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Gamba G. Thirty years of the NaCl cotransporter: from cloning to physiology and structure. Am J Physiol Renal Physiol 2023; 325:F479-F490. [PMID: 37560773 PMCID: PMC10639029 DOI: 10.1152/ajprenal.00114.2023] [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: 05/02/2023] [Revised: 08/08/2023] [Accepted: 08/08/2023] [Indexed: 08/11/2023] Open
Abstract
The primary structure of the thiazide-sensitive NaCl cotransporter (NCC) was resolved 30 years ago by the molecular identification of the cDNA encoding this cotransporter, from the winter's flounder urinary bladder, following a functional expression strategy. This review outlines some aspects of how the knowledge about thiazide diuretics and NCC evolved, the history of the cloning process, and the expansion of the SLC12 family of electroneutral cotransporters. The diseases associated with activation or inactivation of NCC are discussed, as well as the molecular model by which the activity of NCC is regulated. The controversies in the field are discussed as well as recent publication of the three-dimensional model of NCC obtained by cryo-electron microscopy, revealing not only the amino acid residues critical for Na+ and Cl- translocation but also the residues critical for polythiazide binding to the transporter, opening the possibility for a new era in thiazide diuretic therapy.
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Affiliation(s)
- Gerardo Gamba
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
- Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
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2
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Kettritz R, Loffing J. Potassium homeostasis - Physiology and pharmacology in a clinical context. Pharmacol Ther 2023; 249:108489. [PMID: 37454737 DOI: 10.1016/j.pharmthera.2023.108489] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 07/03/2023] [Accepted: 07/06/2023] [Indexed: 07/18/2023]
Abstract
Membrane voltage controls the function of excitable cells and is mainly a consequence of the ratio between the extra- and intracellular potassium concentration. Potassium homeostasis is safeguarded by balancing the extra-/intracellular distribution and systemic elimination of potassium to the dietary potassium intake. These processes adjust the plasma potassium concentration between 3.5 and 4.5 mmol/L. Several genetic and acquired diseases but also pharmacological interventions cause dyskalemias that are associated with increased morbidity and mortality. The thresholds at which serum K+ not only associates but also causes increased mortality are hotly debated. We discuss physiologic, pathophysiologic, and pharmacologic aspects of potassium regulation and provide informative case vignettes. Our aim is to help clinicians, epidemiologists, and pharmacologists to understand the complexity of the potassium homeostasis in health and disease and to initiate appropriate treatment strategies in dyskalemic patients.
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Affiliation(s)
- Ralph Kettritz
- Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; Experimental and Clinical Research Center, Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité Universitätsmedizin Berlin, Germany.
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Koulouridis I, Koulouridis E. The Integral Role of Chloride & With-No-Lysine Kinases in Cell Volume Regulation & Hypertension. Int J Nephrol Renovasc Dis 2023; 16:183-196. [PMID: 37601040 PMCID: PMC10438449 DOI: 10.2147/ijnrd.s417766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 07/28/2023] [Indexed: 08/22/2023] Open
Abstract
Chloride anions are the most abundant in humans. For many years, it has been believed that chloride is simply a counterion of all other cations, ensuring the electroneutrality of the extracellular space. Recent data suggests that chloride anions possess a broad spectrum of important activities that regulate vital cellular functions. It is now evident that, apart from its contribution to the electroneutrality of the extracellular space, it acts as an osmole and contributes to extracellular and intracellular volume regulation. Its anionic charge also contributes to the generation of cell membrane potential. The most interesting action of chloride anions is their ability to regulate the activity of with-no-lysine kinases, which in turn regulate the activity of sodium chloride and potassium chloride cotransporters and govern the reabsorption of salt and excretion of potassium by nephron epithelia. Chloride anions seem to play a crucial role in cell functions, such as cell volume regulation, sodium reabsorption in the distal nephron, potassium balance, and sodium sensitivity, which lead to hypertension. All of these functions are accomplished on a molecular level via complicated metabolic pathways, many of which remain poorly defined. We attempted to elucidate some of these pathways in light of recent advances in our knowledge, obtained mainly from experimental studies.
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Wang T, Liu T, Xu S, Frindt G, Weinstein AM, Palmer LG. High dietary K + intake inhibits proximal tubule transport. Am J Physiol Renal Physiol 2023; 325:F224-F234. [PMID: 37318989 PMCID: PMC10396284 DOI: 10.1152/ajprenal.00013.2023] [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: 01/27/2023] [Revised: 05/15/2023] [Accepted: 06/14/2023] [Indexed: 06/17/2023] Open
Abstract
The impact of chronic dietary K+ loading on proximal tubule (PT) function was measured using free-flow micropuncture along with measurements of overall kidney function, including urine volume, glomerular filtration rate, and absolute and fractional Na+ and K+ excretion in the rat. Feeding animals a diet with 5% KCl [high K+ (HK)] for 7 days reduced glomerular filtration rate by 29%, increased urine volume by 77%, and increased absolute K+ excretion by 202% compared with rats on a 1% KCl [control K+ (CK)] diet. HK did not change absolute Na+ excretion but significantly increased fraction excretion of Na+ (1.40% vs. 0.64%), indicating that fractional Na+ absorption is reduced by HK. PT reabsorption was assessed using free-flow micropuncture in anesthetized animals. At 80% of the accessible length of the PT, measurements of inulin concentration indicated volume reabsorption of 73% and 54% in CK and HK, respectively. At the same site, fractional PT Na+ reabsorption was 66% in CK animals and 37% in HK animals. Fractional PT K+ reabsorption was 66% in CK and 37% in HK. To assess the role of Na+/H+ exchanger isoform 3 (NHE3) in mediating these changes, we measured NHE3 protein expression in total kidney microsomes as well as surface membranes using Western blots. We found no significant changes in protein in either cell fraction. Expression of the Ser552 phosphorylated form of NHE3 was also similar in CK and HK animals. Reduction in PT transport may facilitate K+ excretion and help balance Na+ excretion by shifting Na+ reabsorption from K+-reabsorbing to K+-secreting nephron segments.NEW & NOTEWORTHY In rats fed a diet rich in K+, proximal tubules reabsorbed less fluid, Na+, and K+ compared with those in animals on a control diet. Glomerular filtration rates also decreased, probably due to glomerulotubular feedback. These reductions may help to maintain balance of the two ions simultaneously by shifting Na+ reabsorption to K+-secreting nephron segments.
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Affiliation(s)
- Tong Wang
- Department of Molecular and Cellular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Tommy Liu
- Department of Molecular and Cellular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Shuhua Xu
- Department of Molecular and Cellular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medicine, New York, New York, United States
| | - Alan M Weinstein
- Department of Physiology and Biophysics, Weill-Cornell Medicine, New York, New York, United States
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medicine, New York, New York, United States
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Saha B, Shabbir W, Takagi E, Duan XP, Leite Dellova DCA, Demko J, Manis A, Loffing-Cueni D, Loffing J, Sørensen MV, Wang WH, Pearce D. Potassium Activates mTORC2-dependent SGK1 Phosphorylation to Stimulate Epithelial Sodium Channel: Role in Rapid Renal Responses to Dietary Potassium. J Am Soc Nephrol 2023; 34:1019-1038. [PMID: 36890646 PMCID: PMC10278851 DOI: 10.1681/asn.0000000000000109] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 02/06/2023] [Indexed: 03/10/2023] Open
Abstract
SIGNIFICANCE STATEMENT Rapid renal responses to ingested potassium are essential to prevent hyperkalemia and also play a central role in blood pressure regulation. Although local extracellular K + concentration in kidney tissue is increasingly recognized as an important regulator of K + secretion, the underlying mechanisms that are relevant in vivo remain controversial. To assess the role of the signaling kinase mTOR complex-2 (mTORC2), the authors compared the effects of K + administered by gavage in wild-type mice and knockout mice with kidney tubule-specific inactivation of mTORC2. They found that mTORC2 is rapidly activated to trigger K + secretion and maintain electrolyte homeostasis. Downstream targets of mTORC2 implicated in epithelial sodium channel regulation (SGK1 and Nedd4-2) were concomitantly phosphorylated in wild-type, but not knockout, mice. These findings offer insight into electrolyte physiologic and regulatory mechanisms. BACKGROUND Increasing evidence implicates the signaling kinase mTOR complex-2 (mTORC2) in rapid renal responses to changes in plasma potassium concentration [K + ]. However, the underlying cellular and molecular mechanisms that are relevant in vivo for these responses remain controversial. METHODS We used Cre-Lox-mediated knockout of rapamycin-insensitive companion of TOR (Rictor) to inactivate mTORC2 in kidney tubule cells of mice. In a series of time-course experiments in wild-type and knockout mice, we assessed urinary and blood parameters and renal expression and activity of signaling molecules and transport proteins after a K + load by gavage. RESULTS A K + load rapidly stimulated epithelial sodium channel (ENaC) processing, plasma membrane localization, and activity in wild-type, but not in knockout, mice. Downstream targets of mTORC2 implicated in ENaC regulation (SGK1 and Nedd4-2) were concomitantly phosphorylated in wild-type, but not knockout, mice. We observed differences in urine electrolytes within 60 minutes, and plasma [K + ] was greater in knockout mice within 3 hours of gavage. Renal outer medullary potassium (ROMK) channels were not acutely stimulated in wild-type or knockout mice, nor were phosphorylation of other mTORC2 substrates (PKC and Akt). CONCLUSIONS The mTORC2-SGK1-Nedd4-2-ENaC signaling axis is a key mediator of rapid tubule cell responses to increased plasma [K + ] in vivo . The effects of K + on this signaling module are specific, in that other downstream mTORC2 targets, such as PKC and Akt, are not acutely affected, and ROMK and Large-conductance K + (BK) channels are not activated. These findings provide new insight into the signaling network and ion transport systems that underlie renal responses to K +in vivo .
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Affiliation(s)
- Bidisha Saha
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
| | - Waheed Shabbir
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
| | - Enzo Takagi
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
| | - Xin-Peng Duan
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Deise Carla Almeida Leite Dellova
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
- Current address: Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of São Paulo, Pirassununga, Sao Paulo, Brazil
| | - John Demko
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
| | - Anna Manis
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
| | | | | | - Mads Vaarby Sørensen
- Department of Biomedicine, Unit of Physiology, Aarhus University, Aarhus, Denmark
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - David Pearce
- Department of Medicine, Division of Nephrology, Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California
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Fan M, Zhang J, Lee CL, Zhang J, Feng L. Structure and thiazide inhibition mechanism of the human Na-Cl cotransporter. Nature 2023; 614:788-793. [PMID: 36792826 PMCID: PMC10030352 DOI: 10.1038/s41586-023-05718-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 01/09/2023] [Indexed: 02/17/2023]
Abstract
The sodium-chloride cotransporter (NCC) is critical for kidney physiology1. The NCC has a major role in salt reabsorption in the distal convoluted tubule of the nephron2,3, and mutations in the NCC cause the salt-wasting disease Gitelman syndrome4. As a key player in salt handling, the NCC regulates blood pressure and is the target of thiazide diuretics, which have been widely prescribed as first-line medications to treat hypertension for more than 60 years5-7. Here we determined the structures of human NCC alone and in complex with a commonly used thiazide diuretic using cryo-electron microscopy. These structures, together with functional studies, reveal major conformational states of the NCC and an intriguing regulatory mechanism. They also illuminate how thiazide diuretics specifically interact with the NCC and inhibit its transport function. Our results provide critical insights for understanding the Na-Cl cotransport mechanism of the NCC, and they establish a framework for future drug design and for interpreting disease-related mutations.
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Affiliation(s)
- Minrui Fan
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jianxiu Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Chien-Ling Lee
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jinru Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Liang Feng
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
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7
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Nan J, Yuan Y, Yang X, Shan Z, Liu H, Wei F, Zhang W, Zhang Y. Cryo-EM structure of the human sodium-chloride cotransporter NCC. SCIENCE ADVANCES 2022; 8:eadd7176. [PMID: 36351028 PMCID: PMC9645730 DOI: 10.1126/sciadv.add7176] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/21/2022] [Indexed: 05/29/2023]
Abstract
The sodium-chloride cotransporter NCC mediates the coupled import of sodium and chloride across the plasma membrane, playing vital roles in kidney extracellular fluid volume and blood pressure control. Here, we present the full-length structure of human NCC, with 2.9 Å for the transmembrane domain and 3.8 Å for the carboxyl-terminal domain. NCC adopts an inward-open conformation and a domain-swap dimeric assembly. Conserved ion binding sites among the cation-chloride cotransporters and the Na2 site are observed in our structure. A unique His residue in the substrate pocket in NCC potentially interacts with Na1 and Cl1 and might also mediate the coordination of Na2 through a Ser residue. Putative observed water molecules are indicated to participate in the coordination of ions and TM coupling. Together with transport activity assays, our structure provides the first glimpse of NCC and defines ion binding sites, promoting drug development for hypertension targeting on NCC.
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Affiliation(s)
- Jing Nan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yafei Yuan
- Beijing Frontier Research Center for Biological Structure, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xuemei Yang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Ziyang Shan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Huihui Liu
- Warshel Institute for Computational Biology, School of Life and Health Sciences, The Chinese University of Hong Kong, Shenzhen 518172, Guangdong, China
| | - Feiwen Wei
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Wei Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yanqing Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
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Shrivastav S, Lee H, Okamoto K, Lu H, Yoshida T, Latt KZ, Wakashin H, Dalgleish JLT, Koritzinsky EH, Xu P, Asico LD, Chung JY, Hewitt S, Gildea JJ, Felder RA, Jose PA, Rosenberg AZ, Knepper MA, Kino T, Kopp JB. HIV-1 Vpr suppresses expression of the thiazide-sensitive sodium chloride co-transporter in the distal convoluted tubule. PLoS One 2022; 17:e0273313. [PMID: 36129874 PMCID: PMC9491550 DOI: 10.1371/journal.pone.0273313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 08/07/2022] [Indexed: 11/19/2022] Open
Abstract
HIV-associated nephropathy (HIVAN) impairs functions of both glomeruli and tubules. Attention has been previously focused on the HIVAN glomerulopathy. Tubular injury has drawn increased attention because sodium wasting is common in hospitalized HIV/AIDS patients. We used viral protein R (Vpr)-transgenic mice to investigate the mechanisms whereby Vpr contributes to urinary sodium wasting. In phosphoenolpyruvate carboxykinase promoter-driven Vpr-transgenic mice, in situ hybridization showed that Vpr mRNA was expressed in all nephron segments, including the distal convoluted tubule. Vpr-transgenic mice, compared with wild-type littermates, markedly increased urinary sodium excretion, despite similar plasma renin activity and aldosterone levels. Kidneys from Vpr-transgenic mice also markedly reduced protein abundance of the Na+-Cl- cotransporter (NCC), while mineralocorticoid receptor (MR) protein expression level was unchanged. In African green monkey kidney cells, Vpr abrogated the aldosterone-mediated stimulation of MR transcriptional activity. Gene expression of Slc12a3 (NCC) in Vpr-transgenic mice was significantly lower compared with wild-type mice, assessed by both qRT-PCR and RNAScope in situ hybridization analysis. Chromatin immunoprecipitation assays identified multiple MR response elements (MRE), located from 5 kb upstream of the transcription start site and extending to the third exon of the SLC12A3 gene. Mutation of MRE and SP1 sites in the SLC12A3 promoter region abrogated the transcriptional responses to aldosterone and Vpr, indicating that functional MRE and SP1 are required for the SLC12A3 gene suppression in response to Vpr. Thus, Vpr attenuates MR transcriptional activity and inhibits Slc12a3 transcription in the distal convoluted tubule and contributes to salt wasting in Vpr-transgenic mice.
