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Markou A, Kitchen P, Aldabbagh A, Repici M, Salman MM, Bill RM, Balklava Z. Mechanisms of aquaporin-4 vesicular trafficking in mammalian cells. J Neurochem 2024; 168:100-114. [PMID: 38102893 PMCID: PMC10953025 DOI: 10.1111/jnc.16029] [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: 06/30/2023] [Revised: 11/24/2023] [Accepted: 12/02/2023] [Indexed: 12/17/2023]
Abstract
The aquaporin-4 (AQP4) water channel is abundantly expressed in the glial cells of the central nervous system and facilitates brain swelling following diverse insults, such as traumatic injury or stroke. Lack of specific and therapeutic AQP4 inhibitors highlights the need to explore alternative routes to control the water permeability of glial cell membranes. The cell surface abundance of AQP4 in mammalian cells fluctuates rapidly in response to changes in oxygen levels and tonicity, suggesting a role for vesicular trafficking in its translocation to and from the cell surface. However, the molecular mechanisms of AQP4 trafficking are not fully elucidated. In this work, early and recycling endosomes were investigated as likely candidates of rapid AQP4 translocation together with changes in cytoskeletal dynamics. In transiently transfected HEK293 cells a significant amount of AQP-eGFP colocalised with mCherry-Rab5-positive early endosomes and mCherry-Rab11-positive recycling endosomes. When exposed to hypotonic conditions, AQP4-eGFP rapidly translocated from intracellular vesicles to the cell surface. Co-expression of dominant negative forms of the mCherry-Rab5 and -Rab11 with AQP4-eGFP prevented hypotonicity-induced AQP4-eGFP trafficking and led to concentration at the cell surface or intracellular vesicles respectively. Use of endocytosis inhibiting drugs indicated that AQP4 internalisation was dynamin-dependent. Cytoskeleton dynamics-modifying drugs also affected AQP4 translocation to and from the cell surface. AQP4 trafficking mechanisms were validated in primary human astrocytes, which express high levels of endogenous AQP4. The results highlight the role of early and recycling endosomes and cytoskeletal dynamics in AQP4 translocation in response to hypotonic and hypoxic stress and suggest continuous cycling of AQP4 between intracellular vesicles and the cell surface under physiological conditions.
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Affiliation(s)
- Andrea Markou
- College of Health and Life SciencesAston UniversityBirminghamUK
- School of Biosciences, Faculty of Health and Medical SciencesUniversity of SurreyGuildfordUK
| | - Philip Kitchen
- College of Health and Life SciencesAston UniversityBirminghamUK
| | - Ahmed Aldabbagh
- College of Health and Life SciencesAston UniversityBirminghamUK
| | | | - Mootaz M. Salman
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
- Kavli Institute for NanoScience DiscoveryUniversity of OxfordOxfordUK
| | - Roslyn M. Bill
- College of Health and Life SciencesAston UniversityBirminghamUK
| | - Zita Balklava
- College of Health and Life SciencesAston UniversityBirminghamUK
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2
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Zhao X, Liang B, Li C, Wang W. Expression Regulation and Trafficking of Aquaporins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:39-51. [PMID: 36717485 DOI: 10.1007/978-981-19-7415-1_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Aquaporins (AQPs) mediate the bidirectional water flow driven by an osmotic gradient. Either gating or trafficking allows for rapid and specific AQP regulation in a tissue-dependent manner. The regulatory mechanisms of AQP2 are discussed mainly in this chapter, as the mechanisms controlling the regulation and trafficking of AQP2 have been very well studied. The targeting of AQP2 to the apical plasma membrane of collecting duct principal cells is mainly regulated by the action of arginine vasopressin (AVP) on the type 2 AVP receptor (V2R), which cause increased intracellular cAMP or elevated intracellular calcium levels. Activation of these intracellular signaling pathways results in vesicles bearing AQP2 transport, docking and fusion with the apical membrane, which increase density of AQP2 on the membrane. The removal of AQP2 from the membrane requires dynamic cytoskeletal remodeling. AQP2 is degraded through the ubiquitin proteasome pathway and lysosomal proteolysis pathway. Finally, we review updated findings in transcriptional and epigenetic regulation of AQP2.
