Live imaging of bidirectional traffic from the ERGIC.
The endoplasmic reticulum-Golgi intermediate compartment (ERGIC) defined by the cycling lectin ERGIC-53 consists of tubulovesicular clusters, but it is unknown if these membranes are transport vehicles or stationary entities. Here, we show by live imaging that GFP-ERGIC-53 mainly localizes to long-lived stationary and some short-lived highly mobile elements. Unlike the anterograde marker VSV-G-GFP, GFP-ERGIC-53 does not vectorially move to the Golgi upon exit from the ERGIC, as assessed by a novel quantitative vector field method. Dual-color imaging of GFP-ERGIC-53 and a secretory protein (signal-sequence-tagged dsRed) reveals that the stationary elements are sites of repeated sorting of retrograde and anterograde cargo, and are interconnected by highly mobile elements. These results suggest that the ERGIC is stationary and not simply a collection of mobile carriers that mediate protein traffic from endoplasmic reticulum to Golgi.
Ben-Tekaya
Houchaima
H
Department of Pharmacology and Neurobiology, Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland.
Miura
Kota
K
Pepperkok
Rainer
R
Hauri
Hans-Peter
HP
D001693:Biological Transport, Active / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D037241:Mannose-Binding Lectins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology
C084004:LMAN1 protein, human; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D049452:Green Fluorescent Proteins