Limits...
The Gcs1 and Age2 ArfGAP proteins provide overlapping essential function for transport from the yeast trans-Golgi network.

Poon PP, Nothwehr SF, Singer RA, Johnston GC - J. Cell Biol. (2001)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.

ABSTRACT
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.

Show MeSH

Related in: MedlinePlus

Vesicular transport stages mediated by ArfGAP pairs. Large arrows indicate vesicular transport pathways from the TGN mediated by the Gcs1 + Age2 ArfGAP pair and the retrograde Golgi-to-ER pathway mediated by the Gcs1 + Glo3 ArfGAP pair.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2199332&req=5

fig10: Vesicular transport stages mediated by ArfGAP pairs. Large arrows indicate vesicular transport pathways from the TGN mediated by the Gcs1 + Age2 ArfGAP pair and the retrograde Golgi-to-ER pathway mediated by the Gcs1 + Glo3 ArfGAP pair.

Mentions: The hypothesis that the Gcs1 + Age2 ArfGAP pair primarily influences transport at the TGN is consistent with the known roles for ARF proteins at the Golgi complex. ARF proteins mediate the recruitment of both AP-1 adaptor complexes and AP-3 complexes onto TGN membranes for transport-vesicle formation (Stamnes and Rothman, 1993; Ooi et al., 1998), so that defective regulation of the ARF cycle of GTP binding and hydrolysis, as expected for the situation investigated here in which an overlapping essential activity of the Gcs1 and Age2 ArfGAPs is diminished, would affect the formation and/or function of both AP-1 and AP-3 transport vesicles. AP-1 vesicles assembled at the TGN are thought to be targeted to endosomal compartments (Deloche et al., 2001), such that impaired vesicle formation at the TGN would lead to defective delivery of vesicular transport components needed for endosomal trafficking. Therefore, the effects that we observe on endosomal function and movement of material from the plasma membrane to the vacuole may be indirect consequences of impaired TGN export. Consequently, we propose that the Gcs1 + Age2 ArfGAP pair mediates the formation and/or function of TGN-derived transport vesicles for both endosomal (CPY) and AP-3–dependent nonendosomal (ALP) pathways (Fig. 10).


The Gcs1 and Age2 ArfGAP proteins provide overlapping essential function for transport from the yeast trans-Golgi network.

Poon PP, Nothwehr SF, Singer RA, Johnston GC - J. Cell Biol. (2001)

Vesicular transport stages mediated by ArfGAP pairs. Large arrows indicate vesicular transport pathways from the TGN mediated by the Gcs1 + Age2 ArfGAP pair and the retrograde Golgi-to-ER pathway mediated by the Gcs1 + Glo3 ArfGAP pair.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199332&req=5

fig10: Vesicular transport stages mediated by ArfGAP pairs. Large arrows indicate vesicular transport pathways from the TGN mediated by the Gcs1 + Age2 ArfGAP pair and the retrograde Golgi-to-ER pathway mediated by the Gcs1 + Glo3 ArfGAP pair.
Mentions: The hypothesis that the Gcs1 + Age2 ArfGAP pair primarily influences transport at the TGN is consistent with the known roles for ARF proteins at the Golgi complex. ARF proteins mediate the recruitment of both AP-1 adaptor complexes and AP-3 complexes onto TGN membranes for transport-vesicle formation (Stamnes and Rothman, 1993; Ooi et al., 1998), so that defective regulation of the ARF cycle of GTP binding and hydrolysis, as expected for the situation investigated here in which an overlapping essential activity of the Gcs1 and Age2 ArfGAPs is diminished, would affect the formation and/or function of both AP-1 and AP-3 transport vesicles. AP-1 vesicles assembled at the TGN are thought to be targeted to endosomal compartments (Deloche et al., 2001), such that impaired vesicle formation at the TGN would lead to defective delivery of vesicular transport components needed for endosomal trafficking. Therefore, the effects that we observe on endosomal function and movement of material from the plasma membrane to the vacuole may be indirect consequences of impaired TGN export. Consequently, we propose that the Gcs1 + Age2 ArfGAP pair mediates the formation and/or function of TGN-derived transport vesicles for both endosomal (CPY) and AP-3–dependent nonendosomal (ALP) pathways (Fig. 10).

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus