1
|
Paylar B, Bezabhe YH, Jass J, Olsson PE. Exploring the Sublethal Impacts of Cu and Zn on Daphnia magna: a transcriptomic perspective. BMC Genomics 2024; 25:790. [PMID: 39160502 PMCID: PMC11331620 DOI: 10.1186/s12864-024-10701-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 08/12/2024] [Indexed: 08/21/2024] Open
Abstract
Metal contamination of aquatic environments remains a major concern due to their persistence. The water flea Daphnia magna is an important model species for metal toxicity studies and water quality assessment. However, most research has focused on physiological endpoints such as mortality, growth, and reproduction in laboratory settings, as well as neglected toxicogenomic responses. Copper (Cu) and zinc (Zn) are essential trace elements that play crucial roles in many biological processes, including iron metabolism, connective tissue formation, neurotransmitter synthesis, DNA synthesis, and immune function. Excess amounts of these metals result in deviations from homeostasis and may induce toxic responses. In this study, we analyzed Daphnia magna transcriptomic responses to IC5 levels of Cu (120 µg/L) and Zn (300 µg/L) in environmental water obtained from a pristine lake with adjusted water hardness (150 mg/L CaCO3). The study was carried out to gain insights into the Cu and Zn regulated stress response mechanisms in Daphnia magna at transcriptome level. A total of 2,688 and 3,080 genes were found to be differentially expressed (DEG) between the control and Cu and the control and Zn, respectively. There were 1,793 differentially expressed genes in common for both Cu and Zn, whereas the number of unique DEGs for Cu and Zn were 895 and 1,287, respectively. Gene ontology and KEGG pathways enrichment were carried out to identify the molecular functions and biological processes affected by metal exposures. In addition to well-known biomarkers, novel targets for metal toxicity screening at the genomic level were identified.
Collapse
Affiliation(s)
- Berkay Paylar
- Biology, The Life Science Center, School of Science and Technology, Örebro University, SE-701 82, Örebro, Sweden
- , Örebro, Sweden
| | - Yared H Bezabhe
- Biology, The Life Science Center, School of Science and Technology, Örebro University, SE-701 82, Örebro, Sweden
- , Örebro, Sweden
| | - Jana Jass
- Biology, The Life Science Center, School of Science and Technology, Örebro University, SE-701 82, Örebro, Sweden
- , Örebro, Sweden
| | - Per-Erik Olsson
- Biology, The Life Science Center, School of Science and Technology, Örebro University, SE-701 82, Örebro, Sweden.
- , Örebro, Sweden.
| |
Collapse
|
2
|
Arreola J, López-Romero AE, Huerta M, Guzmán-Hernández ML, Pérez-Cornejo P. Insights into the function and regulation of the calcium-activated chloride channel TMEM16A. Cell Calcium 2024; 121:102891. [PMID: 38772195 DOI: 10.1016/j.ceca.2024.102891] [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: 02/27/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 05/23/2024]
Abstract
The TMEM16A channel, a member of the TMEM16 protein family comprising chloride (Cl-) channels and lipid scramblases, is activated by the free intracellular Ca2+ increments produced by inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release after GqPCRs or Ca2+ entry through cationic channels. It is a ubiquitous transmembrane protein that participates in multiple physiological functions essential to mammals' lives. TMEM16A structure contains two identical 10-segment monomers joined at their transmembrane segment 10. Each monomer harbours one independent hourglass-shaped pore gated by Ca2+ ligation to an orthosteric site adjacent to the pore and controlled by two gates. The orthosteric site is created by assembling negatively charged glutamate side chains near the pore´s cytosolic end. When empty, this site generates an electrostatic barrier that controls channel rectification. In addition, an isoleucine-triad forms a hydrophobic gate at the boundary of the cytosolic vestibule and the inner side of the neck. When the cytosolic Ca2+ rises, one or two Ca2+ ions bind to the orthosteric site in a voltage (V)-dependent manner, thus neutralising the electrostatic barrier and triggering an allosteric gating mechanism propagating via transmembrane segment 6 to the hydrophobic gate. These coordinated events lead to pore opening, allowing the Cl- flux to ensure the physiological response. The Ca2+-dependent function of TMEM16A is highly regulated. Anions with higher permeability than Cl- facilitate V dependence by increasing the Ca2+ sensitivity, intracellular protons can replace Ca2+ and induce channel opening, and phosphatidylinositol 4,5-bisphosphate bound to four cytosolic sites likely maintains Ca2+ sensitivity. Additional regulation is afforded by cytosolic proteins, most likely by phosphorylation and protein-protein interaction mechanisms.
Collapse
Affiliation(s)
- Jorge Arreola
- Jorge Arreola, Physics Institute of Universidad Autónoma de San Luis Potosí. Av. Parque Chapultepec 1570, Privadas del Pedregal, 78295 San Luis Potosí, SLP., Mexico.
| | - Ana Elena López-Romero
- Jorge Arreola, Physics Institute of Universidad Autónoma de San Luis Potosí. Av. Parque Chapultepec 1570, Privadas del Pedregal, 78295 San Luis Potosí, SLP., Mexico
| | - Miriam Huerta
- Jorge Arreola, Physics Institute of Universidad Autónoma de San Luis Potosí. Av. Parque Chapultepec 1570, Privadas del Pedregal, 78295 San Luis Potosí, SLP., Mexico
| | - María Luisa Guzmán-Hernández
- Catedrática CONAHCYT, Department of Physiology and Biophysics, School of Medicine, Universidad Autónoma de San Luis Potosí. Ave. V. Carranza 2905, Los Filtros, San Luis Potosí, SLP 78210, Mexico
| | - Patricia Pérez-Cornejo
- Department of Physiology and Biophysics, School of Medicine, Universidad Autónoma de San Luis Potosí. Ave. V. Carranza 2905, Los Filtros, San Luis Potosí, SLP 78210, Mexico
| |
Collapse
|
3
|
Ni K, Che B, Gu R, Wang C, Xu H, Li H, Cen S, Luo M, Deng L. BitterDB database analysis plus cell stiffness screening identify flufenamic acid as the most potent TAS2R14-based relaxant of airway smooth muscle cells for therapeutic bronchodilation. Theranostics 2024; 14:1744-1763. [PMID: 38389834 PMCID: PMC10879871 DOI: 10.7150/thno.92492] [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: 11/22/2023] [Accepted: 02/07/2024] [Indexed: 02/24/2024] Open
Abstract
Rationale: Bitter taste receptors (TAS2Rs) are abundantly expressed in airway smooth muscle cells (ASMCs), which have been recognized as promising targets for bitter agonists to initiate relaxation and thereby prevent excessive airway constriction as the main characteristic of asthma. However, due to the current lack of tested safe and potent agonists functioning at low effective concentrations, there has been no clinically approved TAS2R-based drug for bronchodilation in asthma therapy. This study thus aimed at exploring TAS2R agonists with bronchodilator potential by BitterDB database analysis and cell stiffness screening. Methods: Bitter compounds in the BitterDB database were retrieved and analyzed for their working subtype of TAS2R and effective concentration. Compounds activating TAS2R5, 10, and 14 at < 100 μM effective concentration were identified and subsequently screened by cell stiffness assay using optical magnetic twisting cytometry (OMTC) to identify the most potent to relax ASMCs. Then the compound identified was further characterized for efficacy on various aspects related to relaxation of ASMCs, incl. but not limited to traction force by Fourier transform traction force microscopy (FTTFM), [Ca2+]i signaling by Fluo-4/AM intensity, cell migration by scratch wound healing, mRNA expression by qPCR, and protein expressing by ELISA. The compound identified was also compared to conventional β-agonist (isoproterenol and salbutamol) for efficacy in reducing cell stiffness of cultured ASMCs and airway resistance of ovalbumin-treated mice. Results: BitterDB analysis found 18 compounds activating TAS2R5, 10, and 14 at < 100 μM effective concentration. Cell stiffness screening of these compounds eventually identified flufenamic acid (FFA) as the most potent compound to rapidly reduce cell stiffness at 1 μM. The efficacy of FFA to relax ASMCs in vitro and abrogate airway resistance in vivo was equivalent to that of conventional β-agonists. The FFA-induced effect on ASMCs was mediated by TAS2R14 activation, endoplasmic reticulum Ca2+ release, and large-conductance Ca2+-activated K+ (BKCa) channel opening. FFA also attenuated lipopolysaccharide-induced inflammatory response in cultured ASMCs. Conclusions: FFA as a potent TAS2R14 agonist to relax ASMCs while suppressing cytokine release might be a favorite drug agent for further development of TAS2R-based novel dual functional medication for bronchodilation and anti-inflammation in asthma therapy.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | - Mingzhi Luo
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, and School of Medical and Health Engineering, Changzhou University, Changzhou, Jiangsu, China
| | - Linhong Deng
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, and School of Medical and Health Engineering, Changzhou University, Changzhou, Jiangsu, China
| |
Collapse
|
4
|
Sciancalepore M, Ragnini A, Zacchi P, Borelli V, D’Andrea P, Lorenzon P, Bernareggi A. A Pharmacological Investigation of the TMEM16A Currents in Murine Skeletal Myogenic Precursor Cells. Int J Mol Sci 2024; 25:2225. [PMID: 38396901 PMCID: PMC10889721 DOI: 10.3390/ijms25042225] [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: 01/17/2024] [Revised: 02/08/2024] [Accepted: 02/09/2024] [Indexed: 02/25/2024] Open
Abstract
TMEM16A is a Ca2+-activated Cl- channel expressed in various species and tissues. In mammalian skeletal muscle precursors, the activity of these channels is still poorly investigated. Here, we characterized TMEM16A channels and investigated if the pharmacological activation of Piezo1 channels could modulate the TMEM16A currents in mouse myogenic precursors. Whole-cell patch-clamp recordings combined with the pharmacological agents Ani9, T16inh-A01 and Yoda1 were used to characterize TMEM16A-mediated currents and the possible modulatory effect of Piezo1 activity on TMEM16A channels. Western blot analysis was also carried out to confirm the expression of TMEM16A and Piezo1 channel proteins. We found that TMEM16A channels were functionally expressed in fusion-competent mouse myogenic precursors. The pharmacological blockage of TMEM16A inhibited myocyte fusion into myotubes. Moreover, the specific Piezo1 agonist Yoda1 positively regulated TMEM16A currents. The findings demonstrate, for the first time, a sarcolemmal TMEM16A channel activity and its involvement at the early stage of mammalian skeletal muscle differentiation. In addition, the results suggest a possible role of mechanosensitive Piezo1 channels in the modulation of TMEM16A currents.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Annalisa Bernareggi
- Department of Life Sciences, University of Trieste, I-34127 Trieste, Italy; (M.S.); (A.R.); (P.Z.); (V.B.); (P.D.); (P.L.)
| |
Collapse
|
5
|
Arreola J, Pérez-Cornejo P, Segura-Covarrubias G, Corral-Fernández N, León-Aparicio D, Guzmán-Hernández ML. Function and Regulation of the Calcium-Activated Chloride Channel Anoctamin 1 (TMEM16A). Handb Exp Pharmacol 2024; 283:101-151. [PMID: 35768554 DOI: 10.1007/164_2022_592] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Various human tissues express the calcium-activated chloride channel Anoctamin 1 (ANO1), also known as TMEM16A. ANO1 allows the passive chloride flux that controls different physiological functions ranging from muscle contraction, fluid and hormone secretion, gastrointestinal motility, and electrical excitability. Overexpression of ANO1 is associated with pathological conditions such as hypertension and cancer. The molecular cloning of ANO1 has led to a surge in structural, functional, and physiological studies of the channel in several tissues. ANO1 is a homodimer channel harboring two pores - one in each monomer - that work independently. Each pore is activated by voltage-dependent binding of two intracellular calcium ions to a high-affinity-binding site. In addition, the binding of phosphatidylinositol 4,5-bisphosphate to sites scattered throughout the cytosolic side of the protein aids the calcium activation process. Furthermore, many pharmacological studies have established ANO1 as a target of promising compounds that could treat several illnesses. This chapter describes our current understanding of the physiological roles of ANO1 and its regulation under physiological conditions as well as new pharmacological compounds with potential therapeutic applications.
Collapse
Affiliation(s)
- Jorge Arreola
- Physics Institute, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico.
| | - Patricia Pérez-Cornejo
- Department of Physiology and Biophysics, School of Medicine of Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | - Guadalupe Segura-Covarrubias
- Physics Institute, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | - Nancy Corral-Fernández
- Department of Physiology and Biophysics, School of Medicine of Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | - Daniel León-Aparicio
- Physics Institute, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | | |
Collapse
|
6
|
Li S, Wang Z, Geng R, Zhang W, Wan H, Kang X, Guo S. TMEM16A ion channel: A novel target for cancer treatment. Life Sci 2023; 331:122034. [PMID: 37611692 DOI: 10.1016/j.lfs.2023.122034] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/13/2023] [Accepted: 08/18/2023] [Indexed: 08/25/2023]
Abstract
Cancer draws attention owing to the high morbidity and mortality. It is urgent to develop safe and effective cancer therapeutics. The calcium-activated chloride channel TMEM16A is widely distributed in various tissues and regulates physiological functions. TMEM16A is abnormally expressed in several cancers and associate with tumorigenesis, metastasis, and prognosis. Knockdown or inhibition of TMEM16A in cancer cells significantly inhibits cancer development. Therefore, TMEM16A is considered as a biomarker and therapeutic target for some cancers. This work reviews the cancers associated with TMEM16A. Then, the molecular mechanism of TMEM16A overexpression in cancer was analyzed, and the possible signal transduction mechanism of TMEM16A regulating cancer development was summarized. Finally, TMEM16A inhibitors with anticancer effect and their anticancer mechanism were concluded. We hope to provide new ideas for pharmacological studies on TMEM16A in cancer.
Collapse
Affiliation(s)
- Shuting Li
- School of Life Sciences, Hebei University, Baoding 071002, Hebei, China
| | - Zhichen Wang
- School of Life Sciences, Hebei University, Baoding 071002, Hebei, China
| | - Ruili Geng
- School of Life Sciences, Hebei University, Baoding 071002, Hebei, China
| | - Weiwei Zhang
- School of Basic Medical Sciences, Hebei University, Baoding 071002, Hebei, China
| | - Haifu Wan
- School of Life Sciences, Hebei University, Baoding 071002, Hebei, China; Institute of Life Sciences and Green Development, Hebei University, Baoding 071002, Hebei, China
| | - Xianjiang Kang
- School of Life Sciences, Hebei University, Baoding 071002, Hebei, China; Institute of Life Sciences and Green Development, Hebei University, Baoding 071002, Hebei, China.
| | - Shuai Guo
- School of Life Sciences, Hebei University, Baoding 071002, Hebei, China; Institute of Life Sciences and Green Development, Hebei University, Baoding 071002, Hebei, China.
| |
Collapse
|
7
|
He Z, Tu YC, Tsai CW, Mount J, Zhang J, Tsai MF, Yuan P. Structure and function of the human mitochondrial MRS2 channel. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.12.553106. [PMID: 37645897 PMCID: PMC10462007 DOI: 10.1101/2023.08.12.553106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The human Mitochondrial RNA Splicing 2 protein (MRS2) has been implicated in Mg2+ transport across mitochondrial inner membranes, thus playing an important role in Mg2+ homeostasis critical for mitochondrial integrity and function. However, the molecular mechanisms underlying its fundamental channel properties such as ion selectivity and regulation remain unclear. Here, we present structural and functional investigation of MRS2. Cryo-electron microscopy structures in various ionic conditions reveal a pentameric channel architecture and the molecular basis of ion permeation and potential regulation mechanisms. Electrophysiological analyses demonstrate that MRS2 is a Ca2+-regulated, non-selective channel permeable to Mg2+, Ca2+, Na+ and K+, which contrasts with its prokaryotic ortholog, CorA, operating as a Mg2+-gated Mg2+ channel. Moreover, a conserved arginine ring within the pore of MRS2 functions to restrict cation movements, likely preventing the channel from collapsing the proton motive force that drives mitochondrial ATP synthesis. Together, our results provide a molecular framework for further understanding MRS2 in mitochondrial function and disease.
Collapse
Affiliation(s)
- Zhihui He
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- These authors contributed equally to this work
| | - Yung-Chi Tu
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- These authors contributed equally to this work
| | - Chen-Wei Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Jonathan Mount
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Ming-Feng Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| |
Collapse
|
8
|
Arreola J, López-Romero AE, Pérez-Cornejo P, Rodríguez-Menchaca AA. Phosphatidylinositol 4,5-Bisphosphate and Cholesterol Regulators of the Calcium-Activated Chloride Channels TMEM16A and TMEM16B. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:279-304. [PMID: 36988885 DOI: 10.1007/978-3-031-21547-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Chloride fluxes through homo-dimeric calcium-activated channels TMEM16A and TMEM16B are critical to blood pressure, gastrointestinal motility, hormone, fluid and electrolyte secretion, pain sensation, sensory transduction, and neuronal and muscle excitability. Their gating depends on the voltage-dependent binding of two intracellular calcium ions to a high-affinity site formed by acidic residues from α-helices 6-8 in each monomer. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), a low-abundant lipid of the inner leaflet, supports TMEM16A function; it allows TMEM16A to evade the down-regulation induced by calcium, poly-L-lysine, or PI(4,5)P2 5-phosphatase. In stark contrast, adding or removing PI(4,5)P2 diminishes or increases TMEM16B function, respectively. PI(4,5)P2-binding sites on TMEM16A, and presumably on TMEM16B, are on the cytosolic side of α-helices 3-5, opposite the calcium-binding sites. This modular structure suggested that PI(4,5)P2 and calcium cooperate to maintain the conductive state in TMEM16A. Cholesterol, the second-largest constituent of the plasma membrane, also regulates TMEM16A though the mechanism, functional outcomes, binding site(s), and effects on TMEM16A and TMEM16B remain unknown.
Collapse
Affiliation(s)
- Jorge Arreola
- Physics Institute, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico.
| | | | - Patricia Pérez-Cornejo
- Department of Physiology and Biophysics, School of Medicine, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | - Aldo A Rodríguez-Menchaca
- Department of Physiology and Biophysics, School of Medicine, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| |
Collapse
|
9
|
Leucine 434 is essential for docosahexaenoic acid-induced augmentation of L-glutamate transporter current. J Biol Chem 2022; 299:102793. [PMID: 36509140 PMCID: PMC9823230 DOI: 10.1016/j.jbc.2022.102793] [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: 04/13/2022] [Revised: 11/30/2022] [Accepted: 12/04/2022] [Indexed: 12/14/2022] Open
Abstract
Astrocytic excitatory amino acid transporter 2 (EAAT2) plays a major role in removing the excitatory neurotransmitter L-glutamate (L-Glu) from synaptic clefts in the forebrain to prevent excitotoxicity. Polyunsaturated fatty acids such as docosahexaenoic acid (DHA, 22:6 n-3) enhance synaptic transmission, and their target molecules include EAATs. Here, we aimed to investigate the effect of DHA on EAAT2 and identify the key amino acid for DHA/EAAT2 interaction by electrophysiological recording of L-Glu-induced current in Xenopus oocytes transfected with EAATs, their chimeras, and single mutants. DHA transiently increased the amplitude of EAAT2 but tended to decrease that of excitatory amino acid transporter subtype 1 (EAAT1), another astrocytic EAAT. Single mutation of leucine (Leu) 434 to alanine (Ala) completely suppressed the augmentation by DHA, while mutation of EAAT1 Ala 435 (corresponding to EAAT2 Leu434) to Leu changed the effect from suppression to augmentation. Other polyunsaturated fatty acids (docosapentaenoic acid, eicosapentaenoic acid, arachidonic acid, and α-linolenic acid) similarly augmented the EAAT2 current and suppressed the EAAT1 current. Finally, our docking analysis suggested the most stable docking site is the lipid crevice of EAAT2, in close proximity to the L-Glu and sodium binding sites, suggesting that the DHA/Leu434 interaction might affect the elevator-like slide and/or the shapes of the other binding sites. Collectively, our results highlight a key molecular detail in the DHA-induced regulation of synaptic transmission involving EAATs.
Collapse
|
10
|
Jimenez C, Hawn MB, Akin E, Leblanc N. Translational potential of targeting Anoctamin-1-Encoded Calcium-Activated chloride channels in hypertension. Biochem Pharmacol 2022; 206:115320. [PMID: 36279919 DOI: 10.1016/j.bcp.2022.115320] [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: 08/24/2022] [Revised: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 12/14/2022]
Abstract
Calcium-activated chloride channels (CaCC) provide a depolarizing stimulus to a variety of tissues through chloride efflux in response to a rise in internal Ca2+ and voltage. One of these channels, Anoctamin-1 (ANO1 or TMEM16A) is now recognized to play a central role in promoting smooth muscle tone in various types of blood vessels. Its role in hypertension, and thus the therapeutic promise of targeting ANO1, is less straightforward. This review gives an overview of our current knowledge about the potential role ANO1 may play in hypertension within the systemic, portal, and pulmonary vascular systems and the importance of this information when pursuing potential treatment strategies. While the role of ANO1 is well-established in several forms of pulmonary hypertension, its contributions to both the generation of vascular tone and its role in hypertension within the systemic and portal systems are much less clear. This, combined with ANO1's various roles throughout a multitude of tissues throughout the body, command caution when targeting ANO1 as a therapeutic target and may require tissue-selective strategies.
Collapse
Affiliation(s)
- Connor Jimenez
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, 1664 North Virginia Street, Reno, Nevada 89557, USA
| | - Matthew B Hawn
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, 1664 North Virginia Street, Reno, Nevada 89557, USA
| | - Elizabeth Akin
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, 1664 North Virginia Street, Reno, Nevada 89557, USA
| | - Normand Leblanc
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, 1664 North Virginia Street, Reno, Nevada 89557, USA.
| |
Collapse
|
11
|
Ivorra I, Alberola-Die A, Cobo R, González-Ros JM, Morales A. Xenopus Oocytes as a Powerful Cellular Model to Study Foreign Fully-Processed Membrane Proteins. MEMBRANES 2022; 12:986. [PMID: 36295745 PMCID: PMC9610954 DOI: 10.3390/membranes12100986] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 06/16/2023]
Abstract
The use of Xenopus oocytes in electrophysiological and biophysical research constitutes a long and successful story, providing major advances to the knowledge of the function and modulation of membrane proteins, mostly receptors, ion channels, and transporters. Earlier reports showed that these cells are capable of correctly expressing heterologous proteins after injecting the corresponding mRNA or cDNA. More recently, the Xenopus oocyte has become an outstanding host-cell model to carry out detailed studies on the function of fully-processed foreign membrane proteins after their microtransplantation to the oocyte. This review focused on the latter overall process of transplanting foreign membrane proteins to the oocyte after injecting plasma membranes or purified and reconstituted proteins. This experimental approach allows for the study of both the function of mature proteins, with their native stoichiometry and post-translational modifications, and their putative modulation by surrounding lipids, mostly when the protein is purified and reconstituted in lipid matrices of defined composition. Remarkably, this methodology enables functional microtransplantation to the oocyte of membrane receptors, ion channels, and transporters from different sources including human post-mortem tissue banks. Despite the large progress achieved over the last decades on the structure, function, and modulation of neuroreceptors and ion channels in healthy and pathological tissues, many unanswered questions remain and, most likely, Xenopus oocytes will continue to help provide valuable responses.
