{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,9]],"date-time":"2026-01-09T07:04:33Z","timestamp":1767942273445,"version":"3.49.0"},"reference-count":43,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,7]],"date-time":"2026-01-07T00:00:00Z","timestamp":1767744000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100031478","name":"Next Generation EU","doi-asserted-by":"crossref","award":["00000015 CUP h33c22000680006"],"award-info":[{"award-number":["00000015 CUP h33c22000680006"]}],"id":[{"id":"10.13039\/100031478","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Water deprivation triggers coordinated physiological responses to preserve body fluid balance, yet the molecular mechanisms that regulate aquaporin-mediated water transport under dehydration remain incompletely understood. Aquaporin-4 (AQP4), the main water channel in the brain and a basolateral water pathway in the kidney collecting duct, exists in multiple isoforms, including the translational readthrough variant AQP4ex, whose regulatory role is only beginning to be defined. Here, we investigated the effects of acute water deprivation (6\u201312 h) on AQP4 isoform expression and phosphorylation in a mouse kidney and brain. While total AQP4 and AQP4ex protein levels remained largely unchanged in both tissues, dehydration induced a marked and divergent regulation of the phosphorylated form of AQP4ex. Levels increased in the kidney medulla, consistent with enhanced antidiuretic water transport, but decreased in the cerebral cortex, suggesting a protective reduction in perivascular water permeability. No changes were detected in the cerebellum. These findings identify phosphorylation of AQP4ex as a rapid, tissue-specific regulatory mechanism that adjusts water flux according to the physiological needs of each organ, revealing an additional layer of control in systemic water homeostasis and highlighting AQP4ex as a potential target in dehydration-related and osmotic disorders. Future studies could explore the signaling pathways regulating AQP4ex phosphorylation and investigate its potential involvement in pathological conditions, such as diabetes insipidus or cerebral edema.<\/jats:p>","DOI":"10.3390\/ijms27020617","type":"journal-article","created":{"date-parts":[[2026,1,7]],"date-time":"2026-01-07T12:34:21Z","timestamp":1767789261000},"page":"617","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Acute Dehydration Drives Organ-Specific Modulation of Phosphorylated AQP4ex in Brain and Kidney"],"prefix":"10.3390","volume":"27","author":[{"given":"Claudia","family":"Palazzo","sequence":"first","affiliation":[{"name":"Department of Translational Biomedicine and Neurosciences, University of Bari Aldo Moro, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Roberta","family":"Pati","sequence":"additional","affiliation":[{"name":"Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, 70126 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Raffaella Pia","family":"Gatta","sequence":"additional","affiliation":[{"name":"Department of Translational Biomedicine and Neurosciences, University of Bari Aldo Moro, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Onofrio","family":"Valente","sequence":"additional","affiliation":[{"name":"Department of Translational Biomedicine and Neurosciences, University of Bari Aldo Moro, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pasqua","family":"Abbrescia","sequence":"additional","affiliation":[{"name":"Department of Translational Biomedicine and Neurosciences, University of Bari Aldo Moro, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4257-514X","authenticated-orcid":false,"given":"Grazia Paola","family":"Nicchia","sequence":"additional","affiliation":[{"name":"Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, 70126 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5284-2934","authenticated-orcid":false,"given":"Antonio","family":"Frigeri","sequence":"additional","affiliation":[{"name":"Department of Translational Biomedicine and Neurosciences, University of Bari Aldo Moro, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1038\/nrd4226","article-title":"Aquaporins: Important but Elusive Drug Targets","volume":"13","author":"Verkman","year":"2014","journal-title":"Nat. Rev. Drug Discov."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"6255","DOI":"10.1073\/pnas.91.14.6255","article-title":"The Aquaporin Family of Molecular Water Channels","volume":"91","author":"Knepper","year":"1994","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"F13","DOI":"10.1152\/ajprenal.2000.278.1.F13","article-title":"Structure and Function of Aquaporin Water Channels","volume":"278","author":"Verkman","year":"2000","journal-title":"Am. J. Physiol.-Ren. Physiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"632","DOI":"10.1093\/ndt\/gfae235","article-title":"The Biology of Water Homeostasis","volume":"40","author":"Fenton","year":"2025","journal-title":"Nephrol. Dial. Transplant."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1002\/jnr.24354","article-title":"Aquaporins in Brain Edema","volume":"98","author":"Badaut","year":"2020","journal-title":"J. Neurosci. Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2993","DOI":"10.1242\/jcs.108.9.2993","article-title":"Localization of MIWC and GLIP Water Channel Homologs in Neuromuscular, Epithelial and Glandular Tissues","volume":"108","author":"Frigeri","year":"1995","journal-title":"J. Cell Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"7437","DOI":"10.1073\/pnas.0902725106","article-title":"Crystal Structure of Human Aquaporin 4 at 1.8 \u00c5 and Its Mechanism of Conductance","volume":"106","author":"Ho","year":"2009","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2027","DOI":"10.1002\/glia.22417","article-title":"Neuromyelitis Optica IgG Does Not Alter Aquaporin-4 Water Permeability, Plasma Membrane M1\/M23 Isoform Content, or Supramolecular Assembly","volume":"60","author":"Rossi","year":"2012","journal-title":"Glia"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"13609","DOI":"10.1073\/pnas.2235843100","article-title":"Aquaporin-4 Square Array Assembly: Opposing Actions of M1 and M23 Isoforms","volume":"100","author":"Furman","year":"2003","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2936","DOI":"10.1016\/j.bpj.2011.05.012","article-title":"Model of Aquaporin-4 Supramolecular Assembly in Orthogonal Arrays Based on Heterotetrameric Association of M1-M23 Isoforms","volume":"100","author":"Jin","year":"2011","journal-title":"Biophys. J."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"790","DOI":"10.1002\/glia.23126","article-title":"Translational Readthrough Generates New Astrocyte AQP4 Isoforms That Modulate Supramolecular Clustering, Glial Endfeet Localization, and Water Transport","volume":"65","author":"Pisani","year":"2017","journal-title":"Glia"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Pati, R., Palazzo, C., Valente, O., Abbrescia, P., Messina, R., Surdo, N.C., Lefkimmiatis, K., Signorelli, F., Nicchia, G.P., and Frigeri, A. (2022). The Readthrough Isoform AQP4ex Is Constitutively Phosphorylated in the Perivascular Astrocyte Endfeet of Human Brain. Biomolecules, 12.","DOI":"10.3390\/biom12050633"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1186\/s40478-019-0707-5","article-title":"AQP4ex Is Crucial for the Anchoring of AQP4 at the Astrocyte End-Feet and for Neuromyelitis Optica Antibody Binding","volume":"7","author":"Palazzo","year":"2019","journal-title":"Acta Neuropathol. Commun."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Palazzo, C., Abbrescia, P., Valente, O., Nicchia, G.P., Banitalebi, S., Amiry-Moghaddam, M., Trojano, M., and Frigeri, A. (2020). Tissue Distribution of the Readthrough Isoform of AQP4 Reveals a Dual Role of AQP4ex Limited to CNS. Int. J. Mol. Sci., 21.","DOI":"10.3390\/ijms21041531"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1186\/s13195-022-00999-5","article-title":"Loss of Perivascular Aquaporin-4 Localization Impairs Glymphatic Exchange and Promotes Amyloid \u03b2 Plaque Formation in Mice","volume":"14","author":"Simon","year":"2022","journal-title":"Alzheimer\u2019s Res. Ther."