1
|
Cheung PW, Boukenna M, Babicz RSE, Mitra S, Kay A, Paunescu TC, Baylor N, Liu CCS, Nair AV, Bouley R, Brown D. Intracellular sites of AQP2 S256 phosphorylation identified using inhibitors of the AQP2 recycling itinerary. Am J Physiol Renal Physiol 2023; 324:F152-F167. [PMID: 36454701 PMCID: PMC9844975 DOI: 10.1152/ajprenal.00123.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 11/23/2022] [Accepted: 11/24/2022] [Indexed: 12/05/2022] Open
Abstract
Vasopressin (VP)-regulated aquaporin-2 (AQP2) trafficking between cytoplasmic vesicles and the plasma membrane of kidney principal cells is essential for water homeostasis. VP affects AQP2 phosphorylation at several serine residues in the COOH-terminus; among them, serine 256 (S256) appears to be a major regulator of AQP2 trafficking. Mutation of this serine to aspartic acid, which mimics phosphorylation, induces constitutive membrane expression of AQP2. However, the intracellular location(s) at which S256 phosphorylation occurs remains elusive. Here, we used strategies to block AQP2 trafficking at different cellular locations in LLC-PK1 cells and monitored VP-stimulated phosphorylation of S256 at these sites by immunofluorescence and Western blot analysis with phospho-specific antibodies. Using methyl-β-cyclodextrin, cold block or bafilomycin, and taxol, we blocked AQP2 at the plasma membrane, in the perinuclear trans-Golgi network, and in scattered cytoplasmic vesicles, respectively. Regardless of its cellular location, VP induced a significant increase in S256 phosphorylation, and this effect was not dependent on a functional microtubule cytoskeleton. To further investigate whether protein kinase A (PKA) was responsible for S256 phosphorylation in these cellular compartments, we created PKA-null cells and blocked AQP2 trafficking using the same procedures. We found that S256 phosphorylation was no longer increased compared with baseline, regardless of AQP2 localization. Taken together, our data indicate that AQP2 S256 phosphorylation can occur at the plasma membrane, in the trans-Golgi network, or in cytoplasmic vesicles and that this event is dependent on the expression of PKA in these cells.NEW & NOTEWORTHY Phosphorylation of aquaporin-2 by PKA at serine 256 (S256) occurs in various subcellular locations during its recycling itinerary, suggesting that the protein complex necessary for AQP2 S256 phosphorylation is present in these different recycling stations. Furthermore, we showed, using PKA-null cells, that PKA activity is required for vasopressin-induced AQP2 phosphorylation. Our data reveal a complex spatial pattern of intracellular AQP2 phosphorylation at S256, shedding new light on the role of phosphorylation in AQP2 membrane accumulation.
Collapse
Affiliation(s)
- Pui W Cheung
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Mey Boukenna
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Richard S E Babicz
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Shimontini Mitra
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Anna Kay
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Theodor C Paunescu
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Noah Baylor
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Chen-Chung Steven Liu
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Anil V Nair
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Richard Bouley
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Dennis Brown
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| |
Collapse
|
2
|
Aquaporin Gating: A New Twist to Unravel Permeation through Water Channels. Int J Mol Sci 2022; 23:ijms232012317. [PMID: 36293170 PMCID: PMC9604103 DOI: 10.3390/ijms232012317] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 09/30/2022] [Accepted: 10/05/2022] [Indexed: 11/17/2022] Open
Abstract
Aquaporins (AQPs) are small transmembrane tetrameric proteins that facilitate water, solute and gas exchange. Their presence has been extensively reported in the biological membranes of almost all living organisms. Although their discovery is much more recent than ion transport systems, different biophysical approaches have contributed to confirm that permeation through each monomer is consistent with closed and open states, introducing the term gating mechanism into the field. The study of AQPs in their native membrane or overexpressed in heterologous systems have experimentally demonstrated that water membrane permeability can be reversibly modified in response to specific modulators. For some regulation mechanisms, such as pH changes, evidence for gating is also supported by high-resolution structures of the water channel in different configurations as well as molecular dynamics simulation. Both experimental and simulation approaches sustain that the rearrangement of conserved residues contributes to occlude the cavity of the channel restricting water permeation. Interestingly, specific charged and conserved residues are present in the environment of the pore and, thus, the tetrameric structure can be subjected to alter the positions of these charges to sustain gating. Thus, is it possible to explore whether the displacement of these charges (gating current) leads to conformational changes? To our knowledge, this question has not yet been addressed at all. In this review, we intend to analyze the suitability of this proposal for the first time.
Collapse
|
3
|
Karaduman T, Özcan Türkmen M, Ozer ES, Ergin B, Saglam B, Erdem Tuncdemir B, Mergen H. Functional analysis of AQP2 mutants found in patients with diabetes insipidus. Biologia (Bratisl) 2021. [DOI: 10.1007/s11756-021-00807-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
4
|
Bissonnette P, Lussier Y, Matar J, Leduc‐Nadeau A, Da Cal S, Arthus M, Unwin RJ, Steinke J, Rangaswamy D, Bichet DG. Further evidence for functional recovery of AQP2 mutations associated with nephrogenic diabetes insipidus. Physiol Rep 2021; 9:e14866. [PMID: 34120413 PMCID: PMC8198467 DOI: 10.14814/phy2.14866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/26/2021] [Accepted: 04/13/2021] [Indexed: 11/24/2022] Open
Abstract
Aquaporin-2 (AQP2) is a homotetrameric water channel responsible for the final water reuptake in the kidney. Disease-causing AQP2 mutations induce nephrogenic diabetes insipidus (NDI), a condition that challenges the bodily water balance by producing large urinary volumes. In this study, we characterize three new AQP2 mutations identified in our lab from NDI patients (A120D, A130V, T179N) along the previously reported A47V variant. Using Xenopus oocytes, we compared the key functional and biochemical features of these mutations against classical recessive (R187C) and dominant (R254Q) forms, and once again found clear functional recovery features (increased protein stability and function) for all mutations under study. This behaviour, attributed to heteromerization to wt-AQP2, challenge the classical model to NDI which often depicts recessive mutations as ill-structured proteins unable to oligomerize. Consequently, we propose a revised model to the cell pathophysiology of AQP2-related NDI which accounts for the functional recovery of recessive AQP2 mutations.
Collapse
Affiliation(s)
- Pierre Bissonnette
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | - Yoann Lussier
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | - Jessica Matar
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | | | - Sandra Da Cal
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | | | - Robert J. Unwin
- Department of Renal MedicineUniversity College LondonLondonUK
| | - Julia Steinke
- Division of Pediatric NephrologyHelen DeVos Children’s Hospital and ClinicsGrand RapidsMIUSA
| | - Dharshan Rangaswamy
- Department of NephrologyKasturba Medical CollegeKasturba HospitalManipal Academy of Higher EducationManipalKarnatakaIndia
| | - Daniel G. Bichet
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
- Centre de RechercheHôpital du Sacré‐Cœur de MontréalMontréalQCCanada
| |
Collapse
|
5
|
AQP2: Mutations Associated with Congenital Nephrogenic Diabetes Insipidus and Regulation by Post-Translational Modifications and Protein-Protein Interactions. Cells 2020; 9:cells9102172. [PMID: 32993088 PMCID: PMC7599609 DOI: 10.3390/cells9102172] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 09/22/2020] [Accepted: 09/25/2020] [Indexed: 02/07/2023] Open
Abstract
, the molecular defects in the AVPR2 and AQP2 mutants, post-translational modifications (i.e., phosphorylation, ubiquitination, and glycosylation) and various protein-protein interactions that regulate phosphorylation, ubiquitination, tetramerization, trafficking, stability, and degradation of AQP2.
Collapse
|
6
|
Abstract
Diabetes insipidus (DI) is a disorder characterized by excretion of large amounts of hypotonic urine. Central DI results from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, whereas nephrogenic DI results from resistance to AVP in the kidneys. Central and nephrogenic DI are usually acquired, but genetic causes must be evaluated, especially if symptoms occur in early childhood. Central or nephrogenic DI must be differentiated from primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Primary polydipsia is most common in psychiatric patients and health enthusiasts but the polydipsia in a small subgroup of patients seems to be due to an abnormally low thirst threshold, a condition termed dipsogenic DI. Distinguishing between the different types of DI can be challenging and is done either by a water deprivation test or by hypertonic saline stimulation together with copeptin (or AVP) measurement. Furthermore, a detailed medical history, physical examination and imaging studies are needed to ensure an accurate DI diagnosis. Treatment of DI or primary polydipsia depends on the underlying aetiology and differs in central DI, nephrogenic DI and primary polydipsia.
Collapse
|
7
|
Abstract
Body fluid homeostasis is essential for normal life. In the maintenance of water balance, the most important factor and regulated process is the excretory function of the kidneys. The kidneys are capable to compensate not only the daily fluctuations of water intake but also the consequences of fluid loss (respiration, perspiration, sweating, hemorrhage). The final volume and osmolality of the excreted urine is set in the collecting duct via hormonal regulation. The hormone of water conservation is the vasopressin (AVP), and a large volume of urine is produced and excreted in the absence of AVP secretion or if AVP is ineffective in the kidneys. The aquaporin-2 water channel (AQP2) is expressed in the principal cells, and it plays an essential role in the reabsorption of water in the collecting ducts via type 2 vasopressin receptor (V2R)-mediated mechanism. If neural or hormonal regulation fails to operate the normal function of AVP-V2R-AQP2 system, it can result in various diseases such as diabetes insipidus (DI) or nephrogenic syndrome of inappropriate diuresis (NSIAD). The DI is characterized by excessive production of hyposmotic urine ("insipidus" means tasteless) due to the inability of the kidneys to concentrate urine. In this chapter, we focus and discuss the pathophysiology of nephrogenic DI (NDI) and the potential therapeutic interventions in the light of the current experimental data.
Collapse
Affiliation(s)
- András Balla
- Faculty of Medicine, Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Hungarian Academy of Sciences, Semmelweis University, Budapest, Hungary
| | - László Hunyady
- Faculty of Medicine, Department of Physiology, Semmelweis University, Budapest, Hungary.
- MTA-SE Laboratory of Molecular Physiology, Hungarian Academy of Sciences, Semmelweis University, Budapest, Hungary.
| |
Collapse
|
8
|
Calvanese L, D'Auria G, Vangone A, Falcigno L, Oliva R. Structural Basis for Mutations of Human Aquaporins Associated to Genetic Diseases. Int J Mol Sci 2018; 19:E1577. [PMID: 29799470 PMCID: PMC6032259 DOI: 10.3390/ijms19061577] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 05/17/2018] [Accepted: 05/23/2018] [Indexed: 02/06/2023] Open
Abstract
Aquaporins (AQPs) are among the best structural-characterized membrane proteins, fulfilling the role of allowing water flux across cellular membranes. Thus far, 34 single amino acid polymorphisms have been reported in HUMSAVAR for human aquaporins as disease-related. They affect AQP2, AQP5 and AQP8, where they are associated with nephrogenic diabetes insipidus, keratoderma and colorectal cancer, respectively. For half of these mutations, although they are mostly experimentally characterized in their dysfunctional phenotypes, a structural characterization at a molecular level is still missing. In this work, we focus on such mutations and discuss what the structural defects are that they appear to cause. To achieve this aim, we built a 3D molecular model for each mutant and explored the effect of the mutation on all of their structural features. Based on these analyses, we could collect the structural defects of all the pathogenic mutations (here or previously analysed) under few main categories, that we found to nicely correlate with the experimental phenotypes reported for several of the analysed mutants. Some of the structural analyses we present here provide a rationale for previously experimentally observed phenotypes. Furthermore, our comprehensive overview can be used as a reference frame for the interpretation, on a structural basis, of defective phenotypes of other aquaporin pathogenic mutants.
Collapse
MESH Headings
- Amino Acid Sequence
- Aquaporin 2/chemistry
- Aquaporin 2/genetics
- Aquaporin 2/metabolism
- Aquaporin 5/chemistry
- Aquaporin 5/genetics
- Aquaporin 5/metabolism
- Aquaporins/chemistry
- Aquaporins/genetics
- Aquaporins/metabolism
- Colorectal Neoplasms/genetics
- Colorectal Neoplasms/metabolism
- Colorectal Neoplasms/pathology
- Databases, Protein
- Diabetes Insipidus, Nephrogenic/genetics
- Diabetes Insipidus, Nephrogenic/metabolism
- Diabetes Insipidus, Nephrogenic/pathology
- Gene Expression
- Genetic Predisposition to Disease
- Genotype
- Humans
- Keratoderma, Palmoplantar/genetics
- Keratoderma, Palmoplantar/metabolism
- Keratoderma, Palmoplantar/pathology
- Models, Molecular
- Mutation
- Phenotype
- Protein Conformation, alpha-Helical
- Protein Conformation, beta-Strand
- Protein Interaction Domains and Motifs
- Protein Multimerization
- Sequence Alignment
- Sequence Homology, Amino Acid
Collapse
Affiliation(s)
- Luisa Calvanese
- CIRPeB, University of Naples Federico II, Napoli I-80134, Italy.
| | - Gabriella D'Auria
- CIRPeB, University of Naples Federico II, Napoli I-80134, Italy.
- Department of Pharmacy, University of Naples Federico II, Napoli I-80134, Italy.
- Institute of Biostructures and Bioimaging, CNR, Napoli I-80134, Italy.
| | - Anna Vangone
- Bijvoet Center for Biomolecular Research, Faculty of Science, Department of Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| | - Lucia Falcigno
- CIRPeB, University of Naples Federico II, Napoli I-80134, Italy.
- Department of Pharmacy, University of Naples Federico II, Napoli I-80134, Italy.
- Institute of Biostructures and Bioimaging, CNR, Napoli I-80134, Italy.
| | - Romina Oliva
- Department of Sciences and Technologies, University Parthenope of Naples, Napoli I-80143, Italy.
| |
Collapse
|
9
|
Abstract
Diabetes insipidus is a disease characterized by polyuria and polydipsia due to inadequate release of arginine vasopressin from the posterior pituitary gland (neurohypophyseal diabetes insipidus) or due to arginine vasopressin insensitivity by the renal distal tubule, leading to a deficiency in tubular water reabsorption (nephrogenic diabetes insipidus). This article reviews the genetics of diabetes insipidus in the context of its diagnosis, clinical presentation, and therapy.
Collapse
Affiliation(s)
- Marie Helene Schernthaner-Reiter
- Clinical Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria; Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 31 Center Drive, Bethesda, MD 20892, USA.
| | - Constantine A Stratakis
- Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 31 Center Drive, Bethesda, MD 20892, USA
| | - Anton Luger
- Clinical Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
| |
Collapse
|
10
|
Functional Recovery of AQP2 Recessive Mutations Through Hetero-Oligomerization with Wild-Type Counterpart. Sci Rep 2016; 6:33298. [PMID: 27641679 PMCID: PMC5027563 DOI: 10.1038/srep33298] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 07/25/2016] [Indexed: 12/15/2022] Open
Abstract
Aquaporin-2 (AQP2) is a homotetrameric water channel responsible for the final water reuptake in the kidney. Mutations in the protein induce nephrogenic diabetes insipidus (NDI), which challenges the water balance by producing large urinary volumes. Although recessive AQP2 mutations are believed to generate non-functional and monomeric proteins, the literature identifies several mild mutations which suggest the existence of mixed wt/mut tetramers likely to carry function in heterozygotes. Using Xenopus oocytes, we tested this hypothesis and found that mild mutants (V24A, D150E) can associate with wt-AQP2 in mixed heteromers, providing clear functional gain in the process (62 ± 17% and 63 ± 17% increases, respectively), conversely to the strong monomeric R187C mutant which fails to associate with wt-AQP2. In kidney cells, both V24A and D150E display restored targeting while R187C remains in intracellular stores. Using a collection of mutations to expand recovery analyses, we demonstrate that inter-unit contacts are central to this recovery process. These results not only present the ground data for the functional recovery of recessive AQP2 mutants through heteromerization, which prompt to revisit the accepted NDI model, but more importantly describe a general recovery process that could impact on all multimeric systems where recessive mutations are found.
Collapse
|
11
|
AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption. Proc Natl Acad Sci U S A 2016; 113:E4328-37. [PMID: 27402760 DOI: 10.1073/pnas.1607745113] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Filtration through the kidney eliminates toxins, manages electrolyte balance, and controls water homeostasis. Reabsorption of water from the luminal fluid of the nephron occurs through aquaporin-2 (AQP2) water pores in principal cells that line the kidney-collecting duct. This vital process is impeded by formation of an "actin barrier" that obstructs the passive transit of AQP2 to the plasma membrane. Bidirectional control of AQP2 trafficking is managed by hormones and signaling enzymes. We have discovered that vasopressin-independent facets of this homeostatic mechanism are under the control of A-Kinase Anchoring Protein 220 (AKAP220; product of the Akap11 gene). CRISPR/Cas9 gene editing and imaging approaches show that loss of AKAP220 disrupts apical actin networks in organoid cultures. Similar defects are evident in tissue sections from AKAP220-KO mice. Biochemical analysis of AKAP220-null kidney extracts detected reduced levels of active RhoA GTPase, a well-known modulator of the actin cytoskeleton. Fluorescent imaging of kidney sections from these genetically modified mice revealed that RhoA and AQP2 accumulate at the apical surface of the collecting duct. Consequently, these animals are unable to appropriately dilute urine in response to overhydration. We propose that membrane-proximal signaling complexes constrained by AKAP220 impact the actin barrier dynamics and AQP2 trafficking to ensure water homeostasis.
Collapse
|
12
|
Evolutionary Influenced Interaction Pattern as Indicator for the Investigation of Natural Variants Causing Nephrogenic Diabetes Insipidus. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2015; 2015:641393. [PMID: 26180540 PMCID: PMC4477446 DOI: 10.1155/2015/641393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 12/03/2014] [Indexed: 11/18/2022]
Abstract
The importance of short membrane sequence motifs has been shown in many works and emphasizes the related sequence motif analysis. Together with specific transmembrane helix-helix interactions, the analysis of interacting sequence parts is helpful for understanding the process during membrane protein folding and in retaining the three-dimensional fold. Here we present a simple high-throughput analysis method for deriving mutational information of interacting sequence parts. Applied on aquaporin water channel proteins, our approach supports the analysis of mutational variants within different interacting subsequences and finally the investigation of natural variants which cause diseases like, for example, nephrogenic diabetes insipidus. In this work we demonstrate a simple method for massive membrane protein data analysis. As shown, the presented in silico analyses provide information about interacting sequence parts which are constrained by protein evolution. We present a simple graphical visualization medium for the representation of evolutionary influenced interaction pattern pairs (EIPPs) adapted to mutagen investigations of aquaporin-2, a protein whose mutants are involved in the rare endocrine disorder known as nephrogenic diabetes insipidus, and membrane proteins in general. Furthermore, we present a new method to derive new evolutionary variations within EIPPs which can be used for further mutagen laboratory investigations.