Collapse
Affiliation(s)
- Isabel Ivorra
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - Armando Alberola-Die
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - Raúl Cobo
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - José Manuel González-Ros
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, E-03202 Elche, Spain
| | - Andrés Morales
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| |
Collapse
|
12
|
Hone AJ, McIntosh JM. Alkaloid ligands enable function of homomeric human α10 nicotinic acetylcholine receptors. Front Pharmacol 2022; 13:981760. [PMID: 36188578 PMCID: PMC9523446 DOI: 10.3389/fphar.2022.981760] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/23/2022] [Indexed: 01/29/2023] Open
Abstract
In the nervous system, nicotinic acetylcholine receptors (nAChRs) rapidly transduce a chemical signal into one that is electrical via ligand-gated ion flux through the central channel of the receptor. However, some nAChR subunits are expressed by non-excitable cells where signal transduction apparently occurs through non-ionic mechanisms. One such nAChR subunit, α10, is present in a discreet subset of immune cells and has been implicated in pathologies including cancer, neuropathic pain, and chronic inflammation. Longstanding convention holds that human α10 subunits require co-assembly with α9 subunits for function. Here we assessed whether cholinergic ligands can enable or uncover ionic functions from homomeric α10 nAChRs. Xenopus laevis oocytes expressing human α10 subunits were exposed to a panel of ligands and examined for receptor activation using voltage-clamp electrophysiology. Functional expression of human α10 nAChRs was achieved by exposing the oocytes to the alkaloids strychnine, brucine, or methyllycaconitine. Furthermore, acute exposure to the alkaloid ligands significantly enhanced ionic responses. Acetylcholine-gated currents mediated by α10 nAChRs were potently inhibited by the snake toxins α-bungarotoxin and α-cobratoxin but not by α-conotoxins that target α9 and α9α10 nAChRs. Our findings indicate that human α10 homomers are expressed in oocytes and exposure to certain ligands can enable ionic functions. To our knowledge, this is the first demonstration that human α10 subunits can assemble as functional homomeric nAChRs. These findings have potential implications for receptor regulatory-mechanisms and will enable structural, functional, and further pharmacological characterization of human α10 nAChRs.
Collapse
Affiliation(s)
- Arik J. Hone
- School of Biological Sciences, University of Utah, Salt Lake City, UT, United States
- MIRECC, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, UT, United States
| | - J. Michael McIntosh
- School of Biological Sciences, University of Utah, Salt Lake City, UT, United States
- Department of Psychiatry, University of Utah, Salt Lake City, UT, United States
- George E. Whalen Veterans Affairs Medical Center, Salt Lake City, UT, United States
| |
Collapse
|
13
|
Al-Hosni R, Ilkan Z, Agostinelli E, Tammaro P. The pharmacology of the TMEM16A channel: therapeutic opportunities. Trends Pharmacol Sci 2022; 43:712-725. [PMID: 35811176 DOI: 10.1016/j.tips.2022.06.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 06/06/2022] [Accepted: 06/08/2022] [Indexed: 12/15/2022]
Abstract
The TMEM16A Ca2+-gated Cl- channel is involved in a variety of vital physiological functions and may be targeted pharmacologically for therapeutic benefit in diseases such as hypertension, stroke, and cystic fibrosis (CF). The determination of the TMEM16A structure and high-throughput screening efforts, alongside ex vivo and in vivo animal studies and clinical investigations, are hastening our understanding of the physiology and pharmacology of this channel. Here, we offer a critical analysis of recent developments in TMEM16A pharmacology and reflect on the therapeutic opportunities provided by this target.
Collapse
Affiliation(s)
- Rumaitha Al-Hosni
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Zeki Ilkan
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Emilio Agostinelli
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Paolo Tammaro
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| |
Collapse
|
14
|
Pant S, Wu Q, Ryan R, Tajkhorshid E. Microscopic Characterization of the Chloride Permeation Pathway in the Human Excitatory Amino Acid Transporter 1 (EAAT1). ACS Chem Neurosci 2022; 13:776-785. [PMID: 35192345 PMCID: PMC9725111 DOI: 10.1021/acschemneuro.1c00769] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) are glutamate transporters that belong to the solute carrier 1A (SLC1A) family. They couple glutamate transport to the cotransport of three sodium (Na+) ions and one proton (H+) and the counter-transport of one potassium (K+) ion. In addition to this coupled transport, binding of cotransported species to EAATs activates a thermodynamically uncoupled chloride (Cl-) conductance. Structures of SLC1A family members have revealed that these transporters use a twisting elevator mechanism of transport, where a mobile transport domain carries substrate and coupled ions across the membrane, while a static scaffold domain anchors the transporter in the membrane. We recently demonstrated that the uncoupled Cl- conductance is activated by the formation of an aqueous pore at the domain interface during the transport cycle in archaeal GltPh. However, a pathway for the uncoupled Cl- conductance has not been reported for the EAATs, and it is unclear if such a pathway is conserved. Here, we employ all-atom molecular dynamics (MD) simulations combined with enhanced sampling, free-energy calculations, and experimental mutagenesis to approximate large-scale conformational changes during the transport process and identified a Cl--conducting conformation in human EAAT1 (hEAAT1). Sampling the large-scale structural transitions in hEAAT1 allowed us to capture an intermediate conformation formed during the transport cycle with a continuous aqueous pore at the domain interface. The free-energy calculations performed for the conduction of Cl- and Na+ ions through the captured conformation highlight the presence of two hydrophobic gates that control low-barrier movement of Cl- through the aqueous pathway. Overall, our findings provide insights into the mechanism by which a human neurotransmitter transporter supports functional duality of active transport and passive Cl- permeation and confirm the commonality of this mechanism in different members of the SLC1A family.
Collapse
Affiliation(s)
- Shashank Pant
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Qianyi Wu
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Renae Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| |
Collapse
|
15
|
Wu Q, Akhter A, Pant S, Cho E, Zhu JX, Garner AR, Ohyama T, Tajkhorshid E, van Meyel DJ, Ryan RM. Ataxia-linked SLC1A3 mutations alter EAAT1 chloride channel activity and glial regulation of CNS function. J Clin Invest 2022; 132:154891. [PMID: 35167492 PMCID: PMC8970671 DOI: 10.1172/jci154891] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/08/2022] [Indexed: 11/17/2022] Open
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system (CNS). Excitatory Amino Acid Transporters (EAATs) regulate extracellular glutamate by transporting it into cells, mostly glia, to terminate neurotransmission and to avoid neurotoxicity. EAATs are also chloride (Cl-) channels, but the physiological role of Cl- conductance through EAATs is poorly understood. Mutations of human EAAT1 (hEAAT1) have been identified in patients with episodic ataxia type 6 (EA6). One mutation showed increased Cl- channel activity and decreased glutamate transport, but the relative contributions of each function of hEAAT1 to mechanisms underlying the pathology of EA6 remain unclear. Here we investigated the effects of five additional EA6-related mutations on hEAAT1 function in Xenopus laevis oocytes, and on CNS function in a Drosophila melanogaster model of locomotor behavior. Our results indicate that mutations resulting in decreased hEAAT1 Cl- channel activity but with functional glutamate transport can also contribute to the pathology of EA6, highlighting the importance of Cl- homeostasis in glial cells for proper CNS function. We also identified a novel mechanism involving an ectopic sodium (Na+) leak conductance in glial cells. Together, these results strongly support the idea that EA6 is primarily an ion channelopathy of CNS glia.
Collapse
Affiliation(s)
- Qianyi Wu
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Azman Akhter
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Shashank Pant
- Theoretical and Computational Biophysics Group, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Eunjoo Cho
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Jin Xin Zhu
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | | | - Tomoko Ohyama
- Department of Biology, McGill University, Montreal, Canada
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Donald J van Meyel
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Renae M Ryan
- School of Medical Sciences, University of Sydney, Sydney, Australia
| |
Collapse
|
16
|
Hernandez A, Alaniz-Palacios A, Contreras-Vite JA, Martínez-Torres A. Positive modulation of the TMEM16B mediated currents by TRPV4 antagonist. Biochem Biophys Rep 2021; 28:101180. [PMID: 34917777 PMCID: PMC8646129 DOI: 10.1016/j.bbrep.2021.101180] [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: 10/27/2021] [Revised: 11/23/2021] [Accepted: 11/29/2021] [Indexed: 11/30/2022] Open
Abstract
Calcium-activated chloride channels (CaCCs) play important roles in many physiological processes and their malfunction is implicated in diverse pathologies such as cancer, asthma, and hypertension. TMEM16A and TMEM16B proteins are the structural components of the CaCCs. Recent studies in cell cultures and animal models have demonstrated that pharmacological inhibition of CaCCs could be helpful in the treatment of some diseases, however, there are few specific modulators of these channels. CaCCs and Transient Receptor Potential Vanilloid-4 (TRPV4) channels are co-expressed in some tissues where they functionally interact. TRPV4 is activated by different stimuli and forms a calcium permeable channel that is activated by GSK1016790A and antagonized by GSK2193874. Here we report that GSK2193874 enhances the chloride currents mediated by TMEM16B expressed in HEK cells at nanomolar concentrations and that GSK1016790A enhances native CaCCs of Xenopus oocytes. Thus, these compounds may be used as a tool for the study of CaCCs, TRPV4 and their interactions.
Collapse
Affiliation(s)
- Adan Hernandez
- Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, 76230 Santiago de Querétaro, Querétaro, Mexico
| | - Alfredo Alaniz-Palacios
- Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, 76230 Santiago de Querétaro, Querétaro, Mexico
| | - Juan A Contreras-Vite
- Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, 76230 Santiago de Querétaro, Querétaro, Mexico
| | - Ataúlfo Martínez-Torres
- Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, 76230 Santiago de Querétaro, Querétaro, Mexico
| |
Collapse
|
17
|
Angelini M, Pezhouman A, Savalli N, Chang MG, Steccanella F, Scranton K, Calmettes G, Ottolia M, Pantazis A, Karagueuzian HS, Weiss JN, Olcese R. Suppression of ventricular arrhythmias by targeting late L-type Ca2+ current. J Gen Physiol 2021; 153:212725. [PMID: 34698805 PMCID: PMC8552156 DOI: 10.1085/jgp.202012584] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 07/15/2021] [Accepted: 09/02/2021] [Indexed: 12/15/2022] Open
Abstract
Ventricular arrhythmias, a leading cause of sudden cardiac death, can be triggered by cardiomyocyte early afterdepolarizations (EADs). EADs can result from an abnormal late activation of L-type Ca2+ channels (LTCCs). Current LTCC blockers (class IV antiarrhythmics), while effective at suppressing EADs, block both early and late components of ICa,L, compromising inotropy. However, computational studies have recently demonstrated that selective reduction of late ICa,L (Ca2+ influx during late phases of the action potential) is sufficient to potently suppress EADs, suggesting that effective antiarrhythmic action can be achieved without blocking the early peak ICa,L, which is essential for proper excitation–contraction coupling. We tested this new strategy using a purine analogue, roscovitine, which reduces late ICa,L with minimal effect on peak current. Scaling our investigation from a human CaV1.2 channel clone to rabbit ventricular myocytes and rat and rabbit perfused hearts, we demonstrate that (1) roscovitine selectively reduces ICa,L noninactivating component in a human CaV1.2 channel clone and in ventricular myocytes native current, (2) the pharmacological reduction of late ICa,L suppresses EADs and EATs (early after Ca2+ transients) induced by oxidative stress and hypokalemia in isolated myocytes, largely preserving cell shortening and normal Ca2+ transient, and (3) late ICa,L reduction prevents/suppresses ventricular tachycardia/fibrillation in ex vivo rabbit and rat hearts subjected to hypokalemia and/or oxidative stress. These results support the value of an antiarrhythmic strategy based on the selective reduction of late ICa,L to suppress EAD-mediated arrhythmias. Antiarrhythmic therapies based on this idea would modify the gating properties of CaV1.2 channels rather than blocking their pore, largely preserving contractility.
