Autonomic Nerve-Regulated AQP5 Distribution in Salivary Glands and AQP5 Release into Saliva

The salivary glands are innervated by autonomic nerves. Upon activation of M3-muscarinic acetylcholine receptors or α1-adrenergic receptors, cytosolic aquaporin-5 (AQP5) is translocated from intracellular endosomes to the apical plasma membrane (APM) together with lipid rafts in the parotid acinar and duct cells. Some AQP5 is dissociated from the lipid rafts to non-rafts in the APM and the dissociated AQP5 is released into the saliva from the APM. Other AQP5 associated with lipid rafts is internalized and recycled together with the lipid rafts. The subcellular distribution of AQP5 in the salivary glands and its release into the saliva are regulated by autonomic nerves. This review focuses on autonomic nerve-regulated AQP5 trafficking in the parotid glands and AQP5 release into the saliva.