1
|
Drożdżyk K, Peter M, Dutzler R. Structural features of heteromeric channels composed of CALHM2 and CALHM4 paralogs. eLife 2024; 13:RP96138. [PMID: 38896440 PMCID: PMC11186629 DOI: 10.7554/elife.96138] [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] [Indexed: 06/21/2024] Open
Abstract
The CALHM proteins constitute a family of large pore channels that contains six closely related paralogs in humans. Two family members, CALHM1 and 3, have been associated with the release of ATP during taste sensation. Both proteins form heteromeric channels that activate at positive potential and decreased extracellular Ca2+ concentration. Although the structures of several family members displayed large oligomeric organizations of different size, their function has in most cases remained elusive. Our previous study has identified the paralogs CALHM2, 4 and, 6 to be highly expressed in the placenta and defined their structural properties as membrane proteins exhibiting features of large pore channels with unknown activation properties (Drożdżyk et al., 2020). Here, we investigated whether these placental paralogs would form heteromers and characterized heteromeric complexes consisting of CALHM2 and CALHM4 subunits using specific binders as fiducial markers. Both proteins assemble with different stoichiometries with the largest population containing CALHM2 as the predominant component. In these oligomers, the subunits segregate and reside in their preferred conformation found in homomeric channels. Our study has thus revealed the properties that govern the formation of CALHM heteromers in a process of potential relevance in a cellular context.
Collapse
Affiliation(s)
| | - Martina Peter
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Raimund Dutzler
- Department of Biochemistry, University of ZurichZurichSwitzerland
| |
Collapse
|
2
|
Molton O, Bignucolo O, Kellenberger S. Identification of the modulatory Ca 2+-binding sites of acid-sensing ion channel 1a. Open Biol 2024; 14:240028. [PMID: 38896086 DOI: 10.1098/rsob.240028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 04/28/2024] [Indexed: 06/21/2024] Open
Abstract
Acid-sensing ion channels (ASICs) are neuronal Na+-permeable ion channels activated by extracellular acidification. ASICs are involved in learning, fear sensing, pain sensation and neurodegeneration. Increasing the extracellular Ca2+ concentration decreases the H+ sensitivity of ASIC1a, suggesting a competition for binding sites between H+ and Ca2+ ions. Here, we predicted candidate residues for Ca2+ binding on ASIC1a, based on available structural information and our molecular dynamics simulations. With functional measurements, we identified several residues in cavities previously associated with pH-dependent gating, whose mutation reduced the modulation by extracellular Ca2+ of the ASIC1a pH dependence of activation and desensitization. This occurred likely owing to a disruption of Ca2+ binding. Our results link one of the two predicted Ca2+-binding sites in each ASIC1a acidic pocket to the modulation of channel activation. Mg2+ regulates ASICs in a similar way as does Ca2+. We show that Mg2+ shares some of the binding sites with Ca2+. Finally, we provide evidence that some of the ASIC1a Ca2+-binding sites are functionally conserved in the splice variant ASIC1b. Our identification of divalent cation-binding sites in ASIC1a shows how Ca2+ affects ASIC1a gating, elucidating a regulatory mechanism present in many ion channels.
Collapse
Affiliation(s)
- Ophélie Molton
- Department of Biomedical Sciences, University of Lausanne , 1011 Lausanne, Switzerland
| | | | - Stephan Kellenberger
- Department of Biomedical Sciences, University of Lausanne , 1011 Lausanne, Switzerland
| |
Collapse
|
3
|
Luo T, Wu H, Zhu W, Zhang L, Huang Y, Yang X. Emerging therapies: Potential roles of SGLT2 inhibitors in the management of pulmonary hypertension. Respir Med 2024; 227:107631. [PMID: 38631526 DOI: 10.1016/j.rmed.2024.107631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2024] [Revised: 04/01/2024] [Accepted: 04/07/2024] [Indexed: 04/19/2024]
Abstract
Pulmonary hypertension (PH) is a pathophysiological disorder that may involve multiple clinical conditions and may be associated with a variety of cardiovascular and respiratory diseases. Pulmonary hypertension due to left heart disease (PH-LHD) currently lacks targeted therapies, while Pulmonary arterial hypertension (PAH), despite approved treatments, carries considerable residual risk. Metabolic dysfunction has been linked to the pathogenesis and prognosis of PH through various studies, with emerging metabolic agents offering a potential avenue for improving patient outcomes. Sodium-glucose cotransporter 2 inhibitor (SGLT-2i), a novel hypoglycemic agent, could ameliorate metabolic dysfunction and exert cardioprotective effects. Recent small-scale studies suggest SGLT-2i treatment may improve pulmonary artery pressure in patients with PH-LHD, and the PAH animal model shows that SGLT-2i can reduce pulmonary vascular remodeling and prevent progression in PAH, suggesting potential benefits for patients with PH-LHD and perhaps PAH. This review aims to succinctly review PH's pathophysiology, and the connection between metabolic dysfunction and PH, and investigate the prospective mechanisms of action of SGLT-2i in PH-LHD and PAH management.
Collapse
Affiliation(s)
- Taimin Luo
- Department of Pharmacy, Chengdu Seventh People's Hospital (Affiliated Cancer Hospital of Chengdu Medical College), Chengdu, 610000, China
| | - Hui Wu
- Department of Pharmacy, The Affiliated Hospital, Southwest Medical University, Luzhou, 646000, China; School of Pharmacy, Southwest Medical University, Luzhou, 646000, China
| | - Wanlong Zhu
- Department of Pharmacy, The Affiliated Hospital, Southwest Medical University, Luzhou, 646000, China; Department of Pharmacy, Panzhihua Second People's Hospital, Panzhihua, 617000, China
| | - Liaoyun Zhang
- Department of Pharmacy, Sichuan Provincial Maternity and Child Health Care Hospital & Women's and Children's Hospital, Chengdu, 610000, China
| | - Yilan Huang
- Department of Pharmacy, The Affiliated Hospital, Southwest Medical University, Luzhou, 646000, China; School of Pharmacy, Southwest Medical University, Luzhou, 646000, China.
| | - Xuping Yang
- Department of Pharmacy, The Affiliated Hospital, Southwest Medical University, Luzhou, 646000, China; School of Pharmacy, Southwest Medical University, Luzhou, 646000, China.
| |
Collapse
|
4
|
Puebla M, Muñoz MF, Lillo MA, Contreras JE, Figueroa XF. Control of astrocytic Ca 2+ signaling by nitric oxide-dependent S-nitrosylation of Ca 2+ homeostasis modulator 1 channels. Biol Res 2024; 57:19. [PMID: 38689353 PMCID: PMC11059852 DOI: 10.1186/s40659-024-00503-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 04/18/2024] [Indexed: 05/02/2024] Open
Abstract
BACKGROUND Astrocytes Ca2+ signaling play a central role in the modulation of neuronal function. Activation of metabotropic glutamate receptors (mGluR) by glutamate released during an increase in synaptic activity triggers coordinated Ca2+ signals in astrocytes. Importantly, astrocytes express the Ca2+-dependent nitric oxide (NO)-synthetizing enzymes eNOS and nNOS, which might contribute to the Ca2+ signals by triggering Ca2+ influx or ATP release through the activation of connexin 43 (Cx43) hemichannels, pannexin-1 (Panx-1) channels or Ca2+ homeostasis modulator 1 (CALHM1) channels. Hence, we aim to evaluate the participation of NO in the astrocytic Ca2+ signaling initiated by stimulation of mGluR in primary cultures of astrocytes from rat brain cortex. RESULTS Astrocytes were stimulated with glutamate or t-ACPD and NO-dependent changes in [Ca2+]i and ATP release were evaluated. In addition, the activity of Cx43 hemichannels, Panx-1 channels and CALHM1 channels was also analyzed. The expression of Cx43, Panx-1 and CALHM1 in astrocytes was confirmed by immunofluorescence analysis and both glutamate and t-ACPD induced NO-mediated activation of CALHM1 channels via direct S-nitrosylation, which was further confirmed by assessing CALHM1-mediated current using the two-electrode voltage clamp technique in Xenopus oocytes. Pharmacological blockade or siRNA-mediated inhibition of CALHM1 expression revealed that the opening of these channels provides a pathway for ATP release and the subsequent purinergic receptor-dependent activation of Cx43 hemichannels and Panx-1 channels, which further contributes to the astrocytic Ca2+ signaling. CONCLUSIONS Our findings demonstrate that activation of CALHM1 channels through NO-mediated S-nitrosylation in astrocytes in vitro is critical for the generation of glutamate-initiated astrocytic Ca2+ signaling.
Collapse
Affiliation(s)
- Mariela Puebla
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 8330025, Santiago, Chile
| | - Manuel F Muñoz
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 8330025, Santiago, Chile
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
| | - Mauricio A Lillo
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Jorge E Contreras
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Xavier F Figueroa
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 8330025, Santiago, Chile.
| |
Collapse
|
5
|
Lázaro SF, Tonhati H, Oliveira HR, Silva AA, Scalez DCB, Nascimento AV, Santos DJA, Stefani G, Carvalho IS, Sandoval AF, Brito LF. Genetic parameters and genome-wide association studies for mozzarella and milk production traits, lactation length, and lactation persistency in Murrah buffaloes. J Dairy Sci 2024; 107:992-1021. [PMID: 37730179 DOI: 10.3168/jds.2023-23284] [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: 01/18/2023] [Accepted: 08/30/2023] [Indexed: 09/22/2023]
Abstract
Genetic and genomic analyses of longitudinal traits related to milk production efficiency are paramount for optimizing water buffaloes breeding schemes. Therefore, this study aimed to (1) compare single-trait random regression models under a single-step genomic BLUP setting based on alternative covariance functions (i.e., Wood, Wilmink, and Ali and Schaeffer) to describe milk (MY), fat (FY), protein (PY), and mozzarella (MZY) yields, fat-to-protein ratio (FPR), somatic cell score (SCS), lactation length (LL), and lactation persistency (LP) in Murrah dairy buffaloes (Bubalus bubalis); (2) combine the best functions for each trait under a multiple-trait framework; (3) estimate time-dependent SNP effects for all the studied longitudinal traits; and (4) identify the most likely candidate genes associated with the traits. A total of 323,140 test-day records from the first lactation of 4,588 Murrah buffaloes were made available for the study. The model included the average curve of the population nested within herd-year-season of calving, systematic effects of number of milkings per day, and age at first calving as linear and quadratic covariates, and additive genetic, permanent environment, and residual as random effects. The Wood model had the best goodness of fit based on the deviance information criterion and posterior model probabilities for all traits. Moderate heritabilities were estimated over time for most traits (0.30 ± 0.02 for MY; 0.26 ± 0.03 for FY; 0.45 ± 0.04 for PY; 0.28 ± 0.05 for MZY; 0.13 ± 0.02 for FPR; and 0.15 ± 0.03 for SCS). The heritability estimates for LP ranged from 0.38 ± 0.02 to 0.65 ± 0.03 depending on the trait definition used. Similarly, heritabilities estimated for LL ranged from 0.10 ± 0.01 to 0.14 ± 0.03. The genetic correlation estimates across days in milk (DIM) for all traits ranged from -0.06 (186-215 DIM for MY-SCS) to 0.78 (66-95 DIM for PY-MZY). The SNP effects calculated for the random regression model coefficients were used to estimate the SNP effects throughout the lactation curve (from 5 to 305 d). Numerous relevant genomic regions and candidate genes were identified for all traits, confirming their polygenic nature. The candidate genes identified contribute to a better understanding of the genetic background of milk-related traits in Murrah buffaloes and reinforce the value of incorporating genomic information in their breeding programs.
Collapse
Affiliation(s)
- Sirlene F Lázaro
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | - Humberto Tonhati
- Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | - Hinayah R Oliveira
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Alessandra A Silva
- Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | - Daiane C B Scalez
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - André V Nascimento
- Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | | | - Gabriela Stefani
- Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | - Isabella S Carvalho
- Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | - Amanda F Sandoval
- Department of Animal Science, College of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, 14884-900, SP, Brazil
| | - Luiz F Brito
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907.
| |
Collapse
|
6
|
Javed A, Habib S, Ayub A. Evolution of protein domain repertoires of CALHM6. PeerJ 2024; 12:e16063. [PMID: 38188152 PMCID: PMC10768655 DOI: 10.7717/peerj.16063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 08/18/2023] [Indexed: 01/09/2024] Open
Abstract
Calcium (Ca2 +) homeostasis is essential in conducting various cellular processes including nerve transmission, muscular movement, and immune response. Changes in Ca2 + concentration in the cytoplasm are significant in bringing about various immune responses such as pathogen clearance and apoptosis. Various key players are involved in calcium homeostasis such as calcium binders, pumps, and channels. Sequence-based evolutionary information has recently been exploited to predict the biophysical behaviors of proteins, giving critical clues about their functionality. Ion channels are reportedly the first channels developed during evolution. Calcium homeostasis modulator protein 6 (CALHM6) is one such channel. Comprised of a single domain called Ca_hom_mod, CALHM6 is a stable protein interacting with various other proteins in calcium regulation. No previous attempt has been made to trace the exact evolutionary events in the domain of CALHM6, leaving plenty of room for exploring its evolution across a wide range of organisms. The current study aims to answer the questions by employing a computational-based strategy that used profile Hidden Markov Models (HMMs) to scan for the CALHM6 domain, integrated the data with a time-calibrated phylogenetic tree using BEAST and Mesquite, and visualized through iTOL. Around 4,000 domains were identified, and 14,000 domain gain, loss, and duplication events were observed at the end which also included various protein domains other than CALHM6. The data were analyzed concerning CALHM6 evolution as well as the domain gain, loss, and duplication of its interacting partners: Calpain, Vinculin, protein S100-A7, Thioredoxin, Peroxiredoxin, and Calmodulin-like protein 5. Duplication events of CALHM6 near higher eukaryotes showed its increasing complexity in structure and function. This in-silico phylogenetic approach applied to trace the evolution of CALHM6 was an effective approach to get a better understanding of the protein CALHM6.
Collapse
Affiliation(s)
- Aneela Javed
- Molecular Immunology Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), Islamabad, Pakistan
| | - Sabahat Habib
- Molecular Immunology Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), Islamabad, Pakistan
| | - Aaima Ayub
- Molecular Immunology Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), Islamabad, Pakistan
| |
Collapse
|
7
|
Rajayer SR, Smith SM. Neurovirulent cytokines increase neuronal excitability in a model of coronavirus-induced neuroinflammation. Intensive Care Med Exp 2023; 11:71. [PMID: 37833408 PMCID: PMC10575822 DOI: 10.1186/s40635-023-00557-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 10/04/2023] [Indexed: 10/15/2023] Open
Abstract
BACKGROUND Neurological manifestations of severe coronavirus infections, including SARS-CoV-2, are wide-ranging and may persist following virus clearance. Detailed understanding of the underlying changes in brain function may facilitate the identification of therapeutic targets. We directly tested how neocortical function is impacted by the specific panel of cytokines that occur in coronavirus brain infection. Using the whole-cell patch-clamp technique, we determined how the five cytokines (TNFα, IL-1β, IL-6, IL-12p40 and IL-15 for 22-28-h) at concentrations matched to those elicited by MHV-A59 coronavirus brain infection, affected neuronal function in cultured primary mouse neocortical neurons. RESULTS We evaluated how acute cytokine exposure affected neuronal excitability (propensity to fire action potentials), membrane properties, and action potential characteristics, as well as sensitivity to changes in extracellular calcium and magnesium (divalent) concentration. Neurovirulent cytokines increased spontaneous excitability and response to low divalent concentration by depolarizing the resting membrane potential and hyperpolarizing the action potential threshold. Evoked excitability was also enhanced by neurovirulent cytokines at physiological divalent concentrations. At low divalent concentrations, the change in evoked excitability was attenuated. One hour after cytokine removal, spontaneous excitability and hyperpolarization of the action potential threshold normalized but membrane depolarization and attenuated divalent-dependent excitability persisted. CONCLUSIONS Coronavirus-associated cytokine exposure increases spontaneous excitability in neocortical neurons, and some of the changes persist after cytokine removal.
Collapse
Affiliation(s)
- Salil R Rajayer
- Section of Pulmonary, Critical Care, Allergy, and Sleep Medicine, VA Portland Health Care System, 3710 SW U.S. Veterans Hospital Road, R&D 24, Portland, OR, 97239, USA
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Stephen M Smith
- Section of Pulmonary, Critical Care, Allergy, and Sleep Medicine, VA Portland Health Care System, 3710 SW U.S. Veterans Hospital Road, R&D 24, Portland, OR, 97239, USA.
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Oregon Health and Science University, Portland, OR, 97239, USA.
| |
Collapse
|
8
|
Wu YL, Yang AH, Chiu YH. Recent advances in the structure and activation mechanisms of metabolite-releasing Pannexin 1 channels. Biochem Soc Trans 2023; 51:1687-1699. [PMID: 37622532 DOI: 10.1042/bst20230038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/13/2023] [Accepted: 08/15/2023] [Indexed: 08/26/2023]
Abstract
Pannexin 1 (PANX1) is a widely expressed large-pore ion channel located in the plasma membrane of almost all vertebrate cells. It possesses a unique ability to act as a conduit for both inorganic ions (e.g. potassium or chloride) and bioactive metabolites (e.g. ATP or glutamate), thereby activating varying signaling pathways in an autocrine or paracrine manner. Given its crucial role in cell-cell interactions, the activity of PANX1 has been implicated in maintaining homeostasis of cardiovascular, immune, and nervous systems. Dysregulation of PANX1 has also been linked to numerous diseases, such as ischemic stroke, seizure, and inflammatory disorders. Therefore, the mechanisms underlying different modes of PANX1 activation and its context-specific channel properties have gathered significant attention. In this review, we summarize the roles of PANX1 in various physiological processes and diseases, and analyze the accumulated lines of evidence supporting diverse molecular mechanisms associated with different PANX1 activation modalities. We focus on examining recent discoveries regarding PANX1 regulations by reversible post-translational modifications, elevated intracellular calcium concentration, and protein-protein interactions, as well as by irreversible cleavage of its C-terminal tail. Additionally, we delve into the caveats in the proposed PANX1 gating mechanisms and channel open-closed configurations by critically analyzing the structural insights derived from cryo-EM studies and the unitary properties of PANX1 channels. By doing so, we aim to identify potential research directions for a better understanding of the functions and regulations of PANX1 channels.
Collapse
Affiliation(s)
- Yi-Ling Wu
- Department of Life Science, National Tsing Hua University, No. 101, Sec. 2, Kuang Fu Rd., Hsinchu 300044, Taiwan
| | - Ai-Hsing Yang
- Department of Life Science, National Tsing Hua University, No. 101, Sec. 2, Kuang Fu Rd., Hsinchu 300044, Taiwan
| | - Yu-Hsin Chiu
- Department of Life Science, National Tsing Hua University, No. 101, Sec. 2, Kuang Fu Rd., Hsinchu 300044, Taiwan
- Institute of Biotechnology and Department of Medical Science, National Tsing Hua University, No. 101, Sec. 2, Kuang Fu Rd., Hsinchu 300044, Taiwan
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
Ma Z, Paudel U, Foskett JK. Effects of temperature on action potentials and ion conductances in type II taste-bud cells. Am J Physiol Cell Physiol 2023; 325:C155-C171. [PMID: 37273235 PMCID: PMC10312327 DOI: 10.1152/ajpcell.00413.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/06/2023]
Abstract
Temperature strongly influences the intensity of taste, but it remains understudied despite its physiological, hedonic, and commercial implications. The relative roles of the peripheral gustatory and somatosensory systems innervating the oral cavity in mediating thermal effects on taste sensation and perception are poorly understood. Type II taste-bud cells, responsible for sensing sweet, bitter umami, and appetitive NaCl, release neurotransmitters to gustatory neurons by the generation of action potentials, but the effects of temperature on action potentials and the underlying voltage-gated conductances are unknown. Here, we used patch-clamp electrophysiology to explore the effects of temperature on acutely isolated type II taste-bud cell electrical excitability and whole cell conductances. Our data reveal that temperature strongly affects action potential generation, properties, and frequency and suggest that thermal sensitivities of underlying voltage-gated Na+ and K+ channel conductances provide a mechanism for how and whether voltage-gated Na+ and K+ channels in the peripheral gustatory system contribute to the influence of temperature on taste sensitivity and perception.NEW & NOTEWORTHY The temperature of food affects how it tastes. Nevertheless, the mechanisms involved are not well understood, particularly whether the physiology of taste-bud cells in the mouth is involved. Here we show that the electrical activity of type II taste-bud cells that sense sweet, bitter, and umami substances is strongly influenced by temperature. These results suggest a mechanism for the influence of temperature on the intensity of taste perception that resides in taste buds themselves.
Collapse
Affiliation(s)
- Zhongming Ma
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Usha Paudel
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| |
Collapse
|
11
|
Danielli S, Ma Z, Pantazi E, Kumar A, Demarco B, Fischer FA, Paudel U, Weissenrieder J, Lee RJ, Joyce S, Foskett JK, Bezbradica JS. The ion channel CALHM6 controls bacterial infection-induced cellular cross-talk at the immunological synapse. EMBO J 2023; 42:e111450. [PMID: 36861806 PMCID: PMC10068325 DOI: 10.15252/embj.2022111450] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 01/19/2023] [Accepted: 01/26/2023] [Indexed: 03/03/2023] Open
Abstract
Membrane ion channels of the calcium homeostasis modulator (CALHM) family promote cell-cell crosstalk at neuronal synapses via ATP release, where ATP acts as a neurotransmitter. CALHM6, the only CALHM highly expressed in immune cells, has been linked to the induction of natural killer (NK) cell anti-tumour activity. However, its mechanism of action and broader functions in the immune system remain unclear. Here, we generated Calhm6-/- mice and report that CALHM6 is important for the regulation of the early innate control of Listeria monocytogenes infection in vivo. We find that CALHM6 is upregulated in macrophages by pathogen-derived signals and that it relocates from the intracellular compartment to the macrophage-NK cell synapse, facilitating ATP release and controlling the kinetics of NK cell activation. Anti-inflammatory cytokines terminate CALHM6 expression. CALHM6 forms an ion channel when expressed in the plasma membrane of Xenopus oocytes, where channel opening is controlled by a conserved acidic residue, E119. In mammalian cells, CALHM6 is localised to intracellular compartments. Our results contribute to the understanding of neurotransmitter-like signal exchange between immune cells that fine-tunes the timing of innate immune responses.
Collapse
Affiliation(s)
- Sara Danielli
- The Kennedy Institute of RheumatologyUniversity of OxfordOxfordUK
| | - Zhongming Ma
- Department of Physiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Eirini Pantazi
- The Kennedy Institute of RheumatologyUniversity of OxfordOxfordUK
| | - Amrendra Kumar
- Department of Veterans AffairsTennessee Valley Healthcare SystemNashvilleTNUSA
- Department of Pathology, Microbiology, & ImmunologyVanderbilt University Medical CenterNashvilleTNUSA
| | - Benjamin Demarco
- The Kennedy Institute of RheumatologyUniversity of OxfordOxfordUK
| | - Fabian A Fischer
- The Kennedy Institute of RheumatologyUniversity of OxfordOxfordUK
| | - Usha Paudel
- Department of Physiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Jillian Weissenrieder
- Department of Physiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Robert J Lee
- Department of Physiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
- Department of Otorhinolaryngology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Sebastian Joyce
- Department of Veterans AffairsTennessee Valley Healthcare SystemNashvilleTNUSA
- Department of Pathology, Microbiology, & ImmunologyVanderbilt University Medical CenterNashvilleTNUSA
| | - J Kevin Foskett
- Department of Physiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
- Department of Cell and Developmental Biology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | | |
Collapse
|
12
|
Vega JL, Gutiérrez C, Rojas M, Güiza J, Sáez JC. Contribution of large-pore channels to inflammation induced by microorganisms. Front Cell Dev Biol 2023; 10:1094362. [PMID: 36699007 PMCID: PMC9868820 DOI: 10.3389/fcell.2022.1094362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 12/22/2022] [Indexed: 01/12/2023] Open
Abstract
Plasma membrane ionic channels selectively permeate potassium, sodium, calcium, and chloride ions. However, large-pore channels are permeable to ions and small molecules such as ATP and glutamate, among others. Large-pore channels are structures formed by several protein families with little or no evolutionary linkages including connexins (Cxs), pannexins (Panxs), innexin (Inxs), unnexins (Unxs), calcium homeostasis modulator (CALHMs), and Leucine-rich repeat-containing 8 (LRRC8) proteins. Large-pore channels are key players in inflammatory cell response, guiding the activation of inflammasomes, the release of pro-inflammatory cytokines such as interleukin-1 beta (IL-1ß), and the release of adenosine-5'-triphosphate (ATP), which is considered a danger signal. This review summarizes our current understanding of large-pore channels and their contribution to inflammation induced by microorganisms, virulence factors or their toxins.
Collapse
Affiliation(s)
- José L. Vega
- Laboratory of Gap Junctions Proteins and Parasitic Diseases (GaPaL), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile,Centro de Investigación en Inmunología y Biotecnología Biomédica de Antofagasta (CIIBBA), Universidad de Antofagasta, Antofagasta, Chile,Centro de Fisiología y Medicina de Altura (FIMEDALT), Universidad de Antofagasta, Antofagasta, Chile,*Correspondence: José L. Vega,
| | - Camila Gutiérrez
- Laboratory of Gap Junctions Proteins and Parasitic Diseases (GaPaL), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Mauro Rojas
- Laboratory of Gap Junctions Proteins and Parasitic Diseases (GaPaL), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Juan Güiza
- Laboratory of Gap Junctions Proteins and Parasitic Diseases (GaPaL), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Juan C. Sáez
- Centro Interdisciplinario de Neurociencias de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| |
Collapse
|
13
|
Roy S, Johner N, Trendafilov V, Gautschi I, Bignucolo O, Molton O, Bernèche S, Kellenberger S. Calcium regulates acid-sensing ion channel 3 activation by competing with protons in the channel pore and at an allosteric binding site. Open Biol 2022; 12:220243. [PMID: 36541099 PMCID: PMC9768671 DOI: 10.1098/rsob.220243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The extracellular Ca2+ concentration changes locally under certain physiological and pathological conditions. Such variations affect the function of ion channels of the nervous system and consequently also neuronal signalling. We investigated here the mechanisms by which Ca2+ controls the activity of acid-sensing ion channel (ASIC) 3. ASICs are neuronal, H+-gated Na+ channels involved in several physiological and pathological processes, including the expression of fear, learning, pain sensation and neurodegeneration after ischaemic stroke. It was previously shown that Ca2+ negatively modulates the ASIC pH dependence. While protons are default activators of ASIC3, this channel can also be activated at pH7.4 by the removal of the extracellular Ca2+. Two previous studies concluded that low pH opens ASIC3 by displacing Ca2+ ions that block the channel pore at physiological pH. We show here that an acidic residue, distant from the pore, together with pore residues, controls the modulation of ASIC3 by Ca2+. Our study identifies a new regulatory site in ASIC3 and demonstrates that ASIC3 activation involves an allosteric mechanism together with Ca2+ unbinding from the channel pore. We provide a molecular analysis of a regulatory mechanism found in many ion channels.