Collapse
|
13
|
Bockenhauer D, Bichet DG. Pathophysiology, diagnosis and management of nephrogenic diabetes insipidus. Nat Rev Nephrol 2015; 11:576-88. [PMID: 26077742 DOI: 10.1038/nrneph.2015.89] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Healthy kidneys maintain fluid and electrolyte homoeostasis by adjusting urine volume and composition according to physiological needs. The final urine composition is determined in the last tubular segment: the collecting duct. Water permeability in the collecting duct is regulated by arginine vasopressin (AVP). Secretion of AVP from the neurohypophysis is regulated by a complex signalling network that involves osmosensors, barosensors and volume sensors. AVP facilitates aquaporin (AQP)-mediated water reabsorption via activation of the vasopressin V2 receptor (AVPR2) in the collecting duct, thus enabling concentration of urine. In nephrogenic diabetes insipidus (NDI), inability of the kidneys to respond to AVP results in functional AQP deficiency. Consequently, affected patients have constant diuresis, resulting in large volumes of dilute urine. Primary forms of NDI result from mutations in the genes that encode the key proteins AVPR2 and AQP2, whereas secondary forms are associated with biochemical abnormalities, obstructive uropathy or the use of certain medications, particularly lithium. Treatment of the disease is informed by identification of the underlying cause. Here we review the clinical aspects and diagnosis of NDI, the various aetiologies, current treatment options and potential future developments.
Collapse
Affiliation(s)
- Detlef Bockenhauer
- University College London Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - Daniel G Bichet
- Departments of Medicine and Molecular and Integrative Physiology, Université de Montréal Research Center, Hôpital du Sacré-Coeur de Montréal, 5400 Boulevard Gouin Ouest, Montréal, QC H4J 1C5 Canada
| |
Collapse
|
14
|
X-ray structure of human aquaporin 2 and its implications for nephrogenic diabetes insipidus and trafficking. Proc Natl Acad Sci U S A 2014; 111:6305-10. [PMID: 24733887 DOI: 10.1073/pnas.1321406111] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Human aquaporin 2 (AQP2) is a water channel found in the kidney collecting duct, where it plays a key role in concentrating urine. Water reabsorption is regulated by AQP2 trafficking between intracellular storage vesicles and the apical membrane. This process is tightly controlled by the pituitary hormone arginine vasopressin and defective trafficking results in nephrogenic diabetes insipidus (NDI). Here we present the X-ray structure of human AQP2 at 2.75 Å resolution. The C terminus of AQP2 displays multiple conformations with the C-terminal α-helix of one protomer interacting with the cytoplasmic surface of a symmetry-related AQP2 molecule, suggesting potential protein-protein interactions involved in cellular sorting of AQP2. Two Cd(2+)-ion binding sites are observed within the AQP2 tetramer, inducing a rearrangement of loop D, which facilitates this interaction. The locations of several NDI-causing mutations can be observed in the AQP2 structure, primarily situated within transmembrane domains and the majority of which cause misfolding and ER retention. These observations provide a framework for understanding why mutations in AQP2 cause NDI as well as structural insights into AQP2 interactions that may govern its trafficking.
Collapse
|
15
|
Kortenoeven MLA, Fenton RA. Renal aquaporins and water balance disorders. Biochim Biophys Acta Gen Subj 2013; 1840:1533-49. [PMID: 24342488 DOI: 10.1016/j.bbagen.2013.12.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/26/2013] [Accepted: 12/09/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Aquaporins (AQPs) are a family of proteins that can act as water channels. Regulation of AQPs is critical to osmoregulation and the maintenance of body water homeostasis. Eight AQPs are expressed in the kidney of which five have been shown to play a role in body water balance; AQP1, AQP2, AQP3, AQP4 and AQP7. AQP2 in particular is regulated by vasopressin. SCOPE OF REVIEW This review summarizes our current knowledge of the underlying mechanisms of various water balance disorders and their treatment strategies. MAJOR CONCLUSIONS Dysfunctions of AQPs are involved in disorders associated with disturbed water homeostasis. Hyponatremia with increased AQP levels can be caused by diseases with low effective circulating blood volume, such as congestive heart failure, or osmoregulation disorders such as the syndrome of inappropriate secretion of antidiuretic hormone. Treatment consists of fluid restriction, demeclocycline and vasopressin type-2 receptor antagonists. Decreased AQP levels can lead to diabetes insipidus (DI), characterized by polyuria and polydipsia. In central DI, vasopressin production is impaired, while in gestational DI, levels of the vasopressin-degrading enzyme vasopressinase are abnormally increased. Treatment consists of the vasopressin analogue dDAVP. Nephrogenic DI is caused by the inability of the kidney to respond to vasopressin and can be congenital, but is most commonly acquired, usually due to lithium therapy. Treatment consists of sufficient fluid supply, low-solute diet and diuretics. GENERAL SIGNIFICANCE In recent years, our understanding of the underlying mechanisms of water balance disorders has increased enormously, which has opened up several possible new treatment strategies. This article is part of a Special Issue entitled Aquaporins.
Collapse
Affiliation(s)
- Marleen L A Kortenoeven
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark.
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark.
| |
Collapse
|
16
|
Spinocerebellar ataxia-13 Kv3.3 potassium channels: arginine-to-histidine mutations affect both functional and protein expression on the cell surface. Biochem J 2013; 454:259-65. [PMID: 23734863 DOI: 10.1042/bj20130034] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The voltage-gated potassium channel Kv3.3 is the causative gene of SCA13 (spinocerebellar ataxia type 13), an autosomal dominant neurological disorder. The four dominant mutations identified to date cause Kv3.3 channels to be non-functional or have altered gating properties in Xenopus oocytes. In the present paper, we report that SCA13 mutations affect functional as well as protein expression of Kv3.3 channels in a mammalian cell line. The reduced protein level of SCA13 mutants is caused by a shorter protein half-life, and blocking the ubiquitin-proteasome pathway increases the total protein of SCA13 mutants more than wild-type. SCA13 mutated amino acids are highly conserved, and the side chains of these residues play a critical role in the stable expression of Kv3.3 proteins. In addition, we show that mutant Kv3.3 protein levels could be partially rescued by treatment with the chemical chaperone TMAO (trimethylamine N-oxide) and to a lesser extent with co-expression of Kv3.1b. Thus our results suggest that amino acid side chains of SCA13 positions affect the protein half-life and/or function of Kv3.3, and the adverse effect on protein expression cannot be fully rescued.
Collapse
|
17
|
Moeller HB, Rittig S, Fenton RA. Nephrogenic diabetes insipidus: essential insights into the molecular background and potential therapies for treatment. Endocr Rev 2013; 34:278-301. [PMID: 23360744 PMCID: PMC3610677 DOI: 10.1210/er.2012-1044] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The water channel aquaporin-2 (AQP2), expressed in the kidney collecting ducts, plays a pivotal role in maintaining body water balance. The channel is regulated by the peptide hormone arginine vasopressin (AVP), which exerts its effects through the type 2 vasopressin receptor (AVPR2). Disrupted function or regulation of AQP2 or the AVPR2 results in nephrogenic diabetes insipidus (NDI), a common clinical condition of renal origin characterized by polydipsia and polyuria. Over several years, major research efforts have advanced our understanding of NDI at the genetic, cellular, molecular, and biological levels. NDI is commonly characterized as hereditary (congenital) NDI, arising from genetic mutations in the AVPR2 or AQP2; or acquired NDI, due to for exmple medical treatment or electrolyte disturbances. In this article, we provide a comprehensive overview of the genetic, cell biological, and pathophysiological causes of NDI, with emphasis on the congenital forms and the acquired forms arising from lithium and other drug therapies, acute and chronic renal failure, and disturbed levels of calcium and potassium. Additionally, we provide an overview of the exciting new treatment strategies that have been recently proposed for alleviating the symptoms of some forms of the disease and for bypassing G protein-coupled receptor signaling.
Collapse
Affiliation(s)
- Hanne B Moeller
- Department of Biomedicine, Aarhus University, and Department of Pediatrics, Aarhus University Hospital, Wilhelm Meyers Alle 3, Building 1234, Aarhus 8000, Denmark.
| | | | | |
Collapse
|
18
|
Bichet DG, El Tarazi A, Matar J, Lussier Y, Arthus MF, Lonergan M, Bockenhauer D, Bissonnette P. Aquaporin-2: new mutations responsible for autosomal-recessive nephrogenic diabetes insipidus-update and epidemiology. Clin Kidney J 2012; 5:195-202. [PMID: 26069764 PMCID: PMC4400507 DOI: 10.1093/ckj/sfs029] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 02/22/2012] [Indexed: 11/14/2022] Open
Abstract
It is clinically useful to distinguish between two types of hereditary nephrogenic diabetes insipidus (NDI): a ‘pure’ type characterized by loss of water only and a complex type characterized by loss of water and ions. Patients with congenital NDI bearing mutations in the vasopressin 2 receptor gene, AVPR2, or in the aquaporin-2 gene, AQP2, have a pure NDI phenotype with loss of water but normal conservation of sodium, potassium, chloride and calcium. Patients with hereditary hypokalemic salt-losing tubulopathies have a complex phenotype with loss of water and ions. They have polyhydramnios, hypercalciuria and hypo- or isosthenuria and were found to bear KCNJ1 (ROMK) and SLC12A1 (NKCC2) mutations. Patients with polyhydramnios, profound polyuria, hyponatremia, hypochloremia, metabolic alkalosis and sensorineural deafness were found to bear BSND mutations. These clinical phenotypes demonstrate the critical importance of the proteins ROMK, NKCC2 and Barttin to transfer NaCl in the medullary interstitium and thereby to generate, together with urea, a hypertonic milieu. This editorial describes two new developments: (i) the genomic information provided by the sequencing of the AQP2 gene is key to the routine care of these patients, and, as in other genetic diseases, reduces health costs and provides psychological benefits to patients and families and (ii) the expression of AQP2 mutants in Xenopus oocytes and in polarized renal tubular cells recapitulates the clinical phenotypes and reveals a continuum from severe loss of function with urinary osmolalities <150 mOsm/kg H2O to milder defects with urine osmolalities >200 mOsm/kg H2O.
Collapse
Affiliation(s)
- Daniel G Bichet
- Groupe d'Étude des Protéines Membranaires (GÉPROM), Département de Physiologie, Université de Montréal, Montréal, Québec, Canada ; Centre de Recherche, Hôpital du Sacré-Cœur de Montréal, Montréal, Québec, Canada
| | - Abdulah El Tarazi
- Groupe d'Étude des Protéines Membranaires (GÉPROM), Département de Physiologie, Université de Montréal, Montréal, Québec, Canada
| | - Jessica Matar
- Groupe d'Étude des Protéines Membranaires (GÉPROM), Département de Physiologie, Université de Montréal, Montréal, Québec, Canada
| | - Yoann Lussier
- Groupe d'Étude des Protéines Membranaires (GÉPROM), Département de Physiologie, Université de Montréal, Montréal, Québec, Canada
| | | | - Michèle Lonergan
- Centre de Recherche, Hôpital du Sacré-Cœur de Montréal, Montréal, Québec, Canada
| | - Detlef Bockenhauer
- Institute of Child Health, University College London, Great Ormond Street Hospital for Children, NHS Trust, London, UK
| | - Pierre Bissonnette
- Groupe d'Étude des Protéines Membranaires (GÉPROM), Département de Physiologie, Université de Montréal, Montréal, Québec, Canada
| |
Collapse
|
19
|
Abstract
Targeted positioning of the water channel AQP2 (aquaporin-2) strictly regulates body water homoeostasis. Trafficking of AQP2 to the apical membrane is critical for the reabsorption of water in renal collecting ducts. In addition to the cAMP-mediated effect of vasopressin on AQP2 trafficking to the apical membrane, other signalling cascades can also induce this sorting. Recently, AQP2-binding proteins which could regulate this trafficking have been discovered; SPA-1 (signal-induced proliferation-associated gene-1), a GAP (GTPase-activating protein) for Rap1, and the cytoskeletal protein actin. This review summarizes recent advances related to the trafficking mechanisms of AQP2.
Collapse
Affiliation(s)
- Yumi Noda
- Department of Nephrology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
| | | |
Collapse
|
20
|
D184E mutation in aquaporin-4 gene impairs water permeability and links to deafness. Neuroscience 2011; 197:80-8. [PMID: 21952128 DOI: 10.1016/j.neuroscience.2011.09.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 09/09/2011] [Accepted: 09/09/2011] [Indexed: 11/21/2022]
Abstract
Aquaporins (AQPs) play a physiological role in several organs and tissues, and their alteration is associated with disorders of water regulation. The identification of molecular interactions, which are crucial in determining the rate of water flux through the channel, is of pivotal role for the discovery of molecules able to target those interactions and therefore to be used for pathologies ascribable to an altered AQP-dependent water balance. In the present study, a mutational screening of human aquaporin-4 (AQP4) gene was performed on subjects with variable degrees of hearing loss. One heterozygous missense mutation was identified in a Spanish sporadic case, leading to an Asp/Glu amino acid substitution at position 184 (D184E). A BLAST analysis revealed that the amino acid D184 is conserved across species, consistently with a crucial role in the structure/function of AQP4 water channels. The mutation induces a significant reduction in water permeability as measured by the Xenopus laevis oocytes swelling assay and by the use of mammalian cells by total internal reflection microscopy. By Western blot, immunofluorescence and 2D Blue Native/SDS-PAGE we show that the reduction in water permeability is not ascribable to a reduced expression of AQP4 mutant protein or to its incorrect plasma membrane targeting and aggregation into orthogonal arrays of particles. Molecular dynamics simulation provided a molecular explanation of the mechanism whereby the mutation induces a loss of function of the channel. Substituting glutamate for aspartate affects the mobility of the D loop, which acquires a higher propensity to equilibrate in a "closed conformation", thus affecting the rate of water flux. We speculate that this mutation, combined with other genetic defects or concurrently with certain environmental stimuli, could confer a higher susceptibility to deafness.
Collapse
|
21
|
Abstract
Over the past two decades, the genetic and molecular basis of familial forms of diabetes insipidus has been elucidated. Diabetes insipidus is a clinical syndrome characterized by the excretion of abnormally large volumes of diluted urine (polyuria) and increased fluid intake (polydipsia). The most common type of diabetes insipidus is caused by lack of the antidiuretic hormone arginine vasopressin (vasopressin), which is produced in the hypothalamus and secreted by the neurohypophysis. This type of diabetes insipidus is referred to here as neurohypophyseal diabetes insipidus. The syndrome can also result from resistance to the antidiuretic effects of vasopressin on the kidney, either at the level of the vasopressin 2 receptor or the aquaporin 2 water channel (which mediates the re-absorption of water from urine), and is referred to as renal or nephrogenic diabetes insipidus. Differentiation between these two types of diabetes insipidus and primary polydipsia can be difficult owing to the existence of partial as well as complete forms of vasopressin deficiency or resistance. Seven different familial forms of diabetes insipidus are known to exist. The clinical presentation, genetic basis and cellular mechanisms responsible for them vary considerably. This information has led to improved methods of differential diagnosis and could provide the basis of new forms of therapy.
Collapse
Affiliation(s)
- Muriel Babey
- Division of Endocrinology, Metabolism and Molecular Medicine, Feinberg School of Medicine, Northwestern University, Tarry 15, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | | | | |
Collapse
|
22
|
Bouley R, Lu HAJ, Nunes P, Da Silva N, McLaughlin M, Chen Y, Brown D. Calcitonin has a vasopressin-like effect on aquaporin-2 trafficking and urinary concentration. J Am Soc Nephrol 2010; 22:59-72. [PMID: 21071524 DOI: 10.1681/asn.2009121267] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The most common cause of hereditary nephrogenic diabetes insipidus is a nonfunctional vasopressin (VP) receptor type 2 (V2R). Calcitonin, another ligand of G-protein-coupled receptors, has a VP-like effect on electrolytes and water reabsorption, suggesting that it may affect AQP2 trafficking. Here, calcitonin increased intracellular cAMP and stimulated the membrane accumulation of AQP2 in LLC-PK1 cells. Pharmacologic inhibition of protein kinase A (PKA) and deficiency of a critical PKA phosphorylation site on AQP2 both prevented calcitonin-induced membrane accumulation of AQP2. Fluorescence assays showed that calcitonin led to a 70% increase in exocytosis and a 20% decrease in endocytosis of AQP2. Immunostaining of rat kidney slices demonstrated that calcitonin induced a significant redistribution of AQP2 to the apical membrane of principal cells in cortical collecting ducts and connecting segments but not in the inner stripe or inner medulla. Calcitonin-treated VP-deficient Brattleboro rats had a reduced urine flow and two-fold higher urine osmolality during the first 12 hours of treatment compared with control groups. Although this VP-like effect of calcitonin diminished over the following 72 hours, the tachyphylaxis was reversible. Taken together, these data show that calcitonin induces cAMP-dependent AQP2 trafficking in cortical collecting and connecting tubules in parallel with an increase in urine concentration. This suggests that calcitonin has a potential therapeutic use in nephrogenic diabetes insipidus.
Collapse
Affiliation(s)
- Richard Bouley
- Massachusetts General Hospital, Center for Systems Biology, Program in Membrane Biology and Division of Nephrology, Simches Research Center, Room 8202, 185 Cambridge Street, Boston, MA 02114, USA.
| | | | | | | | | | | | | |
Collapse
|
23
|
Xu GY, Wang F, Jiang X, Tao J. Aquaporin 1, a potential therapeutic target for migraine with aura. Mol Pain 2010; 6:68. [PMID: 20969805 PMCID: PMC2974658 DOI: 10.1186/1744-8069-6-68] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Accepted: 10/25/2010] [Indexed: 11/10/2022] Open
Abstract
The pathophysiology of migraine remains largely unknown. However, evidence regarding the molecules participating in the pathophysiology of migraine has been accumulating. Water channel proteins, known as aquaporins (AQPs), notably AQP-1 and AQP-4, appears to be involved in the pathophysiology of several neurological diseases. This review outlines newly emerging evidence indicating that AQP-1 plays an important role in pain signal transduction and migraine and could therefore serve as a potential therapeutic target for these diseases.
Collapse
Affiliation(s)
- Guang-Yin Xu
- Key Laboratory of Pain Research & Therapy, Department of Neurobiology and Institute of Neuroscience, Soochow University, Suzhou, P.R. China
| | | | | | | |
Collapse
|
24
|
Nedvetsky PI, Tamma G, Beulshausen S, Valenti G, Rosenthal W, Klussmann E. Regulation of aquaporin-2 trafficking. Handb Exp Pharmacol 2009:133-157. [PMID: 19096775 DOI: 10.1007/978-3-540-79885-9_6] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Principal cells lining renal collecting ducts control the fine-tuning of body water homeostasis by regulating water reabsorption through the water channels aquaporin-2 (AQP2), aquaporin-3 (AQP3), and aquaporin-4 (AQP4). While the localization of AQP2 is subject to regulation by arginine-vasopressin (AVP), AQP3 and AQP4 are constitutively expressed in the basolateral plasma membrane. AVP adjusts the amount of AQP2 in the plasma membrane by triggering its redistribution from intracellular vesicles into the plasma membrane. This permits water entry into the cells and water exit through AQP3 and AQP4. The translocation of AQP2 is initiated by an increase in cAMP following V2R activation through AVP. The AVP-induced rise in cAMP activates protein kinase A (PKA), which in turn phosphorylates AQP2, and thereby triggers the redistribution of AQP2. Several proteins participating in the control of cAMP-dependent AQP2 trafficking have been identified; for example, A kinase anchoring proteins (AKAPs) tethering PKA to cellular compartments; phosphodiesterases (PDEs) regulating the local cAMP level; cytoskeletal components such as F-actin and microtubules; small GTPases of the Rho family controlling cytoskeletal dynamics; motor proteins transporting AQP2-bearing vesicles to and from the plasma membrane for exocytic insertion and endocytic retrieval; SNAREs inducing membrane fusions, hsc70, a chaperone, important for endocytic retrieval. In addition, cAMP-independent mechanisms of translocation mainly involving the F-actin cytoskeleton have been uncovered. Defects of AQP2 trafficking cause diseases such as nephrogenic diabetes insipidus (NDI), a disorder characterized by a massive loss of hypoosmotic urine.This review summarizes recent data elucidating molecular mechanisms underlying the trafficking of AQP2. In particular, we focus on proteins involved in the regulation of trafficking, and physiological and pathophysiological stimuli determining the cellular localization of AQP2. The identification of proteins and protein-protein interactions may lead to the development of drugs targeting AQP2 trafficking. Such drugs may be suitable for the treatment of diseases associated with dysregulation of body water homeostasis, including NDI or cardiovascular diseases (e.g., chronic heart failure) where the AVP level is elevated, inducing excessive water retention.
