Endosidin1 defines a compartment involved in endocytosis of the brassinosteroid receptor BRI1 and the auxin transporters PIN2 and AUX1

Abstract

Although it is known that proteins are delivered to and recycled from the plasma membrane (PM) via endosomes, the nature of the compartments and pathways responsible for cargo and vesicle sorting and cellular signaling is poorly understood. To define and dissect specific recycling pathways, chemical effectors of proteins involved in vesicle trafficking, especially through endosomes, would be invaluable. Thus, we identified chemicals affecting essential steps in PM/endosome trafficking, using the intensely localized PM transport at the tips of germinating pollen tubes.

Isolation and proteomic analysis of the SYP61 compartment reveal its role in exocytic trafficking in Arabidopsis

“…AT1G09330-YFP formed punctate structures that were sensitive to brefeldin A (BFA) [61] and ES1 [17], and predominantly colocalized with SYP61-CFP ( Figure 5D-5I). TVP23p, the yeast homolog of AT1G09330, is localized to late Golgi compartments and interacts with Yip4 and Yip5 [62].…”

“…The same results were observed in SYP61/CESA6-YFP double-labeling experiments, confirming the role of SYP61 in the trafficking of CESA complexes to the PM. The analysis was extended to plants treated with endosidin 1 (ES1), a specific inhibitor of SYP61 trafficking [17], revealing that SYP61 and CESA6-YFP colocalize in ES1 bodies ( Figure 4C). This clearly demonstrates that CESA trafficking is TGN dependent.…”

“…Arabidopsis thaliana Col-0, wild-type plants and transgenic lines expressing SYP61-CFP [17], were grown in liquid MS medium for 14 days [64]. Golgi/TGN vesicles were isolated by gently grinding leaves in chilled vesicle isolation buffer (HEPES 50 mM, pH 7.5, 0.45 M sucrose, 5 mM MgCl2, 1 mM DTT, 0.5% PVP (P2307, Sigma) and protease inhibitors (Roche)) and by separating the Golgi/TGN as previously described [65].…”

“…SYP61 is a TGN-localized Q-SNARE and is part of a protein complex that includes VTI12 and SYP41 Q-SNAREs and other regulatory proteins such as VPS45 [15,16]. The SYP61 compartment appears to function as an EE for specific PM proteins [17]. The exact role of SYP61 is unclear, but it has been implicated in stress responses induced by abscisic acid [18], and it may be involved in trafficking of components to and from the prevacuolar compartment (PVC) [6,7,15,16,19].…”

MODIFIED VACUOLE PHENOTYPE1 Is an Arabidopsis Myrosinase-Associated Protein Involved in Endomembrane Protein Trafficking

“…For example, point mutations in the KATAMARI1/MURUS3 (KAM1/MUR3; Tamura et al, 2005) and KATAMARI2/GRAVITROPISM DEFECTIVE2 (KAM2/GRV2; Tamura et al, 2007;Silady et al, 2008) genes lead to disruption of endomembranes, resulting in the formation of perinuclear aggregates containing organelles. Nonlethal trafficking disruptions have also been generated using chemical genomics, where small molecules were used to perturb trafficking of a soluble cargo protein and localization of endomembrane markers (Surpin et al, 2005;Robert et al, 2008). Such studies have provided valuable clues about these essential cellular processes.…”