title: Trans-Golgi network-located AP1 gamma adaptins mediate dileucine motif-directed vacuolar targeting in Arabidopsis.
abstract: Membrane proteins on the tonoplast are indispensible for vacuolar functions in plants. However, how these proteins are transported to the vacuole and how they become separated from plasma membrane proteins remain largely unknown. In this study, we used Arabidopsis thaliana vacuolar ion transporter1 (VIT1) as a reporter to study the mechanisms of tonoplast targeting. We showed that VIT1 reached the tonoplast through a pathway involving the endoplasmic reticulum (ER), Golgi, trans-Golgi network (TGN), prevacuolar compartment, and tonoplast. VIT1 contains a putative N-terminal dihydrophobic type ER export signal, and its N terminus has a conserved dileucine motif (EKQTLL), which is responsible for tonoplast targeting. In vitro peptide binding assays with synthetic VIT1 N terminus identified adaptor protein complex-1 (AP1) subunits that interacted with the dileucine motif. A deficiency of AP1 gamma adaptins in Arabidopsis cells caused relocation of tonoplast proteins containing the dileucine motif, such as VIT1 and inositol transporter1, to the plasma membrane. The dileucine motif also effectively rerouted the plasma membrane protein SCAMP1 to the tonoplast. Together with subcellular localization studies showing that AP1 gamma adaptins localize to the TGN, we propose that the AP1 complex on the TGN mediates tonoplast targeting of membrane proteins with the dileucine motif.
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Cai
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Yonglun
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhuang
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Baiying
authors.initials: B
authors.lastname: Li
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China ljiang@cuhk.edu.hk.
authors.forename: Liwen
authors.identifier: http://orcid.org/0000-0002-2480-8210
authors.initials: L
authors.lastname: Jiang
mesh_terms: D033982:Adaptor Protein Complex gamma Subunits / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009154:Mutation; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D021381:Protein Transport; D011523:Protoplasts / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: D033982:Adaptor Protein Complex gamma Subunits; D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D009842:Oligopeptides; D010455:Peptides; C515257:VIT1 protein, Arabidopsis; D007930:Leucine