Acute Hypertonicity Alters Aquaporin-2 Trafficking and Induces a MAPK-dependent Accumulation at the Plasma Membrane of Renal Epithelial Cells

• Published in: The Journal of biological chemistry Vol. 283; no. 39; pp. 26643 - 26661
• Main Authors: Hasler, Udo, Nunes, Paula, Bouley, Richard, Lu, Hua A.J., Matsuzaki, Toshiyuki, Brown, Dennis
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.09.2008; American Society for Biochemistry and Molecular Biology
• Subjects: Adaptation, Physiological - drug effects; Adaptation, Physiological - physiology; Animals; Antidiuretic Agents - pharmacology; Aquaporin 2 - genetics; Aquaporin 2 - metabolism; Biological Transport, Active - drug effects; Biological Transport, Active - physiology; Cell Line; Cyclic AMP - genetics; Cyclic AMP - metabolism; Cyclic AMP-Dependent Protein Kinases - genetics; Cyclic AMP-Dependent Protein Kinases - metabolism; Cytosol - metabolism; Endocytosis - drug effects; Endocytosis - physiology; Epithelial Cells - cytology; Epithelial Cells - metabolism; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Golgi Apparatus - metabolism; Kidney Tubules, Collecting - cytology; Kidney Tubules, Collecting - metabolism; MAP Kinase Signaling System - drug effects; MAP Kinase Signaling System - physiology; Mechanisms of Signal Transduction; Mitogen-Activated Protein Kinase 1 - genetics; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - genetics; Mitogen-Activated Protein Kinase 3 - metabolism; Mutation; Osmotic Pressure - drug effects; p38 Mitogen-Activated Protein Kinases - genetics; p38 Mitogen-Activated Protein Kinases - metabolism; Phosphorylation - drug effects; Protein Transport - drug effects; Protein Transport - physiology; Rats; Rats, Brattleboro; Vasopressins - pharmacology; Water - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M801071200

The unique phenotype of renal medullary cells allows them to survive and functionally adapt to changes of interstitial osmolality/tonicity. We investigated the effects of acute hypertonic challenge on AQP2 (aquaporin-2) water channel trafficking. In the absence of vasopressin, hypertonicity alone induced rapid (<10 min) plasma membrane accumulation of AQP2 in rat kidney collecting duct principal cells in situ, and in several kidney epithelial lines. Confocal microscopy revealed that AQP2 also accumulated in the trans-Golgi network (TGN) following hypertonic challenge. AQP2 mutants that mimic the Ser256-phosphorylated and -nonphosphorylated state accumulated at the cell surface and TGN, respectively. Hypertonicity did not induce a change in cytosolic cAMP concentration, but inhibition of either calmodulin or cAMP-dependent protein kinase A activity blunted the hypertonicity-induced increase of AQP2 cell surface expression. Hypertonicity increased p38, ERK1/2, and JNK MAPK activity. Inhibiting MAPK activity abolished hypertonicity-induced accumulation of AQP2 at the cell surface but did not affect either vasopressin-dependent AQP2 trafficking or hypertonicity-induced AQP2 accumulation in the TGN. Finally, increased AQP2 cell surface expression induced by hypertonicity largely resulted from a reduction in endocytosis but not from an increase in exocytosis. These data indicate that acute hypertonicity profoundly alters AQP2 trafficking and that hypertonicity-induced AQP2 accumulation at the cell surface depends on MAP kinase activity. This may have important implications on adaptational processes governing transcellular water flux and/or cell survival under extreme conditions of hypertonicity.