title: Presence and localization of aquaporin-6 in rat parotid acinar cells.
abstract: Aquaporins (AQPs) are integral membrane proteins that function as channels for the transfer of water and small solutes across membranes. In mammalian cells, 13 isoforms (AQP0-12) have been identified, and these exhibit unique patterns of expression in various cell types and tissues. Among these isoforms, AQP6 is considered to function not as water channel, but as an anion channel. We investigated the presence and localization of AQP6 in rat parotid acinar cells. AQP6 mRNA was detected in these cells by using reverse transcription/polymerase chain reaction, and Western blotting analysis identified a protein band that reacted with an anti-AQP6 antibody in the membrane fraction and secretory granule membrane. In order to localize AQP6, we used the anti-AQP6 antibody for histological immunodetection. Under confocal microscopy, we observed positive immunoreactions near the tight junctions of parotid acinar cells. Immunolabeling of ultrathin cryosections detected AQP6 near tight junctions and around secretory granule membranes. Immunoelectron microscopy confirmed the presence of AQP6 in the membranes of isolated secretory granules. These results suggest that AQP6 participates in water and anion transport in plasma membranes near tight junctions and secretory granule membranes in rat parotid acinar cells.
authors.affiliation: Department of Physiology and Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan.
authors.forename: Miwako
authors.initials: M
authors.lastname: Matsuki-Fukushima
authors.forename: Sadamitsu
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Masaki
authors.initials: M
authors.lastname: Shimono
authors.forename: Keitaro
authors.initials: K
authors.lastname: Satoh
authors.forename: Junko
authors.initials: J
authors.lastname: Fujita-Yoshigaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugiya
mesh_terms: D000818:Animals; D051403:Aquaporin 6 / Q000235:genetics / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D007679:Kidney Medulla / Q000166:cytology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D010306:Parotid Gland / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D022142:Secretory Vesicles / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism; D062826:Zonula Occludens-1 Protein
chemical_list: C496043:Aqp6 protein, rat; D051403:Aquaporin 6; D008565:Membrane Proteins; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein