Molecular mechanisms of Sar/Arf GTPases in vesicular trafficking in yeast and plants

Abstract

Small GTPase proteins play essential roles in the regulation of vesicular trafficking systems in eukaryotic cells. Two types of small GTPases, secretion-associated Ras-related protein (Sar) and ADP-ribosylation factor (Arf), act in the biogenesis of transport vesicles. Sar/Arf GTPases function as molecular switches by cycling between active, GTP-bound and inactive, GDP-bound forms, catalyzed by guanine nucleotide exchange factors and GTPase-activating proteins, respectively. Activated Sar/Arf GTPases undergo a conformational change, exposing the N-terminal amphipathic α-helix for insertion into membranes. The process triggers the recruitment and assembly of coat proteins to the membranes, followed by coated vesicle formation and scission. In higher plants, Sar/Arf GTPases also play pivotal roles in maintaining the dynamic identity of organelles in the secretory pathway. Sar1 protein strictly controls anterograde transport from the endoplasmic reticulum (ER) through the recruitment of plant COPII coat components onto membranes. COPII vesicle transport is responsible for the organization of highly conserved polygonal ER networks. In contrast, Arf proteins contribute to the regulation of multiple trafficking routes, including transport through the Golgi complex and endocytic transport. These transport systems have diversified in the plant kingdom independently and exhibit several plant-specific features with respect to Golgi organization, endocytic cycling, cell polarity and cytokinesis. The functional diversification of vesicular trafficking systems ensures the multicellular development of higher plants. This review focuses on the current knowledge of Sar/Arf GTPases, highlighting the molecular details of GTPase regulation in vesicle formation in yeast and advances in knowledge of the characteristics of vesicle trafficking in plants.

Accumulation of phosphoinositides in distinct regions of the periarbuscular membrane

“…However, it should be noted that recent studies indicate that the PH FAPP1 probe has a second binding interface that binds a small GTPase ARF1, and mutagenesis of the binding site, plus the use of a second reporter entirely specific for PI4 P, confirmed that labeling of the Golgi is not indicative of a pool of PI4 P but rather the presence of high levels of a membrane‐bound form of ARF1 GTPase (He et al ., ; Simon et al ., ). ARF1 is a regulator of membrane trafficking and is present on the Golgi membranes when trafficking activity and transport vesicle formation are high (Beck et al ., ; Yorimitsu et al ., ). Therefore, localization of the PI4 P reporter to Golgi bodies reflects the state of activity of the Golgi bodies rather than the presence of PI4 P (He et al ., ; Simon et al ., ).…”

Robust gene expression changes in the ganglia following subclinical reactivation in rhesus macaques infected with simian varicella virus

“…Only 48 common DEGs were identified, most of which were down-regulated after both acute infection and reactivation. Several of these DEGs play a role in synaptic plasticity ( THRA , KIRREL and IGFS8 ) (Martin et al , 2015; Ray and Treloar, 2012; Vallortigara et al , 2009); neuronal growth ( MBP , STMN2 , PRPH and RHOG ) (Eriksson et al , 2008; Franke et al , 2012; Westerlund et al , 2011); and cell cycle such as ARF1 , HDLBP , and BOP1 (Molyneux et al , 2014; Strezoska et al , 2000; Yorimitsu et al , 2014). Although a limited number of DEGs were shared between these studies, both revealed a robust number of down-regulated genes that were involved in neuronal function, which suggests that both viral entry and viral reactivation cause neuronal damage but may affect different neuronal functions.…”

The ArfGAP protein MoGlo3 regulates the development and pathogenicity of Magnaporthe oryzae

“…In vesicle trafficking of eukaryotic cells, coatomer protein I (COPI) vesicles are required for retrograde traffic from the Golgi to the ER (Letourneur et al, 1994), while coatomer protein II (COPII) vesicles are involved in transport from the endoplasmic reticulum (ER) to the Golgi (Barlowe et al, 1994). The small G protein ADP-ribosylation factor (Arf1) plays a key role in the generation of COPI (D' Souza-Schorey and Chavrier, 2006;Yorimitsu et al, 2014). The function of Arf is regulated by guanine nucleotide exchange factors (ArfGEFs) and GTPase-activating proteins (ArfGAPs) (Tanigawa et al, 1993;Lewis et al, 2004;D'Souza-Schorey and Chavrier, 2006;Gillingham and Munro, 2007;Yorimitsu et al, 2014).…”