 10.1371/journal.pbio.3002309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 09/27/2023] [Accepted: 08/23/2023] [Indexed: 09/17/2023] Open
Abstract
The proton-activated chloride (PAC) channel plays critical roles in ischemic neuron death, but its activation mechanisms remain elusive. Here, we investigated the gating of PAC channels using its novel bifunctional modulator C77304. C77304 acted as a weak activator of the PAC channel, causing moderate activation by acting on its proton gating. However, at higher concentrations, C77304 acted as a weak inhibitor, suppressing channel activity. This dual function was achieved by interacting with 2 modulatory sites of the channel, each with different affinities and dependencies on the channel's state. Moreover, we discovered a protonation-independent voltage activation of the PAC channel that appears to operate through an ion-flux gating mechanism. Through scanning-mutagenesis and molecular dynamics simulation, we confirmed that E181, E257, and E261 in the human PAC channel serve as primary proton sensors, as their alanine mutations eliminated the channel's proton gating while sparing the voltage-dependent gating. This proton-sensing mechanism was conserved among orthologous PAC channels from different species. Collectively, our data unveils the polymodal gating and proton-sensing mechanisms in the PAC channel that may inspire potential drug development.
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Affiliation(s)
- Piao Zhao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
- Peptide and small molecule drug R&D platform, Furong Laboratory, Hunan Normal University, Changsha, China
| | - Cheng Tang
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
- Peptide and small molecule drug R&D platform, Furong Laboratory, Hunan Normal University, Changsha, China
| | - Yuqin Yang
- Kuang Yaming Honors School, State Key Laboratory of Analytical Chemistry for Life Science, Engineering Research Center of Protein and Peptide Medicine of Ministry of Education, & Institute for Brain Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Zhen Xiao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Samantha Perez-Miller
- Department of Molecular Pathobiology and NYU Pain Research Center, College of Dentistry, New York University, New York, New York, United States of America
| | - Heng Zhang
- Department of Biophysics and Kidney Disease Center, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Guoqing Luo
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Hao Liu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Yaqi Li
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Qingyi Liao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Fan Yang
- Department of Biophysics and Kidney Disease Center, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Hao Dong
- Kuang Yaming Honors School, State Key Laboratory of Analytical Chemistry for Life Science, Engineering Research Center of Protein and Peptide Medicine of Ministry of Education, & Institute for Brain Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Rajesh Khanna
- Department of Molecular Pathobiology and NYU Pain Research Center, College of Dentistry, New York University, New York, New York, United States of America
- Department of Neuroscience and Physiology and Neuroscience Institute, School of Medicine, New York University, New York, New York, United States of America
| | - Zhonghua Liu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
- Peptide and small molecule drug R&D platform, Furong Laboratory, Hunan Normal University, Changsha, China
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13
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Chen GL, Li J, Zhang J, Zeng B. To Be or Not to Be an Ion Channel: Cryo-EM Structures Have a Say. Cells 2023; 12:1870. [PMID: 37508534 PMCID: PMC10378246 DOI: 10.3390/cells12141870] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 07/13/2023] [Accepted: 07/16/2023] [Indexed: 07/30/2023] Open
Abstract
Ion channels are the second largest class of drug targets after G protein-coupled receptors. In addition to well-recognized ones like voltage-gated Na/K/Ca channels in the heart and neurons, novel ion channels are continuously discovered in both excitable and non-excitable cells and demonstrated to play important roles in many physiological processes and diseases such as developmental disorders, neurodegenerative diseases, and cancer. However, in the field of ion channel discovery, there are an unignorable number of published studies that are unsolid and misleading. Despite being the gold standard of a functional assay for ion channels, electrophysiological recordings are often accompanied by electrical noise, leak conductance, and background currents of the membrane system. These unwanted signals, if not treated properly, lead to the mischaracterization of proteins with seemingly unusual ion-conducting properties. In the recent ten years, the technical revolution of cryo-electron microscopy (cryo-EM) has greatly advanced our understanding of the structures and gating mechanisms of various ion channels and also raised concerns about the pore-forming ability of some previously identified channel proteins. In this review, we summarize cryo-EM findings on ion channels with molecular identities recognized or disputed in recent ten years and discuss current knowledge of proposed channel proteins awaiting cryo-EM analyses. We also present a classification of ion channels according to their architectures and evolutionary relationships and discuss the possibility and strategy of identifying more ion channels by analyzing structures of transmembrane proteins of unknown function. We propose that cross-validation by electrophysiological and structural analyses should be essentially required for determining molecular identities of novel ion channels.
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Affiliation(s)
- Gui-Lan Chen
- Key Laboratory of Medical Electrophysiology, Ministry of Education & Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou 646000, China
| | - Jian Li
- College of Pharmaceutical Sciences, Gannan Medical University, Ganzhou 341000, China
| | - Jin Zhang
- School of Basic Medical Sciences, Nanchang University, Nanchang 330031, 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 646000, China
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14
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Song J, Yu Y, Yan Z, Xiao S, Zhao X, Wang F, Fang Q, Ye G. Chloride intracellular channel gene knockdown induces insect cell lines death and level increases of intracellular calcium ions. Front Physiol 2023; 14:1217954. [PMID: 37485065 PMCID: PMC10356983 DOI: 10.3389/fphys.2023.1217954] [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: 05/06/2023] [Accepted: 06/28/2023] [Indexed: 07/25/2023] Open
Abstract
Chloride intracellular channel (CLIC) is a member of the chloride channel protein family for which growing evidence supports a pivotal role in fundamental cellular events. However, the physiological function of CLIC in insects is still rarely uncovered. The ovary-derived High Five (Hi-5) cell line isolated from the cabbage looper (Trichoplusia ni) is widely used in laboratories. Here, we studied both characteristics and functions of CLIC in Hi-5 cells (TnCLIC). We identified the TnCLIC gene in Hi-5 cells and annotated highly conserved CLIC proteins in most insect species. After RNA interference of TnCLIC, the phenomenon of significantly increased cell death suggests that the TnCLIC protein is essential for the survival of Hi-5 cells. The same lethal effect was also observed in Spodoptera frugiperda 9 and Drosophila melanogaster Schneider 2 cells after CLIC knockdown. Furthermore, we found that this kind of cell death was accompanied by increases in intracellular calcium ions after TnCLIC knockdown with the transcriptomic analyses and the detection of calcium levels. Our results provide insights into insect CLIC as a key factor for cell survival and lay the foundation for the cell death mechanism.
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Affiliation(s)
- Jiqiang Song
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Yanping Yu
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Zhichao Yan
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - Shan Xiao
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Xianxin Zhao
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Fang Wang
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Qi Fang
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Gongyin Ye
- State Key Laboratory of Rice Biology and Breeding & Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
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15
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Tam SW, Huffer K, Li M, Swartz KJ. Ion permeation pathway within the internal pore of P2X receptor channels. eLife 2023; 12:84796. [PMID: 36940138 PMCID: PMC10027316 DOI: 10.7554/elife.84796] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 03/07/2023] [Indexed: 03/21/2023] Open
Abstract
P2X receptor channels are trimeric ATP-activated ion channels expressed in neuronal and non-neuronal cells that are attractive therapeutic targets for human disorders. Seven subtypes of P2X receptor channels have been identified in mammals that can form both homomeric and heteromeric channels. P2X1-4 and P2X7 receptor channels are cation-selective, whereas P2X5 has been reported to have both cation and anion permeability. P2X receptor channel structures reveal that each subunit is comprised of two transmembrane helices, with both N-and C-termini on the intracellular side of the membrane and a large extracellular domain that contains the ATP binding sites at subunit interfaces. Recent structures of ATP-bound P2X receptors with the activation gate open reveal the unanticipated presence of a cytoplasmic cap over the central ion permeation pathway, leaving lateral fenestrations that may be largely buried within the membrane as potential pathways for ions to permeate the intracellular end of the pore. In the present study, we identify a critical residue within the intracellular lateral fenestrations that is readily accessible to thiol-reactive compounds from both sides of the membrane and where substitutions influence the relative permeability of the channel to cations and anions. Taken together, our results demonstrate that ions can enter or exit the internal pore through lateral fenestrations that play a critical role in determining the ion selectivity of P2X receptor channels.
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Affiliation(s)
- Stephanie W Tam
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Kate Huffer
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
- Department of Biology, Johns Hopkins University, Baltimore, United States
| | - Mufeng Li
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Kenton J Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
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16
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Identification of the Acid-Sensitive Site Critical for Chloral Hydrate (CH) Activation of the Proton-Activated Chloride Channel. J Neurosci 2023; 43:526-539. [PMID: 36283831 PMCID: PMC9888509 DOI: 10.1523/jneurosci.0482-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 09/22/2022] [Accepted: 09/26/2022] [Indexed: 11/06/2022] Open
Abstract
The transmembrane protein TMEM206 was recently identified as the molecular basis of the extracellular proton-activated Cl- channel (PAC), which plays an essential role in neuronal death in ischemia-reperfusion. The PAC channel is activated by extracellular acid, but the proton-sensitive mechanism remains unclear, although different acid-sensitive pockets have been suggested based on the cryo-EM structure of the human PAC (hPAC) channel. In the present study, we firstly identified two acidic amino acid residues that removed the pH-dependent activation of the hPAC channel by neutralization all the conservative negative charged residues located in the extracellular domain of the hPAC channel and some positively charged residues at the hotspot combined with two-electrode voltage-clamp (TEVC) recording in the Xenopus oocytes system. Double-mutant cycle analysis and double cysteine mutant of these two residues proved that these two residues cooperatively form a proton-sensitive site. In addition, we found that chloral hydrate activates the hPAC channel depending on the normal pH sensitivity of the hPAC channel. Furthermore, the PAC channel knock-out (KO) male mice (C57BL/6J) resist chloral hydrate-induced sedation and hypnosis. Our study provides a molecular basis for understanding the proton-dependent activation mechanism of the hPAC channel and a novel drug target of chloral hydrate.SIGNIFICANCE STATEMENT Proton-activated Cl- channel (PAC) channels are widely distributed in the nervous system and play a vital pathophysiological role in ischemia and endosomal acidification. The main discovery of this paper is that we identified the proton activation mechanism of the human proton-activated chloride channel (hPAC). Intriguingly, we also found that anesthetic chloral hydrate can activate the hPAC channel in a pH-dependent manner. We found that the chloral hydrate activates the hPAC channel and needs the integrity of the pH-sensitive site. In addition, the PAC channel knock-out (KO) mice are resistant to chloral hydrate-induced anesthesia. The study on PAC channels' pH activation mechanism enables us to better understand PAC's biophysical mechanism and provides a novel target of chloral hydrate.
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17
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Mihaljević L, Ruan Z, Osei-Owusu J, Lü W, Qiu Z. Inhibition of the proton-activated chloride channel PAC by PIP 2. eLife 2023; 12:83935. [PMID: 36633397 PMCID: PMC9876566 DOI: 10.7554/elife.83935] [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: 10/04/2022] [Accepted: 12/18/2022] [Indexed: 01/13/2023] Open
Abstract
Proton-activated chloride (PAC) channel is a ubiquitously expressed pH-sensing ion channel, encoded by PACC1 (TMEM206). PAC regulates endosomal acidification and macropinosome shrinkage by releasing chloride from the organelle lumens. It is also found at the cell surface, where it is activated under pathological conditions related to acidosis and contributes to acid-induced cell death. However, the pharmacology of the PAC channel is poorly understood. Here, we report that phosphatidylinositol (4,5)-bisphosphate (PIP2) potently inhibits PAC channel activity. We solved the cryo-electron microscopy structure of PAC with PIP2 at pH 4.0 and identified its putative binding site, which, surprisingly, locates on the extracellular side of the transmembrane domain (TMD). While the overall conformation resembles the previously resolved PAC structure in the desensitized state, the TMD undergoes remodeling upon PIP2-binding. Structural and electrophysiological analyses suggest that PIP2 inhibits the PAC channel by stabilizing the channel in a desensitized-like conformation. Our findings identify PIP2 as a new pharmacological tool for the PAC channel and lay the foundation for future drug discovery targeting this channel.
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Affiliation(s)
- Ljubica Mihaljević
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Zheng Ruan
- Department of Structural Biology, Van Andel InstituteGrand RapidsUnited States
| | - James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Wei Lü
- Department of Structural Biology, Van Andel InstituteGrand RapidsUnited States
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
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18
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Osei-Owusu J, Ruan Z, Mihaljević L, Matasic DS, Chen KH, Lü W, Qiu Z. Molecular mechanism underlying desensitization of the proton-activated chloride channel PAC. eLife 2022; 11:e82955. [PMID: 36547405 PMCID: PMC9779784 DOI: 10.7554/elife.82955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 12/12/2022] [Indexed: 12/24/2022] Open
Abstract
Desensitization is a common property of membrane receptors, including ion channels. The newly identified proton-activated chloride (PAC) channel plays an important role in regulating the pH and size of organelles in the endocytic pathway, and is also involved in acid-induced cell death. However, how the PAC channel desensitizes is largely unknown. Here, we show by patch-clamp electrophysiological studies that PAC (also known as TMEM206/ASOR) undergoes pH-dependent desensitization upon prolonged acid exposure. Through structure-guided and comprehensive mutagenesis, we identified several residues critical for PAC desensitization, including histidine (H) 98, glutamic acid (E) 94, and aspartic acid (D) 91 at the extracellular extension of the transmembrane helix 1 (TM1), as well as E107, D109, and E250 at the extracellular domain (ECD)-transmembrane domain (TMD) interface. Structural analysis and molecular dynamic simulations revealed extensive interactions between residues at the TM1 extension and those at the ECD-TMD interface. These interactions likely facilitate PAC desensitization by stabilizing the desensitized conformation of TM1, which undergoes a characteristic rotational movement from the resting and activated states to the desensitized state. Our studies establish a new paradigm of channel desensitization in this ubiquitously expressed ion channel and pave the way for future investigation of its relevance in cellular physiology and disease.
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Affiliation(s)
- James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Zheng Ruan
- Department of Structural Biology, Van Andel InstituteGrand RapidsUnited States
| | - Ljubica Mihaljević
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Daniel S Matasic
- Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Kevin Hong Chen
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Wei Lü
- Department of Structural Biology, Van Andel InstituteGrand RapidsUnited States
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of MedicineBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
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19
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Chen XC, Zhang H, Liu SH, Zhou Y, Jiang L. Engineering Polymeric Nanofluidic Membranes for Efficient Ionic Transport: Biomimetic Design, Material Construction, and Advanced Functionalities. ACS NANO 2022; 16:17613-17640. [PMID: 36322865 DOI: 10.1021/acsnano.2c07641] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Design elements extracted from biological ion channels guide the engineering of artificial nanofluidic membranes for efficient ionic transport and spawn biomimetic devices with great potential in many cutting-edge areas. In this context, polymeric nanofluidic membranes can be especially attractive because of their inherent flexibility and benign processability, which facilitate massive fabrication and facile device integration for large-scale applications. Herein, the state-of-the-art achievements of polymeric nanofluidic membranes are systematically summarized. Theoretical fundamentals underlying both biological and synthetic ion channels are introduced. The advances of engineering polymeric nanofluidic membranes are then detailed from aspects of structural design, material construction, and chemical functionalization, emphasizing their broad chemical and reticular/topological variety as well as considerable property tunability. After that, this Review expands on examples of evolving these polymeric membranes into macroscopic devices and their potentials in addressing compelling issues in energy conversion and storage systems where efficient ion transport is highly desirable. Finally, a brief outlook on possible future developments in this field is provided.
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Affiliation(s)
- Xia-Chao Chen
- School of Materials Science & Engineering, Zhejiang Sci-Tech University, Hangzhou310018, P. R. China
| | - Hao Zhang
- School of Materials Science & Engineering, Zhejiang Sci-Tech University, Hangzhou310018, P. R. China
| | - Sheng-Hua Liu
- School of Materials Science & Engineering, Zhejiang Sci-Tech University, Hangzhou310018, P. R. China
| | - Yahong Zhou
- CAS Key Laboratory of Bio-inspired Materials and Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing100190, P. R. China
| | - Lei Jiang
- CAS Key Laboratory of Bio-inspired Materials and Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing100190, P. R. China
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20
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The roles of two extracellular loops in proton sensing and permeation in human Otop1 proton channel. Commun Biol 2022; 5:1110. [PMID: 36266567 PMCID: PMC9585144 DOI: 10.1038/s42003-022-04085-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 10/07/2022] [Indexed: 11/08/2022] Open
Abstract
Otopetrin (Otop) proteins were recently found to function as proton channels, with Otop1 revealed to be the sour taste receptor in mammals. Otop proteins contain twelve transmembrane segments (S1-S12) which are divided into structurally similar N and C domains. The mechanisms by which Otop channels sense extracellular protons to initiate gating and conduct protons once the channels are activated remains largely elusive. Here we show that two extracellular loops are playing key roles in human Otop1 channel function. We find that residue H229 in the S5-S6 loop is critical for proton sensing of Otop1. Further, our data reveal that the S11-12 loop is structurally and functionally essential for the Otop1 channel and that residue D570 in this loop regulates proton permeation into the pore formed by the C domain. This study sheds light on the molecular mechanism behind the structure and function of this newly identified ion channel family. Electrophysiology experiments, mutagenesis, and structural modelling provide insights into the structure and function of the sour taste receptor Otopetrin 1.
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21
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Verkest C, Salinas M, Diochot S, Deval E, Lingueglia E, Baron A. Mechanisms of Action of the Peptide Toxins Targeting Human and Rodent Acid-Sensing Ion Channels and Relevance to Their In Vivo Analgesic Effects. Toxins (Basel) 2022; 14:toxins14100709. [PMID: 36287977 PMCID: PMC9612379 DOI: 10.3390/toxins14100709] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 09/30/2022] [Accepted: 10/02/2022] [Indexed: 11/16/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are voltage-independent H+-gated cation channels largely expressed in the nervous system of rodents and humans. At least six isoforms (ASIC1a, 1b, 2a, 2b, 3 and 4) associate into homotrimers or heterotrimers to form functional channels with highly pH-dependent gating properties. This review provides an update on the pharmacological profiles of animal peptide toxins targeting ASICs, including PcTx1 from tarantula and related spider toxins, APETx2 and APETx-like peptides from sea anemone, and mambalgin from snake, as well as the dimeric protein snake toxin MitTx that have all been instrumental to understanding the structure and the pH-dependent gating of rodent and human cloned ASICs and to study the physiological and pathological roles of native ASICs in vitro and in vivo. ASICs are expressed all along the pain pathways and the pharmacological data clearly support a role for these channels in pain. ASIC-targeting peptide toxins interfere with ASIC gating by complex and pH-dependent mechanisms sometimes leading to opposite effects. However, these dual pH-dependent effects of ASIC-inhibiting toxins (PcTx1, mambalgin and APETx2) are fully compatible with, and even support, their analgesic effects in vivo, both in the central and the peripheral nervous system, as well as potential effects in humans.
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Affiliation(s)
- Clément Verkest
- CNRS (Centre National de la Recherche Scientifique), IPMC (Institut de Pharmacologie Moléculaire et Cellulaire), LabEx ICST (Laboratory of Excellence in Ion Channel Science and Therapeutics), FHU InovPain (Fédération Hospitalo-Universitaire “Innovative Solutions in Refractory Chronic Pain”), Université Côte d’Azur, 660 Route des Lucioles, Sophia-Antipolis, 06560 Nice, France
- Department of Anesthesiology, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Miguel Salinas
- CNRS (Centre National de la Recherche Scientifique), IPMC (Institut de Pharmacologie Moléculaire et Cellulaire), LabEx ICST (Laboratory of Excellence in Ion Channel Science and Therapeutics), FHU InovPain (Fédération Hospitalo-Universitaire “Innovative Solutions in Refractory Chronic Pain”), Université Côte d’Azur, 660 Route des Lucioles, Sophia-Antipolis, 06560 Nice, France
| | - Sylvie Diochot
- CNRS (Centre National de la Recherche Scientifique), IPMC (Institut de Pharmacologie Moléculaire et Cellulaire), LabEx ICST (Laboratory of Excellence in Ion Channel Science and Therapeutics), FHU InovPain (Fédération Hospitalo-Universitaire “Innovative Solutions in Refractory Chronic Pain”), Université Côte d’Azur, 660 Route des Lucioles, Sophia-Antipolis, 06560 Nice, France
| | - Emmanuel Deval
- CNRS (Centre National de la Recherche Scientifique), IPMC (Institut de Pharmacologie Moléculaire et Cellulaire), LabEx ICST (Laboratory of Excellence in Ion Channel Science and Therapeutics), FHU InovPain (Fédération Hospitalo-Universitaire “Innovative Solutions in Refractory Chronic Pain”), Université Côte d’Azur, 660 Route des Lucioles, Sophia-Antipolis, 06560 Nice, France
| | - Eric Lingueglia
- CNRS (Centre National de la Recherche Scientifique), IPMC (Institut de Pharmacologie Moléculaire et Cellulaire), LabEx ICST (Laboratory of Excellence in Ion Channel Science and Therapeutics), FHU InovPain (Fédération Hospitalo-Universitaire “Innovative Solutions in Refractory Chronic Pain”), Université Côte d’Azur, 660 Route des Lucioles, Sophia-Antipolis, 06560 Nice, France
| | - Anne Baron
- CNRS (Centre National de la Recherche Scientifique), IPMC (Institut de Pharmacologie Moléculaire et Cellulaire), LabEx ICST (Laboratory of Excellence in Ion Channel Science and Therapeutics), FHU InovPain (Fédération Hospitalo-Universitaire “Innovative Solutions in Refractory Chronic Pain”), Université Côte d’Azur, 660 Route des Lucioles, Sophia-Antipolis, 06560 Nice, France
- Correspondence:
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22
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Osei-Owusu J, Kots E, Ruan Z, Mihaljević L, Chen KH, Tamhaney A, Ye X, Lü W, Weinstein H, Qiu Z. Molecular determinants of pH sensing in the proton-activated chloride channel. Proc Natl Acad Sci U S A 2022; 119:e2200727119. [PMID: 35878032 PMCID: PMC9351481 DOI: 10.1073/pnas.2200727119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 05/31/2022] [Indexed: 01/27/2023] Open
Abstract
In response to acidic pH, the widely expressed proton-activated chloride (PAC) channel opens and conducts anions across cellular membranes. By doing so, PAC plays an important role in both cellular physiology (endosome acidification) and diseases associated with tissue acidosis (acid-induced cell death). Despite the available structural information, how proton binding in the extracellular domain (ECD) leads to PAC channel opening remains largely unknown. Here, through comprehensive mutagenesis and electrophysiological studies, we identified several critical titratable residues, including two histidine residues (H130 and H131) and an aspartic acid residue (D269) at the distal end of the ECD, together with the previously characterized H98 at the transmembrane domain-ECD interface, as potential pH sensors for human PAC. Mutations of these residues resulted in significant changes in pH sensitivity. Some combined mutants also exhibited large basal PAC channel activities at neutral pH. By combining molecular dynamics simulations with structural and functional analysis, we further found that the β12 strand at the intersubunit interface and the associated "joint region" connecting the upper and lower ECDs allosterically regulate the proton-dependent PAC activation. Our studies suggest a distinct pH-sensing and gating mechanism of this new family of ion channels sensitive to acidic environment.
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Affiliation(s)
- James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ekaterina Kots
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY 10065
| | - Zheng Ruan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI 49503
| | - Ljubica Mihaljević
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Kevin Hong Chen
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ami Tamhaney
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Xinyu Ye
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI 49503
| | - Wei Lü
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI 49503
| | - Harel Weinstein
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY 10065
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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23
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Zha XM, Xiong ZG, Simon RP. pH and proton-sensitive receptors in brain ischemia. J Cereb Blood Flow Metab 2022; 42:1349-1363. [PMID: 35301897 PMCID: PMC9274858 DOI: 10.1177/0271678x221089074] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/11/2022] [Accepted: 02/28/2022] [Indexed: 01/01/2023]
Abstract
Extracellular proton concentration is at 40 nM when pH is 7.4. In disease conditions such as brain ischemia, proton concentration can reach µM range. To respond to this increase in extracellular proton concentration, the mammalian brain expresses at least three classes of proton receptors. Acid-sensing ion channels (ASICs) are the main neuronal cationic proton receptor. The proton-activated chloride channel (PAC), which is also known as (aka) acid-sensitive outwardly rectifying anion channel (ASOR; TMEM206), mediates acid-induced chloride currents. Besides proton-activated channels, GPR4, GPR65 (aka TDAG8, T-cell death-associated gene 8), and GPR68 (aka OGR1, ovarian cancer G protein-coupled receptor 1) function as proton-sensitive G protein-coupled receptors (GPCRs). Though earlier studies on these GPCRs mainly focus on peripheral cells, we and others have recently provided evidence for their functional importance in brain injury. Specifically, GPR4 shows strong expression in brain endothelium, GPR65 is present in a fraction of microglia, while GPR68 exhibits predominant expression in brain neurons. Here, to get a better view of brain acid signaling and its contribution to ischemic injury, we will review the recent findings regarding the differential contribution of proton-sensitive GPCRs to cerebrovascular function, neuroinflammation, and neuronal injury following acidosis and brain ischemia.