Collapse
Affiliation(s)
- Marina Angelini
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Arash Pezhouman
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Nicoletta Savalli
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marvin G Chang
- Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA
| | - Federica Steccanella
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Kyle Scranton
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Guillaume Calmettes
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Michela Ottolia
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,University of California, Los Angeles Cardiovascular Theme, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Antonios Pantazis
- Division of Neurobiology, Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.,Wallenberg Center for Molecular Medicine, Linköping University, Linköping, Sweden
| | - Hrayr S Karagueuzian
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Riccardo Olcese
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,University of California, Los Angeles Cardiovascular Theme, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| |
Collapse
|
18
|
Hawn MB, Akin E, Hartzell H, Greenwood IA, Leblanc N. Molecular mechanisms of activation and regulation of ANO1-Encoded Ca 2+-Activated Cl - channels. Channels (Austin) 2021; 15:569-603. [PMID: 34488544 PMCID: PMC8480199 DOI: 10.1080/19336950.2021.1975411] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 08/29/2021] [Indexed: 01/13/2023] Open
Abstract
Ca2+-activated Cl- channels (CaCCs) perform a multitude of functions including the control of cell excitability, regulation of cell volume and ionic homeostasis, exocrine and endocrine secretion, fertilization, amplification of olfactory sensory function, and control of smooth muscle cell contractility. CaCCs are the translated products of two members (ANO1 and ANO2, also known as TMEM16A and TMEM16B) of the Anoctamin family of genes comprising ten paralogs. This review focuses on recent progress in understanding the molecular mechanisms involved in the regulation of ANO1 by cytoplasmic Ca2+, post-translational modifications, and how the channel protein interacts with membrane lipids and protein partners. After first reviewing the basic properties of native CaCCs, we then present a brief historical perspective highlighting controversies about their molecular identity in native cells. This is followed by a summary of the fundamental biophysical and structural properties of ANO1. We specifically address whether the channel is directly activated by internal Ca2+ or indirectly through the intervention of the Ca2+-binding protein Calmodulin (CaM), and the structural domains responsible for Ca2+- and voltage-dependent gating. We then review the regulation of ANO1 by internal ATP, Calmodulin-dependent protein kinase II-(CaMKII)-mediated phosphorylation and phosphatase activity, membrane lipids such as the phospholipid phosphatidyl-(4,5)-bisphosphate (PIP2), free fatty acids and cholesterol, and the cytoskeleton. The article ends with a survey of physical and functional interactions of ANO1 with other membrane proteins such as CLCA1/2, inositol trisphosphate and ryanodine receptors in the endoplasmic reticulum, several members of the TRP channel family, and the ancillary Κ+ channel β subunits KCNE1/5.
Collapse
Affiliation(s)
- M. B. Hawn
- Department of Pharmacology and Center of Biomedical Research Excellence for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, Reno, United States
| | - E. Akin
- Department of Pharmacology and Center of Biomedical Research Excellence for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, Reno, United States
| | - H.C. Hartzell
- Department of Cell Biology, Emory University School of Medicine, USA
| | - I. A. Greenwood
- Department of Vascular Pharmacology, St. George’s University of London, UK
| | - N. Leblanc
- Department of Pharmacology and Center of Biomedical Research Excellence for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, Reno, United States
| |
Collapse
|
19
|
Le SC, Liang P, Lowry AJ, Yang H. Gating and Regulatory Mechanisms of TMEM16 Ion Channels and Scramblases. Front Physiol 2021; 12:787773. [PMID: 34867487 PMCID: PMC8640346 DOI: 10.3389/fphys.2021.787773] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 10/29/2021] [Indexed: 12/30/2022] Open
Abstract
The transmembrane protein 16 (TMEM16) family consists of Ca2+-activated ion channels and Ca2+-activated phospholipid scramblases (CaPLSases) that passively flip-flop phospholipids between the two leaflets of the membrane bilayer. Owing to their diverse functions, TMEM16 proteins have been implicated in various human diseases, including asthma, cancer, bleeding disorders, muscular dystrophy, arthritis, epilepsy, dystonia, ataxia, and viral infection. To understand TMEM16 proteins in health and disease, it is critical to decipher their molecular mechanisms of activation gating and regulation. Structural, biophysical, and computational characterizations over the past decade have greatly advanced the molecular understanding of TMEM16 proteins. In this review, we summarize major structural features of the TMEM16 proteins with a focus on regulatory mechanisms and gating.
Collapse
Affiliation(s)
- Son C. Le
- Department of Biochemistry, Duke University Medical Center, Durham, NC, United States
| | - Pengfei Liang
- Department of Biochemistry, Duke University Medical Center, Durham, NC, United States
| | - Augustus J. Lowry
- Department of Biochemistry, Duke University Medical Center, Durham, NC, United States
| | - Huanghe Yang
- Department of Biochemistry, Duke University Medical Center, Durham, NC, United States
- Department of Neurobiology, Duke University Medical Center, Durham, NC, United States
| |
Collapse
|
20
|
Ji W, Shi D, Shi S, Yang X, Chen Y, An H, Pang C. TMEM16A protein: calcium binding site and its activation mechanism. Protein Pept Lett 2021; 28:1338-1348. [PMID: 34749600 DOI: 10.2174/0929866528666211105112131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/08/2021] [Accepted: 09/18/2021] [Indexed: 11/22/2022]
Abstract
TMEM16A mediates calcium-activated transmembrane flow of chloride ion and a variety of physiological functions. The binding of cytoplasmic calcium ions of TMEM16A and the consequent conformational changes of it are the key issues to explore the relationship between its structure and function. In recent years, researchers have explored this issue through electrophysiological experiment, structure resolving, molecular dynamic simulation and other methods. The structures of TMEM16 family members resolved by cryo-Electron microscopy (cryo-EM) and X-ray crystallization provide the primarily basis for the investigation of the molecular mechanism of TMEM16A. However, the binding and activation mechanism of calcium ions in TMEM16A are still unclear and controversial. This review discusses four Ca2+ sensing sites of TMEM16A and analyze activation properties of TMEM16A by them, which will help to understand the structure-function relationship of TMEM16A and throw light on the molecular design targeting TMEM16A channel.
Collapse
Affiliation(s)
- Wanying Ji
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| | - Donghong Shi
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| | - Sai Shi
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| | - Xiao Yang
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| | - Yafei Chen
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| | - Hailong An
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| | - Chunli Pang
- Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401. China
| |
Collapse
|
21
|
Savalli N, Angelini M, Steccanella F, Wier J, Wu F, Quinonez M, DiFranco M, Neely A, Cannon SC, Olcese R. The distinct role of the four voltage sensors of the skeletal CaV1.1 channel in voltage-dependent activation. J Gen Physiol 2021; 153:212652. [PMID: 34546289 PMCID: PMC8460119 DOI: 10.1085/jgp.202112915] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 08/22/2021] [Indexed: 11/30/2022] Open
Abstract
Initiation of skeletal muscle contraction is triggered by rapid activation of RYR1 channels in response to sarcolemmal depolarization. RYR1 is intracellular and has no voltage-sensing structures, but it is coupled with the voltage-sensing apparatus of CaV1.1 channels to inherit voltage sensitivity. Using an opto-electrophysiological approach, we resolved the excitation-driven molecular events controlling both CaV1.1 and RYR1 activations, reported as fluorescence changes. We discovered that each of the four human CaV1.1 voltage-sensing domains (VSDs) exhibits unique biophysical properties: VSD-I time-dependent properties were similar to ionic current activation kinetics, suggesting a critical role of this voltage sensor in CaV1.1 activation; VSD-II, VSD-III, and VSD-IV displayed faster activation, compatible with kinetics of sarcoplasmic reticulum Ca2+ release. The prominent role of VSD-I in governing CaV1.1 activation was also confirmed using a naturally occurring, charge-neutralizing mutation in VSD-I (R174W). This mutation abolished CaV1.1 current at physiological membrane potentials by impairing VSD-I activation without affecting the other VSDs. Using a structurally relevant allosteric model of CaV activation, which accounted for both time- and voltage-dependent properties of CaV1.1, to predict VSD-pore coupling energies, we found that VSD-I contributed the most energy (~75 meV or ∼3 kT) toward the stabilization of the open states of the channel, with smaller (VSD-IV) or negligible (VSDs II and III) energetic contribution from the other voltage sensors (<25 meV or ∼1 kT). This study settles the longstanding question of how CaV1.1, a slowly activating channel, can trigger RYR1 rapid activation, and reveals a new mechanism for voltage-dependent activation in ion channels, whereby pore opening of human CaV1.1 channels is primarily driven by the activation of one voltage sensor, a mechanism distinct from that of all other voltage-gated channels.
Collapse
Affiliation(s)
- Nicoletta Savalli
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marina Angelini
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Federica Steccanella
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Julian Wier
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Fenfen Wu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marbella Quinonez
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marino DiFranco
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Alan Neely
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Stephen C Cannon
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| |
Collapse
|
22
|
Roy Choudhury A, Großhans J, Kong D. Ion Channels in Epithelial Dynamics and Morphogenesis. Cells 2021; 10:cells10092280. [PMID: 34571929 PMCID: PMC8465836 DOI: 10.3390/cells10092280] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 08/22/2021] [Accepted: 08/30/2021] [Indexed: 01/21/2023] Open
Abstract
Mechanosensitive ion channels mediate the neuronal sensation of mechanical signals such as sound, touch, and pain. Recent studies point to a function of these channel proteins in cell types and tissues in addition to the nervous system, such as epithelia, where they have been little studied, and their role has remained elusive. Dynamic epithelia are intrinsically exposed to mechanical forces. A response to pull and push is assumed to constitute an essential part of morphogenetic movements of epithelial tissues, for example. Mechano-gated channels may participate in sensing and responding to such forces. In this review, focusing on Drosophila, we highlight recent results that will guide further investigations concerned with the mechanistic role of these ion channels in epithelial cells.
Collapse
|
23
|
Emerging Modulators of TMEM16A and Their Therapeutic Potential. J Membr Biol 2021; 254:353-365. [PMID: 34263350 DOI: 10.1007/s00232-021-00188-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 05/21/2021] [Indexed: 02/04/2023]
Abstract
Calcium-activated chloride channels (CaCCs) are widespread chloride channels which rely on calcium activation to perform their functions. In 2008, TMEM16A (also known as anoctamin1, ANO1) was identified as the molecular basis of the CaCCs, which provided the possibility to study the physiological function of CaCCs. TMEM16A is widely expressed in various cells and controls basic physiological functions, including neuronal and cardiac excitability, nerve transduction, smooth muscle contraction, epithelial Cl- secretion and fertilization. However, the abnormal function of TMEM16A may cause a variety of diseases, including asthma, gastrointestinal motility disorder and various cancers. Therefore, TMEM16A is a putative drug target for many diseases, and it is important to determine specific and efficient modulators of TMEM16A channel. In recent years, we and others have screened several natural modulators of TMEM16A against cancers and gastrointestinal motility dysfunction. This article reviews the screening methods, efficacy of TMEM16A modulators and pharmacological effects of TMEM16A modulators on different diseases. GRAPHIC ABSTACT.
