1
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Zhang S, Meor Azlan NF, Josiah SS, Zhou J, Zhou X, Jie L, Zhang Y, Dai C, Liang D, Li P, Li Z, Wang Z, Wang Y, Ding K, Wang Y, Zhang J. The role of SLC12A family of cation-chloride cotransporters and drug discovery methodologies. J Pharm Anal 2023; 13:1471-1495. [PMID: 38223443 PMCID: PMC10785268 DOI: 10.1016/j.jpha.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 06/20/2023] [Accepted: 09/05/2023] [Indexed: 09/12/2023] Open
Abstract
The solute carrier family 12 (SLC12) of cation-chloride cotransporters (CCCs) comprises potassium chloride cotransporters (KCCs, e.g. KCC1, KCC2, KCC3, and KCC4)-mediated Cl- extrusion, and sodium potassium chloride cotransporters (N[K]CCs, NKCC1, NKCC2, and NCC)-mediated Cl- loading. The CCCs play vital roles in cell volume regulation and ion homeostasis. Gain-of-function or loss-of-function of these ion transporters can cause diseases in many tissues. In recent years, there have been considerable advances in our understanding of CCCs' control mechanisms in cell volume regulations, with many techniques developed in studying the functions and activities of CCCs. Classic approaches to directly measure CCC activity involve assays that measure the transport of potassium substitutes through the CCCs. These techniques include the ammonium pulse technique, radioactive or nonradioactive rubidium ion uptake-assay, and thallium ion-uptake assay. CCCs' activity can also be indirectly observed by measuring γ-aminobutyric acid (GABA) activity with patch-clamp electrophysiology and intracellular chloride concentration with sensitive microelectrodes, radiotracer 36Cl-, and fluorescent dyes. Other techniques include directly looking at kinase regulatory sites phosphorylation, flame photometry, 22Na+ uptake assay, structural biology, molecular modeling, and high-throughput drug screening. This review summarizes the role of CCCs in genetic disorders and cell volume regulation, current methods applied in studying CCCs biology, and compounds developed that directly or indirectly target the CCCs for disease treatments.
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Affiliation(s)
- Shiyao Zhang
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
| | - Nur Farah Meor Azlan
- Institute of Biomedical and Clinical Sciences, Medical School, Faculty of Health and Life Sciences, University of Exeter, Exeter, EX4 4PS, UK
| | - Sunday Solomon Josiah
- Institute of Biomedical and Clinical Sciences, Medical School, Faculty of Health and Life Sciences, University of Exeter, Exeter, EX4 4PS, UK
| | - Jing Zhou
- Department of Neurology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institute of Biological Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Xiaoxia Zhou
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
| | - Lingjun Jie
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
| | - Yanhui Zhang
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
| | - Cuilian Dai
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
| | - Dong Liang
- Aurora Discovery Inc., Foshan, Guangdong, 528300, China
| | - Peifeng Li
- Institute for Translational Medicine, Qingdao University, Qingdao, Shandong, 266021, China
| | - Zhengqiu Li
- School of Pharmacy, Jinan University, Guangzhou, 510632, China
| | - Zhen Wang
- State Key Laboratory of Chemical Biology, Research Center of Chemical Kinomics, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yun Wang
- Department of Neurology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institute of Biological Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Ke Ding
- State Key Laboratory of Chemical Biology, Research Center of Chemical Kinomics, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
| | - Jinwei Zhang
- Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 363001, China
- Institute of Biomedical and Clinical Sciences, Medical School, Faculty of Health and Life Sciences, University of Exeter, Exeter, EX4 4PS, UK
- State Key Laboratory of Chemical Biology, Research Center of Chemical Kinomics, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032, China
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2
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Zhang Y, Li Y, Thompson KN, Stoletov K, Yuan Q, Bera K, Lee SJ, Zhao R, Kiepas A, Wang Y, Mistriotis P, Serra SA, Lewis JD, Valverde MA, Martin SS, Sun SX, Konstantopoulos K. Polarized NHE1 and SWELL1 regulate migration direction, efficiency and metastasis. Nat Commun 2022; 13:6128. [PMID: 36253369 PMCID: PMC9576788 DOI: 10.1038/s41467-022-33683-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 09/26/2022] [Indexed: 12/24/2022] Open
Abstract
Cell migration regulates diverse (patho)physiological processes, including cancer metastasis. According to the Osmotic Engine Model, polarization of NHE1 at the leading edge of confined cells facilitates water uptake, cell protrusion and motility. The physiological relevance of the Osmotic Engine Model and the identity of molecules mediating cell rear shrinkage remain elusive. Here, we demonstrate that NHE1 and SWELL1 preferentially polarize at the cell leading and trailing edges, respectively, mediate cell volume regulation, cell dissemination from spheroids and confined migration. SWELL1 polarization confers migration direction and efficiency, as predicted mathematically and determined experimentally via optogenetic spatiotemporal regulation. Optogenetic RhoA activation at the cell front triggers SWELL1 re-distribution and migration direction reversal in SWELL1-expressing, but not SWELL1-knockdown, cells. Efficient cell reversal also requires Cdc42, which controls NHE1 repolarization. Dual NHE1/SWELL1 knockdown inhibits breast cancer cell extravasation and metastasis in vivo, thereby illustrating the physiological significance of the Osmotic Engine Model.
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Affiliation(s)
- Yuqi Zhang
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Yizeng Li
- grid.264260.40000 0001 2164 4508Department of Biomedical Engineering, Binghamton University, SUNY, Binghamton, NY 13902 USA
| | - Keyata N. Thompson
- grid.411024.20000 0001 2175 4264Marlene and Stewart Greenebaum National Cancer Institute Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Konstantin Stoletov
- grid.17089.370000 0001 2190 316XDepartment of Oncology, University of Alberta, Edmonton, AB T6G 2E1 Canada
| | - Qinling Yuan
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Kaustav Bera
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Se Jong Lee
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Runchen Zhao
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Alexander Kiepas
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Yao Wang
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Panagiotis Mistriotis
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.252546.20000 0001 2297 8753Department of Chemical Engineering, Auburn University, Auburn, AL 36849 USA
| | - Selma A. Serra
- grid.5612.00000 0001 2172 2676Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - John D. Lewis
- grid.17089.370000 0001 2190 316XDepartment of Oncology, University of Alberta, Edmonton, AB T6G 2E1 Canada
| | - Miguel A. Valverde
- grid.5612.00000 0001 2172 2676Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Stuart S. Martin
- grid.411024.20000 0001 2175 4264Marlene and Stewart Greenebaum National Cancer Institute Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201 USA ,grid.411024.20000 0001 2175 4264Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Sean X. Sun
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA
| | - Konstantinos Konstantopoulos
- grid.21107.350000 0001 2171 9311Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Department of Oncology, The Johns Hopkins University, Baltimore, MD 21205 USA
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Cancer as a Channelopathy—Appreciation of Complimentary Pathways Provides a Different Perspective for Developing Treatments. Cancers (Basel) 2022; 14:cancers14194627. [PMID: 36230549 PMCID: PMC9562872 DOI: 10.3390/cancers14194627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 09/17/2022] [Accepted: 09/21/2022] [Indexed: 12/15/2022] Open
Abstract
Simple Summary While improvements in technology have improved our ability to treat many forms of cancer when diagnosed at an early stage of the disease, the ability to improve survival and quality of life for patients with late stage disease has been limited, largely due to the ability of cancer cells to evade destruction when treatments block preferred paths for survival. Here, we review the role that ions and ion channels play in normal cell function, the development of disease and their role in the life and death of a cell. It is hoped that viewing cancer from the perspective of altered ion channel expression and ion balance may provide a novel approach for developing more effective treatments for this devastating disease. Abstract Life depends upon the ability of cells to evaluate and adapt to a constantly changing environment and to maintain internal stability to allow essential biochemical reactions to occur. Ions and ion channels play a crucial role in this process and are essential for survival. Alterations in the expression of the transmembrane proteins responsible for maintaining ion balance that occur as a result of mutations in the genetic code or in response to iatrogenically induced changes in the extracellular environment is a characteristic feature of oncogenesis and identifies cancer as one of a constellation of diseases known as channelopathies. The classification of cancer as a channelopathy provides a different perspective for viewing the disease. Potentially, it may expand opportunities for developing novel ways to affect or reverse the deleterious changes that underlie establishing and sustaining disease and developing tolerance to therapeutic attempts at treatment. The role of ions and ion channels and their interactions in the cell’s ability to maintain ionic balance, homeostasis, and survival are reviewed and possible approaches that mitigate gain or loss of ion channel function to contribute to new or enhance existing cancer therapies are discussed.
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Xia H, Zahra A, Jia M, Wang Q, Wang Y, Campbell SL, Wu J. Na +/H + Exchanger 1, a Potential Therapeutic Drug Target for Cardiac Hypertrophy and Heart Failure. Pharmaceuticals (Basel) 2022; 15:ph15070875. [PMID: 35890170 PMCID: PMC9318128 DOI: 10.3390/ph15070875] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/07/2022] [Accepted: 07/12/2022] [Indexed: 01/27/2023] Open
Abstract
Cardiac hypertrophy is defined as increased heart mass in response to increased hemodynamic requirements. Long-term cardiac hypertrophy, if not counteracted, will ultimately lead to heart failure. The incidence of heart failure is related to myocardial infarction, which could be salvaged by reperfusion and ultimately invites unfavorable myocardial ischemia-reperfusion injury. The Na+/H+ exchangers (NHEs) are membrane transporters that exchange one intracellular proton for one extracellular Na+. The first discovered NHE isoform, NHE1, is expressed almost ubiquitously in all tissues, especially in the myocardium. During myocardial ischemia-reperfusion, NHE1 catalyzes increased uptake of intracellular Na+, which in turn leads to Ca2+ overload and subsequently myocardial injury. Numerous preclinical research has shown that NHE1 is involved in cardiac hypertrophy and heart failure, but the exact molecular mechanisms remain elusive. The objective of this review is to demonstrate the potential role of NHE1 in cardiac hypertrophy and heart failure and investigate the underlying mechanisms.
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Affiliation(s)
- Huiting Xia
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China; (H.X.); (A.Z.)
| | - Aqeela Zahra
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China; (H.X.); (A.Z.)
| | - Meng Jia
- Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China; (M.J.); (Q.W.)
- Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing 100070, China
- National Clinical Research Center for Neurological Disease, Beijing 100070, China
| | - Qun Wang
- Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China; (M.J.); (Q.W.)
- National Clinical Research Center for Neurological Disease, Beijing 100070, China
| | - Yunfu Wang
- Taihe Hospital, Hubei University of Medicine, Shiyan 440070, China;
| | - Susan L. Campbell
- Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA;
| | - Jianping Wu
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China; (H.X.); (A.Z.)
- Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China; (M.J.); (Q.W.)
- Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing 100070, China
- National Clinical Research Center for Neurological Disease, Beijing 100070, China
- Correspondence:
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5
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Diabetes, Heart Failure and Beyond: Elucidating the Cardioprotective Mechanisms of Sodium Glucose Cotransporter 2 (SGLT2) Inhibitors. Am J Cardiovasc Drugs 2022; 22:35-46. [PMID: 34189716 DOI: 10.1007/s40256-021-00486-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/27/2021] [Indexed: 02/07/2023]
Abstract
Approximately 5 million individuals in the US are living with congestive heart failure (CHF), with 650,000 new cases being diagnosed every year. CHF has a multifactorial etiology, ranging from coronary artery disease, hypertension, valvular abnormalities and diabetes mellitus. Currently, guidelines by the American College of Cardiology advocate the use of angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, β-blockers, diuretics, aldosterone antagonists, and inotropes for the medical management of heart failure. The sodium glucose cotransporter 2 (SGLT2) inhibitors are a class of drug that have been widely used in the management of type 2 diabetes mellitus that work by inhibiting the reabsorption of glucose in the proximal convoluted tubule. Since the EMPA-REG OUTCOME trial, several studies have demonstrated the benefits of SGLT2 inhibitors in reducing cardiovascular risk related to heart failure. While the cardiovascular benefits could be explained by their ability to reduce weight, improve glycemic index and lower blood pressure, several recent trials have suggested that SGLT2 inhibitors exhibit pleiotropic effects that underlie their cardioprotective properties. These findings have led to an expansion in preclinical and clinical research aiming to understand the mechanisms by which SGLT2 inhibitors improve heart failure outcomes.
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6
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The Important Role of Ion Transport System in Cervical Cancer. Int J Mol Sci 2021; 23:ijms23010333. [PMID: 35008759 PMCID: PMC8745646 DOI: 10.3390/ijms23010333] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 12/26/2021] [Accepted: 12/27/2021] [Indexed: 12/15/2022] Open
Abstract
Cervical cancer is a significant gynecological cancer and causes cancer-related deaths worldwide. Human papillomavirus (HPV) is implicated in the etiology of cervical malignancy. However, much evidence indicates that HPV infection is a necessary but not sufficient cause in cervical carcinogenesis. Therefore, the cellular pathophysiology of cervical cancer is worthy of study. This review summarizes the recent findings concerning the ion transport processes involved in cell volume regulation and intracellular Ca2+ homeostasis of epithelial cells and how these transport systems are themselves regulated by the tumor microenvironment. For cell volume regulation, we focused on the volume-sensitive Cl− channels and K+-Cl− cotransporter (KCC) family, important regulators for ionic and osmotic homeostasis of epithelial cells. Regarding intracellular Ca2+ homeostasis, the Ca2+ store sensor STIM molecules and plasma membrane Ca2+ channel Orai proteins, the predominant Ca2+ entry mechanism in epithelial cells, are discussed. Furthermore, we evaluate the potential of these membrane ion transport systems as diagnostic biomarkers and pharmacological interventions and highlight the challenges.
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7
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High Na + Salt Diet and Remodeling of Vascular Smooth Muscle and Endothelial Cells. Biomedicines 2021; 9:biomedicines9080883. [PMID: 34440087 PMCID: PMC8389691 DOI: 10.3390/biomedicines9080883] [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: 05/31/2021] [Revised: 07/19/2021] [Accepted: 07/21/2021] [Indexed: 12/12/2022] Open
Abstract
Our knowledge on essential hypertension is vast, and its treatment is well known. Not all hypertensives are salt-sensitive. The available evidence suggests that even normotensive individuals are at high cardiovascular risk and lower survival rate, as blood pressure eventually rises later in life with a high salt diet. In addition, little is known about high sodium (Na+) salt diet-sensitive hypertension. There is no doubt that direct and indirect Na+ transporters, such as the Na/Ca exchanger and the Na/H exchanger, and the Na/K pump could be implicated in the development of high salt-induced hypertension in humans. These mechanisms could be involved following the destruction of the cell membrane glycocalyx and changes in vascular endothelial and smooth muscle cells membranes’ permeability and osmolarity. Thus, it is vital to determine the membrane and intracellular mechanisms implicated in this type of hypertension and its treatment.
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8
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Li Y, Zhou X, Sun SX. Hydrogen, Bicarbonate, and Their Associated Exchangers in Cell Volume Regulation. Front Cell Dev Biol 2021; 9:683686. [PMID: 34249935 PMCID: PMC8264760 DOI: 10.3389/fcell.2021.683686] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 05/31/2021] [Indexed: 11/25/2022] Open
Abstract
Cells lacking a stiff cell wall, e.g., mammalian cells, must actively regulate their volume to maintain proper cell function. On the time scale that protein production is negligible, water flow in and out of the cell determines the cell volume variation. Water flux follows hydraulic and osmotic gradients; the latter is generated by various ion channels, transporters, and pumps in the cell membrane. Compared to the widely studied roles of sodium, potassium, and chloride in cell volume regulation, the effects of proton and bicarbonate are less understood. In this work, we use mathematical models to analyze how proton and bicarbonate, combined with sodium, potassium, chloride, and buffer species, regulate cell volume upon inhibition of ion channels, transporters, and pumps. The model includes several common, widely expressed ion transporters and focuses on obtaining generic outcomes. Results show that the intracellular osmolarity remains almost constant before and after cell volume change. The steady-state cell volume does not depend on water permeability. In addition, to ensure the stability of cell volume and ion concentrations, cells need to develop redundant mechanisms to maintain homeostasis, i.e., multiple ion channels or transporters are involved in the flux of the same ion species. These results provide insights for molecular mechanisms of cell volume regulation with additional implications for water-driven cell migration.
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Affiliation(s)
- Yizeng Li
- Department of Mechanical Engineering, Kennesaw State University, Marietta, GA, United States
| | - Xiaohan Zhou
- Department of Physics, University of Toronto, Toronto, ON, Canada
| | - Sean X. Sun
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, United States
- Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD, United States
- Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, MD, United States
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9
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Winklemann I, Matsuoka R, Meier PF, Shutin D, Zhang C, Orellana L, Sexton R, Landreh M, Robinson CV, Beckstein O, Drew D. Structure and elevator mechanism of the mammalian sodium/proton exchanger NHE9. EMBO J 2020; 39:e105908. [PMID: 33118634 PMCID: PMC7737618 DOI: 10.15252/embj.2020105908] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 09/09/2020] [Accepted: 09/10/2020] [Indexed: 12/21/2022] Open
Abstract
Na+ /H+ exchangers (NHEs) are ancient membrane-bound nanomachines that work to regulate intracellular pH, sodium levels and cell volume. NHE activities contribute to the control of the cell cycle, cell proliferation, cell migration and vesicle trafficking. NHE dysfunction has been linked to many diseases, and they are targets of pharmaceutical drugs. Despite their fundamental importance to cell homeostasis and human physiology, structural information for the mammalian NHE was lacking. Here, we report the cryogenic electron microscopy structure of NHE isoform 9 (SLC9A9) from Equus caballus at 3.2 Å resolution, an endosomal isoform highly expressed in the brain and associated with autism spectrum (ASD) and attention deficit hyperactivity (ADHD) disorders. Despite low sequence identity, the NHE9 architecture and ion-binding site are remarkably similar to distantly related bacterial Na+ /H+ antiporters with 13 transmembrane segments. Collectively, we reveal the conserved architecture of the NHE ion-binding site, their elevator-like structural transitions, the functional implications of autism disease mutations and the role of phosphoinositide lipids to promote homodimerization that, together, have important physiological ramifications.
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Affiliation(s)
- Iven Winklemann
- Department of Biochemistry and BiophysicsStockholm UniversityStockholmSweden
| | - Rei Matsuoka
- Department of Biochemistry and BiophysicsStockholm UniversityStockholmSweden
| | - Pascal F Meier
- Department of Biochemistry and BiophysicsStockholm UniversityStockholmSweden
| | - Denis Shutin
- Department of ChemistryUniversity of OxfordOxfordUK
| | - Chenou Zhang
- Department of PhysicsCenter for Biological PhysicsArizona State UniversityTempeAZUSA
| | - Laura Orellana
- Department of Biochemistry and BiophysicsStockholm UniversityStockholmSweden
| | - Ricky Sexton
- Department of PhysicsCenter for Biological PhysicsArizona State UniversityTempeAZUSA
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell BiologyKarolinska InstituteStockholmSweden
| | | | - Oliver Beckstein
- Department of PhysicsCenter for Biological PhysicsArizona State UniversityTempeAZUSA
| | - David Drew
- Department of Biochemistry and BiophysicsStockholm UniversityStockholmSweden
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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Focal adhesion kinase PTK2 autophosphorylation is not required for the activation of sodium–hydrogen exchange by decreased cell volume in the preimplantation mouse embryo. ZYGOTE 2019; 27:173-179. [DOI: 10.1017/s0967199419000212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
SummaryRecovery from decreased cell volume is accomplished by a regulated increase of intracellular osmolarity. The acute response is activation of inorganic ion transport into the cell, the main effector of which is the Na+/H+ exchanger NHE1. NHE1 is rapidly activated by a cell volume decrease in early embryos, but how this occurs is incompletely understood. Elucidating cell volume-regulatory mechanisms in early embryos is important, as it has been shown that their dysregulation results in preimplantation developmental arrest. The kinase JAK2 has a role in volume-mediated NHE1 activation in at least some cells, including 2-cell stage mouse embryos. However, while 2-cell embryos show partial inhibition of NHE1 when JAK2 activity is blocked, NHE1 activation in 1-cell embryos is JAK2-independent, implying a requirement for additional signalling mechanisms. As focal adhesion kinase (FAK aka PTK2) becomes phosphorylated and activated in some cell types in response to decreased cell volume, we sought to determine whether it was involved in NHE1 activation in the early mouse embryo. FAK activity requires initial autophosphorylation of a tyrosine residue, Y397. However, FAK Y397 phosphorylation levels were not increased in either 1- or 2-cell embryos after cell volume was decreased. Furthermore, the selective FAK inhibitor PF-562271 did not affect NHE1 activation at concentrations that essentially eliminated Y397 phosphorylation. Thus, autophosphorylation of FAK Y397 does not appear to be required for NHE1 activation induced by a decrease in cell volume in early mouse embryos.
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12
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Marcoux AA, Slimani S, Tremblay LE, Frenette-Cotton R, Garneau AP, Isenring P. Regulation of Na +-K +-Cl - cotransporter type 2 by the with no lysine kinase-dependent signaling pathway. Am J Physiol Cell Physiol 2019; 317:C20-C30. [PMID: 30917032 DOI: 10.1152/ajpcell.00041.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Na+-K+-Cl- cotransporter type 2 (NKCC2) is confined to the apical membrane of the thick ascending limb of Henle, where it reabsorbs a substantial fraction of the ultrafiltered NaCl load. It is expressed along this nephron segment as three main splice variants (called NKCC2A, NKCC2B, and NKCC2F) that differ in residue composition along their second transmembrane domain and first intracellular cytosolic connecting segment (CS2). NKCC2 is known to be activated by cell shrinkage and intracellular [Cl-] reduction. Although the with no lysine (WNK) kinases could play a role in this response, the mechanisms involved are ill defined, and the possibility of variant-specific responses has not been tested thus far. In this study, we have used the Xenopus laevis oocyte expression system to gain further insight in these regards. We have found for the first time that cell shrinkage could stimulate NKCC2A- and NKCC2B-mediated ion transport by increasing carrier abundance at the cell surface and that this response was achieved (at least in part) by the enzymatic function of a WNK kinase. Interestingly, we have also found that the activity and cell surface abundance of NKCC2F were less affected by cell shrinkage compared with the other variants and that ion transport by certain variants could be stimulated through WNK kinase expression in the absence of carrier redistribution. Taken together, these results suggest that the WNK kinase-dependent pathway can affect both the trafficking as well as intrinsic activity of NKCC2 and that CS2 plays an important role in carrier regulation.
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Affiliation(s)
- Andrée-Anne Marcoux
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Samira Slimani
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Laurence E Tremblay
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Rachelle Frenette-Cotton
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Alexandre P Garneau
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada.,Cardiometabolic Research Group, Department of Kinesiology, Faculty of Medicine, University of Montreal , Montreal, Quebec , Canada
| | - Paul Isenring
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
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13
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de Los Heros P, Pacheco-Alvarez D, Gamba G. Role of WNK Kinases in the Modulation of Cell Volume. CURRENT TOPICS IN MEMBRANES 2018; 81:207-235. [PMID: 30243433 DOI: 10.1016/bs.ctm.2018.08.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ion Transport across the cell membrane is required to maintain cell volume homeostasis. In response to changes in extracellular osmolarity, most cells activate specific metabolic or membrane-transport pathways to respond to cell swelling or shrinkage and return their volume to its normal resting state. This process involves the rapid adjustment of the activities of channels and transporters that mediate flux of K+, Na+, Cl-, and small organic osmolytes. Cation chloride cotransporters (CCCs) NKCCs and KCCs are a family of membrane proteins modulated by changes in cell volume and/or in the intracellular chloride concentration ([Cl-]i). Cell swelling triggers regulatory volume decrease (RVD), promoting solute and water efflux to restore normal cell volume. Swelling-activated KCCs mediate RVD in most cell types. In contrast, cell shrinkage triggers regulatory volume increase (RVI), which involves the activation of the NKCC1 cotransporter of the CCC family. Regulation of the CCCs during RVI and RVD by protein phosphorylation is a well-characterized mechanism, where WNK kinases and their downstream kinase substrates, SPAK and OSR1 constitute the essential phospho-regulators. WNKs-SPAK/OSR1-CCCs complex is required to regulate cell shrinkage-induced RVI or cell swelling-induced RVD via activating or inhibitory phosphorylation of NKCCs or KCCs, respectively. WNK1 and WNK4 kinases have been established as [Cl-]i sensors/regulators, while a role for WNK3 kinase as a cell volume-sensing kinase has emerged and is proposed in this chapter.
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Affiliation(s)
- Paola de Los Heros
- División de Investigación, Facultad de Medicina, Universidad Nacional Autónoma de México, Coyoacán, Mexico City, Mexico
| | | | - Gerardo Gamba
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, Mexico; Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Tlalpan, Mexico City, Mexico
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14
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Carbajo JM, Maraver F. Salt water and skin interactions: new lines of evidence. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2018; 62:1345-1360. [PMID: 29675710 DOI: 10.1007/s00484-018-1545-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/08/2018] [Accepted: 04/10/2018] [Indexed: 06/08/2023]
Abstract
In Health Resort Medicine, both balneotherapy and thalassotherapy, salt waters and their peloids, or mud products are mainly used to treat rheumatic and skin disorders. These therapeutic agents act jointly via numerous mechanical, thermal, and chemical mechanisms. In this review, we examine a new mechanism of action specific to saline waters. When topically administered, this water rich in sodium and chloride penetrates the skin where it is able to modify cellular osmotic pressure and stimulate nerve receptors in the skin via cell membrane ion channels known as "Piezo" proteins. We describe several models of cutaneous adsorption/desorption and penetration of dissolved ions in mineral waters through the skin (osmosis and cell volume mechanisms in keratinocytes) and examine the role of these resources in stimulating cutaneous nerve receptors. The actions of salt mineral waters are mediated by a mechanism conditioned by the concentration and quality of their salts involving cellular osmosis-mediated activation/inhibition of cell apoptotic or necrotic processes. In turn, this osmotic mechanism modulates the recently described mechanosensitive piezoelectric channels.
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Affiliation(s)
- Jose Manuel Carbajo
- Department of Radiology, Rehabilitation and Physiotherapy, Faculty of Medicine, Universidad Complutense de Madrid, Plaza Ramon y Cajal, s/n, 28040, Madrid, Spain
| | - Francisco Maraver
- Department of Radiology, Rehabilitation and Physiotherapy, Faculty of Medicine, Universidad Complutense de Madrid, Plaza Ramon y Cajal, s/n, 28040, Madrid, Spain.
- Professional School of Medical Hydrology, Faculty of Medicine, Universidad Complutense de Madrid, 28040, Madrid, Spain.
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15
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Shorthouse D, Riedel A, Kerr E, Pedro L, Bihary D, Samarajiwa S, Martins CP, Shields J, Hall BA. Exploring the role of stromal osmoregulation in cancer and disease using executable modelling. Nat Commun 2018; 9:3011. [PMID: 30069015 PMCID: PMC6070494 DOI: 10.1038/s41467-018-05414-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 06/29/2018] [Indexed: 02/07/2023] Open
Abstract
Osmotic regulation is a vital homoeostatic process in all cells and tissues. Cells initially respond to osmotic stresses by activating transmembrane transport proteins to move osmotically active ions. Disruption of ion and water transport is frequently observed in cellular transformations such as cancer. We report that genes involved in membrane transport are significantly deregulated in many cancers, and that their expression can distinguish cancer cells from normal cells with a high degree of accuracy. We present an executable model of osmotic regulation and membrane transport in mammalian cells, providing a mechanistic explanation for phenotype change in varied disease states, and accurately predicting behaviour from single cell expression data. We also predict key proteins involved in cellular transformation, SLC4A3 (AE3), and SLC9A1 (NHE1). Furthermore, we predict and verify a synergistic drug combination in vitro, of sodium and chloride channel inhibitors, which target the osmoregulatory network to reduce cancer-associated phenotypes in fibroblasts.
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Affiliation(s)
- David Shorthouse
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Angela Riedel
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Emma Kerr
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Luisa Pedro
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Dóra Bihary
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Shamith Samarajiwa
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Carla P Martins
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK
| | - Jacqueline Shields
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK.
| | - Benjamin A Hall
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK.
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16
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Cohen BE. Membrane Thickness as a Key Factor Contributing to the Activation of Osmosensors and Essential Ras Signaling Pathways. Front Cell Dev Biol 2018; 6:76. [PMID: 30087894 PMCID: PMC6066546 DOI: 10.3389/fcell.2018.00076] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 06/25/2018] [Indexed: 12/17/2022] Open
Abstract
The cell membrane provides a functional link between the external environment and the replicating DNA genome by using ligand-gated receptors and chemical signals to activate signaling transduction pathways. However, increasing evidence has also indicated that the phospholipid bilayer itself by altering various physical parameters serves as a sensor that regulate membrane proteins in a specific manner. Changes in thickness and/or curvature of the membrane have been shown to be induced by mechanical forces and transmitted through the transmembrane helices of several types of mechanosensitive (MS) ion channels underlying functions such as osmoregulation in bacteria and sensory processing in mammalian cells. This review focus on recent protein functional and structural data indicating that the activation of bacterial and yeast osmosensors is consistent with thickness-induced tilting changes of the transmembrane domains of these proteins. Membrane thinning in combination with curvature changes may also lead to the lateral transfer of the small lipid-anchored GTPases Ras1 and H-Ras out of lipid rafts for clustering and signaling. The modulation of signaling pathways by amphiphilic peptides and the membrane-active antibiotics colistin and Amphotericin B is also discussed.
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Affiliation(s)
- B Eleazar Cohen
- Division of External Activities, National Institute of Allergy and Infectious Diseases, Bethesda, MD, United States
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17
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Ferreira C, Prestin K, Hussner J, Zimmermann U, Meyer Zu Schwabedissen HE. PDZ domain containing protein 1 (PDZK1), a modulator of membrane proteins, is regulated by the nuclear receptor THRβ. Mol Cell Endocrinol 2018; 461:215-225. [PMID: 28928085 DOI: 10.1016/j.mce.2017.09.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 07/25/2017] [Accepted: 09/13/2017] [Indexed: 01/17/2023]
Abstract
Genome wide association studies revealed single nucleotide polymorphisms (SNP) located within the promoter of PDZ domain containing protein 1 (PDZK1) to be associated with serum uric acid levels. Since modulation of transporters and particularly of membrane proteins involved in uric acid handling by PDZK1 has previously been reported, the aim of this study was to analyze the impact of the polymorphisms rs1967017, rs1471633, and rs12129861 on promoter activity and thereby transcription of PDZK1. Cell-based reporter gene assays showed transactivation of the PDZK1-promoter by triiodothyronine mediated by thyroid hormone receptors (THR) α and β. In silico analysis verified localization of the polymorphism rs1967017 within the most likely THR binding site whose deletion reduced THR-mediated transactivation. Furthermore, our study shows regulation of PDZK1 by thyroid hormones, thereby providing a mechanistic basis for the previously reported associations between thyroid hormone status and uric acid homeostasis.
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Affiliation(s)
- Celio Ferreira
- Department of Pharmaceutical Sciences, Biopharmacy, University of Basel, 4056 Basel, Switzerland
| | - Katharina Prestin
- Department of Pharmaceutical Sciences, Biopharmacy, University of Basel, 4056 Basel, Switzerland
| | - Janine Hussner
- Department of Pharmaceutical Sciences, Biopharmacy, University of Basel, 4056 Basel, Switzerland
| | - Uwe Zimmermann
- Clinic for Urology, University Medicine Greifswald, Greifswald, Germany
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18
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Xu B, Zhou C, Meredith M, Baltz JM. Acute cell volume regulation by Janus kinase 2-mediated sodium/hydrogen exchange activation develops at the late one-cell stage in mouse preimplantation embryos. Biol Reprod 2017; 96:542-550. [DOI: 10.1095/biolreprod.116.143974] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 02/02/2017] [Indexed: 01/23/2023] Open
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19
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Pasantes-Morales H. Channels and Volume Changes in the Life and Death of the Cell. Mol Pharmacol 2016; 90:358-70. [PMID: 27358231 DOI: 10.1124/mol.116.104158] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 06/22/2016] [Indexed: 12/11/2022] Open
Abstract
Volume changes deviating from original cell volume represent a major challenge for cellular homeostasis. Cell volume may be altered either by variations in the external osmolarity or by disturbances in the transmembrane ion gradients that generate an osmotic imbalance. Cells respond to anisotonicity-induced volume changes by active regulatory mechanisms that modify the intracellular/extracellular concentrations of K(+), Cl(-), Na(+), and organic osmolytes in the direction necessary to reestablish the osmotic equilibrium. Corrective osmolyte fluxes permeate across channels that have a relevant role in cell volume regulation. Channels also participate as causal actors in necrotic swelling and apoptotic volume decrease. This is an overview of the types of channels involved in either corrective or pathologic changes in cell volume. The review also underlines the contribution of transient receptor potential (TRP) channels, notably TRPV4, in volume regulation after swelling and describes the role of other TRPs in volume changes linked to apoptosis and necrosis. Lastly we discuss findings showing that multimers derived from LRRC8A (leucine-rich repeat containing 8A) gene are structural components of the volume-regulated Cl(-) channel (VRAC), and we underline the intriguing possibility that different heteromer combinations comprise channels with different intrinsic properties that allow permeation of the heterogenous group of molecules acting as organic osmolytes.
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Affiliation(s)
- Herminia Pasantes-Morales
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
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20
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Jentsch TJ. VRACs and other ion channels and transporters in the regulation of cell volume and beyond. Nat Rev Mol Cell Biol 2016; 17:293-307. [PMID: 27033257 DOI: 10.1038/nrm.2016.29] [Citation(s) in RCA: 206] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cells need to regulate their volume to counteract osmotic swelling or shrinkage, as well as during cell division, growth, migration and cell death. Mammalian cells adjust their volume by transporting potassium, sodium, chloride and small organic osmolytes using plasma membrane channels and transporters. This generates osmotic gradients, which drive water in and out of cells. Key players in this process are volume-regulated anion channels (VRACs), the composition of which has recently been identified and shown to encompass LRRC8 heteromers. VRACs also transport metabolites and drugs and function in extracellular signal transduction, apoptosis and anticancer drug resistance.
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Affiliation(s)
- Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
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21
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Yan Y, Shapiro JI. The physiological and clinical importance of sodium potassium ATPase in cardiovascular diseases. Curr Opin Pharmacol 2016; 27:43-9. [PMID: 26891193 PMCID: PMC5161351 DOI: 10.1016/j.coph.2016.01.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 01/14/2016] [Accepted: 01/29/2016] [Indexed: 12/14/2022]
Abstract
The Na/K-ATPase has been extensively studied, but it is only recently that its role as a scaffolding and signaling protein has been identified. It has been identified that cardiotonic steroids (CTS) such as digitalis mediate signal transduction through the Na/K-ATPase in a process found to result in the generation of reactive oxygen species (ROS). As these ROS also appear capable of initiating this signal cascade, a feed forward amplification process has been postulated and subsequently implicated in some disease pathways including uremic cardiomyopathy.
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Affiliation(s)
- Yanling Yan
- Joan C. Edwards School of Medicine, Marshall University, Department of Medicine, USA
| | - Joseph I Shapiro
- Joan C. Edwards School of Medicine, Marshall University, Department of Medicine, USA.
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22
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Son S, Kang JH, Oh S, Kirschner MW, Mitchison TJ, Manalis S. Resonant microchannel volume and mass measurements show that suspended cells swell during mitosis. J Cell Biol 2016; 211:757-63. [PMID: 26598613 PMCID: PMC4657169 DOI: 10.1083/jcb.201505058] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Suspended cells transiently increase their volume during mitosis because of ion exchange through the plasma membrane. Osmotic regulation of intracellular water during mitosis is poorly understood because methods for monitoring relevant cellular physical properties with sufficient precision have been limited. Here we use a suspended microchannel resonator to monitor the volume and density of single cells in suspension with a precision of 1% and 0.03%, respectively. We find that for transformed murine lymphocytic leukemia and mouse pro–B cell lymphoid cell lines, mitotic cells reversibly increase their volume by more than 10% and decrease their density by 0.4% over a 20-min period. This response is correlated with the mitotic cell cycle but is not coupled to nuclear osmolytes released by nuclear envelope breakdown, chromatin condensation, or cytokinesis and does not result from endocytosis of the surrounding fluid. Inhibiting Na-H exchange eliminates the response. Although mitotic rounding of adherent cells is necessary for proper cell division, our observations that suspended cells undergo reversible swelling during mitosis suggest that regulation of intracellular water may be a more general component of mitosis than previously appreciated.
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Affiliation(s)
- Sungmin Son
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Joon Ho Kang
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Seungeun Oh
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Marc W Kirschner
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - T J Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Scott Manalis
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
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23
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Rose KL, Watson AJ, Drysdale TA, Cepinskas G, Chan M, Rupar CA, Fraser DD. Simulated diabetic ketoacidosis therapy in vitro elicits brain cell swelling via sodium-hydrogen exchange and anion transport. Am J Physiol Endocrinol Metab 2015; 309:E370-9. [PMID: 26081282 DOI: 10.1152/ajpendo.00107.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 06/11/2015] [Indexed: 01/08/2023]
Abstract
A common complication of type 1 diabetes mellitus is diabetic ketoacidosis (DKA), a state of severe insulin deficiency. A potentially harmful consequence of DKA therapy in children is cerebral edema (DKA-CE); however, the mechanisms of therapy-induced DKA-CE are unknown. Our aims were to identify the DKA treatment factors and membrane mechanisms that might contribute specifically to brain cell swelling. To this end, DKA was induced in juvenile mice with the administration of the pancreatic toxins streptozocin and alloxan. Brain slices were prepared and exposed to DKA-like conditions in vitro. Cell volume changes were imaged in response to simulated DKA therapy. Our experiments showed that cell swelling was elicited with isolated DKA treatment components, including alkalinization, insulin/alkalinization, and rapid reductions in osmolality. Methyl-isobutyl-amiloride, a nonselective inhibitor of sodium-hydrogen exchangers (NHEs), reduced cell swelling in brain slices elicited with simulated DKA therapy (in vitro) and decreased brain water content in juvenile DKA mice administered insulin and rehydration therapy (in vivo). Specific pharmacological inhibition of the NHE1 isoform with cariporide also inhibited cell swelling, but only in the presence of the anion transport (AT) inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid. DKA did not alter brain NHE1 isoform expression, suggesting that the cell swelling attributed to the NHE1 was activity dependent. In conclusion, our data raise the possibility that brain cell swelling can be elicited by DKA treatment factors and that it is mediated by NHEs and/or coactivation of NHE1 and AT.
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Affiliation(s)
- Keeley L Rose
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada; Children's Health Research Institute, London, Ontario, Canada
| | - Andrew J Watson
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada; Children's Health Research Institute, London, Ontario, Canada
| | - Thomas A Drysdale
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada; Children's Health Research Institute, London, Ontario, Canada; Department of Paediatrics, Western University, London, Ontario, Canada
| | | | - Melissa Chan
- Children's Health Research Institute, London, Ontario, Canada
| | - C Anthony Rupar
- Children's Health Research Institute, London, Ontario, Canada; Department of Paediatrics, Western University, London, Ontario, Canada
| | - Douglas D Fraser
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada; Children's Health Research Institute, London, Ontario, Canada; Centre for Critical Illness Research, London, Ontario, Canada; Department of Paediatrics, Western University, London, Ontario, Canada; Department of Clinical Neurological Sciences, Western University, London, Ontario, Canada; and Translational Research Centre, London, Ontario, Canada
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24
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Singh V, Yang J, Cha B, Chen TE, Sarker R, Yin J, Avula LR, Tse M, Donowitz M. Sorting nexin 27 regulates basal and stimulated brush border trafficking of NHE3. Mol Biol Cell 2015; 26:2030-43. [PMID: 25851603 PMCID: PMC4472014 DOI: 10.1091/mbc.e14-12-1597] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 04/01/2015] [Indexed: 12/21/2022] Open
Abstract
In polarized epithelial cells, SNX27 regulates PDZ domain–directed trafficking of NHE3 from endosomes to the plasma membrane and increases the stability of brush border NHE3. This establishes SNX27 as an important regulator of polarized sorting in epithelial cells. Sorting nexin 27 (SNX27) contains a PDZ domain that is phylogenetically related to the PDZ domains of the NHERF proteins. Studies on nonepithelial cells have shown that this protein is located in endosomes, where it regulates trafficking of cargo proteins in a PDZ domain–dependent manner. However, the role of SNX27 in trafficking of cargo proteins in epithelial cells has not been adequately explored. Here we show that SNX27 directly interacts with NHE3 (C-terminus) primarily through the SNX27 PDZ domain. A combination of knockdown and reconstitution experiments with wild type and a PDZ domain mutant (GYGF → GAGA) of SNX27 demonstrate that the PDZ domain of SNX27 is required to maintain basal NHE3 activity and surface expression of NHE3 in polarized epithelial cells. Biotinylation-based recycling and degradation studies in intestinal epithelial cells show that SNX27 is required for the exocytosis (not endocytosis) of NHE3 from early endosome to plasma membrane. SNX27 is also required to regulate the retention of NHE3 on the plasma membrane. The findings of the present study extend our understanding of PDZ-mediated recycling of cargo proteins from endosome to plasma membrane in epithelial cells.
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Affiliation(s)
- Varsha Singh
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jianbo Yang
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Boyoung Cha
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Tiane-e Chen
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Rafiquel Sarker
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jianyi Yin
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Leela Rani Avula
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ming Tse
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Mark Donowitz
- Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Na+-H+ exchanger-1 (NHE1) regulation in kidney proximal tubule. Cell Mol Life Sci 2015; 72:2061-74. [PMID: 25680790 DOI: 10.1007/s00018-015-1848-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 01/28/2015] [Accepted: 01/29/2015] [Indexed: 01/17/2023]
Abstract
The ubiquitously expressed plasma membrane Na(+)-H(+) exchanger NHE1 is a 12 transmembrane-spanning protein that directs important cell functions such as homeostatic intracellular volume and pH control. The 315 amino acid cytosolic tail of NHE1 binds plasma membrane phospholipids and multiple proteins that regulate additional, ion-translocation independent functions. This review focuses on NHE1 structure/function relationships, as well as the role of NHE1 in kidney proximal tubule functions, including pH regulation, vectorial Na(+) transport, cell volume control and cell survival. The implications of these functions are particularly critical in the setting of progressive, albuminuric kidney diseases, where the accumulation of reabsorbed fatty acids leads to disruption of NHE1-membrane phospholipid interactions and tubular atrophy, which is a poor prognostic factor for progression to end stage renal disease. This review amplifies the vital role of the proximal tubule NHE1 Na(+)-H(+) exchanger as a kidney cell survival factor.
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Sultan A, Luo M, Yu Q, Riederer B, Xia W, Chen M, Lissner S, Gessner JE, Donowitz M, Yun CC, deJonge H, Lamprecht G, Seidler U. Differential association of the Na+/H+ Exchanger Regulatory Factor (NHERF) family of adaptor proteins with the raft- and the non-raft brush border membrane fractions of NHE3. Cell Physiol Biochem 2014; 32:1386-402. [PMID: 24297041 DOI: 10.1159/000356577] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2013] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND/AIMS Trafficking, brush border membrane (BBM) retention, and signal-specific regulation of the Na+/H+ exchanger NHE3 is regulated by the Na+/H+ Exchanger Regulatory Factor (NHERF) family of PDZ-adaptor proteins, which enable the formation of multiprotein complexes. It is unclear, however, what determines signal specificity of these NHERFs. Thus, we studied the association of NHE3, NHERF1 (EBP50), NHERF2 (E3KARP), and NHERF3 (PDZK1) with lipid rafts in murine small intestinal BBM. METHODS Detergent resistant membranes ("lipid rafts") were isolated by floatation of Triton X-incubated small intestinal BBM from a variety of knockout mouse strains in an Optiprep step gradient. Acid-activated NHE3 activity was measured fluorometrically in BCECF-loaded microdissected villi, or by assessment of CO2/HCO3(-) mediated increase in fluid absorption in perfused jejunal loops of anethetized mice. RESULTS NHE3 was found to partially associate with lipid rafts in the native BBM, and NHE3 raft association had an impact on NHE3 transport activity and regulation in vivo. NHERF1, 2 and 3 were differentially distributed to rafts and non-rafts, with NHERF2 being most raft-associated and NHERF3 entirely non-raft associated. NHERF2 expression enhanced the localization of NHE3 to membrane rafts. The use of acid sphingomyelinase-deficient mice, which have altered membrane lipid as well as lipid raft composition, allowed us to test the validity of the lipid raft concept in vivo. CONCLUSIONS The differential association of the NHERFs with the raft-associated and the non-raft fraction of NHE3 in the brush border membrane is one component of the differential and signal-specific NHE3 regulation by the different NHERFs.
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Abstract
PURPOSE To review the history of experimental embryo culture and how culture media that permitted complete preimplantation development in vitro were first discovered, and the physiological insights gained. METHODS This article reviews the history of in vitro mammalian embryo culture, in particular the efforts that led to the current generation of successful culture media and how these reflect embryo physiology, highlighting the contributions of Dr. John D. Biggers and his colleagues and students. RESULTS The culture of mammalian embryos began about a century ago. However, defined media without biological fluids were only developed in the late 1950s, and the first live young born from cultured embryos, using these media, were produced by McLaren and Biggers in 1958. It wasn’t until the late 1980s, however, that preimplantation mammalian embryos could generally be cultured in vitro from fertilized eggs to blastocysts. These new media led to insights into embryo physiology, including the importance of cell volume homeostasis to early embryo viability. CONCLUSIONS The development of successful preimplantation embryo culture media has had a profound effect on assisted reproduction technologies and on research into early embryo physiology.
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Clausell M, Fang Z, Chen W. In vivo study of transepithelial potential difference (TEPD) in proximal convoluted tubules of rat kidney by synchronization modulation electric field. J Membr Biol 2014; 247:601-9. [PMID: 24894719 DOI: 10.1007/s00232-014-9676-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 05/09/2014] [Indexed: 11/30/2022]
Abstract
Synchronization modulation (SM) electric field has been shown to effectively activate function of Na(+)/K(+) pumps in various cells and tissues, including skeletal muscle cells, cardiomyocyte, monolayer of cultured cell line, and peripheral blood vessels. We are now reporting the in vivo studies in application of the SM electric field to kidney of living rats. The field-induced changes in the transepithelial potential difference (TEPD) or the lumen potential from the proximal convoluted tubules were monitored. The results showed that a short time (20 s) application of the SM electric field can significantly increase the magnitude of TEPD from 1-2 mV to about 20 mV. The TEPD is an active potential representing the transport current of the Na/K pumps in epithelial wall of renal tubules. This study showed that SM electric field can increase TEPD by activation of the pump molecules. Considering renal tubules, many active transporters are driven by the Na(+) concentration gradient built by the Na(+)/K(+) pumps, activation of the pump functions and increase in the magnitude of TEPD imply that the SM electric field may improve reabsorption functions of the renal tubules.
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Affiliation(s)
- Mathis Clausell
- Department of Physics, Cellular and Molecular Biophysics Lab, University of South Florida, Tampa, FL, 33620, USA
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Khundmiri SJ, Salyer SA, Farmer B, Qipshidze-Kelm N, Murray RD, Clark BJ, Xie Z, Pressley TA, Lederer ED. Structural determinants for the ouabain-stimulated increase in Na-K ATPase activity. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1089-102. [PMID: 24566089 DOI: 10.1016/j.bbamcr.2014.02.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 02/06/2014] [Accepted: 02/12/2014] [Indexed: 01/11/2023]
Abstract
Recent studies suggest that at low concentrations, ouabain increases Na-K ATPase and NHE1 activity and activates the Src signaling cascade in proximal tubule cells. Our laboratory demonstrated that low concentrations of ouabain increase blood pressure in rats. We hypothesize that ouabain-induced increase in blood pressure and Na-K ATPase activity requires NHE1 activity and association. To test this hypothesis we treated rats with ouabain (1μgkg body wt(-1)day(-1)) for 9days in the presence or absence of the NHE1 inhibitor, zoniporide. Ouabain stimulated a significant increase in blood pressure which was prevented by zoniporide. Using NHE1-expressing Human Kidney cells 2 (HK2), 8 (HK8) and 11 (HK11) and Mouse Kidney cells from Wild type (WT) and NHE1 knock-out mice (SWE) cell lines, we show that ouabain stimulated Na-K ATPase activity and surface expression in a Src-dependent manner in NHE1-expressing cells but not in NHE1-deplete cells. Zoniporide prevented ouabain-induced stimulation of (86)Rb uptake in the NHE1-expressing cells. FRET and TIRF microscopy showed that ouabain increased association between GFP-NHE1 and mCherry-Na-K ATPase transfected into NHE1-deficient SWE cells. Mutational analysis demonstrated that the caveolin binding motif (CBM) of Na-K ATPase α1 is required for translocation of both Na-K ATPase α1 and NHE1 to the basolateral membrane. Mutations in activity or scaffold domains of NHE1 resulted in loss of ouabain-mediated regulation of Na-K ATPase. These results support that NHE1 is required for the ouabain-induced increase in blood pressure, and that the caveolin binding motif of Na-K ATPase α1 as well as the activity and scaffolding domains of NHE1 are required for their functional association.
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Affiliation(s)
- Syed J Khundmiri
- Robley Rex Veterans Affairs Medical Center, Louisville, KY, USA; Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, KY, USA; Department of Physiology, University of Louisville, Louisville, KY, USA.
| | - Sarah A Salyer
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, KY, USA; Department of Physiology, University of Louisville, Louisville, KY, USA
| | - Brandon Farmer
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, KY, USA
| | | | - Rebecca D Murray
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, KY, USA; Department of Physiology, University of Louisville, Louisville, KY, USA
| | - Barbara J Clark
- Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, KY, USA
| | - Zijian Xie
- Department of Physiology, University of Toledo College of Medicine, Toledo, OH, USA
| | - Thomas A Pressley
- Department of Cell Physiology and Molecular Biophysics, Texas Tech Univ. Health Sciences Center, Lubbock, TX, USA
| | - Eleanor D Lederer
- Robley Rex Veterans Affairs Medical Center, Louisville, KY, USA; Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, KY, USA; Department of Physiology, University of Louisville, Louisville, KY, USA
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Hendus-Altenburger R, Kragelund BB, Pedersen SF. Structural dynamics and regulation of the mammalian SLC9A family of Na⁺/H⁺ exchangers. CURRENT TOPICS IN MEMBRANES 2014; 73:69-148. [PMID: 24745981 DOI: 10.1016/b978-0-12-800223-0.00002-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mammalian Na⁺/H⁺ exchangers of the SLC9A family are widely expressed and involved in numerous essential physiological processes. Their primary function is to mediate the 1:1 exchange of Na⁺ for H⁺ across the membrane in which they reside, and they play central roles in regulation of body, cellular, and organellar pH. Their function is tightly regulated through mechanisms involving interactions with multiple protein and lipid-binding partners, phosphorylations, and other posttranslational modifications. Biochemical and mutational analyses indicate that the SLC9As have a short intracellular N-terminus, 12 transmembrane (TM) helices necessary and sufficient for ion transport, and a C-terminal cytoplasmic tail region with essential regulatory roles. No high-resolution structures of the SLC9As exist; however, models based on crystal structures of the bacterial NhaAs support the 12 TM organization and suggest that TMIV and XI may form a central part of the ion-translocation pathway, whereas pH sensing may involve TMII, TMIX, and several intracellular loops. Similar to most ion transporters studied, SLC9As likely exist as coupled dimers in the membrane, and this appears to be important for the well-studied cooperativity of H⁺ binding. The aim of this work is to summarize and critically discuss the currently available evidence on the structural dynamics, regulation, and binding partner interactions of SLC9As, focusing in particular on the most widely studied isoform, SLC9A1/NHE1. Further, novel bioinformatic and structural analyses are provided that to some extent challenge the existing paradigm on how ions are transported by mammalian SLC9As.
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Affiliation(s)
- Ruth Hendus-Altenburger
- Section for Biomolecular Sciences, Department of Biology, University of Copenhagen, Copenhagen, Denmark; Section for Cell and Developmental Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Birthe B Kragelund
- Section for Biomolecular Sciences, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Stine Falsig Pedersen
- Section for Cell and Developmental Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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Hong JH, Park S, Shcheynikov N, Muallem S. Mechanism and synergism in epithelial fluid and electrolyte secretion. Pflugers Arch 2013; 466:1487-99. [PMID: 24240699 DOI: 10.1007/s00424-013-1390-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 10/16/2013] [Accepted: 10/17/2013] [Indexed: 01/04/2023]
Abstract
A central function of epithelia is the control of the volume and electrolyte composition of bodily fluids through vectorial transport of electrolytes and the obligatory H2O. In exocrine glands, fluid and electrolyte secretion is carried out by both acinar and duct cells, with the portion of fluid secreted by each cell type varying among glands. All acinar cells secrete isotonic, plasma-like fluid, while the duct determines the final electrolyte composition of the fluid by absorbing most of the Cl(-) and secreting HCO3 (-). The key transporters mediating acinar fluid and electrolyte secretion are the basolateral Na(+)/K(+) /2Cl(-) cotransporter, the luminal Ca(2+)-activated Cl(-) channel ANO1 and basolateral and luminal Ca(2+)-activated K(+) channels. Ductal fluid and HCO3 (-) secretion are mediated by the basolateral membrane Na(+)-HCO3 (-) cotransporter NBCe1-B and the luminal membrane Cl(-)/HCO3 (-) exchanger slc26a6 and the Cl(-) channel CFTR. The function of the transporters is regulated by multiple inputs, which in the duct include major regulation by the WNK/SPAK pathway that inhibit secretion and the IRBIT/PP1 pathway that antagonize the effects of the WNK/SPAK pathway to both stimulate and coordinate the secretion. The function of these regulatory pathways in secretory glands acinar cells is yet to be examined. An important concept in biology is synergism among signaling pathways to generate the final physiological response that ensures regulation with high fidelity and guards against cell toxicity. While synergism is observed in all epithelial functions, the molecular mechanism mediating the synergism is not known. Recent work reveals a central role for IRBIT as a third messenger that integrates and synergizes the function of the Ca(2+) and cAMP signaling pathways in activation of epithelial fluid and electrolyte secretion. These concepts are discussed in this review using secretion by the pancreatic and salivary gland ducts as model systems.
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Affiliation(s)
- Jeong Hee Hong
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, MD, 20892, USA
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Structural and functional insights into the cardiac Na+/H+ exchanger. J Mol Cell Cardiol 2013; 61:60-7. [DOI: 10.1016/j.yjmcc.2012.11.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 11/26/2012] [Accepted: 11/28/2012] [Indexed: 11/19/2022]
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Zhou C, Fitzharris G, Alper SL, Baltz JM. Na+/H+exchange is inactivated during mouse oocyte meiosis, facilitating glycine accumulation that maintains embryo cell volume. J Cell Physiol 2013; 228:2042-53. [DOI: 10.1002/jcp.24370] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 03/20/2013] [Indexed: 11/07/2022]
Affiliation(s)
| | | | - Seth L. Alper
- Renal Division and Molecular and Vascular Medicine Division, Beth Israel Deaconess Medical Center; Department of Medicine, Harvard Medical School; Boston; Massachusetts
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Alexander RT, Dimke H, Cordat E. Proximal tubular NHEs: sodium, protons and calcium? Am J Physiol Renal Physiol 2013; 305:F229-36. [PMID: 23761670 DOI: 10.1152/ajprenal.00065.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Na⁺/H⁺ exchange activity in the apical membrane of the proximal tubule is fundamental to the reabsorption of Na⁺ and water from the filtrate. The role of this exchange process in bicarbonate reclamation and, consequently, the maintenance of acid-base homeostasis has been appreciated for at least half a century and remains a pillar of renal tubular physiology. More recently, apical Na⁺/H⁺ exchange, mediated by Na⁺/H⁺ exchanger isoform 3 (NHE3), has been implicated in proximal tubular reabsorption of Ca²⁺ and Ca²⁺ homeostasis in general. Overexpression of NHE3 increased paracellular Ca²⁺ flux in a proximal tubular cell model. Consistent with this observation, mice with genetic deletion of Nhe3 have a noticable renal Ca²⁺ leak. These mice also display decreased intestinal Ca²⁺ uptake and osteopenia. This review highlights the traditional roles of proximal tubular Na⁺/H⁺ exchange and summarizes recent novel findings implicating the predominant isoform, NHE3, in Ca²⁺ homeostasis.
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Affiliation(s)
- R Todd Alexander
- Department of Pediatrics, Edmonton Clinic Health Academy, 11405-87 Ave., University of Alberta, Edmonton, AB, Canada T6G 2R7.
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Li HC, Du Z, Barone S, Rubera I, McDonough AA, Tauc M, Zahedi K, Wang T, Soleimani M. Proximal tubule specific knockout of the Na⁺/H⁺ exchanger NHE3: effects on bicarbonate absorption and ammonium excretion. J Mol Med (Berl) 2013; 91:951-63. [PMID: 23508938 PMCID: PMC3730089 DOI: 10.1007/s00109-013-1015-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 01/16/2013] [Accepted: 02/25/2013] [Indexed: 11/17/2022]
Abstract
The existing NHE3 knockout mouse has significant intestinal electrolyte absorption defects, making this model unsuitable for the examination of the role of proximal tubule NHE3 in pathophysiologic states in vivo. To overcome this problem, we generated proximal convoluted tubule-specific KO mice (NHE3-PT KO) by generating and crossing NHE3 floxed mice with the sodium-glucose transporter 2 Cre transgenic mice. The NHE3-PT KO mice have >80 % ablation of NHE3 as determined by immunofluorescence microscopy, western blot, and northern analyses, and show mild metabolic acidosis (serum bicarbonate of 21.2 mEq/l in KO vs. 23.7 mEq/l in WT, p < 0.05). In vitro microperfusion studies in the isolated proximal convoluted tubules demonstrated a ∼36 % reduction in bicarbonate reabsorption (JHCO3 = 53.52 ± 4.61 pmol/min/mm in KO vs. 83.09 ± 9.73 in WT) and a ∼27 % reduction in volume reabsorption (Jv = 0.67 ± 0.07 nl/min/mm in KO vs. 0.92 ± 0.06 nl/min/mm in WT) in mutant mice. The NHE3-PT KO mice tolerated NH4Cl acid load well (added to the drinking water) and showed NH4 excretion rates comparable to WT mice at 2 and 5 days after NH4Cl loading without disproportionate metabolic acidosis after 5 days of acid load. Our results suggest that the Na+/H+ exchanger NHE3 plays an important role in fluid and bicarbonate reabsorption in the proximal convoluted tubule but does not play an important role in NH4 excretion.
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Affiliation(s)
- Hong C Li
- Center on Genetics of Transport and the Department of Medicine, University of Cincinnati, Cincinnati, OH, USA
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Pasham V, Rotte A, Gu S, Yang W, Bhandaru M, Rexhepaj R, Pathare G, Lang F. Upregulation of intestinal NHE3 following saline ingestion. Kidney Blood Press Res 2013; 37:48-57. [PMID: 23548792 DOI: 10.1159/000343401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/19/2013] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Little is known about the effect of salt content of ingested fluid on intestinal transport processes. Osmosensitive genes include the serum- and glucocorticoid-inducible kinase SGK1, which is up-regulated by hyperosmolarity and cell shrinkage. SGK1 is in turn a powerful stimulator of the intestinal Na(+)/H(+) exchanger NHE3. The present study was thus performed to elucidate, whether the NaCl content of beverages influences NHE3 activity. METHODS Mice were offered access to either plain water or isotonic saline ad libitum. NHE3 transcript levels and protein abundance in intestinal tissue were determined by confocal immunofluorescent microscopy, RT-PCR and western blotting, cytosolic pH (pHi) in intestinal cells from 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence and Na(+)/H(+) exchanger activity from the Na(+) dependent realkalinization following an ammonium pulse. RESULTS Saline drinking significantly enhanced fluid intake and increased NHE3 transcript levels, NHE3 protein and Na(+)/H(+) exchanger activity. CONCLUSIONS Salt content of ingested fluid has a profound effect on intestinal Na(+)/H(+) exchanger expression and activity.
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Affiliation(s)
- Venkanna Pasham
- Department of Physiology, University of Tübingen, Tübingen, Germany
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Pasham V, Pathare G, Fajol A, Rexhepaj R, Michael D, Pakladok T, Alesutan I, Rotte A, Föller M, Lang F. OSR1-sensitive small intestinal Na+ transport. Am J Physiol Gastrointest Liver Physiol 2012; 303:G1212-9. [PMID: 23019198 DOI: 10.1152/ajpgi.00367.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The oxidative stress responsive kinase 1 (OSR1) contributes to WNK (with no K)-dependent regulation of renal tubular salt transport, renal salt excretion, and blood pressure. Little is known, however, about a role of OSR1 in the regulation of intestinal salt transport. The present study thus explored whether OSR1 is expressed in intestinal tissue and whether small intestinal Na(+)/H(+) exchanger (NHE), small intestinal Na(+)-glucose cotransport (SGLT1), and/or colonic epithelium Na(+) channel (ENaC) differ between knockin mice carrying one allele of WNK-resistant OSR1 (osr1(+/KI)) and wild-type mice (osr1(+/+)). OSR1 protein abundance was determined by Western blotting, cytosolic pH from BCECF fluorescence, NHE activity from Na(+)-dependent realkalinization following an ammonium pulse, SGLT1 activity from glucose-induced current, and colonic ENaC activity from amiloride-sensitive transepithelial current in Ussing chamber experiments. As a result, OSR1 protein was expressed in small intestine of both osr1(+/KI) mice and osr1(+/+) mice. Daily fecal Na(+), K(+), and H(2)O excretion and jejunal SGLT1 activity were lower, whereas small intestinal NHE activity and colonic ENaC activity were higher in osr1(+/KI) mice than in osr1(+/+) mice. NHE3 inhibitor S-3226 significantly reduced NHE activity in both genotypes but did not abrogate the difference between the genotypes. Plasma osmolarity, serum antidiuretic hormone, plasma aldosterone, and plasma corticosterone concentrations were similar in both genotypes. Small intestinal NHE3 and colonic α-ENaC protein abundance were not significantly different between genotypes, but colonic phospho-β-ENaC (ser633) was significantly higher in osr1(+/KI) mice. In conclusion, OSR1 is expressed in intestine and partial WNK insensitivity of OSR1 increases intestinal NHE activity and colonic ENaC activity.
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Affiliation(s)
- Venkanna Pasham
- Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany
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Baltz JM. Media composition: salts and osmolality. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2012; 912:61-80. [PMID: 22829369 DOI: 10.1007/978-1-61779-971-6_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
The main components of embryo culture media are salts, which dissociate into their component inorganic ions in aqueous solution. All embryo culture media contain the same six inorganic ions: Na(+), K(+), Cl(-), Ca(2+), Mg(2+), and SO(4)(2-), while most also contain PO(4)(2-). The salts that are used to formulate embryo culture media can be traced back to classic saline solutions, particularly Krebs-Ringer Bicarbonate (KRB), that were developed for somatic cells in the first half of the twentieth century. The salt and inorganic ion concentrations in the first successful defined mouse embryo culture medium, Whittens medium, were identical to those in KRB. These remained largely unchanged in embryo culture media for decades, with similar levels found in the standard mouse embryo culture medium, M16, formulated in the 1970s. Human embryos were initially cultured in undefined somatic cell media such as Earles and Hams F-10 with serum added. This changed in the mid-1980s, however, with the development of Quinns HTF, a defined medium specifically formulated for human embryo culture, in which the inorganic ion concentrations are similar to those in M16 and Whittens. While these media were useful both for experimental work and clinically, embryos suffered developmental blocks in all of them, with mouse embryos blocking at the 2-cell stage and human embryos at the 4- to 8-cell stage. Starting in the late 1980s, however, mouse embryo culture media were first developed that alleviated these developmental blocks. These media, CZB and KSOM, had much lower osmolalities than previous media, mainly due to lower inorganic ion concentrations. Indeed, lowering total inorganic ion concentration and osmolality proved key to understanding how media that supported complete preimplantation development in vitro can be formulated. A subsequent improvement was the addition of amino acids to culture media for both mouse and human embryos. At least in part, their beneficial effect during the cleavage stages of development is due to the presence in early preimplantation embryos of mechanisms for cell volume regulation that depend on the accumulation of amino acids as organic osmolytes to provide intracellular osmotic support. These amino acids, principally glycine, replace a portion of the intracellular inorganic ions that would otherwise be needed to maintain cell size, preventing the intracellular ionic strength from rising to deleterious levels and blocking development. Thus, the optimum salts levels, osmolality, and amino acid contents of culture media are not independent, but interact strongly because of their roles in cell volume regulation. In the absence of compounds that preimplantation embryos can use as organic osmolytes, embryos will develop only at lower osmolalities and salt concentrations in the medium. However, when organic osmolytes such as some amino acids are present, embryos will develop in culture at higher osmolarities that are similar to those they experience in tubal fluid in vivo.
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Affiliation(s)
- Jay M Baltz
- Department of Obstetrics and Gynecology, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, ON, Canada.
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Zhou C, Baltz JM. JAK2 mediates the acute response to decreased cell volume in mouse preimplantation embryos by activating NHE1. J Cell Physiol 2012; 228:428-38. [DOI: 10.1002/jcp.24147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Baltz JM, Zhou C. Cell volume regulation in mammalian oocytes and preimplantation embryos. Mol Reprod Dev 2012; 79:821-31. [DOI: 10.1002/mrd.22117] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 09/17/2012] [Indexed: 11/06/2022]
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Lee MG, Ohana E, Park HW, Yang D, Muallem S. Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion. Physiol Rev 2012; 92:39-74. [PMID: 22298651 DOI: 10.1152/physrev.00011.2011] [Citation(s) in RCA: 273] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.
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Affiliation(s)
- Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
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Stewart MP, Toyoda Y, Hyman AA, Muller DJ. Force probing cell shape changes to molecular resolution. Trends Biochem Sci 2011; 36:444-50. [DOI: 10.1016/j.tibs.2011.05.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 04/26/2011] [Accepted: 05/02/2011] [Indexed: 11/25/2022]
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Rabbani I, Siegling-Vlitakis C, Noci B, Martens H. Evidence for NHE3-mediated Na transport in sheep and bovine forestomach. Am J Physiol Regul Integr Comp Physiol 2011; 301:R313-9. [DOI: 10.1152/ajpregu.00580.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Na absorption across the cornified, multilayered, and squamous rumen epithelium is mediated by electrogenic amiloride-insensitive transport and by electroneutral Na transport. High concentrations of amiloride (>100 μM) inhibit Na transport, indicating Na+/H+ exchange (NHE) activity. The underlying NHE isoform for transepithelial Na absorption was characterized by mucosal application of the specific inhibitor HOE642 for NHE1 and S3226 for NHE3 in Ussing chamber studies with isolated epithelia from bovine and sheep forestomach. S3226 (1 μM; NHE3 inhibitor) abolished electroneutral Na transport under control conditions and also the short-chain fatty acid-induced increase of Na transport via NHE. However, HOE642 (30 μM; NHE1 inhibitor) did not change Na transport rates. NHE3 was immunohistochemically localized in membranes of the upper layers toward the lumen. Expression of NHE1 and NHE3 has been previously demonstrated by RT-PCR, and earlier experiments with isolated rumen epithelial cells have shown the activity of both NHE1 and NHE3. Obviously, both isoforms are involved in the regulation of intracellular pH, pHi. However, transepithelial Na transport is only mediated by apical uptake via NHE3 in connection with extrusion of Na by the basolaterally located Na-K-ATPase. The missing involvement of NHE1 in transepithelial Na transport suggests that the proposed “job sharing” in epithelia between these two isoforms probably also applies to forestomach epithelia: NHE3 for transepithelial transport and NHE1 for, among others, pHi and volume regulation.
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Affiliation(s)
- Imtiaz Rabbani
- Institute of Veterinary Physiology, Free University of Berlin, Berlin, Germany
- University of Veterinary & Animal Sciences Lahore, Pakistan; and
| | | | - Bardhyl Noci
- Clinic for Ruminants and Swine, Free University of Berlin, Berlin, Germany
| | - Holger Martens
- Institute of Veterinary Physiology, Free University of Berlin, Berlin, Germany
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Wooden JM, Finney GL, Rynes E, Maccoss MJ, Lambert AJ, Robledo RF, Peters LL, Gilligan DM. Comparative proteomics reveals deficiency of SLC9A1 (sodium/hydrogen exchanger NHE1) in β-adducin null red cells. Br J Haematol 2011; 154:492-501. [PMID: 21689084 DOI: 10.1111/j.1365-2141.2011.08612.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Spherocytosis is one of the most common inherited disorders, yet presents with a wide range of clinical severity. While several genes have been found mutated in patients with spherocytosis, the molecular basis for the variability in severity of haemolytic anaemia is not entirely understood. To identify candidate proteins involved in haemolytic anaemia pathophysiology, we utilized a label-free comparative proteomic approach to detect differences in red blood cells (RBCs) from normal and β-adducin (Add2) knock-out mice. We detected seven proteins that were decreased and 48 proteins that were increased in β-adducin null RBC ghosts. Since haemolytic anaemias are characterized by reticulocytosis, we compared reticulocyte-enriched samples from phenylhydrazine-treated mice with mature RBCs from untreated mice. Among the 48 proteins increased in Add2 knockout RBCs, only 11 were also increased in reticulocytes. Of the proteins decreased in Add2 knockout RBCs, α-adducin showed the greatest intensity difference, followed by SLC9A1, the sodium-hydrogen exchanger previously termed NHE1. We verified these mass spectrometry results by immunoblot. This is the first example of SLC9A1deficiency in haemolytic anaemia and suggests new insights into the mechanisms leading to fragile RBCs.
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Neri EA, Bezerra CNA, Rebouças NA. Essential regulatory elements for NHE3 gene transcription in renal proximal tubule cells. Braz J Med Biol Res 2011; 44:514-23. [PMID: 21537610 DOI: 10.1590/s0100-879x2011007500054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Accepted: 04/11/2011] [Indexed: 11/21/2022] Open
Abstract
The objectives of the present study were to identify the cis-elements of the promoter absolutely required for the efficient rat NHE3 gene transcription and to locate positive and negative regulatory elements in the 5'-flanking sequence (5'FS), which might modulate the gene expression in proximal tubules, and to compare this result to those reported for intestinal cell lines. We analyzed the promoter activity of different 5'FS segments of the rat NHE3 gene, in the OKP renal proximal tubule cell line by measuring the activity of the reporter gene luciferase. Because the segment spanning the first 157 bp of 5'FS was the most active it was studied in more detail by sequential deletions, point mutations, and gel shift assays. The essential elements for gene transcription are in the region -85 to -33, where we can identify consensual binding sites for Sp1 and EGR-1, which are relevant to NHE3 gene basal transcription. Although a low level of transcription is still possible when the first 25 bp of the 5'FS are used as promoter, efficient transcription only occurs with 44 bp of 5'FS. There are negative regulatory elements in the segments spanning -1196 to -889 and -467 to -152, and positive enhancers between -889 and -479 bp of 5'FS. Transcription factors in the OKP cell nuclear extract efficiently bound to DNA elements of rat NHE3 promoter as demonstrated by gel shift assays, suggesting a high level of similarity between transcription factors of both species, including Sp1 and EGR-1.
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Affiliation(s)
- E A Neri
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brazil
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Alexander RT, Jaumouillé V, Yeung T, Furuya W, Peltekova I, Boucher A, Zasloff M, Orlowski J, Grinstein S. Membrane surface charge dictates the structure and function of the epithelial Na+/H+ exchanger. EMBO J 2011; 30:679-91. [PMID: 21245831 DOI: 10.1038/emboj.2010.356] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2010] [Accepted: 12/17/2010] [Indexed: 01/24/2023] Open
Abstract
The Na(+)/H(+) exchanger NHE3 plays a central role in intravascular volume and acid-base homeostasis. Ion exchange activity is conferred by its transmembrane domain, while regulation of the rate of transport by a variety of stimuli is dependent on its cytosolic C-terminal region. Liposome- and cell-based assays employing synthetic or recombinant segments of the cytosolic tail demonstrated preferential association with anionic membranes, which was abrogated by perturbations that interfere with electrostatic interactions. Resonance energy transfer measurements indicated that segments of the C-terminal domain approach the bilayer. In intact cells, neutralization of basic residues in the cytosolic tail by mutagenesis or disruption of electrostatic interactions inhibited Na(+)/H(+) exchange activity. An electrostatic switch model is proposed to account for multiple aspects of the regulation of NHE3 activity.
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Al Moamen NJ, Prasad V, Bodi I, Miller ML, Neiman ML, Lasko VM, Alper SL, Wieczorek DF, Lorenz JN, Shull GE. Loss of the AE3 anion exchanger in a hypertrophic cardiomyopathy model causes rapid decompensation and heart failure. J Mol Cell Cardiol 2010; 50:137-46. [PMID: 21056571 DOI: 10.1016/j.yjmcc.2010.10.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 10/13/2010] [Accepted: 10/24/2010] [Indexed: 02/08/2023]
Abstract
The AE3 Cl(-)/HCO(3)(-) exchanger is abundantly expressed in the sarcolemma of cardiomyocytes, where it mediates Cl(-)-uptake and HCO(3)(-)-extrusion. Inhibition of AE3-mediated Cl(-)/HCO(3)(-) exchange has been suggested to protect against cardiac hypertrophy; however, other studies indicate that AE3 might be necessary for optimal cardiac function. To test these hypotheses we crossed AE3-null mice, which appear phenotypically normal, with a hypertrophic cardiomyopathy mouse model carrying a Glu180Gly mutation in α-tropomyosin (TM180). Loss of AE3 had no effect on hypertrophy; however, survival of TM180/AE3 double mutants was sharply reduced compared with TM180 single mutants. Analysis of cardiac performance revealed impaired cardiac function in TM180 and TM180/AE3 mutants. TM180/AE3 double mutants were more severely affected and exhibited little response to β-adrenergic stimulation, a likely consequence of their more rapid progression to heart failure. Increased expression of calmodulin-dependent kinase II and protein phosphatase 1 and differences in methylation and localization of protein phosphatase 2A were observed, but were similar in single and double mutants. Phosphorylation of phospholamban on Ser16 was sharply increased in both single and double mutants relative to wild-type hearts under basal conditions, leading to reduced reserve capacity for β-adrenergic stimulation of phospholamban phosphorylation. Imaging analysis of isolated myocytes revealed reductions in amplitude and decay of Ca(2+) transients in both mutants, with greater reductions in TM180/AE3 mutants, consistent with the greater severity of their heart failure phenotype. Thus, in the TM180 cardiomyopathy model, loss of AE3 had no apparent anti-hypertrophic effect and led to more rapid decompensation and heart failure.
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Affiliation(s)
- Nabeel J Al Moamen
- Department of Molecular Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
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Schiller KR, Maniak PJ, O'Grady SM. Cystic fibrosis transmembrane conductance regulator is involved in airway epithelial wound repair. Am J Physiol Cell Physiol 2010; 299:C912-21. [PMID: 20686068 DOI: 10.1152/ajpcell.00215.2010] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The role of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) in airway epithelial wound repair was investigated using normal human bronchial epithelial (NHBE) cells and a human airway epithelial cell line (Calu-3) of serous gland origin. Measurements of wound repair were performed using continuous impedance sensing to determine the time course for wound closure. Control experiments showed that the increase in impedance corresponding to cell migration into the wound was blocked by treatment with the actin polymerization inhibitor, cytochalasin D. Time lapse imaging revealed that NHBE and Calu-3 cell wound closure was dependent on cell migration, and that movement occurred as a collective sheet of cells. Selective inhibition of CFTR activity with CFTR(inh)-172 or short hairpin RNA silencing of CFTR expression produced a significant delay in wound repair. The CF cell line UNCCF1T also exhibited significantly slower migration than comparable normal airway epithelial cells. Inhibition of CFTR-dependent anion transport by treatment with CFTR(inh)-172 slowed wound closure to the same extent as silencing CFTR protein expression, indicating that ion transport by CFTR plays a critical role in migration. Moreover, morphologic analysis of migrating cells revealed that CFTR inhibition or silencing significantly reduced lamellipodia protrusion. These findings support the conclusion that CFTR participates in airway epithelial wound repair by a mechanism involving anion transport that is coupled to the regulation of lamellipodia protrusion at the leading edge of the cell.
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Affiliation(s)
- Katherine R Schiller
- Graduate Program in Comparative Molecular Biosciences, University of Minnesota, St. Paul, Minnesota 55108, USA
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Cha B, Zhu XC, Chen W, Jones M, Ryoo S, Zachos NC, Chen TE, Lin R, Sarker R, Kenworthy AK, Tse M, Kovbasnjuk O, Donowitz M. NHE3 mobility in brush borders increases upon NHERF2-dependent stimulation by lyophosphatidic acid. J Cell Sci 2010; 123:2434-43. [PMID: 20571054 DOI: 10.1242/jcs.056713] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The epithelial brush border (BB) Na(+)/H(+) exchanger NHE3 is associated with the actin cytoskeleton by binding both directly and indirectly to ezrin; indirect binding is via attachment to NHERF family proteins. NHE3 mobility in polarized epithelial cell BBs is restricted by the actin cytoskeleton and NHERF binding such that only approximately 30% of NHE3 in the apical domain of an OK cell line stably expressing NHERF2 is mobile, as judged by FRAP analysis. Given that levels of NHE3 are partially regulated by changes in trafficking, we investigated whether the cytoskeleton association of NHE3 was dynamic and changed as part of acute regulation to allow NHE3 trafficking. The agonist studied was lysophosphatidic acid (LPA), an inflammatory mediator, which acutely stimulates NHE3 activity by increasing the amount of NHE3 on the BBs by stimulated exocytosis. LPA acutely stimulated NHE3 activity in OK cells stably expressing NHERF2. Two conditions that totally prevented LPA stimulation of NHE3 activity only partially prevented stimulation of NHE3 mobility: the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, and the NHE3F1 double mutant which has minimal direct binding of NHE3 to ezrin. These results show that LPA stimulation of NHE3 mobility occurs in two parts: (1) PI3K-dependent exocytic trafficking to the BB and (2) an increase in surface mobility of NHE3 in BBs under basal conditions. Moreover, the LPA stimulatory effect on NHE3 mobility required NHERF2. Although NHE3 and NHERF2 co-precipitated under basal conditions, they failed to co-precipitate 30 minutes after addition of LPA, whereas the physical association was re-established by 50-60 minutes. This dynamic interaction between NHERF2 and NHE3 was confirmed by acceptor photobleaching Förster Resonance energy Transfer (FRET). The restricted mobility of NHE3 in BBs under basal conditions as a result of cytoskeleton association is therefore dynamic and is reversed as part of acute LPA stimulation of NHE3. We suggest that this acute but transient increase in NHE3 mobility induced by LPA occurs via two processes: addition of NHE3 to the BB by exocytosis, a process which precedes binding of NHE3 to the actin cytoskeleton via NHERF2-ezrin, and by release of NHERF2 from the NHE3 already localized in the apical membrane, enabling NHE3 to distribute throughout the microvilli. These fractions of NHE3 make up a newly identified pool of NHE3 called the 'transit pool'. Moreover, our results show that there are two aspects of LPA signaling involved in stimulation of NHE3 activity: PI3K-dependent stimulated NHE3 exocytosis and the newly described, PI3K-independent dissociation of microvillar NHE3 from NHERF2.
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Affiliation(s)
- Boyoung Cha
- Departments of Physiology and Medicine, Gastroenterology Division, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 212052, USA
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Gawenis LR, Bradford EM, Alper SL, Prasad V, Shull GE. AE2 Cl-/HCO3- exchanger is required for normal cAMP-stimulated anion secretion in murine proximal colon. Am J Physiol Gastrointest Liver Physiol 2010; 298:G493-503. [PMID: 20110461 PMCID: PMC2853300 DOI: 10.1152/ajpgi.00178.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Anion secretion by colonic epithelium is dependent on apical CFTR-mediated anion conductance and basolateral ion transport. In many tissues, the NKCC1 Na(+)-K(+)-2Cl(-) cotransporter mediates basolateral Cl(-) uptake. However, additional evidence suggests that the AE2 Cl(-)/HCO(3)(-) exchanger, when coupled with the NHE1 Na(+)/H(+) exchanger or a Na(+)-HCO(3)(-) cotransporter (NBC), contributes to HCO(3)(-) and/or Cl(-) uptake. To analyze the secretory functions of AE2 in proximal colon, short-circuit current (I(sc)) responses to cAMP and inhibitors of basolateral anion transporters were measured in muscle-stripped wild-type (WT) and AE2-null (AE2(-/-)) proximal colon. In physiological Ringer, the magnitude of cAMP-stimulated I(sc) was the same in WT and AE2(-/-) colon. However, the I(sc) response in AE2(-/-) colon exhibited increased sensitivity to the NKCC1 inhibitor bumetanide and decreased sensitivity to the distilbene derivative SITS (which inhibits AE2 and some NBCs), indicating that loss of AE2 results in a switch to increased NKCC1-supported anion secretion. Removal of HCO(3)(-) resulted in robust cAMP-stimulated I(sc) in both AE2(-/-) and WT colon that was largely mediated by NKCC1, whereas removal of Cl(-) resulted in sharply decreased cAMP-stimulated I(sc) in AE2(-/-) colon relative to WT controls. Inhibition of NHE1 had no effect on cAMP-stimulated I(sc) in AE2(-/-) colon but caused a switch to NKCC1-supported secretion in WT colon. Thus, in AE2(-/-) colon, Cl(-) secretion supported by basolateral NKCC1 is enhanced, whereas HCO(3)(-) secretion is diminished. These results show that AE2 is a component of the basolateral ion transport mechanisms that support anion secretion in the proximal colon.
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Affiliation(s)
- Lara R. Gawenis
- 1Department of Physiology, University of Utah, Salt Lake City, Utah;
| | - Emily M. Bradford
- 2Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio; and
| | - Seth L. Alper
- 3Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Vikram Prasad
- 2Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio; and
| | - Gary E. Shull
- 2Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio; and
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