The role of ARF1 and rab GTPases in polarization of the Golgi stack.
The organization and sorting of proteins within the Golgi stack to establish and maintain its cis to trans polarization remains an enigma. The function of Golgi compartments involves coat assemblages that facilitate vesicle traffic, Rab-tether-SNAP receptor (SNARE) machineries that dictate membrane identity, as well as matrix components that maintain structure. We have investigated how the Golgi complex achieves compartmentalization in response to a key component of the coat complex I (COPI) coat assembly pathway, the ARF1 GTPase, in relationship to GTPases-regulating endoplasmic reticulum (ER) exit (Sar1) and targeting fusion (Rab1). Following collapse of the Golgi into the ER in response to inhibition of activation of ARF1 by Brefeldin A, we found that Sar1- and Rab1-dependent Golgi reformation took place at multiple peripheral and perinuclear ER exit sites. These rapidly converged into immature Golgi that appeared as onion-like structures composed of multiple concentrically arrayed cisternae of mixed enzyme composition. During clustering to the perinuclear region, Golgi enzymes were sorted to achieve the degree of polarization within the stack found in mature Golgi. Surprisingly, we found that sorting of Golgi enzymes into their subcompartments was insensitive to the dominant negative GTP-restricted ARF1 mutant, a potent inhibitor of COPI coat disassembly and vesicular traffic. We suggest that a COPI-independent, Rab-dependent mechanism is involved in the rapid reorganization of resident enzymes within the Golgi stack following synchronized release from the ER, suggesting an important role for Rab hubs in directing Golgi polarization.
Bannykh
Serguei I
SI
Department of Pathology, Yale University Medical School, 310 Cedar Street, New Haven, CT 06520, USA.
Plutner
Helen
H
Matteson
Jeanne
J
Balch
William E
WE
D020823:ADP-Ribosylation Factor 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D045744:Cell Line, Tumor; D020755:Coat Protein Complex I / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D019084:Fluorescent Antibody Technique, Indirect; D006056:Golgi Apparatus / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D008361:Mannosidases / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000648:ultrastructure; D008845:Microinjections; D008856:Microscopy, Fluorescence; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009154:Mutation; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013696:Temperature; D014616:Vaccinia virus / Q000235:genetics / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism / Q000648:ultrastructure; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D020761:rab1 GTP-Binding Proteins / Q000378:metabolism
D020755:Coat Protein Complex I; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D011500:Protein Synthesis Inhibitors; D011994:Recombinant Proteins; D014759:Viral Envelope Proteins; D020126:Brefeldin A; D008361:Mannosidases; C038829:mannosyl-oligosaccharide 1,3 - 1,6-alpha-mannosidase; C487879:SAR1 protein, rat; D020823:ADP-Ribosylation Factor 1; D020559:Monomeric GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D020761:rab1 GTP-Binding Proteins