1
|
Wang WH, Lin DH. Inwardly rectifying K + channels 4.1 and 5.1 (Kir4.1/Kir5.1) in the renal distal nephron. Am J Physiol Cell Physiol 2022; 323:C277-C288. [PMID: 35759440 PMCID: PMC9291425 DOI: 10.1152/ajpcell.00096.2022] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The inwardly rectifying potassium channel (Kir) 4.1 (encoded by KCNJ10) interacts with Kir5.1 (encoded by KCNJ16) to form a major basolateral K+ channel in the renal distal convoluted tubule (DCT), connecting tubule (CNT), and the cortical collecting duct (CCD). Kir4.1/Kir5.1 heterotetramer plays an important role in regulating Na+ and K+ transport in the DCT, CNT, and CCD. A recent development in the field has firmly established the role of Kir4.1/Kir5.1 heterotetramer of the DCT in the regulation of thiazide-sensitive Na-Cl cotransporter (NCC). Changes in Kir4.1/Kir5.1 activity of the DCT are an essential step for the regulation of NCC expression/activity induced by dietary K+ and Na+ intakes and play a role in modulating NCC by type 2 angiotensin II receptor (AT2R), bradykinin type II receptor (BK2R), and β-adrenergic receptor. Since NCC activity determines the Na+ delivery rate to the aldosterone-sensitive distal nephron (ASDN), a distal nephron segment from late DCT to CCD, Kir4.1/Kir5.1 activity plays a critical role not only in the regulation of renal Na+ absorption but also in modulating renal K+ excretion and maintaining K+ homeostasis. Thus, Kir4.1/Kir5.1 activity serves as an important component of renal K+ sensing mechanism. The main focus of this review is to provide an overview regarding the role of Kir4.1 and Kir5.1 of the DCT and CCD in the regulation of renal K+ excretion and Na+ absorption.
Collapse
Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
| |
Collapse
|
2
|
Lo J, Forst AL, Warth R, Zdebik AA. EAST/SeSAME Syndrome and Beyond: The Spectrum of Kir4.1- and Kir5.1-Associated Channelopathies. Front Physiol 2022; 13:852674. [PMID: 35370765 PMCID: PMC8965613 DOI: 10.3389/fphys.2022.852674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 02/08/2022] [Indexed: 12/13/2022] Open
Abstract
In 2009, two groups independently linked human mutations in the inwardly rectifying K+ channel Kir4.1 (gene name KCNJ10) to a syndrome affecting the central nervous system (CNS), hearing, and renal tubular salt reabsorption. The autosomal recessive syndrome has been named EAST (epilepsy, ataxia, sensorineural deafness, and renal tubulopathy) or SeSAME syndrome (seizures, sensorineural deafness, ataxia, intellectual disability, and electrolyte imbalance), accordingly. Renal dysfunction in EAST/SeSAME patients results in loss of Na+, K+, and Mg2+ with urine, activation of the renin-angiotensin-aldosterone system, and hypokalemic metabolic alkalosis. Kir4.1 is highly expressed in affected organs: the CNS, inner ear, and kidney. In the kidney, it mostly forms heteromeric channels with Kir5.1 (KCNJ16). Biallelic loss-of-function mutations of Kir5.1 can also have disease significance, but the clinical symptoms differ substantially from those of EAST/SeSAME syndrome: although sensorineural hearing loss and hypokalemia are replicated, there is no alkalosis, but rather acidosis of variable severity; in contrast to EAST/SeSAME syndrome, the CNS is unaffected. This review provides a framework for understanding some of these differences and will guide the reader through the growing literature on Kir4.1 and Kir5.1, discussing the complex disease mechanisms and the variable expression of disease symptoms from a molecular and systems physiology perspective. Knowledge of the pathophysiology of these diseases and their multifaceted clinical spectrum is an important prerequisite for making the correct diagnosis and forms the basis for personalized therapies.
Collapse
Affiliation(s)
- Jacky Lo
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Anna-Lena Forst
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Richard Warth
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Anselm A. Zdebik
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
| |
Collapse
|
3
|
Membrane pools of phosphatidylinositol-4-phosphate regulate KCNQ1/KCNE1 membrane expression. Commun Biol 2021; 4:1392. [PMID: 34907346 PMCID: PMC8671492 DOI: 10.1038/s42003-021-02909-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 11/24/2021] [Indexed: 11/23/2022] Open
Abstract
Plasma membrane phosphatidylinositol 4-phosphate (PI4P) is a precursor of PI(4,5)P2, an important regulator of a large number of ion channels. Although the role of the phospholipid PI(4,5)P2 in stabilizing ion channel function is well established, little is known about the role of phospholipids in channel membrane localization and specifically the role of PI4P in channel function and localization. The phosphatidylinositol 4-kinases (PI4Ks) synthesize PI4P. Our data show that inhibition of PI4K and prolonged decrease of levels of plasma membrane PI4P lead to a decrease in the KCNQ1/KCNE1 channel membrane localization and function. In addition, we show that mutations linked to Long QT syndrome that affect channel interactions with phospholipids lead to a decrease in membrane expression. We show that expression of a LQT1-associated C-terminal deletion mutant abolishes PI4Kinase-mediated decrease in membrane expression and rescues membrane expression for phospholipid-targeting mutations. Our results indicate a novel role for PI4P on ion channel regulation. Our data suggest that decreased membrane PI4P availability to the channel, either due to inhibition of PI4K or as consequence of mutations, dramatically inhibits KCNQ1/KCNE1 channel membrane localization and current. Our results may have implications to regulation of other PI4P binding channels.
Collapse
|
4
|
Akyuz E, Koklu B, Uner A, Angelopoulou E, Paudel YN. Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy. J Neurosci Res 2021; 100:413-443. [PMID: 34713909 DOI: 10.1002/jnr.24985] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 09/23/2021] [Accepted: 10/01/2021] [Indexed: 01/29/2023]
Abstract
Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.
Collapse
Affiliation(s)
- Enes Akyuz
- Faculty of International Medicine, Department of Biophysics, University of Health Sciences, Istanbul, Turkey
| | - Betul Koklu
- Faculty of Medicine, Namık Kemal University, Tekirdağ, Turkey
| | - Arda Uner
- Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey
| | - Efthalia Angelopoulou
- Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Yam Nath Paudel
- Neuropharmacology Research Strength, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
| |
Collapse
|
5
|
Suzumoto Y, Columbano V, Gervasi L, Giunta R, Mattina T, Trimarchi G, Capolongo G, Simeoni M, Perna AF, Zacchia M, Toriello G, Pollastro RM, Rapisarda F, Capasso G, Trepiccione F. A case series of adult patients affected by EAST/SeSAME syndrome suggests more severe disease in subjects bearing KCNJ10 truncating mutations. Intractable Rare Dis Res 2021; 10:95-101. [PMID: 33996354 PMCID: PMC8122315 DOI: 10.5582/irdr.2020.03158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
EAST/SeSAME syndrome is a rare disease affecting the Central Nervous System (CNS), inner ear, and kidney. The syndrome is due to loss-of-function mutations in the KCNJ10 gene encoding the inward-rectifying potassium channel Kir4.1. EAST/SeSAME syndrome is mainly diagnosed during childhood with a tonic-clonic seizure being the usual first symptom. Due to a limited number of patients and recent identification of the disease, few data are available on the clinical progress of this disease in adulthood. In particular, neurologic and nephrological outcomes have not been reported. We present a case series of 4 adult patients harbouring homozygous missense mutation p.Ala167Val and homozygous frameshift mutations p.Asn232Glnfs*14 and p.Gly275Valfs*7. Effects of these mutations were predicted by in silico modelling and bioinformatic tools. Patients with truncating mutations were associated with more severe outcomes, both in tubulopathy severity and neurological symptomatology. Conversely, either missense or truncating mutations were correlated with similar severity of epilepsy, with a long free-of-event period up to 20 years old. No eGFR decline was documented. Modelling predicted that truncating mutations lead to complete Kir4.1 dysfunction. Finally, all patients had a mild increase in urinary protein excretion. Our study indicates that the prognosis of patients suffering from EAST/SeSAME syndrome is related to the severity of the mutation causing the disease. As predicted by in silico modelling, truncating mutations of KCNJ10 are associated with more severe disease, with recurrence of symptomatic hypokalemia and more severe neurological phenotype. The type of mutation should be considered for the therapy tailored to patients' phenotype.
Collapse
Affiliation(s)
| | - Valeria Columbano
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Luciano Gervasi
- School of Nephrology, Department of Clinical and Experimental Medicine, University of Catania, Italy
| | - Rosa Giunta
- School of Nephrology, Department of Clinical and Experimental Medicine, University of Catania, Italy
| | - Teresa Mattina
- Department of Biomedical and Biotechnological Sciences, University of Catania, Italy
| | - Gabriele Trimarchi
- Department of Biomedical and Biotechnological Sciences, University of Catania, Italy
| | - Giovanna Capolongo
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Mariadelina Simeoni
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Alessandra F. Perna
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Miriam Zacchia
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | | | - Rosa M. Pollastro
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Francesco Rapisarda
- School of Nephrology, Department of Clinical and Experimental Medicine, University of Catania, Italy
| | - Giovambattista Capasso
- Biogem Research Institute, Ariano Irpino, Italy
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Francesco Trepiccione
- Biogem Research Institute, Ariano Irpino, Italy
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
- Address correspondence to:Francesco Trepiccione, Department of Translational Medical Sciences University of Campania "L.Vanvitelli", Via Pansini n5, 80131 Naples, Italy. E-mail:
| |
Collapse
|
6
|
Ma Q, Cao Z, Li H, Wang W, Tian Y, Yan L, Liao Y, Chen X, Chen Y, Shi Y, Tang S, Zhou N. Two naturally occurring mutations of human GPR103 define distinct G protein selection bias. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119046. [PMID: 33872671 DOI: 10.1016/j.bbamcr.2021.119046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 04/12/2021] [Accepted: 04/13/2021] [Indexed: 11/18/2022]
Abstract
The neuropeptide 26RFa plays important roles in the regulation of many physiological functions. 26RFa has been recognized as an endogenous ligand for receptor GPR103. In the present study, we demonstrate that GPR103 dually couples to Gαq and Gαi/o proteins. However, two naturally occurring missense mutations were identified from a young male patient. In the first, Y68H, induction of Ca2+ mobilization was noted without detection of ERK1/2 activation. In the second, R371W, the potential to activate ERK1/2 signaling was retained but with failure to evoke Ca2+ mobilization. Further analysis provides evidence that Gαq, L-type Ca2+ channel and PKCβI and βII are involved in the Y68H-mediated signaling pathway, whereas Gαi/o, Gβγ, and PKCζ are implicated in the R371W-induced signaling. Our results demonstrate that two point mutations, Y68H and R371W, affect the equilibrium between the different receptor conformations, leading to alteration of G protein-coupling preferences. Importantly, these findings provide a foundation for future elucidation of GPCR-mediated biased signaling and the physiological implications of their bias.
