The AP-1B clathrin adaptor complex is responsible for the polarized transport of many basolateral membrane proteins in epithelial cells. Localization of AP-1B to recycling endosomes (REs) along with other components (exocyst subunits and Rab8) involved in AP-1B–dependent transport suggested that RE might be an intermediate between the Golgi and the plasma membrane. Although the involvement of endosomes in the secretory pathway has long been suspected, we now present direct evidence using four independent methods that REs play a role in basolateral transport in MDCK cells. Newly synthesized AP-1B–dependent cargo, vesicular stomatitis virus glycoprotein G (VSV-G), was found by video microscopy, immunoelectron microscopy, and cell fractionation to enter transferrin-positive REs within a few minutes after exit from the trans-Golgi network. Although transient, RE entry appears essential because enzymatic inactivation of REs blocked VSV-G delivery to the cell surface. Because an apically targeted VSV-G mutant behaved similarly, these results suggest that REs not only serve as an intermediate but also as a common site for polarized sorting on the endocytic and secretory pathways.
Recycling endosomes can serve as intermediates during transport from the Golgi to the plasma membrane of MDCK cells
T. Taguchi's present address is 21st Century Center for Excellence Program and Dept. of Biochemistry, Osaka University School of Medicine, 2-2 Yamadaoka, Suite, Osaka, 565-0871 Japan.
Abbreviations used in this paper: CHX, cycloheximide; MFI, mean fluorescence intensity; RE, recycling endosome; Tfn, transferrin; TfnR, Tfn receptor; VSV-G, vesicular stomatitis virus glycoprotein G.
Agnes Lee Ang, Tomohiko Taguchi, Stephen Francis, Heike Fölsch, Lindsay J. Murrells, Marc Pypaert, Graham Warren, Ira Mellman; Recycling endosomes can serve as intermediates during transport from the Golgi to the plasma membrane of MDCK cells . J Cell Biol 8 November 2004; 167 (3): 531–543. doi: https://doi.org/10.1083/jcb.200408165
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