1
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Ragupathi A, Kim C, Jacinto E. The mTORC2 signaling network: targets and cross-talks. Biochem J 2024; 481:45-91. [PMID: 38270460 PMCID: PMC10903481 DOI: 10.1042/bcj20220325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/29/2023] [Accepted: 12/18/2023] [Indexed: 01/26/2024]
Abstract
The mechanistic target of rapamycin, mTOR, controls cell metabolism in response to growth signals and stress stimuli. The cellular functions of mTOR are mediated by two distinct protein complexes, mTOR complex 1 (mTORC1) and mTORC2. Rapamycin and its analogs are currently used in the clinic to treat a variety of diseases and have been instrumental in delineating the functions of its direct target, mTORC1. Despite the lack of a specific mTORC2 inhibitor, genetic studies that disrupt mTORC2 expression unravel the functions of this more elusive mTOR complex. Like mTORC1 which responds to growth signals, mTORC2 is also activated by anabolic signals but is additionally triggered by stress. mTORC2 mediates signals from growth factor receptors and G-protein coupled receptors. How stress conditions such as nutrient limitation modulate mTORC2 activation to allow metabolic reprogramming and ensure cell survival remains poorly understood. A variety of downstream effectors of mTORC2 have been identified but the most well-characterized mTORC2 substrates include Akt, PKC, and SGK, which are members of the AGC protein kinase family. Here, we review how mTORC2 is regulated by cellular stimuli including how compartmentalization and modulation of complex components affect mTORC2 signaling. We elaborate on how phosphorylation of its substrates, particularly the AGC kinases, mediates its diverse functions in growth, proliferation, survival, and differentiation. We discuss other signaling and metabolic components that cross-talk with mTORC2 and the cellular output of these signals. Lastly, we consider how to more effectively target the mTORC2 pathway to treat diseases that have deregulated mTOR signaling.
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Affiliation(s)
- Aparna Ragupathi
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
| | - Christian Kim
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
| | - Estela Jacinto
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
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2
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Kalashyan M, Raghunathan K, Oller H, Bayer MT, Jimenez L, Roland JT, Kolobova E, Hagen SJ, Goldsmith JD, Shub MD, Goldenring JR, Kaji I, Thiagarajah JR. Patient-derived enteroids provide a platform for the development of therapeutic approaches in microvillus inclusion disease. J Clin Invest 2023; 133:e169234. [PMID: 37643022 PMCID: PMC10575727 DOI: 10.1172/jci169234] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 08/22/2023] [Indexed: 08/31/2023] Open
Abstract
Microvillus inclusion disease (MVID), caused by loss-of-function mutations in the motor protein myosin Vb (MYO5B), is a severe infantile disease characterized by diarrhea, malabsorption, and acid/base instability, requiring intensive parenteral support for nutritional and fluid management. Human patient-derived enteroids represent a model for investigation of monogenic epithelial disorders but are a rare resource from MVID patients. We developed human enteroids with different loss-of function MYO5B variants and showed that they recapitulated the structural changes found in native MVID enterocytes. Multiplex immunofluorescence imaging of patient duodenal tissues revealed patient-specific changes in localization of brush border transporters. Functional analysis of electrolyte transport revealed profound loss of Na+/H+ exchange (NHE) activity in MVID patient enteroids with near-normal chloride secretion. The chloride channel-blocking antidiarrheal drug crofelemer dose-dependently inhibited agonist-mediated fluid secretion. MVID enteroids exhibited altered differentiation and maturation versus healthy enteroids. γ-Secretase inhibition with DAPT recovered apical brush border structure and functional Na+/H+ exchange activity in MVID enteroids. Transcriptomic analysis revealed potential pathways involved in the rescue of MVID cells including serum/glucocorticoid-regulated kinase 2 (SGK2) and NHE regulatory factor 3 (NHERF3). These results demonstrate the utility of patient-derived enteroids for developing therapeutic approaches to MVID.
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Affiliation(s)
- Meri Kalashyan
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Krishnan Raghunathan
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Haley Oller
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Marie-Theres Bayer
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Lissette Jimenez
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
- Congenital Enteropathy Program, Boston Children’s Hospital, Boston, Massachusetts, USA
- PediCODE Consortium, as detailed in Supplemental Acknowledgments
| | - Joseph T. Roland
- Section of Surgical Sciences and
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Elena Kolobova
- Section of Surgical Sciences and
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Susan J. Hagen
- Department of Surgery, Division of Surgical Sciences, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Jeffrey D. Goldsmith
- PediCODE Consortium, as detailed in Supplemental Acknowledgments
- Department of Pathology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Mitchell D. Shub
- Department of Child Health, University of Arizona College of Medicine–Phoenix, and Division of Gastroenterology, Phoenix Children’s Hospital, Phoenix, Arizona, USA
| | - James R. Goldenring
- PediCODE Consortium, as detailed in Supplemental Acknowledgments
- Section of Surgical Sciences and
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Nashville VA Medical Center, Nashville, Tennessee, USA
| | - Izumi Kaji
- PediCODE Consortium, as detailed in Supplemental Acknowledgments
- Section of Surgical Sciences and
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Jay R. Thiagarajah
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
- Congenital Enteropathy Program, Boston Children’s Hospital, Boston, Massachusetts, USA
- PediCODE Consortium, as detailed in Supplemental Acknowledgments
- Harvard Digestive Disease Center, Boston, Massachusetts, USA
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3
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Wang J, Wang L, Wang Z, Lv M, Fu J, Zhang Y, Qiu P, Shi D, Luo C. Vitamin C down-regulates the H3K9me3-dependent heterochromatin in buffalo fibroblasts via PI3K/PDK1/SGK1/KDM4A signal axis. Theriogenology 2023; 200:114-124. [PMID: 36805248 DOI: 10.1016/j.theriogenology.2023.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 02/02/2023] [Accepted: 02/02/2023] [Indexed: 02/11/2023]
Abstract
The success of reprogramming is dependent on the reprogramming factors enriched in the cytoplasm of recipient oocytes and the potential of donor nucleus to be reprogrammed. Histone 3 lysine 9 trimethylation (H3K9me3) was identified as a major epigenetic barrier impeding complete reprogramming. Treating donor cell with vitamin C (Vc) can enhance the developmental potential of cloned embryos, but the underlying mechanisms still need to be elucidated. In this study, we found that 20μg/mL Vc could promote proliferation and inhibit apoptosis of BFFs, as well as down-regulate the H3K9me3-dependent heterochromatin and increase chromatin accessibility. Inhibited the expression of KDM4A resulted in increasing apoptosis rate and the H3K9me3-dependent heterochromatin, which can be restored by Vc. Moreover, Vc up-regulated the expression of KDM4A through PI3K/PDK1/SGK1 pathway. Inhibiting any factor in the signal axis of this PI3K pathway not only suppressed the activity of KDM4A but also substantially increased the level of H3K9me3 modification and the expression of the HP1α protein. Finally, Vc can rescue those negative effects induced by the blocking the PI3K/PDK1/SGK1 pathway. Collectively, Vc can down-regulate the H3K9me3-dependent heterochromatin in BFFs via PI3K/PDK1/SGK1/KDM4A signal axis, suggesting that Vc can turn the chromatin status of donor cells to be reprogrammed more easily.
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Affiliation(s)
- Jinling Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China
| | - Lei Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China
| | - Zhiqiang Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; Guangxi Academy of Medical Sciences and the People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Meiyun Lv
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China
| | - Jiayuan Fu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China
| | - Yunchuan Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China
| | - Peng Qiu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China
| | - Deshun Shi
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China.
| | - Chan Luo
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi Key Laboratory of Animal Reproduction, Breeding and Disease Control, Guangxi University, 75 Xiuling Road, Nanning, 530005, China; College of Animal Science and Technology, Guangxi University, 75 Xiuling Road, Nanning, 530005, China.
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4
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Kalashyan M, Raghunathan K, Oller H, Theres MB, Jimenez L, Roland JT, Kolobova E, Hagen SJ, Goldsmith JD, Shub MD, Goldenring JR, Kaji I, Thiagarajah JR. Therapy Development for Microvillus Inclusion Disease using Patient-derived Enteroids. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.28.526036. [PMID: 36747680 PMCID: PMC9900906 DOI: 10.1101/2023.01.28.526036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Microvillus Inclusion Disease (MVID), caused by loss-of-function mutations in the motor protein Myosin Vb (MYO5B), is a severe infantile disease characterized by diarrhea, malabsorption, and acid-base instability, requiring intensive parenteral support for nutritional and fluid management. Human patient-derived enteroids represent a model for investigation of monogenic epithelial disorders but are a rare resource from MVID patients. We developed human enteroids with different loss-of function MYO5B variants and showed that they recapitulated the structural changes found in native MVID enterocytes. Multiplex Immunofluorescence imaging of patient duodenal tissues revealed patient-specific changes in localization of brush border transporters. Functional analysis of electrolyte transport revealed profound loss of Na + /H + exchange (NHE) activity in MVID patient enteroids with near-normal chloride secretion. The chloride channel-blocking anti-diarrheal drug, Crofelemer, dose-dependently inhibited agonist-mediated fluid secretion. MVID enteroids exhibited altered differentiation and maturation versus healthy enteroids. Inhibition of Notch signaling with the γ-secretase inhibitor, DAPT, recovered apical brush border structure and functional Na + /H + exchange activity in MVID enteroids. Transcriptomic analysis revealed potential pathways involved in the rescue of MVID cells including serum- and glucocorticoid-induced protein kinase 2 (SGK2), and NHE regulatory factor 3 (NHERF3). These results demonstrate the utility of patient-derived enteroids for developing therapeutic approaches to MVID. Conflict-of-interest statement The authors have declared that no conflict of interest exists.