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1093\/brain\/awab311","article-title":"Emerging Roles for Dynamic Aquaporin-4 Subcellular Relocalization in CNS Water Homeostasis","volume":"145","author":"Salman","year":"2022","journal-title":"Brain"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"957","DOI":"10.1172\/JCI231","article-title":"Generation and Phenotype of a Transgenic Knockout Mouse Lacking the Mercurial-Insensitive Water Channel Aquaporin-4","volume":"100","author":"Ma","year":"1997","journal-title":"J. Clin. Investig."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"233s","DOI":"10.1111\/j.1469-445X.2000.tb00028.x","article-title":"Role of Water Channels in Fluid Transport Studied by Phenotype Analysis of Aquaporin Knockout Mice","volume":"85","author":"Verkman","year":"2000","journal-title":"Exp. Physiol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"C549","DOI":"10.1152\/ajpcell.1998.274.2.C549","article-title":"Fourfold Reduction of Water Permeability in Inner Medullary Collecting Duct of Aquaporin-4 Knockout Mice","volume":"274","author":"Chou","year":"1998","journal-title":"Am. J. Physiol.-Cell Physiol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/j.molbrainres.2005.09.005","article-title":"Effect of Water Deprivation on Aquaporin 4 (AQP4) mRNA Expression in Chickens (Gallus domesticus)","volume":"141","author":"Saito","year":"2005","journal-title":"Mol. Brain Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1007\/978-3-540-79885-9_6","article-title":"Regulation of Aquaporin-2 Trafficking","volume":"Volume 190","author":"Beitz","year":"2009","journal-title":"Aquaporins"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"696","DOI":"10.1681\/ASN.V104696","article-title":"Regulation of Aquaporin mRNA Expression in Rat Kidney by Water Intake","volume":"10","author":"Echevarria","year":"1999","journal-title":"J. Am. Soc. Nephrol."},{"key":"ref_23","first-page":"499","article-title":"Functional Changes in the Expression of the Aqp4 Gene in the Hypothalamus Under the Influence of Drinking Regimen and Arterial Hypertension in Rats","volume":"110","author":"Evtushenko","year":"2024","journal-title":"Ross. Fiziol. \u017eurnal Im. IM Se\u010denova"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1152\/physrev.00017.2003","article-title":"Neuroendocrine Control of Body Fluid Metabolism","volume":"84","author":"Elias","year":"2004","journal-title":"Physiol. Rev."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"F930","DOI":"10.1152\/ajprenal.00291.2004","article-title":"Bidirectional Regulation of AQP2 Trafficking and Recycling: Involvement of AQP2-S256 Phosphorylation","volume":"288","author":"Nejsum","year":"2005","journal-title":"Am. J. Physiol.-Ren. Physiol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.krcp.2013.07.005","article-title":"Regulation of Aquaporin-2 in the Kidney: A Molecular Mechanism of Body-Water Homeostasis","volume":"32","author":"Kwon","year":"2013","journal-title":"Kidney Res. Clin. Pract."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"M110.004036","DOI":"10.1074\/mcp.M110.004036","article-title":"Quantitative Protein and mRNA Profiling Shows Selective Post-Transcriptional Control of Protein Expression by Vasopressin in Kidney Cells","volume":"10","author":"Khositseth","year":"2011","journal-title":"Mol. Cell. Proteom."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1013","DOI":"10.1073\/pnas.92.4.1013","article-title":"Vasopressin Increases Water Permeability of Kidney Collecting Duct by Inducing Translocation of Aquaporin-CD Water Channels to Plasma Membrane","volume":"92","author":"Nielsen","year":"1995","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"F309","DOI":"10.1152\/ajprenal.00260.2001","article-title":"Water Permeability of Aquaporin-4 Is Decreased by Protein Kinase C and Dopamine","volume":"283","author":"Zelenina","year":"2002","journal-title":"Am. J. Physiol.-Ren. Physiol."