Hsp90 visualized using SPC-104, tested on Bouin's fixed paraffin embedded backskin sections of transgenic mice. Courtesy of Dr. Turksen, Ottawa Hospital Research Institute, Canada.

Hsp90 is a highly conserved and essential stress protein that is expressed in all eukaryotic cells. From a functional perspective, hsp90 participates in the folding, assembly, maturation, and stabilization of specific proteins as an integral component of a chaperone complex (1-4). Despite its label of being a heat-shock protein, hsp90 is one of the most highly expressed proteins in unstressed cells (1–2% of cytosolic protein). It carries out a number of housekeeping functions – including controlling the activity, turnover, and trafficking of a variety of proteins. Most of the hsp90-regulated proteins that have been discovered to date are involved in cell signaling (5-6). The number of proteins now know to interact with Hsp90 is about 100. Target proteins include the kinases v-Src, Wee1, and c-Raf, transcriptional regulators such as p53 and steroid receptors, and the polymerases of the hepatitis B virus and telomerase.5. When bound to ATP, Hsp90 interacts with co-chaperones Cdc37, p23, and an assortment of immunophilin-like proteins, forming a complex that stabilizes and protects target proteins from proteasomal degradation.

In most cases, hsp90-interacting proteins have been shown to co-precipitate with hsp90 when carrying out immunoadsorption studies, and to exist in cytosolic heterocomplexes with it. In a number of cases, variations in hsp90 expression or hsp90 mutation has been shown to degrade signaling function via the protein or to impair a specific function of the protein (such as steroid binding, kinase activity) in vivo. Ansamycin antibiotics, such as geldanamycin and radicicol, inhibit hsp90 function (7).

1. Arlander S.J.H., et al. (2003) J Biol Chem 278: 52572-52577.
2. Pearl H., et al. (2001) Adv Protein Chem 59:157-186.
3. Neckers L., et al. (2002) Trends Mol Med 8:S55-S61.
4. Pratt W., Toft D. (2003) Exp Biol Med 228:111-133.
5. Pratt W., Toft D. (1997) Endocr Rev 18: 306–360.
6. Pratt W.B. (1998) Proc Soc Exptl Biol Med 217: 420–434.
7. Whitesell L., et al. (1994) Proc Natl Acad Sci USA 91: 8324– 8328.

近期发表文献
1. Wagatsuma, A. et al. (2011). Pharmacological inhibition of HSP90 activity negatively modulates myogenic differentiation and cell survival in C2C12 cells. Mol and Cel Biochem. 358 (1-2), 265-280.  doi: 10.1007/s11010-011-0977-0
 
2. Verheyen, A. et al. (2012). Systemic anti-vascular endothelial growth factor therapies induce a painful sensory neuropathy. Brain. 135 (9), 2629-2641. doi: 10.1093/brain/aws145

3. Zhang, S. et al. (2013). B Cell–Specific Deficiencies in mTOR Limit Humoral Immune Responses. Journal of Immunology. Published online. doi: 10.4049/jimmunol.1201767