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Affiliation(s)
- Xiang-ming Zha
- Division of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, Kansas City, MO, USA
| | - Zhi-Gang Xiong
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Roger P Simon
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
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24
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Zeziulia M, Blin S, Schmitt FW, Lehmann M, Jentsch TJ. Proton-gated anion transport governs macropinosome shrinkage. Nat Cell Biol 2022; 24:885-895. [PMID: 35590106 PMCID: PMC9203271 DOI: 10.1038/s41556-022-00912-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 04/05/2022] [Indexed: 01/25/2023]
Abstract
Intracellular organelles change their size during trafficking and maturation. This requires the transport of ions and water across their membranes. Macropinocytosis, a ubiquitous form of endocytosis of particular importance for immune and cancer cells, generates large vacuoles that can be followed optically. Shrinkage of macrophage macropinosomes depends on TPC-mediated Na+ efflux and Cl− exit through unknown channels. Relieving osmotic pressure facilitates vesicle budding, positioning osmotic shrinkage upstream of vesicular sorting and trafficking. Here we identify the missing macrophage Cl− channel as the proton-activated Cl− channel ASOR/TMEM206. ASOR activation requires Na+-mediated depolarization and luminal acidification by redundant transporters including H+-ATPases and CLC 2Cl−/H+ exchangers. As corroborated by mathematical modelling, feedback loops requiring the steep voltage and pH dependencies of ASOR and CLCs render vacuole resolution resilient towards transporter copy numbers. TMEM206 disruption increased albumin-dependent survival of cancer cells. Our work suggests a function for the voltage and pH dependence of ASOR and CLCs, provides a comprehensive model for ion-transport-dependent vacuole maturation and reveals biological roles of ASOR. Zeziulia et al. identify the proton-activated Cl− channel ASOR/TMEM206 as necessary for shrinkage of macropinosomes, which is needed for downstream sorting events.
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Affiliation(s)
- Mariia Zeziulia
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany.,Graduate Program of the Freie Universität Berlin, Berlin, Germany
| | - Sandy Blin
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Franziska W Schmitt
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany.,Graduate Program of the Humboldt Universität Berlin, Berlin, Germany
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Thomas J Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany. .,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany. .,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany.
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25
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Wang C, Polovitskaya MM, Delgado BD, Jentsch TJ, Long SB. Gating choreography and mechanism of the human proton-activated chloride channel ASOR. SCIENCE ADVANCES 2022; 8:eabm3942. [PMID: 35108041 PMCID: PMC8809534 DOI: 10.1126/sciadv.abm3942] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 12/08/2021] [Indexed: 05/25/2023]
Abstract
The proton-activated chloride channel ASOR (TMEM206/PAC) permeates anions across cellular membranes in response to acidification, thereby enhancing acid-induced cell death and regulating endocytosis. The molecular mechanisms of pH-dependent control are not understood, in part because structural information for an activated conformation of ASOR is lacking. Here, we reconstitute function from purified protein and present a 3.1-Å-resolution cryo-electron microscopy structure of human ASOR at acidic pH in an activated conformation. The work contextualizes a previous acidic pH structure as a desensitized conformation. Combined with electrophysiological studies and high-resolution structures of resting and desensitized states, the work reveals mechanisms of proton sensing and ion pore gating. Clusters of extracellular acidic residues function as pH sensors and coalesce when protonated. Ensuing conformational changes induce metamorphosis of transmembrane helices to fashion an ion conduction pathway unique to the activated conformation. The studies identify a new paradigm of channel gating in this ubiquitous ion channel.
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Affiliation(s)
- Chongyuan Wang
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Maya M. Polovitskaya
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), D-13125 Berlin, Germany
| | - Bryce D. Delgado
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
- Graduate Program in Biochemistry and Structural Biology, Cell and Developmental Biology, and Molecular Biology, Weill Cornell Medicine Graduate School of Medical Sciences, New York, NY 10065, USA
| | - Thomas J. Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), D-13125 Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, D-10117 Berlin, Germany
| | - Stephen B. Long
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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26
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Okada Y, Sabirov RZ, Merzlyak PG, Numata T, Sato-Numata K. Properties, Structures, and Physiological Roles of Three Types of Anion Channels Molecularly Identified in the 2010's. Front Physiol 2022; 12:805148. [PMID: 35002778 PMCID: PMC8733619 DOI: 10.3389/fphys.2021.805148] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/06/2021] [Indexed: 11/24/2022] Open
Abstract
Molecular identification was, at last, successfully accomplished for three types of anion channels that are all implicated in cell volume regulation/dysregulation. LRRC8A plus LRRC8C/D/E, SLCO2A1, and TMEM206 were shown to be the core or pore-forming molecules of the volume-sensitive outwardly rectifying anion channel (VSOR) also called the volume-regulated anion channel (VRAC), the large-conductance maxi-anion channel (Maxi-Cl), and the acid-sensitive outwardly rectifying anion channel (ASOR) also called the proton-activated anion channel (PAC) in 2014, 2017, and 2019, respectively. More recently in 2020 and 2021, we have identified the S100A10-annexin A2 complex and TRPM7 as the regulatory proteins for Maxi-Cl and VSOR/VRAC, respectively. In this review article, we summarize their biophysical and structural properties as well as their physiological roles by comparing with each other on the basis of their molecular insights. We also point out unsolved important issues to be elucidated soon in the future.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), Okazaki, Japan.,Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan.,Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan.,Cardiovascular Research Institute, Yokohama City University, Yokohama, Japan
| | - Ravshan Z Sabirov
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Petr G Merzlyak
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Tomohiro Numata
- Department of Integrative Physiology, Graduate School of Medicine, Akita University, Akita, Japan
| | - Kaori Sato-Numata
- Department of Integrative Physiology, Graduate School of Medicine, Akita University, Akita, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
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27
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Teng B, Kaplan JP, Liang Z, Krieger Z, Tu YH, Burendei B, Ward AB, Liman ER. Structural motifs for subtype-specific pH-sensitive gating of vertebrate otopetrin proton channels. eLife 2022; 11:77946. [PMID: 35920807 PMCID: PMC9348849 DOI: 10.7554/elife.77946] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 07/19/2022] [Indexed: 01/05/2023] Open
Abstract
Otopetrin (OTOP) channels are proton-selective ion channels conserved among vertebrates and invertebrates, with no structural similarity to other ion channels. There are three vertebrate OTOP channels (OTOP1, OTOP2, and OTOP3), of which one (OTOP1) functions as a sour taste receptor. Whether extracellular protons gate OTOP channels, in addition to permeating them, was not known. Here, we compare the functional properties of the three murine OTOP channels using patch-clamp recording and cytosolic pH microfluorimetry. We find that OTOP1 and OTOP3 are both steeply activated by extracellular protons, with thresholds of pHo <6.0 and 5.5, respectively, and kinetics that are pH-dependent. In contrast, OTOP2 channels are broadly active over a large pH range (pH 5 pH 10) and carry outward currents in response to extracellular alkalinization (>pH 9.0). Strikingly, we could change the pH-sensitive gating of OTOP2 and OTOP3 channels by swapping extracellular linkers that connect transmembrane domains. Swaps of extracellular linkers in the N domain, comprising transmembrane domains 1-6, tended to change the relative conductance at alkaline pH of chimeric channels, while swaps within the C domain, containing transmembrane domains 7-12, tended to change the rates of OTOP3 current activation. We conclude that members of the OTOP channel family are proton-gated (acid-sensitive) proton channels and that the gating apparatus is distributed across multiple extracellular regions within both the N and C domains of the channels. In addition to the taste system, OTOP channels are expressed in the vertebrate vestibular and digestive systems. The distinct gating properties we describe may allow them to subserve varying cell-type specific functions in these and other biological systems.
