title: Diacidic motifs influence the export of transmembrane proteins from the endoplasmic reticulum in plant cells.
abstract: In yeast and mammals, amino acid motifs in the cytosolic tails of transmembrane domains play a role in protein trafficking by facilitating export from the endoplasmic reticulum (ER). However, little is known about ER export signals of membrane proteins in plants. Therefore, we investigated the role of diacidic motifs in the ER export of Golgi-localized membrane proteins. We show that diacidic motifs perform a significant function in the export of transmembrane proteins to the Golgi apparatus, as mutations of these signals impede the efficient anterograde transport of multispanning, type II, and type I proteins. Furthermore, we demonstrate that diacidic motifs instigate the export of proteins that reside in the ER due to the lengths of their transmembrane domains. However, not all of the diacidic motifs in the cytosolic tails of the proteins studied were equally important in ER export. Transport of Golgi proteins was disrupted only by mutagenesis of specific diacidic signals, suggesting that the protein environment of these signals affects their function. Our findings indicate that diacidic ER export motifs are present and functional in plant membrane proteins and that they are dominant over transmembrane domain length in determining the export of proteins from the ER in plant cells.
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon SK S7N 5E2, Saskatchewan, Canada.
authors.forename: Sally L
authors.initials: SL
authors.lastname: Hanton
authors.forename: Luciana
authors.initials: L
authors.lastname: Renna
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Bortolotti
authors.forename: Laurent
authors.initials: L
authors.lastname: Chatre
authors.forename: Giovanni
authors.initials: G
authors.lastname: Stefano
authors.forename: Federica
authors.initials: F
authors.lastname: Brandizzi
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000596:Amino Acids / Q000737:chemistry; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000737:chemistry / Q000378:metabolism*; D000077614:Golgi Matrix Proteins; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D059828:Plant Cells; D010940:Plant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; C504617:CASP protein, Arabidopsis; D002352:Carrier Proteins; C445096:GONST1 protein, Arabidopsis; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010940:Plant Proteins