Rab6 coordinates a novel Golgi to ER retrograde transport pathway in live cells.
We visualized a fluorescent-protein (FP) fusion to Rab6, a Golgi-associated GTPase, in conjunction with fluorescent secretory pathway markers. FP-Rab6 defined highly dynamic transport carriers (TCs) translocating from the Golgi to the cell periphery. FP-Rab6 TCs specifically accumulated a retrograde cargo, the wild-type Shiga toxin B-fragment (STB), during STB transport from the Golgi to the endoplasmic reticulum (ER). FP-Rab6 TCs associated intimately with the ER, and STB entered the ER via specialized peripheral regions that accumulated FP-Rab6. Microinjection of antibodies that block coatomer protein I (COPI) function inhibited trafficking of a KDEL-receptor FP-fusion, but not FP-Rab6. Additionally, markers of COPI-dependent recycling were excluded from FP-Rab6/STB TCs. Overexpression of Rab6:GDP (T27N mutant) using T7 vaccinia inhibited toxicity of Shiga holotoxin, but did not alter STB transport to the Golgi or Golgi morphology. Taken together, our results indicate Rab6 regulates a novel Golgi to ER transport pathway.
White
J
J
Light Microscopy Group, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany. jwhite@embl-heidelberg.de
Johannes
L
L
Mallard
F
F
Girod
A
A
Grill
S
S
Reinsch
S
S
Keller
P
P
Tzschaschel
B
B
Echard
A
A
Goud
B
B
Stelzer
E H
EH
D000818:Animals; D001427:Bacterial Toxins / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D018000:Receptors, Peptide / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022603:Shiga Toxins; D014162:Transfection; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D001427:Bacterial Toxins; C064459:KDEL receptor; D008164:Luminescent Proteins; C094135:Rab6 protein; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; D022603:Shiga Toxins; D049452:Green Fluorescent Proteins; D020691:rab GTP-Binding Proteins