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Affiliation(s)
- Bochuan Teng
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Joshua P Kaplan
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Ziyu Liang
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Zachary Krieger
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States
| | - Yu-Hsiang Tu
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaUnited States
| | - Batuujin Burendei
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Emily R Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
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28
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Cai R, Tang J, Chen XZ. Ion permeation controlled by hydrophobic residues and proton binding in the proton-activated chloride channel. iScience 2021; 24:103395. [PMID: 34825147 PMCID: PMC8605177 DOI: 10.1016/j.isci.2021.103395] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 07/13/2021] [Accepted: 10/28/2021] [Indexed: 01/17/2023] Open
Abstract
Recently identified proton-activated chloride channel (PAC) contains two transmembrane helices (S1–S2) and is involved in lysosome function, hypoxia adaption, stroke, and carcinogenesis. Although a PAC structure was recently resolved, its gating and activation mechanisms remained largely unknown. By the two-electrode voltage clamp electrophysiology in Xenopus oocytes, we found that the hydrophobicity of site 304 at fenestrations, but not that of neighbor sites, is important for maintaining PAC at a closed state at pH 7.5. When activated at acidic pH, PAC activity significantly increased with the hydrophilicity of site 307 within S2, but not with that of neighbor sites, suggesting that 307 acts as an activation gate. We identified six conserved protonatable residues critical for proton-induced activation, consistent with structural studies. Our study depicted a scheme in which proton binding induces conformational changes from the W304-controlled closed state at fenestrations to an activated state controlled by activation gate I307 in helix S2. The hydrophobicity of site 304 is critical for maintaining PAC at a closed state The function of activated PAC is modulated by the hydrophilicity of site 307 Six protonatable amino acids are involved in proton-induced PAC activation H+ binding seem to change PAC from W304-controlled closed to I307-gated open state
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Affiliation(s)
- Ruiqi Cai
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Jingfeng Tang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, Hubei 430086, China
- Corresponding author
| | - Xing-Zhen Chen
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
- Corresponding author
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29
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Heusser SA, Pless SA. Acid-sensing ion channels as potential therapeutic targets. Trends Pharmacol Sci 2021; 42:1035-1050. [PMID: 34674886 DOI: 10.1016/j.tips.2021.09.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 09/13/2021] [Accepted: 09/14/2021] [Indexed: 11/16/2022]
Abstract
Tissue acidification is associated with a variety of disease states, and acid-sensing ion channels (ASICs) that can sense changes in pH have gained traction as possible pharmaceutical targets. An array of modulators, ranging from small molecules to large biopharmaceuticals, are known to inhibit ASICs. Here, we summarize recent insights from animal studies to assess the therapeutic potential of ASICs in disorders such as ischemic stroke, various pain-related processes, anxiety, and cardiac pathologies. We also review the factors that present a challenge in the pharmacological targeting of ASICs, and which need to be taken into careful consideration when developing potent and selective modulators in the future.
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Affiliation(s)
- Stephanie A Heusser
- Department for Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Stephan A Pless
- Department for Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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30
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Dossi E, Rouach N. Pannexin 1 channels and ATP release in epilepsy: two sides of the same coin : The contribution of pannexin-1, connexins, and CALHM ATP-release channels to purinergic signaling. Purinergic Signal 2021; 17:533-548. [PMID: 34495463 DOI: 10.1007/s11302-021-09818-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/08/2021] [Indexed: 11/29/2022] Open
Abstract
Purinergic signaling mediated by ATP and its metabolites contributes to various brain physiological processes as well as to several pathological conditions, including neurodegenerative and neurological disorders, such as epilepsy. Among the different ATP release pathways, pannexin 1 channels represent one of the major conduits being primarily activated in pathological contexts. Investigations on in vitro and in vivo models of epileptiform activity and seizures in mice and human tissues revealed pannexin 1 involvement in aberrant network activity and epilepsy, and highlighted that pannexin 1 exerts a complex role. Pannexin 1 can indeed either sustain seizures through release of ATP that can directly activate purinergic receptors, or tune down epileptic activity via ATP-derived adenosine that decreases neuronal excitability. Interestingly, in-depth analysis of the literature unveils that this dichotomy is only apparent, as it depends on the model of seizure induction and the type of evoked epileptiform activity, two factors that can differentially activate pannexin 1 channels and trigger distinct intracellular signaling cascades. Here, we review the general properties and ATP permeability of pannexin 1 channels, and discuss their impact on acute epileptiform activity and chronic epilepsy according to the regime of activity and disease state. These data pave the way for the development of new antiepileptic strategies selectively targeting pannexin 1 channels in a context-dependent manner.
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Affiliation(s)
- Elena Dossi
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé Et de la Recherche Médicale U1050, Collège de France, Labex Memolife, Université PSL, Paris, France.
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé Et de la Recherche Médicale U1050, Collège de France, Labex Memolife, Université PSL, Paris, France.