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Nesverova, V., and T\u00f6rnroth-Horsefield, S. (2019). Phosphorylation-Dependent Regulation of Mammalian Aquaporins. Cells, 8.","DOI":"10.3390\/cells8020082"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1674","DOI":"10.1096\/fj.04-3281fje","article-title":"New Possible Roles for Aquaporin-4 in Astrocytes: Cell Cytoskeleton and Functional Relationship with Connexin43","volume":"19","author":"Nicchia","year":"2005","journal-title":"FASEB J."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Mueller, S.M., McFarland White, K., Fass, S.B., Chen, S., Shi, Z., Ge, X., Engelbach, J.A., Gaines, S.H., Bice, A.R., and Vasek, M.J. (2023). Evaluation of Gliovascular Functions of AQP4 Readthrough Isoforms. Front. Cell. Neurosci., 17.","DOI":"10.3389\/fncel.2023.1272391"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"846","DOI":"10.1073\/pnas.1015217108","article-title":"Critical Role of Aquaporin-4 (AQP4) in Astrocytic Ca2+ Signaling Events Elicited by Cerebral Edema","volume":"108","author":"Thrane","year":"2011","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"112","DOI":"10.1007\/s12028-021-01326-w","article-title":"Neuronal Swelling: A Non-Osmotic Consequence of Spreading Depolarization","volume":"35","author":"Hellas","year":"2021","journal-title":"Neurocrit. Care"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"841","DOI":"10.1007\/s00424-022-02712-9","article-title":"Renal Water Transport in Health and Disease","volume":"474","author":"Feraille","year":"2022","journal-title":"Pfl\u00fcgers Arch.-Eur. J. Physiol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"852","DOI":"10.2215\/CJN.10741013","article-title":"Osmotic Homeostasis","volume":"10","author":"Danziger","year":"2015","journal-title":"Clin. J. Am. Soc. Nephrol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"RP95873","DOI":"10.7554\/eLife.95873","article-title":"Astrocyte Aquaporin Mediates a Tonic Water Efflux Maintaining Brain Homeostasis","volume":"13","author":"Pham","year":"2024","journal-title":"eLife"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"879","DOI":"10.1002\/glia.20347","article-title":"Assembly of a Perivascular Astrocyte Protein Scaffold at the Mammalian Blood\u2013Brain Barrier Is Dependent on \u03b1-Syntrophin","volume":"53","author":"Bragg","year":"2006","journal-title":"Glia"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"971","DOI":"10.1016\/j.neuroscience.2009.09.020","article-title":"Water Permeability through Aquaporin-4 Is Regulated by Protein Kinase C and Becomes Rate-Limiting for Glioma Invasion","volume":"168","author":"McCoy","year":"2010","journal-title":"Neuroscience"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1363","DOI":"10.1002\/glia.20855","article-title":"Aquaporin-4 Orthogonal Arrays of Particles Are the Target for Neuromyelitis Optica Autoantibodies","volume":"57","author":"Nicchia","year":"2009","journal-title":"Glia"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"845","DOI":"10.1002\/ana.24271","article-title":"Impairment of Paravascular Clearance Pathways in the Aging Brain","volume":"76","author":"Kress","year":"2014","journal-title":"Ann. Neurol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"869","DOI":"10.1002\/glia.20661","article-title":"Dystrophin-dependent and -independent AQP4 Pools Are Expressed in the Mouse Brain","volume":"56","author":"Nicchia","year":"2008","journal-title":"Glia"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1186\/s40478-024-01870-4","article-title":"Crucial Role of Aquaporin-4 Extended Isoform in Brain Water Homeostasis and Amyloid-\u03b2 Clearance: Implications for Edema and Neurodegenerative Diseases","volume":"12","author":"Abbrescia","year":"2024","journal-title":"Acta Neuropathol. Commun."}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/27\/2\/617\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,9]],"date-time":"2026-01-09T05:22:51Z","timestamp":1767936171000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/27\/2\/617"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,7]]},"references-count":43,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["ijms27020617"],"URL":"https:\/\/doi.org\/10.3390\/ijms27020617","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,7]]}}}