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Nickerson AJ, Mutchler SM, Sheng S, Cox NA, Ray EC, Kashlan OB, Carattino MD, Marciszyn AL, Winfrey A, Gingras S, Kirabo A, Hughey RP, Kleyman TR. Mice lacking γENaC palmitoylation sites maintain benzamil-sensitive Na+ transport despite reduced channel activity. JCI Insight 2023; 8:e172051. [PMID: 37707951 PMCID: PMC10721255 DOI: 10.1172/jci.insight.172051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/12/2023] [Indexed: 09/16/2023] Open
Abstract
Epithelial Na+ channels (ENaCs) control extracellular fluid volume by facilitating Na+ absorption across transporting epithelia. In vitro studies showed that Cys-palmitoylation of the γENaC subunit is a major regulator of channel activity. We tested whether γ subunit palmitoylation sites are necessary for channel function in vivo by generating mice lacking the palmitoylated cysteines (γC33A,C41A) using CRISPR/Cas9 technology. ENaCs in dissected kidney tubules from γC33A,C41A mice had reduced open probability compared with wild-type (WT) littermates maintained on either standard or Na+-deficient diets. Male mutant mice also had higher aldosterone levels than WT littermates following Na+ restriction. However, γC33A,C41A mice did not have reduced amiloride-sensitive Na+ currents in the distal colon or benzamil-induced natriuresis compared to WT mice. We identified a second, larger conductance cation channel in the distal nephron with biophysical properties distinct from ENaC. The activity of this channel was higher in Na+-restricted γC33A,C41A versus WT mice and was blocked by benzamil, providing a possible compensatory mechanism for reduced prototypic ENaC function. We conclude that γ subunit palmitoylation sites are required for prototypic ENaC activity in vivo but are not necessary for amiloride/benzamil-sensitive Na+ transport in the distal nephron or colon.
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Affiliation(s)
| | | | | | | | | | - Ossama B. Kashlan
- Department of Medicine
- Department of Computational and Systems Biology
| | | | | | | | - Sebastien Gingras
- Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Annet Kirabo
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | | | - Thomas R. Kleyman
- Department of Medicine
- Department of Cell Biology, and
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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2
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Lemmens-Gruber R, Tzotzos S. The Epithelial Sodium Channel-An Underestimated Drug Target. Int J Mol Sci 2023; 24:ijms24097775. [PMID: 37175488 PMCID: PMC10178586 DOI: 10.3390/ijms24097775] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/14/2023] [Accepted: 04/15/2023] [Indexed: 05/15/2023] Open
Abstract
Epithelial sodium channels (ENaC) are part of a complex network of interacting biochemical pathways and as such are involved in several disease states. Dependent on site and type of mutation, gain- or loss-of-function generated symptoms occur which span from asymptomatic to life-threatening disorders such as Liddle syndrome, cystic fibrosis or generalized pseudohypoaldosteronism type 1. Variants of ENaC which are implicated in disease assist further understanding of their molecular mechanisms in order to create models for specific pharmacological targeting. Identification and characterization of ENaC modifiers not only furthers our basic understanding of how these regulatory processes interact, but also enables discovery of new therapeutic targets for the disease conditions caused by ENaC dysfunction. Numerous test compounds have revealed encouraging results in vitro and in animal models but less in clinical settings. The EMA- and FDA-designated orphan drug solnatide is currently being tested in phase 2 clinical trials in the setting of acute respiratory distress syndrome, and the NOX1/ NOX4 inhibitor setanaxib is undergoing clinical phase 2 and 3 trials for therapy of primary biliary cholangitis, liver stiffness, and carcinoma. The established ENaC blocker amiloride is mainly used as an add-on drug in the therapy of resistant hypertension and is being studied in ongoing clinical phase 3 and 4 trials for special applications. This review focuses on discussing some recent developments in the search for novel therapeutic agents.
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Affiliation(s)
- Rosa Lemmens-Gruber
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, A-1090 Vienna, Austria
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3
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The Post-Translational Modification Networking in WNK-Centric Hypertension Regulation and Electrolyte Homeostasis. Biomedicines 2022; 10:biomedicines10092169. [PMID: 36140271 PMCID: PMC9496095 DOI: 10.3390/biomedicines10092169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/26/2022] [Accepted: 08/27/2022] [Indexed: 11/17/2022] Open
Abstract
The with-no-lysine (WNK) kinase family, comprising four serine-threonine protein kinases (WNK1-4), were first linked to hypertension due to their mutations in association with pseudohypoaldosteronism type II (PHAII). WNK kinases regulate crucial blood pressure regulators, SPAK/OSR1, to mediate the post-translational modifications (PTMs) of their downstream ion channel substrates, such as sodium chloride co-transporter (NCC), epithelial sodium chloride (ENaC), renal outer medullary potassium channel (ROMK), and Na/K/2Cl co-transporters (NKCCs). In this review, we summarize the molecular pathways dysregulating the WNKs and their downstream target renal ion transporters. We summarize each of the genetic variants of WNK kinases and the small molecule inhibitors that have been discovered to regulate blood pressure via WNK-triggered PTM cascades.
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Palmitoylation of Voltage-Gated Ion Channels. Int J Mol Sci 2022; 23:ijms23169357. [PMID: 36012639 PMCID: PMC9409123 DOI: 10.3390/ijms23169357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/11/2022] [Accepted: 08/16/2022] [Indexed: 11/30/2022] Open
Abstract
Protein lipidation is one of the most common forms of posttranslational modification. This alteration couples different lipids, such as fatty acids, phospho- and glycolipids and sterols, to cellular proteins. Lipidation regulates different aspects of the protein’s physiology, including structure, stability and affinity for cellular membranes and protein–protein interactions. In this scenario, palmitoylation is the addition of long saturated fatty acid chains to amino acid residues of the proteins. The enzymes responsible for this modification are acyltransferases and thioesterases, which control the protein’s behavior by performing a series of acylation and deacylation cycles. These enzymes target a broad repertoire of substrates, including ion channels. Thus, protein palmitoylation exhibits a pleiotropic role by differential modulation of the trafficking, spatial organization and electrophysiological properties of ion channels. Considering voltage-gated ion channels (VGICs), dysregulation of lipidation of both the channels and the associated ancillary subunits correlates with the development of various diseases, such as cancer or mental disorders. Therefore, a major role for protein palmitoylation is currently emerging, affecting not only the dynamism and differential regulation of a moiety of cellular proteins but also linking to human health. Therefore, palmitoylation of VGIC, as well as related enzymes, constitutes a novel pharmacological tool for drug development to target related pathologies.
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5
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Chuang YC, Chen CC. Force From Filaments: The Role of the Cytoskeleton and Extracellular Matrix in the Gating of Mechanosensitive Channels. Front Cell Dev Biol 2022; 10:886048. [PMID: 35586339 PMCID: PMC9108448 DOI: 10.3389/fcell.2022.886048] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/19/2022] [Indexed: 01/16/2023] Open
Abstract
The senses of proprioception, touch, hearing, and blood pressure on mechanosensitive ion channels that transduce mechanical stimuli with high sensitivity and speed. This conversion process is usually called mechanotransduction. From nematode MEC-4/10 to mammalian PIEZO1/2, mechanosensitive ion channels have evolved into several protein families that use variant gating models to convert different forms of mechanical force into electrical signals. In addition to the model of channel gating by stretching from lipid bilayers, another potent model is the opening of channels by force tethering: a membrane-bound channel is elastically tethered directly or indirectly between the cytoskeleton and the extracellular molecules, and the tethering molecules convey force to change the channel structure into an activation form. In general, the mechanical stimulation forces the extracellular structure to move relative to the cytoskeleton, deforming the most compliant component in the system that serves as a gating spring. Here we review recent studies focusing on the ion channel mechanically activated by a tethering force, the mechanotransduction-involved cytoskeletal protein, and the extracellular matrix. The mechanosensitive channel PIEZO2, DEG/ENaC family proteins such as acid-sensing ion channels, and transient receptor potential family members such as NompC are discussed. State-of-the-art techniques, such as polydimethylsiloxane indentation, the pillar array, and micropipette-guided ultrasound stimulation, which are beneficial tools for exploring the tether model, are also discussed.
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Affiliation(s)
- Yu-Chia Chuang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Chih-Cheng Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- Neuroscience Program of Academia Sinica, Academia Sinica, Taipei, Taiwan
- Taiwan Mouse Clinic, BioTReC, Academia Sinica, Taipei, Taiwan
- *Correspondence: Chih-Cheng Chen,
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6
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Zhang J, Yuan HK, Chen S, Zhang ZR. Detrimental or beneficial: Role of endothelial ENaC in vascular function. J Cell Physiol 2021; 237:29-48. [PMID: 34279047 DOI: 10.1002/jcp.30505] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 12/19/2022]
Abstract
In the past, it was believed that the expression of the epithelial sodium channel (ENaC) was restricted to epithelial tissues, such as the distal nephron, airway, sweat glands, and colon, where it is critical for sodium homeostasis. Over the past two decades, this paradigm has shifted due to the finding that ENaC is also expressed in various nonepithelial tissues, notably in vascular endothelial cells. In this review, the recent findings of the expression, regulation, and function of the endothelial ENaC (EnNaC) are discussed. The expression of EnNaC subunits is reported in a variety of endothelial cell lines and vasculatures, but this is controversial across different species and vessels and is not a universal finding in all vascular beds. The expression density of EnNaC is very faint compared to ENaC in the epithelium. To date, little is known about the regulatory mechanism of EnNaC. Through it can be regulated by aldosterone, the detailed downstream signaling remains elusive. EnNaC responds to increased extracellular sodium with the feedforward activation mechanism, which is quite different from the Na+ self-inhibition mechanism of ENaC. Functionally, EnNaC was shown to be a determinant of cellular mechanics and vascular tone as it can sense shear stress, and its activation or insertion into plasma membrane causes endothelial stiffness and reduced nitric oxide production. However, in some blood vessels, EnNaC is essential for maintaining the integrity of endothelial barrier function. In this context, we discuss the possible reasons for the distinct role of EnNaC in vasculatures.
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Affiliation(s)
- Jun Zhang
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Hui-Kai Yuan
- Department of General Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuo Chen
- Department of Biopharmaceutical Sciences, School of Pharmacy, Harbin Medical University (Daqing), Daqing, China
| | - Zhi-Ren Zhang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang Key Laboratory for Metabolic Disorder & Cancer Related Cardiovascular Diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
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7
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Abstract
The Epithelial Na+ Channel, ENaC, comprised of 3 subunits (αβγ, or sometimes δβγENaC), plays a critical role in regulating salt and fluid homeostasis in the body. It regulates fluid reabsorption into the blood stream from the kidney to control blood volume and pressure, fluid absorption in the lung to control alveolar fluid clearance at birth and maintenance of normal airway surface liquid throughout life, and fluid absorption in the distal colon and other epithelial tissues. Moreover, recent studies have also revealed a role for sodium movement via ENaC in nonepithelial cells/tissues, such as endothelial cells in blood vessels and neurons. Over the past 25 years, major advances have been made in our understanding of ENaC structure, function, regulation, and role in human disease. These include the recently solved three-dimensional structure of ENaC, ENaC function in various tissues, and mutations in ENaC that cause a hereditary form of hypertension (Liddle syndrome), salt-wasting hypotension (PHA1), or polymorphism in ENaC that contributes to other diseases (such as cystic fibrosis). Moreover, great strides have been made in deciphering the regulation of ENaC by hormones (e.g., the mineralocorticoid aldosterone, glucocorticoids, vasopressin), ions (e.g., Na+ ), proteins (e.g., the ubiquitin-protein ligase NEDD4-2, the kinases SGK1, AKT, AMPK, WNKs & mTORC2, and proteases), and posttranslational modifications [e.g., (de)ubiquitylation, glycosylation, phosphorylation, acetylation, palmitoylation]. Characterization of ENaC structure, function, regulation, and role in human disease, including using animal models, are described in this article, with a special emphasis on recent advances in the field. © 2021 American Physiological Society. Compr Physiol 11:1-29, 2021.
