title: Localization of large ADP-ribosylation factor-guanine nucleotide exchange factors to different Golgi compartments: evidence for distinct functions in protein traffic.
abstract: Activation of several ADP-ribosylation factors (ARFs) by guanine nucleotide exchange factors (GEFs) regulates recruitment of coat proteins (COPs) on the Golgi complex and is generally assumed to be the target of brefeldin A (BFA). The large ARF-GEFs Golgi-specific BFA resistance factor 1 (GBF1) and BFA-inhibited GEFs (BIGs) localize to this organelle but catalyze exchange preferentially on class II and class I ARFs, respectively. We now demonstrate using quantitative confocal microscopy that these GEFs show a very limited overlap with each other (15 and 23%). In contrast, GBF1 colocalizes with the cis-marker p115 (86%), whereas BIGs overlap extensively with TGN38 (83%). Consistent with these distributions, GBF1, but not BIG1, partially relocalized to peripheral sites after incubation at 15 degrees C. The new GBF1 structures represent peripheral vesicular tubular clusters (VTCs) because 88% of structures analyzed stained for both GBF1 and p115. Furthermore, as expected of VTCs, they rapidly reclustered to the Golgi complex in a microtubule-dependent manner upon warm-up. These observations suggest that GBF1 and BIGs activate distinct subclasses of ARFs in specific locations to regulate different types of reactions. In agreement with this possibility, COPI overlapped to a greater extent with GBF1 (64%) than BIG1 (31%), whereas clathrin showed limited overlap with BIG1, and virtually none with GBF1.
authors.affiliation: Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Zhao
authors.forename: Troy K R
authors.initials: TK
authors.lastname: Lasell
authors.forename: Paul
authors.initials: P
authors.lastname: Melançon
mesh_terms: D020727:ADP-Ribosylation Factors / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002460:Cell Line; D020755:Coat Protein Complex I / Q000378:metabolism; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D051790:G-Box Binding Factors; D006023:Glycoproteins; D006056:Golgi Apparatus / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000032:analysis* / Q000276:immunology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D018613:Microscopy, Confocal; D008870:Microtubules / Q000187:drug effects; D015739:Nocodazole / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D012097:Repressor Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D020755:Coat Protein Complex I; D004268:DNA-Binding Proteins; D051790:G-Box Binding Factors; D006023:Glycoproteins; D020662:Guanine Nucleotide Exchange Factors; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011500:Protein Synthesis Inhibitors; D012097:Repressor Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; C513045:Tgoln2 protein, rat; D014157:Transcription Factors; D020126:Brefeldin A; D019869:Phosphatidylinositol 3-Kinases; D020727:ADP-Ribosylation Factors; D015739:Nocodazole