Collapse
Affiliation(s)
- Qiang Ma
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China; Department of Neurobiology, NHC and CAMS Key Laboratory of Medical Neurobiology, School of Brain Science and Brian Medicine, MOE Frontier Center of Brain Science and Brain-machine Integration, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Zheng Cao
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Huanzheng Li
- Wenzhou Key Laboratory of Birth Defects, Wenzhou Central Hospital, Wenzhou, Zhejiang 325000, China
| | - Weiwei Wang
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Yanan Tian
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Lili Yan
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Yuan Liao
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Xiangnan Chen
- Wenzhou Key Laboratory of Birth Defects, Wenzhou Central Hospital, Wenzhou, Zhejiang 325000, China
| | - Yu Chen
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Ying Shi
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Shaohua Tang
- Wenzhou Key Laboratory of Birth Defects, Wenzhou Central Hospital, Wenzhou, Zhejiang 325000, China; School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 32500, China
| | - Naiming Zhou
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang 310058, China.
| |
Collapse
|
7
|
Tian Y, Jiang C, Pan Y, Guo Z, Wang W, Luo X, Cao Z, Zhang B, Yang J, Shi Y, Zhou N, He X. Bombyx neuropeptide G protein-coupled receptor A14 and A15 are two functional G protein-coupled receptors for CCHamide neuropeptides. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2021; 131:103553. [PMID: 33582278 DOI: 10.1016/j.ibmb.2021.103553] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 06/12/2023]
Abstract
CCHamides are newly identified insect neuropeptides, which are widely occurring in most insects. However, our knowledge about their signaling characteristics and physiological roles is still limited. Here, we cloned two full-length cDNAs encoding putative CCHamide receptors, Bombyx neuropeptide GPCR A14 (BNGR-A14) and -A15 (BNGR-A15), from the brain of B. mori larvae. Characterization of signaling indicated that Bombyx CCHamide-1 and CCHamide-2 are specific endogenous ligands for BNGR-A15 and BNGR-A14, respectively. Further functional assays combined with specific inhibitors demonstrated that upon activation by CCHamide-2, BNGR-A14 elicited significant increases in CRE-driven luciferase activity, intracellular Ca2+ mobilization and ERK1/2 phosphorylation in a Gq inhibitor-sensitive manner, while BNGR-A15 was activated by CCHamide-1, thus leading to intracellular accumulation of cAMP, Ca2+ mobilization, and ERK1/2 phosphorylation in a Gs and Gq inhibitor-sensitive manner. Based on these findings, we designated the receptors BNGR-A15 and -A14 as Bommo-CCHaR-1 and -2, respectively. In addition, our results showed that CCHamides are considered to require intrachain disulfide bonds to activate their respective receptor in the physiological concentration range. Moreover, quantitative RT-PCR analysis revealed that CCHamide-1 is more likely to serve as a brain-gut peptide to regulate feeding behavior and growth through BNGR-A15, whereas the CCHamide-2 signaling system might play an important role in the control of multiple physiological processes. Our findings provide in-depth information on CCHamide-1 and -2-mediated signaling, facilitating further elucidation of their endocrinological roles in the regulation of fundamental physiological processes.
Collapse
Affiliation(s)
- Yanan Tian
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Chaohui Jiang
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yi Pan
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Zhiqiang Guo
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Weiwei Wang
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Xumei Luo
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Zheng Cao
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Bing Zhang
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, Zhoushan, Zhejiang, 316022, China
| | - Jingwen Yang
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, Zhoushan, Zhejiang, 316022, China
| | - Ying Shi
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Naiming Zhou
- Institute of Biochemistry, College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
| | - Xiaobai He
- College of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, 212018, China.
| |
Collapse
|
8
|
Lv J, Fu X, Li Y, Hong G, Li P, Lin J, Xun Y, Fang L, Weng W, Yue R, Li GL, Guan B, Li H, Huang Y, Chai R. Deletion of Kcnj16 in Mice Does Not Alter Auditory Function. Front Cell Dev Biol 2021; 9:630361. [PMID: 33693002 PMCID: PMC7937937 DOI: 10.3389/fcell.2021.630361] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 01/26/2021] [Indexed: 01/13/2023] Open
Abstract
Endolymphatic potential (EP) is the main driving force behind the sensory transduction of hearing, and K+ is the main charge carrier. Kir5.1 is a K+ transporter that plays a significant role in maintaining EP homeostasis, but the expression pattern and role of Kir5.1 (which is encoded by the Kcnj16 gene) in the mouse auditory system has remained unclear. In this study, we found that Kir5.1 was expressed in the mouse cochlea. We checked the inner ear morphology and measured auditory function in Kcnj16–/– mice and found that loss of Kcnj16 did not appear to affect the development of hair cells. There was no significant difference in auditory function between Kcnj16–/– mice and wild-type littermates, although the expression of Kcnma1, Kcnq4, and Kcne1 were significantly decreased in the Kcnj16–/– mice. Additionally, no significant differences were found in the number or distribution of ribbon synapses between the Kcnj16–/– and wild-type mice. In summary, our results suggest that the Kcnj16 gene is not essential for auditory function in mice.
Collapse
Affiliation(s)
- Jun Lv
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Xiaolong Fu
- State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Yige Li
- State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Guodong Hong
- State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Peipei Li
- School of Life Sciences and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Jing Lin
- Waksman Institute, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
| | - Youfang Xun
- Department of Otolaryngology, Head and Neck Surgery, Xiangya School of Medicine, Central South University, Changsha, China.,Department of Otolaryngology, Head and Neck Surgery, Clinical Medical College of Yangzhou University, Yangzhou, China
| | - Lucheng Fang
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Weibin Weng
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Rongyu Yue
- Department of Otolaryngology-Head and Neck Surgery, Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Geng-Lin Li
- Department of Otorhinolaryngology and ENT Institute, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Bing Guan
- Department of Otolaryngology, Head and Neck Surgery, Clinical Medical College of Yangzhou University, Yangzhou, China
| | - He Li
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Yideng Huang
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.,Department of Otolaryngology-Head and Neck Surgery, Hwa Mei Hospital, University of Chinese Academy of Sciences, Ningbo, China
| | - Renjie Chai
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China.,Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China.,Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
9
|
Franken GAC, Adella A, Bindels RJM, Baaij JHF. Mechanisms coupling sodium and magnesium reabsorption in the distal convoluted tubule of the kidney. Acta Physiol (Oxf) 2021; 231:e13528. [PMID: 32603001 PMCID: PMC7816272 DOI: 10.1111/apha.13528] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 05/29/2020] [Accepted: 06/22/2020] [Indexed: 02/06/2023]
Abstract
Hypomagnesaemia is a common feature of renal Na+ wasting disorders such as Gitelman and EAST/SeSAME syndrome. These genetic defects specifically affect Na+ reabsorption in the distal convoluted tubule, where Mg2+ reabsorption is tightly regulated. Apical uptake via TRPM6 Mg2+ channels and basolateral Mg2+ extrusion via a putative Na+ -Mg2+ exchanger determines Mg2+ reabsorption in the distal convoluted tubule. However, the mechanisms that explain the high incidence of hypomagnesaemia in patients with Na+ wasting disorders of the distal convoluted tubule are largely unknown. In this review, we describe three potential mechanisms by which Mg2+ reabsorption in the distal convoluted tubule is linked to Na+ reabsorption. First, decreased activity of the thiazide-sensitive Na+ /Cl- cotransporter (NCC) results in shortening of the segment, reducing the Mg2+ reabsorption capacity. Second, the activity of TRPM6 and NCC are determined by common regulatory pathways. Secondary effects of NCC dysregulation such as hormonal imbalance, therefore, might disturb TRPM6 expression. Third, the basolateral membrane potential, maintained by the K+ permeability and Na+ -K+ -ATPase activity, provides the driving force for Na+ and Mg2+ extrusion. Depolarisation of the basolateral membrane potential in Na+ wasting disorders of the distal convoluted tubule may therefore lead to reduced activity of the putative Na+ -Mg2+ exchanger SLC41A1. Elucidating the interconnections between Mg2+ and Na+ transport in the distal convoluted tubule is hampered by the currently available models. Our analysis indicates that the coupling of Na+ and Mg2+ reabsorption may be multifactorial and that advanced experimental models are required to study the molecular mechanisms.
Collapse
Affiliation(s)
- Gijs A. C. Franken
- Department of Physiology Radboud Institute for Molecular Life SciencesRadboud University Medical Center Nijmegen the Netherlands
| | - Anastasia Adella
- Department of Physiology Radboud Institute for Molecular Life SciencesRadboud University Medical Center Nijmegen the Netherlands
| | - René J. M. Bindels
- Department of Physiology Radboud Institute for Molecular Life SciencesRadboud University Medical Center Nijmegen the Netherlands
| | - Jeroen H. F. Baaij
- Department of Physiology Radboud Institute for Molecular Life SciencesRadboud University Medical Center Nijmegen the Netherlands
| |
Collapse
|
10
|
Nagai J, Yu X, Papouin T, Cheong E, Freeman MR, Monk KR, Hastings MH, Haydon PG, Rowitch D, Shaham S, Khakh BS. Behaviorally consequential astrocytic regulation of neural circuits. Neuron 2020; 109:576-596. [PMID: 33385325 DOI: 10.1016/j.neuron.2020.12.008] [Citation(s) in RCA: 122] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/23/2020] [Accepted: 12/07/2020] [Indexed: 12/16/2022]
Abstract
Astrocytes are a large and diverse population of morphologically complex cells that exist throughout nervous systems of multiple species. Progress over the last two decades has shown that astrocytes mediate developmental, physiological, and pathological processes. However, a long-standing open question is how astrocytes regulate neural circuits in ways that are behaviorally consequential. In this regard, we summarize recent studies using Caenorhabditis elegans, Drosophila melanogaster, Danio rerio, and Mus musculus. The data reveal diverse astrocyte mechanisms operating in seconds or much longer timescales within neural circuits and shaping multiple behavioral outputs. We also refer to human diseases that have a known primary astrocytic basis. We suggest that including astrocytes in mechanistic, theoretical, and computational studies of neural circuits provides new perspectives to understand behavior, its regulation, and its disease-related manifestations.
Collapse
Affiliation(s)
- Jun Nagai
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; RIKEN Center for Brain Science, 2-1 Hirosawa Wako City, Saitama 351-0198, Japan
| | - Xinzhu Yu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, 514 Burrill Hall, 407 S. Goodwin Ave, Urbana, IL 61801, USA
| | - Thomas Papouin
- Department of Neuroscience, Washington University in St. Louis, School of Medicine, Campus Box 8108, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Eunji Cheong
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Marc R Freeman
- The Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Kelly R Monk
- The Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Michael H Hastings
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Philip G Haydon
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - David Rowitch
- Department of Paediatrics, Wellcome-MRC Cambridge Stem Cell Institute, University of Cambridge, Cambridge, UK; Departments of Pediatrics and Neurosurgery, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
| |
Collapse
|
11
|
Kinboshi M, Ikeda A, Ohno Y. Role of Astrocytic Inwardly Rectifying Potassium (Kir) 4.1 Channels in Epileptogenesis. Front Neurol 2020; 11:626658. [PMID: 33424762 PMCID: PMC7786246 DOI: 10.3389/fneur.2020.626658] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/08/2020] [Indexed: 12/25/2022] Open
Abstract
Astrocytes regulate potassium and glutamate homeostasis via inwardly rectifying potassium (Kir) 4.1 channels in synapses, maintaining normal neural excitability. Numerous studies have shown that dysfunction of astrocytic Kir4.1 channels is involved in epileptogenesis in humans and animal models of epilepsy. Specifically, Kir4.1 channel inhibition by KCNJ10 gene mutation or expressional down-regulation increases the extracellular levels of potassium ions and glutamate in synapses and causes hyperexcitation of neurons. Moreover, recent investigations demonstrated that inhibition of Kir4.1 channels facilitates the expression of brain-derived neurotrophic factor (BDNF), an important modulator of epileptogenesis, in astrocytes. In this review, we summarize the current understanding on the role of astrocytic Kir4.1 channels in epileptogenesis, with a focus on functional and expressional changes in Kir4.1 channels and their regulation of BDNF secretion. We also discuss the potential of Kir4.1 channels as a therapeutic target for the prevention of epilepsy.
Collapse
Affiliation(s)
- Masato Kinboshi
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan.,Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yukihiro Ohno
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
| |
Collapse
|
12
|
D'Adamo MC, Liantonio A, Conte E, Pessia M, Imbrici P. Ion Channels Involvement in Neurodevelopmental Disorders. Neuroscience 2020; 440:337-359. [PMID: 32473276 DOI: 10.1016/j.neuroscience.2020.05.032] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 05/16/2020] [Accepted: 05/19/2020] [Indexed: 12/14/2022]
Abstract
Inherited and sporadic mutations in genes encoding for brain ion channels, affecting membrane expression or biophysical properties, have been associated with neurodevelopmental disorders characterized by epilepsy, cognitive and behavioral deficits with significant phenotypic and genetic heterogeneity. Over the years, the screening of a growing number of patients and the functional characterization of newly identified mutations in ion channels genes allowed to recognize new phenotypes and to widen the clinical spectrum of known diseases. Furthermore, advancements in understanding disease pathogenesis at atomic level or using patient-derived iPSCs and animal models have been pivotal to orient therapeutic intervention and to put the basis for the development of novel pharmacological options for drug-resistant disorders. In this review we will discuss major improvements and critical issues concerning neurodevelopmental disorders caused by dysfunctions in brain sodium, potassium, calcium, chloride and ligand-gated ion channels.
Collapse
Affiliation(s)
- Maria Cristina D'Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Malta
| | | | - Elena Conte
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Italy
| | - Mauro Pessia
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Malta; Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Italy.
| |
Collapse
|
13
|
Manis AD, Hodges MR, Staruschenko A, Palygin O. Expression, localization, and functional properties of inwardly rectifying K + channels in the kidney. Am J Physiol Renal Physiol 2020; 318:F332-F337. [PMID: 31841387 PMCID: PMC7052651 DOI: 10.1152/ajprenal.00523.2019] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 12/10/2019] [Accepted: 12/10/2019] [Indexed: 12/13/2022] Open
Abstract
Inwardly rectifying K+ (Kir) channels are expressed in multiple organs and cell types and play critical roles in cellular function. Most notably, Kir channels are major determinants of the resting membrane potential and K+ homeostasis. The renal outer medullary K+ channel (Kir1.1) was the first renal Kir channel identified and cloned in the kidney over two decades ago. Since then, several additional members, including classical and ATP-regulated Kir family classes, have been identified to be expressed in the kidney and to contribute to renal ion transport. Although the ATP-regulated Kir channel class remains the most well known due to severe pathological phenotypes associated with their mutations, progress is being made in defining the properties, localization, and physiological functions of other renal Kir channels, including those localized to the basolateral epithelium. This review is primarily focused on the current knowledge of the expression and localization of renal Kir channels but will also briefly describe their proposed functions in the kidney.
Collapse
Affiliation(s)
- Anna D Manis
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Matthew R Hodges
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
| | - Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin
- Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| |
Collapse
|
14
|
Ronzier E, Parks XX, Qudsi H, Lopes CM. Statin-specific inhibition of Rab-GTPase regulates cPKC-mediated IKs internalization. Sci Rep 2019; 9:17747. [PMID: 31780674 PMCID: PMC6882895 DOI: 10.1038/s41598-019-53700-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 10/21/2019] [Indexed: 12/18/2022] Open
Abstract
Statins are prescribed for prevention and treatment of coronary artery disease. Statins have different cholesterol lowering abilities, with rosuvastatin and atorvastatin being the most effective, while statins like simvastatin and fluvastatin having lower effectiveness. Statins, in addition to their cholesterol lowering effects, can prevent isoprenylation of Rab-GTPase proteins, a protein family important for the regulation of membrane-bound protein trafficking. Here we show that endosomal localization of Rab-GTPases (Rab5, Rab7 and Rab11) was inhibited in a statin-specific manner, with stronger effects by fluvastatin, followed by simvastatin and atorvastatin, and with a limited effect by rosuvastatin. Fluvastatin inhibition of Rab5 has been shown to mediate cPKC-dependent trafficking regulation of the cardiac delayed rectifier KCNQ1/KCNE1 channels. We observed statin-specific inhibition of channel regulation consistent with statin-specific Rab-GTPase inhibition both in heterologous systems and cardiomyocytes. Our results uncover a non-cholesterol-reducing statin-specific effect of statins. Because Rab-GTPases are important regulators of membrane trafficking they may underlie statin specific pleiotropic effects. Therefore, statin-specificity may allow better treatment tailoring.
Collapse
Affiliation(s)
- Elsa Ronzier
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA
| | - Xiaorong Xu Parks
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA
| | - Haani Qudsi
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA
| | - Coeli M Lopes
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY, 14642, USA.
| |
Collapse
|
15
|
Zangerl-Plessl EM, Qile M, Bloothooft M, Stary-Weinzinger A, van der Heyden MAG. Disease Associated Mutations in K IR Proteins Linked to Aberrant Inward Rectifier Channel Trafficking. Biomolecules 2019; 9:biom9110650. [PMID: 31731488 PMCID: PMC6920955 DOI: 10.3390/biom9110650] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 12/28/2022] Open
Abstract
The ubiquitously expressed family of inward rectifier potassium (KIR) channels, encoded by KCNJ genes, is primarily involved in cell excitability and potassium homeostasis. Channel mutations associate with a variety of severe human diseases and syndromes, affecting many organ systems including the central and peripheral neural system, heart, kidney, pancreas, and skeletal muscle. A number of mutations associate with altered ion channel expression at the plasma membrane, which might result from defective channel trafficking. Trafficking involves cellular processes that transport ion channels to and from their place of function. By alignment of all KIR channels, and depicting the trafficking associated mutations, three mutational hotspots were identified. One localized in the transmembrane-domain 1 and immediately adjacent sequences, one was found in the G-loop and Golgi-export domain, and the third one was detected at the immunoglobulin-like domain. Surprisingly, only few mutations were observed in experimentally determined Endoplasmic Reticulum (ER)exit-, export-, or ER-retention motifs. Structural mapping of the trafficking defect causing mutations provided a 3D framework, which indicates that trafficking deficient mutations form clusters. These “mutation clusters” affect trafficking by different mechanisms, including protein stability.
Collapse
Affiliation(s)
- Eva-Maria Zangerl-Plessl
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Muge Qile
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Meye Bloothooft
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Marcel A. G. van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
- Correspondence: ; Tel.: +31-887558901
| |
Collapse
|
16
|
van der Wijst J, Belge H, Bindels RJM, Devuyst O. Learning Physiology From Inherited Kidney Disorders. Physiol Rev 2019; 99:1575-1653. [PMID: 31215303 DOI: 10.1152/physrev.00008.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.
Collapse
Affiliation(s)
- Jenny van der Wijst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Hendrica Belge
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Olivier Devuyst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| |
Collapse
|
17
|
Mir A, Chaudhary M, Alkhaldi H, Alhazmi R, Albaradie R, Housawi Y. Epilepsy in patients with EAST syndrome caused by mutation in the KCNJ10. Brain Dev 2019; 41:706-715. [PMID: 30952461 DOI: 10.1016/j.braindev.2019.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 03/03/2019] [Accepted: 03/19/2019] [Indexed: 11/20/2022]
Abstract
OBJECTIVE EAST syndrome comprises of epilepsy, ataxia, sensorineural deafness, and tubulopathy. It is caused by a mutation in KCNJ10 gene. Less than thirty cases have been reported in the literature with emphasis on genetic mutation and renal tubulopathy. In this article, our goal is to present a comprehensive description of epilepsy and its management. A literature review is also presented to consolidate and compare our findings with the previously reported cases. METHODS Retrospective chart review was done to collect patient data. Research clinic was organized to obtain missing data. Molecular genetic testing was done at the CGC Genetics Laboratory. Electroencephalogram (EEG) was done for all patients and interpreted by a pediatric epileptologist and brain MRI was reviewed by a pediatric neuroradiologist. Developmental assessment was done by a developmental pediatrician using Griffiths Mental Developmental Scale. RESULTS In patients with EAST syndrome, seizure is the first symptom occurring around 3-4 months of age. Most common seizure type was generalized tonic clonic (GTC). Usually, the seizures were brief lasting <3 min but few patients also presented with status epilepticus especially when the medication was weaned. Carbamazepine (CBZ) was found to be effective in most cases. Lamotrigine (LTG), valproic acid (VPA), and topiramate (TPM) were also found to be helpful. Routine EEGs were usually normal or showed non-specific findings. In few patients, EEG showed background slowing. Brain MRI revealed hyperintensity in the dentate nuclei in some patients, and quantitative volumetric analysis studies showed volume loss in different regions of the brain especially the cerebellum. All our five patients have the same homozygous c.170C>T (p.Thr57Ile) missense mutation in KCNJ10 gene. CONCLUSION This article provides the readers with an understanding of the natural history of epilepsy in this syndrome to help in early recognition, avoid unnecessary investigations, and provide the best treatment for seizures. It also helps the physicians to share the prognosis of this rare syndrome with the parents.
Collapse
Affiliation(s)
- Ali Mir
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia.
| | - Mohammed Chaudhary
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Hani Alkhaldi
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Rami Alhazmi
- Medical Imaging Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Raidah Albaradie
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Yousef Housawi
- Genetic and Metabolic Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| |
Collapse
|
18
|
Parks XX, Ronzier E, O-Uchi J, Lopes CM. Fluvastatin inhibits Rab5-mediated IKs internalization caused by chronic Ca 2+-dependent PKC activation. J Mol Cell Cardiol 2019; 129:314-325. [PMID: 30898664 DOI: 10.1016/j.yjmcc.2019.03.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 02/26/2019] [Accepted: 03/16/2019] [Indexed: 10/27/2022]
Abstract
Statins, in addition to their cholesterol lowering effects, can prevent isoprenylation of Rab GTPase proteins, a key protein family for the regulation of protein trafficking. Rab-GTPases have been shown to be involved in the control of membrane expression level of ion channels, including one of the major cardiac repolarizing channels, IKs. Decreased IKs function has been observed in a number of disease states and associated with increased propensity for arrhythmias, but the mechanism underlying IKs decrease remains elusive. Ca2+-dependent PKC isoforms (cPKC) are chronically activated in variety of human diseases and have been suggested to acutely regulate IKs function. We hypothesize that chronic cPKC stimulation leads to Rab-mediated decrease in IKs membrane expression, and that can be prevented by statins. In this study we show that chronic cPKC stimulation caused a dramatic Rab5 GTPase-dependent decrease in plasma membrane localization of the IKs pore forming subunit KCNQ1, reducing IKs function. Our data indicates fluvastatin inhibition of Rab5 restores channel localization and function after cPKC-mediated channel internalization. Our results indicate a novel statin anti-arrhythmic effect that would be expected to inhibit pathological electrical remodeling in a number of disease states associated with high cPKC activation. Because Rab-GTPases are important regulators of membrane trafficking they may underlie other statin pleiotropic effects.
Collapse
Affiliation(s)
- Xiaorong Xu Parks
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America
| | - Elsa Ronzier
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America
| | - Jin O-Uchi
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America; Lillehei Heart Institute, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455, United States of America
| | - Coeli M Lopes
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America.
| |
Collapse
|
19
|
Malik S, Lambert E, Zhang J, Wang T, Clark HL, Cypress M, Goldman BI, Porter GA, Pena S, Nino W, Gray DA. Potassium conservation is impaired in mice with reduced renal expression of Kir4.1. Am J Physiol Renal Physiol 2018; 315:F1271-F1282. [PMID: 30110571 DOI: 10.1152/ajprenal.00022.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To better understand the role of the inward-rectifying K channel Kir4.1 (KCNJ10) in the distal nephron, we initially studied a global Kir4.1 knockout mouse (gKO), which demonstrated the hypokalemia and hypomagnesemia seen in SeSAME/EAST syndrome and was associated with reduced Na/Cl cotransporter (NCC) expression. Lethality by ~3 wk, however, limits the usefulness of this model, so we developed a kidney-specific Kir4.1 "knockdown" mouse (ksKD) using a cadherin 16 promoter and Cre-loxP methodology. These mice appeared normal and survived to adulthood. Kir4.1 protein expression was decreased ~50% vs. wild-type (WT) mice by immunoblotting, and immunofluorescence showed moderately reduced Kir4.1 staining in distal convoluted tubule that was minimal or absent in connecting tubule and cortical collecting duct. Under control conditions, the ksKD mice showed metabolic alkalosis and relative hypercalcemia but were normokalemic and mildly hypermagnesemic despite decreased NCC expression. In addition, the mice had a severe urinary concentrating defect associated with hypernatremia, enlarged kidneys with tubulocystic dilations, and reduced aquaporin-3 expression. On a K/Mg-free diet for 1 wk, however, ksKD mice showed marked hypokalemia (serum K: 1.5 ± 0.1 vs. 3.0 ± 0.1 mEq/l for WT), which was associated with renal K wasting (transtubular K gradient: 11.4 ± 0.8 vs. 1.6 ± 0.4 in WT). Phosphorylated-NCC expression increased in WT but not ksKD mice on the K/Mg-free diet, suggesting that loss of NCC adaptation underlies the hypokalemia. In conclusion, even modest reduction in Kir4.1 expression results in impaired K conservation, which appears to be mediated by reduced expression of activated NCC.
Collapse
Affiliation(s)
- Sundeep Malik
- Department of Pharmacology and Physiology, School of Medicine, University of Rochester , Rochester, New York
| | - Emily Lambert
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Junhui Zhang
- Department of Cellular and Molecular Physiology, Yale University School of Medicine , New Haven, Connecticut
| | - Tong Wang
- Department of Cellular and Molecular Physiology, Yale University School of Medicine , New Haven, Connecticut
| | - Heather L Clark
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Michael Cypress
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Bruce I Goldman
- Pathology and Laboratory Medicine, University of Rochester , Rochester, New York
| | - George A Porter
- Cardiology Division, Department of Pediatrics, University of Rochester , Rochester, New York
| | - Salvador Pena
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Wilson Nino
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Daniel A Gray
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| |
Collapse
|
20
|
Celmina M, Micule I, Inashkina I, Audere M, Kuske S, Pereca J, Stavusis J, Pelnena D, Strautmanis J. EAST/SeSAME syndrome: Review of the literature and introduction of four new Latvian patients. Clin Genet 2018; 95:63-78. [PMID: 29722015 DOI: 10.1111/cge.13374] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/12/2018] [Accepted: 04/23/2018] [Indexed: 11/28/2022]
Abstract
EAST (Epilepsy, Ataxia, Sensorineural deafness, Tubulopathy) or SeSAME (Seizures, Sensorineural deafness, Ataxia, Mental retardation, and Electrolyte imbalance) syndrome is a rare autosomal recessive syndrome first described in 2009 independently by Bockenhauer and Scholl. It is caused by mutations in KCNJ10, which encodes Kir4.1, an inwardly rectifying K+ channel found in the brain, inner ear, kidney and eye. To date, 16 mutations and at least 28 patients have been reported. In this paper, we review mutations causing EAST/SeSAME syndrome, clinical manifestations in detail, and efficacy of treatment in previously reported patients. We also report a new Latvian kindred with 4 patients. In contrast to the majority of previous reports, we found a progressive course of the disorder in terms of hearing impairment and neurologic deficit. The treatment is based on antiepileptic drugs, electrolyte replacement, hearing aids and mobility devices. Future research should concentrate on recognizing the lesions in the central nervous system to evaluate new potential diagnostic criteria and on formally evaluating intellectual disability.
Collapse
Affiliation(s)
- M Celmina
- Clinic for Pediatrics, Children's Clinical University Hospital, Riga, Latvia.,Faculty of Continuing Education, University of Latvia, Riga, Latvia
| | - I Micule
- Clinic for Medical Genetics and Prenatal Diagnostics, Children's Clinical University Hospital, Riga, Latvia
| | - I Inashkina
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - M Audere
- ENT Department, Children's Clinical University Hospital, Riga, Latvia
| | - S Kuske
- Latvian Children's Hearing Center, Riga, Latvia
| | - J Pereca
- Emergency Department, Royal Infirmary of Edinburg, Edinburgh, United Kingdom
| | - J Stavusis
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - D Pelnena
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - J Strautmanis
- Clinic for Pediatric Neurology and Neurosurgery, Children's Clinical University Hospital, Riga, Latvia
| |
Collapse
|
21
|
Papavasiliou A, Foska K, Ioannou J, Nagel M. Epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome in a European child with KCNJ10 mutations: A case report. SAGE Open Med Case Rep 2017; 5:2050313X17723549. [PMID: 28835827 PMCID: PMC5536383 DOI: 10.1177/2050313x17723549] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 07/07/2017] [Indexed: 11/23/2022] Open
Abstract
Background: Epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome is a multi-organ disorder that links to autosomal recessive mutations in the KCNJ10 gene, which encodes for the Kir4.1 potassium channel. It is mostly described in consanguineous, non-European families. Case Report: A European male of non-consanguineous birth, with early-onset, static ataxic motor disorder, intellectual disability and epilepsy, imitating cerebral palsy, presented with additional findings of renal tubulopathy, sensorineural deafness and normal neuroimaging leading to the diagnosis of epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome. The patient was heterozygous for two KCNJ10 mutations: a missense mutation (p.R65C) that is already published and a not yet published duplication (p.F119GfsX25) that creates a premature truncation of the protein. Both mutations are likely damaging. Parental testing has not been performed, and therefore, we do not know for certain whether the mutations are on different alleles. This young man presents some clinical and laboratory features that differ from previously reported patients with epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome. Conclusion: The necessity of accurate diagnosis through genetic testing in patients with static motor disorders resembling cerebral palsy phenotypes, atypical clinical features and noncontributory neuroimaging is emphasized.
Collapse
Affiliation(s)
| | - Katerina Foska
- Department of Pediatric Neurology, Pendeli Children's Hospital, Athens, Greece
| | - John Ioannou
- Department of Pediatric Neurology, Pendeli Children's Hospital, Athens, Greece
| | - Mato Nagel
- Laboratory for Molecular Diagnostics, Weisswasser, Germany
| |
Collapse
|
22
|
Hasan S, Balobaid A, Grottesi A, Dabbagh O, Cenciarini M, Rawashdeh R, Al-Sagheir A, Bove C, Macchioni L, Pessia M, Al-Owain M, D'Adamo MC. Lethal digenic mutations in the K + channels Kir4.1 ( KCNJ10) and SLACK ( KCNT1) associated with severe-disabling seizures and neurodevelopmental delay. J Neurophysiol 2017; 118:2402-2411. [PMID: 28747464 DOI: 10.1152/jn.00284.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 07/05/2017] [Accepted: 07/21/2017] [Indexed: 01/14/2023] Open
Abstract
A 2-yr-old boy presented profound developmental delay, failure to thrive, ataxia, hypotonia, and tonic-clonic seizures that caused the death of the patient. Targeted and whole exome sequencing revealed two heterozygous missense variants: a novel mutation in the KCNJ10 gene that encodes for the inward-rectifying K+ channel Kir4.1 and another previously characterized mutation in KCNT1 that encodes for the Na+-activated K+ channel known as Slo2.2 or SLACK. The objectives of this study were to perform the clinical and genetic characterization of the proband and his family and to examine the functional consequence of the Kir4.1 mutation. The mutant and wild-type KCNJ10 constructs were generated and heterologously expressed in Xenopus laevis oocytes, and whole cell K+ currents were measured using the two-electrode voltage-clamp technique. The KCNJ10 mutation c.652C>T resulted in a p.L218F substitution at a highly conserved residue site. Wild-type KCNJ10 expression yielded robust Kir current, whereas currents from oocytes expressing the mutation were reduced, remarkably. Western Blot analysis revealed reduced protein expression by the mutation. Kir5.1 subunits display selective heteromultimerization with Kir4.1 constituting channels with unique kinetics. The effect of the mutation on Kir4.1/5.1 channel activity was twofold: a reduction in current amplitudes and an increase in the pH-dependent inhibition. We thus report a novel loss-of-function mutation in Kir4.1 found in a patient with a coexisting mutation in SLACK channels that results in a fatal disease.NEW & NOTEWORTHY We present and characterize a novel mutation in KCNJ10 Unlike previously reported EAST/SeSAME patients, our patient was heterozygous, and contrary to previous studies, mimicking the heterozygous state by coexpression resulted in loss of channel function. We report in the same patient co-occurrence of a KCNT1 mutation resulting in a more severe phenotype. This study provides new insights into the phenotypic spectrum and to the genotype-phenotype correlations associated with EAST/SeSAME and MMFSI.
Collapse
Affiliation(s)
- Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Ameera Balobaid
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | | | - Omar Dabbagh
- Department of Neurosciences, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Marta Cenciarini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Rifaat Rawashdeh
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Afaf Al-Sagheir
- Department of Pediatrics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Cecilia Bove
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Lara Macchioni
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy.,Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
| | - Mohammed Al-Owain
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.,College of Medicine, AlFaisal University, Riyadh, Saudi Arabia; and
| | - Maria Cristina D'Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta; .,Fondazione Santa Lucia, IRCCS, Rome, Italy
| |
Collapse
|
23
|
Dossi E, Vasile F, Rouach N. Human astrocytes in the diseased brain. Brain Res Bull 2017; 136:139-156. [PMID: 28212850 PMCID: PMC5766741 DOI: 10.1016/j.brainresbull.2017.02.001] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/08/2017] [Accepted: 02/09/2017] [Indexed: 12/23/2022]
Abstract
Astrocytes are key active elements of the brain that contribute to information processing. They not only provide neurons with metabolic and structural support, but also regulate neurogenesis and brain wiring. Furthermore, astrocytes modulate synaptic activity and plasticity in part by controlling the extracellular space volume, as well as ion and neurotransmitter homeostasis. These findings, together with the discovery that human astrocytes display contrasting characteristics with their rodent counterparts, point to a role for astrocytes in higher cognitive functions. Dysfunction of astrocytes can thereby induce major alterations in neuronal functions, contributing to the pathogenesis of several brain disorders. In this review we summarize the current knowledge on the structural and functional alterations occurring in astrocytes from the human brain in pathological conditions such as epilepsy, primary tumours, Alzheimer's disease, major depressive disorder and Down syndrome. Compelling evidence thus shows that dysregulations of astrocyte functions and interplay with neurons contribute to the development and progression of various neurological diseases. Targeting astrocytes is thus a promising alternative approach that could contribute to the development of novel and effective therapies to treat brain disorders.
Collapse
Affiliation(s)
- Elena Dossi
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
| | - Flora Vasile
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
| |
Collapse
|
24
|
A Missense Variant in KCNJ10 in Belgian Shepherd Dogs Affected by Spongy Degeneration with Cerebellar Ataxia (SDCA1). G3-GENES GENOMES GENETICS 2017; 7:663-669. [PMID: 28007838 PMCID: PMC5295610 DOI: 10.1534/g3.116.038455] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Spongy degeneration with cerebellar ataxia (SDCA) is a severe neurodegenerative disease with monogenic autosomal recessive inheritance in Malinois dogs, one of the four varieties of the Belgian Shepherd breed. We performed a genetic investigation in six families and seven isolated cases of Malinois dogs with signs of cerebellar dysfunction. Linkage analysis revealed an unexpected genetic heterogeneity within the studied cases. The affected dogs from four families and one isolated case shared a ∼1.4 Mb common homozygous haplotype segment on chromosome 38. Whole genome sequence analysis of three affected and 140 control dogs revealed a missense variant in the KCNJ10 gene encoding a potassium channel (c.986T>C; p.Leu329Pro). Pathogenic variants in KCNJ10 were reported previously in humans, mice, and dogs with neurological phenotypes. Therefore, we consider KCNJ10:c.986T>C the most likely candidate causative variant for one subtype of SDCA in Malinois dogs, which we propose to term spongy degeneration with cerebellar ataxia 1 (SDCA1). However, our study also comprised samples from 12 Malinois dogs with cerebellar dysfunction which were not homozygous for this variant, suggesting a different genetic basis in these dogs. A retrospective detailed clinical and histopathological analysis revealed subtle neuropathological differences with respect to SDCA1-affected dogs. Thus, our study highlights the genetic and phenotypic complexity underlying cerebellar dysfunction in Malinois dogs and provides the basis for a genetic test to eradicate one specific neurodegenerative disease from the breeding population. These dogs represent an animal model for the human EAST syndrome.
Collapse
|
25
|
Palygin O, Pochynyuk O, Staruschenko A. Role and mechanisms of regulation of the basolateral K ir 4.1/K ir 5.1K + channels in the distal tubules. Acta Physiol (Oxf) 2017; 219:260-273. [PMID: 27129733 PMCID: PMC5086442 DOI: 10.1111/apha.12703] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 01/28/2016] [Accepted: 04/28/2016] [Indexed: 12/11/2022]
Abstract
Epithelial K+ channels are essential for maintaining electrolyte and fluid homeostasis in the kidney. It is recognized that basolateral inward-rectifying K+ (Kir ) channels play an important role in the control of resting membrane potential and transepithelial voltage, thereby modulating water and electrolyte transport in the distal part of nephron and collecting duct. Monomeric Kir 4.1 (encoded by Kcnj10 gene) and heteromeric Kir 4.1/Kir 5.1 (Kir 4.1 together with Kir 5.1 (Kcnj16)) channels are abundantly expressed at the basolateral membranes of the distal convoluted tubule and the cortical collecting duct cells. Loss-of-function mutations in KCNJ10 cause EAST/SeSAME tubulopathy in humans associated with salt wasting, hypomagnesaemia, metabolic alkalosis and hypokalaemia. In contrast, mice lacking Kir 5.1 have severe renal phenotype that, apart from hypokalaemia, is the opposite of the phenotype seen in EAST/SeSAME syndrome. Experimental advances using genetic animal models provided critical insights into the physiological role of these channels in electrolyte homeostasis and the control of kidney function. Here, we discuss current knowledge about K+ channels at the basolateral membrane of the distal tubules with specific focus on the homomeric Kir 4.1 and heteromeric Kir 4.1/Kir 5.1 channels. Recently identified molecular mechanisms regulating expression and activity of these channels, such as cell acidification, dopamine, insulin and insulin-like growth factor-1, Src family protein tyrosine kinases, as well as the role of these channels in NCC-mediated transport in the distal convoluted tubules, are also described.
Collapse
Affiliation(s)
- Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | | |
Collapse
|
26
|
Seifert G, Henneberger C, Steinhäuser C. Diversity of astrocyte potassium channels: An update. Brain Res Bull 2016; 136:26-36. [PMID: 27965079 DOI: 10.1016/j.brainresbull.2016.12.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 12/08/2016] [Accepted: 12/09/2016] [Indexed: 01/08/2023]
Abstract
Astrocyte K+ channels and the K+ currents they mediate dwarf all other transmembrane conductances in these cells. This defining feature of astrocytes and its functional implications have been investigated intensely over the past decades. Nonetheless, many aspects of astrocyte K+ handling and signaling remain incompletely understood. In this review, we provide an update on the diversity of K+ channels expressed by astrocytes and new functional implications. We focus on inwardly-rectifying K+ channels (particularly Kir4.1), two-pore K+ channels and voltage and Ca2+-dependent K+ channels. We further discuss new insights into the involvement of these K+ channels in K+ buffering, control of synaptic transmission, regulation of the vasculature and in diseases of the central nervous system.
