Shinozaki Fumika, Minami Michiko, Chiba Tomoki, Suzuki Miho, Yoshimatsu Katsuhiko, Ichikawa Yoshimasa, Terasawa Kazuya, Emori Yasufumi, Matsumoto Ken, Kurosaki Tomohiro, Nakai Akira, Tanaka Keiji, Minami Yasufumi
Department of Biophysics and Biochemistry, and Undergraduate Program for Bioinformatics and Systems Biology, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Biol Chem. 2006 Jun 16;281(24):16361-9. doi: 10.1074/jbc.M600891200. Epub 2006 Apr 14.
Hsp90 participates in many distinct aspects of cellular functions and accomplishes these roles by interacting with multiple client proteins. To gain insight into the interactions between Hsp90 and its clients, here we have reduced the protein level of Hsp90 in avian cells by gene targeting in an attempt to elicit the otherwise undetectable (because of the vast amount of cellular Hsp90) Hsp90-interacting proteins. Hsp90beta-deficient cells can grow, albeit more slowly than wild-type cells. B cell antigen receptor signaling is multiply impaired in these mutant cells; in particular, the amount of immunoglobulin M heavy chain protein is markedly reduced. Furthermore, serum activation does not promote ERK phosphorylation in Hsp90beta-deficient cells. These multifaceted depressive effects seem to be provoked independently of each other and possibly recapitulate the proteome-wide in vivo functions of Hsp90. Reintroduction of the Hsp90beta gene efficiently restores all of the defects. Unexpectedly, however, introducing the Hsp90alpha gene is also effective in restoration; thus, these defects might be caused by a reduction in the total expression of Hsp90 rather than by loss of Hsp90beta-specific function.
热休克蛋白90（Hsp90）参与细胞功能的许多不同方面，并通过与多种客户蛋白相互作用来完成这些作用。为了深入了解Hsp90与其客户蛋白之间的相互作用，我们在此通过基因靶向降低了禽类细胞中Hsp90的蛋白水平，试图找出那些原本因细胞中大量Hsp90而无法检测到的与Hsp90相互作用的蛋白。Hsp90β缺陷型细胞能够生长，尽管比野生型细胞生长得更慢。在这些突变细胞中，B细胞抗原受体信号传导存在多重缺陷；特别是，免疫球蛋白M重链蛋白的量显著减少。此外，血清激活在Hsp90β缺陷型细胞中不会促进细胞外信号调节激酶（ERK）的磷酸化。这些多方面的抑制作用似乎彼此独立引发，并且可能概括了Hsp90在全蛋白质组范围内的体内功能。重新引入Hsp90β基因可有效恢复所有缺陷。然而，出乎意料的是，引入Hsp90α基因在恢复方面也有效；因此，这些缺陷可能是由Hsp90总表达量的降低而非Hsp90β特异性功能的丧失所引起的。