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31
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Couch T, Berger K, Kneisley DL, McCullock TW, Kammermeier P, Maclean DM. Topography and motion of acid-sensing ion channel intracellular domains. eLife 2021; 10:68955. [PMID: 34292153 PMCID: PMC8341984 DOI: 10.7554/elife.68955] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 07/21/2021] [Indexed: 01/12/2023] Open
Abstract
Acid-sensing ion channels (ASICs) are trimeric cation-selective channels activated by decreases in extracellular pH. The intracellular N and C terminal tails of ASIC1 influence channel gating, trafficking, and signaling in ischemic cell death. Despite several X-ray and cryo-EM structures of the extracellular and transmembrane segments of ASIC1, these important intracellular tails remain unresolved. Here, we describe the coarse topography of the chicken ASIC1 intracellular domains determined by fluorescence resonance energy transfer (FRET), measured using either fluorescent lifetime imaging or patch clamp fluorometry. We find the C terminal tail projects into the cytosol by approximately 35 Å and that the N and C tails from the same subunits are closer than adjacent subunits. Using pH-insensitive fluorescent proteins, we fail to detect any relative movement between the N and C tails upon extracellular acidification but do observe axial motions of the membrane proximal segments toward the plasma membrane. Taken together, our study furnishes a coarse topographic map of the ASIC intracellular domains while providing directionality and context to intracellular conformational changes induced by extracellular acidification.
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Affiliation(s)
- Tyler Couch
- Graduate Program in Cellular and Molecular Pharmacology and Physiology, Reno, United States
| | - Kyle Berger
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, United States
| | - Dana L Kneisley
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, United States
| | - Tyler W McCullock
- Graduate Program in Cellular and Molecular Pharmacology and Physiology, Reno, United States
| | - Paul Kammermeier
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, United States
| | - David M Maclean
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, United States
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32
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Okada Y, Sato-Numata K, Sabirov RZ, Numata T. Cell Death Induction and Protection by Activation of Ubiquitously Expressed Anion/Cation Channels. Part 2: Functional and Molecular Properties of ASOR/PAC Channels and Their Roles in Cell Volume Dysregulation and Acidotoxic Cell Death. Front Cell Dev Biol 2021; 9:702317. [PMID: 34307382 PMCID: PMC8299559 DOI: 10.3389/fcell.2021.702317] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/18/2021] [Indexed: 12/18/2022] Open
Abstract
For survival and functions of animal cells, cell volume regulation (CVR) is essential. Major hallmarks of necrotic and apoptotic cell death are persistent cell swelling and shrinkage, and thus they are termed the necrotic volume increase (NVI) and the apoptotic volume decrease (AVD), respectively. A number of ubiquitously expressed anion and cation channels play essential roles not only in CVR but also in cell death induction. This series of review articles address the question how cell death is induced or protected with using ubiquitously expressed ion channels such as swelling-activated anion channels, acid-activated anion channels, and several types of TRP cation channels including TRPM2 and TRPM7. In the Part 1, we described the roles of swelling-activated VSOR/VRAC anion channels. Here, the Part 2 focuses on the roles of the acid-sensitive outwardly rectifying (ASOR) anion channel, also called the proton-activated chloride (PAC) anion channel, which is activated by extracellular protons in a manner sharply dependent on ambient temperature. First, we summarize phenotypical properties, the molecular identity, and the three-dimensional structure of ASOR/PAC. Second, we highlight the unique roles of ASOR/PAC in CVR dysfunction and in the induction of or protection from acidotoxic cell death under acidosis and ischemic conditions.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), Okazaki, Japan.,Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan.,Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Kaori Sato-Numata
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
| | - Ravshan Z Sabirov
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Tomohiro Numata
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan
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Ritter M, Bresgen N, Kerschbaum HH. From Pinocytosis to Methuosis-Fluid Consumption as a Risk Factor for Cell Death. Front Cell Dev Biol 2021; 9:651982. [PMID: 34249909 PMCID: PMC8261248 DOI: 10.3389/fcell.2021.651982] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/29/2021] [Indexed: 12/11/2022] Open
Abstract
The volumes of a cell [cell volume (CV)] and its organelles are adjusted by osmoregulatory processes. During pinocytosis, extracellular fluid volume equivalent to its CV is incorporated within an hour and membrane area equivalent to the cell's surface within 30 min. Since neither fluid uptake nor membrane consumption leads to swelling or shrinkage, cells must be equipped with potent volume regulatory mechanisms. Normally, cells respond to outwardly or inwardly directed osmotic gradients by a volume decrease and increase, respectively, i.e., they shrink or swell but then try to recover their CV. However, when a cell death (CD) pathway is triggered, CV persistently decreases in isotonic conditions in apoptosis and it increases in necrosis. One type of CD associated with cell swelling is due to a dysfunctional pinocytosis. Methuosis, a non-apoptotic CD phenotype, occurs when cells accumulate too much fluid by macropinocytosis. In contrast to functional pinocytosis, in methuosis, macropinosomes neither recycle nor fuse with lysosomes but with each other to form giant vacuoles, which finally cause rupture of the plasma membrane (PM). Understanding methuosis longs for the understanding of the ionic mechanisms of cell volume regulation (CVR) and vesicular volume regulation (VVR). In nascent macropinosomes, ion channels and transporters are derived from the PM. Along trafficking from the PM to the perinuclear area, the equipment of channels and transporters of the vesicle membrane changes by retrieval, addition, and recycling from and back to the PM, causing profound changes in vesicular ion concentrations, acidification, and-most importantly-shrinkage of the macropinosome, which is indispensable for its proper targeting and cargo processing. In this review, we discuss ion and water transport mechanisms with respect to CVR and VVR and with special emphasis on pinocytosis and methuosis. We describe various aspects of the complex mutual interplay between extracellular and intracellular ions and ion gradients, the PM and vesicular membrane, phosphoinositides, monomeric G proteins and their targets, as well as the submembranous cytoskeleton. Our aim is to highlight important cellular mechanisms, components, and processes that may lead to methuotic CD upon their derangement.