Collapse
Affiliation(s)
- Sophie Roy
- Department of biomedical Sciences, University of Lausanne, 1011 Lausanne, Switzerland
| | - Niklaus Johner
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland,Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Viktor Trendafilov
- Department of biomedical Sciences, University of Lausanne, 1011 Lausanne, Switzerland
| | - Ivan Gautschi
- Department of biomedical Sciences, University of Lausanne, 1011 Lausanne, Switzerland
| | - Olivier Bignucolo
- Department of biomedical Sciences, University of Lausanne, 1011 Lausanne, Switzerland,Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Ophélie Molton
- Department of biomedical Sciences, University of Lausanne, 1011 Lausanne, Switzerland
| | - Simon Bernèche
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland,Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Stephan Kellenberger
- Department of biomedical Sciences, University of Lausanne, 1011 Lausanne, Switzerland
| |
Collapse
|
14
|
Hill DB, Button B, Rubinstein M, Boucher RC. Physiology and pathophysiology of human airway mucus. Physiol Rev 2022; 102:1757-1836. [PMID: 35001665 PMCID: PMC9665957 DOI: 10.1152/physrev.00004.2021] [Citation(s) in RCA: 78] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 12/13/2021] [Accepted: 12/19/2021] [Indexed: 01/27/2023] Open
Abstract
The mucus clearance system is the dominant mechanical host defense system of the human lung. Mucus is cleared from the lung by cilia and airflow, including both two-phase gas-liquid pumping and cough-dependent mechanisms, and mucus transport rates are heavily dependent on mucus concentration. Importantly, mucus transport rates are accurately predicted by the gel-on-brush model of the mucociliary apparatus from the relative osmotic moduli of the mucus and periciliary-glycocalyceal (PCL-G) layers. The fluid available to hydrate mucus is generated by transepithelial fluid transport. Feedback interactions between mucus concentrations and cilia beating, via purinergic signaling, coordinate Na+ absorptive vs Cl- secretory rates to maintain mucus hydration in health. In disease, mucus becomes hyperconcentrated (dehydrated). Multiple mechanisms derange the ion transport pathways that normally hydrate mucus in muco-obstructive lung diseases, e.g., cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), non-CF bronchiectasis (NCFB), and primary ciliary dyskinesia (PCD). A key step in muco-obstructive disease pathogenesis is the osmotic compression of the mucus layer onto the airway surface with the formation of adherent mucus plaques and plugs, particularly in distal airways. Mucus plaques create locally hypoxic conditions and produce airflow obstruction, inflammation, infection, and, ultimately, airway wall damage. Therapies to clear adherent mucus with hydrating and mucolytic agents are rational, and strategies to develop these agents are reviewed.
Collapse
Affiliation(s)
- David B Hill
- Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
- Joint Department of Biomedical Engineering, The University of North Carolina and North Carolina State University, Chapel Hill, North Carolina
| | - Brian Button
- Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Michael Rubinstein
- Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
- Department of Mechanical Engineering and Materials Science, Biomedical Engineering, Physics, and Chemistry, Duke University, Durham, North Carolina
| | - Richard C Boucher
- Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| |
Collapse
|
15
|
Callens M, Loncke J, Bultynck G. Dysregulated Ca 2+ Homeostasis as a Central Theme in Neurodegeneration: Lessons from Alzheimer's Disease and Wolfram Syndrome. Cells 2022; 11:cells11121963. [PMID: 35741091 PMCID: PMC9221778 DOI: 10.3390/cells11121963] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/06/2022] [Accepted: 06/13/2022] [Indexed: 12/12/2022] Open
Abstract
Calcium ions (Ca2+) operate as important messengers in the cell, indispensable for signaling the underlying numerous cellular processes in all of the cell types in the human body. In neurons, Ca2+ signaling is crucial for regulating synaptic transmission and for the processes of learning and memory formation. Hence, the dysregulation of intracellular Ca2+ homeostasis results in a broad range of disorders, including cancer and neurodegeneration. A major source for intracellular Ca2+ is the endoplasmic reticulum (ER), which has close contacts with other organelles, including mitochondria. In this review, we focus on the emerging role of Ca2+ signaling at the ER–mitochondrial interface in two different neurodegenerative diseases, namely Alzheimer’s disease and Wolfram syndrome. Both of these diseases share some common hallmarks in the early stages, including alterations in the ER and mitochondrial Ca2+ handling, mitochondrial dysfunction and increased Reactive oxygen species (ROS) production. This indicates that similar mechanisms may underly these two disease pathologies and suggests that both research topics might benefit from complementary research.
Collapse
|
16
|
Khare N, Maheshwari SK, Rizvi SMD, Albadrani HM, Alsagaby SA, Alturaiki W, Iqbal D, Zia Q, Villa C, Jha SK, Jha NK, Jha AK. Homology Modelling, Molecular Docking and Molecular Dynamics Simulation Studies of CALMH1 against Secondary Metabolites of Bauhinia variegata to Treat Alzheimer's Disease. Brain Sci 2022; 12:brainsci12060770. [PMID: 35741655 PMCID: PMC9220886 DOI: 10.3390/brainsci12060770] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 05/05/2022] [Accepted: 05/31/2022] [Indexed: 02/06/2023] Open
Abstract
Calcium homeostasis modulator 1 (CALHM1) is a protein responsible for causing Alzheimer’s disease. In the absence of an experimentally designed protein molecule, homology modelling was performed. Through homology modelling, different CALHM1 models were generated and validated through Rampage. To carry out further in silico studies, through molecular docking and molecular dynamics simulation experiments, various flavonoids and alkaloids from Bauhinia variegata were utilised as inhibitors to target the protein (CALHM1). The sequence of CALHM1 was retrieved from UniProt and the secondary structure prediction of CALHM1 was done through CFSSP, GOR4, and SOPMA methods. The structure was identified through LOMETS, MUSTER, and MODELLER and finally, the structures were validated through Rampage. Bauhinia variegata plant was used to check the interaction of alkaloids and flavonoids against CALHM1. The protein and protein–ligand complex were also validated through molecular dynamics simulations studies. The model generated through MODELLER software with 6VAM A was used because this model predicted the best results in the Ramachandran plot. Further molecular docking was performed, quercetin was found to be the most appropriate candidate for the protein molecule with the minimum binding energy of −12.45 kcal/mol and their ADME properties were analysed through Molsoft and Molinspiration. Molecular dynamics simulations showed that CALHM1 and CALHM1–quercetin complex became stable at 2500 ps. It may be seen through the study that quercetin may act as a good inhibitor for treatment. With the help of an in silico study, it was easier to analyse the 3D structure of the protein, which may be scrutinized for the best-predicted model. Quercetin may work as a good inhibitor for treating Alzheimer’s disease, according to in silico research using molecular docking and molecular dynamics simulations, and future in vitro and in vivo analysis may confirm its effectiveness.
Collapse
Affiliation(s)
- Noopur Khare
- Institute of Biosciences and Technology, Shri Ramswaroop Memorial University, Barabanki 225003, Uttar Pradesh, India; (N.K.); (S.K.M.)
- Department of Biotechnology, Dr. A.P.J. Abdul Kalam Technical University, Lucknow 226021, Uttar Pradesh, India
| | - Sanjiv Kumar Maheshwari
- Institute of Biosciences and Technology, Shri Ramswaroop Memorial University, Barabanki 225003, Uttar Pradesh, India; (N.K.); (S.K.M.)
| | - Syed Mohd Danish Rizvi
- Department of Pharmaceutics, College of Pharmacy, University of Hail, Hail 2240, Saudi Arabia;
| | - Hind Muteb Albadrani
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah 11952, Saudi Arabia; (H.M.A.); (S.A.A.); (W.A.); (Q.Z.)
| | - Suliman A. Alsagaby
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah 11952, Saudi Arabia; (H.M.A.); (S.A.A.); (W.A.); (Q.Z.)
| | - Wael Alturaiki
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah 11952, Saudi Arabia; (H.M.A.); (S.A.A.); (W.A.); (Q.Z.)
| | - Danish Iqbal
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah 11952, Saudi Arabia; (H.M.A.); (S.A.A.); (W.A.); (Q.Z.)
- Health and Basic Sciences Research Center, Majmaah University, Al Majmaah 15341, Saudi Arabia
- Correspondence: (D.I.); (A.K.J.)
| | - Qamar Zia
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah 11952, Saudi Arabia; (H.M.A.); (S.A.A.); (W.A.); (Q.Z.)
- Health and Basic Sciences Research Center, Majmaah University, Al Majmaah 15341, Saudi Arabia
| | - Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, 20900 Monza, Italy;
| | - Saurabh Kumar Jha
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Greater Noida 201310, Uttar Pradesh, India; (S.K.J.); (N.K.J.)
- Department of Biotechnology, School of Applied & Life Sciences (SALS), Uttaranchal University, Dehradun 248007, Uttarakhand, India
- Department of Biotechnology Engineering and Food Technology, Chandigarh University, Mohali 140413, Punjab, India
| | - Niraj Kumar Jha
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Greater Noida 201310, Uttar Pradesh, India; (S.K.J.); (N.K.J.)
- Department of Biotechnology, School of Applied & Life Sciences (SALS), Uttaranchal University, Dehradun 248007, Uttarakhand, India
- Department of Biotechnology Engineering and Food Technology, Chandigarh University, Mohali 140413, Punjab, India
| | - Abhimanyu Kumar Jha
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Greater Noida 201310, Uttar Pradesh, India; (S.K.J.); (N.K.J.)
- Correspondence: (D.I.); (A.K.J.)
| |
Collapse
|
17
|
Whyte-Fagundes P, Taskina D, Safarian N, Zoidl C, Carlen PL, Donaldson LW, Zoidl GR. Panx1 channels promote both anti- and pro-seizure-like activities in the zebrafish via p2rx7 receptors and ATP signaling. Commun Biol 2022; 5:472. [PMID: 35585187 PMCID: PMC9117279 DOI: 10.1038/s42003-022-03356-2] [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] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 04/12/2022] [Indexed: 11/08/2022] Open
Abstract
The molecular mechanisms of excitation/inhibition imbalances promoting seizure generation in epilepsy patients are not fully understood. Evidence suggests that Pannexin1 (Panx1), an ATP release channel, modulates the excitability of the brain. In this report, we performed electrophysiological, behavioral, and molecular phenotyping experiments on zebrafish larvae bearing genetic or pharmacological knockouts of Panx1a and Panx1b channels, each homologous to human PANX1. When Panx1a function is lost, or both channels are under pharmacological blockade, seizures with ictal-like events and seizure-like locomotion are reduced in the presence of pentylenetetrazol. Transcriptome profiling by RNA-seq demonstrates a spectrum of distinct metabolic and cell signaling states which correlate with the loss of Panx1a. Furthermore, the pro- and anticonvulsant activities of both Panx1 channels affect ATP release and involve the purinergic receptor P2rx7. Our findings suggest a subfunctionalization of Panx1 enabling dual roles in seizures, providing a unique and comprehensive perspective to understanding seizure mechanisms in the context of this channel.
Collapse
Affiliation(s)
- Paige Whyte-Fagundes
- Department of Biology, York University, Toronto, ON, M3J1P3, Canada.
- Center of Vision Research (CVR), York University, Toronto, ON, M3J1P3, Canada.
- Krembil Research Institute, University Health Network, 60 Leonard Ave, Toronto, ON, M5T 1M8, Canada.
| | - Daria Taskina
- Department of Biology, York University, Toronto, ON, M3J1P3, Canada
- Center of Vision Research (CVR), York University, Toronto, ON, M3J1P3, Canada
| | - Nickie Safarian
- Department of Biology, York University, Toronto, ON, M3J1P3, Canada
- Center of Vision Research (CVR), York University, Toronto, ON, M3J1P3, Canada
| | - Christiane Zoidl
- Department of Biology, York University, Toronto, ON, M3J1P3, Canada
- Center of Vision Research (CVR), York University, Toronto, ON, M3J1P3, Canada
| | - Peter L Carlen
- Krembil Research Institute, University Health Network, 60 Leonard Ave, Toronto, ON, M5T 1M8, Canada
- Department of Medicine, Physiology and BME, University of Toronto, 399 Bathurst St., 5w442, Toronto, ON, M5T 2S8, Canada
| | | | - Georg R Zoidl
- Department of Biology, York University, Toronto, ON, M3J1P3, Canada.
- Center of Vision Research (CVR), York University, Toronto, ON, M3J1P3, Canada.
- Krembil Research Institute, University Health Network, 60 Leonard Ave, Toronto, ON, M5T 1M8, Canada.
| |
Collapse
|
18
|
Kasuya G, Nureki O. Recent Advances in the Structural Biology of the Volume-Regulated Anion Channel LRRC8. Front Pharmacol 2022; 13:896532. [PMID: 35645818 PMCID: PMC9130832 DOI: 10.3389/fphar.2022.896532] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 04/25/2022] [Indexed: 01/23/2023] Open
Abstract
Members of the leucine-rich repeat-containing 8 (LRRC8) protein family, composed of five LRRC8A-E isoforms, are pore-forming components of the volume-regulated anion channel (VRAC), which is activated by cell swelling and releases chloride ions (Cl−) or other osmolytes to counteract cell swelling. Although the LRRC8 protein family was identified as the molecular entity of VRAC only in 2014, due to recent advances in cryo-electron microscopy (cryo-EM), various LRRC8 structures, including homo-hexameric LRRC8A and LRRC8D structures, as well as inhibitor-bound and synthetic single-domain antibody-bound homo-hexameric LRRC8A structures, have been reported, thus extending our understanding of the molecular mechanisms of this protein family. In this review, we describe the important features of LRRC8 provided by these structures, particularly the overall architectures, and the suggested mechanisms underlying pore inhibition and allosteric modulation by targeting the intracellular leucine-rich repeat (LRR) domain.