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Affiliation(s)
- Daniela Rotin
- The Hospital for Sick Children, and The University of Toronto, Toronto, Canada
| | - Olivier Staub
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
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8
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Mukherjee A, MacDonald KD, Kim J, Henderson MI, Eygeris Y, Sahay G. Engineered mutant α-ENaC subunit mRNA delivered by lipid nanoparticles reduces amiloride currents in cystic fibrosis-based cell and mice models. SCIENCE ADVANCES 2020; 6:6/47/eabc5911. [PMID: 33208364 PMCID: PMC7673816 DOI: 10.1126/sciadv.abc5911] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 10/05/2020] [Indexed: 05/02/2023]
Abstract
Cystic fibrosis (CF) results from mutations in the chloride-conducting CF transmembrane conductance regulator (CFTR) gene. Airway dehydration and impaired mucociliary clearance in CF is proposed to result in tonic epithelial sodium channel (ENaC) activity, which drives amiloride-sensitive electrogenic sodium absorption. Decreasing sodium absorption by inhibiting ENaC can reverse airway surface liquid dehydration. Here, we inhibit endogenous heterotrimeric ENaC channels by introducing inactivating mutant ENaC α mRNA (αmutENaC). Lipid nanoparticles carrying αmutENaC were transfected in CF-based airway cells in vitro and in vivo. We observed a significant decrease in macroscopic as well as amiloride-sensitive ENaC currents and an increase in airway surface liquid height in CF airway cells. Similarly, intranasal transfection of αmutENaC mRNA decreased amiloride-sensitive nasal potential difference in CFTRKO mice. These data suggest that mRNA-based ENaC inhibition is a powerful strategy for reducing mucus dehydration and has therapeutic potential for treating CF in all patients, independent of genotype.
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Affiliation(s)
- Anindit Mukherjee
- Department of Pharmaceutical Sciences, College of Pharmacy, Robertson Life Sciences Building, Oregon State University, Portland, OR 97201, USA
| | - Kelvin D MacDonald
- Department of Pharmaceutical Sciences, College of Pharmacy, Robertson Life Sciences Building, Oregon State University, Portland, OR 97201, USA
- Department of Pediatrics, School of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Jeonghwan Kim
- Department of Pharmaceutical Sciences, College of Pharmacy, Robertson Life Sciences Building, Oregon State University, Portland, OR 97201, USA
| | - Michael I Henderson
- Department of Cell, Developmental and Cancer Biology, Oregon Health & Science University, Portland, OR 97201, USA
| | - Yulia Eygeris
- Department of Pharmaceutical Sciences, College of Pharmacy, Robertson Life Sciences Building, Oregon State University, Portland, OR 97201, USA
| | - Gaurav Sahay
- Department of Pharmaceutical Sciences, College of Pharmacy, Robertson Life Sciences Building, Oregon State University, Portland, OR 97201, USA.
- Department of Biomedical Engineering, Robertson Life Sciences Building, Oregon Health & Science University, Portland, OR 97239, USA
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9
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Abstract
PURPOSE OF REVIEW The main goal of this article is to discuss the role of the epithelial sodium channel (ENaC) in extracellular fluid and blood pressure regulation. RECENT FINDINGS Besides its role in sodium handling in the kidney, recent studies have found that ENaC expressed in other cells including immune cells can influence blood pressure via extra-renal mechanisms. Dendritic cells (DCs) are activated and contribute to salt-sensitive hypertension in an ENaC-dependent manner. We discuss recent studies on how ENaC is regulated in both the kidney and other sites including the vascular smooth muscles, endothelial cells, and immune cells. We also discuss how this extra-renal ENaC can play a role in salt-sensitive hypertension and its promise as a novel therapeutic target. The role of ENaC in blood pressure regulation in the kidney has been well studied. Recent human gene sequencing efforts have identified thousands of variants among the genes encoding ENaC, and research efforts to determine if these variants and their expression in extra-renal tissue play a role in hypertension will advance our understanding of the pathogenesis of ENaC-mediated cardiovascular disease and lead to novel therapeutic targets.
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Affiliation(s)
- Ashley L Pitzer
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, 2215 Garland Avenue, P415C Medical Research Building IV, Nashville, TN, 37232, USA
| | - Justin P Van Beusecum
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, 2215 Garland Avenue, P415C Medical Research Building IV, Nashville, TN, 37232, USA
| | - Thomas R Kleyman
- Departments of Medicine, Cell Biology, Pharmacology, and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Annet Kirabo
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, 2215 Garland Avenue, P415C Medical Research Building IV, Nashville, TN, 37232, USA. .,Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.
