Large ARF guanine nucleotide exchange factors in membrane trafficking

Abstract

In eukaryotic cells membrane compartments are connected through cargo-selective vesicle trafficking mediating the exchange of components between different organelles. This exchange is essential to maintain their structural integrity and specific composition. A fundamental regulatory step in vesicle formation is the activation of small ARF GTPases by exchanging their bound GDP for GTP, which is a prerequisite for ARF-mediated effector recruitment. Activation of ARFs is catalyzed by the characteristic SEC7 domain of guanine nucleotide exchange factors (ARF-GEFs), which are classified according to their additional protein domains.The only group of ARF-GEFs conserved in mammals, yeast and plants are the large ARF-GEFs. This review summarizes recent findings on the function of large ARF-GEFs, and the use of the inhibitor Brefeldin A as a potent tool in understanding membrane trafficking. Furthermore we highlight common themes and apparent differences in large ARF-GEF function between eukaryotic kingdoms.

Adventitious root formation in rice requires OsGNOM1 and is mediated by the OsPINs family

“…Arabidopsis GNOM1 is sensitive to BFA [18,21]. OsGNOM1 is a closer homolog to the Arabidopsis GNOM than to the six other rice GNOM proteins except Os02g22090 ( Figure 7C).…”

“…GNOM affects polar auxin transport (PAT) and development in Arabidopsis [15][16][17][18]. Over 20 allelic mutants of gnom have been identified [19][20][21]. Most of these mutants exhibited severe defects in both early embryonic structure and subsequent post-embryonic development such as LR formation and gravitropism, resulting in lethality [19,22,23].…”

“…Most of these mutants exhibited severe defects in both early embryonic structure and subsequent post-embryonic development such as LR formation and gravitropism, resulting in lethality [19,22,23]. GNOM is found in ORIGINAL ARTICLE www.cell-research.com | Cell Research Shiping Liu et al 1111 npg endosomal compartments and catalyzes guanine nucleotide exchange through its SEC7 domain, which is highly conserved among animals, plants and fungi [21,[24][25][26]. Except for GL1 in Arabidopsis, most large ARF-GEFs in plants (including GNOM) are predicted to be sensitive to the fungal toxin brefeldin A (BFA), a specific inhibitor of membrane protein trafficking [27,28].…”

Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p

“…Yeast cells contain five structurally related Sec7 domain-containing proteins with the potential to provide GEF activity for ARF family proteins involved in vesicular transport and actin remodeling (Casanova, 2007;Anders and Jurgens, 2008;Tsai et al, 2008). Sec7p, Gea1p, Gea2p and Syt1p have been shown to be Arf1/2 GEFs and Yel1p acts as an Arf3p-GEF (Jones et al, 1999;Gillingham and Munro, 2007a;Gillingham and Munro, 2007b).…”

BEX5/RabA1b Regulates trans-Golgi Network-to-Plasma Membrane Protein Trafficking in Arabidopsis

“…However, large protein families, including small GTPases (such as Rab GTPases and ARF GTPases) and ARF-GEF activators of ARF GTPases have been found as crucial regulators of vesicle trafficking (Zerial and McBride, 2001;Rutherford and Moore, 2002;Vernoud et al, 2003;Anders and Jürgens, 2008;Nielsen et al, 2008;Woollard and Moore, 2008). In yeast and mammals, every step in vesicle trafficking on secretory, endocytic, and recycling routes is regulated by members of Rab and ARF GTPases.…”