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Kmochová T, Kidd KO, Orr A, Hnízda A, Hartmannová H, Hodaňová K, Vyleťal P, Naušová K, Brinsa V, Trešlová H, Sovová J, Barešová V, Svojšová K, Vrbacká A, Stránecký V, Robins VC, Taylor A, Martin L, Rivas-Chavez A, Payne R, Bleyer HA, Williams A, Rennke HG, Weins A, Short PJ, Agrawal V, Storsley LJ, Waikar SS, McPhail ED, Dasari S, Leung N, Hewlett T, Yorke J, Gaston D, Geldenhuys L, Samuels M, Levine AP, West M, Hůlková H, Pompach P, Novák P, Weinberg RB, Bedard K, Živná M, Sikora J, Bleyer AJ, Kmoch S. Autosomal dominant ApoA4 mutations present as tubulointerstitial kidney disease with medullary amyloidosis. Kidney Int 2024; 105:799-811. [PMID: 38096951 DOI: 10.1016/j.kint.2023.11.021] [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: 04/13/2023] [Revised: 11/03/2023] [Accepted: 11/10/2023] [Indexed: 01/21/2024]
Abstract
Sporadic cases of apolipoprotein A-IV medullary amyloidosis have been reported. Here we describe five families found to have autosomal dominant medullary amyloidosis due to two different pathogenic APOA4 variants. A large family with autosomal dominant chronic kidney disease (CKD) and bland urinary sediment underwent whole genome sequencing with identification of a chr11:116692578 G>C (hg19) variant encoding the missense mutation p.L66V of the ApoA4 protein. We identified two other distantly related families from our registry with the same variant and two other distantly related families with a chr11:116693454 C>T (hg19) variant encoding the missense mutation p.D33N. Both mutations are unique to affected families, evolutionarily conserved and predicted to expand the amyloidogenic hotspot in the ApoA4 structure. Clinically affected individuals suffered from CKD with a bland urinary sediment and a mean age for kidney failure of 64.5 years. Genotyping identified 48 genetically affected individuals; 44 individuals had an estimated glomerular filtration rate (eGFR) under 60 ml/min/1.73 m2, including all 25 individuals with kidney failure. Significantly, 11 of 14 genetically unaffected individuals had an eGFR over 60 ml/min/1.73 m2. Fifteen genetically affected individuals presented with higher plasma ApoA4 concentrations. Kidney pathologic specimens from four individuals revealed amyloid deposits limited to the medulla, with the mutated ApoA4 identified by mass-spectrometry as the predominant amyloid constituent in all three available biopsies. Thus, ApoA4 mutations can cause autosomal dominant medullary amyloidosis, with marked amyloid deposition limited to the kidney medulla and presenting with autosomal dominant CKD with a bland urinary sediment. Diagnosis relies on a careful family history, APOA4 sequencing and pathologic studies.
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Affiliation(s)
- Tereza Kmochová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Kendrah O Kidd
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Andrew Orr
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Aleš Hnízda
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Hana Hartmannová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Kateřina Hodaňová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Petr Vyleťal
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Karolína Naušová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Vítězslav Brinsa
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Helena Trešlová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Jana Sovová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Veronika Barešová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Klára Svojšová
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Alena Vrbacká
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Viktor Stránecký
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Victoria C Robins
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Abbigail Taylor
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Lauren Martin
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Ana Rivas-Chavez
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Riley Payne
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Heidi A Bleyer
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Adrienne Williams
- Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Helmut G Rennke
- Pathology Department, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Astrid Weins
- Pathology Department, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Varun Agrawal
- Division of Nephrology and Hypertension, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
| | - Leroy J Storsley
- Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Sushrut S Waikar
- Section of Nephrology, Boston University Chobanian and Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Ellen D McPhail
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Surendra Dasari
- Department of Quantitative Health Sciences, Mayo Clinic, Rochester, Minnesota, USA
| | - Nelson Leung
- Division of Nephrology and Hypertension, Division of Hematology, Mayo Clinic, Rochester, Minnesota, USA
| | - Tom Hewlett
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jake Yorke
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Daniel Gaston
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Laurette Geldenhuys
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Mark Samuels
- Department of Medicine Université de Montréal, Montreal, Quebec, Canada; Department of Biochemistry, Université de Montréal, Montreal, Quebec, Canada; Centre de Recherche du CHU Ste-Justine, Montreal, Quebec, Canada
| | - Adam P Levine
- Research Department of Pathology, University College London, London, UK
| | - Michael West
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Helena Hůlková
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Institute of Pathology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Petr Pompach
- Institute of Microbiology of the Czech Academy of Sciences, Vestec, Czech Republic
| | - Petr Novák
- Institute of Microbiology of the Czech Academy of Sciences, Vestec, Czech Republic
| | - Richard B Weinberg
- Section on Gastroenterology, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA; Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Karen Bedard
- Department of Pathology and Laboratory Medicine, Izaak Walton Killam Hospital, Halifax Nova Scotia, Canada
| | - Martina Živná
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Jakub Sikora
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Institute of Pathology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Anthony J Bleyer
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
| | - Stanislav Kmoch
- Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic; Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
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2
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Eiger DS, Hicks C, Gardner J, Pham U, Rajagopal S. Location bias: A "Hidden Variable" in GPCR pharmacology. Bioessays 2023; 45:e2300123. [PMID: 37625014 DOI: 10.1002/bies.202300123] [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: 07/05/2023] [Revised: 08/09/2023] [Accepted: 08/16/2023] [Indexed: 08/27/2023]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors and primarily signal through two main effector proteins: G proteins and β-arrestins. Many agonists of GPCRs promote "biased" responses, in which different cellular signaling pathways are activated with varying efficacies. The mechanisms underlying biased signaling have not been fully elucidated, with many potential "hidden variables" that regulate this behavior. One contributor is "location bias," which refers to the generation of unique signaling cascades from a given GPCR depending upon the cellular location at which the receptor is signaling. Here, we review evidence that GPCRs are expressed at and traffic to various subcellular locations and discuss how location bias can impact the pharmacologic properties and characterization of GPCR agonists. We also evaluate how differences in subcellular environments can modulate GPCR signaling, highlight the physiological significance of subcellular GPCR signaling, and discuss the therapeutic potential of exploiting GPCR location bias.
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Affiliation(s)
- Dylan Scott Eiger
- Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Chloe Hicks
- Trinity College, Duke University, Durham, North Carolina, USA
| | - Julia Gardner
- Trinity College, Duke University, Durham, North Carolina, USA
| | - Uyen Pham
- Department of Biochemistry, Duke University, Durham, North Carolina, USA
| | - Sudarshan Rajagopal
- Department of Biochemistry, Duke University, Durham, North Carolina, USA
- Department of Medicine, Duke University, Durham, North Carolina, USA
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Hulikova A, Park KC, Loonat AA, Gunadasa-Rohling M, Curtis MK, Chung YJ, Wilson A, Carr CA, Trafford AW, Fournier M, Moshnikova A, Andreev OA, Reshetnyak YK, Riley PR, Smart N, Milne TA, Crump NT, Swietach P. Alkaline nucleoplasm facilitates contractile gene expression in the mammalian heart. Basic Res Cardiol 2022; 117:17. [PMID: 35357563 PMCID: PMC8971196 DOI: 10.1007/s00395-022-00924-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 03/04/2022] [Accepted: 03/11/2022] [Indexed: 01/31/2023]
Abstract
Cardiac contractile strength is recognised as being highly pH-sensitive, but less is known about the influence of pH on cardiac gene expression, which may become relevant in response to changes in myocardial metabolism or vascularization during development or disease. We sought evidence for pH-responsive cardiac genes, and a physiological context for this form of transcriptional regulation. pHLIP, a peptide-based reporter of acidity, revealed a non-uniform pH landscape in early-postnatal myocardium, dissipating in later life. pH-responsive differentially expressed genes (pH-DEGs) were identified by transcriptomics of neonatal cardiomyocytes cultured over a range of pH. Enrichment analysis indicated "striated muscle contraction" as a pH-responsive biological process. Label-free proteomics verified fifty-four pH-responsive gene-products, including contractile elements and the adaptor protein CRIP2. Using transcriptional assays, acidity was found to reduce p300/CBP acetylase activity and, its a functional readout, inhibit myocardin, a co-activator of cardiac gene expression. In cultured myocytes, acid-inhibition of p300/CBP reduced H3K27 acetylation, as demonstrated by chromatin immunoprecipitation. H3K27ac levels were more strongly reduced at promoters of acid-downregulated DEGs, implicating an epigenetic mechanism of pH-sensitive gene expression. By tandem cytoplasmic/nuclear pH imaging, the cardiac nucleus was found to exercise a degree of control over its pH through Na+/H+ exchangers at the nuclear envelope. Thus, we describe how extracellular pH signals gain access to the nucleus and regulate the expression of a subset of cardiac genes, notably those coding for contractile proteins and CRIP2. Acting as a proxy of a well-perfused myocardium, alkaline conditions are permissive for expressing genes related to the contractile apparatus.
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Affiliation(s)
- Alzbeta Hulikova
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Kyung Chan Park
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Aminah A Loonat
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Mala Gunadasa-Rohling
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - M Kate Curtis
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Yu Jin Chung
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Abigail Wilson
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Carolyn A Carr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Marjorie Fournier
- Department of Biochemistry, Advanced Proteomics Facility, University of Oxford, Oxford, UK
| | - Anna Moshnikova
- Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI, 02881, USA
| | - Oleg A Andreev
- Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI, 02881, USA
| | - Yana K Reshetnyak
- Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI, 02881, USA
| | - Paul R Riley
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Nicola Smart
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Thomas A Milne
- MRC Molecular Haematology Unit, Radcliffe Department of Medicine, MRC Weatherall Institute of Molecular Medicine, NIHR Oxford Biomedical Research Centre Haematology Theme, University of Oxford, Oxford, UK
| | - Nicholas T Crump
- MRC Molecular Haematology Unit, Radcliffe Department of Medicine, MRC Weatherall Institute of Molecular Medicine, NIHR Oxford Biomedical Research Centre Haematology Theme, University of Oxford, Oxford, UK
| | - Pawel Swietach
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
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4
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Ha JH, Tu HC, Wilkens S, Loh SN. Loss of bound zinc facilitates amyloid fibril formation of leukocyte-cell-derived chemotaxin 2 (LECT2). J Biol Chem 2021; 296:100446. [PMID: 33617884 PMCID: PMC8039541 DOI: 10.1016/j.jbc.2021.100446] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/05/2021] [Accepted: 02/18/2021] [Indexed: 02/06/2023] Open
Abstract
Aggregation of the circulating protein leukocyte-cell-derived chemotaxin 2 (LECT2) causes amyloidosis of LECT2 (ALECT2), one of the most prevalent forms of systemic amyloidosis affecting the kidney and liver. The I40V mutation is thought to be necessary but not sufficient for ALECT2, with a second, as-yet undetermined condition being required for the disease. EM, X-ray diffraction, NMR, and fluorescence experiments demonstrate that LECT2 forms amyloid fibrils in vitro in the absence of other proteins. Removal of LECT2's single bound Zn2+ appears to be obligatory for fibril formation. Zinc-binding affinity is strongly dependent on pH: 9-13 % of LECT2 is calculated to exist in the zinc-free state over the normal pH range of blood, with this fraction rising to 80 % at pH 6.5. The I40V mutation does not alter zinc-binding affinity or kinetics but destabilizes the zinc-free conformation. These results suggest a mechanism in which loss of zinc together with the I40V mutation leads to ALECT2.
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Affiliation(s)
- Jeung-Hoi Ha
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Ho-Chou Tu
- Alnylam Pharmaceuticals, Cambridge, Massachusetts, USA
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Stewart N Loh
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
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Zhou C, Bhinderwala F, Lehman MK, Thomas VC, Chaudhari SS, Yamada KJ, Foster KW, Powers R, Kielian T, Fey PD. Urease is an essential component of the acid response network of Staphylococcus aureus and is required for a persistent murine kidney infection. PLoS Pathog 2019; 15:e1007538. [PMID: 30608981 PMCID: PMC6343930 DOI: 10.1371/journal.ppat.1007538] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 01/23/2019] [Accepted: 12/18/2018] [Indexed: 01/22/2023] Open
Abstract
Staphylococcus aureus causes acute and chronic infections resulting in significant morbidity. Urease, an enzyme that generates NH3 and CO2 from urea, is key to pH homeostasis in bacterial pathogens under acidic stress and nitrogen limitation. However, the function of urease in S. aureus niche colonization and nitrogen metabolism has not been extensively studied. We discovered that urease is essential for pH homeostasis and viability in urea-rich environments under weak acid stress. The regulation of urease transcription by CcpA, Agr, and CodY was identified in this study, implying a complex network that controls urease expression in response to changes in metabolic flux. In addition, it was determined that the endogenous urea derived from arginine is not a significant contributor to the intracellular nitrogen pool in non-acidic conditions. Furthermore, we found that during a murine chronic renal infection, urease facilitates S. aureus persistence by promoting bacterial fitness in the low-pH, urea-rich kidney. Overall, our study establishes that urease in S. aureus is not only a primary component of the acid response network but also an important factor required for persistent murine renal infections. Urease has been reported to be crucial to bacteria in environmental adaptation, virulence, and defense against host immunity. Although the function of urease in S. aureus is not clear, recent evidence suggests that urease is important for acid resistance in various niches. Our study deciphered a function of S. aureus urease both in laboratory conditions and during host colonization. Furthermore, we uncovered the major components of the regulatory system that fine-tunes the expression of urease. Collectively, this study established the dual function of urease which serves as a significant part of the S. aureus acid response while also serving as an enzyme required for persistent kidney infections and potential subsequent staphylococcal metastasis.
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Affiliation(s)
- Chunyi Zhou
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Fatema Bhinderwala
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
- Nebraska Center for Integrated Biomolecular Communication, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - McKenzie K. Lehman
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Vinai C. Thomas
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Sujata S. Chaudhari
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Kelsey J. Yamada
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Kirk W. Foster
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Robert Powers
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
- Nebraska Center for Integrated Biomolecular Communication, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Tammy Kielian
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Paul D. Fey
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- * E-mail:
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Thomsen ARB, Jensen DD, Hicks GA, Bunnett NW. Therapeutic Targeting of Endosomal G-Protein-Coupled Receptors. Trends Pharmacol Sci 2018; 39:879-891. [PMID: 30180973 DOI: 10.1016/j.tips.2018.08.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/07/2018] [Accepted: 08/10/2018] [Indexed: 02/08/2023]
Abstract
G-protein-coupled receptors (GPCRs) are conventionally considered to function at the plasma membrane, where they detect extracellular ligands and activate heterotrimeric G proteins that transmit intracellular signals. Consequently, drug discovery efforts have focused on identification of agonists and antagonists of cell surface GPCRs. However, β-arrestin (ARR)-dependent desensitization and endocytosis rapidly terminate G protein signaling at the plasma membrane. Emerging evidence indicates that GPCRs can continue to signal from endosomes by G-protein- and βARR-dependent processes. By regulating the duration and location of intracellular signaling events, GPCRs in endosomes control critically important processes, including gene transcription and ion channel activity. Thus, GPCRs in endosomes, in addition to at the cell surface, have emerged as important therapeutic targets.