Collapse
Affiliation(s)
- Go Kasuya
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University, Shimotsuke, Japan
- *Correspondence: Go Kasuya, ; Osamu Nureki,
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- *Correspondence: Go Kasuya, ; Osamu Nureki,
| |
Collapse
|
19
|
Boudreault F, Tan JJ, Grygorczyk R. Propidium uptake and ATP release in A549 cells share similar transport mechanisms. Biophys J 2022; 121:1593-1609. [PMID: 35398020 PMCID: PMC9117937 DOI: 10.1016/j.bpj.2022.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 03/03/2022] [Accepted: 04/04/2022] [Indexed: 11/02/2022] Open
Abstract
The lipid bilayer of eukaryotic cells' plasma membrane is almost impermeable to small ions and large polar molecules, but its miniscule basal permeability in intact cells is poorly characterized. This report describes the intrinsic membrane permeability of A549 cells toward the charged molecules propidium (Pr2+) and ATP4-. Under isotonic conditions, we detected with quantitative fluorescence microscopy, a continuous low-rate uptake of Pr (∼150 × 10-21 moles (zmol)/h/cell, [Pr]o = 150 μM, 32°C). It was stimulated transiently but strongly by 66% hypotonic cell swelling reaching an influx amplitude of ∼1500 (zmol/h)/cell. The progressive Pr uptake with increasing [Pr]o (30, 150, and 750 μM) suggested a permeation mechanism by simple diffusion. We quantified separately ATP release with custom wide-field-of-view chemiluminescence imaging. The strong proportionality between ATP efflux and Pr2+ influx during hypotonic challenge, and the absence of stimulation of transmembrane transport following 300% hypertonic shock, indicated that ATP and Pr travel the same conductive pathway. The fluorescence images revealed a homogeneously distributed intracellular uptake of Pr not consistent with high-conductance channels expressed at low density on the plasma membrane. We hypothesized that the pathway consists of transiently formed water pores evenly spread across the plasma membrane. The abolition of cell swelling-induced Pr uptake with 500 μM gadolinium, a known modulator of membrane fluidity, supported the involvement of water pores whose formation depends on the membrane fluidity. Our study suggests an alternative model of a direct permeation of ATP (and other molecules) through the phospholipid bilayer, which may have important physiological implications.
Collapse
|
20
|
Xia W, Zheng L, Fang J, Li F, Zhou Y, Zeng Z, Zhang B, Li Z, Li H, Zhu F. PFmulDL: a novel strategy enabling multi-class and multi-label protein function annotation by integrating diverse deep learning methods. Comput Biol Med 2022; 145:105465. [PMID: 35366467 DOI: 10.1016/j.compbiomed.2022.105465] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/22/2022] [Accepted: 03/25/2022] [Indexed: 02/06/2023]
Abstract
Bioinformatic annotation of protein function is essential but extremely sophisticated, which asks for extensive efforts to develop effective prediction method. However, the existing methods tend to amplify the representativeness of the families with large number of proteins by misclassifying the proteins in the families with small number of proteins. That is to say, the ability of the existing methods to annotate proteins in the 'rare classes' remains limited. Herein, a new protein function annotation strategy, PFmulDL, integrating multiple deep learning methods, was thus constructed. First, the recurrent neural network was integrated, for the first time, with the convolutional neural network to facilitate the function annotation. Second, a transfer learning method was introduced to the model construction for further improving the prediction performances. Third, based on the latest data of Gene Ontology, the newly constructed model could annotate the largest number of protein families comparing with the existing methods. Finally, this newly constructed model was found capable of significantly elevating the prediction performance for the 'rare classes' without sacrificing that for the 'major classes'. All in all, due to the emerging requirements on improving the prediction performance for the proteins in 'rare classes', this new strategy would become an essential complement to the existing methods for protein function prediction. All the models and source codes are freely available and open to all users at: https://github.com/idrblab/PFmulDL.
Collapse
Affiliation(s)
- Weiqi Xia
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China
| | - Lingyan Zheng
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China; Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, 330110, China
| | - Jiebin Fang
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China
| | - Fengcheng Li
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China
| | - Ying Zhou
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China
| | - Zhenyu Zeng
- Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, 330110, China
| | - Bing Zhang
- Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, 330110, China
| | - Zhaorong Li
- Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, 330110, China
| | - Honglin Li
- School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, China.
| | - Feng Zhu
- College of Pharmaceutical Sciences, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China; Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou, 330110, China.
| |
Collapse
|
21
|
Ren Y, Li Y, Wang Y, Wen T, Lu X, Chang S, Zhang X, Shen Y, Yang X. Cryo-EM structure of the heptameric calcium homeostasis modulator 1 channel. J Biol Chem 2022; 298:101838. [PMID: 35339491 PMCID: PMC9035704 DOI: 10.1016/j.jbc.2022.101838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 03/13/2022] [Accepted: 03/14/2022] [Indexed: 12/01/2022] Open
Abstract
Calcium homeostasis modulator 1 (CALHM1) is a voltage- and Ca2+-gated ATP channel that plays an important role in neuronal signaling. However, as the previously reported CALHM structures are all in the ATP-conducting state, the gating mechanism of ATP permeation is still elusive. Here, we report cryo-EM reconstructions of two Danio rerio CALHM1 heptamers with ordered or flexible long C-terminal helices at resolutions of 3.2 Å and 2.9 Å, respectively, and one D. rerio CALHM1 octamer with flexible long C-terminal helices at a resolution of 3.5 Å. Structural analysis shows that the heptameric CALHM1s are in an ATP-nonconducting state with a central pore diameter of approximately 6.6 Å. Compared with those inside the octameric CALHM1, the N-helix inside the heptameric CALHM1 is in the “down” position to avoid steric clashing with the adjacent TM1 helix. Molecular dynamics simulations show that as the N-helix moves from the “down” position to the “up” position, the pore size of ATP molecule permeation increases significantly. Our results provide important information for elucidating the mechanism of ATP molecule permeation in the CALHM1 channel.
Collapse
Affiliation(s)
- Yue Ren
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Yang Li
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Yaojie Wang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Tianlei Wen
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Xuhang Lu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China
| | - Shenghai Chang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China; Center of Cryo Electron Microscopy, Zhejiang University School of Medicine, Hangzhou, China
| | - Xing Zhang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China; Center of Cryo Electron Microscopy, Zhejiang University School of Medicine, Hangzhou, China
| | - Yuequan Shen
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China; Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin 300071, China.
| | - Xue Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China.
| |
Collapse
|
22
|
Salgado MTSF, Fernandes E Silva E, Matsumoto AM, Mattozo FH, Amarante MCAD, Kalil SJ, Votto APDS. C-phycocyanin decreases proliferation and migration of melanoma cells: In silico and in vitro evidences. Bioorg Chem 2022; 122:105757. [PMID: 35339928 DOI: 10.1016/j.bioorg.2022.105757] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 10/25/2021] [Accepted: 03/20/2022] [Indexed: 12/24/2022]
Abstract
The incidence and number of deaths caused by melanoma have been increasing in recent years, and the pigment C-phycocyanin (C-PC) appears as a possible alternative to treat this disease. So, the objective of this study was to combine in silico and in vitro analysis to understand the main anti-melanoma pathways exerted by C-PC. We evaluated the ability of C-PC to bind to the main cellular targets related in the progression of melanoma through molecular docking, and the reflection of this bind in the biological effects in the B16F10 cell line through in vitro analysis. Our results showed that C-PC was able to bind BRAF and MEK, which are related to the signal transduction pathway for proliferation and survival. There was also an interaction between C-PC and cyclin-dependent kinase 4 and 6. In vitro analysis demonstrated that C-PC decreased B16F10 cell proliferation, as observed by cell viability and mitotic index assays. C-PC also interacted with matrix metalloproteinase 2 and 9 and N-cadherin, which may have caused the decrease in cell migration observed in vitro. Besides that, C-PC interacts with VEGF, a factor responsible for regulating the proliferation and cellular invasion pathways. Finally, C-PC did not alter the cell viability of the non-tumoral melanocytes. Therefore, C-PC is a strong anti-tumor candidate for the treatment of melanoma, since it acts in different cellular pathways of melanoma, without causing damage to non-tumoral cells.
Collapse
Affiliation(s)
| | | | - Andressa Mai Matsumoto
- Laboratório de Cultura Celular, ICB, FURG, RS, Brazil; Programa de Pós-Graduação em Ciências Fisiológicas, ICB, FURG, RS, Brazil
| | - Francielly Hafele Mattozo
- Laboratório de Cultura Celular, ICB, FURG, RS, Brazil; Programa de Pós-Graduação em Ciências Fisiológicas, ICB, FURG, RS, Brazil
| | | | | | - Ana Paula de Souza Votto
- Laboratório de Cultura Celular, ICB, FURG, RS, Brazil; Programa de Pós-Graduação em Ciências Fisiológicas, ICB, FURG, RS, Brazil.
| |
Collapse
|
23
|
Wooding SP, Ramirez VA, Behrens M. Bitter taste receptors: Genes, evolution and health. Evol Med Public Health 2022; 9:431-447. [PMID: 35154779 PMCID: PMC8830313 DOI: 10.1093/emph/eoab031] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 10/05/2021] [Indexed: 02/01/2023] Open
Abstract
Bitter taste perception plays vital roles in animal behavior and fitness. By signaling the presence of toxins in foods, particularly noxious defense compounds found in plants, it enables animals to avoid exposure. In vertebrates, bitter perception is initiated by TAS2Rs, a family of G protein-coupled receptors expressed on the surface of taste buds. There, oriented toward the interior of the mouth, they monitor the contents of foods, drinks and other substances as they are ingested. When bitter compounds are encountered, TAS2Rs respond by triggering neural pathways leading to sensation. The importance of this role placed TAS2Rs under selective pressures in the course of their evolution, leaving signatures in patterns of gene gain and loss, sequence polymorphism, and population structure consistent with vertebrates' diverse feeding ecologies. The protective value of bitter taste is reduced in modern humans because contemporary food supplies are safe and abundant. However, this is not always the case. Some crops, particularly in the developing world, retain surprisingly high toxicity and bitterness remains an important measure of safety. Bitter perception also shapes health through its influence on preference driven behaviors such as diet choice, alcohol intake and tobacco use. Further, allelic variation in TAS2Rs is extensive, leading to individual differences in taste sensitivity that drive these behaviors, shaping susceptibility to disease. Thus, bitter taste perception occupies a critical intersection between ancient evolutionary processes and modern human health.
Collapse
Affiliation(s)
- Stephen P Wooding
- Department of Anthropology and Health Sciences Research Institute, University of California, Merced, CA, USA
| | - Vicente A Ramirez
- Department of Public Health, University of California, Merced, CA, USA
| | - Maik Behrens
- Maik Behrens, Leibniz-Institute for Food Systems Biology at the Technical University of Munich, Freising, Germany
| |
Collapse
|
24
|
Alijevic O, Peng Z, Kellenberger S. Changes in H +, K +, and Ca 2+ Concentrations, as Observed in Seizures, Induce Action Potential Signaling in Cortical Neurons by a Mechanism That Depends Partially on Acid-Sensing Ion Channels. Front Cell Neurosci 2021; 15:732869. [PMID: 34720879 PMCID: PMC8553998 DOI: 10.3389/fncel.2021.732869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/27/2021] [Indexed: 11/13/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are activated by extracellular acidification. Because ASIC currents are transient, these channels appear to be ideal sensors for detecting the onset of rapid pH changes. ASICs are involved in neuronal death after ischemic stroke, and in the sensation of inflammatory pain. Ischemia and inflammation are associated with a slowly developing, long-lasting acidification. Recent studies indicate however that ASICs are unable to induce an electrical signaling activity under standard experimental conditions if pH changes are slow. In situations associated with slow and sustained pH drops such as high neuronal signaling activity and ischemia, the extracellular K+ concentration increases, and the Ca2+ concentration decreases. We hypothesized that the concomitant changes in H+, K+, and Ca2+ concentrations may allow a long-lasting ASIC-dependent induction of action potential (AP) signaling. We show that for acidification from pH7.4 to pH7.0 or 6.8 on cultured cortical neurons, the number of action potentials and the firing time increased strongly if the acidification was accompanied by a change to higher K+ and lower Ca2+ concentrations. Under these conditions, APs were also induced in neurons from ASIC1a-/- mice, in which a pH of ≤ 5.0 would be required to activate ASICs, indicating that ASIC activation was not required for the AP induction. Comparison between neurons of different ASIC genotypes indicated that the ASICs modulate the AP induction under such changed ionic conditions. Voltage-clamp measurements of the Na+ and K+ currents in cultured cortical neurons showed that the lowering of the pH inhibited Na+ and K+ currents. In contrast, the lowering of the Ca2+ together with the increase in the K+ concentration led to a hyperpolarizing shift of the activation voltage dependence of voltage-gated Na+ channels. We conclude that the ionic changes observed during high neuronal activity mediate a sustained AP induction caused by the potentiation of Na+ currents, a membrane depolarization due to the changed K+ reversal potential, the activation of ASICs, and possibly effects on other ion channels. Our study describes therefore conditions under which slow pH changes induce neuronal signaling by a mechanism involving ASICs.
Collapse
Affiliation(s)
- Omar Alijevic
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
| | - Zhong Peng
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
| | - Stephan Kellenberger
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
25
|
Gaete PS, Lillo MA, López W, Liu Y, Jiang W, Luo Y, Harris AL, Contreras JE. A novel voltage-clamp/dye uptake assay reveals saturable transport of molecules through CALHM1 and connexin channels. J Gen Physiol 2021; 152:211474. [PMID: 33074302 PMCID: PMC7579738 DOI: 10.1085/jgp.202012607] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 09/23/2020] [Indexed: 12/14/2022] Open
Abstract
Large-pore channels permeable to small molecules such as ATP, in addition to atomic ions, are emerging as important regulators in health and disease. Nonetheless, their mechanisms of molecular permeation and selectivity remain mostly unexplored. Combining fluorescence microscopy and electrophysiology, we developed a novel technique that allows kinetic analysis of molecular permeation through connexin and CALHM1 channels in Xenopus oocytes rendered translucent. Using this methodology, we found that (1) molecular flux through these channels saturates at low micromolar concentrations, (2) kinetic parameters of molecular transport are sensitive to modulators of channel gating, (3) molecular transport and ionic currents can be differentially affected by mutation and gating, and (4) N-terminal regions of these channels control transport kinetics and permselectivity. Our methodology allows analysis of how human disease-causing mutations affect kinetic properties and permselectivity of molecular signaling and enables the study of molecular mechanisms, including selectivity and saturability, of molecular transport in other large-pore channels.