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Affiliation(s)
- Xiaoduo Zhao
- Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Baien Liang
- Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Chunling Li
- Department of Physiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
| | - Weidong Wang
- Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
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3
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Insight into the Mammalian Aquaporin Interactome. Int J Mol Sci 2022; 23:ijms23179615. [PMID: 36077012 PMCID: PMC9456110 DOI: 10.3390/ijms23179615] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 08/16/2022] [Accepted: 08/22/2022] [Indexed: 01/07/2023] Open
Abstract
Aquaporins (AQPs) are a family of transmembrane water channels expressed in all living organisms. AQPs facilitate osmotically driven water flux across biological membranes and, in some cases, the movement of small molecules (such as glycerol, urea, CO2, NH3, H2O2). Protein-protein interactions play essential roles in protein regulation and function. This review provides a comprehensive overview of the current knowledge of the AQP interactomes and addresses the molecular basis and functional significance of these protein-protein interactions in health and diseases. Targeting AQP interactomes may offer new therapeutic avenues as targeting individual AQPs remains challenging despite intense efforts.
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4
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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.
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5
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Filchenko I, Blochet C, Buscemi L, Price M, Badaut J, Hirt L. Caveolin-1 Regulates Perivascular Aquaporin-4 Expression After Cerebral Ischemia. Front Cell Dev Biol 2020; 8:371. [PMID: 32523952 PMCID: PMC7261922 DOI: 10.3389/fcell.2020.00371] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 04/27/2020] [Indexed: 01/25/2023] Open
Abstract
Edema is a hallmark of many brain disorders including stroke. During vasogenic edema, blood-brain barrier (BBB) permeability increases, contributing to the entry of plasma proteins followed by water. Caveolae and caveolin-1 (Cav-1) are involved in these BBB permeability changes. The expression of the aquaporin-4 (AQP4) water channel relates to brain swelling, however, its regulation is poorly understood. Here we tested whether Cav-1 regulates AQP4 expression in the perivascular region after brain ischemia in mice. We showed that Cav-1 knockout mice had enhanced hemispheric swelling and decreased perivascular AQP4 expression in perilesional and contralateral cortical regions compared to wild-type. Glial fibrillary acidic protein-positive astrocytes displayed less branching and ramification in Cav-1 knockout mice compared to wild-type animals. There was a positive correlation between the area of perivascular AQP4-immunolabelling and branch length of Glial fibrillary acidic protein-positive astrocytes in wild-type mice, not seen in Cav-1 knockout mice. In summary, we show for the first time that loss of Cav-1 results in decreased AQP4 expression and impaired perivascular AQP4 covering after cerebral ischemia associated with altered reactive astrocyte morphology and enhanced brain swelling. Therapeutic approaches targeting Cav-1 may provide new opportunities for improving stroke outcome.
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Affiliation(s)
- Irina Filchenko
- Service of Neurology, Department of Clinical Neurosciences, CHUV, Lausanne, Switzerland.,North-Western State Medical University named after I.I. Mechnikov, Saint-Petersburg, Russia.,Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Camille Blochet
- Service of Neurology, Department of Clinical Neurosciences, CHUV, Lausanne, Switzerland.,Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Lara Buscemi
- Service of Neurology, Department of Clinical Neurosciences, CHUV, Lausanne, Switzerland.,Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Melanie Price
- Service of Neurology, Department of Clinical Neurosciences, CHUV, Lausanne, Switzerland.,Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Jerome Badaut
- Brain Molecular Imaging Lab, CNRS UMR 5287, INCIA, University of Bordeaux, Bordeaux, France.,Basic Science Department, Loma Linda University School of Medicine, Loma Linda, CA, United States
| | - Lorenz Hirt
- Service of Neurology, Department of Clinical Neurosciences, CHUV, Lausanne, Switzerland.,Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
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7
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Pizzoni A, López González M, Di Giusto G, Rivarola V, Capurro C, Ford P. AQP2 can modulate the pattern of Ca
2+
transients induced by store‐operated Ca
2+
entry under TRPV4 activation. J Cell Biochem 2018; 119:4120-4133. [DOI: 10.1002/jcb.26612] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Accepted: 12/07/2017] [Indexed: 12/15/2022]
Affiliation(s)
- Alejandro Pizzoni
- Laboratorio de Biomembranas, Facultad de Medicina, Departamento de Ciencias FisiológicasUniversidad de Buenos AiresBuenos AiresArgentina
- CONICET‐Universidad de Buenos AiresInstituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO)Buenos AiresArgentina
| | - Macarena López González
- Laboratorio de Biomembranas, Facultad de Medicina, Departamento de Ciencias FisiológicasUniversidad de Buenos AiresBuenos AiresArgentina
| | - Gisela Di Giusto
- Laboratorio de Biomembranas, Facultad de Medicina, Departamento de Ciencias FisiológicasUniversidad de Buenos AiresBuenos AiresArgentina
- CONICET‐Universidad de Buenos AiresInstituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO)Buenos AiresArgentina
| | - Valeria Rivarola
- Laboratorio de Biomembranas, Facultad de Medicina, Departamento de Ciencias FisiológicasUniversidad de Buenos AiresBuenos AiresArgentina
- CONICET‐Universidad de Buenos AiresInstituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO)Buenos AiresArgentina
| | - Claudia Capurro
- Laboratorio de Biomembranas, Facultad de Medicina, Departamento de Ciencias FisiológicasUniversidad de Buenos AiresBuenos AiresArgentina
- CONICET‐Universidad de Buenos AiresInstituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO)Buenos AiresArgentina
| | - Paula Ford
- Laboratorio de Biomembranas, Facultad de Medicina, Departamento de Ciencias FisiológicasUniversidad de Buenos AiresBuenos AiresArgentina
- CONICET‐Universidad de Buenos AiresInstituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO)Buenos AiresArgentina
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Shimizu K, Sano M, Kita A, Sawai N, Iizuka-Kogo A, Kogo H, Aoki T, Takata K, Matsuzaki T. Phosphorylation and dephosphorylation of aquaporin-2 at serine 269 and its subcellular distribution during vasopressin-induced exocytosis and subsequent endocytosis in the rat kidney . ACTA ACUST UNITED AC 2017. [DOI: 10.1679/aohc.77.25] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | - Nobuhiko Sawai
- Present address: Department of Molecular Medicine and Anatomy, Nippon Medical School,
| | | | | | - Takeo Aoki
- Present address: School of Radiological Technology, Gunma Prefectural College of Health Sciences,
| | - Kuniaki Takata
- Present address: Gunma Prefectural College of Health Sciences,
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Abstract
Aquaporins (AQPs ) are a family of membrane water channels that basically function as regulators of intracellular and intercellular water flow. To date, thirteen AQPs , which are distributed widely in specific cell types in various organs and tissues, have been characterized in humans. Four AQP monomers, each of which consists of six membrane-spanning alpha-helices that have a central water-transporting pore, assemble to form tetramers, forming the functional units in the membrane. AQP facilitates osmotic water transport across plasma membranes and thus transcellular fluid movement. The cellular functions of aquaporins are regulated by posttranslational modifications , e.g. phosphorylation, ubiquitination, glycosylation, subcellular distribution, degradation, and protein interactions. Insight into the molecular mechanisms responsible for regulated aquaporin trafficking and synthesis is proving to be fundamental for development of novel therapeutic targets or reliable diagnostic and prognostic biomarkers.
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Affiliation(s)
- Chunling Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, 74# Zhongshan Er Road, Guangzhou, 510080, China
| | - Weidong Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, 74# Zhongshan Er Road, Guangzhou, 510080, China.
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10
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Jung HJ, Kwon TH. Molecular mechanisms regulating aquaporin-2 in kidney collecting duct. Am J Physiol Renal Physiol 2016; 311:F1318-F1328. [PMID: 27760771 DOI: 10.1152/ajprenal.00485.2016] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 10/11/2016] [Accepted: 10/11/2016] [Indexed: 01/04/2023] Open
Abstract
The kidney collecting duct is an important renal tubular segment for regulation of body water homeostasis and urine concentration. Water reabsorption in the collecting duct principal cells is controlled by vasopressin, a peptide hormone that induces the osmotic water transport across the collecting duct epithelia through regulation of water channel proteins aquaporin-2 (AQP2) and aquaporin-3 (AQP3). In particular, vasopressin induces both intracellular translocation of AQP2-bearing vesicles to the apical plasma membrane and transcription of the Aqp2 gene to increase AQP2 protein abundance. The signaling pathways, including AQP2 phosphorylation, RhoA phosphorylation, intracellular calcium mobilization, and actin depolymerization, play a key role in the translocation of AQP2. This review summarizes recent data demonstrating the regulation of AQP2 as the underlying molecular mechanism for the homeostasis of water balance in the body.
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Affiliation(s)
- Hyun Jun Jung
- Epithelial Systems Biology Laboratory, Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland; and
| | - Tae-Hwan Kwon
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu, Korea
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11
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Vukićević T, Schulz M, Faust D, Klussmann E. The Trafficking of the Water Channel Aquaporin-2 in Renal Principal Cells-a Potential Target for Pharmacological Intervention in Cardiovascular Diseases. Front Pharmacol 2016; 7:23. [PMID: 26903868 PMCID: PMC4749865 DOI: 10.3389/fphar.2016.00023] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 01/25/2016] [Indexed: 01/13/2023] Open
Abstract
Arginine-vasopressin (AVP) stimulates the redistribution of water channels, aquaporin-2 (AQP2) from intracellular vesicles into the plasma membrane of renal collecting duct principal cells. By this AVP directs 10% of the water reabsorption from the 170 L of primary urine that the human kidneys produce each day. This review discusses molecular mechanisms underlying the AVP-induced redistribution of AQP2; in particular, it provides an overview over the proteins participating in the control of its localization. Defects preventing the insertion of AQP2 into the plasma membrane cause diabetes insipidus. The disease can be acquired or inherited, and is characterized by polyuria and polydipsia. Vice versa, up-regulation of the system causing a predominant localization of AQP2 in the plasma membrane leads to excessive water retention and hyponatremia as in the syndrome of inappropriate antidiuretic hormone secretion (SIADH), late stage heart failure or liver cirrhosis. This article briefly summarizes the currently available pharmacotherapies for the treatment of such water balance disorders, and discusses the value of newly identified mechanisms controlling AQP2 for developing novel pharmacological strategies. Innovative concepts for the therapy of water balance disorders are required as there is a medical need due to the lack of causal treatments.
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Affiliation(s)
- Tanja Vukićević
- Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Association Berlin, Germany
| | - Maike Schulz
- Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Association Berlin, Germany
| | - Dörte Faust
- Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Association Berlin, Germany
| | - Enno Klussmann
- Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz AssociationBerlin, Germany; German Centre for Cardiovascular ResearchBerlin, Germany
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12
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Abstract
PURPOSE OF REVIEW Aquaporin-2 (AQP2) water channels in principal cells of the kidney collecting duct are essential for urine concentration. Due to application of modern technologies, progress in our understanding of AQP2 has accelerated in recent years. In this article, we highlight some of the new insights into AQP2 function that have developed recently, with particular focus on the cell biological aspects of AQP2 regulation. RECENT FINDINGS AQP2 is subjected to a number of regulated modifications, including phosphorylation and ubiquitination, which are important for AQP2 function, cellular localization and degradation. AQP2 is likely internalized via clathrin and non-clathrin-mediated endocytosis. Regulation of AQP2 endocytosis, in addition to exocytosis, is a vital mechanism in determining overall AQP2 membrane abundance. AQP2 is associated with regulated membrane microdomains. Studies using membrane cholesterol depleting reagents, for example statins, have supported the role of membrane rafts in regulation of AQP2 trafficking. Noncanonical roles for AQP2, for example in epithelial cell migration, are emerging. SUMMARY AQP2 function and thus urine concentration is dependent on a variety of cell signalling mechanisms, posttranslational modification and interplay between AQP2 and its lipid environment. This complexity of regulation allows fine-tuning of AQP2 function and thus body water homeostasis.
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13
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Unraveling aquaporin interaction partners. Biochim Biophys Acta Gen Subj 2013; 1840:1614-23. [PMID: 24252279 DOI: 10.1016/j.bbagen.2013.11.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/07/2013] [Accepted: 11/12/2013] [Indexed: 12/18/2022]
Abstract
BACKGROUND Insight into protein-protein interactions (PPIs) is highly desirable in order to understand the physiology of cellular events. This understanding is one of the challenges in biochemistry and molecular biology today, especially for eukaryotic membrane proteins where hurdles of production, purification and structural determination must be passed. SCOPE OF REVIEW We have explored the common strategies used to find medically relevant interaction partners of aquaporins (AQPs). The most frequently used methods to detect direct contact, yeast two-hybrid interaction assay and co-precipitation, are described together with interactions specifically found for the selected targets AQP0, AQP2, AQP4 and AQP5. MAJOR CONCLUSIONS The vast majority of interactions involve the aquaporin C-terminus and the characteristics of the interaction partners are strikingly diverse. While the well-established methods for PPIs are robust, a novel approach like bimolecular fluorescence complementation (BiFC) is attractive for screening many conditions as well as transient interactions. The ultimate goal is structural evaluation of protein complexes in order to get mechanistic insight into how proteins communicate at a molecular level. GENERAL SIGNIFICANCE What we learn from the human aquaporin field in terms of method development and communication between proteins can be of major use for any integral membrane protein of eukaryotic origin. This article is part of a Special Issue entitled Aquaporins.
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Păunescu TG, Lu HAJ, Russo LM, Pastor-Soler NM, McKee M, McLaughlin MM, Bartlett BE, Breton S, Brown D. Vasopressin induces apical expression of caveolin in rat kidney collecting duct principal cells. Am J Physiol Renal Physiol 2013; 305:F1783-95. [PMID: 24133120 DOI: 10.1152/ajprenal.00622.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Caveolin (Cav)1 is expressed in the basolateral membrane domain of renal collecting duct (CD) principal cells (PCs), where it is associated with caveolae. To reveal any potential involvement of Cav1 in vasopressin signaling, we used specific monoclonal and polyclonal antibodies to examine its localization in CD PCs of Brattleboro (BB) rats treated with vasopressin (DDAVP). Compared with controls, immunofluorescence revealed a time-dependent increase in Cav1 expression in the apical membrane domain of PCs, where it overlapped with aquaporin-2 (AQP2). After 24 h of DDAVP treatment, Cav1 was visible as an increased number of small apical spots. The staining gradually became more extensive, and, after 2 wk of DDAVP, it occupied the majority of the apical membrane domain of many PCs. Cav1 also assumed an apical localization in PCs of DDAVP-treated Sprague-Dawley and Long-Evans rats. Similarly, Cav2 appeared at the apical pole of PCs after DDAVP treatment of BB, Sprague-Dawley, and Long-Evans rats. Immunogold electron microscopy confirmed bipolar Cav1 membrane expression in DDAVP-treated BB rats, whereas caveolae were only detected on the basolateral membrane. Immunoblot analysis of BB rat whole kidney homogenates revealed no significant increase in Cav1 levels in DDAVP-treated rats, suggesting that DDAVP induces Cav1 relocalization or modifies its targeting. We conclude that Cav1 and Cav2 trafficking and membrane localization are dramatically altered by the action of DDAVP. Importantly, the absence of apical caveolae indicates that while Cavs may have an as yet undetermined role in vasopressin-regulated signaling processes, this is probably unrelated to AQP2 internalization by caveolae.
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Affiliation(s)
- Teodor G Păunescu
- Program in Membrane Biology/Division of Nephrology, Massachusetts General Hospital, Simches Research Center, 185 Cambridge St., CPZN8150, Boston, MA 02114.
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15
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Matsuzaki T, Susa T, Shimizu K, Sawai N, Suzuki T, Aoki T, Yokoo S, Takata K. Function of the membrane water channel aquaporin-5 in the salivary gland. Acta Histochem Cytochem 2012; 45:251-9. [PMID: 23209334 PMCID: PMC3496861 DOI: 10.1267/ahc.12018] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Accepted: 07/11/2012] [Indexed: 01/07/2023] Open
Abstract
The process of saliva production in the salivary glands requires transepithelial water transfer from the interstitium to the acinar lumen. There are two transepithelial pathways: the transcellular and paracellular. In the transcellular pathway, the aquaporin water channels induce passive water diffusion across the membrane lipid bilayer. It is well known that aquaporin-5 (AQP5) is expressed in the salivary glands, in which it is mainly localized at the apical membrane of the acinar cells. This suggests the physiological importance of AQP5 in transcellular water transfer. Reduced saliva secretion under pilocarpine stimulation in AQP5-null mice compared with normal mice further indicates the importance of AQP5 in this process, at least in stimulated saliva secretion. Questions remain therefore regarding the role and importance of AQP5 in basal saliva secretion. It has been speculated that there would be some short-term regulation of AQP5 such as a trafficking mechanism to regulate saliva secretion. However, no histochemical evidence of AQP5-trafficking has been found, although some of biochemical analyses suggested that it may occur. There are no reports of human disease caused by AQP5 mutations, but some studies have revealed an abnormal subcellular distribution of AQP5 in patients or animals with xerostomia caused by Sjögren’s syndrome and X-irradiation. These findings suggest the possible pathophysiological importance of AQP5 in the salivary glands.
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Affiliation(s)
- Toshiyuki Matsuzaki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
| | - Taketo Susa
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
| | - Kinue Shimizu
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
| | - Nobuhiko Sawai
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
| | - Takeshi Suzuki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
| | - Takeo Aoki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
| | - Satoshi Yokoo
- Department of Stomatology and Oral Surgery, Gunma University Graduate School of Medicine
- Department of Stomatology and Oral Surgery, Gunma University Graduate School of Medicine
| | - Kuniaki Takata
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine
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