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Dynamics of Salivary Gland AQP5 under Normal and Pathologic Conditions

1
Department of Molecular Oral Physiology, Division of Oral Science, Graduate School of Biomedical Sciences, Tokushima University, Tokushima-shi, Tokushima 770-8504, Japan
2
Kosei Pharmaceutical Co., Ltd., Osaka-shi, Osaka 540–0039, Japan
3
Field of Biomolecular Functions and Technology, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Tokushima-shi, Tokushima 770-8513, Japan
*
Authors to whom correspondence should be addressed.
Professor emeritus, Tokushima University.
Int. J. Mol. Sci. 2020, 21(4), 1182; https://doi.org/10.3390/ijms21041182
Received: 10 January 2020 / Revised: 4 February 2020 / Accepted: 7 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms 3.0)
Aquaporin 5 (AQP5) plays an important role in the salivary gland function. The mRNA and protein for AQP5 are expressed in the acini from embryonic days E13-16 and E17-18, respectively and for entire postnatal days. Ligation-reopening of main excretory duct induces changes in the AQP5 level which would give an insight for mechanism of regeneration/self-duplication of acinar cells. The AQP5 level in the submandibular gland (SMG) decreases by chorda tympani denervation (CTD) via activation autophagosome, suggesting that its level in the SMG under normal condition is maintained by parasympathetic nerve. Isoproterenol (IPR), a β-adrenergic agonist, raised the levels of membrane AQP5 protein and its mRNA in the parotid gland (PG), suggesting coupling of the AQP5 dynamic and amylase secretion-restoration cycle. In the PG, lipopolysaccharide (LPS) is shown to activate mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signalings and potentially downregulate AQP5 expression via cross coupling of activator protein-1 (AP-1) and NF-κB. In most species, Ser-156 and Thr-259 of AQP5 are experimentally phosphorylated, which is enhanced by cAMP analogues and forskolin. cAMP-dependent phosphorylation of AQP5 does not seem to be markedly involved in regulation of its intracellular trafficking but seems to play a role in its constitutive expression and lateral diffusion in the cell membrane. Additionally, Ser-156 phosphorylation may be important for cancer development. View Full-Text
Keywords: aquaporin 5 (AQP5); submandibular gland (SMG); parotid gland (PG); chorda tympani nerve; isoproterenol (IPR); lipopolysaccharide (LPS); mitogen-activated protein kinase (MAPK); nuclear factor-kappa B (NF-κB); phosphorylation aquaporin 5 (AQP5); submandibular gland (SMG); parotid gland (PG); chorda tympani nerve; isoproterenol (IPR); lipopolysaccharide (LPS); mitogen-activated protein kinase (MAPK); nuclear factor-kappa B (NF-κB); phosphorylation
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Hosoi, K.; Yao, C.; Hasegawa, T.; Yoshimura, H.; Akamatsu, T. Dynamics of Salivary Gland AQP5 under Normal and Pathologic Conditions. Int. J. Mol. Sci. 2020, 21, 1182.

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