title: Functional identification of sorting receptors involved in trafficking of soluble lytic vacuolar proteins in vegetative cells of Arabidopsis.
abstract: In eukaryotic cells, protein trafficking plays an essential role in biogenesis of proteins that belong to the endomembrane compartments. In this process, an important step is the sorting of organellar proteins depending on their final destinations. For vacuolar proteins, vacuolar sorting receptors (VSRs) and receptor homology-transmembrane-RING H2 domain proteins (RMRs) are thought to be responsible. Arabidopsis (Arabidopsis thaliana) contains seven VSRs. Among them, VSR1, VSR3, and VSR4 are involved in sorting storage proteins targeted to the protein storage vacuole (PSV) in seeds. However, the identity of VSRs for soluble proteins of the lytic vacuole in vegetative cells remains controversial. Here, we provide evidence that VSR1, VSR3, and VSR4 are involved in sorting soluble lytic vacuolar and PSV proteins in vegetative cells. In protoplasts from leaf tissues of vsr1vsr3 and vsr1vsr4 but not vsr5vsr6, and rmr1rmr2 and rmr3rmr4 double mutants, soluble lytic vacuolar (Arabidopsis aleurain-like protein:green fluorescent protein [GFP] and carboxypeptidase Y:GFP and PSV (phaseolin) proteins, but not the vacuolar membrane protein Arabidopsis βFructosidase4:GFP, exhibited defects in their trafficking; they accumulated to the endoplasmic reticulum with an increased secretion into medium. The trafficking defects in vsr1vsr4 protoplasts were rescued by VSR1 or VSR4 but not VSR5 or AtRMR1. Furthermore, of the luminal domain swapping mutants between VSR1 and VSR5, the mutant with the luminal domain of VSR1, but not that of VSR5, rescued the trafficking defects of Arabidopsis aleurain-like protein:GFP and phaseolin in vsr1vsr4 protoplasts. Based on these results, we propose that VSR1, VSR3, and VSR4, but not other VSRs, are involved in sorting soluble lytic vacuolar and PSV proteins for their trafficking to the vacuoles in vegetative cells.
authors.affiliation: Division of Integrative Biosciences , Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Yongjik
authors.initials: Y
authors.lastname: Lee
authors.forename: Mihue
authors.initials: M
authors.lastname: Jang
authors.forename: Kyungyoung
authors.initials: K
authors.lastname: Song
authors.forename: Hyangju
authors.initials: H
authors.lastname: Kang
authors.forename: Myoung Hui
authors.initials: MH
authors.lastname: Lee
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Lee
authors.forename: Jan
authors.initials: J
authors.lastname: Zouhar
authors.forename: Enrique
authors.initials: E
authors.lastname: Rojo
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Sohn
authors.forename: Inhwan
authors.initials: I
authors.lastname: Hwang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D059828:Plant Cells / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D012995:Solubility; D014170:Transformation, Genetic; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C106564:ELP protein, Arabidopsis; D008565:Membrane Proteins; C505135:RMR1 protein, Arabidopsis; D018160:Receptors, Cytoplasmic and Nuclear; C529649:VSR3 protein, Arabidopsis; D049452:Green Fluorescent Proteins