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Bahbahani H. Long-range linkage disequilibrium events on the genome of dromedary camels as a signal of epistatic and directional positive selection. Heliyon 2024; 10:e34343. [PMID: 39100441 PMCID: PMC11295981 DOI: 10.1016/j.heliyon.2024.e34343] [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: 06/27/2024] [Accepted: 07/08/2024] [Indexed: 08/06/2024] Open
Abstract
The genome of dromedary camels has been subjected to various evolutionary forces, such as genetic admixture, natural positive selection, and epistatic selection. These forces are considered as main factors associated with the formation of long-range linkage disequilibrium (LRLD) events. We have analyzed whole-genome data of 56 dromedary camel samples from different geographical regions across the Arabian Peninsula for two main purposes: first, to assess the level of linkage disequilibrium, and second, to identify autosomal LRLD events. The analysis revealed a mean r 2 value of 0.25 (±0.028) over the dromedary autosomes, with a continuous decay until reaching a plateau at inter-variant distances >400 kb. A total of 1847 LRLD events were identified within the dromedary autosomes, which harbor 36 prevalent haplotypes. A level of genetic admixture was observed among the dromedary populations analyzed, which might be a source for the observed LRLD events. Four functional interactions were revealed among the genes found within the LRLD events, with some genes overlapping with prevalent haplotypes, indicative of potential epistatic selection. Genes related to renal function, fertility, thermal regulation, bone structure, and insulin regulation were found among the LRLD genes. These genes, along with the defined prevalent haplotypes, can be considered as hotspots for natural positive selection associated with the LRLD distribution on dromedary genomes. In this study, we have for the first time analyzed the genome of dromedary camels for LRLD events possibly influenced by forces including genetic admixture, epistatic and positive selection. The revealed LRLD elements and prevalent haplotypes should be accounted for when designing breeding programmes to conserve the genetic stock of this well-adapted domestic species.
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Affiliation(s)
- Hussain Bahbahani
- Department of Biological Sciences, Faculty of Science, Kuwait University, Sh. Sabah Al-Salem Campus, Kuwait
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2
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Gantsova E, Serova O, Vishnyakova P, Deyev I, Elchaninov A, Fatkhudinov T. Mechanisms and physiological relevance of acid-base exchange in functional units of the kidney. PeerJ 2024; 12:e17316. [PMID: 38699185 PMCID: PMC11064853 DOI: 10.7717/peerj.17316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 04/09/2024] [Indexed: 05/05/2024] Open
Abstract
This review discusses the importance of homeostasis with a particular emphasis on the acid-base (AB) balance, a crucial aspect of pH regulation in living systems. Two primary organ systems correct deviations from the standard pH balance: the respiratory system via gas exchange and the kidneys via proton/bicarbonate secretion and reabsorption. Focusing on kidney functions, we describe the complexity of renal architecture and its challenges for experimental research. We address specific roles of different nephron segments (the proximal convoluted tubule, the loop of Henle and the distal convoluted tubule) in pH homeostasis, while explaining the physiological significance of ion exchange processes maintained by the kidneys, particularly the role of bicarbonate ions (HCO3-) as an essential buffer system of the body. The review will be of interest to researchers in the fields of physiology, biochemistry and molecular biology, which builds a strong foundation and critically evaluates existing studies. Our review helps identify the gaps of knowledge by thoroughly understanding the existing literature related to kidney acid-base homeostasis.
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Affiliation(s)
- Elena Gantsova
- Avtsyn Research Institute of Human Morphology of Federal State Budgetary Scientific Institution “Petrovsky National Research Centre of Surgery”, Moscow, Russia
- Research Institute of Molecular and Cellular Medicine, Peoples’ Friendship University of Russia (RUDN University), Moscow, Russia
| | - Oxana Serova
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation
| | - Polina Vishnyakova
- Research Institute of Molecular and Cellular Medicine, Peoples’ Friendship University of Russia (RUDN University), Moscow, Russia
- National Medical Research Center for Obstetrics, Gynecology and Perinatology Named after Academician V.I. Kulakov of Ministry of Healthcare of Russian Federation, Moscow, Russian Federation
| | - Igor Deyev
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation
| | - Andrey Elchaninov
- Avtsyn Research Institute of Human Morphology of Federal State Budgetary Scientific Institution “Petrovsky National Research Centre of Surgery”, Moscow, Russia
- Research Institute of Molecular and Cellular Medicine, Peoples’ Friendship University of Russia (RUDN University), Moscow, Russia
| | - Timur Fatkhudinov
- Avtsyn Research Institute of Human Morphology of Federal State Budgetary Scientific Institution “Petrovsky National Research Centre of Surgery”, Moscow, Russia
- Research Institute of Molecular and Cellular Medicine, Peoples’ Friendship University of Russia (RUDN University), Moscow, Russia
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3
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Chrysopoulou M, Rinschen MM. Metabolic Rewiring and Communication: An Integrative View of Kidney Proximal Tubule Function. Annu Rev Physiol 2024; 86:405-427. [PMID: 38012048 DOI: 10.1146/annurev-physiol-042222-024724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The kidney proximal tubule is a key organ for human metabolism. The kidney responds to stress with altered metabolite transformation and perturbed metabolic pathways, an ultimate cause for kidney disease. Here, we review the proximal tubule's metabolic function through an integrative view of transport, metabolism, and function, and embed it in the context of metabolome-wide data-driven research. Function (filtration, transport, secretion, and reabsorption), metabolite transformation, and metabolite signaling determine kidney metabolic rewiring in disease. Energy metabolism and substrates for key metabolic pathways are orchestrated by metabolite sensors. Given the importance of renal function for the inner milieu, we also review metabolic communication routes with other organs. Exciting research opportunities exist to understand metabolic perturbation of kidney and proximal tubule function, for example, in hypertension-associated kidney disease. We argue that, based on the integrative view outlined here, kidney diseases without genetic cause should be approached scientifically as metabolic diseases.
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Affiliation(s)
| | - Markus M Rinschen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark;
- III. Department of Medicine and Hamburg Center for Kidney Health, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
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4
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Gantsova EA, Serova OV, Eladari D, Bobrovskiy DM, Petrenko AG, Elchaninov AV, Deyev IE. A Comparative Kidney Transcriptome Analysis of Bicarbonate-Loaded insrr-Null Mice. Curr Issues Mol Biol 2023; 45:9709-9722. [PMID: 38132452 PMCID: PMC10742211 DOI: 10.3390/cimb45120606] [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: 10/19/2023] [Revised: 11/23/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023] Open
Abstract
The maintenance of plasma pH is critical for life in all organisms. The kidney plays a critical role in acid-base regulation in vertebrates by controlling the plasma concentration of bicarbonate. The receptor tyrosine kinase IRR (insulin receptor-related receptor) is expressed in renal β-intercalated cells and is involved in alkali sensing due to its ability to autophosphorylate under alkalization of extracellular medium (pH > 7.9). In mice with a knockout of the insrr gene, which encodes for IRR, urinary bicarbonate secretion in response to alkali loading is impaired. The specific regulatory mechanisms in the kidney that are under the control of IRR remain unknown. To address this issue, we analyzed and compared the kidney transcriptomes of wild-type and insrr knockout mice under basal or bicarbonate-loaded conditions. Transcriptomic analyses revealed a differential regulation of a number of genes in the kidney. Using TaqMan real-time PCR, we confirmed different expressions of the slc26a4, rps7, slc5a2, aqp6, plcd1, gapdh, rny3, kcnk5, slc6a6 and atp6v1g3 genes in IRR knockout mice. Also, we found that the expression of the kcnk5 gene is increased in wild-type mice after bicarbonate loading but not in knockout mice. Gene set enrichment analysis between the IRR knockout and wild-type samples identified that insrr knockout causes alterations in expression of genes related mostly to the ATP metabolic and electron transport chain processes.
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Affiliation(s)
- E. A. Gantsova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the RAS, Moscow 117997, Russia; (E.A.G.); (O.V.S.); (A.G.P.)
- Avtsyn Research Institute of Human Morphology of Federal State Budgetary Scientific Institution “Petrovsky National Research Centre of Surgery”, Moscow 117418, Russia;
| | - O. V. Serova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the RAS, Moscow 117997, Russia; (E.A.G.); (O.V.S.); (A.G.P.)
| | - D. Eladari
- Service de Médecine de Précision des Maladies Métaboliques et Rénales, CHU Amiens-Picardie, Université de Picardie Jules Verne, 80054 Amiens, France
| | - D. M. Bobrovskiy
- School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - A. G. Petrenko
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the RAS, Moscow 117997, Russia; (E.A.G.); (O.V.S.); (A.G.P.)
| | - A. V. Elchaninov
- Avtsyn Research Institute of Human Morphology of Federal State Budgetary Scientific Institution “Petrovsky National Research Centre of Surgery”, Moscow 117418, Russia;
| | - I. E. Deyev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the RAS, Moscow 117997, Russia; (E.A.G.); (O.V.S.); (A.G.P.)
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5
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Guo W, Ji P, Xie Y. Genetic Diagnosis and Treatment of Inherited Renal Tubular Acidosis. KIDNEY DISEASES (BASEL, SWITZERLAND) 2023; 9:371-383. [PMID: 37901710 PMCID: PMC10601937 DOI: 10.1159/000531556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 06/12/2023] [Indexed: 10/31/2023]
Abstract
Background Renal tubular acidosis (RTA) is caused by various disruptions to the secretion of H+ by distal renal tubules and/or dysfunctional reabsorption of HCO3- by proximal renal tubules, which causes renal acidification dysfunction, ultimately leading to a clinical syndrome characterized by hyperchloremic metabolic acidosis with a normal anion gap. With the development of molecular genetics and gene sequencing technology, inherited RTA has also attracted attention, and an increasing number of RTA-related pathogenic genes have been discovered and reported. Summary This paper focuses on the latest progress in the research of inherited RTA and systematically reviews the pathogenic genes, protein functions, clinical manifestations, internal relationship between genotypes and clinical phenotypes, diagnostic clues, differential diagnosis, and treatment strategies associated with inherited RTA. This paper aims to deepen the understanding of inherited RTA and reduce the missed diagnosis and misdiagnosis of RTA. Key Messages This review systematically summarizes the pathogenic genes, pathophysiological mechanisms, differential diagnosis, and treatment of different types of inherited RTA, which has good clinical value for guiding the diagnosis and treatment of inherited RTA.
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Affiliation(s)
- Wenkai Guo
- Department of Nephrology, First Medical Center of Chinese PLA General Hospital, Chinese PLA Institute of Nephrology, State Key Laboratory of Kidney Diseases, National Clinical Research Center for Kidney Diseases, Beijing, China
- School of Medicine, Nankai University, Tianjin, China
| | - Pengcheng Ji
- Department of Nephrology, First Medical Center of Chinese PLA General Hospital, Chinese PLA Institute of Nephrology, State Key Laboratory of Kidney Diseases, National Clinical Research Center for Kidney Diseases, Beijing, China
| | - Yuansheng Xie
- Department of Nephrology, First Medical Center of Chinese PLA General Hospital, Chinese PLA Institute of Nephrology, State Key Laboratory of Kidney Diseases, National Clinical Research Center for Kidney Diseases, Beijing, China
- School of Medicine, Nankai University, Tianjin, China
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Gonye EC, Bayliss DA. Criteria for central respiratory chemoreceptors: experimental evidence supporting current candidate cell groups. Front Physiol 2023; 14:1241662. [PMID: 37719465 PMCID: PMC10502317 DOI: 10.3389/fphys.2023.1241662] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 08/16/2023] [Indexed: 09/19/2023] Open
Abstract
An interoceptive homeostatic system monitors levels of CO2/H+ and provides a proportionate drive to respiratory control networks that adjust lung ventilation to maintain physiologically appropriate levels of CO2 and rapidly regulate tissue acid-base balance. It has long been suspected that the sensory cells responsible for the major CNS contribution to this so-called respiratory CO2/H+ chemoreception are located in the brainstem-but there is still substantial debate in the field as to which specific cells subserve the sensory function. Indeed, at the present time, several cell types have been championed as potential respiratory chemoreceptors, including neurons and astrocytes. In this review, we advance a set of criteria that are necessary and sufficient for definitive acceptance of any cell type as a respiratory chemoreceptor. We examine the extant evidence supporting consideration of the different putative chemoreceptor candidate cell types in the context of these criteria and also note for each where the criteria have not yet been fulfilled. By enumerating these specific criteria we hope to provide a useful heuristic that can be employed both to evaluate the various existing respiratory chemoreceptor candidates, and also to focus effort on specific experimental tests that can satisfy the remaining requirements for definitive acceptance.
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Affiliation(s)
- Elizabeth C. Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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7
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Synergistic effects of agonists and two-pore-domain potassium channels on secretory responses of human pancreatic duct cells Capan-1. Pflugers Arch 2023; 475:361-379. [PMID: 36534232 PMCID: PMC9908661 DOI: 10.1007/s00424-022-02782-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 12/02/2022] [Accepted: 12/07/2022] [Indexed: 12/23/2022]
Abstract
Mechanisms of synergistic agonist stimulation and modulation of the electrochemical driving force for anion secretion are still not fully explored in human pancreatic duct epithelial cells. The first objective of this study was therefore to test whether combined agonist stimulation augments anion transport responses in the Capan-1 monolayer model of human pancreatic duct epithelium. The second objective was to test the influence of H+,K+-ATPase inhibition on anion transport in Capan-1 monolayers. The third objective was to analyze the expression and function of K+ channels in Capan-1, which could support anion secretion and cooperate with H+,K+-ATPases in pH and potassium homeostasis. The human pancreatic adenocarcinoma cell line Capan-1 was cultured conventionally or as polarized monolayers that were analyzed by Ussing chamber electrophysiological recordings. Single-cell intracellular calcium was assayed with Fura-2. mRNA isolated from Capan-1 was analyzed by use of the nCounter assay or RT-PCR. Protein expression was assessed by immunofluorescence and western blot analyses. Combined stimulation with different physiological agonists enhanced anion transport responses compared to single agonist stimulation. The responsiveness of Capan-1 cells to histamine was also revealed in these experiments. The H+,K+-ATPase inhibitor omeprazole reduced carbachol- and riluzole-induced anion transport responses. Transcript analyses revealed abundant TASK-2, TWIK-1, TWIK-2, TASK-5, KCa3.1, and KCNQ1 mRNA expression. KCNE1 mRNA and TREK-1, TREK-2, TASK-2, and KCNQ1 protein expression were also shown. This study shows that the Capan-1 model recapitulates key physiological aspects of a bicarbonate-secreting epithelium and constitutes a valuable model for functional studies on human pancreatic duct epithelium.
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8
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Khoubza L, Gilbert N, Kim EJ, Chatelain FC, Feliciangeli S, Abelanet S, Kang D, Lesage F, Bichet D. Alkaline-sensitive two-pore domain potassium channels form functional heteromers in pancreatic β-cells. J Biol Chem 2022; 298:102447. [PMID: 36063992 PMCID: PMC9520024 DOI: 10.1016/j.jbc.2022.102447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 11/15/2022] Open
Abstract
Two-pore domain K+ channels (K2P channels), active as dimers, produce inhibitory currents regulated by a variety of stimuli. Among them, TWIK1-related alkalinization-activated K+ channel 1 (TALK1), TWIK1-related alkalinization-activated K+ channel 2 (TALK2), and TWIK1-related acid-sensitive K+ channel 2 (TASK2) form a subfamily of structurally related K2P channels stimulated by extracellular alkalosis. The human genes encoding these proteins are clustered at chromosomal region 6p21 and coexpressed in multiple tissues, including the pancreas. The question whether these channels form functional heteromers remained open. By analyzing single-cell transcriptomic data, we show that these channels are coexpressed in insulin-secreting pancreatic β-cells. Using in situ proximity ligation assay and electrophysiology, we show that they form functional heterodimers both upon heterologous expression and under native conditions in human pancreatic β-cells. We demonstrate that heteromerization of TALK2 with TALK1 or with TASK2 endows TALK2 with sensitivity to extracellular alkalosis in the physiological range. We further show that the association of TASK2 with TALK1 and TALK2 increases their unitary conductance. These results provide a new example of heteromerization in the K2P channel family expanding the range of the potential physiological and pathophysiological roles of TALK1/TALK2/TASK2 channels, not only in insulin-secreting cells but also in the many other tissues in which they are coexpressed.
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Affiliation(s)
- Lamyaa Khoubza
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France
| | - Nicolas Gilbert
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France
| | - Eun-Jin Kim
- Department of Physiology, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju, South Korea
| | - Franck C Chatelain
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France
| | - Sylvain Feliciangeli
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France; Inserm, Paris, France
| | - Sophie Abelanet
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France
| | - Dawon Kang
- Department of Physiology, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju, South Korea
| | - Florian Lesage
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France; Inserm, Paris, France.
| | - Delphine Bichet
- Université côte d'Azur, IPMC CNRS UMR7275, Laboratory of Excellence ICST, Valbonne, France
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Palmer LG. Directing two-way traffic in the kidney: A tale of two ions. J Gen Physiol 2022; 154:213433. [PMID: 36048011 PMCID: PMC9437110 DOI: 10.1085/jgp.202213179] [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] [Indexed: 12/14/2022] Open
Abstract
The kidneys regulate levels of Na+ and K+ in the body by varying urinary excretion of the electrolytes. Since transport of each of the two ions can affect the other, controlling both at the same time is a complex task. The kidneys meet this challenge in two ways. Some tubular segments change the coupling between Na+ and K+ transport. In addition, transport of Na+ can shift between segments where it is coupled to K+ reabsorption and segments where it is coupled to K+ secretion. This permits the kidney to maintain electrolyte balance with large variations in dietary intake.
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Affiliation(s)
- Lawrence G. Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY,Correspondence to Lawrence G. Palmer:
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10
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Wang L, Lin X, Zhou Z, Yang Y, Gao P, Wu Z. Genetic Variants Involved in the Crystallization Pathway Are Associated with Calcium Nephrolithiasis in the Chinese Han Population. Genes (Basel) 2022; 13:genes13060943. [PMID: 35741705 PMCID: PMC9222851 DOI: 10.3390/genes13060943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 05/12/2022] [Accepted: 05/18/2022] [Indexed: 02/05/2023] Open
Abstract
A genome-wide association analysis study (GWAS) in the Japanese population identified 14 significant loci associated with nephrolithiasis. Besides 4 novel loci related to metabolic traits, the 10 remaining loci were associated with kidney or electrolyte-related traits. We aimed to replicate the association of these loci with calcium nephrolithiasis in the Chinese Han population. A case–control association analysis was conducted involving 691 calcium nephrolithiasis patients and 1008 control subjects. We were able to genotype a total of 11 single-nucleotide polymorphisms (SNPs) previously identified as being correlated with nephrolithiasis in the Japanese population. SNP rs35747824 at PDILT was related to calcium nephrolithiasis in the Chinese Han population (p = 4.346 × 10−3, OR = 1.292). Moreover, four SNPs at four loci, rs6667242 at ALPL (p = 0.02999, OR = 0.8331), rs1544935 at KCNK5 (p = 0.01341, OR = 0.7804), rs7328064 at DGKH (p = 0.007452, OR = 1.211) and rs13041834 at BCAS1 (p = 0.03897, OR = 0.8409), were suggestively associated with calcium nephrolithiasis. Our results demonstrated that the genetic variants at 1p36.12, 6p21.2, 13q14.11, 16p12.3 and 20q13.2 are associated with calcium nephrolithiasis in the Chinese Han population. Furthermore, our study highlights the importance of genetic variance associated with the crystallization pathway in Chinese patients with calcium nephrolithiasis.
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Affiliation(s)
- Lujia Wang
- Department of Urology, Huashan Hospital & Institute of Urology, Fudan University, Shanghai 200040, China; (L.W.); (Z.Z.); (Y.Y.); (P.G.)
- Clinical Research Center of Urolithiasis, Shanghai Medical College, Fudan University, Shanghai 200040, China
| | - Xiaoling Lin
- Department of Urology, Shanghai Children’s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200062, China;
| | - Zijian Zhou
- Department of Urology, Huashan Hospital & Institute of Urology, Fudan University, Shanghai 200040, China; (L.W.); (Z.Z.); (Y.Y.); (P.G.)
- Clinical Research Center of Urolithiasis, Shanghai Medical College, Fudan University, Shanghai 200040, China
| | - Yuanyuan Yang
- Department of Urology, Huashan Hospital & Institute of Urology, Fudan University, Shanghai 200040, China; (L.W.); (Z.Z.); (Y.Y.); (P.G.)
- Clinical Research Center of Urolithiasis, Shanghai Medical College, Fudan University, Shanghai 200040, China
| | - Peng Gao
- Department of Urology, Huashan Hospital & Institute of Urology, Fudan University, Shanghai 200040, China; (L.W.); (Z.Z.); (Y.Y.); (P.G.)
- Clinical Research Center of Urolithiasis, Shanghai Medical College, Fudan University, Shanghai 200040, China
| | - Zhong Wu
- Department of Urology, Huashan Hospital & Institute of Urology, Fudan University, Shanghai 200040, China; (L.W.); (Z.Z.); (Y.Y.); (P.G.)
- Clinical Research Center of Urolithiasis, Shanghai Medical College, Fudan University, Shanghai 200040, China
- Correspondence: ; Tel.: +86-21-52887081
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11
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Imenez Silva PH, Mohebbi N. Kidney metabolism and acid-base control: back to the basics. Pflugers Arch 2022; 474:919-934. [PMID: 35513635 PMCID: PMC9338915 DOI: 10.1007/s00424-022-02696-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 01/18/2023]
Abstract
Kidneys are central in the regulation of multiple physiological functions, such as removal of metabolic wastes and toxins, maintenance of electrolyte and fluid balance, and control of pH homeostasis. In addition, kidneys participate in systemic gluconeogenesis and in the production or activation of hormones. Acid-base conditions influence all these functions concomitantly. Healthy kidneys properly coordinate a series of physiological responses in the face of acute and chronic acid-base disorders. However, injured kidneys have a reduced capacity to adapt to such challenges. Chronic kidney disease patients are an example of individuals typically exposed to chronic and progressive metabolic acidosis. Their organisms undergo a series of alterations that brake large detrimental changes in the homeostasis of several parameters, but these alterations may also operate as further drivers of kidney damage. Acid-base disorders lead not only to changes in mechanisms involved in acid-base balance maintenance, but they also affect multiple other mechanisms tightly wired to it. In this review article, we explore the basic renal activities involved in the maintenance of acid-base balance and show how they are interconnected to cell energy metabolism and other important intracellular activities. These intertwined relationships have been investigated for more than a century, but a modern conceptual organization of these events is lacking. We propose that pH homeostasis indissociably interacts with central pathways that drive progression of chronic kidney disease, such as inflammation and metabolism, independent of etiology.
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Affiliation(s)
- Pedro Henrique Imenez Silva
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.
| | - Nilufar Mohebbi
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
- Praxis Und Dialysezentrum Zurich, Zurich, Switzerland
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12
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Neubauer J, Forst AL, Warth R, Both CP, Haas C, Thomas J. Genetic variants in eleven central and peripheral chemoreceptor genes in sudden infant death syndrome. Pediatr Res 2022; 92:1026-1033. [PMID: 35102300 PMCID: PMC9586864 DOI: 10.1038/s41390-021-01899-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 07/14/2021] [Accepted: 08/16/2021] [Indexed: 12/15/2022]
Abstract
BACKGROUND Sudden infant death syndrome (SIDS) is still one of the leading causes of postnatal infant death in developed countries. The occurrence of SIDS is described by a multifactorial etiology that involves the respiratory control system including chemoreception. It is still unclear whether genetic variants in genes involved in respiratory chemoreception might play a role in SIDS. METHODS The exome data of 155 SIDS cases were screened for variants within 11 genes described in chemoreception. Pathogenicity of variants was assigned based on the assessment of variant types and in silico protein predictions according to the current recommendations of the American College of Medical Genetics and Genomics. RESULTS Potential pathogenic variants in genes encoding proteins involved in respiratory chemoreception could be identified in 5 (3%) SIDS cases. Two of the variants (R137S/A188S) were found in the KNCJ16 gene, which encodes for the potassium channel Kir5.1, presumably involved in central chemoreception. Electrophysiologic analysis of these KCNJ16 variants revealed a loss-of-function for the R137S variant but no obvious impairment for the A188S variant. CONCLUSIONS Genetic variants in genes involved in respiratory chemoreception may be a risk factor in a fraction of SIDS cases and may thereby contribute to the multifactorial etiology of SIDS. IMPACT What is the key message of your article? Gene variants encoding proteins involved in respiratory chemoreception may play a role in a minority of SIDS cases. What does it add to the existing literature? Although impaired respiratory chemoreception has been suggested as an important risk factor for SIDS, genetic variants in single genes seem to play a minor role. What is the impact? This study supports previous findings, which indicate that genetic variants in single genes involved in respiratory control do not have a dominant role in SIDS.
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Affiliation(s)
- Jacqueline Neubauer
- grid.7400.30000 0004 1937 0650Zurich Institute of Forensic Medicine, University of Zurich, Zurich, Switzerland
| | - Anna-Lena Forst
- grid.7727.50000 0001 2190 5763Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Richard Warth
- grid.7727.50000 0001 2190 5763Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Christian Peter Both
- grid.412341.10000 0001 0726 4330Department of Anesthesiology, University Children’s Hospital Zurich, Zurich, Switzerland
| | - Cordula Haas
- grid.7400.30000 0004 1937 0650Zurich Institute of Forensic Medicine, University of Zurich, Zurich, Switzerland
| | - Jörg Thomas
- Department of Anesthesiology, University Children's Hospital Zurich, Zurich, Switzerland.
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13
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Berg P, Svendsen SL, Sorensen MV, Schreiber R, Kunzelmann K, Leipziger J. The molecular mechanism of CFTR- and secretin-dependent renal bicarbonate excretion. J Physiol 2021; 599:3003-3011. [PMID: 33963548 DOI: 10.1113/jp281285] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 04/12/2021] [Indexed: 11/08/2022] Open
Abstract
This review summarizes the newly discovered molecular mechanism of secretin-stimulated urine HCO3 - excretion and the role of cystic fibrosis transmembrane conductance regulator (CFTR) in renal HCO3 - excretion. The secretin receptor is functionally expressed in the basolateral membrane of the HCO3 - -secreting β-intercalated cells of the collecting duct. Here it activates a fast and efficient secretion of HCO3 - into the urine serving to normalize metabolic alkalosis. The ability to acutely increase renal base excretion is entirely dependent on functional pendrin (SLC26A4) and CFTR, and both proteins localize to the apical membrane of the β-intercalated cells. In cystic fibrosis mice and patients, this function is absent or markedly reduced. We discuss that the alkaline tide, namely the transient urine alkalinity after a meal, has now received a clear physiological explanation.
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Affiliation(s)
- Peder Berg
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
| | - Samuel L Svendsen
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
| | - Mads Vaarby Sorensen
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
| | - Rainer Schreiber
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Jens Leipziger
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
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14
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Yi C, Spitters TWGM, Al-Far EADA, Wang S, Xiong T, Cai S, Yan X, Guan K, Wagner M, El-Armouche A, Antos CL. A calcineurin-mediated scaling mechanism that controls a K +-leak channel to regulate morphogen and growth factor transcription. eLife 2021; 10:e60691. [PMID: 33830014 PMCID: PMC8110307 DOI: 10.7554/elife.60691] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 04/07/2021] [Indexed: 01/10/2023] Open
Abstract
The increase in activity of the two-pore potassium-leak channel Kcnk5b maintains allometric juvenile growth of adult zebrafish appendages. However, it remains unknown how this channel maintains allometric growth and how its bioelectric activity is regulated to scale these anatomical structures. We show the activation of Kcnk5b is sufficient to activate several genes that are part of important development programs. We provide in vivo transplantation evidence that the activation of gene transcription is cell autonomous. We also show that Kcnk5b will induce the expression of different subsets of the tested developmental genes in different cultured mammalian cell lines, which may explain how one electrophysiological stimulus can coordinately regulate the allometric growth of diverse populations of cells in the fin that use different developmental signals. We also provide evidence that the post-translational modification of serine 345 in Kcnk5b by calcineurin regulates channel activity to scale the fin. Thus, we show how an endogenous bioelectric mechanism can be regulated to promote coordinated developmental signaling to generate and scale a vertebrate appendage.
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Affiliation(s)
- Chao Yi
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
- CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesShanghaiChina
| | - Tim WGM Spitters
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
| | | | - Sen Wang
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
- CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesShanghaiChina
| | - TianLong Xiong
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
- CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesShanghaiChina
| | - Simian Cai
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
| | - Xin Yan
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
| | - Kaomei Guan
- Institut für Pharmakologie und Toxikologie, Technische Universität DresdenDresdenGermany
| | - Michael Wagner
- Institut für Pharmakologie und Toxikologie, Technische Universität DresdenDresdenGermany
- Klinik für Innere Medizin und Kardiologie, Herzzentrum Dresden, Technische Universität DresdenDresdenGermany
| | - Ali El-Armouche
- Institut für Pharmakologie und Toxikologie, Technische Universität DresdenDresdenGermany
| | - Christopher L Antos
- School of Life Sciences and Technology, ShanghaiTech UniversityShanghaiChina
- Institut für Pharmakologie und Toxikologie, Technische Universität DresdenDresdenGermany
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15
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Structural basis for pH gating of the two-pore domain K+ channel TASK2. Nature 2020; 586:457-462. [DOI: 10.1038/s41586-020-2770-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 07/06/2020] [Indexed: 12/31/2022]
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16
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Koudrina N, Perry SF, Gilmour KM. The role of TASK-2 channels in CO 2 sensing in zebrafish ( Danio rerio). Am J Physiol Regul Integr Comp Physiol 2020; 319:R329-R342. [PMID: 32697653 DOI: 10.1152/ajpregu.00132.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Peripheral chemosensitivity in fishes is thought to be mediated by serotonin-enriched neuroepithelial cells (NECs) that are localized to the gills of adults and the integument of larvae. In adult zebrafish (Danio rerio), branchial NECs are presumed to mediate the cardiorespiratory reflexes associated with hypoxia or hypercapnia, whereas in larvae, there is indirect evidence linking cutaneous NECs to hypoxic hyperventilation and hypercapnic tachycardia. No study yet has examined the ventilatory response of larval zebrafish to hypercapnia, and regardless of developmental stage, the signaling pathways involved in CO2 sensing remain unclear. In the mouse, a background potassium channel (TASK-2) contributes to the sensitivity of chemoreceptor cells to CO2. Zebrafish possess two TASK-2 channel paralogs, TASK-2 and TASK-2b, encoded by kcnk5a and kcnk5b, respectively. The present study aimed to determine whether TASK-2 channels are expressed in NECs of larval zebrafish and whether they are involved in CO2 sensing. Using immunohistochemical approaches, TASK-2 protein was observed on the surface of NECs in larvae. Exposure of larvae to hypercapnia caused cardiac and breathing frequencies to increase, and these responses were blunted in fish experiencing TASK-2 and/or TASK-2b knockdown. The results of these experiments suggest that TASK-2 channels are involved in CO2 sensing by NECs and contribute to the initiation of reflex cardiorespiratory responses during exposure of larvae to hypercapnia.
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Affiliation(s)
- N Koudrina
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - S F Perry
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - K M Gilmour
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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17
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Imenez Silva PH, Wagner CA. Potassium channels in control of renal function. Kidney Int 2020; 97:253-255. [PMID: 31980072 DOI: 10.1016/j.kint.2019.10.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 10/22/2019] [Accepted: 10/24/2019] [Indexed: 11/18/2022]
Abstract
Potassium channels are important to control membrane potential and drive epithelial transport processes. In this issue of Kidney International, Bignon et al. report the role of the Kir4.2 K+-channel, localized at the basolateral membrane of proximal tubules, in the reabsorption of bicarbonate and the modulation of renal ammoniagenesis. The findings have implications for our understanding of how the kidney reacts to hypokalemia, an acid load, and the metabolic acidosis of patients with advanced stages of chronic kidney disease.
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Affiliation(s)
- Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center of Competence in Research NCCR Kidney.CH, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center of Competence in Research NCCR Kidney.CH, Switzerland.
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18
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Lanni JS, Peal D, Ekstrom L, Chen H, Stanclift C, Bowen ME, Mercado A, Gamba G, Kahle KT, Harris MP. Integrated K+ channel and K+Cl- cotransporter functions are required for the coordination of size and proportion during development. Dev Biol 2019; 456:164-178. [PMID: 31472116 PMCID: PMC7235970 DOI: 10.1016/j.ydbio.2019.08.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 08/07/2019] [Accepted: 08/23/2019] [Indexed: 10/26/2022]
Abstract
The coordination of growth during development establishes proportionality within and among the different anatomic structures of organisms. Innate memory of this proportionality is preserved, as shown in the ability of regenerating structures to return to their original size. Although the regulation of this coordination is incompletely understood, mutant analyses of zebrafish with long-finned phenotypes have uncovered important roles for bioelectric signaling in modulating growth and size of the fins and barbs. To date, long-finned mutants identified are caused by hypermorphic mutations, leaving unresolved whether such signaling is required for normal development. We isolated a new zebrafish mutant, schleier, with proportional overgrowth phenotypes caused by a missense mutation and loss of function in the K+-Cl- cotransporter Kcc4a. Creation of dominant negative Kcc4a in wild-type fish leads to loss of growth restriction in fins and barbs, supporting a requirement for Kcc4a in regulation of proportion. Epistasis experiments suggest that Kcc4a and the two-pore potassium channel Kcnk5b both contribute to a common bioelectrical signaling response in the fin. These data suggest that an integrated bioelectric signaling pathway is required for the coordination of size and proportion during development.
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Affiliation(s)
| | - David Peal
- Department of Genetics, Harvard Medical School, Boston, MA, 02124, USA; Department of Orthopaedic Research, Boston Children's Hospital, Boston, MA, 02124, USA
| | - Laura Ekstrom
- Department of Biology, Wheaton College, Norton, MA, 02766, USA
| | - Haining Chen
- Department of Biology, Wheaton College, Norton, MA, 02766, USA
| | | | - Margot E Bowen
- Department of Genetics, Harvard Medical School, Boston, MA, 02124, USA; Department of Orthopaedic Research, Boston Children's Hospital, Boston, MA, 02124, USA
| | | | - Gerardo Gamba
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico; Tecnológico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Mexico
| | - Kristopher T Kahle
- Departments of Neurosurgery, Pediatrics, and Cellular & Molecular Physiology, and NIH-Rockefeller Center for Mendelian Genomics, Yale School of Medicine, New Haven, CT, 06511, USA
| | - Matthew P Harris
- Department of Genetics, Harvard Medical School, Boston, MA, 02124, USA; Department of Orthopaedic Research, Boston Children's Hospital, Boston, MA, 02124, USA
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19
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Defective bicarbonate reabsorption in Kir4.2 potassium channel deficient mice impairs acid-base balance and ammonia excretion. Kidney Int 2019; 97:304-315. [PMID: 31870500 DOI: 10.1016/j.kint.2019.09.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 09/16/2019] [Accepted: 09/23/2019] [Indexed: 11/21/2022]
Abstract
The kidneys excrete the daily acid load mainly by generating and excreting ammonia but the underlying molecular mechanisms are not fully understood. Here we evaluated the role of the inwardly rectifying potassium channel subunit Kir4.2 (Kcnj15 gene product) in this process. In mice, Kir4.2 was present exclusively at the basolateral membrane of proximal tubular cells and disruption of Kcnj15 caused a hyperchloremic metabolic acidosis associated with a reduced threshold for bicarbonate in the absence of a generalized proximal tubule dysfunction. Urinary ammonium excretion rates in Kcnj15- deleted mice were inappropriate to acidosis under basal and acid-loading conditions, and not related to a failure to acidify urine or a reduced expression of ammonia transporters in the collecting duct. In contrast, the expression of key proteins involved in ammonia metabolism and secretion by proximal cells, namely the glutamine transporter SNAT3, the phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase enzymes, and the sodium-proton exchanger NHE-3 was inappropriate in Kcnj15-deleted mice. Additionally, Kcnj15 deletion depolarized the proximal cell membrane by decreasing the barium-sensitive component of the potassium conductance and caused an intracellular alkalinization. Thus, the Kir4.2 potassium channel subunit is a newly recognized regulator of proximal ammonia metabolism. The kidney consequences of its loss of function in mice support the proposal for KCNJ15 as a molecular basis for human isolated proximal renal tubular acidosis.
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20
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Kashoor I, Batlle D. Proximal renal tubular acidosis with and without Fanconi syndrome. Kidney Res Clin Pract 2019; 38:267-281. [PMID: 31474092 PMCID: PMC6727890 DOI: 10.23876/j.krcp.19.056] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 06/13/2019] [Accepted: 06/19/2019] [Indexed: 01/02/2023] Open
Abstract
Proximal renal tubular acidosis (RTA) is caused by a defect in bicarbonate (HCO3−) reabsorption in the kidney proximal convoluted tubule. It usually manifests as normal anion-gap metabolic acidosis due to HCO3− wastage. In a normal kidney, the thick ascending limb of Henle’s loop and more distal nephron segments reclaim all of the HCO3− not absorbed by the proximal tubule. Bicarbonate wastage seen in type II RTA indicates that the proximal tubular defect is severe enough to overwhelm the capacity for HCO3− reabsorption beyond the proximal tubule. Proximal RTA can occur as an isolated syndrome or with other impairments in proximal tubular functions under the spectrum of Fanconi syndrome. Fanconi syndrome, which is characterized by a defect in proximal tubular reabsorption of glucose, amino acids, uric acid, phosphate, and HCO3−, can occur due to inherited or acquired causes. Primary inherited Fanconi syndrome is caused by a mutation in the sodium-phosphate cotransporter (NaPi-II) in the proximal tubule. Recent studies have identified new causes of Fanconi syndrome due to mutations in the EHHADH and the HNF4A genes. Fanconi syndrome can also be one of many manifestations of various inherited systemic diseases, such as cystinosis. Many of the acquired causes of Fanconi syndrome with or without proximal RTA are drug-induced, with the list of causative agents increasing as newer drugs are introduced for clinical use, mainly in the oncology field.
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Affiliation(s)
- Ibrahim Kashoor
- Division of Nephrology and Hypertension, Department of Medicine, The Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Daniel Batlle
- Division of Nephrology and Hypertension, Department of Medicine, The Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
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21
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Tanikawa C, Kamatani Y, Terao C, Usami M, Takahashi A, Momozawa Y, Suzuki K, Ogishima S, Shimizu A, Satoh M, Matsuo K, Mikami H, Naito M, Wakai K, Yamaji T, Sawada N, Iwasaki M, Tsugane S, Kohri K, Yu ASL, Yasui T, Murakami Y, Kubo M, Matsuda K. Novel Risk Loci Identified in a Genome-Wide Association Study of Urolithiasis in a Japanese Population. J Am Soc Nephrol 2019; 30:855-864. [PMID: 30975718 DOI: 10.1681/asn.2018090942] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 02/08/2019] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND A family history of urolithiasis is associated with a more than doubling of urolithiasis risk, and a twin study estimating 56% heritability of the condition suggests a pivotal role for host genetic factors. However, previous genome-wide association studies (GWAS) have identified only six risk-related loci. METHODS To identify novel urolithiasis-related loci in the Japanese population, we performed a large-scale GWAS of 11,130 cases and 187,639 controls, followed by a replication analysis of 2289 cases and 3817 controls. Diagnosis of urolithiasis was confirmed either by a clinician or using medical records or self-report. We also assessed the association of urolithiasis loci with 16 quantitative traits, including metabolic, kidney-related, and electrolyte traits (such as body mass index, lipid storage, eGFR, serum uric acid, and serum calcium), using up to 160,000 samples from BioBank Japan. RESULTS The analysis identified 14 significant loci, including nine novel loci. Ten regions showed a significant association with at least one quantitative trait, including metabolic, kidney-related, and electrolyte traits, suggesting a common genetic basis for urolithiasis and these quantitative traits. Four novel loci were related to metabolic traits, obesity, hypertriglyceridemia, or hyperuricemia. The remaining ten loci were associated with kidney- or electrolyte-related traits; these may affect crystallization. Weighted genetic risk score analysis indicated that the highest risk group (top 20%) showed an odds ratio of 1.71 (95% confidence interval, 1.42 to 2.06) - 2.13 (95% confidence interval, 2.00 to 2.27) compared with the reference group (bottom 20%). CONCLUSIONS Our findings provide evidence that host genetic factors related to regulation of metabolic and crystallization pathways contribute to the development of urolithiasis.
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Affiliation(s)
| | - Yoichiro Kamatani
- Division of Genomic Medicine, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Chikashi Terao
- Division of Genomic Medicine, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Masayuki Usami
- Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Atsushi Takahashi
- Division of Genomic Medicine, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan.,Department of Genomic Medicine, Research Institute, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Yukihide Momozawa
- Division of Genomic Medicine, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Kichiya Suzuki
- Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan
| | - Soichi Ogishima
- Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan
| | - Atsushi Shimizu
- Iwate Tohoku Medical Megabank Organization, Iwate Medical University, Iwate, Japan
| | - Mamoru Satoh
- Iwate Tohoku Medical Megabank Organization, Iwate Medical University, Iwate, Japan
| | - Keitaro Matsuo
- Division of Cancer Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya, Japan.,Department of Epidemiology and
| | - Haruo Mikami
- Cancer Prevention Center, Chiba Cancer Center Research Institute, Chiba, Japan
| | - Mariko Naito
- Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Aichi, Japan.,Department of Oral Epidemiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Kenji Wakai
- Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Aichi, Japan
| | | | | | | | - Shoichiro Tsugane
- Center for Public Health Sciences, National Cancer Center, Tokyo, Japan; and
| | - Kenjiro Kohri
- Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Alan S L Yu
- Division of Nephrology and Hypertension and.,The Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas
| | - Takahiro Yasui
- Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | | | - Michiaki Kubo
- Division of Genomic Medicine, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Koichi Matsuda
- Laboratory of Clinical Genome Sequencing, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan;
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22
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Ahluwalia TS, Schulz CA, Waage J, Skaaby T, Sandholm N, van Zuydam N, Charmet R, Bork-Jensen J, Almgren P, Thuesen BH, Bedin M, Brandslund I, Christensen CK, Linneberg A, Ahlqvist E, Groop PH, Hadjadj S, Tregouet DA, Jørgensen ME, Grarup N, Pedersen O, Simons M, Groop L, Orho-Melander M, McCarthy MI, Melander O, Rossing P, Kilpeläinen TO, Hansen T. A novel rare CUBN variant and three additional genes identified in Europeans with and without diabetes: results from an exome-wide association study of albuminuria. Diabetologia 2019; 62:292-305. [PMID: 30547231 PMCID: PMC6323095 DOI: 10.1007/s00125-018-4783-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 10/22/2018] [Indexed: 01/06/2023]
Abstract
AIMS/HYPOTHESIS Identifying rare coding variants associated with albuminuria may open new avenues for preventing chronic kidney disease and end-stage renal disease, which are highly prevalent in individuals with diabetes. Efforts to identify genetic susceptibility variants for albuminuria have so far been limited, with the majority of studies focusing on common variants. METHODS We performed an exome-wide association study to identify coding variants in a two-stage (discovery and replication) approach. Data from 33,985 individuals of European ancestry (15,872 with and 18,113 without diabetes) and 2605 Greenlanders were included. RESULTS We identified a rare (minor allele frequency [MAF]: 0.8%) missense (A1690V) variant in CUBN (rs141640975, β = 0.27, p = 1.3 × 10-11) associated with albuminuria as a continuous measure in the combined European meta-analysis. The presence of each rare allele of the variant was associated with a 6.4% increase in albuminuria. The rare CUBN variant had an effect that was three times stronger in individuals with type 2 diabetes compared with those without (pinteraction = 7.0 × 10-4, β with diabetes = 0.69, β without diabetes = 0.20) in the discovery meta-analysis. Gene-aggregate tests based on rare and common variants identified three additional genes associated with albuminuria (HES1, CDC73 and GRM5) after multiple testing correction (pBonferroni < 2.7 × 10-6). CONCLUSIONS/INTERPRETATION The current study identifies a rare coding variant in the CUBN locus and other potential genes associated with albuminuria in individuals with and without diabetes. These genes have been implicated in renal and cardiovascular dysfunction. The findings provide new insights into the genetic architecture of albuminuria and highlight target genes and pathways for the prevention of diabetes-related kidney disease.
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Affiliation(s)
- Tarunveer S Ahluwalia
- Steno Diabetes Center Copenhagen, Niels Steensens Vej 2, 2820, Gentofte, Denmark.
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
- Copenhagen Prospective Studies on Asthma in Childhood, Gentofte and Herlev Hospital, University of Copenhagen, Copenhagen, Denmark.
| | | | - Johannes Waage
- Copenhagen Prospective Studies on Asthma in Childhood, Gentofte and Herlev Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Tea Skaaby
- Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, Capital Region, Copenhagen, Denmark
| | - Niina Sandholm
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, Helsinki, Finland
- Abdominal Center, Nephrology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Research Programs Unit, Diabetes and Obesity, University of Helsinki, Helsinki, Finland
| | - Natalie van Zuydam
- Wellcome Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Romain Charmet
- Inserm UMR-S 1166, Sorbonne Universités, UPMC Université Paris, Paris, France
| | - Jette Bork-Jensen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Peter Almgren
- Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
| | - Betina H Thuesen
- Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, Capital Region, Copenhagen, Denmark
| | - Mathilda Bedin
- Paris Descartes University-Sorbonne Paris Cité, Imagine Institute, Paris, France
| | - Ivan Brandslund
- Department of Clinical Immunology and Biochemistry, Lillebaelt Hospital, Vejle, Denmark
| | - Cramer K Christensen
- Department of Internal Medicine and Endocrinology, Lillebaelt Hospital, Vejle, Denmark
| | - Allan Linneberg
- Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, Capital Region, Copenhagen, Denmark
| | - Emma Ahlqvist
- Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
| | - Per-Henrik Groop
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, Helsinki, Finland
- Abdominal Center, Nephrology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Research Programs Unit, Diabetes and Obesity, University of Helsinki, Helsinki, Finland
- Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Samy Hadjadj
- L'institut du thorax, Department of Endocrinology, CIC 1413 INSERM, CHU Nantes, Nantes, France
| | | | - Marit E Jørgensen
- Steno Diabetes Center Copenhagen, Niels Steensens Vej 2, 2820, Gentofte, Denmark
- National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark
| | - Niels Grarup
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Oluf Pedersen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Matias Simons
- Paris Descartes University-Sorbonne Paris Cité, Imagine Institute, Paris, France
| | - Leif Groop
- Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | | | - Mark I McCarthy
- Wellcome Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Olle Melander
- Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
| | - Peter Rossing
- Steno Diabetes Center Copenhagen, Niels Steensens Vej 2, 2820, Gentofte, Denmark
- University of Copenhagen, Copenhagen, Denmark
| | - Tuomas O Kilpeläinen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torben Hansen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
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Rajkumar P, Pluznick JL. Acid-base regulation in the renal proximal tubules: using novel pH sensors to maintain homeostasis. Am J Physiol Renal Physiol 2018; 315:F1187-F1190. [PMID: 30066586 DOI: 10.1152/ajprenal.00185.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The kidneys play a critical role in precisely regulating the composition of the plasma to maintain homeostasis. To achieve this, the kidneys must be able to accurately determine or "sense" the concentration of a wide variety of substances and to make adjustments accordingly. Kidneys face a key challenge in the arena of pH balance, as there is a particularly narrow range over which plasma pH varies in a healthy subject (7.35-7.45) and this pH must constantly be protected against a variety of onslaughts (changes in diet, activity, and even elevation). The proximal tubule, the first segment to come into contact with the forming urine, plays an important role in helping the kidneys to maintain pH homeostasis. Recent studies have identified a number of novel proximal tubule proteins and signaling pathways that work to sense changes in pH and subsequently modulate renal pH regulation. In this review, we will highlight the role of novel players in acid-base homeostasis in the proximal tubule.