Collapse
|
24
|
Marcovich I, Moglie MJ, Carpaneto Freixas AE, Trigila AP, Franchini LF, Plazas PV, Lipovsek M, Elgoyhen AB. Distinct Evolutionary Trajectories of Neuronal and Hair Cell Nicotinic Acetylcholine Receptors. Mol Biol Evol 2021; 37:1070-1089. [PMID: 31821508 PMCID: PMC7086180 DOI: 10.1093/molbev/msz290] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The expansion and pruning of ion channel families has played a crucial role in the evolution of nervous systems. Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels with distinct roles in synaptic transmission at the neuromuscular junction, the central and peripheral nervous system, and the inner ear. Remarkably, the complement of nAChR subunits has been highly conserved along vertebrate phylogeny. To ask whether the different subtypes of receptors underwent different evolutionary trajectories, we performed a comprehensive analysis of vertebrate nAChRs coding sequences, mouse single-cell expression patterns, and comparative functional properties of receptors from three representative tetrapod species. We found significant differences between hair cell and neuronal receptors that were most likely shaped by the differences in coexpression patterns and coassembly rules of component subunits. Thus, neuronal nAChRs showed high degree of coding sequence conservation, coupled to greater coexpression variance and conservation of functional properties across tetrapod clades. In contrast, hair cell α9α10 nAChRs exhibited greater sequence divergence, narrow coexpression pattern, and great variability of functional properties across species. These results point to differential substrates for random change within the family of gene paralogs that relate to the segregated roles of nAChRs in synaptic transmission.
Collapse
Affiliation(s)
- Irina Marcovich
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marcelo J Moglie
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Agustín E Carpaneto Freixas
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Anabella P Trigila
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Lucia F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Paola V Plazas
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Marcela Lipovsek
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Centre for Developmental Neurobiology, King's College London, Institute of Psychiatry, Psychology and Neuroscience, Guy's Campus, London, United Kingdom
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| |
Collapse
|
25
|
The Groovy TMEM16 Family: Molecular Mechanisms of Lipid Scrambling and Ion Conduction. J Mol Biol 2021; 433:166941. [PMID: 33741412 DOI: 10.1016/j.jmb.2021.166941] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/09/2021] [Accepted: 03/09/2021] [Indexed: 12/28/2022]
Abstract
The TMEM16 family of membrane proteins displays a remarkable functional dichotomy - while some family members function as Ca2+-activated anion channels, the majority of characterized TMEM16 homologs are Ca2+-activated lipid scramblases, which catalyze the exchange of phospholipids between the two membrane leaflets. Furthermore, some TMEM16 scramblases can also function as channels. Due to their involvement in important physiological processes, the family has been actively studied ever since their molecular identity was unraveled. In this review, we will summarize the recent advances in the field and how they influenced our view of TMEM16 family function and evolution. Structural, functional and computational studies reveal how relatively small rearrangements in the permeation pathway are responsible for the observed functional duality: while TMEM16 scramblases can adopt both ion- and lipid conductive conformations, TMEM16 channels can only populate the former. Recent data further provides the molecular details of a stepwise activation mechanism, which is initiated by Ca2+ binding and modulated by various cellular factors, including lipids. TMEM16 function and the surrounding membrane properties are inextricably intertwined, with the protein inducing bilayer deformations associated with scrambling, while the surrounding lipids modulate TMEM16 conformation and activity.
Collapse
|
26
|
Chen I, Pant S, Wu Q, Cater R, Sobti M, Vandenberg R, Stewart AG, Tajkhorshid E, Font J, Ryan R. Glutamate transporters have a chloride channel with two hydrophobic gates. Nature 2021; 591:327-331. [PMID: 33597752 PMCID: PMC7954978 DOI: 10.1038/s41586-021-03240-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 01/13/2021] [Indexed: 01/31/2023]
Abstract
Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and its precise control is vital to maintain normal brain function and to prevent excitotoxicity1. The removal of extracellular glutamate is achieved by plasma-membrane-bound transporters, which couple glutamate transport to sodium, potassium and pH gradients using an elevator mechanism2-5. Glutamate transporters also conduct chloride ions by means of a channel-like process that is thermodynamically uncoupled from transport6-8. However, the molecular mechanisms that enable these dual-function transporters to carry out two seemingly contradictory roles are unknown. Here we report the cryo-electron microscopy structure of a glutamate transporter homologue in an open-channel state, which reveals an aqueous cavity that is formed during the glutamate transport cycle. The functional properties of this cavity, combined with molecular dynamics simulations, reveal it to be an aqueous-accessible chloride permeation pathway that is gated by two hydrophobic regions and is conserved across mammalian and archaeal glutamate transporters. Our findings provide insight into the mechanism by which glutamate transporters support their dual function, and add information that will assist in mapping the complete transport cycle shared by the solute carrier 1A transporter family.
Collapse
Affiliation(s)
- Ichia Chen
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Shashank Pant
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Qianyi Wu
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Rosemary Cater
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Meghna Sobti
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia.,St Vincent’s Clinical School, Faculty of Medicine, UNSW Sydney, Kensington, NSW 2052, Australia
| | - Robert Vandenberg
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Alastair G. Stewart
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia.,St Vincent’s Clinical School, Faculty of Medicine, UNSW Sydney, Kensington, NSW 2052, Australia
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA, Corresponding authors: Emad Tajkhorshid (), Josep Font (), Renae Ryan ()
| | - Josep Font
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia, Corresponding authors: Emad Tajkhorshid (), Josep Font (), Renae Ryan ()
| | - Renae Ryan
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia, Corresponding authors: Emad Tajkhorshid (), Josep Font (), Renae Ryan ()
| |
Collapse
|
27
|
Saha T, Aoun J, Hayashi M, Ali SI, Sarkar P, Bag PK, Leblanc N, Ameen N, Woodward OM, Hoque KM. Intestinal TMEM16A control luminal chloride secretion in a NHERF1 dependent manner. Biochem Biophys Rep 2021; 25:100912. [PMID: 33537462 PMCID: PMC7838733 DOI: 10.1016/j.bbrep.2021.100912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 12/18/2020] [Accepted: 01/06/2021] [Indexed: 12/11/2022] Open
Abstract
TMEM16A (Transmembrane protein 16A or Anoctamin1) is a calcium-activated chloride channel. (CaCC),that exerts critical roles in epithelial secretion. However, its localization, function, and regulation in intestinal chloride (Cl−) secretion remain obscure. Here, we show that TMEM16A protein abundance correlates with Cl− secretion in different regions of native intestine activated by the Ca2+-elevating muscarinic agonist carbachol (CCH). Basal, as well as both cAMP- and CCH-stimulated Isc, was largely reduced in Ano1 ± mouse intestine. We found CCH was not able to increase Isc in the presence of apical to serosal Cl− gradient, strongly supporting TMEM16A as primarily a luminal Cl− channel. Immunostaining demonstrated apical localization of TMEM16A where it colocalized with NHERF1 in mouse colonic tissue. Cellular depletion of NHERF1 in human colonic T84 cells caused a significant reduction of both cAMP- and CCH-stimulated Isc. Immunoprecipitation experiments revealed that NHERF1 forms a complex with TMEM16A through a PDZ-based interaction. We conclude that TMEM16A is a luminal Cl− channel in the intestine that functionally interacts with CFTR via PDZ-based interaction of NHERF1 for efficient and specific cholinergic stimulation of intestinal Cl− secretion. TMEM16A express apically and operate Cl− secretion in mouse intestinal tissue. TMEM16A potentially interacts with NHERF1 via its C-terminal PDZ binding motif. TMEM16A-NHERF1 complex is requisite for cAMP and Ca2+ mediated apical Cl− secretion.
Collapse
Affiliation(s)
- Tultul Saha
- Pathophysiology Division, National Institute of Cholera & Enteric Diseases, Kolkata, India
| | - Joydeep Aoun
- Pathophysiology Division, National Institute of Cholera & Enteric Diseases, Kolkata, India.,Department of Pharmacology, The Center for Cardiovascular Research, Center of Biomedical Research Excellence for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, Reno, NV, United States
| | - Mikio Hayashi
- Dept. of Cell Physiology, Institute of Biomedical Science, Kansai Medical University, Hirakata, Japan
| | - Sheikh Irshad Ali
- Pathophysiology Division, National Institute of Cholera & Enteric Diseases, Kolkata, India
| | - Paramita Sarkar
- Pathophysiology Division, National Institute of Cholera & Enteric Diseases, Kolkata, India
| | - Prasanta Kumar Bag
- Dept. of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, India
| | - Normand Leblanc
- Department of Pharmacology, The Center for Cardiovascular Research, Center of Biomedical Research Excellence for Molecular and Cellular Signal Transduction in the Cardiovascular System, University of Nevada, Reno School of Medicine, Reno, NV, United States
| | - Nadia Ameen
- Department of Pediatrics/Gastroenterology and Hepatology, Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, United States
| | - Owen M Woodward
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Kazi Mirajul Hoque
- Pathophysiology Division, National Institute of Cholera & Enteric Diseases, Kolkata, India.,Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| |
Collapse
|
28
|
Prignano L, Herchenroder L, Dempski RE. Characterizing Channelrhodopsin Channel Properties Via Two-Electrode Voltage Clamp and Kinetic Modeling. Methods Mol Biol 2021; 2191:49-63. [PMID: 32865738 DOI: 10.1007/978-1-0716-0830-2_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two-electrode voltage clamp (TEVC) is a preferred electrophysiological technique used to study gating kinetics and ion selectivity of light-activated channelrhodopsins (ChRs). The method uses two intracellular microelectrodes to hold, or clamp, the membrane potential at a specific value and measure the flow of ions across the plasma membrane. Here, we describe the use of TEVC and a simple solution exchange protocol to measure cation selectivity and analyze gating kinetics of the C1C2 chimera expressed in Xenopus laevis oocytes. Detailed instructions on how to process the collected data and interpret the results are also provided.
Collapse
Affiliation(s)
- Lindsey Prignano
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Lauren Herchenroder
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Robert E Dempski
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA.
| |
Collapse
|
29
|
Unraveling the Molecular Players at the Cholinergic Efferent Synapse of the Zebrafish Lateral Line. J Neurosci 2020; 41:47-60. [PMID: 33203744 DOI: 10.1523/jneurosci.1772-20.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/25/2020] [Accepted: 10/30/2020] [Indexed: 12/26/2022] Open
Abstract
The lateral line (LL) is a sensory system that allows fish and amphibians to detect water currents. LL responsiveness is modulated by efferent neurons that aid in distinguishing between external and self-generated stimuli, maintaining sensitivity to relevant cues. One component of the efferent system is cholinergic, the activation of which inhibits afferent activity. LL hair cells (HCs) share structural, functional, and molecular similarities with those of the cochlea, making them a popular model for studying human hearing and balance disorders. Because of these commonalities, one could propose that the receptor at the LL efferent synapse is a α9α10 nicotinic acetylcholine receptor (nAChR). However, the identities of the molecular players underlying ACh-mediated inhibition in the LL remain unknown. Surprisingly, through the analysis of single-cell expression studies and in situ hybridization, we describe that α9, but not the α10, subunits are enriched in zebrafish HCs. Moreover, the heterologous expression of zebrafish α9 subunits indicates that homomeric receptors are functional and exhibit robust ACh-gated currents blocked by α-bungarotoxin and strychnine. In addition, in vivo Ca2+ imaging on mechanically stimulated zebrafish LL HCs show that ACh elicits a decrease in evoked Ca2+ signals, regardless of HC polarity. This effect is blocked by both α-bungarotoxin and apamin, indicating coupling of ACh-mediated effects to small-conductance Ca2+-activated potassium (SKs) channels. Our results indicate that an α9-containing (α9*) nAChR operates at the zebrafish LL efferent synapse. Moreover, the activation of α9* nAChRs most likely leads to LL HC hyperpolarization served by SK channels.SIGNIFICANCE STATEMENT The fish lateral line (LL) mechanosensory system shares structural, functional, and molecular similarities with those of the mammalian cochlea. Thus, it has become an accessible model for studying human hearing and balance disorders. However, the molecular players serving efferent control of LL hair cell (HC) activity have not been identified. Here we demonstrate that, different from the hearing organ of vertebrate species, a nicotinic acetylcholine receptor composed only of α9 subunits operates at the LL efferent synapse. Activation of α9-containing receptors leads to LL HC hyperpolarization because of the opening of small-conductance Ca2+-activated potassium channels. These results will further aid in the interpretation of data obtained from LL HCs as a model for cochlear HCs.
Collapse
|
30
|
Henry C, Cens T, Charnet P, Cohen-Solal C, Collet C, van-Dijk J, Guiramand J, de Jésus-Ferreira MC, Menard C, Mokrane N, Roussel J, Thibault JB, Vignes M, Rousset M. Heterogeneous expression of GABA receptor-like subunits LCCH3 and GRD reveals functional diversity of GABA receptors in the honeybee Apis mellifera. Br J Pharmacol 2020; 177:3924-3940. [PMID: 32436264 DOI: 10.1111/bph.15135] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 04/24/2020] [Accepted: 05/09/2020] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND AND PURPOSE Despite a growing awareness, annual losses of honeybee colonies worldwide continue to reach threatening levels for food safety and global biodiversity. Among the biotic and abiotic stresses probably responsible for these losses, pesticides, including those targeting ionotropic GABA receptors, are one of the major drivers. Most insect genomes include the ionotropic GABA receptor subunit gene, Rdl, and two GABA-like receptor subunit genes, Lcch3 and Grd. Most studies have focused on Rdl which forms homomeric GABA-gated chloride channels, and a complete analysis of all possible molecular combinations of GABA receptors is still lacking. EXPERIMENTAL APPROACH We cloned the Rdl, Grd, and Lcch3 genes of Apis mellifera and systematically characterized the resulting GABA receptors expressed in Xenopus oocytes, using electrophysiological assays, fluorescence microscopy and co-immunoprecipitation techniques. KEY RESULTS The cloned subunits interacted with each other, forming GABA-gated heteromeric channels with particular properties. Strikingly, these heteromers were always more sensitive than AmRDL homomer to all the pharmacological agents tested. In particular, when expressed together, Grd and Lcch3 form a non-selective cationic channel that opens at low concentrations of GABA and with sensitivity to insecticides similar to that of homomeric Rdl channels. CONCLUSION AND IMPLICATIONS For off-target species like the honeybee, chronic sublethal exposure to insecticides constitutes a major threat. At these concentration ranges, homomeric RDL receptors may not be the most pertinent target to study and other ionotropic GABA receptor subtypes should be considered in order to understand more fully the molecular mechanisms of sublethal toxicity to insecticides.
Collapse
Affiliation(s)
| | - Thierry Cens
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Pierre Charnet
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Claude Collet
- UR 406 Abeilles et Environnement, INRAE, Avignon Cedex 9, France
| | | | | | | | - Claudine Menard
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Nawfel Mokrane
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Julien Roussel
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Michel Vignes
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Matthieu Rousset
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| |
Collapse
|
31
|
Walther F, Feind D, Vom Dahl C, Müller CE, Kukaj T, Sattler C, Nagel G, Gao S, Zimmer T. Action potentials in Xenopus oocytes triggered by blue light. J Gen Physiol 2020; 152:151581. [PMID: 32211871 PMCID: PMC7201882 DOI: 10.1085/jgp.201912489] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 02/24/2020] [Indexed: 11/20/2022] Open
Abstract
Voltage-gated sodium (Na+) channels are responsible for the fast upstroke of the action potential of excitable cells. The different α subunits of Na+ channels respond to brief membrane depolarizations above a threshold level by undergoing conformational changes that result in the opening of the pore and a subsequent inward flux of Na+. Physiologically, these initial membrane depolarizations are caused by other ion channels that are activated by a variety of stimuli such as mechanical stretch, temperature changes, and various ligands. In the present study, we developed an optogenetic approach to activate Na+ channels and elicit action potentials in Xenopus laevis oocytes. All recordings were performed by the two-microelectrode technique. We first coupled channelrhodopsin-2 (ChR2), a light-sensitive ion channel of the green alga Chlamydomonas reinhardtii, to the auxiliary β1 subunit of voltage-gated Na+ channels. The resulting fusion construct, β1-ChR2, retained the ability to modulate Na+ channel kinetics and generate photosensitive inward currents. Stimulation of Xenopus oocytes coexpressing the skeletal muscle Na+ channel Nav1.4 and β1-ChR2 with 25-ms lasting blue-light pulses resulted in rapid alterations of the membrane potential strongly resembling typical action potentials of excitable cells. Blocking Nav1.4 with tetrodotoxin prevented the fast upstroke and the reversal of the membrane potential. Coexpression of the voltage-gated K+ channel Kv2.1 facilitated action potential repolarization considerably. Light-induced action potentials were also obtained by coexpressing β1-ChR2 with either the neuronal Na+ channel Nav1.2 or the cardiac-specific isoform Nav1.5. Potential applications of this novel optogenetic tool are discussed.
Collapse
Affiliation(s)
- Florian Walther
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Dominic Feind
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christian Vom Dahl
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christoph Emanuel Müller
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Taulant Kukaj
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christian Sattler
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Georg Nagel
- Institute of Physiology-Neurophysiology, Biocentre, Julius-Maximilians-University, Wuerzburg, Germany
| | - Shiqiang Gao
- Institute of Physiology-Neurophysiology, Biocentre, Julius-Maximilians-University, Wuerzburg, Germany
| | - Thomas Zimmer
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| |
Collapse
|
32
|
Shi S, Pang C, Guo S, Chen Y, Ma B, Qu C, Ji Q, An H. Recent progress in structural studies on TMEM16A channel. Comput Struct Biotechnol J 2020; 18:714-722. [PMID: 32257055 PMCID: PMC7118279 DOI: 10.1016/j.csbj.2020.03.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 03/12/2020] [Accepted: 03/13/2020] [Indexed: 11/26/2022] Open
Abstract
The calcium-activated chloride channel, also known as TMEM16A, shows both calcium and membrane potential dependent activation. The channel is expressed broadly and contributes to a variety of physiological processes, and it is expected to be a target for the treatment of diseases such as hypertension, pain, cystic fibrosis and lung cancer. A thorough understanding of the structural characteristics of TMEM16A is important to reveal its physiological and pathological roles. Recent studies have released several Cryo-EM structures of the channel, revealed the structural basis and mechanism of the gating of the channel. This review focused on the understandings of the structural basis and molecular mechanism of the gating and permeation of TMEM16A channel, which will provide important basis for the development of drugs targeting TMEM16A.
Collapse
Affiliation(s)
- Sai Shi
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Chunli Pang
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Shuai Guo
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Yafei Chen
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Biao Ma
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Chang Qu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Qiushuang Ji
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| | - Hailong An
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin 300401, China.,Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin, 300401, China
| |
Collapse
|
33
|
|
34
|
Wang Z, Ng C, Liu X, Wang Y, Li B, Kashyap P, Chaudhry HA, Castro A, Kalontar EM, Ilyayev L, Walker R, Alexander RT, Qian F, Chen X, Yu Y. The ion channel function of polycystin-1 in the polycystin-1/polycystin-2 complex. EMBO Rep 2019; 20:e48336. [PMID: 31441214 PMCID: PMC6832002 DOI: 10.15252/embr.201948336] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/30/2019] [Accepted: 08/01/2019] [Indexed: 12/15/2022] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 or PKD2 gene, encoding the polycystic kidney disease protein polycystin-1 and the transient receptor potential channel polycystin-2 (also known as TRPP2), respectively. Polycystin-1 and polycystin-2 form a receptor-ion channel complex located in primary cilia. The function of this complex, especially the role of polycystin-1, is largely unknown due to the lack of a reliable functional assay. In this study, we dissect the role of polycystin-1 by directly recording currents mediated by a gain-of-function (GOF) polycystin-1/polycystin-2 channel. Our data show that this channel has distinct properties from that of the homomeric polycystin-2 channel. The polycystin-1 subunit directly contributes to the channel pore, and its eleven transmembrane domains are sufficient for its channel function. We also show that the cleavage of polycystin-1 at the N-terminal G protein-coupled receptor proteolysis site is not required for the activity of the GOF polycystin-1/polycystin-2 channel. These results demonstrate the ion channel function of polycystin-1 in the polycystin-1/polycystin-2 complex, enriching our understanding of this channel and its role in ADPKD.
Collapse
Affiliation(s)
- Zhifei Wang
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Courtney Ng
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Xiong Liu
- Department of Physiology, Membrane Protein Disease Research GroupFaculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanada
| | - Yan Wang
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Bin Li
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Parul Kashyap
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | | | - Alexis Castro
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | | | - Leah Ilyayev
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| | - Rebecca Walker
- Division of NephrologyDepartment of MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - R Todd Alexander
- Departments of Pediatrics and PhysiologyUniversity of AlbertaEdmontonABCanada
| | - Feng Qian
- Division of NephrologyDepartment of MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Xing‐Zhen Chen
- Department of Physiology, Membrane Protein Disease Research GroupFaculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanada
| | - Yong Yu
- Department of Biological SciencesSt. John's UniversityQueensNYUSA
| |
Collapse
|
35
|
Shimomura T, Kubo Y. Phosphoinositides modulate the voltage dependence of two-pore channel 3. J Gen Physiol 2019; 151:986-1006. [PMID: 31182502 PMCID: PMC6683669 DOI: 10.1085/jgp.201812285] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 04/26/2019] [Accepted: 05/23/2019] [Indexed: 02/03/2023] Open
Abstract
Two-pore channels, or two-pore Na+ channels (TPCs), contain two homologous domains, each containing a functional unit typical of voltage-dependent cation channels. Each domain is considered to be responsible for either phosphoinositide (PI) binding or voltage sensing. Among the three members of the TPC family, TPC1 and TPC2 are activated by PI(3,5)P2, while TPC3 has been thought not to be affected by any PIs. Here, we report that TPC3 is sensitive to PI(3,4)P2 and PI(3,5)P2, but not to PI(4,5)P2, and that the extremely slow increase in TPC3 currents induced by depolarization in Xenopus oocytes is due to the production of PI(3,4)P2 Similarly to TPC1, the cluster of basic amino acid residues in domain I is critical for PI sensitivity, but with a slight variation that may allow TPC3 to be sensitive to both PI(3,4)P2 and PI(3,5)P2 We also found that TPC3 has a unique PI-dependent modulation mechanism of voltage dependence, which is achieved by a specific bridging interaction between domain I and domain II. Taken together, these findings show that TPC3 is a unique member of the TPC family that senses PIs and displays a strong coupling between PI binding and voltage-dependent gating.
