Heat shock protein 90 regulates phosphatidylinositol 3-kinase-related protein kinase family proteins together with the RUVBL1/2 and Tel2-containing co-factor complex (original) (raw)
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Molecular & Cellular …, 2012
Despite the increasing importance of heat shock protein 90 (Hsp90) inhibitors as chemotherapeutic agents in diseases such as cancer, their global effects on the proteome remain largely unknown. Here we use high resolution, quantitative mass spectrometry to map protein expression changes associated with the application of the Hsp90 inhibitor, 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG). In depth data obtained from five replicate SILAC experiments enabled accurate quantification of about 6,000 proteins in HeLa cells. As expected, we observed activation of a heat shock response with induced expression of molecular chaperones, which refold misfolded proteins, and proteases, which degrade irreparably damaged polypeptides. Despite the broad range of known Hsp90 substrates, bioinformatics analysis revealed that particular protein classes were preferentially affected. These prominently included proteins involved in the DNA damage response, as well as protein kinases and especially tyrosine kinases. We followed up on this observation with a quantitative phosphoproteomic analysis of about 4,000 sites, which revealed that Hsp90 inhibition leads to much more down-than up-regulation of the phosphoproteome (34% down versus 6% up). This study defines the cellular response to Hsp90 inhibition at the proteome level and sheds light on the mechanisms by which it can be used to target cancer cells.
Proceedings of the National Academy of Sciences, 2012
The "apoptotic ring" is characterized by the phosphorylation of histone H2AX at serine 139 (γ-H2AX) by DNA-dependent protein kinase (DNA-PK). The γ-H2AX apoptotic ring differs from the nuclear foci patterns observed in response to DNA-damaging agents. It contains phosphorylated DNA damage response proteins including activated Chk2, activated ATM, and activated DNA-PK itself but lacks MDC1 and 53BP1, which are required to initiate DNA repair. Because DNA-PK can phosphorylate heat shock protein 90α (HSP90α) in biochemical assays, we investigated whether HSP90α is involved in the apoptotic ring. Here we show that HSP90α is phosphorylated by DNA-PK on threonines 5 and 7 early during apoptosis and that both phosphorylated HSP90α and DNA-PK colocalize in the apoptotic ring. We also show that DNA-PK is a client of HSP90α and that HSP90α is required for full DNA-PK activation, γ-H2AX formation, DNA fragmentation, and apoptotic body formation. In contrast, HSP90 inhibition by geldanamycin markedly enhances TRAIL-induced DNA-PK and H2AX activation. Together, our results reveal that HSP90α is a substrate and chaperone of DNA-PK in the apoptotic response. The response of phosphorylated HSP90α to TRAIL and its localization to the γ-H2AX ring represent epigenetic features of apoptosis that offer insights for studying and monitoring nuclear apoptosis.
Targeting of multiple signalling pathways by heat shock protein 90 molecular chaperone inhibitors
Endocrine Related Cancer, 2006
The last decade has seen the molecular chaperone heat shock protein 90 (HSP90) emerge as an exciting target for cancer therapy. This is because HSP90 is involved in maintaining the conformation, stability, activity and cellular localisation of several key oncogenic client proteins. These include, amongst others, ERBB2, C-RAF, CDK4, AKT/PKB, steroid hormone receptors, mutant p53, HIF-1a, survivin and telomerase hTERT. Therefore, modulation of this single drug target offers the prospect of simultaneously inhibiting all the multiple signalling pathways and biological processes that have been implicated in the development of the malignant phenotype. The chaperone function of HSP90 requires the formation of a multichaperone complex, which is dependent on the hydrolysis of ATP and ADP/ATP exchange. Most current inhibitors of HSP90 act as nucleotide mimetics, which block the intrinsic ATPase activity of this molecular chaperone. The first-in-class inhibitor to enter and complete phase I clinical trials was the geldanamycin analogue, 17-allylamino-17-demethoxygeldanamycin. The results of these trials have demonstrated that HSP90 is a valid drug target. Evidence of clinical activity has been seen in patients with melanoma, breast and prostate cancer. This article provides a personal perspective of the present efforts to increase our understanding of the molecular and cellular consequences of HSP90 inhibition, with examples from work in our own laboratory. We also review the discovery and development of novel small-molecule inhibitors and discuss alternative approaches to inhibit HSP90 activity, both of which offer exciting prospects for the future.
Molecular basis for the actions of Hsp90 inhibitors and cancer therapy
The Journal of Antibiotics, 2011
Heat-shock protein 90 (Hsp90) inhibitor downregulates c-Myc expression and upregulates the expression of tumor repressor proteins such as p53 and pRB, inhibiting the G1/S transition and causing G2/M arrest during cell cycle progression. The cycle progression is extensively controlled by the pRB/E2F signaling pathway. E2F is released from the pRB/E2F complex with the phosphorylation of pRB by cyclin-cyclin-dependent kinase (CDK) complexes. The released E2F promotes the transcription of target genes involved in cell cycle progression. The pRB/E2F signaling pathway is controlled by DNA methyltransferase-1 (Dnmt-1). The elevated expression of Dnmt-1 has been reported in carcinomas of the colon, lung and prostate. A defect of pRB expression in RbÀ/À cancer cells is caused by the aberrant methylation of CpG in the Rb promoter. The Hsp90 inhibitor disrupts the Dnmt-1/Hsp90 association and upregulates pRB expression. In this review, the Hsp90 inhibitors that show promise for cancer therapy are summarized.
Inhibition of Hsp90: a new strategy for inhibiting protein kinases
Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, 2004
The 90-kDa heat shock protein (Hsp90) is a ubiquitous, evolutionarily highly conserved, molecular chaperone in the eukaryotic cytosol. Hsp90, together with a number of other chaperones, promotes the conformational maturation of a large variety of protein kinases. Inhibition of Hsp90 function results in the collapse of the metastable conformation of most of these kinases and leads to their proteolytic elimination by the proteasome. Numerous natural and synthetic Hsp90 inhibitors have been developed in recent years. Some of these inhibitors are also involved in sensitizing tumor cells to pro-apoptotic insults, hence serve as anti-cancer drugs. Here we review these novel protein kinase inhibitors and their emerging role in various cellular processes, apart from their inhibition of Hsp90 protein function. We focus not only on Hsp90-tumor progression, but also on cytoarchitecture, as the higher levels of cellular organization need constant remodeling, where the role of Hsp90 requires investigation. Our last major aspect deals with protein oxidation, since several Hsp90 inhibitors exert pro-oxidant effects. D Abbreviations: 17AAG, 17-allylamino-17-demethoxy-geldanamycin; Cdk, cyclin-dependent kinase; CK II, CK refers to the old name of protein kinase CK II, casein kinase; EGF, epidermal growth factor; ER, endoplasmic reticulum; Grp94, 94-kDa glucose regulated protein, the endoplasmic reticulum homologue of Hsp90; HSF, heat shock factor; Hsp, heat shock protein; Hsp70, the 70-kDa heat shock protein; Hsp90, the 90-kDa heat shock protein; ILGF, insulin-like growth factor; MEK, mitogen activated protein kinase kinase; MOK, mitogen activated protein kinase; MAK, male germ cell associated kinase; NQQ1, NADH quinone oxidoreductase, DT-diaphorase; PDGF, platelet-derived growth factor; PKB, protein kinase B; PU3 and PU24F-Cl, purine-based Hsp90 inhibitors; RTK, receptor tyrosine kinase
The molecular chaperone Hsp90 is regulated by co-chaperones such as p50Cdc37, which recruits a wide selection of client protein kinases. Targeted disruption of the Hsp90-p50Cdc37 complex by protein–protein interaction (PPI) inhibitors has emerged as an alternative strategy to treat diseases characterized by aberrant Hsp90 activity. Using isothermal microcalorimetry, ELISA and GST-pull down assays we evaluated reported Hsp90 inhibitors and nucleotides for their ability to inhibit formation of the human Hsp90β-p50Cdc37 complex, reconstituted in vitro from full-length proteins. Hsp90 inhibitors, including the proposed PPI inhibitors gedunin and H2-gamendazole, did not affect the interaction of Hsp90 with p50Cdc37 in vitro. Phosphorylation of Hsp90 and p50Cdc37 by casein kinase 2 (CK2) did not alter the thermodynamic signature of complex formation. However, the phosphorylated complex was vulnerable to disruption by ADP (IC50 = 32 μM), while ATP, AMPPNP and Hsp90 inhibitors remained largely ineffective. The differential inhibitory activity of ADP suggests that phosphorylation by CK2 primes the complex for dissociation in response to a drop in ATP/ADP levels. The approach applied herein provides robust assays for a comprehensive biochemical evaluation of potential effectors of the Hsp90-p50Cdc37 complex, such as phosphorylation by a kinase or the interaction with small molecule ligands.
FBW7-dependent Mcl-1 degradation mediates the anticancer effect of Hsp90 inhibitors
Molecular cancer therapeutics, 2017
Heat shock protein 90 (Hsp90) is widely overexpressed in cancer cells and necessary for maintenance of malignant phenotypes. Hsp90 inhibition induces tumor cell death through degradation of its client oncoproteins, and has shown promises in preclinical studies. However, the mechanism by which Hsp90 inhibitors kill tumor cells is not well understood. Biomarkers associated with differential sensitivity and resistance to Hsp90 inhibitors remain to be identified. In this study, we found that colorectal cancer (CRC) cells containing inactivating mutations of FBW7, a tumor suppressor and E3 ubiquitin ligase, are intrinsically insensitive to Hsp90 inhibitors. The insensitive CRC cells lack degradation of Mcl-1, a pro-survival Bcl-2 family protein. Hsp90 inhibition promotes GSK3β-dependent phosphorylation of Mcl-1, which subsequently binds to FBW7 and undergoes ubiquitination and proteasomal degradation. Specifically blocking Mcl-1 phosphorylation by genetic knock-in abrogates its degradati...