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Affiliation(s)
- Premraj Rajkumar
- Department of Physiology, Johns Hopkins University , Baltimore, Maryland.,Recursion Pharmaceuticals, Salt Lake City, Utah
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24
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Kurtz I. Renal Tubular Acidosis: H +/Base and Ammonia Transport Abnormalities and Clinical Syndromes. Adv Chronic Kidney Dis 2018; 25:334-350. [PMID: 30139460 PMCID: PMC6128697 DOI: 10.1053/j.ackd.2018.05.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Renal tubular acidosis (RTA) represents a group of diseases characterized by (1) a normal anion gap metabolic acidosis; (2) abnormalities in renal HCO3- absorption or new renal HCO3- generation; (3) changes in renal NH4+, Ca2+, K+, and H2O homeostasis; and (4) extrarenal manifestations that provide etiologic diagnostic clues. The focus of this review is to give a general overview of the pathogenesis of the various clinical syndromes causing RTA with a particular emphasis on type I (hypokalemic distal RTA) and type II (proximal) RTA while reviewing their pathogenesis from a physiological "bottom-up" approach. In addition, the factors involved in the generation of metabolic acidosis in both type I and II RTA are reviewed highlighting the importance of altered renal ammonia production/partitioning and new HCO3- generation. Our understanding of the underlying tubular transport and extrarenal abnormalities has significantly improved since the first recognition of RTA as a clinical entity because of significant advances in clinical acid-base chemistry, whole tubule and single-cell H+/base transport, and the molecular characterization of the various transporters and channels that are functionally affected in patients with RTA. Despite these advances, additional studies are needed to address the underlying mechanisms involved in hypokalemia, altered ammonia production/partitioning, hypercalciuria, nephrocalcinosis, cystic abnormalities, and CKD progression in these patients.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, and Brain Research Institute, UCLA, Los Angeles, CA.
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25
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Parker MD. Mouse models of SLC4-linked disorders of HCO 3--transporter dysfunction. Am J Physiol Cell Physiol 2018; 314:C569-C588. [PMID: 29384695 DOI: 10.1152/ajpcell.00301.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The SLC4 family Cl-/[Formula: see text] cotransporters (NBCe1, NBCe2, NBCn1, and NBCn2) contribute to a variety of vital physiological processes including pH regulation and epithelial fluid secretion. Accordingly, their dysfunction can have devastating effects. Disorders such as epilepsy, hemolytic anemia, glaucoma, hearing loss, osteopetrosis, and renal tubular acidosis are all genetically linked to SLC4-family gene loci. This review summarizes how studies of Slc4-modified mice have enhanced our understanding of the etiology of SLC4-linked pathologies and the interpretation of genetic linkage studies. The review also surveys the novel disease signs exhibited by Slc4-modified mice which could either be considered to presage their description in humans, or to highlight interspecific differences. Finally, novel Slc4-modified mouse models are proposed, the study of which may further our understanding of the basis and treatment of SLC4-linked disorders of [Formula: see text]-transporter dysfunction.
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Affiliation(s)
- Mark D Parker
- Department of Physiology and Biophysics, The State University of New York: The University at Buffalo , Buffalo, New York.,Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York , Buffalo, New York.,State University of New York Eye Institutes, University at Buffalo: The State University of New York , Buffalo, New York
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26
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O'Grady SM. Taking intestinal anion secretion to TASK: a role for K2P channels in cyclic AMP-regulated anion secretion. J Physiol 2017; 596:359-360. [PMID: 29205365 DOI: 10.1113/jp275567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Scott M O'Grady
- Departments of Animal Science, Integrative Biology and Physiology, University of Minnesota, 480 Haecker Hall, 1364 Eckles Avenue, St Paul, MN, 55108, USA
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27
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Julio-Kalajzić F, Villanueva S, Burgos J, Ojeda M, Cid LP, Jentsch TJ, Sepúlveda FV. K 2P TASK-2 and KCNQ1-KCNE3 K + channels are major players contributing to intestinal anion and fluid secretion. J Physiol 2017; 596:393-407. [PMID: 29143340 DOI: 10.1113/jp275178] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 11/08/2017] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS K+ channels are important in intestinal epithelium as they ensure the ionic homeostasis and electrical potential of epithelial cells during anion and fluid secretion. Intestinal epithelium cAMP-activated anion secretion depends on the activity of the (also cAMP dependent) KCNQ1-KCNE3 K+ channel, but the secretory process survives after genetic inactivation of the K+ channel in the mouse. Here we use double mutant mice to investigate which alternative K+ channels come into action to compensate for the absence of KCNQ1-KCNE3 K+ channels. Our data establish that whilst Ca2+ -activated KCa 3.1 channels are not involved, K2P two-pore domain TASK-2 K+ channels are major players providing an alternative conductance to sustain the intestinal secretory process. Work with double mutant mice lacking both TASK-2 and KCNQ1-KCNE3 channels nevertheless points to yet-unidentified K+ channels that contribute to the robustness of the cAMP-activated anion secretion process. ABSTRACT Anion and fluid secretion across the intestinal epithelium, a process altered in cystic fibrosis and secretory diarrhoea, is mediated by cAMP-activated CFTR Cl- channels and requires the simultaneous activity of basolateral K+ channels to maintain cellular ionic homeostasis and membrane potential. This function is fulfilled by the cAMP-activated K+ channel formed by the association of pore-forming KCNQ1 with its obligatory KCNE3 β-subunit. Studies using mice show sizeable cAMP-activated intestinal anion secretion in the absence of either KCNQ1 or KCNE3 suggesting that an alternative K+ conductance must compensate for the loss of KCNQ1-KCNE3 activity. We used double mutant mouse and pharmacological approaches to identify such a conductance. Ca2+ -dependent anion secretion can also be supported by Ca2+ -dependent KCa 3.1 channels after independent CFTR activation, but cAMP-dependent anion secretion is not further decreased in the combined absence of KCa 3.1 and KCNQ1-KCNE3 K+ channel activity. We show that the K2P K+ channel TASK-2 is expressed in the epithelium of the small and large intestine. Tetrapentylammonium, a TASK-2 inhibitor, abolishes anion secretory current remaining in the absence of KCNQ1-KCNE3 activity. A double mutant mouse lacking both KCNQ1-KCNE3 and TASK-2 showed a much reduced cAMP-mediated anion secretion compared to that observed in the single KCNQ1-KCNE3 deficient mouse. We conclude that KCNQ1-KCNE3 and TASK-2 play major roles in the intestinal anion and fluid secretory phenotype. The persistence of an, admittedly reduced, secretory activity in the absence of these two conductances suggests that further additional K+ channel(s) as yet unidentified contribute to the robustness of the intestinal anion secretory process.
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Affiliation(s)
| | - Sandra Villanueva
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Johanna Burgos
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Margarita Ojeda
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - L Pablo Cid
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
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28
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Phosphatidylinositol (4,5)-bisphosphate dynamically regulates the K 2P background K + channel TASK-2. Sci Rep 2017; 7:45407. [PMID: 28358046 PMCID: PMC5371824 DOI: 10.1038/srep45407] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 02/23/2017] [Indexed: 12/22/2022] Open
Abstract
Two-pore domain K2P K+ channels responsible for the background K+ conductance and the resting membrane potential, are also finely regulated by a variety of chemical, physical and physiological stimuli. Hormones and transmitters acting through Gq protein-coupled receptors (GqPCRs) modulate the activity of various K2P channels but the signalling involved has remained elusive, in particular whether dynamic regulation by membrane PI(4,5)P2, common among other classes of K+ channels, affects K2P channels is controversial. Here we show that K2P K+ channel TASK-2 requires PI(4,5)P2 for activity, a dependence that accounts for its run down in the absence of intracellular ATP and its full recovery by addition of exogenous PI(4,5)P2, its inhibition by low concentrations of polycation PI scavengers, and inhibition by PI(4,5)P2 depletion from the membrane. Comprehensive mutagenesis suggests that PI(4,5)P2 interaction with TASK-2 takes place at C-terminus where three basic aminoacids are identified as being part of a putative binding site.
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29
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Bai X, Lacey HA, Greenwood SL, Baker PN, Turner MA, Sibley CP, Fyfe GK. TASK Channel Expression in Human Placenta and Cytotrophoblast Cells. ACTA ACUST UNITED AC 2016; 13:30-9. [PMID: 16378911 DOI: 10.1016/j.jsgi.2005.10.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Indexed: 10/25/2022]
Abstract
OBJECTIVE The multinucleate syncytiotrophoblast is the transporting epithelium of the human placental villus, formed throughout pregnancy by fusion and differentiation of underlying mononucleate cytotrophoblast cells. Similar to other epithelia, K+ channels will impact on syncytiotrophoblast transport properties during its development and differentiation. Therefore we investigated expression and activity of the two-pore domain K+ channels TASK1 and 2 in relation to gestation and differentiation, using villous tissue from first and third trimester and cultured cytotrophoblast cells at mononucleate and multinucleate stages of culture. METHODS Quantitative real-time polymerase chain reaction (PCR), immunofluorescence, and 86Rb+ (K) efflux were used to investigate TASK channel expression and function. RESULTS TASK2 mRNA expression was higher in first trimester than term (10 to 13 vs 38 to 40 weeks, P < .05). Other K+ alpha-subunit mRNAs, including TASK1, remained unaltered but the regulatory BKCa beta-subunit, like TASK2, was higher in first trimester than term (P < .001). Immunofluorescence showed that TASK2 had an intracellular localization within the trophoblast of first trimester villi but was less abundant and restricted to stem villi at term. TASK2 also showed intracellular localization in mononucleate cytotrophoblast cells in culture and expression was lost with multinucleation. By contrast, TASK1 was localised, independently of cell nucleation, to cytotrophoblast cell plasma membranes. 86Rb+ (K) efflux was measured from multinucleated cytotrophoblast cells. Both basal and pH 8.0-stimulated efflux was inhibited by the TASK1 antagonist anandamide (n = 5 for both conditions; P < .01 and P < .001, respectively). CONCLUSION TASK1 and 2 are expressed in placental trophoblast cells and TASK1 activity may have a role in regulating syncytiotrophoblast homeostasis and/or solute transport functions.
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Affiliation(s)
- Xilian Bai
- Maternal and Fetal Health Research Centre, Division of Human Development, The Medical School, University of Manchester, St Mary's Hospital, Manchester, United Kingdom
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30
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Afzali AM, Ruck T, Herrmann AM, Iking J, Sommer C, Kleinschnitz C, Preuβe C, Stenzel W, Budde T, Wiendl H, Bittner S, Meuth SG. The potassium channels TASK2 and TREK1 regulate functional differentiation of murine skeletal muscle cells. Am J Physiol Cell Physiol 2016; 311:C583-C595. [PMID: 27488672 DOI: 10.1152/ajpcell.00363.2015] [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: 12/21/2015] [Accepted: 08/02/2016] [Indexed: 12/18/2022]
Abstract
Two-pore domain potassium (K2P) channels influence basic cellular parameters such as resting membrane potential, cellular excitability, or intracellular Ca2+-concentration [Ca2+]i While the physiological importance of K2P channels in different organ systems (e.g., heart, central nervous system, or immune system) has become increasingly clear over the last decade, their expression profile and functional role in skeletal muscle cells (SkMC) remain largely unknown. The mouse SkMC cell line C2C12, wild-type mouse muscle tissue, and primary mouse muscle cells (PMMs) were analyzed using quantitative PCR, Western blotting, and immunohistochemical stainings as well as functional analysis including patch-clamp measurements and Ca2+ imaging. Mouse SkMC express TWIK-related acid-sensitive K+ channel (TASK) 2, TWIK-related K+ channel (TREK) 1, TREK2, and TWIK-related arachidonic acid stimulated K+ channel (TRAAK). Except TASK2 all mentioned channels were upregulated in vitro during differentiation from myoblasts to myotubes. TASK2 and TREK1 were also functionally expressed and upregulated in PMMs isolated from mouse muscle tissue. Inhibition of TASK2 and TREK1 during differentiation revealed a morphological impairment of myoblast fusion accompanied by a downregulation of maturation markers. TASK2 and TREK1 blockade led to a decreased K+ outward current and a decrease of ACh-dependent Ca2+ influx in C2C12 cells as potential underlying mechanisms. K2P-channel expression was also detected in human muscle tissue by immunohistochemistry pointing towards possible relevance for human muscle cell maturation and function. In conclusion, our findings for the first time demonstrate the functional expression of TASK2 and TREK1 in muscle cells with implications for differentiation processes warranting further investigations in physiologic and pathophysiologic scenarios.
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Affiliation(s)
- Ali M Afzali
- Department of Neurology, University of Münster, Münster, Germany
| | - Tobias Ruck
- Department of Neurology, University of Münster, Münster, Germany;
| | | | - Janette Iking
- Department of Neurology, University of Münster, Münster, Germany
| | - Claudia Sommer
- Department of Neurology, University Hospital of Würzburg, Würzburg, Germany
| | | | - Corinna Preuβe
- Department of Neuropathology, Charité-Universitätsmedizin, Berlin, Germany
| | - Werner Stenzel
- Department of Neuropathology, Charité-Universitätsmedizin, Berlin, Germany
| | - Thomas Budde
- Institute of Physiology I, University of Münster, Münster, Germany; and
| | - Heinz Wiendl
- Department of Neurology, University of Münster, Münster, Germany
| | - Stefan Bittner
- Department of Neurology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Sven G Meuth
- Department of Neurology, University of Münster, Münster, Germany
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31
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Niemeyer MI, Cid LP, González W, Sepúlveda FV. Gating, Regulation, and Structure in K2P K+ Channels: In Varietate Concordia? Mol Pharmacol 2016; 90:309-17. [DOI: 10.1124/mol.116.103895] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 05/31/2016] [Indexed: 11/22/2022] Open
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32
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Reed AP, Bucci G, Abd-Wahab F, Tucker SJ. Dominant-Negative Effect of a Missense Variant in the TASK-2 (KCNK5) K+ Channel Associated with Balkan Endemic Nephropathy. PLoS One 2016; 11:e0156456. [PMID: 27228168 PMCID: PMC4882002 DOI: 10.1371/journal.pone.0156456] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 05/14/2016] [Indexed: 11/20/2022] Open
Abstract
TASK-2, a member of the Two-Pore Domain (K2P) subfamily of K+ channels, is encoded by the KCNK5 gene. The channel is expressed primarily in renal epithelial tissues and a potentially deleterious missense variant in KCNK5 has recently been shown to be prevalent amongst patients predisposed to the development of Balkan Endemic Nephropathy (BEN), a chronic tubulointerstitial renal disease of unknown etiology. In this study we show that this variant (T108P) results in a complete loss of channel function and is associated with a major reduction in TASK-2 channel subunits at the cell surface. Furthermore, these mutant subunits have a suppressive or ‘dominant-negative’ effect on channel function when coexpressed with wild-type subunits. This missense variant is located at the extracellular surface of the M2 transmembrane helix and by using a combination of structural modelling and further functional analysis we also show that this highly-conserved threonine residue is critical for the correct function of other K2P channels. These results therefore provide further structural and functional insights into the possible pathophysiological effects of this missense variant in TASK-2.
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Affiliation(s)
- Alan P. Reed
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Giovanna Bucci
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Firdaus Abd-Wahab
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Stephen J. Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, United Kingdom
- * E-mail:
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33
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Veale EL, Mathie A. Aristolochic acid, a plant extract used in the treatment of pain and linked to Balkan endemic nephropathy, is a regulator of K2P channels. Br J Pharmacol 2016; 173:1639-52. [PMID: 26914156 PMCID: PMC4842925 DOI: 10.1111/bph.13465] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 02/08/2016] [Accepted: 02/15/2016] [Indexed: 01/08/2023] Open
Abstract
Background and Purpose Aristolochic acid (AristA) is found in plants used in traditional medicines to treat pain. We investigated the action of AristA on TREK and TRESK, potassium (K2P) channels, which are potential therapeutic targets in pain. Balkan endemic nephropathy (BEN) is a renal disease associated with AristA consumption. A mutation of TASK‐2 (K2P5.1) channels (T108P) is seen in some patients susceptible to BEN, so we investigated how both this mutation and AristA affected TASK‐2 channels. Experimental Approach Currents through wild‐type and mutated human K2P channels expressed in tsA201 cells were measured using whole‐cell patch‐clamp recordings in the presence and absence of AristA. Key Results TREK‐1‐ and TREK‐2‐mediated currents were enhanced by AristA (100 μM), whereas TRESK was inhibited. Inhibition of TRESK did not depend on the phosphorylation of key intracellular serines but was completely blocked by mutation of bulky residues in the inner pore (F145A_F352A). The TASK‐2_T108P mutation markedly reduced both current density and ion selectivity. A related mutation (T108C) had similar but less marked effects. External alkalization and application of flufenamic acid enhanced TASK‐2 and TASK‐2_T108C current but did not affect TASK‐2_T108P current. AristA (300 μM) produced a modest enhancement of TASK‐2 current. Conclusions and Implications Enhancement of TREK‐1 and TREK‐2 and inhibition of TRESK by AristA may contribute to therapeutically useful effects of this compound in pain. Whilst AristA is unlikely to interact directly with TASK‐2 channels in BEN, loss of functional TASK‐2 channels may indirectly increase susceptibility to AristA toxicity.
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Affiliation(s)
- Emma L Veale
- Medway School of Pharmacy, University of Kent, Kent, UK
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34
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Cui CY, Sima J, Yin M, Michel M, Kunisada M, Schlessinger D. Identification of potassium and chloride channels in eccrine sweat glands. J Dermatol Sci 2015; 81:129-31. [PMID: 26627722 DOI: 10.1016/j.jdermsci.2015.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 10/16/2015] [Accepted: 11/04/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Chang-Yi Cui
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd., Suite 100, Baltimore, MD, USA.
| | - Jian Sima
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd., Suite 100, Baltimore, MD, USA
| | - Mingzhu Yin
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd., Suite 100, Baltimore, MD, USA
| | - Marc Michel
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd., Suite 100, Baltimore, MD, USA
| | - Makoto Kunisada
- Division of Dermatology, Department of Internal Related, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - David Schlessinger
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 251 Bayview Blvd., Suite 100, Baltimore, MD, USA
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35
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Cazals Y, Bévengut M, Zanella S, Brocard F, Barhanin J, Gestreau C. KCNK5 channels mostly expressed in cochlear outer sulcus cells are indispensable for hearing. Nat Commun 2015; 6:8780. [PMID: 26549439 PMCID: PMC4659937 DOI: 10.1038/ncomms9780] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/01/2015] [Indexed: 01/03/2023] Open
Abstract
In the cochlea, K(+) is essential for mechano-electrical transduction. Here, we explore cochlear structure and function in mice lacking K(+) channels of the two-pore domain family. A profound deafness associated with a decrease in endocochlear potential is found in adult Kcnk5(-/-) mice. Hearing occurs around postnatal day 19 (P19), and completely disappears 2 days later. At P19, Kcnk5(-/-) mice have a normal endolymphatic [K(+)] but a partly lowered endocochlear potential. Using Lac-Z as a gene reporter, KCNK5 is mainly found in outer sulcus Claudius', Boettcher's and root cells. Low levels of expression are also seen in the spiral ganglion, Reissner's membrane and stria vascularis. Essential channels (KCNJ10 and KCNQ1) contributing to K(+) secretion in stria vascularis have normal expression in Kcnk5(-/-) mice. Thus, KCNK5 channels are indispensable for the maintenance of hearing. Among several plausible mechanisms, we emphasize their role in K(+) recycling along the outer sulcus lateral route.
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Affiliation(s)
- Yves Cazals
- Laboratoire de Neurosciences Intégratives et Adaptatives (UMR7260), Fédération de Recherche 3C (Cerveau, Comportement, Cognition), Aix-Marseille-Université and CNRS, Marseille 13331, France
| | - Michelle Bévengut
- Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (UMR7286), Aix-Marseille-Université and CNRS, Marseille 13344, France
| | - Sébastien Zanella
- Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (UMR7286), Aix-Marseille-Université and CNRS, Marseille 13344, France
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille 13005, France
| | - Frédéric Brocard
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille 13005, France
| | - Jacques Barhanin
- Laboratoire de Physio-Médecine Moléculaire (UMR7370), Université de Nice-Sophia Antipolis and CNRS, Nice 06107, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
| | - Christian Gestreau
- Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (UMR7286), Aix-Marseille-Université and CNRS, Marseille 13344, France
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36
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Bittner S, Bobak N, Hofmann MS, Schuhmann MK, Ruck T, Göbel K, Brück W, Wiendl H, Meuth SG. Murine K2P5.1 Deficiency Has No Impact on Autoimmune Neuroinflammation due to Compensatory K2P3.1- and KV1.3-Dependent Mechanisms. Int J Mol Sci 2015. [PMID: 26213925 PMCID: PMC4581175 DOI: 10.3390/ijms160816880] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lymphocytes express potassium channels that regulate physiological cell functions, such as activation, proliferation and migration. Expression levels of K2P5.1 (TASK2; KCNK5) channels belonging to the family of two-pore domain potassium channels have previously been correlated to the activity of autoreactive T lymphocytes in patients with multiple sclerosis and rheumatoid arthritis. In humans, K2P5.1 channels are upregulated upon T cell stimulation and influence T cell effector functions. However, a further clinical translation of targeting K2P5.1 is currently hampered by a lack of highly selective inhibitors, making it necessary to evaluate the impact of KCNK5 in established preclinical animal disease models. We here demonstrate that K2P5.1 knockout (K2P5.1−/−) mice display no significant alterations concerning T cell cytokine production, proliferation rates, surface marker molecules or signaling pathways. In an experimental model of autoimmune neuroinflammation, K2P5.1−/− mice show a comparable disease course to wild-type animals and no major changes in the peripheral immune system or CNS compartment. A compensatory upregulation of the potassium channels K2P3.1 and KV1.3 seems to counterbalance the deletion of K2P5.1. As an alternative model mimicking autoimmune neuroinflammation, experimental autoimmune encephalomyelitis in the common marmoset has been proposed, especially for testing the efficacy of new potential drugs. Initial experiments show that K2P5.1 is functionally expressed on marmoset T lymphocytes, opening up the possibility for assessing future K2P5.1-targeting drugs.
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Affiliation(s)
- Stefan Bittner
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany.
| | - Nicole Bobak
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, Valbonne 06560, France.
| | - Majella-Sophie Hofmann
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany.
| | | | - Tobias Ruck
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany.
| | - Kerstin Göbel
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany.
| | - Wolfgang Brück
- Department of Neuropathology, University Medical Center, Georg August University, Göttingen 37073, Germany.
| | - Heinz Wiendl
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany.
| | - Sven G Meuth
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany.
- Department of Physiology I-Neuropathophysiology, University of Münster, Münster 48149, Germany .
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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Sun X, Stephens L, DuBose TD, Petrovic S. Adaptation by the collecting duct to an exogenous acid load is blunted by deletion of the proton-sensing receptor GPR4. Am J Physiol Renal Physiol 2015; 309:F120-36. [DOI: 10.1152/ajprenal.00507.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 05/05/2015] [Indexed: 12/14/2022] Open
Abstract
We previously reported that the deletion of the pH sensor GPR4 causes a non-gap metabolic acidosis and defective net acid excretion (NAE) in the GPR4 knockout mouse (GPR4−/−) (Sun X, Yang LV, Tiegs BC, Arend LJ, McGraw DW, Penn RB, and Petrovic S. J Am Soc Nephrol 21: 1745–1755, 2010). Since the major regulatory site of NAE in the kidney is the collecting duct (CD), we examined acid-base transport proteins in intercalated cells (ICs) of the CD and found comparable mRNA expression of kidney anion exchanger 1 (kAE1), pendrin, and the a4 subunit of H+-ATPase in GPR4−/− vs. +/+. However, NH4Cl loading elicited adaptive doubling of AE1 mRNA in GPR4+/+, but a 50% less pronounced response in GPR4−/−. In GPR4+/+, NH4Cl loading evoked a cellular response characterized by an increase in AE1-labeled and a decrease in pendrin-labeled ICs similar to what was reported in rabbits and rats. This response did not occur in GPR4−/−. Microperfusion experiments demonstrated that the activity of the basolateral Cl−/HCO3− exchanger, kAE1, in CDs isolated from GPR4−/− failed to increase with NH4Cl loading, in contrast to the increase observed in GPR4+/+. Therefore, the deficiency of GPR4 blunted, but did not eliminate the adaptive response to an acid load, suggesting a compensatory response from other pH/CO2/bicarbonate sensors. Indeed, the expression of the calcium-sensing receptor (CaSR) was nearly doubled in GPR4−/− kidneys, in the absence of apparent disturbances of Ca2+ homeostasis. In summary, the expression and activity of the key transport proteins in GPR4−/− mice are consistent with spontaneous metabolic acidosis, but the adaptive response to a superimposed exogenous acid load is blunted and might be partially compensated for by CaSR.
