title: Truncated UDP-glucuronosyltransferase (UGT) from a Crigler-Najjar syndrome type II patient colocalizes with intact UGT in the endoplasmic reticulum.
abstract: Mutations in the gene encoding bilirubin UDP-glucuronosyltransferase (UGT1A1) are known to cause Crigler-Najjar syndrome type II (CN-II). We previously encountered a patient with a nonsense mutation (Q331X) on one allele and with no other mutations in the promoter region or other exons, and proposed that CN-II is inherited as a dominant trait due to the formation of a heterologous subunit structure comprised of the altered UGT1A1 gene product (UGT1A1-p.Q331X) and the intact UGT1A1. Here, we investigated the molecular basis of CN-II in this case by expressing UGT1A1-p.Q331X in cells. UGT1A1-p.Q331X overexpressed in Escherichia coli or mammalian cells directly bound or associated with intact UGT1A1 in vitro or in vivo, respectively. Intact UGT1A1 was observed as a dimer using atomic force microscopy. Fluorescent-tagged UGT1A1-p.Q331X and intact UGT1A1 were colocalized in 293T cells, and fluorescence recovery after photobleaching analysis showed that UGT1A1-p.Q331X was retained in the endoplasmic reticulum (ER) without rapid degradation. These findings support the idea that UGT1A1-p.Q331X and UGT1A1 form a dimer and provide an increased mechanistic understanding of CN-II.
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: Marie
authors.initials: M
authors.lastname: Hirata
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Takagi
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: Taiichi
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Iguchi
authors.affiliation: 1] Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan [2] Department of Biotechnology, Graduate School of Engineering, Nagoya University, Nagoya, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Koiwai
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: So
authors.initials: S
authors.lastname: Maezawa
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Koiwai
mesh_terms: D003414:Crigler-Najjar Syndrome / Q000201:enzymology* / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D014453:Glucuronosyltransferase / Q000737:chemistry / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D050505:Mutant Proteins / Q000378:metabolism*; D038761:Photobleaching; D011485:Protein Binding; D021381:Protein Transport; D013347:Subcellular Fractions / Q000378:metabolism; D000099148:UGT1A1 Enzyme
chemical_list: D014453:Glucuronosyltransferase; D049452:Green Fluorescent Proteins; D050505:Mutant Proteins; D000099148:UGT1A1 Enzyme; C485184:enhanced green fluorescent protein