Collapse
Affiliation(s)
- Pavel I Nedvetsky
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Campus Berlin-Buch, Berlin, 13125, Germany
| | | | | | | | | | | |
Collapse
|
25
|
Loonen AJM, Knoers NVAM, van Os CH, Deen PMT. Aquaporin 2 mutations in nephrogenic diabetes insipidus. Semin Nephrol 2008; 28:252-65. [PMID: 18519086 DOI: 10.1016/j.semnephrol.2008.03.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Water reabsorption in the renal collecting duct is regulated by the antidiuretic hormone vasopressin (AVP). When the vasopressin V2 receptor, present on the basolateral site of the renal principal cell, becomes activated by AVP, aquaporin-2 (AQP2) water channels will be inserted in the apical membrane, and in this fashion, water can be reabsorbed from the pro-urine into the interstitium. The essential role of the vasopressin V2 receptor and AQP2 in the maintenance of body water homeostasis became clear when it was shown that mutations in their genes cause nephrogenic diabetes insipidus, a disorder in which the kidney is unable to concentrate urine in response to AVP. This review describes the current knowledge on AQP2 mutations in nephrogenic diabetes insipidus.
Collapse
Affiliation(s)
- Anne J M Loonen
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | | | | |
Collapse
|
26
|
Sorani MD, Manley GT, Giacomini KM. Genetic variation in human aquaporins and effects on phenotypes of water homeostasis. Hum Mutat 2008; 29:1108-17. [DOI: 10.1002/humu.20762] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
27
|
Sorani MD, Zador Z, Hurowitz E, Yan D, Giacomini KM, Manley GT. Novel variants in human Aquaporin-4 reduce cellular water permeability. Hum Mol Genet 2008; 17:2379-89. [PMID: 18511455 DOI: 10.1093/hmg/ddn138] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cerebral edema contributes significantly to morbidity and mortality after brain injury and stroke. Aquaporin-4 (AQP4), a water channel expressed in astrocytes, plays a key role in brain water homeostasis. Genetic variants in other aquaporin family members have been associated with disease phenotypes. However, in human AQP4, only one non-synonymous single-nucleotide polymorphism (nsSNP) has been reported, with no characterization of protein function or disease phenotype. We analyzed DNA from an ethnically diverse cohort of 188 individuals to identify novel AQP4 variants. AQP4 variants were constructed by site-directed mutagenesis and expressed in cells. Water permeability assays in the cells were used to measure protein function. We identified 24 variants in AQP4 including four novel nsSNPs (I128T, D184E, I205L and M224T). We did not observe the previously documented M278T in our sample. The nsSNPs found were rare ( approximately 1-2% allele frequency) and heterozygous. Computational analysis predicted reduced function mutations. Protein expression and membrane localization were similar for reference AQP4 and the five AQP4 mutants. Cellular assays confirmed that four variant AQP4 channels reduced normalized water permeability to between 26 and 48% of the reference (P < 0.001), while the M278T mutation increased normalized water permeability (P < 0.001). We identified multiple novel AQP4 SNPs and showed that four nsSNPs reduced water permeability. The previously reported M278T mutation resulted in gain of function. Our experiments provide insight into the function of the AQP4 protein. These nsSNPs may have clinical implications for patients with cerebral edema and related disorders.
Collapse
Affiliation(s)
- Marco D Sorani
- Program in Biological and Medical Informatics, University of California, San Francisco, San Francisco, CA 94110, USA
| | | | | | | | | | | |
Collapse
|
28
|
Sahakitrungruang T, Wacharasindhu S, Sinthuwiwat T, Supornsilchai V, Suphapeetiporn K, Shotelersuk V. Identification of two novel aquaporin-2 mutations in a Thai girl with congenital nephrogenic diabetes insipidus. Endocrine 2008; 33:210-4. [PMID: 18473191 DOI: 10.1007/s12020-008-9074-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 04/30/2008] [Accepted: 05/01/2008] [Indexed: 10/22/2022]
Abstract
OBJECTIVE To describe a Thai girl with congenital nephrogenic diabetes insipidus (NDI) and perform mutation analysis of the AQP2 gene. DESIGN Case report. PATIENT A 6-year old girl with a history of failure to thrive, polydipsia and polyuria was studied. Polyuria and polydipsia were observed within the first few months of life. Despite normal serum osmolality and electrolyte, the result of water deprivation test was compatible with a diagnosis of NDI. METHODS The entire coding regions of the AQP2 gene were assessed by polymerase chain reaction and sequencing analysis. The presence of mutations was also confirmed by restriction enzyme digestion analysis. RESULTS Two heterozygous novel missense mutations were identified. Both were located in exon 1; a guanine-to-thymine substitution at nucleotide position 3 (c.3G-->T) inherited from her mother and a guanine-to-adenine at position 85 (c.85G-->A) inherited from her father, resulting in a methionine to isoleucine at codon 1 (p.M1I) and glycine to serine at codon 29 (p.G29S), respectively. These mutations have never been previously described and were not detected in 100 ethnic-matched unaffected control chromosomes. CONCLUSION We report two novel mutations of the AQP2 gene, p.M1I and p.G29S, associated with autosomal recessive congenital NDI. This study expands the genotypic spectrum of AQP2 mutations and emphasizes an important role of genetic testing for definite diagnosis and genetic counseling.
Collapse
Affiliation(s)
- Taninee Sahakitrungruang
- Division of Pediatric Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
| | | | | | | | | | | |
Collapse
|
29
|
Hayanga AJ, Kohen R, Egeland B, Charles A, Spoor M, Kuzon WM, Napolitano LM. Central Diabetes Insipidus: A Rare Perioperative Cause of Severe Hypernatraemia. Anaesth Intensive Care 2008; 36:235-41. [DOI: 10.1177/0310057x0803600215] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In this case report we describe the management of severe hypernatraemia following inadvertent water restriction. A 21-year-old woman with no reported medical history presented on transfer from an outside hospital with a complex volar upper extremity injury. Management both operatively and postoperatively involved a prolonged period of fasting which limited her access to drinking water. Collateral history revealed that she had previously drunk copious amounts of water during the course of any given day and this had served to alleviate the dramatic symptoms of hypernatraemia that were rapidly manifest when her normal intake was curtailed. We outline the fluid management, administration of desmopressin and her subsequent recovery. A literature review of the management of central diabetes insipidus is also covered.
Collapse
Affiliation(s)
- A. J. Hayanga
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - R. Kohen
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - B. Egeland
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - A. Charles
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - M. Spoor
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - W. M. Kuzon
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - L. M. Napolitano
- Divisions of Acute Care Surgery and Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| |
Collapse
|
30
|
Roth J, Yam GHF, Fan J, Hirano K, Gaplovska-Kysela K, Le Fourn V, Guhl B, Santimaria R, Torossi T, Ziak M, Zuber C. Protein quality control: the who's who, the where's and therapeutic escapes. Histochem Cell Biol 2008; 129:163-77. [PMID: 18075753 PMCID: PMC2228381 DOI: 10.1007/s00418-007-0366-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2007] [Indexed: 01/01/2023]
Abstract
In cells the quality of newly synthesized proteins is monitored in regard to proper folding and correct assembly in the early secretory pathway, the cytosol and the nucleoplasm. Proteins recognized as non-native in the ER will be removed and degraded by a process termed ERAD. ERAD of aberrant proteins is accompanied by various changes of cellular organelles and results in protein folding diseases. This review focuses on how the immunocytochemical labeling and electron microscopic analyses have helped to disclose the in situ subcellular distribution pattern of some of the key machinery proteins of the cellular protein quality control, the organelle changes due to the presence of misfolded proteins, and the efficiency of synthetic chaperones to rescue disease-causing trafficking defects of aberrant proteins.
Collapse
Affiliation(s)
- Jürgen Roth
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Gary Hin-Fai Yam
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, University Eye Centre, Mongkok, Kowloon Hong Kong
| | - Jingyu Fan
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- Department of Biophysics, Peking University Health Science Center, 100083 Beijing, P. R. China
| | - Kiyoko Hirano
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- The Noguchi Institute, 1-8-1 Kaga, Itabashi, Tokyo 173-0003 Japan
| | - Katarina Gaplovska-Kysela
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Valerie Le Fourn
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Bruno Guhl
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Roger Santimaria
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Tania Torossi
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Martin Ziak
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Christian Zuber
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| |
Collapse
|
31
|
Jeyaseelan K, Sepramaniam S, Armugam A, Wintour EM. Aquaporins: a promising target for drug development. Expert Opin Ther Targets 2007; 10:889-909. [PMID: 17105375 DOI: 10.1517/14728222.10.6.889] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Aquaporins (AQPs) are a family of small hydrophobic, integral membrane proteins that are expressed in all living organisms and play critical roles in controlling the water flow into and out of cells. So far, 13 different AQPs have been identified in mammals (AQP 0-12). AQPs have recently been implicated in various diseases such as cancer, cataract, brain oedema, gallstone disease and nephrogenic diabetes insipidus, as well as in the development of obesity and polycystic kidney disease. Interfering with the expression of AQPs will undoubtedly have therapeutic applications. Hence, in this review, the authors look at each AQP and its association with various pathological conditions in humans and demonstrate that they form potential targets for the treatment of such diseases.
Collapse
Affiliation(s)
- Kandiah Jeyaseelan
- Yong Loo Lin School of Medicine, National University of Singapore, Department of Biochemistry, 8 Medical Drive, 117597, Singapore.
| | | | | | | |
Collapse
|
32
|
Watson KJ, Kim I, Baquero AF, Burks CA, Liu L, Gilbertson TA. Expression of aquaporin water channels in rat taste buds. Chem Senses 2007; 32:411-21. [PMID: 17339611 DOI: 10.1093/chemse/bjm006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In order to gain insight into the molecular mechanisms that allow taste cells to respond to changes in their osmotic environment, we have used primarily immunocytochemical and molecular approaches to look for evidence of the presence of aquaporin-like water channels in taste cells. Labeling of isolated taste buds from the fungiform, foliate, and vallate papillae in rat tongue with antibodies against several of the aquaporins (AQPs) revealed the presence of AQP1, AQP2, and AQP5 in taste cells from these areas. AQP3 antibodies failed to label isolated taste buds from any of the papillae. There was an apparent difference in the regional localization of AQP labeling within the taste bud. Antibodies against AQP1 and AQP2 labeled predominantly the basolateral membrane, whereas the AQP5 label was clearly evident on both the apical and basolateral membranes of cells within the taste bud. Double labeling revealed that AQP1 and AQP2 labeled many, but not all, of the same taste cells. Similar double-labeling experiments with anti-AQP2 and anti-AQP5 clearly showed that AQP5 was expressed on or near the apical membranes whereas AQP2 was absent from this area. The presence of these 3 types of AQPs in taste buds but not in non-taste bud-containing epithelia was confirmed using reverse transcription-polymerase chain reaction. Experiments using patch clamp recording showed that the AQP inhibitor, tetraethylammonium, significantly reduced hypoosmotic-induced currents in rat taste cells. We hypothesize that the AQPs may play roles both in the water movement underlying compensatory mechanisms for changes in extracellular osmolarity and, in the case of AQP5 in particular, in the gustatory response to water.
Collapse
Affiliation(s)
- Kristina J Watson
- Department of Biology and The Center for Advanced Nutrition, Utah State University, Logan, UT 84322-5305, USA.
| | | | | | | | | | | |
Collapse
|
33
|
Iolascon A, Aglio V, Tamma G, D'Apolito M, Addabbo F, Procino G, Simonetti MC, Montini G, Gesualdo L, Debler EW, Svelto M, Valenti G. Characterization of two novel missense mutations in the AQP2 gene causing nephrogenic diabetes insipidus. Nephron Clin Pract 2006; 105:p33-41. [PMID: 17192724 DOI: 10.1159/000098136] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Accepted: 10/13/2006] [Indexed: 01/10/2023] Open
Abstract
Here, we report the aquaporin 2 (AQP2) mutational analysis of a patient with nephrogenic diabetes insipidus heterozygote due to two novel missense mutations. Direct sequencing of DNA in the male patient revealed that he was compound heterozygote for two mutations in the AQP2 gene: a thymine-to-adenine transversion at position 450 (c.450T>A) in exon 2 and a guanine-to-thymine at nucleotide position 643 (c.643G>T) in exon 4. The double heterozygous 450T>A and 643G>T transversion causes the amino acid substitution D150E and G215C. Direct sequencing of exons 2 and 4 of the AQP2 gene from each of the parents revealed that the c.450T>A mutation was inherited from the father while the c.643G>T mutation was inherited from the mother. Analysis of AQP2 excretion demonstrated that no AQP2 was detectable in the urine of the proband, whereas normal AQP2 levels were measured in both parents. When expressed in renal cells, both proteins were retarded in the endoplasmic reticulum and no redistribution was observed after forskolin stimulation. Of note, homology modeling revealed that the two mutations involve two highly conserved residues providing important clues about the role of the wt residues in AQP2 stability and function.
Collapse
Affiliation(s)
- Achille Iolascon
- Department of Biochemistry and Biomedical Technologies, University Federico II--CEINGE, Naples, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Carroll P, Al-Mojalli H, Al-Abbad A, Al-Hassoun I, Al-Hamed M, Al-Amr R, Butt AI, Meyer BF. Novel mutations underlying nephrogenic diabetes insipidus in Arab families. Genet Med 2006; 8:443-7. [PMID: 16845277 DOI: 10.1097/01.gim.0000223554.46981.7a] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Nephrogenic Diabetes Insipidus (NDI) is genetically heterogeneous and may be inherited in an X-linked or autosomal recessive manner. We aimed to investigate the molecular basis of NDI among Arab families. METHODS Direct sequencing of coding regions for AQP2 and AVPR2 was used to identify underlying mutations. One large deletion required Southern blot analysis and a PCR-based strategy to identify deletion junctions. RESULTS We identified two novel missense mutations (AQP2:p.Gly100Arg and p.Gly180Ser) in AQP2 and one novel missense mutation (AVPR2:p.Gly122Asp), one previously reported missense mutation (AVPR2:p.Arg137His) and one novel contiguous deletion (AVPR2:c.25 + 273_ARHGAP4o:2650-420del) affecting AVPR2. We also describe evidence of lyonization associated with the novel deletion. CONCLUSIONS Two novel mutations were identified in each of AVPR2 and AQP2 underlying CNDI in Arab families. Identification of these mutations will facilitate early diagnosis of CNDI, counseling of families and provide opportunities for early intervention aimed at reducing morbidity. The presence of affected females and consanguinity, as is often observed in Arab communities should not be used to rule out AVPR2 as a candidate when considering diagnostic testing. Careful observation of phenotypic heterogeneity should be used in referring such families for both AQP2 and AVPR2 molecular genetic testing.
Collapse
Affiliation(s)
- Pamela Carroll
- Aragene Laboratory, Research Centre, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | | | | | | | | | | | | | | |
Collapse
|
35
|
Robben JH, Knoers NVAM, Deen PMT. Cell biological aspects of the vasopressin type-2 receptor and aquaporin 2 water channel in nephrogenic diabetes insipidus. Am J Physiol Renal Physiol 2006; 291:F257-70. [PMID: 16825342 DOI: 10.1152/ajprenal.00491.2005] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In the renal collecting duct, water reabsorption is regulated by the antidiuretic hormone vasopressin (AVP). Binding of this hormone to the vasopressin V2 receptor (V2R) leads to insertion of aquaporin-2 (AQP2) water channels in the apical membrane, thereby allowing water reabsorption from the pro-urine to the interstitium. The disorder nephrogenic diabetes insipidus (NDI) is characterized by the kidney's inability to concentrate pro-urine in response to AVP, which is mostly acquired due to electrolyte disturbances or lithium therapy. Alternatively, NDI is inherited in an X-linked or autosomal fashion due to mutations in the genes encoding V2R or AQP2, respectively. This review describes the current knowledge of the cell biological causes of NDI and how these defects may explain the patients' phenotypes. Also, the increased understanding of these cellular defects in NDI has opened exciting initiatives in the development of novel therapies for NDI, which are extensively discussed in this review.
Collapse
MESH Headings
- Amino Acid Sequence
- Aquaporin 2/genetics
- Aquaporin 2/physiology
- DNA/genetics
- Diabetes Insipidus, Nephrogenic/etiology
- Diabetes Insipidus, Nephrogenic/genetics
- Diabetes Insipidus, Nephrogenic/physiopathology
- Diabetes Insipidus, Nephrogenic/therapy
- Gene Expression Regulation/physiology
- Genetic Diseases, X-Linked/etiology
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/physiopathology
- Genetic Diseases, X-Linked/therapy
- Humans
- Molecular Sequence Data
- Mutation/genetics
- Mutation/physiology
- Receptors, Vasopressin/genetics
- Receptors, Vasopressin/physiology
- Vasopressins/physiology
Collapse
Affiliation(s)
- Joris H Robben
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences and Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | | |
Collapse
|
36
|
Noda Y, Sasaki S. Regulation of aquaporin-2 trafficking and its binding protein complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1117-25. [PMID: 16624255 DOI: 10.1016/j.bbamem.2006.03.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 02/14/2006] [Accepted: 03/07/2006] [Indexed: 12/19/2022]
Abstract
Trafficking of water channel aquaporin-2 (AQP2) to the apical membrane is critical to water reabsorption in renal collecting ducts and its regulation maintains body water homeostasis. However, exact molecular mechanisms which recruit AQP2 are unknown. Recent studies highlighted a key role for spatial and temporal regulation of actin dynamics in AQP2 trafficking. We have recently identified AQP2-binding proteins which directly regulate this trafficking: SPA-1, a GTPase-activating protein (GAP) for Rap1, and cytoskeletal protein actin. In addition, a multiprotein "force generator" complex which directly binds to AQP2 has been discovered. This review summarizes recent advances related to the mechanism for AQP2 trafficking.
Collapse
Affiliation(s)
- Yumi Noda
- Department of Nephrology, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo 113-8519, Japan.
| | | |
Collapse
|
37
|
Bouley R, Pastor-Soler N, Cohen O, McLaughlin M, Breton S, Brown D. Stimulation of AQP2 membrane insertion in renal epithelial cells in vitro and in vivo by the cGMP phosphodiesterase inhibitor sildenafil citrate (Viagra). Am J Physiol Renal Physiol 2005; 288:F1103-12. [PMID: 15644488 DOI: 10.1152/ajprenal.00337.2004] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vasopressin-stimulated insertion of the aquaporin 2 (AQP2) water channel into the plasma membrane of kidney collecting duct principal cells is a key event in the urinary concentrating mechanism. The paradigm for vasopressin-receptor signaling involves cAMP-mediated protein kinase A activation, which results in the functionally critical phosphorylation of AQP2 on amino acid serine 256. We previously showed that a parallel cGMP-mediated signaling pathway also leads to AQP2 membrane insertion in AQP2-transfected LLC-PK1 (LLC-AQP2) cells and in outer medullary collecting duct principal cells in situ (Bouley R, Breton S, Sun T, McLaughlin M, Nsumu NN, Lin HY, Ausiello DA, and Brown D. J Clin Invest 106: 1115-1126, 2000). In the present report, we show by immunofluorescence microscopy, and Western blotting of plasma membrane fractions, that 45-min exposure of LLC-AQP2 cells to the cGMP phosphodiesterase type 5 (PDE5) inhibitors sildenafil citrate (Viagra) or 4-{[3',4'-methylene-dioxybenzyl]amino}-6-methoxyquinazoline elevates intracellular cGMP levels and results in the plasma membrane accumulation of AQP2; i.e., they mimic the vasopressin effect. Importantly, our data also show that acute exposure to PDE5 inhibitors for 60 min induces apical accumulation of AQP2 in kidney medullary collecting duct principal cells both in tissue slices incubated in vitro as well as in vivo after intravenous injection of Viagra into rats. These data suggest that AQP2 membrane insertion can be induced independently of vasopressin-receptor activation by activating a parallel cGMP-mediated signal transduction pathway with cGMP PDE inhibitors. These results provide proof-of-principle that pharmacological activation of vasopressin-independent, cGMP signaling pathways could aid in the treatment of those forms of nephrogenic diabetes insipidus that are due to vasopressin-2 receptor dysfunction.
Collapse
Affiliation(s)
- Richard Bouley
- Program in Membrane Biology and Renal Unit, Rm. 8207, Massachusetts General Hospital East, 149 13th St.. Charlestown, MA 02129, USA
| | | | | | | | | | | |
Collapse
|
38
|
Shalev H, Romanovsky I, Knoers NV, Lupa S, Landau D. Bladder function impairment in aquaporin-2 defective nephrogenic diabetes insipidus. Nephrol Dial Transplant 2004; 19:608-13. [PMID: 14767016 DOI: 10.1093/ndt/gfg574] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The aim of this study was to describe the urological complications associated with nephrogenic diabetes insipidus (NDI) due to a mutation in aquaporin-2 (AQP2), a collecting-duct protein activated by ADH signalling. METHODS We provide a case series description of a group of seven patients with autosomal recessive NDI due to AQP2 gene mutation, receiving routine medical management since diagnosis in the first months of life. RESULTS Mean urine osmolarity at diagnosis and last follow-up was 89+/-25 and 83+/-18 mosm/l, respectively. Hydroureteronephrosis was observed in all children, beginning at age 3 years. Two children have daytime enuresis at ages 7 and 10 years and all children older than 6 years continue to have nocturnal enuresis. Markedly enlarged bladders were observed as early as age 4 years in all patients. Trabeculated bladder walls were found in three children. Urodynamic studies performed in two daytime incontinent children revealed a hypotonic-large-capacity type of neurogenic bladder. No impairment in kidney function is currently observed. CONCLUSIONS The severe renal concentrating defect in this type of NDI is associated with the development of hydroureteronephrosis followed by bladder enlargement and dysfunction. Careful follow-up is needed in order to assure that no bladder outlet obstruction and/or renal insufficiency develop.
Collapse
Affiliation(s)
- Hanna Shalev
- Department of Pediatrics, Soroka University Medical Center, Ben Gurion University of the Negev, Beer Sheva, Israel
| | | | | | | | | |
Collapse
|
39
|
Abstract
The mechanisms underlying normal and abnormal cardiac rhythms are complex and incompletely understood. Through the study of uncommon inheritable arrhythmia syndromes, including the long QT and Brugada syndromes, new insights are emerging. At the cellular and tissue levels, we now recognize that ion channel current is the sum of biophysical (gating, permeation), biochemical (phosphorylation, etc), and biogenic (biosynthesis, processing, trafficking, and degradation) properties. This review focuses on how heart cells process ion channel proteins and how this protein trafficking may be altered in some cardiac arrhythmia diseases. In this review, we honor Dr Harry A. Fozzard, a modern pioneer in cardiac arrhythmias, cell biology, and molecular electrophysiology. As a scientist and physician, his writings and mentorship have served to foster a generation of investigators who continue to bring this complex field toward greater scientific understanding and impact on humankind.
Collapse
Affiliation(s)
- Brian P Delisle
- Section of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, USA
| | | | | | | |
Collapse
|
40
|
Schülein R. The early stages of the intracellular transport of membrane proteins: clinical and pharmacological implications. Rev Physiol Biochem Pharmacol 2004; 151:45-91. [PMID: 15103508 DOI: 10.1007/s10254-004-0022-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Intracellular transport mechanisms ensure that integral membrane proteins are delivered to their correct subcellular compartments. Efficient intracellular transport is a prerequisite for the establishment of both cell architecture and function. In the past decade, transport processes of proteins have also drawn the attention of clinicians and pharmacologists since many diseases have been shown to be caused by transport-deficient proteins. Membrane proteins residing within the plasma membrane are transported via the secretory (exocytotic) pathway. The general transport routes of the secretory pathway are well established. The transport of membrane proteins starts with their integration into the ER membrane. The ribosomes synthesizing membrane proteins are targeted to the ER membrane, and the nascent chains are co-translationally integrated into the bilayer, i.e., they are inserted while their synthesis is in progress. During ER insertion, the orientation (topology) of the proteins in the membrane is determined. Proteins are folded, and their folding state is checked by a quality control system that allows only correctly folded forms to leave the ER. Misfolded or incompletely folded forms are retained, transported back to the cytosol and finally subjected to proteolysis. Correctly folded proteins are transported in the membranes of vesicles through the ER/Golgi intermediate compartment (ERGIC) and the individual compartments of the Golgi apparatus ( cis, medial, trans) to the plasma membrane. In this review, the current knowledge of the first stages of the intracellular trafficking of membrane proteins will be summarized. This "early secretory pathway" includes the processes of ER insertion, topology determination, folding, quality control and the transport to the Golgi apparatus. Mutations in the genes of membrane proteins frequently lead to misfolded forms that are recognized and retained by the quality control system. Such mutations may cause inherited diseases like cystic fibrosis or retinitis pigmentosa. In the second part of this review, the clinical implications of the early secretory pathway will be discussed. Finally, new pharmacological strategies to rescue misfolded and transport-defective membrane proteins will be outlined.
Collapse
Affiliation(s)
- R Schülein
- Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany.
| |
Collapse
|
41
|
Noda Y, Sasaki S. Molecular Mechanisms and Drug Development in Aquaporin Water Channel Diseases: Molecular Mechanism of Water Channel Aquaporin-2 Trafficking. J Pharmacol Sci 2004; 96:249-54. [PMID: 15539762 DOI: 10.1254/jphs.fmj04004x2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Targeted positioning of water channel aquaporin-2 (AQP2) strictly regulates body water homeostasis. Trafficking of AQP2 to the apical membrane is critical for the reabsorption of water in renal collecting ducts. Besides the cAMP-mediated effect of vasopressin on AQP2 trafficking to the apical membrane, other signaling cascades also induce this sorting. Recently, AQP2-binding proteins that directly regulate this trafficking have been uncovered: SPA-1, a GTPase-activating protein (GAP) for Rap1, and cytoskeletal protein actin. This review summarizes recent advances related to the trafficking mechanism of AQP2 and its defect causing nephrogenic diabetes insipidus (NDI).
Collapse
Affiliation(s)
- Yumi Noda
- Department of Nephrology, Graduate School, Tokyo Medical and Dental University, Japan.
| | | |
Collapse
|
42
|
Tajima T, Okuhara K, Satoh K, Nakae J, Fujieda K. Two novel aquaporin-2 mutations in a sporadic Japanese patient with autosomal recessive nephrogenic diabetes insipidus. Endocr J 2003; 50:473-6. [PMID: 14599123 DOI: 10.1507/endocrj.50.473] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
We identified two novel mutations of the aquaporin-2 (AQP2) gene in a sporadic Japanese patient diagnosed with an autosomal recessive nephrogenic diabetes insipidus (NDI). The patient, a Japanese boy, was referred to our clinic at the age of 5 months because of unexplained recurrent fever. He was diagnosed with NDI by clinical, biochemical and endocrine findings. Molecular analysis demonstrated that he was a compound heterozygote for two mutations. One mutation consisted of a two base deletion in exon 1 (197, 198 delCA). This deletion caused a frameshift in the open reading frame, resulting in a premature stop codon 186 bases downstream in exon 1. The second mutation was a G to A transition of the terminal exon splice site (1502-1G-->A). To date, several mutations in the AQP2 gene have been described, however no splicing mutation in the AQP2 gene has been identified. The deletion mutation described in this case study was inherited patemally and the splicing site mutation was inherited maternally, indicating an autosomal recessive inheritance. In the present case study, we identified two new mutations in the AQP-2 gene. Previous studies have shown that there is no hot spot for mutations in the AQP-2 gene, and thus genetic analysis for individual patients is helpful for genetic counseling and early diagnosis.
