| Budget Amount *help |
¥4,060,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
We have identified a novel member of CREB/ATF family and named it OASIS. OASIS has a transmembrane domain in addition to a bZIP domain, reminiscent of another family member ATF6. Via this transmembrane domain, OASIS is localized to the endoplasmic reticulum (ER). Our previous study showed that OASIS is specifically expressed by astrocytes in the brain. Since ATF6 has been implicated in the stress responses, we assumed that OASIS is also involved in some kind of stress responses.
In the present study, we first tested whether OASIS is liberated from ER membrane by proteolytic cleavage. We employed cultured astrocytes for this analysis, because OASIS is endogenously expressed in the cell. First if all, we applied ER stress to astrocytes by treating them with tunicamicin or thapsigargin. Under this condition, OASIS protein has smaller molecular weight than the control condition. This suggested that OASIS received regulated intramembrene proteolysis. When we knocked down the membrane-associated protease, Si protease, by siRNA, the cleavage of the OASIS protein was inhibited. In the case of 52 protease knockdown, the cleavage was also blocked. These result suggested that Si and S2 proteases are both involved in the liberation of OASIS N-terminal fragment. These two proteases are known to reside in the Golgi apparatus. So we checked subcellular localization of OASIS protein in the ER stress condition. Unlike the normal state, OASIS protein was translocated to the Golgi apparatus. Mutation of intraluminal domain of the OASIS protein did not affect the translocation to the Golgi apparatus, suggesting that Golgi translocation was promoted by the mechanisms other than the ordinary Golgi targeting signals, which ATF6 utilizes.
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