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Affiliation(s)
- Meri Kalashyan
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital; Harvard Medical School, Boston, MA
| | - Krishnan Raghunathan
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital; Harvard Medical School, Boston, MA
| | - Haley Oller
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital; Harvard Medical School, Boston, MA
| | - Marie-Bayer Theres
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital; Harvard Medical School, Boston, MA
| | - Lissette Jimenez
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital; Harvard Medical School, Boston, MA
- Congenital Enteropathy Program, Boston Children’s Hospital, Boston, MA
- PediCoDE Consortium
| | - Joseph T. Roland
- Section of Surgical Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Elena Kolobova
- Section of Surgical Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Susan J Hagen
- Department of Surgery, Division of Surgical Sciences, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Jeffrey D. Goldsmith
- Department of Pathology, Boston Children’s Hospital; Harvard Medical School, Boston, MA
- PediCoDE Consortium
| | - Mitchell D. Shub
- Department of Child Health University of Arizona College of Medicine-Phoenix and Division of Gastroenterology, Phoenix Children’s
| | - James R. Goldenring
- Section of Surgical Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee
- Nashville VA Medical Center, Nashville, TN
- PediCoDE Consortium
| | - Izumi Kaji
- Section of Surgical Sciences, Vanderbilt University Medical Center, Nashville, Tennessee
- Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee
- PediCoDE Consortium
| | - Jay R. Thiagarajah
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children’s Hospital; Harvard Medical School, Boston, MA
- Congenital Enteropathy Program, Boston Children’s Hospital, Boston, MA
- Harvard Digestive Disease Center, Boston MA
- PediCoDE Consortium
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5
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Leite APDO, Li XC, Nwia SM, Hassan R, Zhuo JL. Angiotensin II and AT 1a Receptors in the Proximal Tubules of the Kidney: New Roles in Blood Pressure Control and Hypertension. Int J Mol Sci 2022; 23:2402. [PMID: 35269547 PMCID: PMC8910592 DOI: 10.3390/ijms23052402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 02/15/2022] [Accepted: 02/18/2022] [Indexed: 02/01/2023] Open
Abstract
Contrary to public perception, hypertension remains one of the most important public health problems in the United States, affecting 46% of adults with increased risk for heart attack, stroke, and kidney diseases. The mechanisms underlying poorly controlled hypertension remain incompletely understood. Recent development in the Cre/LoxP approach to study gain or loss of function of a particular gene has significantly helped advance our new insights into the role of proximal tubule angiotensin II (Ang II) and its AT1 (AT1a) receptors in basal blood pressure control and the development of Ang II-induced hypertension. This novel approach has provided us and others with an important tool to generate novel mouse models with proximal tubule-specific loss (deletion) or gain of the function (overexpression). The objective of this invited review article is to review and discuss recent findings using novel genetically modifying proximal tubule-specific mouse models. These new studies have consistently demonstrated that deletion of AT1 (AT1a) receptors or its direct downstream target Na+/H+ exchanger 3 (NHE3) selectively in the proximal tubules of the kidney lowers basal blood pressure, increases the pressure-natriuresis response, and induces natriuretic responses, whereas overexpression of an intracellular Ang II fusion protein or AT1 (AT1a) receptors selectively in the proximal tubules increases proximal tubule Na+ reabsorption, impairs the pressure-natriuresis response, and elevates blood pressure. Furthermore, the development of Ang II-induced hypertension by systemic Ang II infusion or by proximal tubule-specific overexpression of an intracellular Ang II fusion protein was attenuated in mutant mice with proximal tubule-specific deletion of AT1 (AT1a) receptors or NHE3. Thus, these recent studies provide evidence for and new insights into the important roles of intratubular Ang II via AT1 (AT1a) receptors and NHE3 in the proximal tubules in maintaining basal blood pressure homeostasis and the development of Ang II-induced hypertension.
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Affiliation(s)
- Ana Paula de Oliveira Leite
- Tulane Hypertension and Renal Center of Excellence, 1430 Tulane Avenue, New Orleans, LA 70112, USA; (A.P.d.O.L.); (X.C.L.); (S.M.N.); (R.H.)
- Department of Physiology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Xiao C. Li
- Tulane Hypertension and Renal Center of Excellence, 1430 Tulane Avenue, New Orleans, LA 70112, USA; (A.P.d.O.L.); (X.C.L.); (S.M.N.); (R.H.)
- Department of Physiology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Sarah M. Nwia
- Tulane Hypertension and Renal Center of Excellence, 1430 Tulane Avenue, New Orleans, LA 70112, USA; (A.P.d.O.L.); (X.C.L.); (S.M.N.); (R.H.)
- Department of Physiology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Rumana Hassan
- Tulane Hypertension and Renal Center of Excellence, 1430 Tulane Avenue, New Orleans, LA 70112, USA; (A.P.d.O.L.); (X.C.L.); (S.M.N.); (R.H.)
- Department of Physiology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Jia L. Zhuo
- Tulane Hypertension and Renal Center of Excellence, 1430 Tulane Avenue, New Orleans, LA 70112, USA; (A.P.d.O.L.); (X.C.L.); (S.M.N.); (R.H.)
- Department of Physiology, Tulane University School of Medicine, New Orleans, LA 70112, USA
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6
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Pearce D, Manis AD, Nesterov V, Korbmacher C. Regulation of distal tubule sodium transport: mechanisms and roles in homeostasis and pathophysiology. Pflugers Arch 2022; 474:869-884. [PMID: 35895103 PMCID: PMC9338908 DOI: 10.1007/s00424-022-02732-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 07/09/2022] [Accepted: 07/11/2022] [Indexed: 02/03/2023]
Abstract
Regulated Na+ transport in the distal nephron is of fundamental importance to fluid and electrolyte homeostasis. Further upstream, Na+ is the principal driver of secondary active transport of numerous organic and inorganic solutes. In the distal nephron, Na+ continues to play a central role in controlling the body levels and concentrations of a more select group of ions, including K+, Ca++, Mg++, Cl-, and HCO3-, as well as water. Also, of paramount importance are transport mechanisms aimed at controlling the total level of Na+ itself in the body, as well as its concentrations in intracellular and extracellular compartments. Over the last several decades, the transporters involved in moving Na+ in the distal nephron, and directly or indirectly coupling its movement to that of other ions have been identified, and their interrelationships brought into focus. Just as importantly, the signaling systems and their components-kinases, ubiquitin ligases, phosphatases, transcription factors, and others-have also been identified and many of their actions elucidated. This review will touch on selected aspects of ion transport regulation, and its impact on fluid and electrolyte homeostasis. A particular focus will be on emerging evidence for site-specific regulation of the epithelial sodium channel (ENaC) and its role in both Na+ and K+ homeostasis. In this context, the critical regulatory roles of aldosterone, the mineralocorticoid receptor (MR), and the kinases SGK1 and mTORC2 will be highlighted. This includes a discussion of the newly established concept that local K+ concentrations are involved in the reciprocal regulation of Na+-Cl- cotransporter (NCC) and ENaC activity to adjust renal K+ secretion to dietary intake.
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Affiliation(s)
- David Pearce
- Department of Medicine, Division of Nephrology, and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA USA
| | - Anna D. Manis
- Department of Medicine, Division of Nephrology, and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA USA
| | - Viatcheslav Nesterov
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, Erlangen, Germany
| | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, Erlangen, Germany
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7
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Marcoux AA, Tremblay LE, Slimani S, Fiola MJ, Mac-Way F, Haydock L, Garneau AP, Isenring P. Anatomophysiology of the Henle's Loop: Emphasis on the Thick Ascending Limb. Compr Physiol 2021; 12:3119-3139. [PMID: 34964111 DOI: 10.1002/cphy.c210021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The loop of Henle plays a variety of important physiological roles through the concerted actions of ion transport systems in both its apical and basolateral membranes. It is involved most notably in extracellular fluid volume and blood pressure regulation as well as Ca2+ , Mg2+ , and acid-base homeostasis because of its ability to reclaim a large fraction of the ultrafiltered solute load. This nephron segment is also involved in urinary concentration by energizing several of the steps that are required to generate a gradient of increasing osmolality from cortex to medulla. Another important role of the loop of Henle is to sustain a process known as tubuloglomerular feedback through the presence of specialized renal tubular cells that lie next to the juxtaglomerular arterioles. This article aims at describing these physiological roles and at discussing a number of the molecular mechanisms involved. It will also report on novel findings and uncertainties regarding the realization of certain processes and on the pathophysiological consequences of perturbed salt handling by the thick ascending limb of the loop of Henle. Since its discovery 150 years ago, the loop of Henle has remained in the spotlight and is now generating further interest because of its role in the renal-sparing effect of SGLT2 inhibitors. © 2022 American Physiological Society. Compr Physiol 12:1-21, 2022.
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Affiliation(s)
- Andrée-Anne Marcoux
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Laurence E Tremblay
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Samira Slimani
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Marie-Jeanne Fiola
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Fabrice Mac-Way
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Ludwig Haydock
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Alexandre P Garneau
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada.,Cardiometabolic Axis, School of Kinesiology and Physical Activity Sciences, University of Montréal, Montréal, QC, Canada
| | - Paul Isenring
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
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8
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Park CH, Moon J, Park M, Cheng H, Lee J, Chang JS. Protein Kinase SGK2 Is Induced by the β 3 Adrenergic Receptor-cAMP-PKA-PGC-1α/NT-PGC-1α Axis but Dispensable for Brown/Beige Adipose Tissue Thermogenesis. Front Physiol 2021; 12:780312. [PMID: 34899399 PMCID: PMC8657153 DOI: 10.3389/fphys.2021.780312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 10/29/2021] [Indexed: 11/21/2022] Open
Abstract
Brown and beige adipocytes are specialized to dissipate energy as heat. Sgk2, encoding a serine/threonine kinase, has been identified as a brown and beige adipocyte-specific gene in rodents and humans; however, its function in brown/beige adipocytes remains unraveled. Here, we examined the regulation and role of Sgk2 in brown/beige adipose tissue thermogenesis. We found that transcriptional coactivators PGC-1α and NT-PGC-1α activated by the β3 adrenergic receptor-cAMP-PKA pathway are recruited to the Sgk2 promoter, triggering Sgk2 transcription in response to cold. SGK2 elevation was closely associated with increased serine/threonine phosphorylation of proteins carrying the consensus RxRxxS/T phosphorylation site. However, despite cold-dependent activation of SGK2, mice lacking Sgk2 exhibited normal cold tolerance at 4°C. In addition, Sgk2+/+ and Sgk2−/− mice induced comparable increases in energy expenditure during pharmacological activation of brown and beige adipose tissue with a β3AR agonist. In vitro loss- and gain-of-function studies further demonstrated that Sgk2 ablation or activation does not alter thermogenic gene expression and mitochondrial respiration in brown adipocytes. Collectively, our results reveal a new signaling component SGK2, although dispensable for cold-induced thermogenesis that adds an additional layer of complexity to the β3AR signaling network in brown/beige adipose tissue.
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Affiliation(s)
- Chul-Hong Park
- Gene Regulation and Metabolism Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, United States
| | - Jiyoung Moon
- Gene Regulation and Metabolism Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, United States
| | - Minsung Park
- Gene Regulation and Metabolism Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, United States
| | - Helia Cheng
- Gene Regulation and Metabolism Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, United States
| | - Jisu Lee
- Gene Regulation and Metabolism Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, United States
| | - Ji Suk Chang
- Gene Regulation and Metabolism Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, United States
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9
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Al-Shamasi AA, Elkaffash R, Mohamed M, Rayan M, Al-Khater D, Gadeau AP, Ahmed R, Hasan A, Eldassouki H, Yalcin HC, Abdul-Ghani M, Mraiche F. Crosstalk between Sodium-Glucose Cotransporter Inhibitors and Sodium-Hydrogen Exchanger 1 and 3 in Cardiometabolic Diseases. Int J Mol Sci 2021; 22:12677. [PMID: 34884494 PMCID: PMC8657861 DOI: 10.3390/ijms222312677] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/08/2021] [Accepted: 11/12/2021] [Indexed: 12/14/2022] Open
Abstract
Abnormality in glucose homeostasis due to hyperglycemia or insulin resistance is the hallmark of type 2 diabetes mellitus (T2DM). These metabolic abnormalities in T2DM lead to cellular dysfunction and the development of diabetic cardiomyopathy leading to heart failure. New antihyperglycemic agents including glucagon-like peptide-1 receptor agonists and the sodium-glucose cotransporter-2 inhibitors (SGLT2i) have been shown to attenuate endothelial dysfunction at the cellular level. In addition, they improved cardiovascular safety by exhibiting cardioprotective effects. The mechanism by which these drugs exert their cardioprotective effects is unknown, although recent studies have shown that cardiovascular homeostasis occurs through the interplay of the sodium-hydrogen exchangers (NHE), specifically NHE1 and NHE3, with SGLT2i. Another theoretical explanation for the cardioprotective effects of SGLT2i is through natriuresis by the kidney. This theory highlights the possible involvement of renal NHE transporters in the management of heart failure. This review outlines the possible mechanisms responsible for causing diabetic cardiomyopathy and discusses the interaction between NHE and SGLT2i in cardiovascular diseases.
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Affiliation(s)
- Al-Anood Al-Shamasi
- Department of Pharmaceutical Sciences, College of Pharmacy, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.-A.A.-S.); (R.E.); (M.M.); (M.R.); (D.A.-K.)
- Biomedical and Pharmaceutical Research Unit, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
| | - Rozina Elkaffash
- Department of Pharmaceutical Sciences, College of Pharmacy, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.-A.A.-S.); (R.E.); (M.M.); (M.R.); (D.A.-K.)
- Biomedical and Pharmaceutical Research Unit, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
| | - Meram Mohamed
- Department of Pharmaceutical Sciences, College of Pharmacy, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.-A.A.-S.); (R.E.); (M.M.); (M.R.); (D.A.-K.)
- Biomedical and Pharmaceutical Research Unit, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
| | - Menatallah Rayan
- Department of Pharmaceutical Sciences, College of Pharmacy, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.-A.A.-S.); (R.E.); (M.M.); (M.R.); (D.A.-K.)
- Biomedical and Pharmaceutical Research Unit, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
| | - Dhabya Al-Khater
- Department of Pharmaceutical Sciences, College of Pharmacy, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.-A.A.-S.); (R.E.); (M.M.); (M.R.); (D.A.-K.)
- Biomedical and Pharmaceutical Research Unit, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
| | - Alain-Pierre Gadeau
- INSERM, Biology of Cardiovascular Disease, University of Bordeaux, U1034 Pessac, France;
| | - Rashid Ahmed
- Department of Mechanical and Chemical Engineering, College of Engineering, Qatar University, Doha P.O. Box 2713, Qatar; (R.A.); (A.H.)
- Biomedical Research Centre (BRC), Qatar University, Doha P.O. Box 2713, Qatar;
| | - Anwarul Hasan
- Department of Mechanical and Chemical Engineering, College of Engineering, Qatar University, Doha P.O. Box 2713, Qatar; (R.A.); (A.H.)
- Biomedical Research Centre (BRC), Qatar University, Doha P.O. Box 2713, Qatar;
| | - Hussein Eldassouki
- College of Kinesiology, University of Saskatchewan, Saskatoon, SK S7N 5B5, Canada;
| | | | - Muhammad Abdul-Ghani
- Division of Diabetes, University of Texas Health Science Center at San Antonio, Floyd Curl Drive, San Antonio, TX 7703, USA;
| | - Fatima Mraiche
- Department of Pharmaceutical Sciences, College of Pharmacy, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.-A.A.-S.); (R.E.); (M.M.); (M.R.); (D.A.-K.)
- Biomedical and Pharmaceutical Research Unit, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
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New Insights into the Critical Importance of Intratubular Na +/H + Exchanger 3 and Its Potential Therapeutic Implications in Hypertension. Curr Hypertens Rep 2021; 23:34. [PMID: 34110521 DOI: 10.1007/s11906-021-01152-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2021] [Indexed: 01/08/2023]
Abstract
PURPOSE OF REVIEW The sodium (Na+) and hydrogen (H+) exchanger 3 (NHE3), known as solute carrier family 9 member 3 (SLC9A3), mediates active transcellular Na+ and bicarbonate reabsorption in the small intestine of the gut and proximal tubules of the kidney. The purpose of this article is to review and discuss recent findings on the critical roles of intestinal and proximal tubule NHE3 in maintaining basal blood pressure (BP) homeostasis and their potential therapeutic implications in the development of angiotensin II (Ang II)-dependent hypertension. RECENT FINDINGS Recently, our and other laboratories have generated or used novel genetically modified mouse models with whole-body, kidney-specific, or proximal tubule-specific deletion of NHE3 to determine the critical roles and underlying mechanisms of NHE3 in maintaining basal BP homeostasis and the development of Ang II-induced hypertension at the whole-body, kidney, or proximal tubule levels. The new findings demonstrate that NHE3 contributes to about 10 to 15 mmHg to basal blood pressure levels, and that deletion of NHE3 at the whole-kidney or proximal tubule level, or pharmacological inhibition of NHE3 at the kidney level with an orally absorbable NHE3 inhibitor AVE-0657, attenuates ~ 50% of Ang II-induced hypertension in mice. The results support the proof-of-concept hypothesis that NHE3 plays critical roles in physiologically maintaining normal BP and in the development of Ang II-dependent hypertension. Our results also strongly suggest that NHE3 in the proximal tubules of the kidney may be therapeutically targeted to treat poorly controlled hypertension in humans.
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11
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Serum- and glucocorticoid- inducible kinase 2, SGK2, is a novel autophagy regulator and modulates platinum drugs response in cancer cells. Oncogene 2020; 39:6370-6386. [PMID: 32848212 PMCID: PMC7529585 DOI: 10.1038/s41388-020-01433-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 08/07/2020] [Accepted: 08/13/2020] [Indexed: 12/16/2022]
Abstract
For many tumor types chemotherapy still represents the therapy of choice and many standard treatments are based on the use of platinum (PT) drugs. However, de novo or acquired resistance to platinum is frequent and leads to disease progression. In Epithelial Ovarian Cancer (EOC) patients, PT-resistant recurrences are very common and improving the response to treatment still represents an unmet clinical need. To identify new modulators of PT-sensitivity, we performed a loss-of-function screening targeting 680 genes potentially involved in the response of EOC cells to platinum. We found that SGK2 (Serum-and Glucocorticoid-inducible kinase 2) plays a key role in PT-response. We show here that EOC cells relay on the induction of autophagy to escape PT-induced death and that SGK2 inhibition increases PT sensitivity inducing a block in the autophagy cascade due to the impairment of lysosomal acidification. Mechanistically we demonstrate that SGK2 controls autophagy in a kinase-dependent manner by binding and inhibiting the V-ATPase proton pump. Accordingly, SGK2 phosphorylates the subunit V1H (ATP6V1H) of V-ATPase and silencing or chemical inhibition of SGK2, affects the normal autophagic flux and sensitizes EOC cells to platinum. Hence, we identified a new pathway that links autophagy to the survival of cancer cells under platinum treatment in which the druggable kinase SGK2 plays a central role. Our data suggest that blocking autophagy via SGK2 inhibition could represent a novel therapeutic strategy to improve patients' response to platinum.
