| Budget Amount *help |
¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000)
Fiscal Year 2010: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2009: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
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| Research Abstract |
Peroxisomes are ubiquitous single membrane-bound organelles that contain about 100 different enzymes catalyzing various metabolic pathways such as fatty-acid β-oxidation and etherglycerolipid synthesis. Peroxisomes are formed by growth and division of preexisting peroxisomes after posttranslational import of newly synthesized peroxisomal matrix and membrane proteins. Two distinct signals, peroxisomal targeting signal type 1 (PTS1) and PTS2, direct proteins to the peroxisomal matrix. PEX5 and PEX7 encode the cytosolic receptors for PTS1 and PTS2, respectively. However, functional regulation of Pex7p by ubiquitin remains undefined.
To address the regulation, if any, of Pex7p by ubiquitination, we first investigated whether or not Pex7p is ubiquitinated and degraded by proteasomes in cells. Addition of a proteasome inhibitor, MG132 to cell culture delayed Pex7p degradation. Alternatively, we also attempted to isolate any potential Pex7p-binding proteins involved in the degradation system of Pex7p. From a cell line stably expressing FLAG-Pex7p, we isolated several Pex7p-binding proteins, termed P7BPs : Pex7p binding proteins. Suppression of P7BP1 by RNAi resulted in a delay of Pex7p degradation, as observed in the MG132-treated cells, hence implying that P7BP1 plays a role in Pex7p ubiquitination.
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