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Ko W, Lee E, Kim JE, Lim HH, Suh BC. The plasma membrane inner leaflet PI(4,5)P 2 is essential for the activation of proton-activated chloride channels. Nat Commun 2024; 15:7008. [PMID: 39143141 PMCID: PMC11324729 DOI: 10.1038/s41467-024-51400-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Accepted: 08/07/2024] [Indexed: 08/16/2024] Open
Abstract
Proton-activated chloride (PAC) channels, ubiquitously expressed in tissues, regulate intracellular Cl- levels and cell death following acidosis. However, molecular mechanisms and signaling pathways involved in PAC channel modulation are largely unknown. Herein, we determine that phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] of the plasma membrane inner leaflet is essential for the proton activation of PAC channels. PI(4,5)P2 depletion by activating phosphatidylinositol 5-phosphatases or Gq protein-coupled muscarinic receptors substantially inhibits human PAC currents. In excised inside-out patches, PI(4,5)P2 application to the cytoplasmic side increases the currents. Structural simulation reveals that the putative PI(4,5)P2-binding site is localized within the cytosol in resting state but shifts to the cell membrane's inner surface in an activated state and interacts with inner leaflet PI(4,5)P2. Alanine neutralization of basic residues near the membrane-cytosol interface of the transmembrane helice 2 significantly attenuates PAC currents. Overall, our study uncovers a modulatory mechanism of PAC channel through inner membrane PI(4,5)P2.
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Affiliation(s)
- Woori Ko
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
| | - Euna Lee
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
- Neurovascular Unit Research Group, Korea Brain Research Institute (KBRI), Daegu, 41068, Republic of Korea
| | - Jung-Eun Kim
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
| | - Hyun-Ho Lim
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea
- Neurovascular Unit Research Group, Korea Brain Research Institute (KBRI), Daegu, 41068, Republic of Korea
| | - Byung-Chang Suh
- Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea.
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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.
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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
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Sang Y, Niu C, Xu J, Zhu T, You S, Wang J, Zhang L, Du X, Zhang H. PI4KIIIβ-Mediated Phosphoinositides Metabolism Regulates Function of the VTA Dopaminergic Neurons and Depression-Like Behavior. J Neurosci 2024; 44:e0555232024. [PMID: 38267258 PMCID: PMC10941068 DOI: 10.1523/jneurosci.0555-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 12/18/2023] [Accepted: 01/11/2024] [Indexed: 01/26/2024] Open
Abstract
Phosphoinositides, including phosphatidylinositol-4,5-bisphosphate (PIP2), play a crucial role in controlling key cellular functions such as membrane and vesicle trafficking, ion channel, and transporter activity. Phosphatidylinositol 4-kinases (PI4K) are essential enzymes in regulating the turnover of phosphoinositides. However, the functional role of PI4Ks and mediated phosphoinositide metabolism in the central nervous system has not been fully revealed. In this study, we demonstrated that PI4KIIIβ, one of the four members of PI4Ks, is an important regulator of VTA dopaminergic neuronal activity and related depression-like behavior of mice by controlling phosphoinositide turnover. Our findings provide new insights into possible mechanisms and potential drug targets for neuropsychiatric diseases, including depression. Both sexes were studied in basic behavior tests, but only male mice could be used in the social defeat depression model.
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Affiliation(s)
- Yuqi Sang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Chenxu Niu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Jiaxi Xu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shanxi 710061, China
| | - Tiantian Zhu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Shuangzhu You
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Jing Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Ludi Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Department of Psychiatry, The First Hospital of Hebei Medical University, Mental Health Institute of Hebei Medical University, Shijiazhuang, Hebei 050000, China
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Jin Y, Xue J. Lipid kinases PIP5Ks and PIP4Ks: potential drug targets for breast cancer. Front Oncol 2023; 13:1323897. [PMID: 38156113 PMCID: PMC10753794 DOI: 10.3389/fonc.2023.1323897] [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: 10/18/2023] [Accepted: 11/29/2023] [Indexed: 12/30/2023] Open
Abstract
Phosphoinositides, a small group of lipids found in all cellular membranes, have recently garnered heightened attention due to their crucial roles in diverse biological processes and different diseases. Among these, phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), the most abundant bis-phosphorylated phosphoinositide within the signaling system, stands notably connected to breast cancer. Not only does it serve as a key activator of the frequently altered phosphatidylinositol 3-kinase (PI3K) pathway in breast cancer, but also its conversion to phosphatidylinositol-3,4,5-triphosphate (PI(3,4,5)P3) is an important direction for breast cancer research. The generation and degradation of phosphoinositides intricately involve phosphoinositide kinases. PI(4,5)P2 generation emanates from the phosphorylation of PI4P or PI5P by two lipid kinase families: Type I phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks) and Type II phosphatidylinositol-5-phosphate 4-kinases (PIP4Ks). In this comprehensive review, we focus on these two lipid kinases and delineate their compositions and respective cellular localization. Moreover, we shed light on the expression patterns and functions of distinct isoforms of these kinases in breast cancer. For a deeper understanding of their functional dynamics, we expound upon various mechanisms governing the regulation of PIP5Ks and PIP4Ks activities. A summary of effective and specific small molecule inhibitors designed for PIP5Ks or PIP4Ks are also provided. These growing evidences support PIP5Ks and PIP4Ks as promising drug targets for breast cancer.