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12
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Li XC, Zhu D, Chen X, Zheng X, Zhao C, Zhang J, Soleimani M, Rubera I, Tauc M, Zhou X, Zhuo JL. Proximal Tubule-Specific Deletion of the NHE3 (Na +/H + Exchanger 3) in the Kidney Attenuates Ang II (Angiotensin II)-Induced Hypertension in Mice. Hypertension 2019; 74:526-535. [PMID: 31352824 DOI: 10.1161/hypertensionaha.119.13094] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The present study directly tested the hypothesis that the NHE3 (Na+/H+ exchanger 3) in the proximal tubules of the kidney is required for the development of Ang II (angiotensin II)-induced hypertension using PT-Nhe3-/- (proximal tubule-specific NHE3 knockout) mice. Specifically, PT-Nhe3-/- mice were generated using the SGLT2-Cre/Nhe3loxlox approach, whereas Ang II-induced hypertension was studied in 12 groups (n=5-12 per group) of adult male and female wild-type (WT) and PT-Nhe3-/- mice. Under basal conditions, systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure were significantly lower in male and female PT-Nhe3-/- than WT mice (P<0.01). A high pressor, 1.5 mg/kg per day, intraperitoneal or a slow pressor dose of Ang II, 0.5 mg/kg per day, intraperitoneal for 2 weeks significantly increased systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure in male and female WT mice (P<0.01), but the hypertensive response to Ang II was markedly attenuated in male and female PT-Nhe3-/- mice (P<0.01). Ang II impaired the pressure-natriuresis response in WT mice, whereas proximal tubule-specific deletion of NHE3 improved the pressure-natriuresis response in Ang II-infused PT-Nhe3-/- mice (P<0.01). AT1 receptor blocker losartan completely blocked Ang II-induced hypertension in both WT and PT-Nhe3-/- mice (P<0.01). However, inhibition of nitric oxide synthase with L-NG-Nitroarginine methyl ester had no effect on Ang II-induced hypertension in WT or PT-Nhe3-/- mice (not significant). Furthermore, Ang II-induced hypertension was significantly attenuated by an orally absorbable NHE3 inhibitor AVE0657. In conclusion, NHE3 in the proximal tubules of the kidney may be a therapeutical target in hypertension induced by Ang II or with increased NHE3 expression in the proximal tubules.
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Affiliation(s)
- Xiao C Li
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Division of Nephrology, Department of Medicine (X.C.L., J.L.Z.), University of Mississippi Medical Center, Jackson
| | - Dongmin Zhu
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Anesthesiology, Shenzhen Far East Obstetrics and Gynecology Hospital, China (D.Z.)
| | - Xu Chen
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
| | - Xiaowen Zheng
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X. Zheng, C.Z., J.Z.)
| | - Chunling Zhao
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X. Zheng, C.Z., J.Z.)
| | - Jianfeng Zhang
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X. Zheng, C.Z., J.Z.)
| | - Manoocher Soleimani
- Division of Nephrology and Hypertension, Department of Internal Medicine, The University of Cincinnati College of Medicine, OH (M.S.)
| | - Isabelle Rubera
- Laboratoire de Physiomédecine Moléculaire, LP2M, UMR-CNRS 7370, Université Côte d'Azur, Nice Cedex 2, France (I.R., M.T.)
| | - Michel Tauc
- Laboratoire de Physiomédecine Moléculaire, LP2M, UMR-CNRS 7370, Université Côte d'Azur, Nice Cedex 2, France (I.R., M.T.)
| | - Xinchun Zhou
- Department of Pathology (X. Zhou), University of Mississippi Medical Center, Jackson
| | - Jia L Zhuo
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Division of Nephrology, Department of Medicine (X.C.L., J.L.Z.), University of Mississippi Medical Center, Jackson
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13
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McCaig C, Ataliotis P, Shtaya A, Omar AS, Green AR, Kind CN, Pereira AC, Naray-Fejes-Toth A, Fejes-Toth G, Yáñez-Muñoz RJ, Murray JT, Hainsworth AH. Induction of the cell survival kinase Sgk1: A possible novel mechanism for α-phenyl-N-tert-butyl nitrone in experimental stroke. J Cereb Blood Flow Metab 2019; 39:1111-1121. [PMID: 29260627 PMCID: PMC6545623 DOI: 10.1177/0271678x17746980] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 11/03/2017] [Accepted: 11/06/2017] [Indexed: 11/19/2022]
Abstract
Nitrones (e.g. α-phenyl-N-tert-butyl nitrone; PBN) are cerebroprotective in experimental stroke. Free radical trapping is their proposed mechanism. As PBN has low radical trapping potency, we tested Sgk1 induction as another possible mechanism. PBN was injected (100 mg/kg, i.p.) into adult male rats and mice. Sgk1 was quantified in cerebral tissue by microarray, quantitative RT-PCR and western analyses. Sgk1+/+ and Sgk1-/- mice were randomized to receive PBN or saline immediately following transient (60 min) occlusion of the middle cerebral artery. Neurological deficit was measured at 24 h and 48 h and infarct volume at 48 h post-occlusion. Following systemic PBN administration, rapid induction of Sgk1 was detected by microarray (at 4 h) and confirmed by RT-PCR and phosphorylation of the Sgk1-specific substrate NDRG1 (at 6 h). PBN-treated Sgk1+/+ mice had lower neurological deficit ( p < 0.01) and infarct volume ( p < 0.01) than saline-treated Sgk1+/+ mice. PBN-treated Sgk1-/- mice did not differ from saline-treated Sgk1-/- mice. Saline-treated Sgk1-/- and Sgk1+/+ mice did not differ. Brain Sgk3:Sgk1 mRNA ratio was 1.0:10.6 in Sgk1+/+ mice. Sgk3 was not augmented in Sgk1-/- mice. We conclude that acute systemic treatment with PBN induces Sgk1 in brain tissue. Sgk1 may play a part in PBN-dependent actions in acute brain ischemia.
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Affiliation(s)
- Catherine McCaig
- Molecular and Clinical Sciences Research
Institute, St Georges University of London, London, UK
| | - Paris Ataliotis
- Institute for Medical & Biomedical
Education, St George’s University of London, London, UK
| | - Anan Shtaya
- Molecular and Clinical Sciences Research
Institute, St Georges University of London, London, UK
| | - Ayan S Omar
- Molecular and Clinical Sciences Research
Institute, St Georges University of London, London, UK
| | - A Richard Green
- School of Life Sciences, University of
Nottingham, Nottingham, UK
| | - Clive N Kind
- Leicester School of Pharmacy,
De
Montfort University, Leicester, UK
| | - Anthony C Pereira
- Molecular and Clinical Sciences Research
Institute, St Georges University of London, London, UK
- Department of Neurology, St George’s
University Hospitals NHS Foundation Trust, London, UK
| | - Aniko Naray-Fejes-Toth
- Molecular & Systems Biology
Department, Geisel School of Medicine at Dartmouth, Lebanon, NH, USA
| | - Geza Fejes-Toth
- Molecular & Systems Biology
Department, Geisel School of Medicine at Dartmouth, Lebanon, NH, USA
| | - Rafael J Yáñez-Muñoz
- AGCTlab.org, Centre for Biomedical
Sciences, School of Biological Sciences,
Royal
Holloway, University of London, Egham,
Surrey, UK
| | - James T Murray
- School of Biochemistry and Immunology,
Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2,
Ireland
| | - Atticus H Hainsworth
- Molecular and Clinical Sciences Research
Institute, St Georges University of London, London, UK
- Department of Neurology, St George’s
University Hospitals NHS Foundation Trust, London, UK
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14
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Li XC, Zheng X, Chen X, Zhao C, Zhu D, Zhang J, Zhuo JL. Genetic and genomic evidence for an important role of the Na +/H + exchanger 3 in blood pressure regulation and angiotensin II-induced hypertension. Physiol Genomics 2019; 51:97-108. [PMID: 30849009 PMCID: PMC6485378 DOI: 10.1152/physiolgenomics.00122.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The sodium (Na+)/hydrogen (H+) exchanger 3 (NHE3) and sodium-potassium adenosine triphosphatase (Na+/K+-ATPase) are two of the most important Na+ transporters in the proximal tubules of the kidney. On the apical membrane side, NHE3 primarily mediates the entry of Na+ into and the exit of H+ from the proximal tubules, directly and indirectly being responsible for reabsorbing ~50% of filtered Na+ in the proximal tubules of the kidney. On the basolateral membrane side, Na+/K+-ATPase serves as a powerful engine driving Na+ out of, while pumping K+ into the proximal tubules against their concentration gradients. While the roles of NHE3 and Na+/K+-ATPase in proximal tubular Na+ transport under in vitro conditions are well recognized, their respective contributions to the basal blood pressure regulation and angiotensin II (ANG II)-induced hypertension remain poorly understood. Recently, we have been fortunate to be able to use genetically modified mouse models with global, kidney- or proximal tubule-specific deletion of NHE3 to directly determine the cause and effect relationship between NHE3, basal blood pressure homeostasis, and ANG II-induced hypertension at the whole body, kidney and/or proximal tubule levels. The purpose of this article is to review the genetic and genomic evidence for an important role of NHE3 with a focus in the regulation of basal blood pressure and ANG II-induced hypertension, as we learned from studies using global, kidney- or proximal tubule-specific NHE3 knockout mice. We hypothesize that NHE3 in the proximal tubules is necessary for maintaining basal blood pressure homeostasis and the development of ANG II-induced hypertension.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Xiaowen Zheng
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Xu Chen
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Chunling Zhao
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Dongmin Zhu
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Jianfeng Zhang
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
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15
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Watanabe A, Marumo T, Kawarazaki W, Nishimoto M, Ayuzawa N, Ueda K, Hirohama D, Tanaka T, Yagi S, Ota S, Nagae G, Aburatani H, Kumagai H, Fujita T. Aberrant DNA methylation of pregnane X receptor underlies metabolic gene alterations in the diabetic kidney. Am J Physiol Renal Physiol 2018; 314:F551-F560. [DOI: 10.1152/ajprenal.00390.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epigenetic abnormalities have been suggested to mediate metabolic memory observed in diabetic complications. We have shown that epigenetic alterations may induce persistent phenotypic changes in the proximal tubules of the diabetic kidneys. In this study, we show that pregnane X receptor (PXR), a xenobiotic nuclear receptor, is epigenetically altered and upregulated and may have a possible function in the diabetic kidney. PXR has been shown to play a critical role in metabolic changes in obesity and diabetes; however, its distribution and function in the kidney are unknown. In the normal kidney, Pxr was selectively expressed in the proximal tubular cells with demethylation in the promoter DNA. In db/db mice, significant increases in Pxr mRNA, further demethylation of DNA, and stimulatory histone marks in the promoter were observed. Epigenetic changes are likely to play a causative role in PXR induction, since a DNA methyltransferase inhibitor increased PXR mRNA in cultured human proximal tubular cells. Administration of a PXR agonist increased mRNA levels of solute carrier organic anion transporter family member 2B1 ( Slco2b1), a xenobiotic transporter; response gene to complement 32 ( Rgc32), a molecule known to exert fibrotic effects in the kidney; and phosphoenolpyruvate carboxykinase 1 ( Pck1), a gluconeogenic enzyme in the kidney. The expressions of these genes were inhibited by PXR small interfering RNA in cultured proximal tubular cells. Increased mRNA levels of Slco2b1, Rgc32, and Pck1 were also observed in the kidney of db/db mice. These data indicate that PXR is upregulated in the diabetic kidney with aberrant epigenetic modifications and may modulate the course of diabetic kidney disease through the activation of these genes.
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Affiliation(s)
- Atsushi Watanabe
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
- Department of Nephrology and Endocrinology, National Defense Medical College, Saitama, Japan
| | - Takeshi Marumo
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
| | - Wakako Kawarazaki
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
| | | | - Nobuhiro Ayuzawa
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
| | - Kohei Ueda
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
| | - Daigoro Hirohama
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
| | - Toshiya Tanaka
- Laboratory for Systems Biology and Medicine, The University of Tokyo, Tokyo, Japan
| | - Shintaro Yagi
- Laboratory of Cellular Biochemistry, Department of Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo, Tokyo, Japan
| | - Satoshi Ota
- Genome Science Division, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Genta Nagae
- Genome Science Division, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Hiroyuki Aburatani
- Genome Science Division, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Hiroo Kumagai
- Department of Nephrology and Endocrinology, National Defense Medical College, Saitama, Japan
| | - Toshiro Fujita
- Division of Clinical Epigenetics, The University of Tokyo, Tokyo, Japan
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16
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Wang H, Liu C, You G. The activity of organic anion transporter-3: Role of dexamethasone. J Pharmacol Sci 2018; 136:79-85. [PMID: 29422382 DOI: 10.1016/j.jphs.2017.12.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 12/18/2017] [Accepted: 12/28/2017] [Indexed: 12/14/2022] Open
Abstract
Human organic anion transporter-3 (hOAT3) is richly expressed in the kidney, where it plays critical roles in the secretion, from the blood to urine, of clinically important drugs, such as anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. In the current study, we examined the role of dexamethasone in hOAT3 transport activity in the kidney HEK293 cells. Cis-inhibition study showed that dexamethasone exhibited a concentration-dependent inhibition of hOAT3-mediated uptake of estrone sulfate, a prototypical substrate for the transporter, with IC50 value of 49.91 μM. Dixon plot analysis revealed that inhibition by dexamethasone was competitive with a Ki = 47.08 μM. In contrast to the cis-inhibition effect of dexamethasone, prolonged incubation (6 h) of hOAT3-expressing cells with dexamethasone resulted in an upregulation of hOAT3 expression and transport activity, kinetically revealed as an increase in the maximum transport velocity Vmax without meaningful alteration in substrate-binding affinity Km. Such upregulation was abrogated by GSK650394, a specific inhibitor for serum- and glucocorticoid-inducible kinases (sgk). Dexamethasone also enhanced sgk1 phosphorylation. Our study demonstrated that dexamethasone exhibits dual effects on hOAT3: it is a competitive inhibitor for hOAT3-mediated transport, and interestingly, when entering the cells, it stimulates hOAT3 expression and transport activity through sgk1.
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Affiliation(s)
- Haoxun Wang
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Chenchang Liu
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Guofeng You
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.
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17
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Wang H, You G. SGK1/Nedd4-2 signaling pathway regulates the activity of human organic anion transporters 3. Biopharm Drug Dispos 2017; 38:449-457. [PMID: 28608480 DOI: 10.1002/bdd.2085] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 06/06/2017] [Accepted: 06/07/2017] [Indexed: 01/11/2023]
Abstract
Human organic anion transporter 3 (hOAT3) is localized at the basolateral membrane of renal proximal tubule cells and facilitates the renal secretion of numerous clinical drugs, including anti-HIV therapeutics, anti-tumor drugs, antibiotics, antihypertension drugs and anti-inflammatories. The present study explored the role of serum and glucocorticoid-inducible kinase 1 (sgk1) in the regulation of hOAT3. It was shown that over-expression of sgk1 in hOAT3-expressing cells stimulated hOAT3 transport activity by enhancing the transporter expression at the plasma membrane, kinetically reflected as an increased maximal transport velocity Vmax without substantial change in the substrate-binding affinity Km . In contrast, treatment of cells with the sgk-specific inhibitor GSK650394 resulted in a dose-dependent inhibition of hOAT3 transport activity. Evidence was further provided that sgk1 regulation of hOAT3 activity was mediated by ubiquitin ligase Nedd4-2, an enzyme previously shown to have an inhibitory effect on hOAT3. It was shown that sgk1 phosphorylated Nedd4-2, weakened the association between Nedd4-2 and hOAT3, and decreased hOAT3 ubiquitination. Functionally, the sgk1-stimulated hOAT3 transport activity was attenuated in the presence of a ligase-dead mutant of Nedd4-2. In summary, the investigation established for the first time that sgk1 stimulates hOAT3 transport activity by interfering with the inhibitory effect of Nedd4-2 on the transporter.
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Affiliation(s)
- Haoxun Wang
- Rutgers The State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Guofeng You
- Rutgers The State University of New Jersey, Piscataway, NJ, 08854, USA
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18
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Lang F, Guelinckx I, Lemetais G, Melander O. Two Liters a Day Keep the Doctor Away? Considerations on the Pathophysiology of Suboptimal Fluid Intake in the Common Population. Kidney Blood Press Res 2017; 42:483-494. [PMID: 28787716 DOI: 10.1159/000479640] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 04/19/2017] [Indexed: 11/19/2022] Open
Abstract
Suboptimal fluid intake may require enhanced release of antidiuretic hormone (ADH) or vasopressin for the maintenance of adequate hydration. Enhanced copeptin levels (reflecting enhanced vasopressin levels) in 25% of the common population are associated with enhanced risk of metabolic syndrome with abdominal obesity, type 2 diabetes, hypertension, coronary artery disease, heart failure, vascular dementia, cognitive impairment, microalbuminuria, chronic kidney disease, inflammatory bowel disease, cancer, and premature mortality. Vasopressin stimulates the release of glucocorticoids which in turn up-regulate the serum- and glucocorticoid-inducible kinase 1 (SGK1). Moreover, dehydration upregulates the transcription factor NFAT5, which in turn stimulates SGK1 expression. SGK1 is activated by insulin, growth factors and oxidative stress via phosphatidylinositide-3-kinase, 3-phosphoinositide-dependent kinase PDK1 and mTOR. SGK1 is a powerful stimulator of Na+/K+-ATPase, carriers (e.g. the Na+,K+,2Cl- cotransporter NKCC, the NaCl cotransporter NCC, the Na+/H+ exchanger NHE3, and the Na+ coupled glucose transporter SGLT1), and ion channels (e.g. the epithelial Na+ channel ENaC, the Ca2+ release activated Ca2+ channel Orai1 with its stimulator STIM1, and diverse K+ channels). SGK1 further participates in the regulation of the transcription factors nuclear factor kappa-B NFκB, p53, cAMP responsive element binding protein (CREB), activator protein-1, and forkhead transcription factor FKHR-L1 (FOXO3a). Enhanced SGK1 activity fosters the development of hypertension, obesity, diabetes, thrombosis, stroke, inflammation including inflammatory bowel disease and autoimmune disease, cardiac fibrosis, proteinuria, renal failure as well as tumor growth. The present brief review makes the case that suboptimal fluid intake in the common population may enhance vasopressin and glucocorticoid levels thus up-regulating SGK1 expression and favouring the development of SGK1 related pathologies.
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Affiliation(s)
- Florian Lang
- Department of Physiology I, University of Tuebingen, Tuebingen, Germany
| | | | | | - Olle Melander
- Department of Clinical Sciences, Lund University, Malmö, Sweden
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19
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Abstract
Activation of the PI3K pathway is central to a variety of physiological and pathological processes. In these contexts, AKT is classically considered the de facto mediator of PI3K-dependent signaling. However, in recent years, accumulating data point to the existence of additional effectors of PI3K activity, parallel to and independent of AKT, that play critical and unique roles in mediating different developmental, homeostatic, and pathological processes. In this review, I summarize and discuss our current understanding of the function of the serine/threonine kinase SGK1 as a downstream effector of PI3K, and try to separate targets and pathways validated as uniquely SGK1-dependent from those shared with AKT.
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20
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Zamora-González N, Crespo-Sanjuán J, Calvo-Nieves MD, Sánchez D, Ganfornina MD, Martínez G, Aguirre-Gervás B, González-Fajardo JA. Lower Expression of Genes Involved in Protection against Oxidative Stress in Symptomatic Carotid Atherosclerosis. Ann Vasc Surg 2016; 41:271-278. [PMID: 27913124 DOI: 10.1016/j.avsg.2016.08.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2016] [Revised: 07/26/2016] [Accepted: 08/04/2016] [Indexed: 10/20/2022]
Abstract
BACKGROUND Oxidative stress is increased in atherosclerosis, manifested both in blood and tissue (atherosclerotic plaque). We aim at describing the expression of a number of genes related to oxidative stress response in carotid atherosclerotic plaques and their relation to symptomatic state. METHODS We have studied the messenger RNA expression levels for genes related to oxidative stress in a population of 44 patients undergoing carotid endarterectomy, according to the presence (24 patients) or absence (20 patients) of symptoms. Samples were homogenized, RNA was extracted, and gene expression was measured by quantitative reverse transcription polymerase chain reaction arrays. RESULTS Data showed a decrease in expression of oxidative stress protective genes in symptomatic patients and increased expression of pro-oxidant genes. Asymptomatic patients maintain higher levels of expression of protective genes in the tissue. CONCLUSIONS This study establishes a close relationship between symptoms and levels of expression of genes that protect against oxidative stress. We propose the existence of a mechanism that silences these genes, causing a more severe atherosclerotic disease state.
