title: Roles of copper chaperone for superoxide dismutase 1 and metallothionein in copper homeostasis.
abstract: Copper chaperone for SOD1 (CCS) specifically delivers copper (Cu) to copper, zinc superoxide dismutase (SOD1) in cytoplasm of mammalian cells. In the present study, small interfering RNA (siRNA) targeting CCS was introduced into metallothionein-knockout mouse fibroblasts (MT-KO cells) and their wild type cells (MT-WT cells) to reveal the interactive role of CCS with other Cu-regulating proteins, in particular, MT. CCS knockdown significantly decreased Ctr1, a Cu influx transporter, mRNA expression. On the other hand, Atp7a, a Cu efflux transporter, mRNA expression was increased 3.0 and 2.5 times higher than those of the control in MT-WT and MT-KO cells. These responses of Cu-regulating genes to the CCS knockdown reflected the presence of excess Cu in the cells. To evaluate the Atp7a function in the Cu-replete cells, siRNA of Atp7a and the other Cu transporter, Atp7b were introduced into MT-WT and MT-KO cells. The Atp7a knockdown significantly increased the intracellular Cu concentration, whereas the Atp7b knockdown had no affect. Although two MT isoforms were induced by the CCS knockdown in MT-WT cells, the expression and activity of SOD1 were maintained in both MT-WT and MT-KO cells even when CCS protein expression was reduced to 0.30-0.35 of control. This suggests that the amount of CCS protein exceeds that required to supply Cu to SOD1 in the cells. Further, the CCS knockdown induces Cu accumulation in cells, however, the Cu accumulation is ameliorated by the MT induction, the decrease of Ctr1 expression and the increase of Atp7a expression to maintain Cu homeostasis.
authors.affiliation: Laboratory of Chemical Toxicology and Environmental Health, Showa Pharmaceutical University, 3-3165 Higashi-Tamagawagakuen, Machida, Tokyo, Japan.
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Miyayama
authors.forename: Yudai
authors.initials: Y
authors.lastname: Ishizuka
authors.forename: Tomomi
authors.initials: T
authors.lastname: Iijima
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hiraoka
authors.forename: Yasumitsu
authors.initials: Y
authors.lastname: Ogra
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D000073840:Copper-Transporting ATPases; D055786:Gene Knockout Techniques; D020868:Gene Silencing; D006706:Homeostasis; D042541:Intracellular Space / Q000378:metabolism; D008668:Metallothionein / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D018832:Molecular Chaperones / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1
chemical_list: C486201:Atp7a protein, mouse; D027682:Cation Transport Proteins; C491962:Ccs protein, mouse; D018832:Molecular Chaperones; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D003300:Copper; D008668:Metallothionein; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D000251:Adenosine Triphosphatases; D000073840:Copper-Transporting ATPases