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Affiliation(s)
- Yue Jin
- Department of Molecular Diagnosis, Northern Jiangsu People’s Hospital, Yangzhou University Clinical Medical College, Yangzhou, China
| | - Jian Xue
- Department of Emergency Medicine, Yizheng People’s Hospital, Yangzhou University Clinical Medical College, Yangzhou, China
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Akin EJ, Aoun J, Jimenez C, Mayne K, Baeck J, Young MD, Sullivan B, Sanders KM, Ward SM, Bulley S, Jaggar JH, Earley S, Greenwood IA, Leblanc N. ANO1, CaV1.2, and IP3R form a localized unit of EC-coupling in mouse pulmonary arterial smooth muscle. J Gen Physiol 2023; 155:e202213217. [PMID: 37702787 PMCID: PMC10499037 DOI: 10.1085/jgp.202213217] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 08/01/2023] [Accepted: 08/29/2023] [Indexed: 09/14/2023] Open
Abstract
Pulmonary arterial (PA) smooth muscle cells (PASMC) generate vascular tone in response to agonists coupled to Gq-protein receptor signaling. Such agonists stimulate oscillating calcium waves, the frequency of which drives the strength of contraction. These Ca2+ events are modulated by a variety of ion channels including voltage-gated calcium channels (CaV1.2), the Tmem16a or Anoctamin-1 (ANO1)-encoded calcium-activated chloride (CaCC) channel, and Ca2+ release from the sarcoplasmic reticulum through inositol-trisphosphate receptors (IP3R). Although these calcium events have been characterized, it is unclear how these calcium oscillations underly a sustained contraction in these muscle cells. We used smooth muscle-specific ablation of ANO1 and pharmacological tools to establish the role of ANO1, CaV1.2, and IP3R in the contractile and intracellular Ca2+ signaling properties of mouse PA smooth muscle expressing the Ca2+ biosensor GCaMP3 or GCaMP6. Pharmacological block or genetic ablation of ANO1 or inhibition of CaV1.2 or IP3R, or Ca2+ store depletion equally inhibited 5-HT-induced tone and intracellular Ca2+ waves. Coimmunoprecipitation experiments showed that an anti-ANO1 antibody was able to pull down both CaV1.2 and IP3R. Confocal and superresolution nanomicroscopy showed that ANO1 coassembles with both CaV1.2 and IP3R at or near the plasma membrane of PASMC from wild-type mice. We conclude that the stable 5-HT-induced PA contraction results from the integration of stochastic and localized Ca2+ events supported by a microenvironment comprising ANO1, CaV1.2, and IP3R. In this model, ANO1 and CaV1.2 would indirectly support cyclical Ca2+ release events from IP3R and propagation of intracellular Ca2+ waves.
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Affiliation(s)
- Elizabeth J. Akin
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Joydeep Aoun
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Connor Jimenez
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Katie Mayne
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Julius Baeck
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Michael D. Young
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Brennan Sullivan
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Sean M. Ward
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Simon Bulley
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Jonathan H. Jaggar
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Scott Earley
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Iain A. Greenwood
- Department of Vascular Pharmacology, Molecular and Clinical Science Research Institute, St. George’s University of London, London, UK
| | - Normand Leblanc
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
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6
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Tembo M, Bainbridge RE, Lara-Santos C, Komondor KM, Daskivich GJ, Durrant JD, Rosenbaum JC, Carlson AE. Phosphate position is key in mediating transmembrane ion channel TMEM16A-phosphatidylinositol 4,5-bisphosphate interaction. J Biol Chem 2022; 298:102264. [PMID: 35843309 PMCID: PMC9396059 DOI: 10.1016/j.jbc.2022.102264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 07/10/2022] [Accepted: 07/11/2022] [Indexed: 02/07/2023] Open
Abstract
TransMEMbrane 16A (TMEM16A) is a Ca2+-activated Cl- channel that plays critical roles in regulating diverse physiologic processes, including vascular tone, sensory signal transduction, and mucosal secretion. In addition to Ca2+, TMEM16A activation requires the membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). However, the structural determinants mediating this interaction are not clear. Here, we interrogated the parts of the PI(4,5)P2 head group that mediate its interaction with TMEM16A by using patch- and two-electrode voltage-clamp recordings on oocytes from the African clawed frog Xenopus laevis, which endogenously express TMEM16A channels. During continuous application of Ca2+ to excised inside-out patches, we found that TMEM16A-conducted currents decayed shortly after patch excision. Following this rundown, we show that the application of a synthetic PI(4,5)P2 analog produced current recovery. Furthermore, inducible dephosphorylation of PI(4,5)P2 reduces TMEM16A-conducted currents. Application of PIP2 analogs with different phosphate orientations yielded distinct amounts of current recovery, and only lipids that include a phosphate at the 4' position effectively recovered TMEM16A currents. Taken together, these findings improve our understanding of how PI(4,5)P2 binds to and potentiates TMEM16A channels.
