| Budget Amount *help |
¥12,700,000 (Direct Cost: ¥12,700,000)
Fiscal Year 1999: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1998: ¥10,200,000 (Direct Cost: ¥10,200,000)
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| Research Abstract |
(1) Folding of proteins in the ER involves oxidation of cystein. To elucidate the mechanism of oxidation, we have developed a novel experimental system which selectively labels cysteins forming disulfide bonds of newly synthesized transferrin. By using this methbd, we found that oxidation of the ER lumen appeared to proceeds unevenly and newly synthesized transferrin was rather selectively oxidized. Analysis of the process, which was inhibited by two specific chemicals, revealed two distinctive mechanisms ; one which is responsible for cotranslational oxidation and the other for posttranslational.
(2) We demonstrated that proper folding of tyrosinase depends on calnexin. It is known that mutations of this enzyme is responsible for OCA1. We next reported that they were immediately degraded upon release from canlexin by proteasome.
(3) It has been shown that degradation of misfolded proteins in the ER by proteasome requires mannose trimming, particularly from Man9 structures to Man8. By searching novel molecules which are induced by stress, we reported EDEM which has homologous to a-mannosidase but lacks the enzymatic activity. EDEM bound to misfolded antitrypsin and its degradation was accelerated by overexpressing EDEM, indicating that EDEM may be an acceptor for misfolded proteins in the ER.
(4) We previously reported that sperm in calmegin KO-mouse were unable to bind to egs. In this study, we identified that heterooligomerazation of a cell surface molecule is impaired in the KO mouse, suggesting that calmegin, a testis isoform of calnexin, is required for assembly of a specific cell surface receptor.
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