Four-dimensional live imaging of apical biosynthetic trafficking reveals a post-Golgi sorting role of apical endosomal intermediates.

TitleFour-dimensional live imaging of apical biosynthetic trafficking reveals a post-Golgi sorting role of apical endosomal intermediates.
Publication TypeJournal Article
Year of Publication2014
AuthorsThuenauer R, Hsu Y-C, Carvajal-Gonzalez JMaria, Deborde S, Chuang J-Z, Römer W, Sonnleitner A, Rodriguez-Boulan E, Sung C-H
JournalProc Natl Acad Sci U S A
Volume111
Issue11
Pagination4127-32
Date Published2014 Mar 18
ISSN1091-6490
KeywordsAnimals, Biosynthetic Pathways, Cell Polarity, DNA Primers, Dogs, Epithelial Cells, Golgi Apparatus, Immunoblotting, Immunohistochemistry, Madin Darby Canine Kidney Cells, Microscopy, Confocal, Microscopy, Electron, Transmission, Microscopy, Fluorescence, Plasmids, Protein Transport, rab GTP-Binding Proteins, Rhodopsin, Transport Vesicles
Abstract

Emerging data suggest that in polarized epithelial cells newly synthesized apical and basolateral plasma membrane proteins traffic through different endosomal compartments en route to the respective cell surface. However, direct evidence for trans-endosomal pathways of plasma membrane proteins is still missing and the mechanisms involved are poorly understood. Here, we imaged the entire biosynthetic route of rhodopsin-GFP, an apical marker in epithelial cells, synchronized through recombinant conditional aggregation domains, in live Madin-Darby canine kidney cells using spinning disk confocal microscopy. Our experiments directly demonstrate that rhodopsin-GFP traffics through apical recycling endosomes (AREs) that bear the small GTPase Rab11a before arriving at the apical membrane. Expression of dominant-negative Rab11a drastically reduced apical delivery of rhodopsin-GFP and caused its missorting to the basolateral membrane. Surprisingly, functional inhibition of dynamin-2 trapped rhodopsin-GFP at AREs and caused aberrant accumulation of coated vesicles on AREs, suggesting a previously unrecognized role for dynamin-2 in the scission of apical carrier vesicles from AREs. A second set of experiments, using a unique method to carry out total internal reflection fluorescence microscopy (TIRFM) from the apical side, allowed us to visualize the fusion of rhodopsin-GFP carrier vesicles, which occurred randomly all over the apical plasma membrane. Furthermore, two-color TIRFM showed that Rab11a-mCherry was present in rhodopsin-GFP carrier vesicles and was rapidly released upon fusion onset. Our results provide direct evidence for a role of AREs as a post-Golgi sorting hub in the biosynthetic route of polarized epithelia, with Rab11a regulating cargo sorting at AREs and carrier vesicle docking at the apical membrane.

DOI10.1073/pnas.1304168111
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID24591614
PubMed Central IDPMC3964106
Grant ListEY11307 / EY / NEI NIH HHS / United States
R01 GM034107 / GM / NIGMS NIH HHS / United States
EY016805 / EY / NEI NIH HHS / United States
R01 EY016805 / EY / NEI NIH HHS / United States
EY08538 / EY / NEI NIH HHS / United States
R01 EY008538 / EY / NEI NIH HHS / United States
GM34107 / GM / NIGMS NIH HHS / United States
R01 EY011307 / EY / NEI NIH HHS / United States