title: Posttranslational regulation of Abcc2 expression by SUMOylation system.
abstract: The ATP-binding cassette transporter family C 2 (Abcc2) is a member of efflux transporters involved in the biliary excretion of organic anions from hepatocytes. Posttranslational regulation of Abcc2 has been implicated, although the molecular mechanism is not fully understood. In the present study, we performed yeast two-hybrid screening to identify novel protein(s) that particularly interacts with the linker region of Abcc2 located between the NH(2)-terminal nucleotide binding domain and the last membrane-spanning domain. The screening resulted in the identification of a series of small ubiquitin-like modifier (SUMO)-related enzymes and their substrates. In yeast experiments, all of these interactions were abolished by substituting the putative SUMO consensus site in the linker region (IKKE) in Abcc2 to IRKE. In vitro SUMOylation experiments confirmed that the Abcc2 linker was a substrate of Ubc9-mediated SUMOylation. It was also found that the IKKE sequence is the target of SUMOylation, since a mutant with IKKE is substituted by IRKE was not SUMOylated. Furthermore, we demonstrated for the first time that Abcc2, endogenously expressed in rat hepatoma-derived McARH7777 cells, is SUMOylated. Suppression of endogenous Ubc9 by small interfering RNA resulted in a selective 30% reduction in Abcc2 protein expression in the postnuclear supernatant, whereas subcellular localization of Abcc2 confirmed by semiquantitative immunofluorescence analysis was minimally affected. This is the first demonstration showing the regulation of ABC transporter expression by SUMOylation.
authors.affiliation: Department of Pharmacy, The University of Tokyo Hospital, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Minami
authors.forename: Kousei
authors.initials: K
authors.lastname: Ito
authors.forename: Masashi
authors.initials: M
authors.lastname: Honma
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ikebuchi
authors.forename: Naohiko
authors.initials: N
authors.lastname: Anzai
authors.forename: Yoshikatsu
authors.initials: Y
authors.lastname: Kanai
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Nishida
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tsukita
authors.forename: Shuichi
authors.initials: S
authors.lastname: Sekine
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Horie
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D025842:SUMO-1 Protein / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D020798:Two-Hybrid System Techniques; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D018528:ATP-Binding Cassette Transporters; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D025842:SUMO-1 Protein; D044763:Ubiquitin-Conjugating Enzymes; D000098843:Ubiquitin-Conjugating Enzyme UBC9; C000715087:ABCC2 protein, human; C423013:Abcc2 protein, rat