Redistribution of Gαs in mouse salivary glands following β-adrenergic stimulation.
OBJECTIVE
Signalling via β-adrenergic receptors activates heterotrimeric G-proteins, which dissociate into α and βγ subunits. In salivary glands, the α subunit of Gs stimulates adenylate cyclase, increasing cyclic AMP levels and promoting exocytosis. The goals of this study were to determine Gαs localization in salivary glands and whether it undergoes redistribution upon activation.


METHODS
Mouse parotid and submandibular (SMG) glands were fixed with paraformaldehyde and prepared for immunofluorescence labelling with anti-Gαs.


RESULTS
In unstimulated parotid and SMG acinar cells, Gαs was localized mainly to basolateral membranes. Some parotid acinar cells also exhibited cytoplasmic fluorescence. Isoproterenol (IPR) stimulation resulted in decreased membrane fluorescence and increased cytoplasmic fluorescence, which appeared relatively uniform by 30 min. Beginning about 2 h after IPR, cytoplasmic fluorescence decreased and membrane fluorescence increased, approaching unstimulated levels in SMG acini by 4 h. Some parotid acini exhibited cytoplasmic fluorescence up to 8 h after IPR. The IPR-induced redistribution of Gαs was prevented (SMG) or reduced (parotid) by prior injection of propranolol. Striated duct cells of unstimulated mice exhibited general cytoplasmic fluorescence, which was unchanged after IPR.


CONCLUSIONS
Gαs is localized to basolateral membranes of unstimulated salivary acinar cells. Activation of Gαs causes its release from the cell membrane and movement into the cytoplasm. Reassociation of Gαs with the membrane begins about 2 h after stimulation in the SMG, but complete reassociation takes several hours in the parotid gland. The presence of Gαs in striated duct cells suggests a role in signal transduction of secretion and/or electrolyte transport processes.
Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, CT, USA; Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA. Electronic address: hand@uchc.edu.
Arthur R
AR
Hand
Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, CT, USA.
Kareen O
KO
Elder
Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA.
Rachael P
RP
Norris
D061354:Acinar Cells / Q000187:drug effects / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology*; D051379:Mice; D008856:Microscopy, Fluorescence; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013363:Submandibular Gland / Q000187:drug effects / Q000378:metabolism*
D044385:GTP-Binding Protein alpha Subunits; D011433:Propranolol; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D007545:Isoproterenol
Heterotrimeric G-proteins; Immunofluorescence; Isoproterenol; Parotid gland; Propranolol; Submandibular gland