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Affiliation(s)
- Alex R B Thomsen
- Departments of Surgery and Pharmacology, Columbia University College of Physicians and Surgeons, Columbia University in the City of New York, 21 Audubon Avenue, Room 209, New York City, NY 10032, USA
| | - Dane D Jensen
- Departments of Surgery and Pharmacology, Columbia University College of Physicians and Surgeons, Columbia University in the City of New York, 21 Audubon Avenue, Room 209, New York City, NY 10032, USA
| | - Gareth A Hicks
- Gastroenterology Drug Discovery Unit (GI DDU), Takeda Pharmaceuticals U.S.A. Inc., 35 Landsdowne Street, Cambridge, MA 02139, USA
| | - Nigel W Bunnett
- Departments of Surgery and Pharmacology, Columbia University College of Physicians and Surgeons, Columbia University in the City of New York, 21 Audubon Avenue, Room 209, New York City, NY 10032, USA.
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7
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Jung HJ, Kwon TH. Molecular mechanisms regulating aquaporin-2 in kidney collecting duct. Am J Physiol Renal Physiol 2016; 311:F1318-F1328. [PMID: 27760771 DOI: 10.1152/ajprenal.00485.2016] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 10/11/2016] [Accepted: 10/11/2016] [Indexed: 01/04/2023] Open
Abstract
The kidney collecting duct is an important renal tubular segment for regulation of body water homeostasis and urine concentration. Water reabsorption in the collecting duct principal cells is controlled by vasopressin, a peptide hormone that induces the osmotic water transport across the collecting duct epithelia through regulation of water channel proteins aquaporin-2 (AQP2) and aquaporin-3 (AQP3). In particular, vasopressin induces both intracellular translocation of AQP2-bearing vesicles to the apical plasma membrane and transcription of the Aqp2 gene to increase AQP2 protein abundance. The signaling pathways, including AQP2 phosphorylation, RhoA phosphorylation, intracellular calcium mobilization, and actin depolymerization, play a key role in the translocation of AQP2. This review summarizes recent data demonstrating the regulation of AQP2 as the underlying molecular mechanism for the homeostasis of water balance in the body.
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Affiliation(s)
- Hyun Jun Jung
- Epithelial Systems Biology Laboratory, Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland; and
| | - Tae-Hwan Kwon
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu, Korea
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8
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Choi HJ, Jung HJ, Kwon TH. Extracellular pH affects phosphorylation and intracellular trafficking of AQP2 in inner medullary collecting duct cells. Am J Physiol Renal Physiol 2015; 308:F737-48. [DOI: 10.1152/ajprenal.00376.2014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 01/21/2015] [Indexed: 12/29/2022] Open
Abstract
Kidney collecting duct cells are continuously exposed to the changes of extracellular pH (pHe). We aimed to study the effects of altered pHe on desmopressin (dDAVP)-induced phosphorylation (Ser256, Ser261, Ser264, and Ser269) and apical targeting of aquaporin-2 (AQP2) in rat kidney inner medullary collecting duct (IMCD) cells. When freshly prepared IMCD tubule suspensions exposed to HEPES buffer with pH 5.4, 6.4, 7.4, or 8.4 for 1 h were stimulated with dDAVP (10−10 M, 3 min), AQP2 phosphorylation at Ser256, Ser264, and Ser269 was significantly attenuated under acidic conditions. Next, IMCD cells primary cultured in transwell chambers were exposed to a transepithelial pH gradient for 1 h (apical pH 6.4, 7.4, or 8.4 vs. basolateral pH 7.4 and vice versa). Immunocytochemistry and cell surface biotinylation assay revealed that exposure to either apical pH 6.4 or basolateral pH 6.4 for 1 h was associated with decreased dDAVP (10−9 M, 15 min, basolateral)-induced apical targeting of AQP2 and surface expression of AQP2. Fluorescence resonance energy transfer analysis revealed that the dDAVP (10−9 M)-induced increase of PKA activity was significantly attenuated when LLC-PK1 cells were exposed to pHe 6.4 compared with pHe 7.4 and 8.4. In contrast, forskolin (10−7 M)-induced PKA activation and dDAVP (10−9 M)-induced increases of intracellular Ca2+ were not affected. Taken together, dDAVP-induced phosphorylation and apical targeting of AQP2 are attenuated in IMCD cells under acidic pHe, likely via an inhibition of vasopressin V2 receptor-G protein-cAMP-PKA actions.
