Distinct functions for Arf guanine nucleotide exchange factors at the Golgi complex: GBF1 and BIGs are required for assembly and maintenance of the Golgi stack and trans-Golgi network, respectively.
We examined the relative function of the two classes of guanine nucleotide exchange factors (GEFs) for ADP-ribosylation factors that regulate recruitment of coat proteins on the Golgi complex. Complementary overexpression and RNA-based knockdown approaches established that GBF1 regulates COPI recruitment on cis-Golgi compartments, whereas BIGs appear specialized for adaptor proteins on the trans-Golgi. Knockdown of GBF1 and/or COPI did not prevent export of VSVGtsO45 from the endoplasmic reticulum (ER), but caused its accumulation into peripheral vesiculotubular clusters. In contrast, knockdown of BIG1 and BIG2 caused loss of clathrin adaptor proteins and redistribution of several TGN markers, but had no impact on COPI and several Golgi markers. Surprisingly, brefeldin A-inhibited guanine nucleotide exchange factors (BIGs) knockdown prevented neither traffic of VSVGtsO45 to the plasma membrane nor assembly of a polarized Golgi stack. Our observations indicate that COPII is the only coat required for sorting and export from the ER exit sites, whereas GBF1 but not BIGs, is required for COPI recruitment, Golgi subcompartmentalization, and cargo progression to the cell surface.
Manolea
Florin
F
Department of Cell Biology, University of Alberta, Edmonton, AB, T6G 2H7 Canada.
Claude
Alejandro
A
Chun
Justin
J
Rosas
Javier
J
Melançon
Paul
P
D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D020755:Coat Protein Complex I / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D008985:Monensin / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism; D021601:trans-Golgi Network / Q000187:drug effects / Q000378:metabolism*
C119087:ARFGEF1 protein, human; C119088:ARFGEF2 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D002966:Clathrin; D020755:Coat Protein Complex I; C028391:G protein, vesicular stomatitis virus; C120445:GBF1 protein, human; D020662:Guanine Nucleotide Exchange Factors; D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; D008985:Monensin; D020727:ADP-Ribosylation Factors