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Affiliation(s)
- Shashi Shrivastav
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Hewang Lee
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC, United States of America
| | - Koji Okamoto
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Huiyan Lu
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Teruhiko Yoshida
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Khun Zaw Latt
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Hidefumi Wakashin
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - James L. T. Dalgleish
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Erik H. Koritzinsky
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Peng Xu
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Laureano D. Asico
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC, United States of America
| | - Joon-Yong Chung
- Experimental Pathology Laboratory, Laboratory of Pathology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - Stephen Hewitt
- Experimental Pathology Laboratory, Laboratory of Pathology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - John J. Gildea
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Robin A. Felder
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Pedro A. Jose
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC, United States of America
| | - Avi Z. Rosenberg
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America
| | - Mark A. Knepper
- Epithelial Systems Biology Laboratory, Systems Biology Center, Division of Intramural Research, NHLBI, NIH, Bethesda, Maryland, United States of America
| | - Tomoshige Kino
- Laboratory for Molecular and Genomic Endocrinology, Division of Translational Medicine, Sidra Medicine, Doha, Qatar
| | - Jeffrey B. Kopp
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
- * E-mail:
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Staruschenko A, Hodges MR, Palygin O. Kir5.1 channels: potential role in epilepsy and seizure disorders. Am J Physiol Cell Physiol 2022; 323:C706-C717. [PMID: 35848616 PMCID: PMC9448276 DOI: 10.1152/ajpcell.00235.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/06/2022] [Accepted: 07/08/2022] [Indexed: 11/22/2022]
Abstract
Inwardly rectifying potassium (Kir) channels are broadly expressed in many mammalian organ systems, where they contribute to critical physiological functions. However, the importance and function of the Kir5.1 channel (encoded by the KCNJ16 gene) have not been fully recognized. This review focuses on the recent advances in understanding the expression patterns and functional roles of Kir5.1 channels in fundamental physiological systems vital to potassium homeostasis and neurological disorders. Recent studies have described the role of Kir5.1-forming Kir channels in mouse and rat lines with mutations in the Kcnj16 gene. The animal research reveals distinct renal and neurological phenotypes, including pH and electrolyte imbalances, blunted ventilatory responses to hypercapnia/hypoxia, and seizure disorders. Furthermore, it was confirmed that these phenotypes are reminiscent of those in patient cohorts in which mutations in the KCNJ16 gene have also been identified, further suggesting a critical role for Kir5.1 channels in homeostatic/neural systems health and disease. Future studies that focus on the many functional roles of these channels, expanded genetic screening in human patients, and the development of selective small-molecule inhibitors for Kir5.1 channels, will continue to increase our understanding of this unique Kir channel family member.
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Affiliation(s)
- Alexander Staruschenko
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
- Hypertension and Kidney Research Center, University of South Florida, Tampa, Florida
- James A. Haley Veterans Hospital, Tampa, Florida
| | - Matthew R Hodges
- Department of Physiology and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Oleg Palygin
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
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10
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McDonough AA, Fenton RA. Potassium homeostasis: sensors, mediators, and targets. Pflugers Arch 2022; 474:853-867. [PMID: 35727363 PMCID: PMC10163916 DOI: 10.1007/s00424-022-02718-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 06/08/2022] [Accepted: 06/12/2022] [Indexed: 12/16/2022]
Abstract
Transmembrane potassium (K) gradients are key determinants of membrane potential that can modulate action potentials, control muscle contractility, and influence ion channel and transporter activity. Daily K intake is normally equal to the amount of K in the entire extracellular fluid (ECF) creating a critical challenge - how to maintain ECF [K] and membrane potential in a narrow range during feast and famine. Adaptations to maintain ECF [K] include sensing the K intake, sensing ECF [K] vs. desired set-point and activating mediators that regulate K distribution between ECF and ICF, and regulate renal K excretion. In this focused review, we discuss the basis of these adaptions, including (1) potential mechanisms for rapid feedforward signaling to kidney and muscle after a meal (before a rise in ECF [K]), (2) how skeletal muscles sense and respond to changes in ECF [K], (3) effects of K on aldosterone biosynthesis, and (4) how the kidney responds to changes in ECF [K] to modify K excretion. The concepts of sexual dimorphisms in renal K handling adaptation are introduced, and the molecular mechanisms that can account for the benefits of a K-rich diet to maintain cardiovascular health are discussed. Although the big picture of K homeostasis is becoming more clear, we also highlight significant pieces of the puzzle that remain to be solved, including knowledge gaps in our understanding of initiating signals, sensors and their connection to homeostatic adjustments of ECF [K].
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Affiliation(s)
- Alicia A McDonough
- Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, USA.
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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