Collapse
Affiliation(s)
- Pablo S Gaete
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ
| | - Mauricio A Lillo
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ
| | - William López
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ
| | - Yu Liu
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ
| | - Wenjuan Jiang
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, CA
| | - Yun Luo
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, CA
| | - Andrew L Harris
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ
| | - Jorge E Contreras
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ
| |
Collapse
|
26
|
Rodriguez M, Chen J, Jain PP, Babicheva A, Xiong M, Li J, Lai N, Zhao T, Hernandez M, Balistrieri A, Parmisano S, Simonson T, Breen E, Valdez-Jasso D, Thistlethwaite PA, Shyy JYJ, Wang J, Garcia JGN, Makino A, Yuan JXJ. Upregulation of Calcium Homeostasis Modulators in Contractile-To-Proliferative Phenotypical Transition of Pulmonary Arterial Smooth Muscle Cells. Front Physiol 2021; 12:714785. [PMID: 34408668 PMCID: PMC8364962 DOI: 10.3389/fphys.2021.714785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 07/13/2021] [Indexed: 12/14/2022] Open
Abstract
Excessive pulmonary artery (PA) smooth muscle cell (PASMC) proliferation and migration are implicated in the development of pathogenic pulmonary vascular remodeling characterized by concentric arterial wall thickening and arteriole muscularization in patients with pulmonary arterial hypertension (PAH). Pulmonary artery smooth muscle cell contractile-to-proliferative phenotypical transition is a process that promotes pulmonary vascular remodeling. A rise in cytosolic Ca2+ concentration [(Ca2+) cyt ] in PASMCs is a trigger for pulmonary vasoconstriction and a stimulus for pulmonary vascular remodeling. Here, we report that the calcium homeostasis modulator (CALHM), a Ca2+ (and ATP) channel that is allosterically regulated by voltage and extracellular Ca2+, is upregulated during the PASMC contractile-to-proliferative phenotypical transition. Protein expression of CALHM1/2 in primary cultured PASMCs in media containing serum and growth factors (proliferative PASMC) was significantly greater than in freshly isolated PA (contractile PASMC) from the same rat. Upregulated CALHM1/2 in proliferative PASMCs were associated with an increased ratio of pAKT/AKT and pmTOR/mTOR and an increased expression of the cell proliferation marker PCNA, whereas serum starvation and rapamycin significantly downregulated CALHM1/2. Furthermore, CALHM1/2 were upregulated in freshly isolated PA from rats with monocrotaline (MCT)-induced PH and in primary cultured PASMC from patients with PAH in comparison to normal controls. Intraperitoneal injection of CGP 37157 (0.6 mg/kg, q8H), a non-selective blocker of CALHM channels, partially reversed established experimental PH. These data suggest that CALHM upregulation is involved in PASMC contractile-to-proliferative phenotypical transition. Ca2+ influx through upregulated CALHM1/2 may play an important role in the transition of sustained vasoconstriction to excessive vascular remodeling in PAH or precapillary PH. Calcium homeostasis modulator could potentially be a target to develop novel therapies for PAH.
Collapse
Affiliation(s)
- Marisela Rodriguez
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
- Department of Pediatrics, Tucson, AZ, United States
| | - Jiyuan Chen
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
- State Key Laboratory of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Pritesh P. Jain
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Aleksandra Babicheva
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Mingmei Xiong
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
- State Key Laboratory of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Jifeng Li
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
- Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Ning Lai
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
- State Key Laboratory of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Tengteng Zhao
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Moises Hernandez
- Division of Cardiothoracic Surgery, Department of Surgery, La Jolla, CA, United States
| | - Angela Balistrieri
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Sophia Parmisano
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Tatum Simonson
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Ellen Breen
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| | - Daniela Valdez-Jasso
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, United States
| | | | - John Y. -J. Shyy
- Division of Cardiovascular Medicine, Department of Medicine, La Jolla, CA, United States
| | - Jian Wang
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
- State Key Laboratory of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Joe G. N. Garcia
- Department of Medicine, The University of Arizona, Tucson, AZ, United States
| | - Ayako Makino
- Division of Endocrinology and Metabolism, La Jolla, CA, United States
| | - Jason X. -J. Yuan
- Section of Physiology, Division of Pulmonary, Critical Care and Sleep Medicine, La Jolla, CA, United States
| |
Collapse
|
27
|
Okui M, Murakami T, Sun H, Ikeshita C, Kanamura N, Taruno A. Posttranslational regulation of CALHM1/3 channel: N-linked glycosylation and S-palmitoylation. FASEB J 2021; 35:e21527. [PMID: 33788965 DOI: 10.1096/fj.202002632r] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 02/08/2021] [Accepted: 03/01/2021] [Indexed: 11/11/2022]
Abstract
Among calcium homeostasis modulator (CALHM) family members, CALHM1 and 3 together form a voltage-gated large-pore ion channel called CALHM1/3. CALHM1/3 plays an essential role in taste perception by mediating neurotransmitter release at channel synapses of taste bud cells. However, it is poorly understood how CALHM1/3 is regulated. Biochemical analyses of the two subunits following site-directed mutagenesis and pharmacological treatments established that both CALHM1 and 3 were N-glycosylated at single Asn residues in their second extracellular loops. Biochemical and electrophysiological studies revealed that N-glycan acquisition on CALHM1 and 3, respectively, controls the biosynthesis and gating kinetics of the CALHM1/3 channel. Furthermore, failure in subsequent remodeling of N-glycans decelerated the gating kinetics. Thus, the acquisition of N-glycans on both subunits and their remodeling differentially contribute to the functional expression of CALHM1/3. Meanwhile, metabolic labeling and acyl-biotin exchange assays combined with genetic modification demonstrated that CALHM3 was reversibly palmitoylated at three intracellular Cys residues. Screening of the DHHC protein acyltransferases identified DHHC3 and 15 as CALHM3 palmitoylating enzymes. The palmitoylation-deficient mutant CALHM3 showed a normal degradation rate and interaction with CALHM1. However, the same mutation markedly attenuated the channel activity but not surface localization of CALHM1/3, suggesting that CALHM3 palmitoylation is a critical determinant of CALHM1/3 activity but not its formation or forward trafficking. Overall, this study characterized N-glycosylation and S-palmitoylation of CALHM1/3 subunits and clarified their differential contributions to its functional expression, providing insights into the fine control of the CALHM1/3 channel and associated physiological processes.
Collapse
Affiliation(s)
- Motoki Okui
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan.,Department of Dental Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Tatsuro Murakami
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Hongxin Sun
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Chiaki Ikeshita
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Narisato Kanamura
- Department of Dental Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Akiyuki Taruno
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan.,Japan Science and Technology Agency, PRESTO, Kawaguchi, Japan
| |
Collapse
|
28
|
Guarascio DM, Gonzalez-Velandia KY, Hernandez-Clavijo A, Menini A, Pifferi S. Functional expression of TMEM16A in taste bud cells. J Physiol 2021; 599:3697-3714. [PMID: 34089532 PMCID: PMC8361675 DOI: 10.1113/jp281645] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 06/04/2021] [Indexed: 12/14/2022] Open
Abstract
Key points Taste transduction occurs in taste buds in the tongue epithelium. The Ca2+‐activated Cl– channels TMEM16A and TMEM16B play relevant physiological roles in several sensory systems. Here, we report that TMEM16A, but not TMEM16B, is expressed in the apical part of taste buds. Large Ca2+‐activated Cl− currents blocked by Ani‐9, a selective inhibitor of TMEM16A, are measured in type I taste cells but not in type II or III taste cells. ATP indirectly activates Ca2+‐activated Cl– currents in type I cells through TMEM16A channels. These results indicate that TMEM16A is functional in type I taste cells and contribute to understanding the largely unknown physiological roles of these cells.
Abstract The Ca2+‐activated Cl– channels TMEM16A and TMEM16B have relevant roles in many physiological processes including neuronal excitability and regulation of Cl– homeostasis. Here, we examined the presence of Ca2+‐activated Cl– channels in taste cells of mouse vallate papillae by using immunohistochemistry and electrophysiological recordings. By using immunohistochemistry we showed that only TMEM16A, and not TMEM16B, was expressed in taste bud cells where it largely co‐localized with the inwardly rectifying K+ channel KNCJ1 in the apical part of type I cells. By using whole‐cell patch‐clamp recordings in isolated cells from taste buds, we measured an average current of −1083 pA at −100 mV in 1.5 μm Ca2+ and symmetrical Cl– in type I cells. Ion substitution experiments and blockage by Ani‐9, a specific TMEM16A channel blocker, indicated that Ca2+ activated anionic currents through TMEM16A channels. We did not detect any Ca2+‐activated Cl– currents in type II or III taste cells. ATP is released by type II cells in response to various tastants and reaches type I cells where it is hydrolysed by ecto‐ATPases. Type I cells also express P2Y purinergic receptors and stimulation of type I cells with extracellular ATP produced large Ca2+‐activated Cl− currents blocked by Ani‐9, indicating a possible role of TMEM16A in ATP‐mediated signalling. These results provide a definitive demonstration that TMEM16A‐mediated currents are functional in type I taste cells and provide a foundation for future studies investigating physiological roles for these often‐neglected taste cells. Taste transduction occurs in taste buds in the tongue epithelium. The Ca2+‐activated Cl– channels TMEM16A and TMEM16B play relevant physiological roles in several sensory systems. Here, we report that TMEM16A, but not TMEM16B, is expressed in the apical part of taste buds. Large Ca2+‐activated Cl− currents blocked by Ani‐9, a selective inhibitor of TMEM16A, are measured in type I taste cells but not in type II or III taste cells. ATP indirectly activates Ca2+‐activated Cl– currents in type I cells through TMEM16A channels. These results indicate that TMEM16A is functional in type I taste cells and contribute to understanding the largely unknown physiological roles of these cells.
Collapse
Affiliation(s)
- Domenico M Guarascio
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, 34136, Italy
| | | | - Andres Hernandez-Clavijo
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, 34136, Italy
| | - Anna Menini
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, 34136, Italy
| | - Simone Pifferi
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, 34136, Italy.,Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, 60126, Italy
| |
Collapse
|
29
|
Bhat EA, Sajjad N, Banawas S, Khan J. Human CALHM5: Insight in large pore lipid gating ATP channel and associated neurological pathologies. Mol Cell Biochem 2021; 476:3711-3718. [PMID: 34089472 DOI: 10.1007/s11010-021-04198-y] [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: 01/15/2021] [Accepted: 05/27/2021] [Indexed: 10/21/2022]
Abstract
Recently calcium homeostasis modulators (CALHMs) are identified as ATP release channels play crucial role in functioning of neurons including gustatory signaling and neuronal excitability. Pathologies of Alzheimer's disease and depression have been associated with the dysfunction of CALHMs. Recently, CALHMs has been emerged as an important therapeutic research particularly in neurobiological studies. CALHM1 is most extensively studied among CALHMs and is an ATP and ion channel that is activated by membrane depolarization or removal of extracellular Ca2+. Despite the emerged role of CALHM5 shown by an recently assembled data; however, the neuronal function remains obscure until the first Cryo-EM structure of CALHM5 was recently solved by various research group which acts as a template to study the hidden functional properties of the CALHM5 protein based on structure function mechanism. It provides insight in some of the different pathophysiological roles. CALHM5 structure showed an abnormally large pore channel structure assembled as an undecamer with four transmembrane helices (TM1-TM4), an N-terminal helix (NTH), an extracellular loop region and an intracellular C-terminal domain (CTD) that consists of three α-helices CH1-3. The TM1 and NTH were always poorly defined among all CALHMs; however, these regions were well defined in CALHM5 channel structure. In this context, this review will provide insight in structure, function and mechanism to understand its significant role in pathological diseases particularly in Alzheimer's disease. Moreover, it focuses on CALHM5 structure and recent associated properties based on Cryo-EM research.
Collapse
Affiliation(s)
- Eijaz Ahmed Bhat
- Life Science Institute, Zhejiang University, Hangzhou, Zhejiang, 310058, P.R. China. .,Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, India.
| | - Nasreena Sajjad
- Department of Biochemistry, University of Kashmir, Hazratbal, Jammu and Kashmir, India
| | - Saeed Banawas
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah, 11952, Kingdom of Saudi Arabia. .,Health and Basic Sciences Research Center, Majmaah University, Majmaah, 11952, Saudi Arabia. .,Departments of Biomedical Sciences, Oregon State University, Corvallis, OR, 97331, USA.
| | - Johra Khan
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah, 11952, Kingdom of Saudi Arabia.,Health and Basic Sciences Research Center, Majmaah University, Majmaah, 11952, Saudi Arabia
| |
Collapse
|
30
|
Sabirov RZ, Islam MR, Okada T, Merzlyak PG, Kurbannazarova RS, Tsiferova NA, Okada Y. The ATP-Releasing Maxi-Cl Channel: Its Identity, Molecular Partners and Physiological/Pathophysiological Implications. Life (Basel) 2021; 11:life11060509. [PMID: 34073084 PMCID: PMC8229958 DOI: 10.3390/life11060509] [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: 04/30/2021] [Accepted: 05/27/2021] [Indexed: 12/18/2022] Open
Abstract
The Maxi-Cl phenotype accounts for the majority (app. 60%) of reports on the large-conductance maxi-anion channels (MACs) and has been detected in almost every type of cell, including placenta, endothelium, lymphocyte, cardiac myocyte, neuron, and glial cells, and in cells originating from humans to frogs. A unitary conductance of 300-400 pS, linear current-to-voltage relationship, relatively high anion-to-cation selectivity, bell-shaped voltage dependency, and sensitivity to extracellular gadolinium are biophysical and pharmacological hallmarks of the Maxi-Cl channel. Its identification as a complex with SLCO2A1 as a core pore-forming component and two auxiliary regulatory proteins, annexin A2 and S100A10 (p11), explains the activation mechanism as Tyr23 dephosphorylation at ANXA2 in parallel with calcium binding at S100A10. In the resting state, SLCO2A1 functions as a prostaglandin transporter whereas upon activation it turns to an anion channel. As an efficient pathway for chloride, Maxi-Cl is implicated in a number of physiologically and pathophysiologically important processes, such as cell volume regulation, fluid secretion, apoptosis, and charge transfer. Maxi-Cl is permeable for ATP and other small signaling molecules serving as an electrogenic pathway in cell-to-cell signal transduction. Mutations at the SLCO2A1 gene cause inherited bone and gut pathologies and malignancies, signifying the Maxi-Cl channel as a perspective pharmacological target.