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Affiliation(s)
| | | | | | - Diego Sánchez
- Departamento de Bioquimica y Biologia Molecular y Fisiologia, Instituto de Biologia y Genetica Molecular, Universidad de Valladolid-CSIC, Valladolid, Spain
| | - María Dolores Ganfornina
- Departamento de Bioquimica y Biologia Molecular y Fisiologia, Instituto de Biologia y Genetica Molecular, Universidad de Valladolid-CSIC, Valladolid, Spain
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21
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Xu D, Wang H, You G. Posttranslational Regulation of Organic Anion Transporters by Ubiquitination: Known and Novel. Med Res Rev 2016; 36:964-79. [PMID: 27291023 DOI: 10.1002/med.21397] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 04/27/2016] [Accepted: 04/27/2016] [Indexed: 12/25/2022]
Abstract
Organic anion transporters (OATs) encoded by solute carrier 22 family are localized in the epithelia of multiple organs, where they mediate the absorption, distribution, and excretion of a diverse array of negatively charged environmental toxins and clinically important drugs. Alterations in the expression and function of OATs play important roles in intra- and interindividual variability of the therapeutic efficacy and the toxicity of many drugs. As a result, the activity of OATs must be under tight regulation so as to carry out their normal functions. The regulation of OAT transport activity in response to various stimuli can occur at several levels such as transcription, translation, and posttranslational modification. Posttranslational regulation is of particular interest, because it usually happens within a very short period of time (minutes to hours) when the body has to deal with rapidly changing amounts of substances as a consequence of variable intake of drugs, fluids, or meals as well as metabolic activity. This review article highlights the recent advances from our laboratory in uncovering several posttranslational mechanisms underlying OAT regulation. These advances offer the promise of identifying targets for novel strategies that will maximize therapeutic efficacy in drug development.
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Affiliation(s)
- Da Xu
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey, 08854
| | - Haoxun Wang
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey, 08854
| | - Guofeng You
- Department of Pharmaceutics, Rutgers University, Piscataway, New Jersey, 08854
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22
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Xu D, Huang H, Toh MF, You G. Serum- and glucocorticoid-inducible kinase sgk2 stimulates the transport activity of human organic anion transporters 1 by enhancing the stability of the transporter. INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 7:19-26. [PMID: 27335683 PMCID: PMC4913228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 12/14/2015] [Indexed: 06/06/2023]
Abstract
Human organic anion transporter 1 (hOAT1) belongs to a family of organic anion transporters that play critical roles in the body disposition of clinically important drugs, including anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. hOAT1 is abundantly expressed in the kidney and brain. In the current study, we examined the regulation of hOAT1 by serum- and glucocorticoid-inducible kinase 2 (sgk2) in the kidney COS-7 cells. We showed that sgk2 stimulated hOAT1 transport activity. Such stimulation mainly resulted from an increased cell surface expression of the transporter, kinetically revealed as an increased maximal transport velocity V max without significant change in substrate-binding affinity K m. We further showed that stimulation of hOAT1 activity by sgk2 was achieved by preventing hOAT1 degradation. Our co-immunoprecipitation experiment revealed that the effect of sgk2 on hOAT1 was through a direct interaction between these two proteins. In conclusion, our study demonstrated that sgk2 stimulates hOAT1 transport activity by enhancing the stability of the transporter. This study provides the insights into sgk2 regulation of hOAT1-mediated transport in normal physiology and disease.
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Affiliation(s)
- Da Xu
- Department of Pharmaceutics, Rutgers, The State University of New Jersey Piscataway, NJ 08854, USA
| | - Haozhe Huang
- Department of Pharmaceutics, Rutgers, The State University of New Jersey Piscataway, NJ 08854, USA
| | - May Fern Toh
- Department of Pharmaceutics, Rutgers, The State University of New Jersey Piscataway, NJ 08854, USA
| | - Guofeng You
- Department of Pharmaceutics, Rutgers, The State University of New Jersey Piscataway, NJ 08854, USA
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23
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Jacobs ME, Kathpalia PP, Chen Y, Thomas SV, Noonan EJ, Pao AC. SGK1 regulation by miR-466g in cortical collecting duct cells. Am J Physiol Renal Physiol 2016; 310:F1251-7. [PMID: 26911843 PMCID: PMC4935769 DOI: 10.1152/ajprenal.00024.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 02/22/2016] [Indexed: 11/22/2022] Open
Abstract
Micro-RNAs (miRNAs) are noncoding RNAs that bind target mRNA transcripts and modulate gene expression. In the cortical collecting duct (CCD), aldosterone stimulates the expression of genes that increase activity of the epithelial sodium channel (ENaC); in the early phase of aldosterone induction, one such gene is serum and glucocorticoid regulated kinase 1 (SGK1). We hypothesized that aldosterone regulates the expression of miRNAs in the early phase of induction to control the expression of target genes that stimulate ENaC activity. We treated mpkCCDc14 cells with aldosterone or vehicle for 1 h and used a miRNA microarray to analyze differential miRNA expression. We identified miR-466g as a miRNA that decreased by 57% after 1 h of aldosterone treatment. Moreover, we identified a putative miR-466g binding site in the 3'-untranslated region of SGK1. We constructed an SGK1 3'-untranslated region luciferase reporter and found that cotransfection of miR-466g suppressed luciferase activity in human embryonic kidney-293 cells in a dose-dependent manner. Deletion or introduction of point mutations that disrupt the miR-466g target site attenuated miR-466g-directed suppression of luciferase activity. Finally, we generated stably transduced mpkCCDc14 cell lines overexpressing miR-466g. Cells overexpressing miR-466g demonstrated 12.9-fold lower level of SGK1 mRNA compared with control cells after 6 h of aldosterone induction; moreover, cells overexpressing miR-466g exhibited 25% decrease in amiloride-sensitive current after 6 h of aldosterone induction and complete loss of amiloride-sensitive current after 24 h of aldosterone induction. Our findings implicate miR-466g as a novel early-phase aldosterone responsive miRNA that regulates SGK1 and ENaC in CCD cells.
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Affiliation(s)
- Mollie E Jacobs
- Department of Medicine, Stanford University School of Medicine, Stanford, California; and
| | - Paru P Kathpalia
- Department of Medicine, Stanford University School of Medicine, Stanford, California; and
| | - Yu Chen
- Veterans Affairs Palo Alto Health Care System, Palo Alto, California
| | - Sheela V Thomas
- Department of Medicine, Stanford University School of Medicine, Stanford, California; and
| | - Emily J Noonan
- Department of Medicine, Stanford University School of Medicine, Stanford, California; and Veterans Affairs Palo Alto Health Care System, Palo Alto, California
| | - Alan C Pao
- Department of Medicine, Stanford University School of Medicine, Stanford, California; and Veterans Affairs Palo Alto Health Care System, Palo Alto, California
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24
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Wang H, Xu D, Toh MF, Pao AC, You G. Serum- and glucocorticoid-inducible kinase SGK2 regulates human organic anion transporters 4 via ubiquitin ligase Nedd4-2. Biochem Pharmacol 2016; 102:120-129. [PMID: 26740304 PMCID: PMC5166719 DOI: 10.1016/j.bcp.2015.11.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 11/24/2015] [Indexed: 01/08/2023]
Abstract
Human organic anion transporter 4 (hOAT4) belongs to a family of organic anion transporters that play critical roles in the body disposition of clinically important drugs, including anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. hOAT4 is abundantly expressed in the kidney and placenta. In the current study, we examined the regulation of hOAT4 by serum- and glucocorticoid-inducible kinase 2 (sgk2) in the kidney COS-7 cells. We showed that sgk2 stimulated hOAT4 transport activity. Such stimulation mainly resulted from an increased cell surface expression of the transporter, kinetically revealed as an increased maximal transport velocity Vmax without significant change in substrate-binding affinity Km. We further showed that regulation of hOAT4 activity by sgk2 was mediated by ubiquitin ligase Nedd4-2. Overexpression of Nedd4-2 enhanced hOAT4 ubiquitination, and inhibited hOAT4 transport activity, whereas overexpression of ubiquitin ligase-dead mutant Nedd4-2/C821A or siRNA knockdown of endogenous Nedd4-2 had opposite effects on hOAT4. Our co-immunoprecipitation experiment revealed that sgk2 weakened the association between hOAT4 and Nedd4-2. In conclusion, our study demonstrated for the first time that sgk2 stimulated hOAT4 transport activity by abrogating the inhibitory effect of Nedd4-2 on the transporter.
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Affiliation(s)
- Haoxun Wang
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Da Xu
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - May Fern Toh
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Alan C Pao
- Department of Medicine, Stanford University, Palo Alto, CA 94304, USA
| | - Guofeng You
- Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA.
