title: Dictyostelium discoideum RabS and Rab2 colocalize with the Golgi and contractile vacuole system and regulate osmoregulation.
abstract: Small-molecular-weight GTPase Rab2 has been shown to be a resident of pre-Golgi intermediates and is required for protein transport from the ER to the Golgi complex; however, Rab2 has yet to be characterized in Dictyostelium discoideum. DdRabS is a Dictyostelium Rab that is 80 percent homologous to DdRab1 which is required for protein transport between the ER and Golgi. Expression of GFP-tagged DdRab2 and DdRabS proteins showed localization to Golgi membranes and to the contractile vacuole system (CV) in Dictyostelium. Microscopic imaging indicates that the DdRab2 and DdRabS proteins localize at, and are essential for, the proper structure of Golgi membranes and the CV system. Dominant negative (DN) forms show fractionation of Golgi membranes, supporting their role in the structure and function of it. DdRab2 and DdRabS proteins, and their dominant negative and constitutively active (CA) forms, affect osmoregulation of the cells, possibly by the influx and discharge of fluids, which suggests a role in the function of the CV system. This is the first evidence of GTPases being localized to both Golgi membranes and the CV system in Dictyostelium.
authors.affiliation: Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Maringer
authors.forename: Azure
authors.initials: A
authors.lastname: Yarbrough
authors.forename: Sunder
authors.initials: S
authors.lastname: Sims-Lucas
authors.forename: Entsar
authors.initials: E
authors.lastname: Saheb
authors.forename: Sanaa
authors.initials: S
authors.lastname: Jawed
authors.forename: John
authors.initials: J
authors.lastname: Bush
mesh_terms: D000595:Amino Acid Sequence; D004023:Dictyostelium / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000235:genetics; D006056:Golgi Apparatus / Q000502:physiology; D049452:Green Fluorescent Proteins; D064587:Osmoregulation / Q000235:genetics*; D021381:Protein Transport / Q000235:genetics; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism; D020693:rab2 GTP-Binding Protein / Q000235:genetics*
chemical_list: D049452:Green Fluorescent Proteins; D020693:rab2 GTP-Binding Protein