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10
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Gorinski N, Wojciechowski D, Guseva D, Abdel Galil D, Mueller FE, Wirth A, Thiemann S, Zeug A, Schmidt S, Zareba-Kozioł M, Wlodarczyk J, Skryabin BV, Glage S, Fischer M, Al-Samir S, Kerkenberg N, Hohoff C, Zhang W, Endeward V, Ponimaskin E. DHHC7-mediated palmitoylation of the accessory protein barttin critically regulates the functions of ClC-K chloride channels. J Biol Chem 2020; 295:5970-5983. [PMID: 32184353 DOI: 10.1074/jbc.ra119.011049] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 03/13/2020] [Indexed: 12/21/2022] Open
Abstract
Barttin is the accessory subunit of the human ClC-K chloride channels, which are expressed in both the kidney and inner ear. Barttin promotes trafficking of the complex it forms with ClC-K to the plasma membrane and is involved in activating this channel. Barttin undergoes post-translational palmitoylation that is essential for its functions, but the enzyme(s) catalyzing this post-translational modification is unknown. Here, we identified zinc finger DHHC-type containing 7 (DHHC7) protein as an important barttin palmitoyl acyltransferase, whose depletion affected barttin palmitoylation and ClC-K-barttin channel activation. We investigated the functional role of barttin palmitoylation in vivo in Zdhhc7 -/- mice. Although palmitoylation of barttin in kidneys of Zdhhc7 -/- animals was significantly decreased, it did not pathologically alter kidney structure and functions under physiological conditions. However, when Zdhhc7 -/- mice were fed a low-salt diet, they developed hyponatremia and mild metabolic alkalosis, symptoms characteristic of human Bartter syndrome (BS) type IV. Of note, we also observed decreased palmitoylation of the disease-causing R8L barttin variant associated with human BS type IV. Our results indicate that dysregulated DHHC7-mediated barttin palmitoylation appears to play an important role in chloride channel dysfunction in certain BS variants, suggesting that targeting DHHC7 activity may offer a potential therapeutic strategy for reducing hypertension.
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Affiliation(s)
- Nataliya Gorinski
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | | | - Daria Guseva
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Dalia Abdel Galil
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Franziska E Mueller
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Alexander Wirth
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Stefan Thiemann
- Institute for Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Andre Zeug
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Silke Schmidt
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Monika Zareba-Kozioł
- Laboratory of Cell Biophysics, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland
| | - Jakub Wlodarczyk
- Laboratory of Cell Biophysics, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland
| | - Boris V Skryabin
- Department of Medicine, Core Facility Transgenic Animal and Genetic Engineering Models (TRAM), University of Münster, 48149 Münster, Germany
| | - Silke Glage
- Institute for Laboratory Animal Science, Hannover Medical School, 30625 Hannover, Germany
| | - Martin Fischer
- Institute for Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Samer Al-Samir
- Institute of Vegetative Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Nicole Kerkenberg
- Department of Psychiatry and Psychotherapy, Laboratory for Molecular Psychiatry, University of Münster, 48149 Münster, Germany; Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, 48149 Münster, Germany
| | - Christa Hohoff
- Department of Psychiatry and Psychotherapy, Laboratory for Molecular Psychiatry, University of Münster, 48149 Münster, Germany
| | - Weiqi Zhang
- Department of Psychiatry and Psychotherapy, Laboratory for Molecular Psychiatry, University of Münster, 48149 Münster, Germany; Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, 48149 Münster, Germany
| | - Volker Endeward
- Institute of Vegetative Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Evgeni Ponimaskin
- Department of Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany.
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11
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Ticho AL, Malhotra P, Manzella CR, Dudeja PK, Saksena S, Gill RK, Alrefai WA. S-acylation modulates the function of the apical sodium-dependent bile acid transporter in human cells. J Biol Chem 2020; 295:4488-4497. [PMID: 32071081 DOI: 10.1074/jbc.ra119.011032] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 02/06/2020] [Indexed: 01/16/2023] Open
Abstract
The ileal apical sodium-dependent bile acid transporter (ASBT) is crucial for the enterohepatic circulation of bile acids. ASBT function is rapidly regulated by several posttranslational modifications. One reversible posttranslational modification is S-acylation, involving the covalent attachment of fatty acids to cysteine residues in proteins. However, whether S-acylation affects ASBT function and membrane expression has not been determined. Using the acyl resin-assisted capture method, we found that the majority of ASBT (∼80%) was S-acylated in ileal brush border membrane vesicles from human organ donors, as well as in HEK293 cells stably transfected with ASBT (2BT cells). Metabolic labeling with alkyne-palmitic acid (100 μm for 15 h) also showed that ASBT is S-acylated in 2BT cells. Incubation with the acyltransferase inhibitor 2-bromopalmitate (25 μm for 15 h) significantly reduced ASBT S-acylation, function, and levels on the plasma membrane. Treatment of 2BT cells with saturated palmitic acid (100 μm for 15 h) increased ASBT function, whereas treatment with unsaturated oleic acid significantly reduced ASBT function. Metabolic labeling with alkyne-oleic acid (100 μm for 15 h) revealed that oleic acid attaches to ASBT, suggesting that unsaturated fatty acids may decrease ASBT's function via a direct covalent interaction with ASBT. We also identified Cys-314 as a potential S-acylation site. In conclusion, these results provide evidence that S-acylation is involved in the modulation of ASBT function. These findings underscore the potential for unsaturated fatty acids to reduce ASBT function, which may be useful in disorders in which bile acid toxicity is implicated.
