Regulation of microtubule-dependent recycling at the trans-Golgi network by Rab6A and Rab6A'.
The small GTPase rab6A but not the isoform rab6A' has previously been identified as a regulator of the COPI-independent recycling route that carries Golgi-resident proteins and certain toxins from the Golgi to the endoplasmic reticulum (ER). The isoform rab6A' has been implicated in Golgi-to-endosomal recycling. Because rab6A but not A', binds rabkinesin6, this motor protein is proposed to mediate COPI-independent recycling. We show here that both rab6A and rab6A' GTP-restricted mutants promote, with similar efficiency, a microtubule-dependent recycling of Golgi resident glycosylation enzymes upon overexpression. Moreover, we used small interfering RNA mediated down-regulation of rab6A and A' expression and found that reduced levels of rab6 perturbs organization of the Golgi apparatus and delays Golgi-to-ER recycling. Rab6-directed Golgi-to-ER recycling seems to require functional dynactin, as overexpression of p50/dynamitin, or a C-terminal fragment of Bicaudal-D, both known to interact with dynactin inhibit recycling. We further present evidence that rab6-mediated recycling seems to be initiated from the trans-Golgi network. Together, this suggests that a recycling pathway operates at the level of the trans-Golgi linking directly to the ER. This pathway would be the preferred route for both toxins and resident Golgi proteins.
Cell Biology and Biophysics Programme, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany.
Joanne
J
Young
Tobias
T
Stauber
Elaine
E
del Nery
Isabelle
I
Vernos
Rainer
R
Pepperkok
Tommy
T
Nilsson
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins; D008870:Microtubules / Q000378:metabolism*; D009154:Mutation; D015739:Nocodazole / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D014162:Transfection; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism*
C435206:Bicd2 protein, mouse; D002352:Carrier Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; C094135:Rab6 protein; D006160:Guanosine Triphosphate; D020691:rab GTP-Binding Proteins; D015739:Nocodazole