Collapse
Affiliation(s)
- Ravshan Z. Sabirov
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
- Correspondence: (R.Z.S.); (Y.O.); Tel.: +81-46-858-1501 (Y.O.); Fax: +81-46-858-1542 (Y.O.)
| | - Md. Rafiqul Islam
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Department of Biochemistry and Molecular Biology, Jagannath University, Dhaka 1100, Bangladesh
| | - Toshiaki Okada
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Veneno Technologies Co. Ltd., Tsukuba 305-0031, Japan
| | - Petr G. Merzlyak
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
| | - Ranokhon S. Kurbannazarova
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
| | - Nargiza A. Tsiferova
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
| | - Yasunobu Okada
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
- Department of Physiology, School of Medicine, Aichi Medical University, Nagakute 480-1195, Japan
- Correspondence: (R.Z.S.); (Y.O.); Tel.: +81-46-858-1501 (Y.O.); Fax: +81-46-858-1542 (Y.O.)
| |
Collapse
|
31
|
Mim C, Perkins G, Dahl G. Structure versus function: Are new conformations of pannexin 1 yet to be resolved? J Gen Physiol 2021; 153:211971. [PMID: 33835130 PMCID: PMC8042604 DOI: 10.1085/jgp.202012754] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pannexin 1 (Panx1) plays a decisive role in multiple physiological and pathological settings, including oxygen delivery to tissues, mucociliary clearance in airways, sepsis, neuropathic pain, and epilepsy. It is widely accepted that Panx1 exerts its role in the context of purinergic signaling by providing a transmembrane pathway for ATP. However, under certain conditions, Panx1 can also act as a highly selective membrane channel for chloride ions without ATP permeability. A recent flurry of publications has provided structural information about the Panx1 channel. However, while these structures are consistent with a chloride selective channel, none show a conformation with strong support for the ATP release function of Panx1. In this Viewpoint, we critically assess the existing evidence for the function and structure of the Panx1 channel and conclude that the structure corresponding to the ATP permeation pathway is yet to be determined. We also list a set of additional topics needing attention and propose ways to attain the large-pore, ATP-permeable conformation of the Panx1 channel.
Collapse
Affiliation(s)
- Carsten Mim
- Department of Biomedical Engineering and Health Systems Royal Institute of Technology, Huddinge, Sweden
| | - Guy Perkins
- National Center for Microscopy and Imaging Research, University of California, San Diego School of Medicine, La Jolla, CA
| | - Gerhard Dahl
- Department of Physiology, University of Miami School of Medicine, Miami, FL
| |
Collapse
|
32
|
Zhang I, Hu H. Store-Operated Calcium Channels in Physiological and Pathological States of the Nervous System. Front Cell Neurosci 2020; 14:600758. [PMID: 33328896 PMCID: PMC7732603 DOI: 10.3389/fncel.2020.600758] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/03/2020] [Indexed: 12/13/2022] Open
Abstract
Store-operated calcium channels (SOCs) are widely expressed in excitatory and non-excitatory cells where they mediate significant store-operated calcium entry (SOCE), an important pathway for calcium signaling throughout the body. While the activity of SOCs has been well studied in non-excitable cells, attention has turned to their role in neurons and glia in recent years. In particular, the role of SOCs in the nervous system has been extensively investigated, with links to their dysregulation found in a wide variety of neurological diseases from Alzheimer’s disease (AD) to pain. In this review, we provide an overview of their molecular components, expression, and physiological role in the nervous system and describe how the dysregulation of those roles could potentially lead to various neurological disorders. Although further studies are still needed to understand how SOCs are activated under physiological conditions and how they are linked to pathological states, growing evidence indicates that SOCs are important players in neurological disorders and could be potential new targets for therapies. While the role of SOCE in the nervous system continues to be multifaceted and controversial, the study of SOCs provides a potentially fruitful avenue into better understanding the nervous system and its pathologies.
Collapse
Affiliation(s)
- Isis Zhang
- Department of Anesthesiology, Rutgers New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, United States
| | - Huijuan Hu
- Department of Anesthesiology, Rutgers New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, United States
| |
Collapse
|
33
|
Jeon YK, Choi SW, Kwon JW, Woo J, Choi SW, Kim SJ, Kim SJ. Thermosensitivity of the voltage-dependent activation of calcium homeostasis modulator 1 (calhm1) ion channel. Biochem Biophys Res Commun 2020; 534:590-596. [PMID: 33199024 DOI: 10.1016/j.bbrc.2020.11.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 11/08/2020] [Indexed: 01/08/2023]
Abstract
Calcium homeostasis modulator 1 (calhm1) proteins form an outwardly rectifying nonselective ion channel having exceedingly slow kinetics and low sensitivity to voltage that is shifted by lowering extracellular Ca2+ ([Ca2+]e). Here we found that physiological temperature dramatically facilitates the voltage-dependent activation of the calhm1 current (Icalhm1); increased amplitude (Q10, 7-15) and fastened speed of activation. Also, the leftward shift of the half-activation voltage (V1/2) was similary observed in the normal and lower [Ca2+]e. Since calhm1 is highly expressed in the brain and taste cells, the thermosensitivity should be considered in their electrophysiology.
Collapse
Affiliation(s)
- Young Keul Jeon
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Si Won Choi
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Jae Won Kwon
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Joohan Woo
- Department of Physiology and Ion Channel Disease Research Center, Dongguk University College of Medicine, Seoul, Republic of Korea
| | - Seong Woo Choi
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Sang Jeong Kim
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
| |
Collapse
|
34
|
Yang W, Wang Y, Guo J, He L, Zhou Y, Zheng H, Liu Z, Zhu P, Zhang XC. Cryo-electron microscopy structure of CLHM1 ion channel from Caenorhabditis elegans. Protein Sci 2020; 29:1803-1815. [PMID: 32557855 PMCID: PMC7380676 DOI: 10.1002/pro.3904] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 02/02/2023]
Abstract
Calcium homeostasis modulators (CALHMs/CLHMs) comprise a family of pore-forming protein complexes assembling into voltage-gated, Ca2+ -sensitive, nonselective channels. These complexes contain an ion-conduction pore sufficiently wide to permit the passing of ATP molecules serving as neurotransmitters. While their function and structure information is accumulating, the precise mechanisms of these channel complexes remain to be full understood. Here, we present the structure of the Caenorhabditis elegans CLHM1 channel in its open state solved through single-particle cryo-electron microscopy at 3.7-Å resolution. The transmembrane region of the channel structure of the dominant class shows an assembly of 10-fold rotational symmetry in one layer, and its cytoplasmic region is involved in additional twofold symmetrical packing in a tail-to-tail manner. Furthermore, we identified a series of amino acid residues critical for the regulation of CeCLHM1 channel using functional assays, electrophysiological analyses as well as structural-based analysis. Our structure and function analyses provide new insights into the mechanisms of CALHM channels.
Collapse
Affiliation(s)
- Weixin Yang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| | - Youwang Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| | - Jianli Guo
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
| | - Lingli He
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
| | - Ye Zhou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
| | - Hui Zheng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
| | - Zhenfeng Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| | - Ping Zhu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| | - Xuejun C. Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in BiomacromoleculesInstitute of Biophysics, Chinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| |
Collapse
|
35
|
Demura K, Kusakizako T, Shihoya W, Hiraizumi M, Nomura K, Shimada H, Yamashita K, Nishizawa T, Taruno A, Nureki O. Cryo-EM structures of calcium homeostasis modulator channels in diverse oligomeric assemblies. SCIENCE ADVANCES 2020; 6:eaba8105. [PMID: 32832629 PMCID: PMC7439320 DOI: 10.1126/sciadv.aba8105] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 06/03/2020] [Indexed: 05/08/2023]
Abstract
Calcium homeostasis modulator (CALHM) family proteins are Ca2+-regulated adenosine triphosphate (ATP)-release channels involved in neural functions including neurotransmission in gustation. Here, we present the cryo-electron microscopy (EM) structures of killifish CALHM1, human CALHM2, and Caenorhabditis elegans CLHM-1 at resolutions of 2.66, 3.4, and 3.6 Å, respectively. The CALHM1 octamer structure reveals that the N-terminal helix forms the constriction site at the channel pore in the open state and modulates the ATP conductance. The CALHM2 undecamer and CLHM-1 nonamer structures show the different oligomeric stoichiometries among CALHM homologs. We further report the cryo-EM structures of the chimeric construct, revealing that the intersubunit interactions at the transmembrane domain (TMD) and the TMD-intracellular domain linker define the oligomeric stoichiometry. These findings advance our understanding of the ATP conduction and oligomerization mechanisms of CALHM channels.
Collapse
Affiliation(s)
- Kanae Demura
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tsukasa Kusakizako
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Wataru Shihoya
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masahiro Hiraizumi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Discovery Technology Laboratories, Innovative Research Division, Mitsubishi Tanabe Pharma Corporation, 1000 Kamoshida, Aoba-ku, Yokohama 227-0033, Japan
| | - Kengo Nomura
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan
| | - Hiroto Shimada
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Keitaro Yamashita
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Tomohiro Nishizawa
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Akiyuki Taruno
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan
- Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
- Corresponding author. (A.T.), (O.N.)
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Corresponding author. (A.T.), (O.N.)
| |
Collapse
|
36
|
Ren Y, Wen T, Xi Z, Li S, Lu J, Zhang X, Yang X, Shen Y. Cryo-EM structure of the calcium homeostasis modulator 1 channel. SCIENCE ADVANCES 2020; 6:eaba8161. [PMID: 32832630 PMCID: PMC7439498 DOI: 10.1126/sciadv.aba8161] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 06/03/2020] [Indexed: 05/07/2023]
Abstract
Calcium homeostasis modulator 1 (CALHM1) is a voltage-gated ATP release channel that plays an important role in neural gustatory signaling and the pathogenesis of Alzheimer's disease. Here, we present a cryo-electron microscopy structure of full-length Ca2+-free CALHM1 from Danio rerio at an overall resolution of 3.1 Å. Our structure reveals an octameric architecture with a wide pore diameter of ~20 Å, presumably representing the active conformation. The overall structure is substantially different from that of the isoform CALHM2, which forms both undecameric hemichannels and gap junctions. The N-terminal small helix folds back to the pore and forms an antiparallel interaction with transmembrane helix 1. Structural analysis revealed that the extracellular loop 1 region within the dimer interface may contribute to oligomeric assembly. A positive potential belt inside the pore was identified that may modulate ion permeation. Our structure offers insights into the assembly and gating mechanism of the CALHM1 channel.
Collapse
Affiliation(s)
- Yue Ren
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300350, China
| | - Tianlei Wen
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Zhiqin Xi
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Shunjin Li
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jing Lu
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300350, China
| | - Xing Zhang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Center of Cryo Electron Microscopy, Zhejiang University School of Medicine, Hangzhou, China
| | - Xue Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300350, China
- Corresponding author. (X.Y.); (Y.S.)
| | - Yuequan Shen
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300350, China
- College of Life Sciences, Nankai University, Tianjin 300071, China
- Synergetic Innovation Center of Chemical Science and Engineering, Tianjin 300071, China
- Corresponding author. (X.Y.); (Y.S.)
| |
Collapse
|
37
|
Drożdżyk K, Sawicka M, Bahamonde-Santos MI, Jonas Z, Deneka D, Albrecht C, Dutzler R. Cryo-EM structures and functional properties of CALHM channels of the human placenta. eLife 2020; 9:e55853. [PMID: 32374262 PMCID: PMC7242029 DOI: 10.7554/elife.55853] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 05/05/2020] [Indexed: 01/08/2023] Open
Abstract
The transport of substances across the placenta is essential for the development of the fetus. Here, we were interested in the role of channels of the calcium homeostasis modulator (CALHM) family in the human placenta. By transcript analysis, we found the paralogs CALHM2, 4, and 6 to be highly expressed in this organ and upregulated during trophoblast differentiation. Based on electrophysiology, we observed that activation of these paralogs differs from the voltage- and calcium-gated channel CALHM1. Cryo-EM structures of CALHM4 display decameric and undecameric assemblies with large cylindrical pore, while in CALHM6 a conformational change has converted the pore shape into a conus that narrows at the intracellular side, thus describing distinct functional states of the channel. The pore geometry alters the distribution of lipids, which occupy the cylindrical pore of CALHM4 in a bilayer-like arrangement whereas they have redistributed in the conical pore of CALHM6 with potential functional consequences.
Collapse
Affiliation(s)
| | - Marta Sawicka
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | | | - Zaugg Jonas
- Institute of Biochemistry and Molecular Medicine, University of BernBernSwitzerland
| | - Dawid Deneka
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Christiane Albrecht
- Institute of Biochemistry and Molecular Medicine, University of BernBernSwitzerland
| | - Raimund Dutzler
- Department of Biochemistry, University of ZurichZurichSwitzerland
| |
Collapse
|
38
|
Dunn PJ, Salm EJ, Tomita S. ABC transporters control ATP release through cholesterol-dependent volume-regulated anion channel activity. J Biol Chem 2020; 295:5192-5203. [PMID: 31988241 PMCID: PMC7170513 DOI: 10.1074/jbc.ra119.010699] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 01/10/2020] [Indexed: 12/16/2022] Open
Abstract
Purinergic signaling by extracellular ATP regulates a variety of cellular events and is implicated in both normal physiology and pathophysiology. Several molecules have been associated with the release of ATP and other small molecules, but their precise contributions have been difficult to assess because of their complexity and heterogeneity. Here, we report on the results of a gain-of-function screen for modulators of hypotonicity-induced ATP release using HEK-293 cells and murine cerebellar granule neurons, along with bioluminescence, calcium FLIPR, and short hairpin RNA-based gene-silencing assays. This screen utilized the most extensive genome-wide ORF collection to date, covering 90% of human, nonredundant, protein-encoding genes. We identified two ABCG1 (ABC subfamily G member 1) variants, which regulate cellular cholesterol, as modulators of hypotonicity-induced ATP release. We found that cholesterol levels control volume-regulated anion channel-dependent ATP release. These findings reveal novel mechanisms for the regulation of ATP release and volume-regulated anion channel activity and provide critical links among cellular status, cholesterol, and purinergic signaling.