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Affiliation(s)
- Alexander L Ticho
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332
| | - Pooja Malhotra
- Division of Gastroenterology and Hepatology, Department of Medicine, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332
| | - Christopher R Manzella
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332
| | - Pradeep K Dudeja
- Division of Gastroenterology and Hepatology, Department of Medicine, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332.,Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60612
| | - Seema Saksena
- Division of Gastroenterology and Hepatology, Department of Medicine, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332.,Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60612
| | - Ravinder K Gill
- Division of Gastroenterology and Hepatology, Department of Medicine, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332
| | - Waddah A Alrefai
- Division of Gastroenterology and Hepatology, Department of Medicine, College of Medicine, University of Illinois at Chicago, Illinois 60612-7332 .,Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60612
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12
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Abstract
Epithelial Na+ channels (ENaCs) are members of a family of cation channels that function as sensors of the extracellular environment. ENaCs are activated by specific proteases in the biosynthetic pathway and at the cell surface and remove embedded inhibitory tracts, which allows channels to transition to higher open-probability states. Resolved structures of ENaC and an acid-sensing ion channel revealed highly organized extracellular regions. Within the periphery of ENaC subunits are unique domains formed by antiparallel β-strands containing the inhibitory tracts and protease cleavage sites. ENaCs are inhibited by Na+ binding to specific extracellular site(s), which promotes channel transition to a lower open-probability state. Specific inositol phospholipids and channel modification by Cys-palmitoylation enhance channel open probability. How these regulatory factors interact in a concerted manner to influence channel open probability is an important question that has not been resolved. These various factors are reviewed, and the impact of specific factors on human disorders is discussed.
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Affiliation(s)
- Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, and Departments of Cell Biology and of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Douglas C Eaton
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, Georgia
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13
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Wang XP, Im SJ, Balchak DM, Montalbetti N, Carattino MD, Ray EC, Kashlan OB. Murine epithelial sodium (Na +) channel regulation by biliary factors. J Biol Chem 2019; 294:10182-10193. [PMID: 31092599 PMCID: PMC6664190 DOI: 10.1074/jbc.ra119.007394] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 05/15/2019] [Indexed: 01/01/2023] Open
Abstract
The epithelial sodium channel (ENaC) mediates Na+ transport in several epithelia, including the aldosterone-sensitive distal nephron, distal colon, and biliary epithelium. Numerous factors regulate ENaC activity, including extracellular ligands, post-translational modifications, and membrane-resident lipids. However, ENaC regulation by bile acids and conjugated bilirubin, metabolites that are abundant in the biliary tree and intestinal tract and are sometimes elevated in the urine of individuals with advanced liver disease, remains poorly understood. Here, using a Xenopus oocyte-based system to express and functionally study ENaC, we found that, depending on the bile acid used, bile acids both activate and inhibit mouse ENaC. Whether bile acids were activating or inhibiting was contingent on the position and orientation of specific bile acid moieties. For example, a hydroxyl group at the 12-position and facing the hydrophilic side (12α-OH) was activating. Taurine-conjugated bile acids, which have reduced membrane permeability, affected ENaC activity more strongly than did their more membrane-permeant unconjugated counterparts, suggesting that bile acids regulate ENaC extracellularly. Bile acid-dependent activation was enhanced by amino acid substitutions in ENaC that depress open probability and was precluded by proteolytic cleavage that increases open probability, consistent with an effect of bile acids on ENaC open probability. Bile acids also regulated ENaC in a cortical collecting duct cell line, mirroring the results in Xenopus oocytes. We also show that bilirubin conjugates activate ENaC. These results indicate that ENaC responds to compounds abundant in bile and that their ability to regulate this channel depends on the presence of specific functional groups.
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Affiliation(s)
- Xue-Ping Wang
- From the Renal-Electrolyte Division, Department of Medicine
| | | | | | | | - Marcelo D Carattino
- From the Renal-Electrolyte Division, Department of Medicine
- the Department of Cell Biology and Molecular Physiology, and
| | - Evan C Ray
- From the Renal-Electrolyte Division, Department of Medicine
| | - Ossama B Kashlan
- From the Renal-Electrolyte Division, Department of Medicine,
- the Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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14
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Mutchler SM, Kleyman TR. New insights regarding epithelial Na+ channel regulation and its role in the kidney, immune system and vasculature. Curr Opin Nephrol Hypertens 2019; 28:113-119. [PMID: 30585851 PMCID: PMC6349474 DOI: 10.1097/mnh.0000000000000479] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PURPOSE OF REVIEW This review describes recent findings regarding the epithelial Na channel (ENaC) and its roles in physiologic and pathophysiologic states. We discuss new insights regarding ENaC's structure, its regulation by various factors, its potential role in hypertension and nephrotic syndrome, and its roles in the immune system and vasculature. RECENT FINDINGS A recently resolved structure of ENaC provides clues regarding mechanisms of ENaC activation by proteases. The use of amiloride in nephrotic syndrome, and associated complications are discussed. ENaC is expressed in dendritic cells and contributes to immune system activation and increases in blood pressure in response to NaCl. ENaC is expressed in endothelial ENaC and has a role in regulating vascular tone. SUMMARY New findings have emerged regarding ENaC and its role in the kidney, immune system, and vasculature.
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Affiliation(s)
- Stephanie M. Mutchler
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
| | - Thomas R. Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
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15
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Epithelial sodium channel biogenesis and quality control in the early secretory pathway. Curr Opin Nephrol Hypertens 2018; 27:364-372. [DOI: 10.1097/mnh.0000000000000438] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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16
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Kleyman TR, Kashlan OB, Hughey RP. Epithelial Na + Channel Regulation by Extracellular and Intracellular Factors. Annu Rev Physiol 2017; 80:263-281. [PMID: 29120692 DOI: 10.1146/annurev-physiol-021317-121143] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Epithelial Na+ channels (ENaCs) are members of the ENaC/degenerin family of ion channels that evolved to respond to extracellular factors. In addition to being expressed in the distal aspects of the nephron, where ENaCs couple the absorption of filtered Na+ to K+ secretion, these channels are found in other epithelia as well as nonepithelial tissues. This review addresses mechanisms by which ENaC activity is regulated by extracellular factors, including proteases, Na+, and shear stress. It also addresses other factors, including acidic phospholipids and modification of ENaC cytoplasmic cysteine residues by palmitoylation, which enhance channel activity by altering interactions of the channel with the plasma membrane.