Collapse
Affiliation(s)
- Toshihiro Tajima
- Department of Pediatrics, Hokkaido University School of Medicine, N15, W7, Kita-ku, Sapporo 060-8638, Japan
| | | | | | | | | |
Collapse
|
43
|
Hirano K, Zuber C, Roth J, Ziak M. The proteasome is involved in the degradation of different aquaporin-2 mutants causing nephrogenic diabetes insipidus. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 163:111-20. [PMID: 12819016 PMCID: PMC1868181 DOI: 10.1016/s0002-9440(10)63635-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/01/2003] [Indexed: 11/30/2022]
Abstract
Mutations in the water channel aquaporin-2 (AQP2) can cause congenital nephrogenic diabetes insipidus. To reveal the possible involvement of the protein quality control system in processing AQP2 mutants, we created an in vitro system of clone 9 hepatocytes stably expressing endoplasmic reticulum-retained T126M AQP2 and misrouted E258K AQP2 as well as wild-type AQP2 and studied their biosynthesis, degradation, and intracellular distribution. Mutant and wild-type AQP2 were synthesized as 29-kd nonglycosylated and 32-kd core-glycosylated forms in the endoplasmic reticulum. The wild-type AQP2 had a t(1/2) of 4.6 hours. Remarkable differences in the degradation kinetics were observed for the glycosylated and nonglycosylated T126M AQP2 (t(1/2) = 2.0 hours versus 0.9 hours). Moreover, their degradation was depending on proteasomal activity as demonstrated in inhibition studies. Degradation of E258K AQP2 also occurred rapidly (t(1/2) = 1.8 hours) but in a proteasome- and lysosome-dependent manner. By triple confocal immunofluorescence microscopy misrouting of E258K to lysosomes via the Golgi apparatus could be demonstrated. Notwithstanding the differences in degradation kinetics and subcellular distribution such as endoplasmic reticulum-retention and misrouting to lysosomes, both T126M and E258K AQP2 were efficiently degraded. This implies the involvement of different protein quality control processes in the processing of these AQP2 mutants.
Collapse
Affiliation(s)
- Kiyoko Hirano
- Department of Pathology, Division of Cell and Molecular Pathology, University of Zürich, Zürich, Switzerland
| | | | | | | |
Collapse
|
44
|
Marr N, Bichet DG, Hoefs S, Savelkoul PJM, Konings IBM, De Mattia F, Graat MPJ, Arthus MF, Lonergan M, Fujiwara TM, Knoers NVAM, Landau D, Balfe WJ, Oksche A, Rosenthal W, Müller D, Van Os CH, Deen PMT. Cell-biologic and functional analyses of five new Aquaporin-2 missense mutations that cause recessive nephrogenic diabetes insipidus. J Am Soc Nephrol 2002; 13:2267-77. [PMID: 12191971 DOI: 10.1097/01.asn.0000027355.41663.14] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Mutations in the Aquaporin-2 gene, which encodes a renal water channel, have been shown to cause autosomal nephrogenic diabetes insipidus (NDI), a disease in which the kidney is unable to concentrate urine in response to vasopressin. Most AQP2 missense mutants in recessive NDI are retained in the endoplasmic reticulum (ER), but AQP2-T125M and AQP2-G175R were reported to be nonfunctional channels unimpaired in their routing to the plasma membrane. In five families, seven novel AQP2 gene mutations were identified and their cell-biologic basis for causing recessive NDI was analyzed. The patients in four families were homozygous for mutations, encoding AQP2-L28P, AQP2-A47V, AQP2-V71M, or AQP2-P185A. Expression in oocytes revealed that all these mutants, and also AQP2-T125M and AQP2-G175R, conferred a reduced water permeability compared with wt-AQP2, which was due to ER retardation. The patient in the fifth family had a G>A nucleotide substitution in the splice donor site of one allele that results in an out-of-frame protein. The other allele has a nucleotide deletion (c652delC) and a missense mutation (V194I). The routing and function of AQP2-V194I in oocytes was not different from wt-AQP2; it was therefore concluded that c652delC, which leads to an out-of-frame protein, is the NDI-causing mutation of the second allele. This study indicates that misfolding and ER retention is the main, and possibly only, cell-biologic basis for recessive NDI caused by missense AQP2 proteins. In addition, the reduced single channel water permeability of AQP2-A47V (40%) and AQP2-T125M (25%) might become of therapeutic value when chemical chaperones can be found that restore their routing to the plasma membrane.
Collapse
Affiliation(s)
- Nannette Marr
- Department of Cell Physiology, UMC St. Radboud, Nijmegen, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Abstract
Nephrogenic diabetes insipidus, which can be inherited or acquired, is characterized by an inability to concentrate urine despite normal or elevated plasma concentrations of the antidiuretic hormone arginine vasopressin. Polyuria, with hyposthenuria, and polydipsia are the cardinal clinical manifestations of the disease. About 90% of patients with congenital nephrogenic diabetes insipidus are males with the X-linked recessive form of the disease (OMIM 304800) who have mutations in the arginine vasopressin receptor 2 gene (AVPR2), which codes for the vasopressin V2 receptor. The gene is located in chromosomal region Xq28. In <10% of the families studied, congenital nephrogenic diabetes insipidus has an autosomal-recessive or autosomal-dominant (OMIM 222000 and 125800, respectively) mode of inheritance. Mutations have been identified in the aquaporin-2 gene (AQP2), which is located in chromosome region 12q13 and codes for the vasopressin-sensitive water channel. When studied in vitro, most AVPR2 mutations result in receptors that are trapped intracellularly and are unable to reach the plasma membrane. A few mutant receptors reach the cell surface but are unable to bind arginine vasopressin or to properly trigger an intracellular cyclic AMP signal. Similarly, aquaporin-2 mutant proteins are misrouted and cannot be expressed at the luminal membrane. Chemical or pharmacological chaperones have been found to reverse the intracellular retention of aquaporin-2 and arginine vasopressin receptor 2 mutant proteins. Because many hereditary diseases stem from the intracellular retention of otherwise functional proteins, this mechanism may offer a new therapeutic approach to the treatment of those diseases that result from errors in protein kinesis.
Collapse
Affiliation(s)
- J P Morello
- Department of Biochemistry, Université de Montréal, Montreal, Quebec, Canada.
| | | |
Collapse
|
46
|
Levin MH, Haggie PM, Vetrivel L, Verkman AS. Diffusion in the endoplasmic reticulum of an aquaporin-2 mutant causing human nephrogenic diabetes insipidus. J Biol Chem 2001; 276:21331-6. [PMID: 11297561 DOI: 10.1074/jbc.m101901200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the aquaporin-2 (AQP2) water channel cause the hereditary renal disease nephrogenic diabetes insipidus (NDI). The missense mutation AQP2-T126M causes human recessive NDI by retention at the endoplasmic reticulum (ER) of renal epithelial cells. To determine whether the ER retention of AQP2-T126M is due to relative immobilization in the ER, we measured by fluorescence recovery after photobleaching the intramembrane mobility of green fluorescent protein (GFP) chimeras containing human wild-type and mutant AQP2. In transfected LLC-PK1 renal epithelial cells, GFP-labeled AQP2-T126M was localized to the ER, and wild-type AQP2 to endosomes and the plasma membrane; both were localized to the ER after brefeldin A treatment. Photobleaching with image detection indicated that the GFP-AQP2 chimeras were freely mobile throughout the ER. Quantitative spot photobleaching revealed a diffusion-dependent irreversible process whose recovery depended on spot size and was abolished by paraformaldehyde fixation. In addition, a novel slow reversible fluorescence recovery (t(12) approximately 2 s) was characterized whose recovery was independent of spot size and not affected by fixation. AQP2 translational diffusion in the ER was not slowed by the T126M mutation; diffusion coefficients were (in cm(2)/s x 10(-)10) 2.6 +/- 0.5 (wild-type) and 3.0 +/- 0.4 (T126M). Much faster diffusion was found for a lipid probe (diOC(4)(3), 2.7 x 10(-)8 cm(2)/s) in the ER membrane and for unconjugated GFP in the aqueous ER lumen (6 x 10(-)8 cm(2)/s). ER diffusion of GFP-T126M was not significantly affected by up-regulation of molecular chaperones, cAMP activation, or actin filament disruption. ATP depletion by 2-deoxyglucose and azide resulted in comparable slowing/immobilization of wild-type and T126M AQP2. These results indicate that the ER retention of AQP2-T126M does not result from restricted or slowed mobility and suggest that the majority of AQP2-T126M is not aggregated or bound to slowly moving membrane proteins.
Collapse
Affiliation(s)
- M H Levin
- Departments of Medicine and Physiology, Cardiovascular Research Institute, University of California, San Francisco, California 94143-0521
| | | | | | | |
Collapse
|
47
|
Schrier RW, Cadnapaphornchai MA, Umenishi F. Water-losing and water-retaining states: role of water channels and vasopressin receptor antagonists. HEART DISEASE (HAGERSTOWN, MD.) 2001; 3:210-4. [PMID: 11975794 DOI: 10.1097/00132580-200105000-00014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Alterations in water metabolism are present in conditions such as diabetes insipidus, syndrome of inappropriate antidiuretic hormone secretion, cardiac failure, cirrhosis, and pregnancy. Recent advances in molecular biology have enhanced our understanding of disordered water metabolism in these conditions. This review examines the roles of central vasopressin synthesis and release and collecting duct vasopressin V2 receptor and aquaporin-2 water channel regulation in water-losing and water-retaining states.
Collapse
Affiliation(s)
- R W Schrier
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Health Sciences Center, Denver 80262, USA.
| | | | | |
Collapse
|
48
|
Chapter 6 Trafficking of native and mutant mammalian MIP proteins. CURRENT TOPICS IN MEMBRANES 2001. [DOI: 10.1016/s1063-5823(01)51008-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
49
|
Stahlberg H, Heymann B, Mitsuoka K, Fuyijoshi Y, Engel A. Chapter 2 The aquaporin superfamily: Structure and function. CURRENT TOPICS IN MEMBRANES 2001. [DOI: 10.1016/s1063-5823(01)51004-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
50
|
Affiliation(s)
- P M Deen
- Department of Cell Physiology, University of Nijmegen, The Netherlands.
| | | | | | | |
Collapse
|