Collapse
Affiliation(s)
- Gerald Seifert
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.
| | - Christian Henneberger
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany; German Center of Neurodegenerative Diseases (DZNE), Bonn, Germany; Institute of Neurology, University College London, London, United Kingdom
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.
| |
Collapse
|
27
|
Nwaobi SE, Cuddapah VA, Patterson KC, Randolph AC, Olsen ML. The role of glial-specific Kir4.1 in normal and pathological states of the CNS. Acta Neuropathol 2016; 132:1-21. [PMID: 26961251 DOI: 10.1007/s00401-016-1553-1] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 02/16/2016] [Accepted: 02/25/2016] [Indexed: 12/15/2022]
Abstract
Kir4.1 is an inwardly rectifying K(+) channel expressed exclusively in glial cells in the central nervous system. In glia, Kir4.1 is implicated in several functions including extracellular K(+) homeostasis, maintenance of astrocyte resting membrane potential, cell volume regulation, and facilitation of glutamate uptake. Knockout of Kir4.1 in rodent models leads to severe neurological deficits, including ataxia, seizures, sensorineural deafness, and early postnatal death. Accumulating evidence indicates that Kir4.1 plays an integral role in the central nervous system, prompting many laboratories to study the potential role that Kir4.1 plays in human disease. In this article, we review the growing evidence implicating Kir4.1 in a wide array of neurological disease. Recent literature suggests Kir4.1 dysfunction facilitates neuronal hyperexcitability and may contribute to epilepsy. Genetic screens demonstrate that mutations of KCNJ10, the gene encoding Kir4.1, causes SeSAME/EAST syndrome, which is characterized by early onset seizures, compromised verbal and motor skills, profound cognitive deficits, and salt-wasting. KCNJ10 has also been linked to developmental disorders including autism. Cerebral trauma, ischemia, and inflammation are all associated with decreased astrocytic Kir4.1 current amplitude and astrocytic dysfunction. Additionally, neurodegenerative diseases such as Alzheimer disease and amyotrophic lateral sclerosis demonstrate loss of Kir4.1. This is particularly exciting in the context of Huntington disease, another neurodegenerative disorder in which restoration of Kir4.1 ameliorated motor deficits, decreased medium spiny neuron hyperexcitability, and extended survival in mouse models. Understanding the expression and regulation of Kir4.1 will be critical in determining if this channel can be exploited for therapeutic benefit.
Collapse
|
28
|
Abdelhadi O, Iancu D, Tekman M, Stanescu H, Bockenhauer D, Kleta R. Founder mutation in KCNJ10 in Pakistani patients with EAST syndrome. Mol Genet Genomic Med 2016; 4:521-6. [PMID: 27652280 PMCID: PMC5023937 DOI: 10.1002/mgg3.227] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 11/11/2022] Open
Abstract
Background EAST syndrome is an autosomal recessive disorder caused by loss‐of‐function mutations in the gene KCNJ10. Among the 14 pathogenic mutations described so far, the p.R65P mutation stands out as the most frequent one and is particularly associated with patients of Pakistani origin. As a result we aimed to establish the existence of a potential founder effect in the Pakistani population. Methods To this end, we genotyped 12 patients from seven families and we compared disease haplotypes with ethnically matched control chromosomes. This haplotype was used together with demographic data for Pakistan to estimate the age of this founder mutation. Results We identified a small homozygous 0.694 Mb region around the KCNJ10 p.R65P mutation that had identical haplotypes in all of the patients which were completely absent in the control sample. Based on current demographic data and knowledge about disease frequency, we estimate that this particular p.R65P mutation arose 20 generations (about 500 years) ago. Conclusion By knowing the prevalent mutation in a given population more efficient diagnostics can be performed and the families can benefit from specific counseling.
Collapse
Affiliation(s)
- Ola Abdelhadi
- Centre for Nephrology University College London London UK
| | - Daniela Iancu
- Centre for Nephrology University College London London UK
| | - Mehmet Tekman
- Centre for Nephrology University College London London UK
| | - Horia Stanescu
- Centre for Nephrology University College London London UK
| | | | - Robert Kleta
- Centre for Nephrology University College London London UK
| |
Collapse
|
29
|
Abdelhadi O, Iancu D, Stanescu H, Kleta R, Bockenhauer D. EAST syndrome: Clinical, pathophysiological, and genetic aspects of mutations in KCNJ10. Rare Dis 2016; 4:e1195043. [PMID: 27500072 PMCID: PMC4961265 DOI: 10.1080/21675511.2016.1195043] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/02/2016] [Accepted: 05/24/2016] [Indexed: 11/04/2022] Open
Abstract
EAST syndrome is a recently described autosomal recessive disorder secondary to mutations in KCNJ10 (Kir4.1), a gene encoding a potassium channel expressed in the brain, eye, ear and kidney. This condition is characterized by 4 cardinal features; Epilepsy, Ataxia, Sensorineural deafness, and (a renal salt-wasting) Tubulopathy, hence the acronym EAST syndrome. Here we review reported clinical manifestations, in particular the neurological signs and symptoms which typically have the most impact on the quality of life of patients. In addition we review the pathophysiology and genetic aspects of the disease. So far 14 different KCNJ10 mutations have been published which either directly affect channel function or may lead to mislocalisation. Investigations of the pathophysiology may provide clues to potential treatments.
Collapse
Affiliation(s)
- Ola Abdelhadi
- Center for Nephrology, University College London, London, UK
| | - Daniela Iancu
- Center for Nephrology, University College London, London, UK
| | - Horia Stanescu
- Center for Nephrology, University College London, London, UK
| | - Robert Kleta
- Center for Nephrology, University College London, London, UK
| | | |
Collapse
|
30
|
Crucial role of astrocytes in temporal lobe epilepsy. Neuroscience 2016; 323:157-69. [DOI: 10.1016/j.neuroscience.2014.12.047] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 12/25/2014] [Accepted: 12/30/2014] [Indexed: 11/30/2022]
|
31
|
Rodríguez-Menchaca AA, Aréchiga-Figueroa IA, Sánchez-Chapula JA. The molecular basis of chloroethylclonidine block of inward rectifier (Kir2.1 and Kir4.1) K + channels. Pharmacol Rep 2016; 68:383-9. [DOI: 10.1016/j.pharep.2015.10.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 09/28/2015] [Accepted: 10/12/2015] [Indexed: 10/22/2022]
|
32
|
Weller J, Steinhäuser C, Seifert G. pH-Sensitive K+ Currents and Properties of K2P Channels in Murine Hippocampal Astrocytes. ION CHANNELS AS THERAPEUTIC TARGETS, PART A 2016; 103:263-94. [DOI: 10.1016/bs.apcsb.2015.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
33
|
Abstract
More than two dozen types of potassium channels, with different biophysical and regulatory properties, are expressed in the kidney, influencing renal function in many important ways. Recently, a confluence of discoveries in areas from human genetics to physiology, cell biology, and biophysics has cast light on the special function of five different potassium channels in the distal nephron, encoded by the genes KCNJ1, KCNJ10, KCNJ16, KCNMA1, and KCNN3. Research aimed at understanding how these channels work in health and go awry in disease has transformed our understanding of potassium balance and provided new insights into mechanisms of renal sodium handling and the maintenance of blood pressure. This review focuses on recent advances in this rapidly evolving field.
Collapse
Affiliation(s)
- Paul A Welling
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201;
| |
Collapse
|
34
|
Isoform-specific dynamic translocation of PKC by α1-adrenoceptor stimulation in live cells. Biochem Biophys Res Commun 2015; 465:464-70. [PMID: 26277396 DOI: 10.1016/j.bbrc.2015.08.040] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 08/09/2015] [Indexed: 11/23/2022]
Abstract
Protein kinase C (PKC) plays key roles in the regulation of signal transduction and cellular function in various cell types. At least ten PKC isoforms have been identified and intracellular localization and trafficking of these individual isoforms are important for regulation of enzyme activity and substrate specificity. PKC can be activated downstream of Gq-protein coupled receptor (GqPCR) signaling and translocate to various cellular compartments including plasma membrane (PM). Recent reports suggested that different types of GqPCRs would activate different PKC isoforms (classic, novel and atypical PKCs) with different trafficking patterns. However, the knowledge of isoform-specific activation of PKC by each GqPCR is limited. α1-Adrenoceptor (α1-AR) is one of the GqPCRs highly expressed in the cardiovascular system. In this study, we examined the isoform-specific dynamic translocation of PKC in living HEK293T cells by α1-AR stimulation (α1-ARS). Rat PKCα, βI, βII, δ, ε and ζ fused with GFP at C-term were co-transfected with human α1A-AR into HEK293T cells. The isoform-specific dynamic translocation of PKC in living HEK293T cells by α1-ARS using phenylephrine was measured by confocal microscopy. Before stimulation, GFP-PKCs were localized at cytosolic region. α1-ARS strongly and rapidly translocated a classical PKC (cPKC), PKCα, (<30 s) to PM, with PKCα returning diffusively into the cytosol within 5 min. α1-ARS rapidly translocated other cPKCs, PKCβI and PKCβII, to the PM (<30 s), with sustained membrane localization. One novel PKC (nPKC), PKCε, but not another nPKC, PKCδ, was translocated by α1-AR stimulation to the PM (<30 s) and its membrane localization was also sustained. Finally, α1-AR stimulation did not cause a diacylglycerol-insensitive atypical PKC, PKCζ translocation. Our data suggest that PKCα, β and ε activation may underlie physiological and pathophysiological responses of α1-AR signaling for the phosphorylation of membrane-associated substrates including ion-channel and transporter proteins in the cardiovascular system.