Collapse
Affiliation(s)
- Takushi Shimomura
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Japan .,Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Japan
| |
Collapse
|
36
|
On the mechanism of the electrophysiological changes and membrane lesions induced by asbestos fiber exposure in Xenopus laevis oocytes. Sci Rep 2019; 9:2014. [PMID: 30765791 PMCID: PMC6376119 DOI: 10.1038/s41598-019-38591-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 12/10/2018] [Indexed: 01/09/2023] Open
Abstract
The so-called amphibole asbestos fibers are enriched with mineral iron ions, able to stimulate ROS production. We recently reported that crocidolite asbestos was able to interact with the cell membranes of Xenopus laevis oocytes, to alter their electrical membrane properties. Here, we found that applied iron ions (Fe3+) or H2O2 (for ROS generation) mimicked these effects, suggesting that at least one effect of iron-containing asbestos fiber exposure was mediated by ROS production. Furthermore, combined Fe3+ and H2O2 acted synergistically, producing a membrane effect stronger than that induced by these factors alone. Similar to crocidolite, these changes peaked within 30 minutes of incubation and vanished almost completely after 120 min. However, in the presence of cytochalasin D, which inhibits membrane actin repair mechanisms, crocidolite or applied Fe3+/H2O2 invariably produced oocyte cell death. While the electrophysiological modifications induced by crocidolite suggested a modification of an intrinsic chloride ion channel, the morphological appearance of the treated oocytes also indicated the formation of membrane “pores”; the effects of asbestos exposure may therefore consist of multiple (not necessarily exclusive) underlying mechanisms. In conclusion, using Xenopus oocytes allowed us for the first time, to focus on a specific membrane effect of crocidolite asbestos exposure, which deserves to be tested also on human lung cell lines. Much available evidence suggests that asbestos fibers damage cells through the production of ROS. Our present data confirm that crocidolite fibers can indeed trigger ROS-mediated damaging effects in the oocyte cell membrane, provided iron ions and H2O2 are available for ROS production.
Collapse
|
37
|
Durant F, Bischof J, Fields C, Morokuma J, LaPalme J, Hoi A, Levin M. The Role of Early Bioelectric Signals in the Regeneration of Planarian Anterior/Posterior Polarity. Biophys J 2019; 116:948-961. [PMID: 30799071 DOI: 10.1016/j.bpj.2019.01.029] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 01/11/2019] [Accepted: 01/16/2019] [Indexed: 01/14/2023] Open
Abstract
Axial patterning during planarian regeneration relies on a transcriptional circuit that confers distinct positional information on the two ends of an amputated fragment. The earliest known elements of this system begin demarcating differences between anterior and posterior wounds by 6 h postamputation. However, it is still unknown what upstream events break the axial symmetry, allowing a mutual repressor system to establish invariant, distinct biochemical states at the anterior and posterior ends. Here, we show that bioelectric signaling at 3 h is crucial for the formation of proper anterior-posterior polarity in planaria. Briefly manipulating the endogenous bioelectric state by depolarizing the injured tissue during the first 3 h of regeneration alters gene expression by 6 h postamputation and leads to a double-headed phenotype upon regeneration despite confirmed washout of ionophores from tissue. These data reveal a primary functional role for resting membrane potential taking place within the first 3 h after injury and kick-starting the downstream pattern of events that elaborate anatomy over the following 10 days. We propose a simple model of molecular-genetic mechanisms to explain how physiological events taking place immediately after injury regulate the spatial distribution of downstream gene expression and anatomy of regenerating planaria.
Collapse
Affiliation(s)
- Fallon Durant
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Johanna Bischof
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Chris Fields
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Junji Morokuma
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Joshua LaPalme
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Alison Hoi
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Michael Levin
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts.
| |
Collapse
|
38
|
Pan Y, Chai X, Gao Q, Zhou L, Zhang S, Li L, Luan S. Dynamic Interactions of Plant CNGC Subunits and Calmodulins Drive Oscillatory Ca 2+ Channel Activities. Dev Cell 2019; 48:710-725.e5. [PMID: 30713075 DOI: 10.1016/j.devcel.2018.12.025] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 10/03/2018] [Accepted: 12/28/2018] [Indexed: 12/20/2022]
Abstract
Calcium is a universal signal in all eukaryotes, but the mechanism for encoding calcium signatures remains largely unknown. Calcium oscillations control pollen tube growth and fertilization in flowering plants, serving as a model for dissecting the molecular machines that mediate calcium fluctuations. We report that pollen-tube-specific cyclic nucleotide-gated channels (CNGC18, CNGC8, and CNGC7) together with calmodulin 2 (CaM2) constitute a molecular switch that either opens or closes the calcium channel depending on cellular calcium levels. Under low calcium, calcium-free calmodulin 2 (Apo-CaM2) interacts with CNGC18-CNGC8 complex, leading to activation of the influx channel and consequently increasing cytosolic calcium levels. Calcium-bound CaM2 dissociates from CNGC18/8 heterotetramer, closing the channel and initiating a downturn of cellular calcium levels. We further reconstituted the calcium oscillator in HEK293 cells, supporting the model that Ca2+-CaM-dependent regulation of CNGC channel activity provides an auto-regulatory feedback mechanism for calcium oscillations during pollen tube growth.
Collapse
Affiliation(s)
- Yajun Pan
- College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Xuyang Chai
- College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Qifei Gao
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Liming Zhou
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Sisi Zhang
- College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Legong Li
- College of Life Sciences, Capital Normal University, Beijing 100048, China.
| | - Sheng Luan
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
| |
Collapse
|
39
|
Ji Q, Guo S, Wang X, Pang C, Zhan Y, Chen Y, An H. Recent advances in TMEM16A: Structure, function, and disease. J Cell Physiol 2018; 234:7856-7873. [PMID: 30515811 DOI: 10.1002/jcp.27865] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 11/13/2018] [Indexed: 12/13/2022]
Abstract
TMEM16A (also known as anoctamin 1, ANO1) is the molecular basis of the calcium-activated chloride channels, with ten transmembrane segments. Recently, atomic structures of the transmembrane domains of mouse TMEM16A (mTMEM16A) were determined by single-particle electron cryomicroscopy. This gives us a solid ground to discuss the electrophysiological properties and functions of TMEM16A. TMEM16A is reported to be dually regulated by Ca2+ and voltage. In addition, the dysfunction of TMEM16A has been found to be involved in many diseases including cystic fibrosis, various cancers, hypertension, and gastrointestinal motility disorders. TMEM16A is overexpressed in many cancers, including gastrointestinal stromal tumors, gastric cancer, head and neck squamous cell carcinoma (HNSCC), colon cancer, pancreatic ductal adenocarcinoma, and esophageal cancer. Furthermore, overexpression of TMEM16A is related to the occurrence, proliferation, and migration of tumor cells. To date, several studies have shown that many natural compounds and synthetic compounds have regulatory effects on TMEM16A. These small molecule compounds might be novel drugs for the treatment of diseases caused by TMEM16A dysfunction in the future. In addition, recent studies have shown that TMEM16A plays different roles in different diseases through different signal transduction pathways. This review discusses the topology, electrophysiological properties, modulators and functions of TMEM16A in mediates nociception, gastrointestinal dysfunction, hypertension, and cancer and focuses on multiple regulatory mechanisms regarding TMEM16A.
Collapse
Affiliation(s)
- Qiushuang Ji
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Shuai Guo
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Xuzhao Wang
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Chunli Pang
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Yong Zhan
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Yafei Chen
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Hailong An
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| |
Collapse
|
40
|
Savalli N, Pantazis A, Sigg D, Weiss JN, Neely A, Olcese R. The α2δ-1 subunit remodels CaV1.2 voltage sensors and allows Ca2+ influx at physiological membrane potentials. J Gen Physiol 2017; 148:147-59. [PMID: 27481713 PMCID: PMC4969795 DOI: 10.1085/jgp.201611586] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/30/2016] [Indexed: 12/30/2022] Open
Abstract
Voltage-sensing domains (VSDs) in voltage-gated calcium channels sense the potential difference across membranes and interact with the pore to open it. Savalli et al. find that the accessory subunit α2δ-1 increases the sensitivity of VSDs I–III and also their efficiency of coupling to the pore. Excitation-evoked calcium influx across cellular membranes is strictly controlled by voltage-gated calcium channels (CaV), which possess four distinct voltage-sensing domains (VSDs) that direct the opening of a central pore. The energetic interactions between the VSDs and the pore are critical for tuning the channel’s voltage dependence. The accessory α2δ-1 subunit is known to facilitate CaV1.2 voltage-dependent activation, but the underlying mechanism is unknown. In this study, using voltage clamp fluorometry, we track the activation of the four individual VSDs in a human L-type CaV1.2 channel consisting of α1C and β3 subunits. We find that, without α2δ-1, the channel complex displays a right-shifted voltage dependence such that currents mainly develop at nonphysiological membrane potentials because of very weak VSD–pore interactions. The presence of α2δ-1 facilitates channel activation by increasing the voltage sensitivity (i.e., the effective charge) of VSDs I–III. Moreover, the α2δ-1 subunit also makes VSDs I–III more efficient at opening the channel by increasing the coupling energy between VSDs II and III and the pore, thus allowing Ca influx within the range of physiological membrane potentials.
Collapse
Affiliation(s)
- Nicoletta Savalli
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Antonios Pantazis
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | | | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Alan Neely
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Riccardo Olcese
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| |
Collapse
|
41
|
AMPA glutamate receptors are required for sensory-organ formation and morphogenesis in the basal chordate. Proc Natl Acad Sci U S A 2017; 114:3939-3944. [PMID: 28348228 DOI: 10.1073/pnas.1612943114] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
AMPA-type glutamate receptors (GluAs) mediate fast excitatory transmission in the vertebrate central nervous system (CNS), and their function has been extensively studied in the mature mammalian brain. However, GluA expression begins very early in developing embryos, suggesting that they may also have unidentified developmental roles. Here, we identify developmental roles for GluAs in the ascidian Ciona intestinalis Mammals express Ca2+-permeable GluAs (Ca-P GluAs) and Ca2+-impermeable GluAs (Ca-I GluAs) by combining subunits derived from four genes. In contrast, ascidians have a single gluA gene. Taking advantage of the simple genomic GluA organization in ascidians, we knocked down (KD) GluAs in Ciona and observed severe impairments in formation of the ocellus, a photoreceptive organ used during the swimming stage, and in resorption of the tail and body axis rotation during metamorphosis to the adult stage. These defects could be rescued by injection of KD-resistant GluAs. GluA KD phenotypes could also be reproduced by expressing a GluA mutant that dominantly inhibits glutamate-evoked currents. These results suggest that, in addition to their role in synaptic communication in mature animals, GluAs also have critical developmental functions.
Collapse
|
42
|
Fertility: Store-Operated Ca 2+ Entry in Germ Cells: Role in Egg Activation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:577-593. [PMID: 28900934 DOI: 10.1007/978-3-319-57732-6_29] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
At the time of fertilization, the sperm activates the egg and induces embryonic development by triggering an elevation in the egg's intracellular free Ca2+ concentration. In mammals the initial Ca2+ rise is followed by a series of repetitive Ca2+ transients (known as oscillations) that last for several hours. Although the source of Ca2+ during the signaling process is primarily the egg's smooth endoplasmic reticulum, the oscillations stop in the absence of extracellular Ca2+ indicating that a Ca2+ influx across the plasma membrane is essential to sustain them. Depletion of the intracellular stores using specific inhibitors generates a Ca2+ entry across the plasma membrane of eggs of various species, and a continuous influx of Ca2+ has been linked to the sperm-induced Ca2+ oscillations in the mouse; these data indicate that store-operated Ca2+ entry (SOCE) operates in eggs and may be the mechanism that maintains the long-lasting Ca2+ signal at fertilization. Recent findings suggest that the signaling proteins STIM1 and Orai1 are present in eggs; they are responsible for mediating SOCE, and their functions are essential for proper Ca2+ signaling at fertilization to support normal embryo development.
