Arf3 is activated uniquely at the trans-Golgi network by brefeldin A-inhibited guanine nucleotide exchange factors.
It is widely assumed that class I and II Arfs function interchangeably throughout the Golgi complex. However, we report here that in vivo, Arf3 displays several unexpected properties. Unlike other Golgi-localized Arfs, Arf3 associates selectively with membranes of the trans-Golgi network (TGN) in a manner that is both temperature-sensitive and uniquely dependent on guanine nucleotide exchange factors of the BIGs family. For example, BIGs knockdown redistributed Arf3 but not Arf1 from Golgi membranes. Furthermore, shifting temperature to 20 degrees C, a temperature known to block cargo in the TGN, selectively redistributed Arf3 from Golgi membranes. Arf3 redistribution occurred slowly, suggesting it resulted from a change in membrane composition. Arf3 knockdown and overexpression experiments suggest that redistribution is not responsible for the 20 degrees C block. To investigate in more detail the mechanism for Arf3 recruitment and temperature-dependent release, we characterized several mutant forms of Arf3. This analysis demonstrated that those properties are readily separated and depend on pairs of residues present at opposite ends of the protein. Furthermore, phylogenetic analysis established that all four critical residues were absolutely conserved and unique to Arf3. These results suggest that Arf3 plays a unique function at the TGN that likely involves recruitment by a specific receptor.
Manolea
Florin
F
Department of Cell Biology, University of Alberta, Edmonton, AB, Canada.
Chun
Justin
J
Chen
David W
DW
Clarke
Ian
I
Summerfeldt
Nathan
N
Dacks
Joel B
JB
Melançon
Paul
P
D020823:ADP-Ribosylation Factor 1 / Q000235:genetics / Q000378:metabolism; D020727:ADP-Ribosylation Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D020126:Brefeldin A / Q000378:metabolism*; D016466:CHO Cells; D020755:Coat Protein Complex I / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D003600:Cytosol / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013696:Temperature; D021601:trans-Golgi Network / Q000378:metabolism* / Q000648:ultrastructure
D015415:Biomarkers; D020755:Coat Protein Complex I; D020662:Guanine Nucleotide Exchange Factors; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D020126:Brefeldin A; C116687:ARF3 protein, human; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors