title: Effect on stability, degradation, expression, and targeting of aquaporin-2 water channel by hyperosmolality in renal epithelial cells.
abstract: To investigate the stability, degradation, expression, and targeting of aquaporin-2 (AQP2) by hyperosmolality, stably transfected mIMCD-3 cells expressing AQP2 (AQP2/IMCD3) were generated. In AQP2/IMCD3 cells, both nonglycosylated (ng-AQP2) and glycosylated (g-AQP2) forms were detected by immunoblot. The stability of ng-AQP2 decreased with the lapse of time, whereas that of g-AQP2 was stable. NaCl, but not urea, destabilized ng-AQP2. The half-life of ng-AQP2 in isotonic conditions was approximately 5 h, whereas that in medium supplemented with NaCl was approximately 1.5 h. Urea enhanced it compared to isotonic conditions. These findings indicate that the stability of ng-AQP2 is enhanced by urea, but not NaCl. The degradation of ng-AQP2 was dependent on proteasome and lysosome degradation pathways. The expression of ng-AQP2 was increased by hyperosmolality. Cell surface biotinylation experiments revealed that hyperosmolality enhanced the apical membrane insertion of ng-AQP2. These results indicate that hyperosmolality plays an important role in the stability, degradation, expression, and targeting of ng-AQP2.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA. Fuminori.Umenishi@UCHSC.edu
authors.forename: Fuminori
authors.initials: F
authors.lastname: Umenishi
authors.forename: Takefumi
authors.initials: T
authors.lastname: Narikiyo
authors.forename: Robert W
authors.initials: RW
authors.lastname: Schrier
mesh_terms: D000818:Animals; D051399:Aquaporin 2 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007668:Kidney / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D009997:Osmotic Pressure; D011489:Protein Denaturation / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology; D014508:Urea / Q000494:pharmacology
chemical_list: D051399:Aquaporin 2; D012965:Sodium Chloride; D014508:Urea