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25
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Li XC, Shull GE, Miguel-Qin E, Zhuo JL. Role of the Na+/H+ exchanger 3 in angiotensin II-induced hypertension. Physiol Genomics 2015; 47:479-87. [PMID: 26242933 DOI: 10.1152/physiolgenomics.00056.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 07/29/2015] [Indexed: 01/11/2023] Open
Abstract
The renal mechanisms responsible for angiotensin II (ANG II)-induced hypertension remain incompletely understood. The present study tested the hypothesis that the Na(+)/H(+) exchanger 3 (NHE3) is required for ANG II-induced hypertension in mice. Five groups of wild-type (Nhe3(+/+)) and Nhe3(-/-) mice were treated with vehicle or high pressor doses of ANG II (1.5 mg/kg/day ip, via minipump for 2 wk, or 10 pmol/min iv for 30 min). Under basal conditions, Nhe3(-/-) mice had significantly lower systolic blood pressure (SBP) and mean intra-arterial pressure (MAP) (P < 0.01), 24 h urine (P < 0.05), urinary Na(+) (P < 0.01) and urinary K(+) excretion (P < 0.01). In response to ANG II, SBP and MAP markedly increased in Nhe3(+/+) mice in a time-dependent manner, as expected (P < 0.01). However, these acute and chronic pressor responses to ANG II were significantly attenuated in Nhe3(-/-) mice (P < 0.01). Losartan blocked ANG II-induced hypertension in Nhe3(+/+) mice but induced marked mortality in Nhe3(-/-) mice. The attenuated pressor responses to ANG II in Nhe3(-/-) mice were associated with marked compensatory humoral and renal responses to genetic loss of intestinal and renal NHE3. These include elevated basal plasma ANG II and aldosterone and kidney ANG II levels, salt wasting from the intestines, increased renal AQP1, Na(+)/HCO3 (-), and Na(+)/K(+)-ATPase expression, and increased PKCα, mitogen-activated protein kinases ERK1/2, and glycogen synthase kinase 3αβ signaling proteins in the proximal tubules (P < 0.01). We concluded that NHE3 in proximal tubules of the kidney, along with NHE3 in intestines, is required for maintaining basal blood pressure as well as the full development of ANG II-induced hypertension.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Department of Medicine; University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Gary E Shull
- Department of Molecular Genetics, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Elisa Miguel-Qin
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Department of Medicine; University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Department of Medicine; University of Mississippi Medical Center, Jackson, Mississippi; and
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26
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Gleason CE, Frindt G, Cheng CJ, Ng M, Kidwai A, Rashmi P, Lang F, Baum M, Palmer LG, Pearce D. mTORC2 regulates renal tubule sodium uptake by promoting ENaC activity. J Clin Invest 2014; 125:117-28. [PMID: 25415435 DOI: 10.1172/jci73935] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 10/23/2014] [Indexed: 12/17/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is essential for Na+ homeostasis, and dysregulation of this channel underlies many forms of hypertension. Recent studies suggest that mTOR regulates phosphorylation and activation of serum/glucocorticoid regulated kinase 1 (SGK1), which is known to inhibit ENaC internalization and degradation; however, it is not clear whether mTOR contributes to the regulation of renal tubule ion transport. Here, we evaluated the effect of selective mTOR inhibitors on kidney tubule Na+ and K+ transport in WT and Sgk1-/- mice, as well as in isolated collecting tubules. We found that 2 structurally distinct competitive inhibitors (PP242 and AZD8055), both of which prevent all mTOR-dependent phosphorylation, including that of SGK1, caused substantial natriuresis, but not kaliuresis, in WT mice, which indicates that mTOR preferentially influences ENaC function. PP242 also substantially inhibited Na+ currents in isolated perfused cortical collecting tubules. Accordingly, patch clamp studies on cortical tubule apical membranes revealed that mTOR inhibition markedly reduces ENaC activity, but does not alter activity of K+ inwardly rectifying channels (ROMK channels). Together, these results demonstrate that mTOR regulates kidney tubule ion handling and suggest that mTOR regulates Na+ homeostasis through SGK1-dependent modulation of ENaC activity.
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27
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Lang F, Stournaras C, Alesutan I. Regulation of transport across cell membranes by the serum- and glucocorticoid-inducible kinase SGK1. Mol Membr Biol 2014; 31:29-36. [PMID: 24417516 DOI: 10.3109/09687688.2013.874598] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The serum- and glucocorticoid-inducible kinase 1 (SGK1) is genomically upregulated by cell stress including energy depletion and hyperosmotic shock as well as a variety of hormones including glucocorticoids, mineralocorticoids and TGFβ. SGK1 is activated by insulin, growth factors and oxidative stress via phosphatidylinositide-3-kinase, 3-phosphoinositide-dependent kinase PDK1 and mTOR. SGK1 is a powerful stimulator of Na(+)/K(+)-ATPase, carriers (e.g., NCC, NKCC, NHE1, NHE3, SGLT1, several amino acid transporters) and ion channels (e.g., ENaC, SCN5A, TRPV4-6, ORAI1/STIM1, ROMK, KCNE1/KCNQ1, GluR6, CFTR). Mechanisms employed by SGK1 in transport regulation include direct phosphorylation of target transport proteins, phosphorylation and thus activation of other transport regulating kinases, stabilization of membrane proteins by phosphorylation and thus inactivation of the ubiquitin ligase NEDD4-2, as well as stimulation of transport protein expression by upregulation transcription factors (e.g., nuclear factor kappa-B [NFκB]) and by fostering of protein translation. SGK1 sensitivity of pump, carrier and channel activities participate in the regulation of epithelial transport, cardiac and neuronal excitability, degranulation, platelet function, migration, cell proliferation and apoptosis. SGK1-sensitive functions do not require the presence of SGK1 but are markedly upregulated by SGK1. Accordingly, the phenotype of SGK1 knockout mice is mild. The mice are, however, less sensitive to excessive activation of transport by glucocorticoids, mineralocorticoids, insulin and inflammation. Moreover, excessive SGK1 activity contributes to the pathophysiology of hypertension, obesity, diabetes, thrombosis, stroke, inflammation, autoimmune disease, fibrosis and tumor growth.
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Affiliation(s)
- Florian Lang
- Department of Physiology, University of Tübingen , Germany and
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28
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Morrell ED, Kellum JA, Hallows KR, Pastor-Soler NM. Epithelial transport during septic acute kidney injury. Nephrol Dial Transplant 2013; 29:1312-9. [PMID: 24378526 DOI: 10.1093/ndt/gft503] [Citation(s) in RCA: 24] [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
A goal for scientists studying septic acute kidney injury (AKI) should be to formulate a conceptual model of disease that is able to coherently reconcile the molecular and inflammatory consequences of sepsis with impaired epithelial tubular function, diminished glomerular filtration rate (GFR) and ultimately kidney failure. Recent evidence has shed light on how sepsis modulates the tubular regulation of ion, glucose, urea and water transport and acid-base homeostasis in the kidney. The present review summarizes recent discoveries on changes in epithelial transport under septic and endotoxemic conditions as well as the mechanisms that link inflammation with impaired tubular membrane transport. This paper also proposes that the tubular dysfunction that is mediated by inflammation in sepsis ultimately leads to increased sodium and chloride delivery to the distal tubule and macula densa, contributing to tubuloglomerular feedback and impaired GFR. We feel that this conceptual model resolves many of the physiologic and clinical paradoxes that septic AKI presents to practicing researchers and clinicians.
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Affiliation(s)
- Eric D Morrell
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, S976.1 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA
| | - John A Kellum
- The Center for Critical Care Nephrology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA CRISMA (Clinical Research Systems Modeling of Acute Illness) Center, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Department of Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Kenneth R Hallows
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, S976.1 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA The Center for Critical Care Nephrology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Núria M Pastor-Soler
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, S976.1 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA The Center for Critical Care Nephrology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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29
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Abstract
The proximal tubule reabsorbs most of the filtered bicarbonate which is mediated in large part by Na+/H+ exchange (NHE). We have previously demonstrated that there is an isoform switch during postnatal maturation from NHE8 to NHE3 that is concordant with the postnatal increase in serum glucocorticoid levels. To examine if glucocorticoids may be responsible for this isoform switch, we administered dexamethasone daily to mice at 7–10 days of age, a time prior to the normal isoform switch. We show that compared to vehicle-treated controls, dexamethasone caused a premature increase in renal NHE3 and decrease in NHE8 mRNA, total protein, and brush border membrane protein abundance. To examine if there was a direct epithelial action of dexamethasone on NHE8, we studied normal rat kidney (NRK) cells in vitro which express NHE8 on their apical membrane. Dexamethasone decreased NHE8 mRNA, total protein, and apical protein abundance. Dexamethasone also decreased Na+/H+ exchanger activity. These studies provide evidence that glucocorticoids may play a role in the developmental isoform switch from NHE8 to NHE3 and cause a decrease in NHE8 expression and activity.
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Affiliation(s)
- Catherine Joseph
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas Dallas, Texas 75235-9063
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30
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Abstract
The kidney plays a fundamental role in maintaining body salt and fluid balance and blood pressure homeostasis through the actions of its proximal and distal tubular segments of nephrons. However, proximal tubules are well recognized to exert a more prominent role than distal counterparts. Proximal tubules are responsible for reabsorbing approximately 65% of filtered load and most, if not all, of filtered amino acids, glucose, solutes, and low molecular weight proteins. Proximal tubules also play a key role in regulating acid-base balance by reabsorbing approximately 80% of filtered bicarbonate. The purpose of this review article is to provide a comprehensive overview of new insights and perspectives into current understanding of proximal tubules of nephrons, with an emphasis on the ultrastructure, molecular biology, cellular and integrative physiology, and the underlying signaling transduction mechanisms. The review is divided into three closely related sections. The first section focuses on the classification of nephrons and recent perspectives on the potential role of nephron numbers in human health and diseases. The second section reviews recent research on the structural and biochemical basis of proximal tubular function. The final section provides a comprehensive overview of new insights and perspectives in the physiological regulation of proximal tubular transport by vasoactive hormones. In the latter section, attention is particularly paid to new insights and perspectives learnt from recent cloning of transporters, development of transgenic animals with knockout or knockin of a particular gene of interest, and mapping of signaling pathways using microarrays and/or physiological proteomic approaches.
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Affiliation(s)
- Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
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31
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Salyer SA, Parks J, Barati MT, Lederer ED, Clark BJ, Klein JD, Khundmiri SJ. Aldosterone regulates Na(+), K(+) ATPase activity in human renal proximal tubule cells through mineralocorticoid receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2143-52. [PMID: 23684706 DOI: 10.1016/j.bbamcr.2013.05.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 04/15/2013] [Accepted: 05/08/2013] [Indexed: 12/21/2022]
Abstract
The mechanisms by which aldosterone increases Na(+), K(+) ATPase and sodium channel activity in cortical collecting duct and distal nephron have been extensively studied. Recent investigations demonstrate that aldosterone increases Na-H exchanger-3 (NHE-3) activity, bicarbonate transport, and H(+) ATPase in proximal tubules. However, the role of aldosterone in regulation of Na(+), K(+) ATPase in proximal tubules is unknown. We hypothesize that aldosterone increases Na(+), K(+) ATPase activity in proximal tubules through activation of the mineralocorticoid receptor (MR). Immunohistochemistry of kidney sections from human, rat, and mouse kidneys revealed that the MR is expressed in the cytosol of tubules staining positively for Lotus tetragonolobus agglutinin and type IIa sodium-phosphate cotransporter (NpT2a), confirming proximal tubule localization. Adrenalectomy in Sprague-Dawley rats decreased expression of MR, ENaC α, Na(+), K(+) ATPase α1, and NHE-1 in all tubules, while supplementation with aldosterone restored expression of above proteins. In human kidney proximal tubule (HKC11) cells, treatment with aldosterone resulted in translocation of MR to the nucleus and phosphorylation of SGK-1. Treatment with aldosterone also increased Na(+), K(+) ATPase-mediated (86)Rb uptake and expression of Na(+), K(+) ATPase α1 subunits in HKC11 cells. The effects of aldosterone on Na(+), K(+) ATPase-mediated (86)Rb uptake were prevented by spironolactone, a competitive inhibitor of aldosterone for the MR, and partially by Mifepristone, a glucocorticoid receptor (GR) inhibitor. These results suggest that aldosterone regulates Na(+), K(+) ATPase in renal proximal tubule cells through an MR-dependent mechanism.
