Na,k-atpase in lacrimal gland acinar cell endosomal system,
correcting a case of mistaken identity.
Gierow, J. Peter, Tao Yang, Arpi Bekmezian, Nelson Liu, John M.
Norian, Shin Ae Kim, Sina Rafisolyman, Hongtao Zeng, Curtis T.
Okamoto, Richard L. Wood, and Austin K. Mircheff.
Departments of Physiology & Biophysics, Cell & Neurobiology,
and Ophthalmology, University of Southern California School of
Medicine, Department of Pharmaceutical Sciences, University of
Southern California School of Pharmacy, Los Angeles, California
90033
APStracts 3:0168C, 1996.
Na,K-ATPase is associated with a variety of membrane populations in
lacrimal acinar cells. Acinus-like structures formed by rabbit acinar
cells in primary culture were incubated with horseradish peroxidase
(HRP) to label basal-lateral and endosomal membranes, then analyzed
by EM cytochemistry with the diaminobenzidine reaction or by
fractionation and measurement of marker catalytic activities or
immunoreactivities. HRP adsorbed to basal-lateral membranes at 4
degrees C. Fractionation showed it associated with low-density
membranes enriched in acid phosphatase and TGN38 but containing only
minor amounts of Na,K-ATPase. Cells internalized HRP to cytoplasmic
vesicles, Golgi structures, and lysosomes at 37 degrees C. The major
endosomal compartment revealed by fractionation coincided with major
peaks of Na,K-ATPase and Rab6 and secondary peaks of
galactosyltransferase and _-adaptin. Carbachol (10 [mu]M) increased
lysosomal and Golgi labeling. Thus, most of the Na,K-ATPase is
located in the basal-lateral membrane-oriented endosomal system,
concentrated in a compartment possibly related to the trans-Golgi
network. Constitutive and stimulation-accelerated traffic to and from
this compartment may serve several exocrine cell functions.
Received 26 March 1996; accepted in final form 15 May 1996.
APS Manuscript Number C172-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96