254.

APICAL AND BASOLATERAL ENDOCYTIC PATHWAYS OF MDCK CELLS MEET IN ACIDIC COMMON ENDOSOMES DISTINCT FROM A NEARLY-NEUTRAL APICAL RECYCLING ENDOSOME. Wanga, E., Browna, P.S., Aroetic, B., Chapinb, S.J., Mostovb, K.E., and Dunna, K.W., a Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA b Department of Anatomy and Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA c Department of Cell and Animal Biology, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, Israel. Traffic, 1, (6), 480-493, (2003).

Abstract:
Quantitative confocal microscopic analyses of living, polarized MDCK cells demonstrate different pH profiles for apical and basolateral endocytic pathways, despite a rapid and extensive intersection between the two. Three-dimensional characterizations of ligand trafficking demonstrate that the apical and basolateral endocytic pathways share early, acidic compartments distributed throughout the medial regions of the cell. Polar sorting for both pathways occurs in these common endosomes as IgA is sorted from transferrin to alkaline transcytotic vesicles. While transferrin is directly recycled from the common endosomes, IgA is transported to a downstream apical compartment that is nearly neutral in pH. By several criteria this compartment appears to be equivalent to the previously described apical recycling endosome. The functional significance of the abrupt increase in lumenal pH that accompanies IgA sorting is not clear, as disrupting endosome acidification has no effect on polar sorting. These studies provide the first detailed characterizations of endosome acidification in intact polarized cells and clarify the relationship between the apical and basolateral endocytic itineraries of polarized MDCK cells. The extensive mixing of apical and basolateral pathways underscores the importance of endocytic sorting in maintaining the polarity of the plasma membrane of MDCK cells.

Link to Abstract

Materials & Methods:
No full text available

Microscopic Technique:
confocal microscopy

Cell Type(s):
MDCK cells