title: Five Arabidopsis reticulon isoforms share endoplasmic reticulum location, topology, and membrane-shaping properties.
abstract: The cortical endoplasmic reticulum (ER) in tobacco (Nicotiana tabacum) epidermal cells is a network of tubules and cisternae undergoing dramatic rearrangements. Reticulons are integral membrane proteins involved in shaping ER tubules. Here, we characterized the localization, topology, effect, and interactions of five Arabidopsis thaliana reticulons (RTNs), isoforms 1-4 and 13, in the cortical ER. Our results indicate that RTNLB13 and RTNLB1-4 colocate to and constrict the tubular ER membrane. All five RTNs preferentially accumulate on ER tubules and are excluded from ER cisternae. All isoforms share the same transmembrane topology, with N and C termini facing the cytosol and four transmembrane domains. We show by Förster resonance energy transfer and fluorescence lifetime imaging microscopy that several RTNs have the capacity to interact with themselves and each other, and we suggest that oligomerization is responsible for their residence in the ER membrane. We also show that a complete reticulon homology domain is required for both RTN residence in high-curvature ER membranes and ER tubule constriction, yet it is not necessary for homotypic interactions.
authors.affiliation: School of Life Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom.
authors.forename: Imogen
authors.initials: I
authors.lastname: Sparkes
authors.forename: Nicholas
authors.initials: N
authors.lastname: Tolley
authors.forename: Isabel
authors.initials: I
authors.lastname: Aller
authors.forename: Julia
authors.initials: J
authors.lastname: Svozil
authors.forename: Anne
authors.initials: A
authors.lastname: Osterrieder
authors.forename: Stanley
authors.initials: S
authors.lastname: Botchway
authors.forename: Christopher
authors.initials: C
authors.lastname: Mueller
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Frigerio
authors.forename: Chris
authors.initials: C
authors.lastname: Hawes
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D017433:Protein Structure, Secondary; D018749:RNA, Plant / Q000235:genetics; D014026:Nicotiana / Q000737:chemistry / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D020033:Protein Isoforms; D018749:RNA, Plant