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Affiliation(s)
- Hyo-Jung Choi
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu, Korea; and
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, Kyungpook National University, Taegu, Korea
| | - Hyun Jun Jung
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu, Korea; and
| | - Tae-Hwan Kwon
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu, Korea; and
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, Kyungpook National University, Taegu, Korea
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Marunaka Y, Yoshimoto K, Aoi W, Hosogi S, Ikegaya H. Low pH of interstitial fluid around hippocampus of the brain in diabetic OLETF rats. MOLECULAR AND CELLULAR THERAPIES 2014; 2:6. [PMID: 26056575 PMCID: PMC4452057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 11/07/2013] [Indexed: 11/21/2023]
Abstract
BACKGROUND We have reported that pH values of ascites and interstitial fluids around the liver in Otsuka Long-Evans Tokushima Fatty (OLETF) rats are significantly lower than normal pH, 7.40, of mammalian body fluids (Biochem Biophys Res Commun 2013, 432:650), and that this lowered pH of interstitial fluid causes the insulin resistance in diabetic patients by decreasing insulin-binding to its receptors (J Physiol Sci 2013, 63:S199). In the preset study, we tried to measure the interstitial fluid pH in diabetic OLETF rats, since the interstitial fluid pH plays key factors in the brain function from a viewpoint of the binding affinity of neurotransmitters to their receptors. FINDINGS We found that the pH value of interstitial fluids around hippocampus, the most important area for memory, in diabetic OLETF rats was lower than that in normal rats by measuring pH with antimony pH electrodes. CONCLUSIONS The lowered pH of interstitial fluid around hippocampus of the brain in diabetic rats observed in the present study suggests that the function of hippocampus of the brain would be diminished due to low affinity of various types of neurotransmitters, playing key roles in the hippocampus function, to their receptors. Therefore, we indicate that maintenance of the interstitial fluid pH at the normal level would be one of the most important key factors for molecular and cellular therapies in various types of diseases including diabetes mellitus.
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Affiliation(s)
- Yoshinori Marunaka
- />Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan
- />Department of Bio-Ionomics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan
- />Japan Institute for Food Education and Health, St. Agnes’ University, Kyoto, 602-8013 Japan
| | - Kanji Yoshimoto
- />Department of Forensic Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan
- />Departments of Food Sciences and Biotechnology, and Health, Faculty of Life Sciences, Hiroshima Institute of Technology, Hiroshima, 731-5193 Japan
| | - Wataru Aoi
- />Laboratory of Health Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, 606-8522 Japan
| | - Shigekuni Hosogi
- />Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan
- />Japan Institute for Food Education and Health, St. Agnes’ University, Kyoto, 602-8013 Japan
| | - Hiroshi Ikegaya
- />Department of Forensic Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan
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Marunaka Y, Yoshimoto K, Aoi W, Hosogi S, Ikegaya H. Low pH of interstitial fluid around hippocampus of the brain in diabetic OLETF rats. MOLECULAR AND CELLULAR THERAPIES 2014; 2:6. [PMID: 26056575 PMCID: PMC4452057 DOI: 10.1186/2052-8426-2-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 11/07/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND We have reported that pH values of ascites and interstitial fluids around the liver in Otsuka Long-Evans Tokushima Fatty (OLETF) rats are significantly lower than normal pH, 7.40, of mammalian body fluids (Biochem Biophys Res Commun 2013, 432:650), and that this lowered pH of interstitial fluid causes the insulin resistance in diabetic patients by decreasing insulin-binding to its receptors (J Physiol Sci 2013, 63:S199). In the preset study, we tried to measure the interstitial fluid pH in diabetic OLETF rats, since the interstitial fluid pH plays key factors in the brain function from a viewpoint of the binding affinity of neurotransmitters to their receptors. FINDINGS We found that the pH value of interstitial fluids around hippocampus, the most important area for memory, in diabetic OLETF rats was lower than that in normal rats by measuring pH with antimony pH electrodes. CONCLUSIONS The lowered pH of interstitial fluid around hippocampus of the brain in diabetic rats observed in the present study suggests that the function of hippocampus of the brain would be diminished due to low affinity of various types of neurotransmitters, playing key roles in the hippocampus function, to their receptors. Therefore, we indicate that maintenance of the interstitial fluid pH at the normal level would be one of the most important key factors for molecular and cellular therapies in various types of diseases including diabetes mellitus.