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Affiliation(s)
- Maiwase Tembo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Rachel E Bainbridge
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Crystal Lara-Santos
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kayla M Komondor
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Grant J Daskivich
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jacob D Durrant
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Joel C Rosenbaum
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Anne E Carlson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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Pifferi S, Boccaccio A. Ca 2+-Activated Chloride Channels and Phospholipid Scramblases. Int J Mol Sci 2022; 23:ijms23042158. [PMID: 35216275 PMCID: PMC8875746 DOI: 10.3390/ijms23042158] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 01/29/2022] [Indexed: 11/28/2022] Open
Affiliation(s)
- Simone Pifferi
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, 60126 Ancona, Italy
- Correspondence: (S.P.); (A.B.)
| | - Anna Boccaccio
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, 16149 Genova, Italy
- Correspondence: (S.P.); (A.B.)
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Polymodal Control of TMEM16x Channels and Scramblases. Int J Mol Sci 2022; 23:ijms23031580. [PMID: 35163502 PMCID: PMC8835819 DOI: 10.3390/ijms23031580] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 01/20/2022] [Accepted: 01/20/2022] [Indexed: 02/01/2023] Open
Abstract
The TMEM16A/anoctamin-1 calcium-activated chloride channel (CaCC) contributes to a range of vital functions, such as the control of vascular tone and epithelial ion transport. The channel is a founding member of a family of 10 proteins (TMEM16x) with varied functions; some members (i.e., TMEM16A and TMEM16B) serve as CaCCs, while others are lipid scramblases, combine channel and scramblase function, or perform additional cellular roles. TMEM16x proteins are typically activated by agonist-induced Ca2+ release evoked by Gq-protein-coupled receptor (GqPCR) activation; thus, TMEM16x proteins link Ca2+-signalling with cell electrical activity and/or lipid transport. Recent studies demonstrate that a range of other cellular factors—including plasmalemmal lipids, pH, hypoxia, ATP and auxiliary proteins—also control the activity of the TMEM16A channel and its paralogues, suggesting that the TMEM16x proteins are effectively polymodal sensors of cellular homeostasis. Here, we review the molecular pathophysiology, structural biology, and mechanisms of regulation of TMEM16x proteins by multiple cellular factors.
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9
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Calmodulin-Dependent Regulation of Overexpressed but Not Endogenous TMEM16A Expressed in Airway Epithelial Cells. MEMBRANES 2021; 11:membranes11090723. [PMID: 34564540 PMCID: PMC8471323 DOI: 10.3390/membranes11090723] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/16/2021] [Accepted: 09/20/2021] [Indexed: 11/30/2022]
Abstract
Regulation of the Ca2+-activated Cl− channel TMEM16A by Ca2+/calmodulin (CAM) is discussed controversially. In the present study, we compared regulation of TMEM16A by Ca2+/calmodulin (holo-CAM), CAM-dependent kinase (CAMKII), and CAM-dependent phosphatase calcineurin in TMEM16A-overexpressing HEK293 cells and TMEM16A expressed endogenously in airway and colonic epithelial cells. The activator of the Ca2+/CAM-regulated K+ channel KCNN4, 1-EBIO, activated TMEM16A in overexpressing cells, but not in cells with endogenous expression of TMEM16A. Evidence is provided that CAM-interaction with TMEM16A modulates the Ca2+ sensitivity of the Cl− channel. Enhanced Ca2+ sensitivity of overexpressed TMEM16A explains its activity at basal (non-elevated) intracellular Ca2+ levels. The present results correspond well to a recent report that demonstrates a Ca2+-unbound form of CAM (apo-CAM) that is pre-associated with TMEM16A and mediates a Ca2+-dependent sensitization of activation (and inactivation). However, when using activators or inhibitors for holo-CAM, CAMKII, or calcineurin, we were unable to detect a significant impact of CAM, and limit evidence for regulation by CAM-dependent regulatory proteins on receptor-mediated activation of endogenous TMEM16A in airway or colonic epithelial cells. We propose that regulatory properties of TMEM16A and and other members of the TMEM16 family as detected in overexpression studies, should be validated for endogenous TMEM16A and physiological stimuli such as activation of phospholipase C (PLC)-coupled receptors.
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