Collapse
Affiliation(s)
- Patrick J Dunn
- Department of Cellular and Molecular Physiology, Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale Kavli Institute, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Elizabeth J Salm
- Department of Cellular and Molecular Physiology, Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale Kavli Institute, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Susumu Tomita
- Department of Cellular and Molecular Physiology, Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale Kavli Institute, Yale University School of Medicine, New Haven, Connecticut 06520.
| |
Collapse
|
39
|
|
40
|
Michalski K, Syrjanen JL, Henze E, Kumpf J, Furukawa H, Kawate T. The Cryo-EM structure of pannexin 1 reveals unique motifs for ion selection and inhibition. eLife 2020; 9:e54670. [PMID: 32048993 PMCID: PMC7108861 DOI: 10.7554/elife.54670] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 02/11/2020] [Indexed: 12/24/2022] Open
Abstract
Pannexins are large-pore forming channels responsible for ATP release under a variety of physiological and pathological conditions. Although predicted to share similar membrane topology with other large-pore forming proteins such as connexins, innexins, and LRRC8, pannexins have minimal sequence similarity to these protein families. Here, we present the cryo-EM structure of a frog pannexin 1 (Panx1) channel at 3.0 Å. We find that Panx1 protomers harbor four transmembrane helices similar in arrangement to other large-pore forming proteins but assemble as a heptameric channel with a unique constriction formed by Trp74 in the first extracellular loop. Mutating Trp74 or the nearby Arg75 disrupt ion selectivity, whereas altering residues in the hydrophobic groove formed by the two extracellular loops abrogates channel inhibition by carbenoxolone. Our structural and functional study establishes the extracellular loops as important structural motifs for ion selectivity and channel inhibition in Panx1.
Collapse
Affiliation(s)
- Kevin Michalski
- Department of Molecular Medicine, Cornell UniversityIthacaUnited States
| | - Johanna L Syrjanen
- WM Keck Structural Biology Laboratory, Cold Spring Harbor LaboratoryCold Spring HarborUnited States
| | - Erik Henze
- Department of Molecular Medicine, Cornell UniversityIthacaUnited States
| | - Julia Kumpf
- Department of Molecular Medicine, Cornell UniversityIthacaUnited States
| | - Hiro Furukawa
- WM Keck Structural Biology Laboratory, Cold Spring Harbor LaboratoryCold Spring HarborUnited States
| | - Toshimitsu Kawate
- Department of Molecular Medicine, Cornell UniversityIthacaUnited States
| |
Collapse
|
41
|
Saddala MS, Lennikov A, Bouras A, Huang H. RNA-Seq reveals differential expression profiles and functional annotation of genes involved in retinal degeneration in Pde6c mutant Danio rerio. BMC Genomics 2020; 21:132. [PMID: 32033529 PMCID: PMC7006399 DOI: 10.1186/s12864-020-6550-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 01/31/2020] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Retinal degenerative diseases affect millions of people and represent the leading cause of vision loss around the world. Retinal degeneration has been attributed to a wide variety of causes, such as disruption of genes involved in phototransduction, biosynthesis, folding of the rhodopsin molecule, and the structural support of the retina. The molecular pathogenesis of the biological events in retinal degeneration is unclear; however, the molecular basis of the retinal pathological defect can be potentially determined by gene-expression profiling of the whole retina. In the present study, we analyzed the differential gene expression profile of the retina from a wild-type zebrafish and phosphodiesterase 6c (pde6c) mutant. RESULTS The datasets were downloaded from the Sequence Read Archive (SRA), and adaptors and unbiased bases were removed, and sequences were checked to ensure the quality. The reads were further aligned to the reference genome of zebrafish, and the gene expression was calculated. The differentially expressed genes (DEGs) were filtered based on the log fold change (logFC) (±4) and p-values (p < 0.001). We performed gene annotation (molecular function [MF], biological process [BP], cellular component [CC]), and determined the functional pathways Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway for the DEGs. Our result showed 216 upregulated and 3527 downregulated genes between normal and pde6c mutant zebrafish. These DEGs are involved in various KEGG pathways, such as the phototransduction (12 genes), mRNA surveillance (17 genes), phagosome (25 genes), glycolysis/gluconeogenesis (15 genes), adrenergic signaling in cardiomyocytes (29 genes), ribosome (20 genes), the citrate cycle (TCA cycle; 8 genes), insulin signaling (24 genes), oxidative phosphorylation (20 genes), and RNA transport (22 genes) pathways. Many more of all the pathway genes were down-regulated, while fewer were up-regulated in the retina of pde6c mutant zebrafish. CONCLUSIONS Our data strongly indicate that, among these genes, the above-mentioned pathways' genes as well as calcium-binding, neural damage, peptidase, immunological, and apoptosis proteins are mostly involved in the retinal and neural degeneration that cause abnormalities in photoreceptors or retinal pigment epithelium (RPE) cells.
Collapse
Affiliation(s)
- Madhu Sudhana Saddala
- School of Medicine, Department Ophthalmology, Mason Eye Institute, University of Missouri-Columbia, One Hospital Drive, MA102C, Columbia, MO, 65212, USA
- Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Anton Lennikov
- School of Medicine, Department Ophthalmology, Mason Eye Institute, University of Missouri-Columbia, One Hospital Drive, MA102C, Columbia, MO, 65212, USA
- Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Adam Bouras
- School of Medicine, Department Ophthalmology, Mason Eye Institute, University of Missouri-Columbia, One Hospital Drive, MA102C, Columbia, MO, 65212, USA
| | - Hu Huang
- School of Medicine, Department Ophthalmology, Mason Eye Institute, University of Missouri-Columbia, One Hospital Drive, MA102C, Columbia, MO, 65212, USA.
- Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA.
| |
Collapse
|
42
|
Choi W, Clemente N, Sun W, Du J, Lü W. The structures and gating mechanism of human calcium homeostasis modulator 2. Nature 2019; 576:163-167. [PMID: 31776515 DOI: 10.1038/s41586-019-1781-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 10/08/2019] [Indexed: 12/14/2022]
Abstract
Calcium homeostasis modulators (CALHMs) are voltage-gated, Ca2+-inhibited nonselective ion channels that act as major ATP release channels, and have important roles in gustatory signalling and neuronal toxicity1-3. Dysfunction of CALHMs has previously been linked to neurological disorders1. Here we present cryo-electron microscopy structures of the human CALHM2 channel in the Ca2+-free active or open state and in the ruthenium red (RUR)-bound inhibited state, at resolutions up to 2.7 Å. Our work shows that purified CALHM2 channels form both gap junctions and undecameric hemichannels. The protomer shows a mirrored arrangement of the transmembrane domains (helices S1-S4) relative to other channels with a similar topology, such as connexins, innexins and volume-regulated anion channels4-8. Upon binding to RUR, we observed a contracted pore with notable conformational changes of the pore-lining helix S1, which swings nearly 60° towards the pore axis from a vertical to a lifted position. We propose a two-section gating mechanism in which the S1 helix coarsely adjusts, and the N-terminal helix fine-tunes, the pore size. We identified a RUR-binding site near helix S1 that may stabilize this helix in the lifted conformation, giving rise to channel inhibition. Our work elaborates on the principles of CALHM2 channel architecture and symmetry, and the mechanism that underlies channel inhibition.
Collapse
Affiliation(s)
| | | | - Weinan Sun
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA.,Janelia Research Campus, Ashburn, VA, USA
| | - Juan Du
- Van Andel Institute, Grand Rapids, MI, USA.
| | - Wei Lü
- Van Andel Institute, Grand Rapids, MI, USA.
| |
Collapse
|
43
|
Vallon V, Unwin R, Inscho EW, Leipziger J, Kishore BK. Extracellular Nucleotides and P2 Receptors in Renal Function. Physiol Rev 2019; 100:211-269. [PMID: 31437091 DOI: 10.1152/physrev.00038.2018] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The understanding of the nucleotide/P2 receptor system in the regulation of renal hemodynamics and transport function has grown exponentially over the last 20 yr. This review attempts to integrate the available data while also identifying areas of missing information. First, the determinants of nucleotide concentrations in the interstitial and tubular fluids of the kidney are described, including mechanisms of cellular release of nucleotides and their extracellular breakdown. Then the renal cell membrane expression of P2X and P2Y receptors is discussed in the context of their effects on renal vascular and tubular functions. Attention is paid to effects on the cortical vasculature and intraglomerular structures, autoregulation of renal blood flow, tubuloglomerular feedback, and the control of medullary blood flow. The role of the nucleotide/P2 receptor system in the autocrine/paracrine regulation of sodium and fluid transport in the tubular and collecting duct system is outlined together with its role in integrative sodium and fluid homeostasis and blood pressure control. The final section summarizes the rapidly growing evidence indicating a prominent role of the extracellular nucleotide/P2 receptor system in the pathophysiology of the kidney and aims to identify potential therapeutic opportunities, including hypertension, lithium-induced nephropathy, polycystic kidney disease, and kidney inflammation. We are only beginning to unravel the distinct physiological and pathophysiological influences of the extracellular nucleotide/P2 receptor system and the associated therapeutic perspectives.
Collapse
Affiliation(s)
- Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego & VA San Diego Healthcare System, San Diego, California; Centre for Nephrology, Division of Medicine, University College London, London, United Kingdom; IMED ECD CVRM R&D, AstraZeneca, Gothenburg, Sweden; Department of Medicine, Division of Nephrology, The University of Alabama at Birmingham, Birmingham, Alabama; Department of Biomedicine/Physiology, Aarhus University, Aarhus, Denmark; Departments of Internal Medicine and Nutrition and Integrative Physiology, and Center on Aging, University of Utah Health & Nephrology Research, VA Salt Lake City Healthcare System, Salt Lake City, Utah
| | - Robert Unwin
- Departments of Medicine and Pharmacology, University of California San Diego & VA San Diego Healthcare System, San Diego, California; Centre for Nephrology, Division of Medicine, University College London, London, United Kingdom; IMED ECD CVRM R&D, AstraZeneca, Gothenburg, Sweden; Department of Medicine, Division of Nephrology, The University of Alabama at Birmingham, Birmingham, Alabama; Department of Biomedicine/Physiology, Aarhus University, Aarhus, Denmark; Departments of Internal Medicine and Nutrition and Integrative Physiology, and Center on Aging, University of Utah Health & Nephrology Research, VA Salt Lake City Healthcare System, Salt Lake City, Utah
| | - Edward W Inscho
- Departments of Medicine and Pharmacology, University of California San Diego & VA San Diego Healthcare System, San Diego, California; Centre for Nephrology, Division of Medicine, University College London, London, United Kingdom; IMED ECD CVRM R&D, AstraZeneca, Gothenburg, Sweden; Department of Medicine, Division of Nephrology, The University of Alabama at Birmingham, Birmingham, Alabama; Department of Biomedicine/Physiology, Aarhus University, Aarhus, Denmark; Departments of Internal Medicine and Nutrition and Integrative Physiology, and Center on Aging, University of Utah Health & Nephrology Research, VA Salt Lake City Healthcare System, Salt Lake City, Utah
| | - Jens Leipziger
- Departments of Medicine and Pharmacology, University of California San Diego & VA San Diego Healthcare System, San Diego, California; Centre for Nephrology, Division of Medicine, University College London, London, United Kingdom; IMED ECD CVRM R&D, AstraZeneca, Gothenburg, Sweden; Department of Medicine, Division of Nephrology, The University of Alabama at Birmingham, Birmingham, Alabama; Department of Biomedicine/Physiology, Aarhus University, Aarhus, Denmark; Departments of Internal Medicine and Nutrition and Integrative Physiology, and Center on Aging, University of Utah Health & Nephrology Research, VA Salt Lake City Healthcare System, Salt Lake City, Utah
| | - Bellamkonda K Kishore
- Departments of Medicine and Pharmacology, University of California San Diego & VA San Diego Healthcare System, San Diego, California; Centre for Nephrology, Division of Medicine, University College London, London, United Kingdom; IMED ECD CVRM R&D, AstraZeneca, Gothenburg, Sweden; Department of Medicine, Division of Nephrology, The University of Alabama at Birmingham, Birmingham, Alabama; Department of Biomedicine/Physiology, Aarhus University, Aarhus, Denmark; Departments of Internal Medicine and Nutrition and Integrative Physiology, and Center on Aging, University of Utah Health & Nephrology Research, VA Salt Lake City Healthcare System, Salt Lake City, Utah
| |
Collapse
|
44
|
Dufek S, Cheshire C, Levine AP, Trompeter RS, Issler N, Stubbs M, Mozere M, Gupta S, Klootwijk E, Patel V, Hothi D, Waters A, Webb H, Tullus K, Jenkins L, Godinho L, Levtchenko E, Wetzels J, Knoers N, Teeninga N, Nauta J, Shalaby M, Eldesoky S, Kari JA, Thalgahagoda S, Ranawaka R, Abeyagunawardena A, Adeyemo A, Kristiansen M, Gbadegesin R, Webb NJ, Gale DP, Stanescu HC, Kleta R, Bockenhauer D. Genetic Identification of Two Novel Loci Associated with Steroid-Sensitive Nephrotic Syndrome. J Am Soc Nephrol 2019; 30:1375-1384. [PMID: 31263063 DOI: 10.1681/asn.2018101054] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Accepted: 04/22/2019] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND Steroid-sensitive nephrotic syndrome (SSNS), the most common form of nephrotic syndrome in childhood, is considered an autoimmune disease with an established classic HLA association. However, the precise etiology of the disease is unclear. In other autoimmune diseases, the identification of loci outside the classic HLA region by genome-wide association studies (GWAS) has provided critical insights into disease pathogenesis. Previously conducted GWAS of SSNS have not identified non-HLA loci achieving genome-wide significance. METHODS In an attempt to identify additional loci associated with SSNS, we conducted a GWAS of a large cohort of European ancestry comprising 422 ethnically homogeneous pediatric patients and 5642 ethnically matched controls. RESULTS The GWAS found three loci that achieved genome-wide significance, which explain approximately 14% of the genetic risk for SSNS. It confirmed the previously reported association with the HLA-DR/DQ region (lead single-nucleotide polymorphism [SNP] rs9273542, P=1.59×10-43; odds ratio [OR], 3.39; 95% confidence interval [95% CI], 2.86 to 4.03) and identified two additional loci outside the HLA region on chromosomes 4q13.3 and 6q22.1. The latter contains the calcium homeostasis modulator family member 6 gene CALHM6 (previously called FAM26F). CALHM6 is implicated in immune response modulation; the lead SNP (rs2637678, P=1.27×10-17; OR, 0.51; 95% CI, 0.44 to 0.60) exhibits strong expression quantitative trait loci effects, the risk allele being associated with lower lymphocytic expression of CALHM6. CONCLUSIONS Because CALHM6 is implicated in regulating the immune response to infection, this may provide an explanation for the typical triggering of SSNS onset by infections. Our results suggest that a genetically conferred risk of immune dysregulation may be a key component in the pathogenesis of SSNS.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | - Vaksha Patel