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Affiliation(s)
- Xuming Sun
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Lisa Stephens
- Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Thomas D. DuBose
- Section on Nephrology, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Snezana Petrovic
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Section on Nephrology, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Claude D. Pepper Older Americans Independence Center, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston-Salem, North Carolina; and
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39
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Murayama T, Maruyama IN. Alkaline pH sensor molecules. J Neurosci Res 2015; 93:1623-30. [PMID: 26154399 DOI: 10.1002/jnr.23621] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/12/2015] [Accepted: 06/26/2015] [Indexed: 12/22/2022]
Abstract
Animals can survive only within a narrow pH range. This requires continual monitoring of environmental and body-fluid pH. Although a variety of acidic pH sensor molecules have been reported, alkaline pH sensor function is not well understood. This Review describes neuronal alkaline pH sensors, grouped according to whether they monitor extracellular or intracellular alkaline pH. Extracellular sensors include the receptor-type guanylyl cyclase, the insulin receptor-related receptor, ligand-gated Cl- channels, connexin hemichannels, two-pore-domain K+ channels, and transient receptor potential (TRP) channels. Intracellular sensors include TRP channels and gap junction channels. Identification of molecular mechanisms underlying alkaline pH sensing is crucial for understanding how animals respond to environmental alkaline pH and how body-fluid pH is maintained within a narrow range.
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Affiliation(s)
- Takashi Murayama
- Information Processing Biology Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Ichiro N Maruyama
- Information Processing Biology Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
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40
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Renigunta V, Schlichthörl G, Daut J. Much more than a leak: structure and function of K₂p-channels. Pflugers Arch 2015; 467:867-94. [PMID: 25791628 DOI: 10.1007/s00424-015-1703-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 11/27/2022]
Abstract
Over the last decade, we have seen an enormous increase in the number of experimental studies on two-pore-domain potassium channels (K2P-channels). The collection of reviews and original articles compiled for this special issue of Pflügers Archiv aims to give an up-to-date summary of what is known about the physiology and pathophysiology of K2P-channels. This introductory overview briefly describes the structure of K2P-channels and their function in different organs. Its main aim is to provide some background information for the 19 reviews and original articles of this special issue of Pflügers Archiv. It is not intended to be a comprehensive review; instead, this introductory overview focuses on some unresolved questions and controversial issues, such as: Do K2P-channels display voltage-dependent gating? Do K2P-channels contribute to the generation of action potentials? What is the functional role of alternative translation initiation? Do K2P-channels have one or two or more gates? We come to the conclusion that we are just beginning to understand the extremely complex regulation of these fascinating channels, which are often inadequately described as 'leak channels'.
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Affiliation(s)
- Vijay Renigunta
- Institute of Physiology and Pathophysiology, Marburg University, 35037, Marburg, Germany
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41
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Sepúlveda FV, Pablo Cid L, Teulon J, Niemeyer MI. Molecular aspects of structure, gating, and physiology of pH-sensitive background K2P and Kir K+-transport channels. Physiol Rev 2015; 95:179-217. [PMID: 25540142 DOI: 10.1152/physrev.00016.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
K(+) channels fulfill roles spanning from the control of excitability to the regulation of transepithelial transport. Here we review two groups of K(+) channels, pH-regulated K2P channels and the transport group of Kir channels. After considering advances in the molecular aspects of their gating based on structural and functional studies, we examine their participation in certain chosen physiological and pathophysiological scenarios. Crystal structures of K2P and Kir channels reveal rather unique features with important consequences for the gating mechanisms. Important tasks of these channels are discussed in kidney physiology and disease, K(+) homeostasis in the brain by Kir channel-equipped glia, and central functions in the hearing mechanism in the inner ear and in acid secretion by parietal cells in the stomach. K2P channels fulfill a crucial part in central chemoreception probably by virtue of their pH sensitivity and are central to adrenal secretion of aldosterone. Finally, some unorthodox behaviors of the selectivity filters of K2P channels might explain their normal and pathological functions. Although a great deal has been learned about structure, molecular details of gating, and physiological functions of K2P and Kir K(+)-transport channels, this has been only scratching at the surface. More molecular and animal studies are clearly needed to deepen our knowledge.
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Affiliation(s)
- Francisco V Sepúlveda
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - L Pablo Cid
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - Jacques Teulon
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - María Isabel Niemeyer
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
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42
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Feliciangeli S, Chatelain FC, Bichet D, Lesage F. The family of K2P channels: salient structural and functional properties. J Physiol 2015; 593:2587-603. [PMID: 25530075 DOI: 10.1113/jphysiol.2014.287268] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 12/10/2014] [Indexed: 12/11/2022] Open
Abstract
Potassium channels participate in many biological functions, from ion homeostasis to generation and modulation of the electrical membrane potential. They are involved in a large variety of diseases. In the human genome, 15 genes code for K(+) channels with two pore domains (K2P ). These channels form dimers of pore-forming subunits that produce background conductances finely regulated by a range of natural and chemical effectors, including signalling lipids, temperature, pressure, pH, antidepressants and volatile anaesthetics. Since the cloning of TWIK1, the prototypical member of this family, a lot of work has been carried out on their structure and biology. These studies are still in progress, but data gathered so far show that K2P channels are central players in many processes, including ion homeostasis, hormone secretion, cell development and excitability. A growing number of studies underline their implication in physiopathological mechanisms, such as vascular and pulmonary hypertension, cardiac arrhythmias, nociception, neuroprotection and depression. This review gives a synthetic view of the most noticeable features of these channels.
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Affiliation(s)
- Sylvain Feliciangeli
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Frank C Chatelain
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Delphine Bichet
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Florian Lesage
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
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Bayliss DA, Barhanin J, Gestreau C, Guyenet PG. The role of pH-sensitive TASK channels in central respiratory chemoreception. Pflugers Arch 2014; 467:917-29. [PMID: 25346157 DOI: 10.1007/s00424-014-1633-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 10/08/2014] [Accepted: 10/12/2014] [Indexed: 01/16/2023]
Abstract
A number of the subunits within the family of K2P background K(+) channels are sensitive to changes in extracellular pH in the physiological range, making them likely candidates to mediate various pH-dependent processes. Based on expression patterns within several brainstem neuronal cell groups that are believed to function in CO2/H(+) regulation of breathing, three TASK subunits-TASK-1, TASK-2, and TASK-3-were specifically hypothesized to contribute to this central respiratory chemoreflex. For the acid-sensitive TASK-1 and TASK-3 channels, despite widespread expression at multiple levels within the brainstem respiratory control system (including presumptive chemoreceptor populations), experiments in knockout mice provided no evidence for their involvement in CO2 regulation of breathing. By contrast, the alkaline-activated TASK-2 channel has a more restricted brainstem distribution and was localized to the Phox2b-expressing chemoreceptor neurons of the retrotrapezoid nucleus (RTN). Remarkably, in a Phox2b(27Ala/+) mouse genetic model of congenital central hypoventilation syndrome (CCHS) that is characterized by reduced central respiratory chemosensitivity, selective ablation of Phox2b-expressing RTN neurons was accompanied by a corresponding loss of TASK-2 expression. Furthermore, genetic deletion of TASK-2 blunted RTN neuronal pH sensitivity in vitro, reduced alkaline-induced respiratory network inhibition in situ and diminished the ventilatory response to CO2/H(+) in vivo. Notably, a subpopulation of RTN neurons from TASK-2(-/-) mice retained their pH sensitivity, at least in part due to a residual pH-sensitive background K(+) current, suggesting that other mechanisms (and perhaps other K2P channels) for RTN neuronal pH sensitivity are yet to be identified.
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Affiliation(s)
- Douglas A Bayliss
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, 22908-0735, USA,
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44
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López-Cayuqueo KI, Peña-Münzenmayer G, Niemeyer MI, Sepúlveda FV, Cid LP. TASK-2 K₂p K⁺ channel: thoughts about gating and its fitness to physiological function. Pflugers Arch 2014; 467:1043-53. [PMID: 25315981 DOI: 10.1007/s00424-014-1627-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 10/02/2014] [Accepted: 10/03/2014] [Indexed: 01/08/2023]
Abstract
TASK-2 (K2P5) was one of the earliest members of the K2P two-pore, four transmembrane domain K(+) channels to be identified. TASK-2 gating is controlled by changes in both extra- and intracellular pH through separate sensors: arginine 224 and lysine 245, located at the extra- and intracellular ends of transmembrane domain 4. TASK-2 is inhibited by a direct effect of CO2 and is regulated by and interacts with G protein subunits. TASK-2 takes part in regulatory adjustments and is a mediator in the chemoreception process in neurons of the retrotrapezoid nucleus where its pHi sensitivity could be important in regulating excitability and therefore signalling of the O2/CO2 status. Extracellular pH increases brought about by HCO3 (-) efflux from proximal tubule epithelial cells have been proposed to couple to TASK-2 activation to maintain electrochemical gradients favourable to HCO3 (-) reabsorption. We demonstrate that, as suspected previously, TASK-2 is expressed at the basolateral membrane of the same proximal tubule cells that express apical membrane Na(+)-H(+)-exchanger NHE-3 and basolateral membrane Na(+)-HCO3 (-) cotransporter NBCe1-A, the main components of the HCO3 (-) transport machinery. We also discuss critically the mechanism by which TASK-2 is modulated and impacts the process of HCO3 (-) reclaim by the proximal tubule epithelium, concluding that more than a mere shift in extracellular pH is probably involved.
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Affiliation(s)
- Karen I López-Cayuqueo
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, 5110466, Valdivia, Chile
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45
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Venglovecz V, Rakonczay Z, Gray MA, Hegyi P. Potassium channels in pancreatic duct epithelial cells: their role, function and pathophysiological relevance. Pflugers Arch 2014; 467:625-40. [PMID: 25074489 DOI: 10.1007/s00424-014-1585-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 07/09/2014] [Accepted: 07/18/2014] [Indexed: 12/14/2022]
Abstract
Pancreatic ductal epithelial cells play a fundamental role in HCO3 (-) secretion, a process which is essential for maintaining the integrity of the pancreas. Although several studies have implicated impaired HCO3 (-) and fluid secretion as a triggering factor in the development of pancreatitis, the mechanism and regulation of HCO3 (-) secretion is still not completely understood. To date, most studies on the ion transporters that orchestrate ductal HCO3 (-) secretion have focussed on the role of Cl(-)/HCO3 (-) exchangers and Cl(-) channels, whereas much less is known about the role of K(+) channels. However, there is growing evidence that many types of K(+) channels are present in ductal cells where they have an essential role in establishing and maintaining the electrochemical driving force for anion secretion. For this reason, strategies that increase K(+) channel function may help to restore impaired HCO3 (-) and fluid secretion, such as in pancreatitis, and therefore provide novel directions for future pancreatic therapy. In this review, our aims are to summarize the types of K(+) channels found in pancreatic ductal cells and to discuss their individual roles in ductal HCO3 (-) secretion. We will also describe how K(+) channels are involved in pathophysiological conditions and discuss how they could act as new molecular targets for the development of therapeutic approaches to treat pancreatic diseases.
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Affiliation(s)
- Viktória Venglovecz
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary,
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46
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Toncheva D, Mihailova-Hristova M, Vazharova R, Staneva R, Karachanak S, Dimitrov P, Simeonov V, Ivanov S, Balabanski L, Serbezov D, Malinov M, Stefanovic V, Čukuranović R, Polenakovic M, Jankovic-Velickovic L, Djordjevic V, Jevtovic-Stoimenov T, Plaseska-Karanfilska D, Galabov A, Djonov V, Dimova I. NGS nominated CELA1, HSPG2, and KCNK5 as candidate genes for predisposition to Balkan endemic nephropathy. BIOMED RESEARCH INTERNATIONAL 2014; 2014:920723. [PMID: 24949484 PMCID: PMC4052113 DOI: 10.1155/2014/920723] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 04/16/2014] [Accepted: 04/30/2014] [Indexed: 01/06/2023]
Abstract
Balkan endemic nephropathy (BEN) is a familial chronic tubulointerstitial disease with insidious onset and slow progression leading to terminal renal failure. The results of molecular biological investigations propose that BEN is a multifactorial disease with genetic predisposition to environmental risk agents. Exome sequencing of 22 000 genes with Illumina Nextera Exome Enrichment Kit was performed on 22 DNA samples (11 Bulgarian patients and 11 Serbian patients). Software analysis was performed via NextGene, Provean, and PolyPhen. The frequency of all annotated genetic variants with deleterious/damaging effect was compared with those of European populations. Then we focused on nonannotated variants (with no data available about them and not found in healthy Bulgarian controls). There is no statistically significant difference between annotated variants in BEN patients and European populations. From nonannotated variants with more than 40% frequency in both patients' groups, we nominated 3 genes with possible deleterious/damaging variants--CELA1, HSPG2, and KCNK5. Mutant genes (CELA1, HSPG2, and KCNK5) in BEN patients encode proteins involved in basement membrane/extracellular matrix and vascular tone, tightly connected to process of angiogenesis. We suggest that an abnormal process of angiogenesis plays a key role in the molecular pathogenesis of BEN.
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Affiliation(s)
- D. Toncheva
- Department of Medical Genetics, Medical University of Sofia, Zdrave Street 2, 1431 Sofia, Bulgaria
- Genomics Laboratory of Malinov Clinic, 1620 Sofia, Bulgaria
| | - M. Mihailova-Hristova
- Department of Medical Genetics, Medical University of Sofia, Zdrave Street 2, 1431 Sofia, Bulgaria
| | - R. Vazharova
- Genomics Laboratory of Malinov Clinic, 1620 Sofia, Bulgaria
| | - R. Staneva
- Department of Medical Genetics, Medical University of Sofia, Zdrave Street 2, 1431 Sofia, Bulgaria
| | - S. Karachanak
- Department of Medical Genetics, Medical University of Sofia, Zdrave Street 2, 1431 Sofia, Bulgaria
| | - P. Dimitrov
- Vratza District Hospital, 66 “Vtori Iuni” Boulevard, 3000 Vratza, Bulgaria
| | - V. Simeonov
- Faculty of Medicine, University of Nis, Univerzitetski trg 2, 18000 Nis, Serbia
| | - S. Ivanov
- Genomics Laboratory of Malinov Clinic, 1620 Sofia, Bulgaria
| | - L. Balabanski
- Genomics Laboratory of Malinov Clinic, 1620 Sofia, Bulgaria
| | - D. Serbezov
- Genomics Laboratory of Malinov Clinic, 1620 Sofia, Bulgaria
| | - M. Malinov
- Genomics Laboratory of Malinov Clinic, 1620 Sofia, Bulgaria
| | - V. Stefanovic
- Faculty of Medicine, University of Skopje, Macedonian Academy of Sciences and Arts, Bul. Krste Misirkov 2, P.O. Box 428, 1000 Skopje, Macedonia
| | - R. Čukuranović
- Faculty of Medicine, University of Skopje, Macedonian Academy of Sciences and Arts, Bul. Krste Misirkov 2, P.O. Box 428, 1000 Skopje, Macedonia
| | - M. Polenakovic
- Institute of Microbiology, Bulgarian Academy of Sciences, 26 Georgi Bonchev Street, 1113 Sofia, Bulgaria
| | - L. Jankovic-Velickovic
- Faculty of Medicine, University of Skopje, Macedonian Academy of Sciences and Arts, Bul. Krste Misirkov 2, P.O. Box 428, 1000 Skopje, Macedonia
| | - V. Djordjevic
- Faculty of Medicine, University of Skopje, Macedonian Academy of Sciences and Arts, Bul. Krste Misirkov 2, P.O. Box 428, 1000 Skopje, Macedonia
| | - T. Jevtovic-Stoimenov
- Institute of Microbiology, Bulgarian Academy of Sciences, 26 Georgi Bonchev Street, 1113 Sofia, Bulgaria
| | - D. Plaseska-Karanfilska
- Institute of Microbiology, Bulgarian Academy of Sciences, 26 Georgi Bonchev Street, 1113 Sofia, Bulgaria
| | - A. Galabov
- National Center of Public Health and Analyses, 15 Acad. Ivan Evst. Geshov Boulevard, 1431 Sofia, Bulgaria
| | - V. Djonov
- Institute of Anatomy, Bern University, Baltzerstrass 2, 3012 Bern, Switzerland
| | - I. Dimova
- Department of Medical Genetics, Medical University of Sofia, Zdrave Street 2, 1431 Sofia, Bulgaria
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47
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Bai L, Ma X, Zhang G, Song S, Zhou Y, Gao L, Miao Y, Song CP. A Receptor-Like Kinase Mediates Ammonium Homeostasis and Is Important for the Polar Growth of Root Hairs in Arabidopsis. THE PLANT CELL 2014; 26:1497-1511. [PMID: 24769480 PMCID: PMC4036567 DOI: 10.1105/tpc.114.124586] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 03/30/2014] [Accepted: 04/09/2014] [Indexed: 05/19/2023]
Abstract
Ammonium (NH4+) is both a necessary nutrient and an important signal in plants, but can be toxic in excess. Ammonium sensing and regulatory mechanisms in plant cells have not been fully elucidated. To decipher the complex network of NH4+ signaling, we analyzed [Ca2+]cyt-associated protein kinase (CAP) genes, which encode signaling components that undergo marked changes in transcription levels in response to various stressors. We demonstrated that CAP1, a tonoplast-localized receptor-like kinase, regulates root hair tip growth by maintaining cytoplasmic Ca2+ gradients. A CAP1 knockout mutant (cap1-1) produced elevated levels of cytoplasmic NH4+. Furthermore, root hair growth of cap1-1 was inhibited on Murashige and Skoog medium, but NH4+ depletion reestablished the Ca2+ gradient necessary for normal growth. The lower net NH4+ influx across the vacuolar membrane and relatively alkaline cytosolic pH of cap1-1 root hairs implied that mutation of CAP1 increased NH4+ accumulation in the cytoplasm. Furthermore, CAP1 functionally complemented the npr1 (nitrogen permease reactivator protein) kinase yeast mutant, which is defective in high-affinity NH4+ uptake via MEP2 (methylammonium permease 2), distinguishing CAP1 as a cytosolic modulator of NH4+ levels that participates in NH4+ homeostasis-regulated root hair growth by modulating tip-focused cytoplasmic Ca2+ gradients.
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Affiliation(s)
- Ling Bai
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Xiaonan Ma
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Guozeng Zhang
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Shufei Song
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Yun Zhou
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Lijie Gao
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Yuchen Miao
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
| | - Chun-Peng Song
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng 475001, China
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48
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Lenzini L, Caroccia B, Campos AG, Fassina A, Belloni AS, Seccia TM, Kuppusamy M, Ferraro S, Skander G, Bader M, Rainey WE, Rossi GP. Lower expression of the TWIK-related acid-sensitive K+ channel 2 (TASK-2) gene is a hallmark of aldosterone-producing adenoma causing human primary aldosteronism. J Clin Endocrinol Metab 2014; 99:E674-82. [PMID: 24285684 DOI: 10.1210/jc.2013-2900] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
CONTEXT The molecular mechanisms of primary aldosteronism, a common cause of human hypertension, are unknown, but alterations of K(+) channels can play a key role. OBJECTIVE The objective of the study was to investigate the following: 1) the expression of the Twik-related acid-sensitive K(+) channels (TASK) in aldosterone producing adenomas (APAs); 2) the role of TASK-2 in aldosterone synthesis; and 3) the determinants of TASK-2-blunted expression in APAs. DESIGN We analyzed the transcriptome and the microRNA profiles of 32 consecutive APAs and investigated the protein expression and localization of TASK-2 in APA and adrenocortical cell lines (H295R and HAC15) using immunoblotting and confocal microscopy. The functional effect of TASK-2 blunted activity caused by a dominant-negative mutation on steroidogenic enzymes, and aldosterone production was also assessed. TASK-2 regulation by selected microRNA was studied by a luciferase assay. RESULTS TASK-2 was consistently less expressed at the transcript and protein levels in APAs than in the normal human adrenal cortex. H295R cell transfection with a TASK-2 dominant-negative mutant construct significantly increased the aldosterone production by 153% and the gene expression of aldosterone synthase (CYP11B2, gene expression fold change 3.1 vs control, P < .05) and the steroidogenic acute regulatory protein (gene expression fold change 1.8 vs control, P < .05). Two microRNAs, hsa-miR-23 and hsa-miR-34, were found to decrease the TASK-2 expression by binding to the 3' untranslated region of the TASK-2 gene. CONCLUSIONS The TASK-2 channel lower expression represents a hallmark of APA and is associated with a higher expression of hsa-miR-23 and hsa-miR-34. The ensuing blunted TASK-2 activity increased the production of aldosterone in vitro and the expression of steroidogenic acute regulatory protein and CYP11B2. Hence, the lower expression of TASK-2 channel in APA cells can explain high aldosterone secretion in human primary aldosteronism despite the suppression of angiotensin II, hypertension, and hypokalemia.
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Affiliation(s)
- Livia Lenzini
- Internal Medicine 4 (L.L., B.C., A.G.C., T.M.S., M.K., S.F., G.S., G.P.R.) and Surgical Pathology and Cytopathology Unit (A.F.), Department of Medicine, Department of Medicine, Section of Human Anatomy and Physiology (A.S.B.), Department of Molecular Medicine, University of Padua, 35128 Padua, Italy; Max-Delbrück-Center for Molecular Medicine (M.B.), 13092 Berlin, Germany; and Department of Molecular and Integrative Physiology (W.E.R.), University of Michigan, Ann Arbor, Michigan 48109
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Kurtz I, Zhu Q. Proximal renal tubular acidosis mediated by mutations in NBCe1-A: unraveling the transporter's structure-functional properties. Front Physiol 2013; 4:350. [PMID: 24391589 PMCID: PMC3867943 DOI: 10.3389/fphys.2013.00350] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/13/2013] [Indexed: 12/20/2022] Open
Abstract
NBCe1 belongs to the SLC4 family of base transporting membrane proteins that plays a significant role in renal, extrarenal, and systemic acid-base homeostasis. Recent progress has been made in characterizing the structure-function properties of NBCe1 (encoded by the SLC4A4 gene), and those factors that regulate its function. In the kidney, the NBCe1-A variant that is expressed on the basolateral membrane of proximal tubule is the key transporter responsible for overall transepithelial bicarbonate absorption in this nephron segment. NBCe1 mutations impair transepithelial bicarbonate absorption causing the syndrome of proximal renal tubular acidosis (pRTA). Studies of naturally occurring NBCe1 mutant proteins in heterologous expression systems have been very helpful in elucidation the structure-functional properties of the transporter. NBCe1 mutations are now known to cause pRTA by various mechanisms including the alteration of the transporter function (substrate ion interaction, electrogenicity), abnormal processing to the plasma membrane, and a perturbation in its structural properties. The elucidation of how NBCe1 mutations cause pRTA in addition to the recent studies which have provided further insight into the topology of the transporter have played an important role in uncovering its critically important structural-function properties.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, UCLA Los Angeles, CA, USA ; Brain Research Institute, UCLA Los Angeles, CA, USA
| | - Quansheng Zhu
- Division of Nephrology, David Geffen School of Medicine, UCLA Los Angeles, CA, USA
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TASK-2 channels contribute to pH sensitivity of retrotrapezoid nucleus chemoreceptor neurons. J Neurosci 2013; 33:16033-44. [PMID: 24107938 DOI: 10.1523/jneurosci.2451-13.2013] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Phox2b-expressing glutamatergic neurons of the retrotrapezoid nucleus (RTN) display properties expected of central respiratory chemoreceptors; they are directly activated by CO2/H(+) via an unidentified pH-sensitive background K(+) channel and, in turn, facilitate brainstem networks that control breathing. Here, we used a knock-out mouse model to examine whether TASK-2 (K2P5), an alkaline-activated background K(+) channel, contributes to RTN neuronal pH sensitivity. We made patch-clamp recordings in brainstem slices from RTN neurons that were identified by expression of GFP (directed by the Phox2b promoter) or β-galactosidase (from the gene trap used for TASK-2 knock-out). Whereas nearly all RTN cells from control mice were pH sensitive (95%, n = 58 of 61), only 56% of GFP-expressing RTN neurons from TASK-2(-/-) mice (n = 49 of 88) could be classified as pH sensitive (>30% reduction in firing rate from pH 7.0 to pH 7.8); the remaining cells were pH insensitive (44%). Moreover, none of the recorded RTN neurons from TASK-2(-/-) mice selected based on β-galactosidase activity (a subpopulation of GFP-expressing neurons) were pH sensitive. The alkaline-activated background K(+) currents were reduced in amplitude in RTN neurons from TASK-2(-/-) mice that retained some pH sensitivity but were absent from pH-insensitive cells. Finally, using a working heart-brainstem preparation, we found diminished inhibition of phrenic burst amplitude by alkalization in TASK-2(-/-) mice, with apneic threshold shifted to higher pH levels. In conclusion, alkaline-activated TASK-2 channels contribute to pH sensitivity in RTN neurons, with effects on respiration in situ that are particularly prominent near apneic threshold.
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