Activation of muscarinic receptors in rat parotid acinar cells induces AQP5 trafficking to nuclei and apical plasma membrane.
BACKGROUND
The subcellular distribution of aquaporin-5 (AQP5) in rat parotid acinar cells in response to muscarinic acetylcholine receptor (mAChR) activation remains unclear.


METHODS
Immunoconfocal and immunoelectron microscopy were used to visualize the distribution of AQP5 in parotid acinar cells. Western blotting was used to analyze AQP5 levels in membranes. To clarify the characteristics of membrane domains associated with AQP5, detergent solubility and sucrose-density flotation experiments were performed.


RESULTS
Under control conditions, AQP5 was diffusely distributed on the apical plasma membrane (APM) and apical plasmalemmal region and throughout the cytoplasm. Upon mAChR activation, AQP5 was predominantly located in the nucleus, APM and lateral plasma membrane (LPM). Subsequently, localization of AQP5 in the nucleus, APM and LPM was decreased. Prolonged atropine treatment inhibited mAChR agonist-induced translocation of AQP5 to the nucleus, APM and LPM. AQP5 levels were enhanced in isolated nuclei and nuclear membranes prepared from parotid tissues incubated with mAChR agonist. mAChR agonist induced AQP5 levels in both soluble and insoluble nuclear fractions solubilized with Triton X-100 or Lubrol WX. Small amounts of AQP5 in nuclei were detected using low-density sucrose gradient. When AQP5 was present in the nuclear membrane, nuclear size decreased.


CONCLUSION
The activation of mAChR induced AQP5 translocation to the nucleus, APM and LPM, and AQP5 may trigger water transport across the nuclear membrane and plasma membrane in rat parotid acinar cells.


GENERAL SIGNIFICANCE
AQP5 translocates to the nuclear membrane and may trigger the movement of water, inducing shrinkage of the nucleus and the start of nuclear functions.
['Cho|Gota|G|', 'Bragiel|Aneta M|AM|', 'Wang|Di|D|', 'Pieczonka|Tomasz D|TD|', 'Skowronski|Mariusz T|MT|', 'Shono|Masayuki|M|', 'Nielsen|Søren|S|', 'Ishikawa|Yasuko|Y|']
D061354:Acinar Cells D000818:Animals D051402:Aquaporin 5 D002462:Cell Membrane D002467:Cell Nucleus D008297:Male D021962:Membrane Microdomains D009685:Nuclear Envelope D010306:Parotid Gland D021381:Protein Transport D051381:Rats D017208:Rats, Wistar D011976:Receptors, Muscarinic
Acinar cells Trafficking Nuclei Apical plasma membrane Aquaporin-5 Parotid glands