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Affiliation(s)
- Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA; .,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
| | - Ossama B Kashlan
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA; .,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Rebecca P Hughey
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA; .,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, USA
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17
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Rodenburg RNP, Snijder J, van de Waterbeemd M, Schouten A, Granneman J, Heck AJR, Gros P. Stochastic palmitoylation of accessible cysteines in membrane proteins revealed by native mass spectrometry. Nat Commun 2017; 8:1280. [PMID: 29097667 PMCID: PMC5668376 DOI: 10.1038/s41467-017-01461-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 09/19/2017] [Indexed: 01/09/2023] Open
Abstract
Palmitoylation affects membrane partitioning, trafficking and activities of membrane proteins. However, how specificity of palmitoylation and multiple palmitoylations in membrane proteins are determined is not well understood. Here, we profile palmitoylation states of three human claudins, human CD20 and cysteine-engineered prokaryotic KcsA and bacteriorhodopsin by native mass spectrometry. Cysteine scanning of claudin-3, KcsA, and bacteriorhodopsin shows that palmitoylation is independent of a sequence motif. Palmitoylations are observed for cysteines exposed on the protein surface and situated up to 8 Å into the inner leaflet of the membrane. Palmitoylation on multiple sites in claudin-3 and CD20 occurs stochastically, giving rise to a distribution of palmitoylated membrane-protein isoforms. Non-native sites in claudin-3 indicate that membrane-protein function imposed evolutionary restraints on native palmitoylation sites. These results suggest a generic, stochastic membrane-protein palmitoylation process that is determined by the accessibility of palmitoyl-acyl transferases to cysteines on membrane-embedded proteins, and not by a preferred substrate-sequence motif.
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Affiliation(s)
- Remco N P Rodenburg
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Joost Snijder
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Michiel van de Waterbeemd
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Arie Schouten
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Joke Granneman
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands.
| | - Piet Gros
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands.
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18
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Taruno A, Sun H, Nakajo K, Murakami T, Ohsaki Y, Kido MA, Ono F, Marunaka Y. Post-translational palmitoylation controls the voltage gating and lipid raft association of the CALHM1 channel. J Physiol 2017; 595:6121-6145. [PMID: 28734079 DOI: 10.1113/jp274164] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 07/14/2017] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Calcium homeostasis modulator 1 (CALHM1), a new voltage-gated ATP- and Ca2+ -permeable channel, plays important physiological roles in taste perception and memory formation. Regulatory mechanisms of CALHM1 remain unexplored, although the biophysical disparity between CALHM1 gating in vivo and in vitro suggests that there are undiscovered regulatory mechanisms. Here we report that CALHM1 gating and association with lipid microdomains are post-translationally regulated through the process of protein S-palmitoylation, a reversible attachment of palmitate to cysteine residues. Our data also establish cysteine residues and enzymes responsible for CALHM1 palmitoylation. CALHM1 regulation by palmitoylation provides new mechanistic insights into fine-tuning of CALHM1 gating in vivo and suggests a potential layer of regulation in taste and memory. ABSTRACT Emerging roles of CALHM1, a recently discovered voltage-gated ion channel, include purinergic neurotransmission of tastes in taste buds and memory formation in the brain, highlighting its physiological importance. However, the regulatory mechanisms of the CALHM1 channel remain entirely unexplored, hindering full understanding of its contribution in vivo. The different gating properties of CALHM1 in vivo and in vitro suggest undiscovered regulatory mechanisms. Here, in searching for post-translational regulatory mechanisms, we discovered the regulation of CALHM1 gating and association with lipid microdomains via protein S-palmitoylation, the only reversible lipid modification of proteins on cysteine residues. CALHM1 is palmitoylated at two intracellular cysteines located in the juxtamembrane regions of the third and fourth transmembrane domains. Enzymes that catalyse CALHM1 palmitoylation were identified by screening 23 members of the DHHC protein acyltransferase family. Epitope tagging of endogenous CALHM1 proteins in mice revealed that CALHM1 is basally palmitoylated in taste buds in vivo. Functionally, palmitoylation downregulates CALHM1 without effects on its synthesis, degradation and cell surface expression. Mutation of the palmitoylation sites has a profound impact on CALHM1 gating, shifting the conductance-voltage relationship to more negative voltages and accelerating the activation kinetics. The same mutation also reduces CALHM1 association with detergent-resistant membranes. Our results comprehensively uncover a post-translational regulation of the voltage-dependent gating of CALHM1 by palmitoylation.
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Affiliation(s)
- Akiyuki Taruno
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan
| | - Hongxin Sun
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan
| | - Koichi Nakajo
- Department of Physiology, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, 569-8686, Japan
| | - Tatsuro Murakami
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, DK-2200, Copenhagen N, Denmark
| | - Yasuyoshi Ohsaki
- Department of Molecular Cell Biology and Oral Anatomy, Kyushu University, 3-1-1 Maidashi, Higashi-ward, Fukuoka, 812-8582, Japan
| | - Mizuho A Kido
- Department of Anatomy and Physiology, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Fumihito Ono
- Department of Physiology, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, 569-8686, Japan
| | - Yoshinori Marunaka
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan.,Department of Bio-Ionomics, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan
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19
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Mukherjee A, Wang Z, Kinlough CL, Poland PA, Marciszyn AL, Montalbetti N, Carattino MD, Butterworth MB, Kleyman TR, Hughey RP. Specific Palmitoyltransferases Associate with and Activate the Epithelial Sodium Channel. J Biol Chem 2017; 292:4152-4163. [PMID: 28154191 DOI: 10.1074/jbc.m117.776146] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Indexed: 11/06/2022] Open
Abstract
The epithelial sodium channel (ENaC) has an important role in regulating extracellular fluid volume and blood pressure, as well as airway surface liquid volume and mucociliary clearance. ENaC is a trimer of three homologous subunits (α, β, and γ). We previously reported that cytoplasmic residues on the β (βCys-43 and βCys-557) and γ (γCys-33 and γCys-41) subunits are palmitoylated. Mutation of Cys that blocked ENaC palmitoylation also reduced channel open probability. Furthermore, γ subunit palmitoylation had a dominant role over β subunit palmitoylation in regulating ENaC. To determine which palmitoyltransferases (termed DHHCs) regulate the channel, mouse ENaCs were co-expressed in Xenopus oocytes with each of the 23 mouse DHHCs. ENaC activity was significantly increased by DHHCs 1, 2, 3, 7, and 14. ENaC activation by DHHCs was lost when γ subunit palmitoylation sites were mutated, whereas DHHCs 1, 2, and 14 still activated ENaC lacking β subunit palmitoylation sites. β subunit palmitoylation was increased by ENaC co-expression with DHHC 7. Both wild type ENaC and channels lacking β and γ palmitoylation sites co-immunoprecipitated with the five activating DHHCs, suggesting that ENaC forms a complex with multiple DHHCs. RT-PCR revealed that transcripts for the five activating DHHCs were present in cultured mCCDcl1 cells, and DHHC 3 was expressed in aquaporin 2-positive principal cells of mouse aldosterone-sensitive distal nephron where ENaC is localized. Treatment of polarized mCCDcl1 cells with a general inhibitor of palmitoylation reduced ENaC-mediated Na+ currents within minutes. Our results indicate that specific DHHCs have a role in regulating ENaC.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Thomas R Kleyman
- From the Departments of Medicine, .,Cell Biology, and.,Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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20
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Lucas R, Yue Q, Alli A, Duke BJ, Al-Khalili O, Thai TL, Hamacher J, Sridhar S, Lebedyeva I, Su H, Tzotzos S, Fischer B, Gameiro AF, Loose M, Chakraborty T, Shabbir W, Aufy M, Lemmens-Gruber R, Eaton DC, Czikora I. The Lectin-like Domain of TNF Increases ENaC Open Probability through a Novel Site at the Interface between the Second Transmembrane and C-terminal Domains of the α-Subunit. J Biol Chem 2016; 291:23440-23451. [PMID: 27645999 DOI: 10.1074/jbc.m116.718163] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 12/29/2022] Open
Abstract
Regulation of the epithelial sodium channel (ENaC), which regulates fluid homeostasis and blood pressure, is complex and remains incompletely understood. The TIP peptide, a mimic of the lectin-like domain of TNF, activates ENaC by binding to glycosylated residues in the extracellular loop of ENaC-α, as well as to a hitherto uncharacterized internal site. Molecular docking studies suggested three residues, Val567, Glu568, and Glu571, located at the interface between the second transmembrane and C-terminal domains of ENaC-α, as a critical site for binding of the TIP peptide. We generated Ala replacement mutants in this region of ENaC-α and examined its interaction with TIP peptide (3M, V567A/E568A/E571A; 2M, V567A/E568A; and 1M, E571A). 3M and 2M ENaC-α, but not 1M ENaC-α, displayed significantly reduced binding capacity to TIP peptide and to TNF. When overexpressed in H441 cells, 3M mutant ENaC-α formed functional channels with similar gating and density characteristics as the WT subunit and efficiently associated with the β and γ subunits in the plasma membrane. We subsequently assayed for increased open probability time and membrane expression, both of which define ENaC activity, following addition of TIP peptide. TIP peptide increased open probability time in H441 cells overexpressing wild type and 1M ENaC-α channels, but not 3M or 2M ENaC-α channels. On the other hand, TIP peptide-mediated reduction in ENaC ubiquitination was similar in cells overexpressing either WT or 3M ENaC-α subunits. In summary, this study has identified a novel site in ENaC-α that is crucial for activation of the open probability of the channel, but not membrane expression, by the lectin-like domain of TNF.
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Affiliation(s)
- Rudolf Lucas
- From the Vascular Biology Center, .,the Department of Pharmacology and Toxicology, and.,the Division of Pulmonary and Critical Care Medicine, Medical College of Georgia, Augusta, Georgia 30912
| | - Qiang Yue
- the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Abdel Alli
- the Department of Physiology, Emory University, Atlanta, Georgia 30322.,the Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida 32610
| | | | - Otor Al-Khalili
- the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Tiffany L Thai
- the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Jürg Hamacher
- the Department of Pulmonology, Saarland University, D-66421 Homburg, Germany
| | | | - Iryna Lebedyeva
- the Department of Chemistry, Augusta University, Augusta, Georgia 30912
| | - Huabo Su
- From the Vascular Biology Center
| | - Susan Tzotzos
- Apeptico Research and Development, 1150 Vienna, Austria
| | | | | | - Maria Loose
- the Institute for Medical Microbiology, Justus-Liebig University, 35390 Giessen, Germany, and
| | - Trinad Chakraborty
- the Institute for Medical Microbiology, Justus-Liebig University, 35390 Giessen, Germany, and
| | - Waheed Shabbir
- the Department of Pharmacology and Toxicology, University Vienna, 1010 Vienna, Austria
| | - Mohammed Aufy
- the Department of Pharmacology and Toxicology, University Vienna, 1010 Vienna, Austria
| | - Rosa Lemmens-Gruber
- the Department of Pharmacology and Toxicology, University Vienna, 1010 Vienna, Austria
| | - Douglas C Eaton
- the Department of Physiology, Emory University, Atlanta, Georgia 30322,
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21
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Resh MD. Fatty acylation of proteins: The long and the short of it. Prog Lipid Res 2016; 63:120-31. [PMID: 27233110 DOI: 10.1016/j.plipres.2016.05.002] [Citation(s) in RCA: 188] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/19/2016] [Accepted: 05/21/2016] [Indexed: 12/22/2022]
Abstract
Long, short and medium chain fatty acids are covalently attached to hundreds of proteins. Each fatty acid confers distinct biochemical properties, enabling fatty acylation to regulate intracellular trafficking, subcellular localization, protein-protein and protein-lipid interactions. Myristate and palmitate represent the most common fatty acid modifying groups. New insights into how fatty acylation reactions are catalyzed, and how fatty acylation regulates protein structure and function continue to emerge. Myristate is typically linked to an N-terminal glycine, but recent studies reveal that lysines can also be myristoylated. Enzymes that remove N-terminal myristoyl-glycine or myristate from lysines have now been identified. DHHC proteins catalyze S-palmitoylation, but the mechanisms that regulate substrate recognition by individual DHHC family members remain to be determined. New studies continue to reveal thioesterases that remove palmitate from S-acylated proteins. Another area of rapid expansion is fatty acylation of the secreted proteins hedgehog, Wnt and Ghrelin, by Hhat, Porcupine and GOAT, respectively. Understanding how these membrane bound O-acyl transferases recognize their protein and fatty acyl CoA substrates is an active area of investigation, and is punctuated by the finding that these enzymes are potential drug targets in human diseases.
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Affiliation(s)
- Marilyn D Resh
- Cell Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 143, New York, NY 10075, United States.
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22
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Ji HL, Nie HG, Chang Y, Lian Q, Liu SL. CPT-cGMP Is A New Ligand of Epithelial Sodium Channels. Int J Biol Sci 2016; 12:359-66. [PMID: 27019621 PMCID: PMC4807156 DOI: 10.7150/ijbs.13764] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 11/11/2015] [Indexed: 12/28/2022] Open
Abstract
Epithelial sodium channels (ENaC) are localized at the apical membrane of the epithelium, and are responsible for salt and fluid reabsorption. Renal ENaC takes up salt, thereby controlling salt content in serum. Loss-of-function ENaC mutations lead to low blood pressure due to salt-wasting, while gain-of-function mutations cause impaired sodium excretion and subsequent hypertension as well as hypokalemia. ENaC activity is regulated by intracellular and extracellular signals, including hormones, neurotransmitters, protein kinases, and small compounds. Cyclic nucleotides are broadly involved in stimulating protein kinase A and protein kinase G signaling pathways, and, surprisingly, also appear to have a role in regulating ENaC. Increasing evidence suggests that the cGMP analog, CPT-cGMP, activates αβγ-ENaC activity reversibly through an extracellular pathway in a dose-dependent manner. Furthermore, the parachlorophenylthio moiety and ribose 2'-hydroxy group of CPT-cGMP are essential for facilitating the opening of ENaC channels by this compound. Serving as an extracellular ligand, CPT-cGMP eliminates sodium self-inhibition, which is a novel mechanism for stimulating salt reabsorption in parallel to the traditional NO/cGMP/PKG signal pathway. In conclusion, ENaC may be a druggable target for CPT-cGMP, leading to treatments for kidney malfunctions in salt reabsorption.
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Affiliation(s)
- Hong-Long Ji
- 1. Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler, Texas 75708, USA
| | - Hong-Guang Nie
- 2. Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang 110001, China
| | - Yongchang Chang
- 3. Barrow Neurological Institute, St Joseph's Hospital and Medical Center, Phoenix, Arizona, 85013, USA
| | - Qizhou Lian
- 4. Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Shan-Lu Liu
- 5. Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
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23
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Abstract
Protein S-acylation, the reversible covalent fatty-acid modification of cysteine residues, has emerged as a dynamic posttranslational modification (PTM) that controls the diversity, life cycle, and physiological function of numerous ligand- and voltage-gated ion channels. S-acylation is enzymatically mediated by a diverse family of acyltransferases (zDHHCs) and is reversed by acylthioesterases. However, for most ion channels, the dynamics and subcellular localization at which S-acylation and deacylation cycles occur are not known. S-acylation can control the two fundamental determinants of ion channel function: (1) the number of channels resident in a membrane and (2) the activity of the channel at the membrane. It controls the former by regulating channel trafficking and the latter by controlling channel kinetics and modulation by other PTMs. Ion channel function may be modulated by S-acylation of both pore-forming and regulatory subunits as well as through control of adapter, signaling, and scaffolding proteins in ion channel complexes. Importantly, cross-talk of S-acylation with other PTMs of both cysteine residues by themselves and neighboring sites of phosphorylation is an emerging concept in the control of ion channel physiology. In this review, I discuss the fundamentals of protein S-acylation and the tools available to investigate ion channel S-acylation. The mechanisms and role of S-acylation in controlling diverse stages of the ion channel life cycle and its effect on ion channel function are highlighted. Finally, I discuss future goals and challenges for the field to understand both the mechanistic basis for S-acylation control of ion channels and the functional consequence and implications for understanding the physiological function of ion channel S-acylation in health and disease.
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Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD Scotland, UK
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