Minami Michiko, Shinozaki Fumika, Suzuki Miho, Yoshimatsu Katsuhiko, Ichikawa Yoshimasa, Minami Yasufumi
Department of Natural and Environmental Science, Faculty of Education, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan.
Biochem Biophys Res Commun. 2006 Jun 16;344(4):1315-9. doi: 10.1016/j.bbrc.2006.04.050. Epub 2006 Apr 25.
We have previously shown that the proteasome activator PA28 is essential to Hsp90-dependent protein refolding in vitro, where PA28 mediates transfer of the Hsp90-bound substrate protein to the Hsc70/Hsp40 chaperone machine for its correct refolding. This observation suggests that PA28 may also collaborate with Hsp90 in cells. To examine this possibility, here we have used double-stranded RNA interference (RNAi) against PA28 in Caenorhabditis elegans mutants of daf-21, which encodes Hsp90. We show that C. elegans PA28 facilitates Hsp90-initiated protein refolding, albeit with an activity lower than that of mouse PA28 proteins. RNAi-mediated knockdown of PA28 significantly suppresses the Daf-c (dauer formation constitutive) phenotype of the daf-21 mutant, but it has no affect on the distinct defects of this mutant in sensing odorants. Taking these results together, we conclude that PA28 is likely to function in collaboration with Hsp90 in vivo.
我们之前已经表明，蛋白酶体激活剂PA28在体外对Hsp90依赖的蛋白质重折叠至关重要，其中PA28介导与Hsp90结合的底物蛋白转移至Hsc70/Hsp40伴侣机器以实现其正确重折叠。这一观察结果表明PA28在细胞中可能也与Hsp90协作。为检验这种可能性，我们在此利用双链RNA干扰（RNAi）技术，针对秀丽隐杆线虫中编码Hsp90的daf-21突变体的PA28进行研究。我们发现，秀丽隐杆线虫的PA28能促进Hsp90启动的蛋白质重折叠，尽管其活性低于小鼠PA28蛋白。RNAi介导的PA28敲低显著抑制了daf-21突变体的Daf-c（持续性 dauer形成）表型，但对该突变体在嗅觉感知方面的明显缺陷没有影响。综合这些结果，我们得出结论，PA28在体内可能与Hsp90协同发挥作用。
