title: Expression and characterization of Rab38, a new member of the Rab small G protein family.
abstract: Rab38 is a new member of the Rab small G protein family that regulates intracellular vesicle trafficking. Rab38 is expressed in melanocytes and it has been clarified that a point mutation in the postulated GTP-binding domain of Rab38 is the gene responsible for oculocutaneous albinism in chocolate mice. However, basic information regarding recombinant protein production, intracellular location, and tissue-specific expression pattern has not yet been reported. We produced recombinant Rab38 using a baculovirus/insect cell-protein expression system. A combination of Triton X-114 phase separation and nickel-affinity chromatography yielded exclusively prenylated Rab38 that bound [alpha-32P]-GTP. The mRNA and the native protein were expressed in a tissue-specific manner, e.g., in the lung, skin, stomach, liver, and kidney. Freshly isolated rat alveolar type II cells were highly positive for the mRNA signal, but the signal was rapidly lost over time. Immunofluorescence staining demonstrated that expressed GST-tagged Rab38 was mainly co-localized with endoplasmic reticulum-resident protein and also partly with intermittent vesicles between the endoplasmic reticulum and the Golgi complex. These results indicate that Rab38 is expressed non-ubiquitously in specific tissues and regulates early vesicle transport relating to the endoplasmic reticulum, and hence suggest that Rab38 abnormality may cause multiple organ diseases as well as oculocutaneous albinism.
authors.affiliation: Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Daigaku-Uchinada, Kahokugun, Ishikawa 920-0293, Japan. k-osanai@kanazawa-med.ac.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Osanai
authors.forename: Keiji
authors.initials: K
authors.lastname: Takahashi
authors.forename: Katsumi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Takahashi
authors.forename: Masanobu
authors.initials: M
authors.lastname: Ishigaki
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sakuma
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Toga
authors.forename: Tamio
authors.initials: T
authors.lastname: Suzuki
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Voelker
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D017368:Protein Prenylation; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D012867:Skin / Q000378:metabolism; D013047:Specific Pathogen-Free Organisms; D014162:Transfection; D020691:rab GTP-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D011994:Recombinant Proteins; C412058:RAB38 protein, human; C498787:Rab38 protein, rat; D020691:rab GTP-Binding Proteins