The Gcs1 and Age2 ArfGAP proteins provide overlapping essential function for transport from the yeast trans-Golgi network.
Many intracellular vesicle transport pathways involve GTP hydrolysis by the ADP-ribosylation factor (ARF) type of monomeric G proteins, under the control of ArfGAP proteins. Here we show that the structurally related yeast proteins Gcs1 and Age2 form an essential ArfGAP pair that provides overlapping function for TGN transport. Mutant cells lacking the Age2 and Gcs1 proteins cease proliferation, accumulate membranous structures resembling Berkeley bodies, and are unable to properly process and localize the vacuolar hydrolase carboxypeptidase (CPY) and the vacuolar membrane protein alkaline phosphatase (ALP), which are transported from the TGN to the vacuole by distinct transport routes. Immunofluorescence studies localizing the proteins ALP, Kex2 (a TGN resident protein), and Vps10 (the CPY receptor for transport from the TGN to the vacuole) suggest that inadequate function of this ArfGAP pair leads to a fragmentation of TGN, with effects on secretion and endosomal transport. Our results demonstrate that the Gcs1 + Age2 ArfGAP pair provides overlapping function for transport from the TGN, and also indicate that multiple activities at the TGN can be maintained with the aid of a single ArfGAP.
Poon
P P
PP
Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.
Nothwehr
S F
SF
Singer
R A
RA
Johnston
G C
GC
D020727:ADP-Ribosylation Factors / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D005804:Genes, Lethal; D006026:Glycoside Hydrolases / Q000378:metabolism; D007700:Kinetics; D008854:Microscopy, Electron; D008954:Models, Biological; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D043324:beta-Fructofuranosidase; D021601:trans-Golgi Network / Q000378:metabolism* / Q000648:ultrastructure
C444920:AGE2 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C089147:GCS1 protein, S cerevisiae; D020690:GTPase-Activating Proteins; D029701:Saccharomyces cerevisiae Proteins; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D020727:ADP-Ribosylation Factors