Rab3d localizes to zymogen granules in rat pancreatic acini and
other exocrine glands.
Ohnishi, Hirohide, Stephen A. Ernst, Noel Wys, Mark McNiven, and John
A. Williams.
Departments of Physiology, Anatomy and Cell Biology, and Internal
Medicine
APStracts 3:0079G, 1996.
Rab3 proteins are members of the family of ras-like monomeric GTP
-binding proteins that have been implicated in secretion in neuronal
cells. Although an isoform of Rab3 has been assumed to exist in
pancreatic acini, its identity has not yet been established. We now
report that Rab3D is present in rat pancreatic acini and is localized
to the zymogen granule membrane. RT-PCR was used with primers based
on mouse Rab3D to amplify Rab3D from rat pancreas. The PCR product
without primer sites consisted of 580bp and was 94% identical to the
mouse Rab3D cDNA sequence previously cloned from adipocytes. Western
blotting with a polyclonal antiserum raised against Rab3D-specific
carboxyl-terminal amino acids identified Rab3D in rat pancreatic
acini and revealed its concentration on zymogen granule membranes.
Immunocytochemistry of pancreatic lobules showed that Rab3D localized
to the apical region in a pattern similar to amylase. Confocal
fluorescence microscopy of lobules double immunolabeled with
antibodies to Rab3D and the granule membrane marker protein GP-2
revealed a similar localization of these proteins to zymogen
granules. Immunocytochemistry also revealed the presence of Rab3D in
chief and ECL cells in the stomach, acinar cells in lacrimal, and
parotid gland and Paneth cells in the intestine. These results show
that Rab3D is expressed in rat pancreatic acini and other exocrine
secretory cells. Its location implies it may be involved in regulated
exocytosis.
Received 16 January 1996; accepted in final form 30 March 1996.
APS Manuscript Number G21-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96