Collapse
|
35
|
Wang L, Zhang C, Su X, Lin DH, Wang W. Caveolin-1 Deficiency Inhibits the Basolateral K+ Channels in the Distal Convoluted Tubule and Impairs Renal K+ and Mg2+ Transport. J Am Soc Nephrol 2015; 26:2678-90. [PMID: 25848073 DOI: 10.1681/asn.2014070658] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 12/22/2014] [Indexed: 01/28/2023] Open
Abstract
Kcnj10 encodes the inwardly rectifying K(+) channel Kir4.1 in the basolateral membrane of the distal convoluted tubule (DCT) and is activated by c-Src. However, the regulation and function of this K(+) channel are incompletely characterized. Here, patch-clamp experiments in Kcnj10-transfected HEK293 cells demonstrated that c-Src-induced stimulation of Kcnj10 requires coexpression of caveolin-1 (cav-1), and immunostaining showed expression of cav-1 in the basolateral membrane of parvalbumin-positive DCT. Patch-clamp experiments detected a 40-pS inwardly rectifying K(+) channel, a heterotetramer of Kir4.1/Kir5.1, in the basolateral membrane of the early DCT (DCT1) in both wild-type (WT) and cav-1-knockout (KO) mice. However, the activity of this basolateral 40-pS K(+) channel was lower in KO mice than in WT mice. Moreover, the K(+) reversal potential (an indication of membrane potential) was less negative in the DCT1 of KO mice than in the DCT1 of WT mice. Western blot analysis demonstrated that cav-1 deficiency decreased the expression of the Na(+)/Cl(-) cotransporter and Ste20-proline-alanine-rich kinase (SPAK) but increased the expression of epithelial Na(+) channel-α. Furthermore, the urinary excretion of Mg(2+) and K(+) was significantly higher in KO mice than in WT mice, and KO mice developed hypomagnesemia, hypocalcemia, and hypokalemia. We conclude that disruption of cav-1 decreases basolateral K(+) channel activity and depolarizes the cell membrane potential in the DCT1 at least in part by suppressing the stimulatory effect of c-Src on Kcnj10. Furthermore, the decrease in Kcnj10 and Na(+)/Cl(-) cotransporter expression induced by cav-1 deficiency may underlie the compromised renal transport of Mg(2+), Ca(2+), and K(+).
Collapse
Affiliation(s)
- Lijun Wang
- Department of Physiology, Harbin Medical University, Harbin, China; Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, New York; and Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou, China
| | - Xiaotong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Wenhui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| |
Collapse
|
36
|
Abstract
Astrocytes express ion channels, transmitter receptors, and transporters and, thus, are endowed with the machinery to sense and respond to neuronal activity. Recent studies have implicated that astrocytes play important roles in physiology, but these cells also emerge as crucial actors in epilepsy. Astrocytes are abundantly coupled through gap junctions allowing them to redistribute elevated K(+) and transmitter concentrations from sites of enhanced neuronal activity. Investigation of specimens from patients with pharmacoresistant temporal lobe epilepsy and epilepsy models revealed alterations in expression, localization, and function of astroglial K(+) and water channels. In addition, malfunction of glutamate transporters and the astrocytic glutamate-converting enzyme, glutamine synthetase, has been observed in epileptic tissue. These findings suggest that dysfunctional astrocytes are crucial players in epilepsy and should be considered as promising targets for new therapeutic strategies.
Collapse
Affiliation(s)
- Douglas A Coulter
- Departments of Pediatrics and Neuroscience, Perelman School of Medicine, University of Pennsylvania and the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104-4318
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53105 Bonn, Germany
| |
Collapse
|
37
|
Cheng CJ, Sung CC, Huang CL, Lin SH. Inward-rectifying potassium channelopathies: new insights into disorders of sodium and potassium homeostasis. Pediatr Nephrol 2015; 30:373-83. [PMID: 24899236 DOI: 10.1007/s00467-014-2764-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/11/2013] [Accepted: 01/10/2014] [Indexed: 11/30/2022]
Abstract
Inward-rectifying potassium (Kir) channels allow more inward than outward potassium flux when channels are open in mammalian cells. At physiological resting membrane potentials, however, they predominantly mediate outward potassium flux and play important roles in regulating the resting membrane potential in diverse cell types and potassium secretion in the kidneys. Mutations of Kir channels cause human hereditary diseases collectively called Kir channelopathies, many of which are characterized by disorders of sodium and potassium homeostasis. Studies on these genetic Kir channelopathies have shed light on novel pathophysiological mechanisms, including renal sodium and potassium handling, potassium shifting in skeletal muscles, and aldosterone production in the adrenal glands. Here, we review several recent advances in Kir channels and their clinical implications in sodium and potassium homeostasis.
Collapse
Affiliation(s)
- Chih-Jen Cheng
- Department of Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Neihu 114, Taipei, Taiwan
| | | | | | | |
Collapse
|
38
|
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.
Collapse
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
| |
Collapse
|
39
|
Mutational Consequences of Aberrant Ion Channels in Neurological Disorders. J Membr Biol 2014; 247:1083-127. [DOI: 10.1007/s00232-014-9716-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Accepted: 07/25/2014] [Indexed: 12/25/2022]
|
40
|
Zhang C, Wang L, Zhang J, Su XT, Lin DH, Scholl UI, Giebisch G, Lifton RP, Wang WH. KCNJ10 determines the expression of the apical Na-Cl cotransporter (NCC) in the early distal convoluted tubule (DCT1). Proc Natl Acad Sci U S A 2014; 111:11864-9. [PMID: 25071208 PMCID: PMC4136599 DOI: 10.1073/pnas.1411705111] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The renal phenotype induced by loss-of-function mutations of inwardly rectifying potassium channel (Kir), Kcnj10 (Kir4.1), includes salt wasting, hypomagnesemia, metabolic alkalosis and hypokalemia. However, the mechanism by which Kir.4.1 mutations cause the tubulopathy is not completely understood. Here we demonstrate that Kcnj10 is a main contributor to the basolateral K conductance in the early distal convoluted tubule (DCT1) and determines the expression of the apical Na-Cl cotransporter (NCC) in the DCT. Immunostaining demonstrated Kcnj10 and Kcnj16 were expressed in the basolateral membrane of DCT, and patch-clamp studies detected a 40-pS K channel in the basolateral membrane of the DCT1 of p8/p10 wild-type Kcnj10(+/+) mice (WT). This 40-pS K channel is absent in homozygous Kcnj10(-/-) (knockout) mice. The disruption of Kcnj10 almost completely eliminated the basolateral K conductance and decreased the negativity of the cell membrane potential in DCT1. Moreover, the lack of Kcnj10 decreased the basolateral Cl conductance, inhibited the expression of Ste20-related proline-alanine-rich kinase and diminished the apical NCC expression in DCT. We conclude that Kcnj10 plays a dominant role in determining the basolateral K conductance and membrane potential of DCT1 and that the basolateral K channel activity in the DCT determines the apical NCC expression possibly through a Ste20-related proline-alanine-rich kinase-dependent mechanism.
Collapse
Affiliation(s)
- Chengbiao Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou 221002, China;Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Lijun Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Junhui Zhang
- Department of Genetics, Howard Hughes Medical Institute, and
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Ute I Scholl
- Department of Genetics, Howard Hughes Medical Institute, and
| | - Gerhard Giebisch
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510
| | | | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| |
Collapse
|
41
|
Tanemoto M, Abe T, Uchida S, Kawahara K. Mislocalization of K+ channels causes the renal salt wasting in EAST/SeSAME syndrome. FEBS Lett 2014; 588:899-905. [PMID: 24561201 DOI: 10.1016/j.febslet.2014.02.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 02/03/2014] [Indexed: 01/12/2023]
Abstract
The Kir4.1/Kir5.1 channel mediates basolateral K(+) recycling in renal distal tubules; this process is critical for Na(+) reabsorption at the tubules. Mutations in Kir4.1 are associated with EAST/SeSAME syndrome, a genetic disorder characterized by renal salt wasting. In this study, we found that MAGI-1 anchors Kir4.1 channels (Kir4.1 homomer and Kir4.1/Kir5.1 heteromer) and contributes to basolateral K(+) recycling. The Kir4.1 A167V mutation associated with EAST/SeSAME syndrome caused mistrafficking of the mutant channels and inhibited their expression on the basolateral surface of tubular cells. These findings suggest mislocalization of the Kir4.1 channels contributes to renal salt wasting.
Collapse
Affiliation(s)
- Masayuki Tanemoto
- Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo 174-8605, Japan.
| | - Takaaki Abe
- Division of Medical Science, Tohoku University Graduate School of Biomedical Engineering, Sendai 980-8575, Japan
| | - Shunya Uchida
- Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo 174-8605, Japan
| | - Katsumasa Kawahara
- Department of Cellular and Molecular Physiology, Kitasato University Graduate School of Medical Sciences, Sagamihara 252-0374, Japan
| |
Collapse
|
42
|
Chen J, Zhao HB. The role of an inwardly rectifying K(+) channel (Kir4.1) in the inner ear and hearing loss. Neuroscience 2014; 265:137-46. [PMID: 24480364 DOI: 10.1016/j.neuroscience.2014.01.036] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 01/16/2014] [Accepted: 01/18/2014] [Indexed: 11/18/2022]
Abstract
The KCNJ10 gene which encodes an inwardly rectifying K(+) channel Kir4.1 subunit plays an essential role in the inner ear and hearing. Mutations or deficiency of KCNJ10 can cause hearing loss with EAST or SeSAME syndromes. This review mainly focuses on the expression and function of Kir4.1 potassium channels in the inner ear and hearing. We first introduce general information about inwardly rectifying potassium (Kir) channels. Then, we review the expression and function of Kir4.1 channels in the inner ear, especially in endocochlear potential (EP) generation. Finally, we review KCNJ10 mutation-induced hearing loss and functional impairments. Kir4.1 is strongly expressed on the apical membrane of intermediate cells in the stria vascularis and in the satellite cells of cochlear ganglia. Functionally, Kir4.1 has critical roles in cochlear development and hearing through two distinct aspects of extracellular K(+) homeostasis: First, it participates in the generation and maintenance of EP and high K(+) concentration in the endolymph inside the scala media. Second, Kir4.1 is the major K(+) channel in satellite glial cells surrounding spiral ganglion neurons to sink K(+) ions expelled by the ganglion neurons during excitation. Kir4.1 deficiency leads to hearing loss with the absence of EP and spiral ganglion neuron degeneration. Deafness mutants show loss-of-function and reduced channel membrane-targeting and currents, which can be rescued upon by co-expression with wild-type Kir4.1. This review provides insights for further understanding Kir potassium channel function in the inner ear and the pathogenesis of deafness due to KCNJ10 deficiency, and also provides insights for developing therapeutic strategies targeting this deafness.