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Affiliation(s)
- Yoshinori Marunaka
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan ; Department of Bio-Ionomics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan ; Japan Institute for Food Education and Health, St. Agnes' University, Kyoto, 602-8013 Japan
| | - Kanji Yoshimoto
- Department of Forensic Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan ; Departments of Food Sciences and Biotechnology, and Health, Faculty of Life Sciences, Hiroshima Institute of Technology, Hiroshima, 731-5193 Japan
| | - Wataru Aoi
- Laboratory of Health Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, 606-8522 Japan
| | - Shigekuni Hosogi
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan ; Japan Institute for Food Education and Health, St. Agnes' University, Kyoto, 602-8013 Japan
| | - Hiroshi Ikegaya
- Department of Forensic Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566 Japan
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Zahedi K, Barone S, Xu J, Soleimani M. Potentiation of the effect of thiazide derivatives by carbonic anhydrase inhibitors: molecular mechanisms and potential clinical implications. PLoS One 2013; 8:e79327. [PMID: 24260196 PMCID: PMC3832474 DOI: 10.1371/journal.pone.0079327] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/29/2013] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Carbonic anhydrase inhibitors (CAI) are mild diuretics, hence not widely used in fluid overloaded states. They are however the treatment of choice for certain non-kidney conditions. Thiazides, specific inhibitors of Na-Cl cotransport (NCC), are mild agents and the most widely used diuretics in the world for control of mild hypertension. HYPOTHESIS In addition to inhibiting the salt reabsorption in the proximal tubule, CAIs down-regulate pendrin, therefore leaving NCC as the major salt absorbing transporter in the distal nephron, and hence allowing for massive diuresis by the inhibitors of NCC in the setting of increased delivery of salt from the proximal tubule. EXPERIMENTAL PROTOCOLS AND RESULTS Daily treatment of rats with acetazolamide (ACTZ), a known CAI, for 10 days caused mild diuresis whereas daily treatment with hydrochlorothiazide (HCTZ) for 4 days caused hardly any diuresis. However, treatment of rats that were pretreated with ACTZ for 6 days with a combination of ACTZ plus HCTZ for 4 additional days increased the urine output by greater than 2 fold (p<0.001, n = 5) compared to ACTZ-treated animals. Sodium excretion increased by 80% in the ACTZ plus HCTZ group and animals developed significant volume depletion, metabolic alkalosis and pre-renal failure. Molecular studies demonstrated ∼75% reduction in pendrin expression by ACTZ. The increased urine output in ACTZ/HCTZ treated rats was associated with a significant reduction in urine osmolality and reduced membrane localization of AQP-2 (aquaporin2). CONCLUSIONS These results indicate that ACTZ down-regulates pendrin expression and leaves NCC as the major salt absorbing transporter in the distal nephron in the setting of increased delivery of salt from the proximal tubule. Despite being considered mild agents individually, we propose that the combination of ACTZ and HCTZ is a powerful diuretic regimen.
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Affiliation(s)
- Kamyar Zahedi
- Center on Genetics of Transport and the Department of Medicine, University of Cincinnati, Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio
| | - Sharon Barone
- Center on Genetics of Transport and the Department of Medicine, University of Cincinnati, Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio
| | - Jie Xu
- Center on Genetics of Transport and the Department of Medicine, University of Cincinnati, Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio
| | - Manoocher Soleimani
- Center on Genetics of Transport and the Department of Medicine, University of Cincinnati, Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio
- * E-mail:
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Higashijima Y, Sonoda H, Takahashi S, Kondo H, Shigemura K, Ikeda M. Excretion of urinary exosomal AQP2 in rats is regulated by vasopressin and urinary pH. Am J Physiol Renal Physiol 2013; 305:F1412-21. [DOI: 10.1152/ajprenal.00249.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Urinary exosomes are small vesicles secreted into urine from all renal epithelial cell types and known to contain proteins that are involved in renal secretion and reabsorption. Among these proteins, urinary exosomal aquaporin-2 (AQP2) has been suggested to be useful for diagnosis of renal disease. However, the mechanisms underlying the excretion of urinary exosomal AQP2 are largely unknown. In this study, we examined the mechanisms of urinary exosomal AQP2 excretion in vivo, using diuretics including furosemide (FS), an inhibitor of the sodium-potassium-chloride symporter; acetazolamide (ACTZ), an inhibitor of carbonic anhydrase; OPC-31260 (OPC), a vasopressin type 2 receptor antagonist; and NaHCO3, a urinary alkalizing agent. Samples of urine from rats were collected for 2 h just after treatment with each diuretic, and urinary exosomes were isolated by ultracentrifugation. Urinary exosomal AQP2 excretion was dramatically increased by treatment with FS accompanied by urine acidification or with ACTZ accompanied by urine alkalization. Immunohistochemistry showed that apical localization of AQP2 was clearly evident and the plasma vasopressin level was increased after each treatment. Although treatment with OPC alone had no significant effect, coadministration of OPC completely inhibited the FS-induced and partially reduced the ACTZ-induced responses, respectively. Treatment with NaHCO3 increased the excretion of urinary exosomal AQP2 accompanied by urine alkalization. This increased response was partially inhibited by coadministration of OPC. These data suggest that an increased plasma level of vasopressin promoted the excretion of urinary exosomal AQP2 and that urine alkalinization also increased it independently of vasopressin.
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Affiliation(s)
- Yoshiki Higashijima
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, Japan
| | - Hiroko Sonoda
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, Japan
| | - Saki Takahashi
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, Japan
| | - Hiroaki Kondo
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, Japan
| | - Kanako Shigemura
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, Japan
| | - Masahiro Ikeda
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, Japan
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Akakin D, Kiran D, Ozkan N, Erşahin M, Ozdemir-Kumral ZN, Yeğen B, Şener G. Protective effects of melatonin against spinal cord injury induced oxidative damage in rat kidney: A morphological and biochemical study. Acta Histochem 2013; 115:827-34. [PMID: 23725902 DOI: 10.1016/j.acthis.2013.04.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 02/08/2013] [Accepted: 04/04/2013] [Indexed: 12/17/2022]
Abstract
Spinal cord injury (SCI) induced oxidative stress affects multiple organ systems including the kidney. We studied the possible protective effects of melatonin on SCI-induced oxidative damage in renal tissues of rats. Wistar albino rats (n = 24) were exposed to SCI and divided into vehicle- or melatonin-treated SCI groups. Melatonin was administred intraperitoneally at a dose of 10 mg/kg for seven days. Renal tissues were investigated by light and electron microscopy. Furthermore, tissue malondialdehyde (MDA) and glutathione (GSH) levels and myeloperoxidase (MPO) and superoxide dismutase (SOD) activities were also determined. In the vehicle-treated SCI group, the renal histology was disturbed compared to controls, whereas the melatonin-treated SCI group showed significantly reduced degeneration of renal tissue as seen by both light and electron microscopy. MDA levels, MPO and SOD activities were increased and GSH levels were decreased in the vehicle-treated SCI group compared to controls. On the other hand, decreased MDA levels and MPO activities and increased GSH levels were observed in the melatonin-treated SCI group compared to vehicle-treated SCI group. These results showed that experimentally induced SCI caused oxidative stress in the rat kidney, whereas melatonin treatment reduced oxidative stress, suggesting that it may be used as a complementary therapy of renal problems occurring following SCI.
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Feinstein TN, Yui N, Webber MJ, Wehbi VL, Stevenson HP, King JD, Hallows KR, Brown D, Bouley R, Vilardaga JP. Noncanonical control of vasopressin receptor type 2 signaling by retromer and arrestin. J Biol Chem 2013; 288:27849-60. [PMID: 23935101 DOI: 10.1074/jbc.m112.445098] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The vasopressin type 2 receptor (V2R) is a critical G protein-coupled receptor (GPCR) for vertebrate physiology, including the balance of water and sodium ions. It is unclear how its two native hormones, vasopressin (VP) and oxytocin (OT), both stimulate the same cAMP/PKA pathway yet produce divergent antinatriuretic and antidiuretic effects that are either strong (VP) or weak (OT). Here, we present a new mechanism that differentiates the action of VP and OT on V2R signaling. We found that vasopressin, as opposed to OT, continued to generate cAMP and promote PKA activation for prolonged periods after ligand washout and receptor internalization in endosomes. Contrary to the classical model of arrestin-mediated GPCR desensitization, arrestins bind the VP-V2R complex yet extend rather than shorten the generation of cAMP. Signaling is instead turned off by the endosomal retromer complex. We propose that this mechanism explains how VP sustains water and Na(+) transport in renal collecting duct cells. Together with recent work on the parathyroid hormone receptor, these data support the existence of a novel "noncanonical" regulatory pathway for GPCR activation and response termination, via the sequential action of β-arrestin and the retromer complex.
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Affiliation(s)
- Timothy N Feinstein
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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The epidermal Ca(2+) gradient: Measurement using the phasor representation of fluorescent lifetime imaging. Biophys J 2010; 98:911-21. [PMID: 20197045 DOI: 10.1016/j.bpj.2009.10.055] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 09/30/2009] [Accepted: 10/13/2009] [Indexed: 11/21/2022] Open
Abstract
Ionic gradients are found across a variety of tissues and organs. In this report, we apply the phasor representation of fluorescence lifetime imaging data to the quantitative study of ionic concentrations in tissues, overcoming technical problems of tissue thickness, concentration artifacts of ion-sensitive dyes, and calibration across inhomogeneous tissue. We used epidermis as a model system, as Ca(2+) gradients in this organ have been shown previously to control essential biologic processes of differentiation and formation of the epidermal permeability barrier. The approach described here allowed much better localization of Ca(2+) stores than those used in previous studies, and revealed that the bulk of free Ca(2+) measured in the epidermis comes from intracellular Ca(2+) stores such as the Golgi and the endoplasmic reticulum, with extracellular Ca(2+) making a relatively small contribution to the epidermal Ca(2+) gradient. Due to the high spatial resolution of two-photon microscopy, we were able to measure a marked heterogeneity in average calcium concentrations from cell to cell in the basal keratinocytes. This finding, not reported in previous studies, calls into question the long-held hypothesis that keratinocytes increase intracellular Ca(2+), cease proliferation, and differentiate passively in response to changes in extracellular Ca(2+). The experimental results obtained using this approach illustrate the power of the experimental and analytical techniques outlined in this report. Our approach can be used in mechanistic studies to address the formation, maintenance, and function of the epidermal Ca(2+) gradient, and it should be broadly applicable to the study of other tissues with ionic gradients.
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Shunmugavel A, Khan M, Te Chou PC, Dhindsa RK, Martin MM, Copay AG, Subach BR, Schuler TC, Bilgen M, Orak JK, Singh I. Simvastatin protects bladder and renal functions following spinal cord injury in rats. JOURNAL OF INFLAMMATION-LONDON 2010; 7:17. [PMID: 20403180 PMCID: PMC2873501 DOI: 10.1186/1476-9255-7-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 04/19/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Urinary bladder and renal dysfunction are secondary events associated with spinal cord injury (SCI) in humans. These secondary events not only compromise quality of life but also delay overall recovery from SCI pathophysiology. Furthermore, in experimental models the effects of SCI therapy on bladder and renal functions are generally not evaluated. In this study, we tested whether simvastatin improves bladder and renal functions in a rat model of experimental SCI. METHODS SCI was induced by controlled contusion of T9-T10 in adult female rats. Simvastatin (5 mg/Kg body weight) was administered at two hours after SCI and repeated every 24 hours until the end point. Simvastatin-treated SCI animals (simvastatin group) were compared with vehicle-treated SCI animals (vehicle group) in terms of the Basso Beattie Bresnahan score, tissue morphology, cell death, and bladder/renal functions. RESULTS The urinary bladder of vehicle animals showed a 4.3-fold increase in size and a 9-fold increase in wet weight compared to sham animals. Following SCI, the urine to plasma osmolality ratio increased initially but decreased 1 week after SCI. Hematoxylin and eosin staining of bladder tissue showed transitional epithelial hyperplasia, degeneration of lamina propria, and enlargement of tunica adventia in addition to detrusor muscle hypertrophy. Rats treated with simvastatin for 14 days displayed remarkable recovery by showing decreased bladder size and maintenance of a normal urine/plasma osmolality ratio, in addition to improved locomotion. The muscularis layer of the bladder also regained its compact nature in simvastatin animals. Moreover, SCI-induced renal caspase-3 activity was significantly decreased in the simvastatin group indicating the ability of simvastatin to reduce the renal tubular apoptosis. CONCLUSION Post-injury administration of simvastatin ameliorates bladder and renal dysfunction associated with SCI in rats.
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Bouley R, Palomino Z, Tang SS, Nunes P, Kobori H, Lu HA, Shum WW, Sabolic I, Brown D, Ingelfinger JR, Jung FF. Angiotensin II and hypertonicity modulate proximal tubular aquaporin 1 expression. Am J Physiol Renal Physiol 2009; 297:F1575-86. [PMID: 19776169 DOI: 10.1152/ajprenal.90762.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Aquaporin 1 (AQP1) is the major water channel in the renal proximal tubule (PT) and thin descending limb of Henle, but its regulation remains elusive. Here, we investigated the effect of ANG II, a key mediator of body water homeostasis, on AQP1 expression in immortalized rat proximal tubule cells (IRPTC) and rat kidney. Real-time PCR on IRPTC exposed to ANG II for 12 h revealed a biphasic effect AQP1 mRNA increased dose dependently in response to 10(-12) to 10(-8) M ANG II but decreased by 50% with 10(-7) M ANG II. The twofold increase of AQP1 mRNA in the presence of 10(-8) M ANG II was abolished by the AT(1) receptor blocker losartan. Hypertonicity due to either NaCl or mannitol also upregulated AQP1 mRNA by three- and twofold, respectively. Immunocytochemistry and Western blotting revealed a two- to threefold increase in AQP1 protein expression in IRPTC exposed concomitantly to ANG II (10(-8)M) and hypertonic medium (either NaCl or mannitol), indicating that these stimuli were not additive. Three-dimensional reconstruction of confocal images suggested that AQP1 expression was increased by ANG II in both the apical and basolateral poles of IRPTC. In vivo studies showed that short-term ANG II infusion had a diuretic effect, while this effect was attenuated after several days of ANG II infusion. After 10 days, we observed a twofold increase in AQP1 expression in the PT and thin descending limb of Henle of ANG II-infused rats that was abolished when rats were treated with the selective AT(1)-receptor antagonist olmesartan. Thus ANG II increases AQP1 expression in vitro and in vivo via direct interaction with the AT(1) receptor, providing an important regulatory mechanism to link PT water reabsorption to body fluid homeostasis via the renin-angiotensin system.
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Affiliation(s)
- Richard Bouley
- Center for Systems Biology, Program in Membrane Biology, Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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Brown D, Breton S, Ausiello DA, Marshansky V. Sensing, signaling and sorting events in kidney epithelial cell physiology. Traffic 2009; 10:275-84. [PMID: 19170982 PMCID: PMC2896909 DOI: 10.1111/j.1600-0854.2008.00867.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The kidney regulates body fluid, ion and acid/base homeostasis through the interaction of a host of channels, transporters and pumps within specific tubule segments, specific cell types and specific plasma membrane domains. Furthermore, renal epithelial cells have adapted to function in an often unique and challenging environment that includes high medullary osmolality, acidic pHs, variable blood flow and constantly changing apical and basolateral 'bathing' solutions. In this review, we focus on selected protein trafficking events by which kidney epithelial cells regulate body fluid, ion and acid-base homeostasis in response to changes in physiological conditions. We discuss aquaporin 2 and G-protein-coupled receptors in fluid and ion balance, the vacuolar H(+)-adenosine triphosphatase (V-ATPase) and intercalated cells in acid/base regulation and acidification events in the proximal tubule degradation pathway. Finally, in view of its direct role in vesicle trafficking that we outline in this study, we propose that the V-ATPase itself should, under some circumstances, be considered a fourth category of vesicle 'coat' protein (COP), alongside clathrin, caveolin and COPs.
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Affiliation(s)
- Dennis Brown
- Center for Systems Biology, Program in Membrane Biology and Nephrology Division, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
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