Collapse
|
43
|
Kamikawa A, Ichii O, Sakazaki J, Ishikawa T. Ca2+-activated Cl− channel currents in mammary secretory cells from lactating mouse. Am J Physiol Cell Physiol 2016; 311:C808-C819. [DOI: 10.1152/ajpcell.00050.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 08/19/2016] [Indexed: 11/22/2022]
Abstract
The Cl− secretion via Ca2+-activated Cl− channel (CaCC) is critical for fluid secretion in exocrine glands like the salivary gland. Also in the mammary gland, it has been hypothesized that CaCC plays an important role in the secretion of Cl− and aqueous phase of milk. However, there has been no evidence for the functional expression of CaCC in native mammary secretory (MS) cells of lactating animals. We therefore assessed membrane current in MS cells that were freshly isolated from lactating mice using whole cell patch-clamp techniques. In MS cells, we detected CaCC current that exhibited the following characteristics: 1) Ca2+-dependent activation at the concentrations of submicromolar range; 2) voltage-dependent activation; 3) slow kinetics for activation and deactivation; 4) outward rectification of the steady-state current; 5) anion permeability in the sequence of I− > NO3− > Br− > Cl− >> glutamate; 6) inhibition by Cl− channel blockers (niflumic acid, DIDS, and CaCCinh-A01). These characteristics of native CaCC current were similar to reported characteristics of heterologously expressed TMEM16A. RT-PCR analyses showed the expression of multiple CaCC channels including TMEM16A, Best1, and Best3 in the mammary glands of lactating mice. Immunohistochemical staining revealed the localization of TMEM16A protein at the apical membrane of the MS cells. Collectively, our data strongly suggest that MS cells functionally express CaCC, which is at least partly constituted by TMEM16A. The CaCC such as TMEM16A at the apical membrane of the MS cells may influence the quantity and/or quality of milk.
Collapse
Affiliation(s)
- Akihiro Kamikawa
- Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan; and
| | - Osamu Ichii
- Laboratory of Anatomy, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Junpei Sakazaki
- Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan; and
| | - Toru Ishikawa
- Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan; and
| |
Collapse
|
44
|
Functional aspects of early brain development are preserved in tuberous sclerosis complex (TSC) epileptogenic lesions. Neurobiol Dis 2016; 95:93-101. [DOI: 10.1016/j.nbd.2016.07.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 07/05/2016] [Accepted: 07/13/2016] [Indexed: 02/04/2023] Open
|
45
|
Xu Z, Wu Q, Xu Q, He L. From the Cover: Functional Analysis Reveals Glutamate and Gamma-Aminobutyric Acid-Gated Chloride Channels as Targets of Avermectins in the Carmine Spider Mite. Toxicol Sci 2016; 155:258-269. [DOI: 10.1093/toxsci/kfw210] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
|
46
|
Ma K, Wang H, Yu J, Wei M, Xiao Q. New Insights on the Regulation of Ca 2+ -Activated Chloride Channel TMEM16A. J Cell Physiol 2016; 232:707-716. [PMID: 27682822 DOI: 10.1002/jcp.25621] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 09/27/2016] [Indexed: 12/16/2022]
Abstract
TMEM16A, also known as anoctamin 1, is a recently identified Ca2+ -activated chloride channel and the first member of a 10-member TMEM16 family. TMEM16A dysfunction is implicated in many diseases such as cancer, hypertension, and cystic fibrosis. TMEM16A channels are well known to be dually regulated by voltage and Ca2+ . In addition, recent studies have revealed that TMEM16A channels are regulated by many molecules such as calmodulin, protons, cholesterol, and phosphoinositides, and a diverse range of stimuli such as thermal and mechanical stimuli. A better understanding of the regulatory mechanisms of TMEM16A is important to understand its physiological and pathological role. Recently, the crystal structure of a TMEM16 family member from the fungus Nectria haematococcaten (nhTMEM16) is discovered, and provides valuable information for studying the structure and function of TMEM16A. In this review, we discuss the structure and function of TMEM16A channels based on the crystal structure of nhTMEM16A and focus on the regulatory mechanisms of TMEM16A channels. J. Cell. Physiol. 232: 707-716, 2017. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Ke Ma
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Hui Wang
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Jiankun Yu
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Minjie Wei
- Department of Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Qinghuan Xiao
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| |
Collapse
|
47
|
Klaassen LJ, de Graaff W, van Asselt JB, Klooster J, Kamermans M. Specific connectivity between photoreceptors and horizontal cells in the zebrafish retina. J Neurophysiol 2016; 116:2799-2814. [PMID: 27707811 DOI: 10.1152/jn.00449.2016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 09/30/2016] [Indexed: 11/22/2022] Open
Abstract
The functional and morphological connectivity between various horizontal cell (HC) types (H1, H2, H3, and H4) and photoreceptors was studied in zebrafish retina. Since HCs are strongly coupled by gap junctions and feedback from HCs to photoreceptors depends strongly on connexin (Cx) hemichannels, we characterized the various HC Cxs (Cx52.6, Cx52.7, Cx52.9, and Cx55.5) in Xenopus oocytes. All Cxs formed hemichannels that were conducting at physiological membrane potentials. The Cx hemichannels differed in kinetic properties and voltage dependence, allowing for specific tuning of the coupling of HCs and the feedback signal from HCs to cones. The morphological connectivity between HC layers and cones was determined next. We used zebrafish expressing green fluorescent protein under the control of Cx promoters. We found that all HCs showed Cx55.5 promoter activity. Cx52.7 promoter activity was exclusively present in H4 cells, while Cx52.9 promoter activity occurred only in H1 cells. Cx52.6 promoter activity was present in H4 cells and in the ventral quadrant of the retina also in H1 cells. Finally, we determined the spectral sensitivities of the HC layers. Three response types were found. Monophasic responses were generated by HCs that contacted all cones (H1 cells), biphasic responses were generated by HCs that contacted M, S, and UV cones (H2 cells), and triphasic responses were generated by HCs that contacted either S and UV cones (H3 cells) or rods and UV cones (H4 cells). Electron microscopy confirms that H4 cells innervate cones. This indicates that rod-driven HCs process spectral information during photopic and luminance information during scotopic conditions.
Collapse
Affiliation(s)
- Lauw J Klaassen
- Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and
| | - Wim de Graaff
- Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and
| | - Jorrit B van Asselt
- Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and
| | - Jan Klooster
- Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and
| | - Maarten Kamermans
- Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and .,Department of Genome Analysis, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| |
Collapse
|
48
|
Cater RJ, Vandenberg RJ, Ryan RM. Tuning the ion selectivity of glutamate transporter-associated uncoupled conductances. J Gen Physiol 2016; 148:13-24. [PMID: 27296367 PMCID: PMC4924932 DOI: 10.1085/jgp.201511556] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 05/17/2016] [Indexed: 12/11/2022] Open
Abstract
Excitatory amino acid transporters possess a Cl− conductance whose direction is independent of that of the substrate. By mutating an arginine residue in the putative anion permeation pathway, Cater et al. show that a positive charge at this position determines anion selectivity. The concentration of glutamate within a glutamatergic synapse is tightly regulated by excitatory amino acid transporters (EAATs). In addition to their primary role in clearing extracellular glutamate, the EAATs also possess a thermodynamically uncoupled Cl− conductance. This conductance is activated by the binding of substrate and Na+, but the direction of Cl− flux is independent of the rate or direction of substrate transport; thus, the two processes are thermodynamically uncoupled. A recent molecular dynamics study of the archaeal EAAT homologue GltPh (an aspartate transporter from Pyrococcus horikoshii) identified an aqueous pore at the interface of the transport and trimerization domains, through which anions could permeate, and it was suggested that an arginine residue at the most restricted part of this pathway might play a role in determining anion selectivity. In this study, we mutate this arginine to a histidine in the human glutamate transporter EAAT1 and investigate the role of the protonation state of this residue on anion selectivity and transporter function. Our results demonstrate that a positive charge at this position is crucial for determining anion versus cation selectivity of the uncoupled conductance of EAAT1. In addition, because the nature of this residue influences the turnover rate of EAAT1, we reveal an intrinsic link between the elevator movement of the transport domain and the Cl− channel.
Collapse
Affiliation(s)
- Rosemary J Cater
- Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia
| | - Robert J Vandenberg
- Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia
| | - Renae M Ryan
- Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia
| |
Collapse
|
49
|
Courjaret R, Hodeify R, Hubrack S, Ibrahim A, Dib M, Daas S, Machaca K. The Ca2+-activated Cl- channel Ano1 controls microvilli length and membrane surface area in the oocyte. J Cell Sci 2016; 129:2548-58. [PMID: 27173493 DOI: 10.1242/jcs.188367] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 05/02/2016] [Indexed: 12/12/2022] Open
Abstract
Ca(2+)-activated Cl(-) channels (CaCCs) play important physiological functions in epithelia and other tissues. In frog oocytes the CaCC Ano1 regulates resting membrane potential and the block to polyspermy. Here, we show that Ano1 expression increases the oocyte surface, revealing a novel function for Ano1 in regulating cell morphology. Confocal imaging shows that Ano1 increases microvilli length, which requires ERM-protein-dependent linkage to the cytoskeleton. A dominant-negative form of the ERM protein moesin precludes the Ano1-dependent increase in membrane area. Furthermore, both full-length and the truncated dominant-negative forms of moesin co-localize with Ano1 to the microvilli, and the two proteins co-immunoprecipitate. The Ano1-moesin interaction limits Ano1 lateral membrane mobility and contributes to microvilli scaffolding, therefore stabilizing larger membrane structures. Collectively, these results reveal a newly identified role for Ano1 in shaping the plasma membrane during oogenesis, with broad implications for the regulation of microvilli in epithelia.
Collapse
Affiliation(s)
- Raphael Courjaret
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| | - Rawad Hodeify
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| | - Satanay Hubrack
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| | - Awab Ibrahim
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| | - Maya Dib
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| | - Sahar Daas
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| | - Khaled Machaca
- Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City - Qatar Foundation, Luqta Street, PO Box 24144, Doha 24144, Qatar
| |
Collapse
|
50
|
Function and regulation of TRPP2 ion channel revealed by a gain-of-function mutant. Proc Natl Acad Sci U S A 2016; 113:E2363-72. [PMID: 27071085 DOI: 10.1073/pnas.1517066113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mutations in polycystin-1 and transient receptor potential polycystin 2 (TRPP2) account for almost all clinically identified cases of autosomal dominant polycystic kidney disease (ADPKD), one of the most common human genetic diseases. TRPP2 functions as a cation channel in its homomeric complex and in the TRPP2/polycystin-1 receptor/ion channel complex. The activation mechanism of TRPP2 is unknown, which significantly limits the study of its function and regulation. Here, we generated a constitutively active gain-of-function (GOF) mutant of TRPP2 by applying a mutagenesis scan on the S4-S5 linker and the S5 transmembrane domain, and studied functional properties of the GOF TRPP2 channel. We found that extracellular divalent ions, including Ca(2+), inhibit the permeation of monovalent ions by directly blocking the TRPP2 channel pore. We also found that D643, a negatively charged amino acid in the pore, is crucial for channel permeability. By introducing single-point ADPKD pathogenic mutations into the GOF TRPP2, we showed that different mutations could have completely different effects on channel activity. The in vivo function of the GOF TRPP2 was investigated in zebrafish embryos. The results indicate that, compared with wild type (WT), GOF TRPP2 more efficiently rescued morphological abnormalities, including curly tail and cyst formation in the pronephric kidney, caused by down-regulation of endogenous TRPP2 expression. Thus, we established a GOF TRPP2 channel that can serve as a powerful tool for studying the function and regulation of TRPP2. The GOF channel may also have potential application for developing new therapeutic strategies for ADPKD.
Collapse
|