title: Vacuolar degradation of two integral plasma membrane proteins, AtLRR84A and OsSCAMP1, is cargo ubiquitination-independent and prevacuolar compartment-mediated in plant cells.
abstract: In plant cells, how integral plasma membrane (PM) proteins are degraded in a cargo ubiquitination-independent manner remains elusive. Here, we studied the degradative pathway of two plant PM proteins: AtLRR84A, a type I integral membrane protein belonging to the leucine-rich repeat receptor-like kinase protein family, and OsSCAMP1 (rice secretory carrier membrane protein 1), a tetraspan transmembrane protein located on the PM and trans-Golgi network (TGN) or early endosome (EE). Using wortmannin and ARA7(Q69L) mutant that could enlarge the multivesicular body (MVB) or prevacuolar compartment (PVC) as tools, we demonstrated that, when expressed as green fluorescent protein (GFP) fusions in tobacco BY-2 or Arabidopsis protoplasts, both AtLRR84A and OsSCAMP1 were degraded in the lytic vacuole via the internal vesicles of MVB/PVC in a cargo ubiquitination-independent manner. Such MVB/PVC-mediated vacuolar degradation of PM proteins was further supported by immunocytochemical electron microscopy (immunoEM) study showing the labeling of the fusions on the internal vesicles of the PVC/MVB. Thus, cargo ubiquitination-independent and PVC-mediated degradation of PM proteins in the vacuole is functionally operated in plant cells.
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Cai
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhuang
authors.forename: Junqi
authors.initials: J
authors.lastname: Wang
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Sheung Kwan
authors.initials: SK
authors.lastname: Lam
authors.forename: Caiji
authors.initials: C
authors.lastname: Gao
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Wang
authors.forename: Liwen
authors.initials: L
authors.lastname: Jiang
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics; D002459:Cell Fusion; D002460:Cell Line; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism*; D057146:Multivesicular Bodies / Q000378:metabolism; D012275:Oryza; D010940:Plant Proteins / Q000187:drug effects / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D059748:Proteolysis; D014026:Nicotiana / Q000235:genetics; D054875:Ubiquitination; D014617:Vacuoles / Q000378:metabolism*; D000077191:Wortmannin; D020691:rab GTP-Binding Proteins / Q000235:genetics; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: D000730:Androstadienes; D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D010940:Plant Proteins; D047428:Protein Kinase Inhibitors; C495672:Ara7 protein, Arabidopsis; D020691:rab GTP-Binding Proteins; D000077191:Wortmannin