title: Differential degradation of PIN2 auxin efflux carrier by retromer-dependent vacuolar targeting.
abstract: All eukaryotic cells present at the cell surface a specific set of plasma membrane proteins that modulate responses to internal and external cues and whose activity is also regulated by protein degradation. We characterized the lytic vacuole-dependent degradation of membrane proteins in Arabidopsis thaliana by means of in vivo visualization of vacuolar targeting combined with quantitative protein analysis. We show that the vacuolar targeting pathway is used by multiple cargos including PIN-FORMED (PIN) efflux carriers for the phytohormone auxin. In vivo visualization of PIN2 vacuolar targeting revealed its differential degradation in response to environmental signals, such as gravity. In contrast to polar PIN delivery to the basal plasma membrane, which depends on the vesicle trafficking regulator ARF-GEF GNOM, PIN sorting to the lytic vacuolar pathway requires additional brefeldin A-sensitive ARF-GEF activity. Furthermore, we identified putative retromer components SORTING NEXIN1 (SNX1) and VACUOLAR PROTEIN SORTING29 (VPS29) as important factors in this pathway and propose that the retromer complex acts to retrieve PIN proteins from a late/pre-vacuolar compartment back to the recycling pathways. Our data suggest that ARF GEF- and retromer-dependent processes regulate PIN sorting to the vacuole in an antagonistic manner and illustrate instrumentalization of this mechanism for fine-tuning the auxin fluxes during gravitropic response.
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology, Technologiepark 927, 9052 Ghent, Belgium.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Johannes
authors.initials: J
authors.lastname: Leitner
authors.forename: Marta
authors.initials: M
authors.lastname: Zwiewka
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.forename: Lindy
authors.initials: L
authors.lastname: Abas
authors.forename: Christian
authors.initials: C
authors.lastname: Luschnig
authors.forename: Jirí
authors.initials: J
authors.lastname: Friml
mesh_terms: D020727:ADP-Ribosylation Factors / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018522:Gravitropism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010716:Phosphatidylinositols / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D013997:Time Factors; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D020727:ADP-Ribosylation Factors; D029681:Arabidopsis Proteins; D020662:Guanine Nucleotide Exchange Factors; D007210:Indoleacetic Acids; D010716:Phosphatidylinositols; D033921:Vesicular Transport Proteins; C515611:Mag1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis