Critical Reviews in Oral Biology & Medicine, Vol 4, 407-414, Copyright © 1993 by International & American Associations for Dental Research
Identification and localization of G proteins in exocrine glands
E. L. Watson, D. Di Julio, D. Oda and K. T. Izutsu
Department of Oral Biology, University of Washington, Seattle 98195.
GTP-binding proteins were identified in rat parotid acinar plasma-enriched
membranes (PM) by immunoblot analysis and localized immunohistochemically
in the parotid gland as well as in other exocrine glands by using
affinity-purified antisera specific for alpha subunits of the G proteins.
Isolated rat parotid acinar PM immunoreacted strongly to antisera directed
against Gs alpha, Gi alpha 1/alpha 2, Gi alpha 3, and Go alpha; the signal
for Go alpha, however, was weak with crude Go antisera. Immunohistochemical
studies to identify and localize Go in rat parotid tissue revealed that
antisera to Go alpha immunoreacted with ductal cells. In addition, strong
immunoreactivity to Go alpha antisera was noted in ductal cells of other
salivary glands including rat submandibular, mouse parotid, and mouse
submandibular glands. Light labeling of rat parotid and submandibular gland
acinar cells was also noted. In contrast, in the rat and mouse pancreas, Go
antisera immunoreacted primarily with islet cells. Ductal cells were
negative, but there was light labeling of rat pancreatic acinar cells. The
apparent ductal specificity of Go alpha staining was further verified by
demonstrating that Go alpha antisera immunoreacted strongly with HSG-PA
cells, a human transformed salivary ductal cell line. The results
demonstrate that rat parotid acinar plasma membranes express a number of G
proteins including Go and that Go appears to be selectively expressed in
the ductal cells of rat parotid gland and other salivary glands. The
selective enrichment of Go in ductal cells suggests that this G protein may
play an important role in ductal cell physiology.