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Affiliation(s)
- Sarah A Salyer
- Department of Medicine, Kidney Disease Program, University of Louisville, Louisville, KY, USA
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Lang F, Voelkl J. Therapeutic potential of serum and glucocorticoid inducible kinase inhibition. Expert Opin Investig Drugs 2013; 22:701-14. [PMID: 23506284 DOI: 10.1517/13543784.2013.778971] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
INTRODUCTION Expression of serum-and-glucocorticoid-inducible kinase-1 (SGK1) is low in most cells, but dramatically increases under certain pathophysiological conditions, such as glucocorticoid or mineralocorticoid excess, inflammation with TGFβ release, hyperglycemia, cell shrinkage and ischemia. SGK1 is activated by insulin and growth factors via phosphatidylinositide-3-kinase, 3-phosphoinositide-dependent kinase and mammalian target of rapamycin. SGK1 sensitive functions include activation of ion channels (including epithelial Na(+) channel ENaC, voltage gated Na(+) channel SCN5A transient receptor potential channels TRPV4 - 6, Ca(2+) release activated Ca(2+) channel Orai1/STIM1, renal outer medullary K(+) channel ROMK, voltage gated K(+) channels KCNE1/KCNQ1, kainate receptor GluR6, cystic fibrosis transmembrane regulator CFTR), carriers (including Na(+),Cl(-) symport NCC, Na(+),K(+),2Cl(-) symport NKCC, Na(+)/H(+) exchangers NHE1 and NHE3, Na(+), glucose symport SGLT1, several amino acid transporters), and Na(+)/K(+)-ATPase. SGK1 regulates several enzymes (e.g., glycogen synthase kinase-3, ubiquitin-ligase Nedd4-2) and transcription factors (e.g., forkhead transcription factor 3a, β-catenin, nuclear factor kappa B). AREAS COVERED The phenotype of SGK1 knockout mice is mild and SGK1 is apparently dispensible for basic functions. Excessive SGK1 expression and activity, however, contributes to the pathophysiology of several disorders, including hypertension, obesity, diabetes, thrombosis, stroke, fibrosing disease, infertility and tumor growth. A SGK1 gene variant (prevalence ∼ 3 - 5% in Caucasians and ∼ 10% in Africans) is associated with hypertension, stroke, obesity and type 2 diabetes. SGK1 inhibitors have been developed and shown to reduce blood pressure of hyperinsulinemic mice and to counteract tumor cell survival. EXPERT OPINION Targeting SGK1 may be a therapeutic option in several clinical conditions, including metabolic syndrome and tumor growth.
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Affiliation(s)
- Florian Lang
- University of Tuebingen, Department of Physiology, Tuebingen, Germany.
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Abstract
PURPOSE OF REVIEW The serum and glucocorticoid regulated kinase (SGK) family of protein kinases shares similar biochemical and hormonal signaling properties; however, the SGK kinases also exhibit distinct differences in regulating renal sodium (Na(+)) transport. This review will highlight recent advances in our understanding of the specificity of SGK kinase signaling and regulation of renal Na(+) transport. RECENT FINDINGS Differential expression of SGK kinases at the cellular and subcellular levels contributes to signaling specificity. New evidence indicates that SGK1 associates with the apical cell membrane of cortical collecting duct cells to regulate open probability of the epithelial Na(+) channel (ENaC). Scaffold proteins can also recruit SGK1 to multiprotein complexes for regulation of ENaC expression in the apical membrane. Recent SGK1 knockout models have implicated the NaCl co-transporter (NCC) as another target of SGK1 regulation. Less is known about the function of SGK2 or SGK3, but both kinases can regulate Na(+)/H(+) exchanger 3 (NHE3) activity. SUMMARY The SGK kinases assume distinct roles in regulating Na transport in both proximal and distal elements of the kidney tubule. Future examination of the molecular mechanisms by which the SGK kinases regulate specific substrates will inform our understanding of how these kinases contribute to the physiology of renal Na(+) transport.
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Affiliation(s)
- Alan C Pao
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA
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Girardi ACC, Di Sole F. Deciphering the mechanisms of the Na+/H+ exchanger-3 regulation in organ dysfunction. Am J Physiol Cell Physiol 2012; 302:C1569-87. [DOI: 10.1152/ajpcell.00017.2012] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The Na+/H+ exchanger-3 (NHE3) belongs to the mammalian NHE protein family and catalyzes the electro-neutral exchange of extracellular sodium for intracellular proton across cellular membranes. Its transport function is of essential importance for the maintenance of the body's salt and water homeostasis as well as acid-base balance. Indeed, NHE3 activity is finely regulated by a variety of stimuli, both acutely and chronically, and its transport function is fundamental for a multiplicity of severe and world-wide infection-pathological conditions. This review aims to provide a concise overview of NHE3 physiology and discusses the role of NHE3 in clinical conditions of prominent importance, specifically in hypertension, diabetic nephropathy, heart failure, acute kidney injury, and diarrhea. Study of NHE3 function in models of these diseases has contributed to the deciphering of mechanisms that control the delicate ion balance disrupted in these disorders. The majority of the findings indicate that NHE3 transport function is activated before the onset of hypertension and inhibited thereafter; NHE3 transport function is also upregulated in diabetic nephropathy and heart failure, while it is reported to be downregulated in acute kidney injury and in diarrhea. The molecular mechanisms activated during these pathological conditions to regulate NHE3 transport function are examined with the aim of linking NHE3 dysfunction to the analyzed clinical disorders.
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Affiliation(s)
| | - Francesca Di Sole
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and
- Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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Abstract
Small GTPases function as molecular switches in cell signaling, alternating between an inactive, GDP-bound state, and active GTP-bound state. βPix is one of guanine nucleotide exchange factors (GEFs) that catalyze the exchange of bound GDP for ambient GTP. The central goal of this review article is to summarize recent findings on βPix and the role it plays in kidney pathology and physiology. Recent studies shed new light on several key questions concerning the signaling mechanisms mediated by βPix. This manuscript provides a review of the various mechanisms whereby βPix has been shown to function within the kidney through a wide range of actions. Both canonical GEF activity and non-canonical signaling pathways mediated by βPix are discussed. Distribution patterns of βPix in the kidney will be also covered. Much has yet to be discerned, but it is clear that βPix plays a significant role in the kidney.
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Hryciw DH, Kruger WA, Briffa JF, Slattery C, Bolithon A, Lee A, Poronnik P. Sgk-1 is a Positive Regulator of Constitutive Albumin Uptake in Renal Proximal Tubule Cells. Cell Physiol Biochem 2012; 30:1215-26. [DOI: 10.1159/000343313] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2012] [Indexed: 12/12/2022] Open
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He P, Lee SJ, Lin S, Seidler U, Lang F, Fejes-Toth G, Naray-Fejes-Toth A, Yun CC. Serum- and glucocorticoid-induced kinase 3 in recycling endosomes mediates acute activation of Na+/H+ exchanger NHE3 by glucocorticoids. Mol Biol Cell 2011; 22:3812-25. [PMID: 21865597 PMCID: PMC3192861 DOI: 10.1091/mbc.e11-04-0328] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
SGK1 plays an important role in regulation of Na+/H+ exchanger (NHE) 3 in vivo. We show that SGK3 colocalizes with NHE3 in recycling endosomes. These studies identify SGK3 as the effector of the PI3K pathway that activates NHE3 and show that endosomal localization of SGK3 is essential for acute activation of NHE3. Na+/H+ exchanger 3 (NHE3) is the major Na+ transporter in the intestine. Serum- and glucocorticoid-induced kinase (SGK) 1 interacts with NHE regulatory factor 2 (NHERF2) and mediates activation of NHE3 by dexamethasone (Dex) in cultured epithelial cells. In this study, we compared short-term regulation of NHE3 by Dex in SGK1-null and NHERF2-null mice. In comparison to wild-type mice, loss of SGK1 or NHERF2 significantly attenuated regulation of NHE3 by Dex but did not completely obliterate the effect. We show that transfection of SGK2 or SGK3 in PS120 cells resulted in robust activation of NHE3 by Dex. However, unlike SGK1 or SGK2, SGK3 rapidly activated NHE3 within 15 min of Dex treatment in both PS120 and Caco-2bbe cells. Immunofluorescence analysis showed that SGK3 colocalized with NHE3 in recycling endosomes, whereas SGK1 and SGK2 were diffusely distributed. Mutation of Arg-90 of SGK3 disrupted the endosomal localization of SGK3 and delayed NHE3 activation. Activation of SGK3 and NHE3 by Dex was dependent on phosphoinositide 3-kinase (PI3K) and phosphoinositide-dependent kinase 1 (PDK1), and Dex induced translocation of PDK1 to endosomes. Our study identifies SGK3 as a novel endosomal kinase that acutely regulates NHE3 in a PI3K-dependent mechanism.
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Affiliation(s)
- Peijian He
- Division of Digestive Diseases, Department of Medicine, Emory University, Atlanta, GA 30324, USA
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