Yokoyama Yuhei, Ohtaki Aguru, Jantan Ibrahim, Yohda Masafumi, Nakamoto Hitoshi
Molecular Biology Course, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan; Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia; and Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
Molecular Biology Course, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan; Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia; and Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan
J Biochem. 2015 Mar;157(3):161-8. doi: 10.1093/jb/mvu061. Epub 2014 Oct 7.
Hsp90 is an ATP-dependent molecular chaperone that is involved in important cellular pathways such as signal transduction pathways. It is a potential cancer drug target because it plays a critical role for stabilization and activation of oncoproteins. Thus, small molecule compounds that control the Hsp90 function are useful to elucidate potential lead compounds against cancer. We studied effect of a naturally occurring styryl-lactone goniothalamin on the activity of Hsp90. Although many drugs targeting Hsp90 inhibit the ATPase activity of Hsp90, goniothalamin enhanced rather than inhibited the ATPase activity of a cyanobacterial Hsp90 (HtpG) and a yeast Hsp90. It increased both K(m) and k(cat) of the Hsp90s. Domain competition assays and tryptophan fluorescence measurements with various truncated derivatives of HtpG indicated that goniothalamin binds to the N-terminal domain of HtpG. Goniothalamin did not influence on the interaction of HtpG with a non-native protein or the anti-aggregation activity of HtpG significantly. However, it inhibited the activity of HtpG that assists refolding of a non-native protein in cooperation with the Hsp70 chaperone system. This is the first report to show that a small molecule that binds to the N-terminal domain of Hsp90 activates its ATPase activity, while inhibiting the chaperone function of Hsp90.
热休克蛋白90（Hsp90）是一种依赖ATP的分子伴侣，参与信号转导途径等重要细胞通路。它是一种潜在的癌症药物靶点，因为它在癌蛋白的稳定和激活中起关键作用。因此，控制Hsp90功能的小分子化合物有助于阐明潜在的抗癌先导化合物。我们研究了天然存在的苯乙烯基内酯角鲨胺对Hsp90活性的影响。尽管许多靶向Hsp90的药物会抑制Hsp90的ATP酶活性，但角鲨胺增强而非抑制蓝藻Hsp90（HtpG）和酵母Hsp90的ATP酶活性。它增加了Hsp90的米氏常数（K(m)）和催化常数（k(cat)）。用HtpG的各种截短衍生物进行的结构域竞争试验和色氨酸荧光测量表明，角鲨胺与HtpG的N端结构域结合。角鲨胺对HtpG与非天然蛋白质的相互作用或HtpG的抗聚集活性没有显著影响。然而，它抑制了HtpG与Hsp70伴侣系统协同辅助非天然蛋白质重折叠的活性。这是首次报道一种与Hsp90的N端结构域结合的小分子激活其ATP酶活性，同时抑制Hsp90的伴侣功能。