- Great Ormond Street Hospital, London, United Kingdom
| | - Daljit Hothi
- Great Ormond Street Hospital, London, United Kingdom
| | - Aoife Waters
- Great Ormond Street Hospital, London, United Kingdom
| | - Hazel Webb
- Great Ormond Street Hospital, London, United Kingdom
| | - Kjell Tullus
- Great Ormond Street Hospital, London, United Kingdom
| | - Lucy Jenkins
- Great Ormond Street Hospital, London, United Kingdom
| | | | - Elena Levtchenko
- University Hospitals Leuven and University of Leuven, Leuven, Belgium
| | - Jack Wetzels
- Nephrology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Nine Knoers
- Department of Genetics, UMC Groningen, Groningen, The Netherlands
| | - Nynke Teeninga
- Department of Pediatric Nephrology, Erasmus University Medical Centre-Sophia Children's Hospital, Rotterdam, The Netherlands
| | - Jeroen Nauta
- Department of Pediatric Nephrology, Erasmus University Medical Centre-Sophia Children's Hospital, Rotterdam, The Netherlands
| | - Mohamed Shalaby
- Pediatric Nephrology Center of Excellence, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Sherif Eldesoky
- Pediatric Nephrology Center of Excellence, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Jameela A Kari
- Pediatric Nephrology Center of Excellence, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | | | - Randula Ranawaka
- Department of Paediatrics, University of Peradeniya, Peradeniya, Sri Lanka
| | | | | | - Mark Kristiansen
- University College London Genomics, Institute of Child Health, University College London, London, United Kingdom
| | - Rasheed Gbadegesin
- Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina; and
| | - Nicholas J Webb
- Department of Paediatric Nephrology and.,NIHR Manchester Clinical Research Facility, Manchester Academic Health Science Centre, Royal Manchester Children's Hospital, Manchester, United Kingdom
| | | | | | | | | |
Collapse
|
45
|
Rahman M, Sun R, Mukherjee S, Nilius B, Janssen LJ. TRPV4 Stimulation Releases ATP via Pannexin Channels in Human Pulmonary Fibroblasts. Am J Respir Cell Mol Biol 2019; 59:87-95. [PMID: 29393654 DOI: 10.1165/rcmb.2017-0413oc] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
We previously described several ionic conductances in human pulmonary fibroblasts, including one activated by two structurally distinct TRPV4 (transient receptor potential, vanilloid-type, subtype 4)-channel agonists: 4αPDD (4α-phorbol-12,13-didecanoate) and GSK1016790A. However, the TRPV4-activated current exhibited peculiar properties: it developed slowly over many minutes, exhibited reversal potentials that could vary by tens of millivolts even within a given cell, and was not easily reversed by subsequent addition of two distinct TRPV4-selective blockers (RN-1734 and HC-067047). In this study, we characterized that conductance more carefully. We found that 4αPDD stimulated a delayed release of ATP into the extracellular space, which was reduced by genetic silencing of pannexin expression, and that the 4αPDD-evoked current could be blocked by apyrase (which rapidly degrades ATP) or by the P2Y purinergic receptor/channel blocker pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), and could be mimicked by exogenous addition of ATP. In addition, we found that the 4αPDD-evoked current was blocked by pretreatment with RN-1734 or HC-067047, by Gd3+ or La3+, or by two distinct blockers of pannexin channels (carbenoxolone and probenecid), but not by a blocker of connexin hemichannels (flufenamic acid). We also found expression of TRPV4- and pannexin-channel proteins. 4αPDD markedly increased calcium flashing in our cells. The latter was abrogated by the P2Y channel blocker PPADS, and the 4αPDD-evoked current was eliminated by loading the cytosol with 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or by inhibiting Ca2+/calmodulin-sensitive kinase II using KN93. Altogether, we interpret these findings as suggesting that 4αPDD triggers the release of ATP via pannexin channels, which in turn acts in an autocrine and/or paracrine fashion to stimulate PPADS-sensitive purinergic receptors on human pulmonary fibroblasts.
Collapse
Affiliation(s)
- Mozibur Rahman
- 1 Firestone Institute for Respiratory Health, St. Joseph's Hospital, and.,2 Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - Rui Sun
- 1 Firestone Institute for Respiratory Health, St. Joseph's Hospital, and.,2 Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - Subhendu Mukherjee
- 1 Firestone Institute for Respiratory Health, St. Joseph's Hospital, and.,2 Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - Bernd Nilius
- 3 Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Luke J Janssen
- 1 Firestone Institute for Respiratory Health, St. Joseph's Hospital, and.,2 Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| |
Collapse
|
46
|
CALHM1/CALHM3 channel is intrinsically sorted to the basolateral membrane of epithelial cells including taste cells. Sci Rep 2019; 9:2681. [PMID: 30804437 PMCID: PMC6390109 DOI: 10.1038/s41598-019-39593-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/12/2018] [Indexed: 12/20/2022] Open
Abstract
The CALHM1/CALHM3 channel in the basolateral membrane of polarized taste cells mediates neurotransmitter release. However, mechanisms regulating its localization remain unexplored. Here, we identified CALHM1/CALHM3 in the basolateral membrane of type II taste cells in discrete puncta localized close to afferent nerve fibers. As in taste cells, CALHM1/CALHM3 was present in the basolateral membrane of model epithelia, although it was distributed throughout the membrane and did not show accumulation in puncta. We identified canonical basolateral sorting signals in CALHM1 and CALHM3: tyrosine-based and dileucine motifs. However, basolateral sorting remained intact in mutated channels lacking those signals, suggesting that non-canonical signals reside elsewhere. Our study demonstrates intrinsic basolateral sorting of CALHM channels in polarized cells, and provides mechanistic insights.
Collapse
|
47
|
Giuliani AL, Sarti AC, Di Virgilio F. Extracellular nucleotides and nucleosides as signalling molecules. Immunol Lett 2018; 205:16-24. [PMID: 30439478 DOI: 10.1016/j.imlet.2018.11.006] [Citation(s) in RCA: 130] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/09/2018] [Indexed: 12/26/2022]
Abstract
Extracellular nucleotides, mainly ATP, but also ADP, UTP, UDP and UDP-sugars, adenosine, and adenine base participate in the "purinergic signalling" pathway, an ubiquitous system of cell-to-cell communication. Fundamental pathophysiological processes such as tissue homeostasis, wound healing, neurodegeneration, immunity, inflammation and cancer are modulated by purinergic signalling. Nucleotides can be released from cells via unspecific or specific mechanisms. A non-regulated nucleotide release can occur from damaged or dying cells, whereas exocytotic granules, plasma membrane-derived microvesicles, membrane channels (connexins, pannexins, calcium homeostasis modulator (CALHM) channels and P2X7 receptor) or specific ATP binding cassette (ABC) transporters are involved in the controlled release. Four families of specific receptors, i.e. nucleotide P2X and P2Y receptors, adenosine P1 receptors, and the adenine-selective P0 receptor, and several ecto- nucleotidases are essential components of the "purinergic signalling" pathway. Thanks to the activity of ecto-nucleotidases, ATP (and possibly other nucleotides) are degraded into additional messenger molecules with specific action. The final biological effects depend on the type and amount of released nucleotides, their modification by ecto-nucleotidases, and their possible cellular re-uptake. Overall, these processes confer a remarkable level of selectivity and plasticity to purinergic signalling that makes this network one of the most relevant extracellular messenger systems in higher organisms.
Collapse
Affiliation(s)
- Anna Lisa Giuliani
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferarra, Italy
| | - Alba Clara Sarti
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferarra, Italy
| | - Francesco Di Virgilio
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferarra, Italy.
| |
Collapse
|
48
|
Zhou P, Polovitskaya MM, Jentsch TJ. LRRC8 N termini influence pore properties and gating of volume-regulated anion channels (VRACs). J Biol Chem 2018; 293:13440-13451. [PMID: 29925591 PMCID: PMC6120214 DOI: 10.1074/jbc.ra118.002853] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 06/19/2018] [Indexed: 12/22/2022] Open
Abstract
Volume-regulated anion channels (VRACs) are crucial for cell volume regulation and have various roles in physiology and pathology. VRACs were recently discovered to be formed by heteromers of leucine-rich repeat–containing 8 (LRRC8) proteins. However, the structural determinants of VRAC permeation and gating remain largely unknown. We show here that the short stretch preceding the first LRRC8 transmembrane domain determines VRAC conductance, ion permeability, and inactivation gating. Substituted-cysteine accessibility studies revealed that several of the first 15 LRRC8 residues are functionally important and exposed to a hydrophilic environment. Substituting glutamate 6 with cysteine decreased the amplitudes of swelling-activated ICl,vol currents, strongly increased iodide-over-chloride permeability, and markedly shifted the voltage dependence of channel inactivation. Importantly, these effects were reversed by 2-sulfonatoethyl methanethiosulfonate, which restores the negative charge at this amino acid position. Cd2+-mediated blocking of ICl,vol in cysteine variants suggested that the LRRC8 N termini come close together in the multimeric channel complex and might form part of the pore. We propose a model in which the N termini of the LRRC8 subunits line the cytoplasmic portion of the VRAC pore, possibly by folding back into the ion permeation pathway.
Collapse
Affiliation(s)
- Pingzheng Zhou
- From the Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), D-13125 Berlin, Germany
| | - Maya M Polovitskaya
- From the Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), D-13125 Berlin, Germany.,Graduate Program, Faculty of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Thomas J Jentsch
- From the 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, and
| |
Collapse
|
49
|
Yamada T, Strange K. Intracellular and extracellular loops of LRRC8 are essential for volume-regulated anion channel function. J Gen Physiol 2018; 150:1003-1015. [PMID: 29853476 PMCID: PMC6028502 DOI: 10.1085/jgp.201812016] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 04/02/2018] [Accepted: 05/01/2018] [Indexed: 12/13/2022] Open
Abstract
The volume-regulated anion channel (VRAC) is expressed ubiquitously in vertebrate cells and mediates swelling-induced release of Cl- and organic solutes. Recent studies by several laboratories have demonstrated conclusively that VRAC is encoded by members of the leucine-rich repeat containing 8 (Lrrc8) gene family, which comprises five members, termed Lrrc8a-e. Numerous observations indicate that VRAC is a heteromeric channel comprising the essential subunit LRRC8A and one or more of the other LRRC8 paralogs. Here we demonstrate that the intracellular loop (IL) connecting transmembrane domains 2 and 3 of LRRC8A and the first extracellular loop (EL1) connecting transmembrane domains 1 and 2 of LRRC8C, LRRC8D, or LRRC8E are both essential for VRAC activity. We generate homomeric VRACs by replacing EL1 of LRRC8A with that of LRRC8C and demonstrate normal regulation by cell swelling and shrinkage. We also observe normal volume-dependent regulation in VRAC homomers in which the IL of LRRC8C, LRRC8D, or LRRC8E is replaced with the LRRC8A IL. A 25-amino acid sequence unique to the LRRC8A IL is sufficient to generate homomeric VRAC activity when inserted into the corresponding region of LRRC8C and LRRC8E. LRRC8 chimeras containing these partial LRRC8A IL sequences exhibit altered anion permeability, rectification, and voltage sensitivity, suggesting that the LRRC8A IL plays a role in VRAC pore structure and function. Our studies provide important new insights into the structure/function roles of the LRRC8 EL1 and IL. Homomeric LRRC8 channels will simplify future studies aimed at understanding channel structure and the longstanding and vexing problem of how VRAC is regulated by cell volume changes.
Collapse
|
50
|
Wang J, Jackson DG, Dahl G. Cationic control of Panx1 channel function. Am J Physiol Cell Physiol 2018; 315:C279-C289. [PMID: 29719168 DOI: 10.1152/ajpcell.00303.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The sequence and predicted membrane topology of pannexin1 (Panx1) places it in the family of gap junction proteins. However, rather than forming gap junction channels, Panx1 forms channels in the nonjunctional membrane. Panx1 operates in two distinct open states, depending on the mode of stimulation. The exclusively voltage-gated channel has a small conductance (<100 pS) and is highly selective for the flux of chloride ions. The Panx1 channel activated by various physiological stimuli or by increased concentrations of extracellular potassium ions has a large conductance (~500 pS, however, with multiple, long-lasting subconductance states) and is nonselectively permeable to small molecules, including ATP. To test whether the two open conformations also differ pharmacologically, the effects of di-and trivalent cations on the two Panx1 channel conformations were investigated. The rationale for this venture was that, under certain experimental conditions, ATP release from cells can be inhibited by multivalent cations, yet the literature indicates that the ATP release channel Panx1 is not affected by these ions. Consistent with previous reports, the Panx1 channel was not activated by removal of extracellular Ca2+ and the currents through the voltage-activated channel were not altered by Ca2+, Zn2+, Ba2+, or Gd3+. In contrast, the Panx1 channel activated to the large channel conformation by extracellular K+, osmotic stress, or low oxygen was inhibited by the multivalent cations in a dose-dependent way. Thus, monovalent cations activated the Panx1 channel from the closed state to the "large" conformation, while di- and trivalent cations exclusively inhibited this large channel conformation.
Collapse
Affiliation(s)
- Junjie Wang
- Department of Physiology and Biophysics, University of Miami School of Medicine , Miami, Florida
| | - David George Jackson
- Department of Physiology and Biophysics, University of Miami School of Medicine , Miami, Florida
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami School of Medicine , Miami, Florida
| |
Collapse
|