Abstract
Aquaporin (AQP) 5 is induced to traffic to the apical plasma membrane (APM) in rat parotid glands by the activation of M3 muscarinic acetylcholine receptors (mAChR) or α1-adrenoceptors. Sections of parotid glands were double-stained immunohistochemically with anti-AQP5 antibody and an antibody against a raft marker, either flotillin-2 or GM1. AQP5 localizes to both the APM and intracellular structures under control conditions. Ten minutes after the injection of cevimeline, AQP5 fluorescence was located predominantly on the APM of the parotid interlobular duct cells. Conversely, 60 min after the injection, there was a diffuse AQP5 staining in the cell cytoplasm. Flotillin-2 and GM1 were colocalized with AQP5 in rat parotid glands, suggesting that AQP5 is located in the lipid rafts. After injection of cevimeline, the lipid rafts move to the APM from the cytosol. CLC-K2 was also expressed in rat parotid glands and colocalized with AQP5. Under control conditions, the majority of AQP5 and CLC-K2 was localized in the Triton X-100-insoluble fraction and floated to the light-density fraction. In conclusion, AQP5 and CLC-K2 were localized in the lipid rafts and activation of M3 mAChR induced translocation of them from the lipid rafts to the APM in the interlobular ducts of rat parotid glands. [Jpn J Physiol 55 Suppl:S35 (2005)]
