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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.
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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
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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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A multiscale model of the regulation of aquaporin 2 recycling. NPJ Syst Biol Appl 2022; 8:16. [PMID: 35534498 PMCID: PMC9085758 DOI: 10.1038/s41540-022-00223-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 03/24/2022] [Indexed: 11/08/2022] Open
Abstract
The response of cells to their environment is driven by a variety of proteins and messenger molecules. In eukaryotes, their distribution and location in the cell are regulated by the vesicular transport system. The transport of aquaporin 2 between membrane and storage region is a crucial part of the water reabsorption in renal principal cells, and its malfunction can lead to Diabetes insipidus. To understand the regulation of this system, we aggregated pathways and mechanisms from literature and derived three models in a hypothesis-driven approach. Furthermore, we combined the models to a single system to gain insight into key regulatory mechanisms of Aquaporin 2 recycling. To achieve this, we developed a multiscale computational framework for the modeling and simulation of cellular systems. The analysis of the system rationalizes that the compartmentalization of cAMP in renal principal cells is a result of the protein kinase A signalosome and can only occur if specific cellular components are observed in conjunction. Endocytotic and exocytotic processes are inherently connected and can be regulated by the same protein kinase A signal.
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Markou A, Unger L, Abir-Awan M, Saadallah A, Halsey A, Balklava Z, Conner M, Törnroth-Horsefield S, Greenhill SD, Conner A, Bill RM, Salman MM, Kitchen P. Molecular mechanisms governing aquaporin relocalisation. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183853. [PMID: 34973181 PMCID: PMC8825993 DOI: 10.1016/j.bbamem.2021.183853] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 02/07/2023]
Abstract
The aquaporins (AQPs) form a family of integral membrane proteins that facilitate the movement of water across biological membrane by osmosis, as well as facilitating the diffusion of small polar solutes. AQPs have been recognised as drug targets for a variety of disorders associated with disrupted water or solute transport, including brain oedema following stroke or trauma, epilepsy, cancer cell migration and tumour angiogenesis, metabolic disorders, and inflammation. Despite this, drug discovery for AQPs has made little progress due to a lack of reproducible high-throughput assays and difficulties with the druggability of AQP proteins. However, recent studies have suggested that targetting the trafficking of AQP proteins to the plasma membrane is a viable alternative drug target to direct inhibition of the water-conducting pore. Here we review the literature on the trafficking of mammalian AQPs with a view to highlighting potential new drug targets for a variety of conditions associated with disrupted water and solute homeostasis.
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Affiliation(s)
- Andrea Markou
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Lucas Unger
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mohammed Abir-Awan
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Ahmed Saadallah
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Andrea Halsey
- MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Zita Balklava
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Matthew Conner
- School of Sciences, Research Institute in Healthcare Science, University of Wolverhampton, Wolverhampton WV1 1LY, UK
| | | | - Stuart D Greenhill
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alex Conner
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Roslyn M Bill
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mootaz M Salman
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK; Oxford Parkinson's Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK.
| | - Philip Kitchen
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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Noda Y, Sasaki S. Updates and Perspectives on Aquaporin-2 and Water Balance Disorders. Int J Mol Sci 2021; 22:ijms222312950. [PMID: 34884753 PMCID: PMC8657825 DOI: 10.3390/ijms222312950] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 11/29/2021] [Accepted: 11/29/2021] [Indexed: 12/31/2022] Open
Abstract
Ensuring the proper amount of water inside the body is essential for survival. One of the key factors in the maintenance of body water balance is water reabsorption in the collecting ducts of the kidney, a process that is regulated by aquaporin-2 (AQP2). AQP2 is a channel that is exclusively selective for water molecules and impermeable to ions or other small molecules. Impairments of AQP2 result in various water balance disorders, including nephrogenic diabetes insipidus (NDI), which is a disease characterized by a massive loss of water through the kidney and consequent severe dehydration. Dysregulation of AQP2 is also a cause of water retention with hyponatremia in heart failure, hepatic cirrhosis, and syndrome of inappropriate antidiuretic hormone secretion (SIADH). Antidiuretic hormone vasopressin is an upstream regulator of AQP2. Its binding to the vasopressin V2 receptor promotes AQP2 targeting to the apical membrane and thus enables water reabsorption. Tolvaptan, a vasopressin V2 receptor antagonist, is effective and widely used for water retention with hyponatremia. However, there are no studies showing improvement in hard outcomes or long-term prognosis. A possible reason is that vasopressin receptors have many downstream effects other than AQP2 function. It is expected that the development of drugs that directly target AQP2 may result in increased treatment specificity and effectiveness for water balance disorders. This review summarizes recent progress in studies of AQP2 and drug development challenges for water balance disorders.
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Affiliation(s)
- Yumi Noda
- Department of Nephrology, Nitobe Memorial Nakano General Hospital, Tokyo 164-8607, Japan
- Department of Nephrology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
- Correspondence: ; Tel.: +81-3-3382-1231; Fax: +81-3-3382-1588
| | - Sei Sasaki
- Department of Nephrology, Cellular and Structural Physiology Laboratory, Tokyo Medical and Dental University, Tokyo 113-8519, Japan;
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