Hsp90 and co‐chaperones twist the functions of diverse client proteins

Zuehlke, Abbey D.; Johnson, Jill L.

doi:10.1002/bip.21292

Cited by 229 publications

(208 citation statements)

References 61 publications

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“…It has been reported in PubChem that CP9 inhibits proliferation, protein assembly, and kinase activities in different cancer cell lines. Because Hsp90 is involved in the regulation of kinases, receptors, and protein binding/folding, our data are consistent with others who have reported the downstream effects of CP9 (43).…”

Section: Cp9 As a 2-{[6-(trifluoromethyl)pyrimidin-2-yl]thio}acetamidsupporting

confidence: 93%

Discovery and validation of small-molecule heat-shock protein 90 inhibitors through multimodality molecular imaging in living subjects

Chan

Reeves

Geller³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Up-regulation of the folding machinery of the heat-shock protein 90 (Hsp90) chaperone protein is crucial for cancer progression. The two Hsp90 isoforms (α and β) play different roles in response to chemotherapy. To identify isoform-selective inhibitors of Hsp90 (α/β)/cochaperone p23 interactions, we developed a dual-luciferase (Renilla and Firefly) reporter system for high-throughput screening (HTS) and monitoring the efficacy of Hsp90 inhibitors in cell culture and live mice. HTS of a 30,176 small-molecule chemical library in cell culture identified a compound,, that binds to Hsp90(α/β) and displays characteristics of Hsp90 inhibitors, i.e., degradation of Hsp90 client proteins and inhibition of cell proliferation, glucose metabolism, and thymidine kinase activity, in multiple cancer cell lines. The efficacy of CP9 in disrupting Hsp90(α/β)/p23 interactions and cell proliferation in tumor xenografts was evaluated by non-invasive, repetitive Renilla luciferase and Firefly luciferase imaging, respectively. At 38 h posttreatment (80 mg/kg × 3, i.p.), CP9 led to selective disruption of Hsp90α/p23 as compared with Hsp90β/p23 interactions. Smallanimal PET/CT in the same cohort of mice showed that CP9 treatment (43 h) led to a 40% decrease in 18 F-fluorodeoxyglucose uptake in tumors relative to carrier control-treated mice. However, CP9 did not lead to significant degradation of Hsp90 client proteins in tumors. We performed a structural activity relationship study with 62 analogs of CP9 and identified A17 as the lead compound that outperformed CP9 in inhibiting Hsp90(α/β)/p23 interactions in cell culture. Our efforts demonstrated the power of coupling of HTS with multimodality molecular imaging and led to identification of Hsp90 inhibitors.drug development | small-molecule inhibitors | co-chaperone p23 | bioluminescence imaging | PET/computed tomography imaging

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Section: Cp9 As a 2-{[6-(trifluoromethyl)pyrimidin-2-yl]thio}acetamidsupporting

confidence: 93%

Discovery and validation of small-molecule heat-shock protein 90 inhibitors through multimodality molecular imaging in living subjects

Chan

Reeves

Geller³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Specificity of HSP90 action resides in part with the different cochaperones that associate with the HSP90 complex during the maturation cycle (27,60). This can be a complex process, with the order of entry and exit from the cycle being specific to the particular client protein, and in most cases the specific cochaperone (s) are unknown.…”

Section: Hsp90 Is Required For Proper Period Regulation Of the Circadmentioning

confidence: 99%

HSP90 functions in the circadian clock through stabilization of the client F-box protein ZEITLUPE

Kim

Fujiwara

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

111

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The autoregulatory loops of the circadian clock consist of feedback regulation of transcription/translation circuits but also require finely coordinated cytoplasmic and nuclear proteostasis. Although protein degradation is important to establish steady-state levels, maturation into their active conformation also factors into protein homeostasis. HSP90 facilitates the maturation of a wide range of client proteins, and studies in metazoan clocks implicate HSP90 as an integrator of input or output. Here we show that the Arabidopsis circadian clock-associated F-box protein ZEITLUPE (ZTL) is a unique client for cytoplasmic HSP90. The HSP90-specific inhibitor geldanamycin and RNAi-mediated depletion of cytoplasmic HSP90 reduces levels of ZTL and lengthens circadian period, consistent with ztl loss-of-function alleles. Transient transfection of artificial microRNA targeting cytoplasmic HSP90 genes similarly lengthens period. Proteolytic targets of SCF ZTL , TOC1 and PRR5, are stabilized in geldanamycin-treated seedlings, whereas the levels of closely related clock proteins, PRR3 and PRR7, are unchanged. An in vitro holdase assay, typically used to demonstrate chaperone activity, shows that ZTL can be effectively bound, and aggregation prevented, by HSP90. GIGANTEA, a unique stabilizer of ZTL, may act in the same pathway as HSP90, possibly linking these two proteins to a similar mechanism. Our findings establish maturation of ZTL by HSP90 as essential for proper function of the Arabidopsis circadian clock. Unlike metazoan systems, HSP90 functions here within the core oscillator. Additionally, F-box proteins as clients may place HSP90 in a unique and more central role in proteostasis.protein maturation | proteolysis T he circadian clock system sustains 24-h rhythmicity at the molecular and physiological level in most organisms that have been examined. A key function of the clock is to appropriately phase many essential physiological and biochemical processes in anticipation of the light/dark and temperature changes that occur each day. In both plants and animals impaired operation of the circadian clock results in reduced function and fitness, leading to increased propensity for disease and poor growth and reproductive success (1-5).The underlying basis of circadian clocks involves autoregulatory feedback loops that consist of positive activating and negative repressing elements that control gene transcription and protein activity and localization (6-8). The Arabidopsis circadian system consists of at least three interlocked feedback loops. Although more than 20 different genes are associated with circadian timing in plants, only a small subset has been incorporated into coherent interaction schemes (9, 10). Current models are based largely on transcriptional relationships, but increasingly posttranslational processes, such as regulated proteolysis, have been found to be critical for proper clock function (11-17). In Arabidopsis, the F-box protein ZEITLUPE (ZTL) is an eveningphased clock component responsible for the pro...

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“…19 In eukaryotes, co-chaperones modulate its intrinsic ATPase activity. 20,21 Post-translational modification of Hsp90 (e.g., phosphorylation, acetylation and S-nitrosylation) also impacts ATP and co-chaperone binding, [22][23][24] thus providing a further layer of regulation to the Hsp90 cycle not found in bacteria, a requirement no doubt made necessary by the increasingly complex utilization of Hsp90 in maintaining cellular homeostasis in the face of diverse environmental fluctuation.…”

Section: Tyrosine Phosphorylation Of Hsp90mentioning

confidence: 99%