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Affiliation(s)
- Markus Ritter
- Center for Physiology, Pathophysiology and Biophysics, Institute for Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
- Institute for Physiology and Pathophysiology, Paracelsus Medical University, Nuremberg, Germany
- Gastein Research Institute, Paracelsus Medical University, Salzburg, Austria
- Ludwig Boltzmann Institute for Arthritis und Rehabilitation, Salzburg, Austria
- Kathmandu University School of Medical Sciences, Dhulikhel, Nepal
| | - Nikolaus Bresgen
- Department of Biosciences, University of Salzburg, Salzburg, Austria
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34
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Amphipathic environments for determining the structure of membrane proteins by single-particle electron cryo-microscopy. Q Rev Biophys 2021; 54:e6. [PMID: 33785082 DOI: 10.1017/s0033583521000044] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past decade, the structural biology of membrane proteins (MPs) has taken a new turn thanks to epoch-making technical progress in single-particle electron cryo-microscopy (cryo-EM) as well as to improvements in sample preparation. The present analysis provides an overview of the extent and modes of usage of the various types of surfactants for cryo-EM studies. Digitonin, dodecylmaltoside, protein-based nanodiscs, lauryl maltoside-neopentyl glycol, glyco-diosgenin, and amphipols (APols) are the most popular surfactants at the vitrification step. Surfactant exchange is frequently used between MP purification and grid preparation, requiring extensive optimization each time the study of a new MP is undertaken. The variety of both the surfactants and experimental approaches used over the past few years bears witness to the need to continue developing innovative surfactants and optimizing conditions for sample preparation. The possibilities offered by novel APols for EM applications are discussed.
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Fortea E, Accardi A. A quantitative flux assay for the study of reconstituted Cl - channels and transporters. Methods Enzymol 2021; 652:243-272. [PMID: 34059284 DOI: 10.1016/bs.mie.2021.01.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The recent deluge of high-resolution structural information on membrane proteins has not been accompanied by a comparable increase in our ability to functionally interrogate these proteins. Current functional assays often are not quantitative or are performed in conditions that significantly differ from those used in structural experiments, thus limiting the mechanistic correspondence between structural and functional experiments. A flux assay to determine quantitatively the functional properties of purified and reconstituted Cl- channels and transporters in membranes of defined lipid compositions is described. An ion-sensitive electrode is used to measure the rate of Cl- efflux from proteoliposomes reconstituted with the desired protein and the fraction of vesicles containing at least one active protein. These measurements enable the quantitative determination of key molecular parameters such as the unitary transport rate, the fraction of proteins that are active, and the molecular mass of the transport protein complex. The approach is illustrated using CLC-ec1, a CLC-type H+/Cl- exchanger as an example. The assay enables the quantitative study of a wide range of Cl- transporting molecules and proteins whose activity is modulated by ligands, voltage, and membrane composition as well as the investigation of the effects of compounds that directly inhibit or activate the reconstituted transport systems. The present assay is readily adapted to the study of transport systems with diverse substrate specificities and molecular characteristics, and the necessary modifications needed are discussed.
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Affiliation(s)
- Eva Fortea
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, United States
| | - Alessio Accardi
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, United States; Department of Anesthesiology, Weill Cornell Medical College, New York, NY, United States; Department of Biochemistry, Weill Cornell Medical College, New York, NY, United States.
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36
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Deng Z, Zhao Y, Feng J, Zhang J, Zhao H, Rau MJ, Fitzpatrick JAJ, Hu H, Yuan P. Cryo-EM structure of a proton-activated chloride channel TMEM206. SCIENCE ADVANCES 2021; 7:7/9/eabe5983. [PMID: 33627432 PMCID: PMC7904269 DOI: 10.1126/sciadv.abe5983] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 01/08/2021] [Indexed: 05/12/2023]
Abstract
TMEM206 has been recently identified as an evolutionarily conserved chloride channel that underlies ubiquitously expressed, proton-activated, outwardly rectifying anion currents. Here, we report the cryo-electron microscopy structure of pufferfish TMEM206, which forms a trimeric channel, with each subunit comprising two transmembrane segments and a large extracellular domain. An ample vestibule in the extracellular region is accessible laterally from the three side portals. The central pore contains multiple constrictions. A conserved lysine residue near the cytoplasmic end of the inner helix forms the presumed chloride ion selectivity filter. Unprecedentedly, the core structure and assembly closely resemble those of the epithelial sodium channel/degenerin family of sodium channels that are unrelated in amino acid sequence and conduct cations instead of anions. Together with electrophysiology, this work provides insights into ion conduction and gating for a new class of chloride channels that is architecturally distinct from previously characterized chloride channel families.
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Affiliation(s)
- Zengqin Deng
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Yonghui Zhao
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Jing Feng
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Haiyan Zhao
- Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Michael J Rau
- Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - James A J Fitzpatrick
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Hongzhen Hu
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA.
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110, USA
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Osei-Owusu J, Yang J, Leung KH, Ruan Z, Lü W, Krishnan Y, Qiu Z. Proton-activated chloride channel PAC regulates endosomal acidification and transferrin receptor-mediated endocytosis. Cell Rep 2021; 34:108683. [PMID: 33503418 PMCID: PMC7869721 DOI: 10.1016/j.celrep.2020.108683] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 11/19/2020] [Accepted: 12/29/2020] [Indexed: 12/13/2022] Open
Abstract
During vesicular acidification, chloride (Cl−), as the counterion, provides the electrical shunt for proton pumping by the vacuolar H+ ATPase. Intracellular CLC transporters mediate Cl− influx to the endolysosomes through their 2Cl−/H+ exchange activity. However, whole-endolysosomal patch-clamp recording also revealed a mysterious conductance releasing Cl− from the lumen. It remains unknown whether CLCs or other Cl− channels are responsible for this activity. Here, we show that the newly identified proton-activated Cl− (PAC) channel traffics from the plasma membrane to endosomes via the classical YxxL motif. PAC deletion abolishes the endosomal Cl− conductance, raises luminal Cl− level, lowers luminal pH, and increases transferrin receptor-mediated endocytosis. PAC overexpression generates a large endosomal Cl− current with properties similar to those of endogenous conductance, hypo-acidifies endosomal pH, and reduces transferrin uptake. We propose that the endosomal Cl− PAC channel functions as a low pH sensor and prevents hyper-acidification by releasing Cl− from the lumen. Osei-Owusu et al. show that the recently identified proton-activated chloride (PAC) channel traffics from the plasma membrane to endosomes and forms an intracellular organelle Cl− channel. PAC functions as a low pH sensor in endosomes and prevents luminal hyper-acidification.
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Affiliation(s)
- James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Junhua Yang
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ka Ho Leung
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Zheng Ruan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Wei Lü
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Yamuna Krishnan
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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