Recycling endosomes can serve as intermediates during transport from the Golgi to the plasma membrane of MDCK cells.
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.
Ang
Agnes Lee
AL
Department of Cell Biology, Ludwig Institute of Cancer Research, Yale University School of Medicine, New Haven, CT 06520, USA.
Taguchi
Tomohiko
T
Francis
Stephen
S
Fölsch
Heike
H
Murrells
Lindsay J
LJ
Pypaert
Marc
M
Warren
Graham
G
Mellman
Ira
I
D033961:Adaptor Protein Complex 1 / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004285:Dogs; D004705:Endocytosis; D011992:Endosomes / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D021381:Protein Transport; D014168:Transferrin; D014759:Viral Envelope Proteins / Q000378:metabolism
D033961:Adaptor Protein Complex 1; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D014168:Transferrin; D014759:Viral Envelope Proteins