title: Osh proteins regulate COPII-mediated vesicular transport of ceramide from the endoplasmic reticulum in budding yeast.
abstract: Lipids synthesized at the endoplasmic reticulum (ER) are delivered to the Golgi by vesicular and non-vesicular pathways. ER-to-Golgi transport is crucial for maintaining the different membrane lipid composition and identities of organelles. Despite their importance, mechanisms regulating transport remain elusive. Here we report that in yeast coat protein complex II (COPII) vesicle-mediated transport of ceramide from the ER to the Golgi requires oxysterol-binding protein homologs, Osh proteins, which have been implicated in lipid homeostasis. Because Osh proteins are not required to transport proteins to the Golgi, these results indicate a specific requirement for the Osh proteins in the transport of ceramide. In addition, we provide evidence that Osh proteins play a negative role in COPII vesicle biogenesis. Together, our data suggest that ceramide transport and sphingolipid levels between the ER and Golgi are maintained by two distinct functions of Osh proteins, which negatively regulate COPII vesicle formation and positively control a later stage, presumably fusion of ceramide-enriched vesicles with Golgi compartments.
authors.affiliation: Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Hiroshima 739-8528, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kajiwara
authors.forename: Atsuko
authors.initials: A
authors.lastname: Ikeda
authors.forename: Auxiliadora
authors.initials: A
authors.lastname: Aguilera-Romero
authors.forename: Guillaume A
authors.initials: GA
authors.lastname: Castillon
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kagiwada
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hanada
authors.forename: Howard
authors.initials: H
authors.lastname: Riezman
authors.forename: Manuel
authors.initials: M
authors.lastname: Muñiz
authors.forename: Kouichi
authors.initials: K
authors.lastname: Funato
mesh_terms: D001692:Biological Transport; D022181:COP-Coated Vesicles / Q000378:metabolism*; D002451:Cell Compartmentation; D002518:Ceramides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D017353:Gene Deletion; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D004718:Saccharomycetales / Q000166:cytology* / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism*
chemical_list: D002518:Ceramides; D029701:Saccharomyces cerevisiae Proteins
keywords: COPII; Ceramide; Oxysterol-binding protein; Vesicular transport; Yeast