title: Identification of AQP5 in lipid rafts and its translocation to apical membranes by activation of M3 mAChRs in interlobular ducts of rat parotid gland.
abstract: Aquaporin-5 (AQP5), an apical plasma membrane (APM) water channel in salivary glands, lacrimal glands, and airway epithelium, has an important role in fluid secretion. M(3) muscarinic acetylcholine receptor (mAChR)-induced changes in AQP5 localization in rat parotid glands were investigated with immunofluorescence or immunoelectron microscopy, detergent solubility, and gradient density floatation assays. Confocal microscopy revealed AQP5 localization in intracellular vesicles of interlobular duct cells in rat parotid glands and AQP5 trafficking to the APM 10 min after injection of the mAChR agonist cevimeline. Conversely, 60 min after injection, there was a diffuse pattern of AQP5 staining in the cell cytoplasm. The calcium ionophore A-23187 mimicked the effects of cevimeline. Immunoelectron microscopic studies confirmed that cevimeline induced AQP5 trafficking from intracellular structures to APMs in the interlobular duct cells of rat parotid glands. Lipid raft markers flotillin-2 and GM1 colocalized with AQP5 and moved with AQP5 in response to cevimeline. Under control conditions, the majority of AQP5 localized in the Triton X-100-insoluble fraction and floated to the light-density fraction on discontinuous density gradients. After 10-min incubation of parotid tissue slices with cevimeline or A-23187, AQP5 levels decreased in the Triton X-100-insoluble fraction and increased in the Triton X-100-soluble fraction. Thus AQP5 localizes in the intracellular lipid rafts, and M(3) mAChR activation induces AQP5 trafficking to the APM with lipid rafts via intracellular Ca(2+) signaling and induces AQP5 dissociation from lipid rafts to nonrafts on the APM in the interlobular duct cells of rat parotid glands.
authors.affiliation: Department of Medical Pharmacology, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15, Kuramoto-cho, Tokushima 770-8504, Japan. isikawa@dent.tokushima-u.ac.jp
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Zhenfang
authors.initials: Z
authors.lastname: Yuan
authors.forename: Noriko
authors.initials: N
authors.lastname: Inoue
authors.forename: Mariusz T
authors.initials: MT
authors.lastname: Skowronski
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Nakae
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shono
authors.forename: Gota
authors.initials: G
authors.lastname: Cho
authors.forename: Masato
authors.initials: M
authors.lastname: Yasui
authors.forename: Peter
authors.initials: P
authors.lastname: Agre
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D051402:Aquaporin 5; D020346:Aquaporins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation; D054769:G-Protein-Coupled Receptor Kinase 2; D008297:Male; D021962:Membrane Microdomains / Q000737:chemistry / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D010306:Parotid Gland / Q000187:drug effects / Q000502:physiology*; D021381:Protein Transport; D011812:Quinuclidines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D013876:Thiophenes / Q000494:pharmacology
chemical_list: C496040:Aqp5 protein, rat; D051402:Aquaporin 5; D020346:Aquaporins; D008565:Membrane Proteins; D011812:Quinuclidines; D013876:Thiophenes; D020794:Receptor Protein-Tyrosine Kinases; C080577:muscarinic receptor kinase; D054769:G-Protein-Coupled Receptor Kinase 2; C059240:cevimeline; D002118:Calcium