Collapse
Affiliation(s)
- J Chen
- Department of Morphology, Medical College of China Three Gorges University, Yichang, Hubei 443002, PR China; Department of Otolaryngology, University of Kentucky Medical Center, Lexington, KY 40536-0293, USA
| | - H-B Zhao
- Department of Otolaryngology, University of Kentucky Medical Center, Lexington, KY 40536-0293, USA.
| |
Collapse
|
43
|
Tian C, Zhu R, Zhu L, Qiu T, Cao Z, Kang T. Potassium Channels: Structures, Diseases, and Modulators. Chem Biol Drug Des 2013; 83:1-26. [DOI: 10.1111/cbdd.12237] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Chuan Tian
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
| | - Ruixin Zhu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Lixin Zhu
- Department of Pediatrics; Digestive Diseases and Nutrition Center; The State University of New York at Buffalo; Buffalo NY 14226 USA
| | - Tianyi Qiu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Zhiwei Cao
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Tingguo Kang
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
| |
Collapse
|
44
|
Altered Kir and gap junction channels in temporal lobe epilepsy. Neurochem Int 2013; 63:682-7. [DOI: 10.1016/j.neuint.2013.01.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 12/13/2012] [Accepted: 01/09/2013] [Indexed: 12/12/2022]
|
45
|
Parrock S, Hussain S, Issler N, Differ AM, Lench N, Guarino S, Oosterveld MJS, Keijzer-Veen M, Brilstra E, van Wieringen H, Konijnenberg AY, Amin-Rasip S, Dumitriu S, Klootwijk E, Knoers N, Bockenhauer D, Kleta R, Zdebik AA. KCNJ10 mutations display differential sensitivity to heteromerisation with KCNJ16. Nephron Clin Pract 2013; 123:7-14. [PMID: 24193250 DOI: 10.1159/000356353] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 10/16/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Mutations in the inwardly-rectifying K(+)-channel KCNJ10/Kir4.1 cause autosomal recessive EAST syndrome (epilepsy, ataxia, sensorineural deafness and tubulopathy). KCNJ10 is expressed in the distal convoluted tubule of the kidney, stria vascularis of the inner ear and brain glial cells. Patients diagnosed clinically with EAST syndrome were genotyped and mutations in KCNJ10 were studied functionally. METHODS Patient DNA was amplified and sequenced, and new mutations were identified. Mutant and wild-type KCNJ10 constructs were cloned and heterologously expressed in Xenopus oocytes. Whole-cell K(+) currents were measured by 2-electrode voltage clamping and channel expression was analysed by Western blotting. RESULTS We identified 3 homozygous mutations in KCNJ10 (p.F75C, p.A167V and p.V91fs197X), with mutation p.A167V previously reported in a compound heterozygous state. Oocytes expressing wild-type human KCNJ10 showed inwardly rectified currents, which were significantly reduced in all of the mutants (p < 0.001). Specific inhibition of KCNJ10 currents by Ba(2+) demonstrated a large residual function in p.A167V only, which was not compatible with causing disease. However, co-expression with KCNJ16 abolished function in these heteromeric channels almost completely. CONCLUSION This study provides an explanation for the pathophysiology of the p.A167V KCNJ10 mutation, which had previously not been considered pathogenic on its own. These findings provide evidence for the functional cooperation of KCNJ10 and KCNJ16. Thus, in vitro ascertainment of KCNJ10 function may necessitate co-expression with KCNJ16.
Collapse
Affiliation(s)
- Sophie Parrock
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Takeda I, Takahashi T, Ueno H, Morino H, Ochi K, Nakamura T, Hosomi N, Kawakami H, Hashimoto K, Matsumoto M. Autosomal recessive Andersen-Tawil syndrome with a novel mutation L94P in Kir2.1. ACTA ACUST UNITED AC 2013. [DOI: 10.1111/ncn3.38] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ikuko Takeda
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Tetsuya Takahashi
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Hiroki Ueno
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Hiroyuki Morino
- Department of Epidemiology; Research Institute for Radiation Biology and Medicine; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Kazuhide Ochi
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Takeshi Nakamura
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Naohisa Hosomi
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Hideshi Kawakami
- Department of Epidemiology; Research Institute for Radiation Biology and Medicine; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Kouichi Hashimoto
- Department of Neurophysiology; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Masayasu Matsumoto
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| |
Collapse
|
47
|
Zhang C, Wang L, Thomas S, Wang K, Lin DH, Rinehart J, Wang WH. Src family protein tyrosine kinase regulates the basolateral K channel in the distal convoluted tubule (DCT) by phosphorylation of KCNJ10 protein. J Biol Chem 2013; 288:26135-26146. [PMID: 23873931 DOI: 10.1074/jbc.m113.478453] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The loss of function of the basolateral K channels in the distal nephron causes electrolyte imbalance. The aim of this study is to examine the role of Src family protein tyrosine kinase (SFK) in regulating K channels in the basolateral membrane of the mouse initial distal convoluted tubule (DCT1). Single-channel recordings confirmed that the 40-picosiemen (pS) K channel was the only type of K channel in the basolateral membrane of DCT1. The suppression of SFK reversibly inhibited the basolateral 40-pS K channel activity in cell-attached patches and decreased the Ba(2+)-sensitive whole-cell K currents in DCT1. Inhibition of SFK also shifted the K reversal potential from -65 to -43 mV, suggesting a role of SFK in determining the membrane potential in DCT1. Western blot analysis showed that KCNJ10 (Kir4.1), a key component of the basolateral 40-pS K channel in DCT1, was a tyrosine-phosphorylated protein. LC/MS analysis further confirmed that SFK phosphorylated KCNJ10 at Tyr(8) and Tyr(9). The single-channel recording detected the activity of a 19-pS K channel in KCNJ10-transfected HEK293T cells and a 40-pS K channel in the cells transfected with KCNJ10+KCNJ16 (Kir.5.1) that form a heterotetramer in the basolateral membrane of the DCT. Mutation of Tyr(9) did not alter the channel conductance of the homotetramer and heterotetramer. However, it decreased the whole-cell K currents, the probability of finding K channels, and surface expression of KCNJ10 in comparison to WT KCNJ10. We conclude that SFK stimulates the basolateral K channel activity in DCT1, at least partially, by phosphorylating Tyr(9) on KCNJ10. We speculate that the modulation of tyrosine phosphorylation of KCNJ10 should play a role in regulating membrane transport function in DCT1.
Collapse
Affiliation(s)
- Chengbiao Zhang
- From the Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou, Jiangsu 221002, China,; the Department of Pharmacology, New York Medical College, Valhalla, New York 10595
| | - Lijun Wang
- the Department of Pharmacology, New York Medical College, Valhalla, New York 10595
| | - Sherin Thomas
- the Department of Pharmacology, New York Medical College, Valhalla, New York 10595
| | - Kemeng Wang
- the Department of Pharmacology, New York Medical College, Valhalla, New York 10595
| | - Dao-Hong Lin
- the Department of Pharmacology, New York Medical College, Valhalla, New York 10595
| | - Jesse Rinehart
- the Department of Cellular and Molecular Physiology and; Systems Biology Institute, Yale University, New Haven, Connecticut 06520
| | - Wen-Hui Wang
- the Department of Pharmacology, New York Medical College, Valhalla, New York 10595,.
| |
Collapse
|
48
|
Seifert G, Steinhäuser C. Neuron–astrocyte signaling and epilepsy. Exp Neurol 2013; 244:4-10. [DOI: 10.1016/j.expneurol.2011.08.024] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 08/16/2011] [Accepted: 08/25/2011] [Indexed: 12/30/2022]
|
49
|
Imbrici P, Camerino DC, Tricarico D. Major channels involved in neuropsychiatric disorders and therapeutic perspectives. Front Genet 2013; 4:76. [PMID: 23675382 PMCID: PMC3646240 DOI: 10.3389/fgene.2013.00076] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/16/2013] [Indexed: 12/11/2022] Open
Abstract
Voltage-gated ion channels are important mediators of physiological functions in the central nervous system. The cyclic activation of these channels influences neurotransmitter release, neuron excitability, gene transcription, and plasticity, providing distinct brain areas with unique physiological and pharmacological response. A growing body of data has implicated ion channels in the susceptibility or pathogenesis of psychiatric diseases. Indeed, population studies support the association of polymorphisms in calcium and potassium channels with the genetic risk for bipolar disorders (BPDs) or schizophrenia. Moreover, point mutations in calcium, sodium, and potassium channel genes have been identified in some childhood developmental disorders. Finally, antibodies against potassium channel complexes occur in a series of autoimmune psychiatric diseases. Here we report recent studies assessing the role of calcium, sodium, and potassium channels in BPD, schizophrenia, and autism spectrum disorders, and briefly summarize promising pharmacological strategies targeted on ion channels for the therapy of mental illness and related genetic tests.
Collapse
Affiliation(s)
- Paola Imbrici
- Section of Pharmacology, Department of Pharmacy - Drug Science, University of Bari Bari, Italy
| | | | | |
Collapse
|
50
|
Hamilton KL, Devor DC. Basolateral membrane K+ channels in renal epithelial cells. Am J Physiol Renal Physiol 2012; 302:F1069-81. [PMID: 22338089 DOI: 10.1152/ajprenal.00646.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The major function of epithelial tissues is to maintain proper ion, solute, and water homeostasis. The tubule of the renal nephron has an amazingly simple structure, lined by epithelial cells, yet the segments (i.e., proximal tubule vs. collecting duct) of the nephron have unique transport functions. The functional differences are because epithelial cells are polarized and thus possess different patterns (distributions) of membrane transport proteins in the apical and basolateral membranes of the cell. K(+) channels play critical roles in normal physiology. Over 90 different genes for K(+) channels have been identified in the human genome. Epithelial K(+) channels can be located within either or both the apical and basolateral membranes of the cell. One of the primary functions of basolateral K(+) channels is to recycle K(+) across the basolateral membrane for proper function of the Na(+)-K(+)-ATPase, among other functions. Mutations of these channels can cause significant disease. The focus of this review is to provide an overview of the basolateral K(+) channels of the nephron, providing potential physiological functions and pathophysiology of these channels, where appropriate. We have taken a "K(+) channel gene family" approach in presenting the representative basolateral K(+) channels of the nephron. The basolateral K(+) channels of the renal epithelia are represented by members of the KCNK, KCNJ, KCNQ, KCNE, and SLO gene families.
Collapse
Affiliation(s)
- Kirk L Hamilton
- Department of Physiology, Otago School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
| | | |
Collapse
|