title: Immunohistochemical characterization of the intracellular pool of water channel aquaporin-2 in the rat kidney.
abstract: Aquaporin-2 (AQP2) is a member of water channel proteins expressed in the kidney collecting duct cells, where it is stored in the intracellular compartment. Upon stimulation of antidiuretic hormone (ADH), AQP2 is recruited to the plasma membrane, and plays a critical role in urine concentration. We immunohistochemically characterized the intracellular compartment harboring AQP2 in the rat kidney using antibodies to the endoplasmic reticulum, Golgi apparatus, trans-Golgi network, lysosome, and endosome. Aquaporin-2 did not colocalize with calnexin, TGN38, Golgi 58K, cathepsin D or Igp-110. Small portions of AQP2-bearing vesicles were positive for early endosome antigen 1. These localization patterns were basically the same in water-loaded and ADH-treated animals. These results indicate that AQP2-bearing vesicles constitute a unique intracellular compartment distinct from the endoplasmic reticulum, Golgi apparatus, trans-Golgi network and lysosome. Partial colocalization of AQP2 with early endosomes suggests that the endosomal system might be involved in the trafficking of AQP2.
authors.affiliation: Department of Anatomy and Cell Biology, Gunma University School of Medicine, Showa-machi, Maebashi, Gunma 371-8511, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tajika
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Matsuzaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Takeo
authors.initials: T
authors.lastname: Aoki
authors.forename: Haruo
authors.initials: H
authors.lastname: Hagiwara
authors.forename: Shigeyasu
authors.initials: S
authors.lastname: Tanaka
authors.forename: Eiki
authors.initials: E
authors.lastname: Kominami
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Takata
mesh_terms: D000818:Animals; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000378:metabolism*; D021941:Caveolae / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D015388:Organelles / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D022161:Transport Vesicles / Q000187:drug effects / Q000378:metabolism; D014667:Vasopressins / Q000378:metabolism / Q000494:pharmacology; D033921:Vesicular Transport Proteins
chemical_list: C496025:Aqp2 protein, rat; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D014667:Vasopressins