HSP70 Inhibition by the Small-Molecule 2-Phenylethynesulfonamide Impairs Protein Clearance Pathways in Tumor Cells

Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Molecular Cancer Research (Impact Factor: 4.5). 06/2011; 9(7):936-47. DOI: 10.1158/1541-7786.MCR-11-0019
Source: PubMed

ABSTRACT The evolutionarily conserved stress-inducible HSP70 molecular chaperone plays a central role in maintaining protein quality control in response to various forms of stress. Constitutively elevated HSP70 expression is a characteristic of many tumor cells and contributes to their survival. We recently identified the small-molecule 2-phenylethyenesulfonamide (PES) as a novel HSP70 inhibitor. Here, we present evidence that PES-mediated inhibition of HSP70 family proteins in tumor cells results in an impairment of the two major protein degradation systems, namely, the autophagy-lysosome system and the proteasome pathway. HSP70 family proteins work closely with the HSP90 molecular chaperone to maintain the stability and activities of their many client proteins, and PES causes a disruption in the HSP70/HSP90 chaperone system. As a consequence, many cellular proteins, including known HSP70/HSP90 substrates, accumulate in detergent-insoluble cell fractions, indicative of aggregation and functional inactivation. Overall, PES simultaneously disrupts several cancer critical survival pathways, supporting the idea of targeting HSP70 as a potential approach for cancer therapeutics.

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    • "PES is a small molecule with chemical traits for being a highly reactive and oxidant agent (Fig. 3A). A characterization of its mode of action revealed its ability to block HSP70 function in vivo and as a consequence: i) the secondary inhibition of HSP90 and the proteasome; ii) the blockage of the chaperone-mediated type of autophagy, which results from HSC70 inhibition; iii) the impairment of the completion of macroautophagy (named autophagy hereafter) [12] [34]. "
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    Current Drug Targets 11/2014; 16(1). DOI:10.2174/1389450115666141114153536 · 3.60 Impact Factor
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    • "Anti-actin antibody was used as a loading control. morphologies (Leu et al., 2011; Steele et al., 2009). The EC 50 s or IC 50 s varied with the cell source. "
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    ABSTRACT: The effect of 2-phenylethynesulfonamide (PES), which is a p53 and HSP70 inhibitor in mammalian cells, was studied on the rainbow trout (Oncorhynchus mykiss) gill epithelial cell line, RTgill-W1, in order to evaluate PES as a tool for understanding the cellular survival pathways operating in fish. As judged by three viability assays, fish cells were killed by 24h exposures to PES, but cell death was blocked by the anti-oxidant N-acetylcysteine (NAC). Cell death had several hallmarks of apoptosis: DNA laddering, nuclear fragmentation, Annexin V staining, mitochondrial membrane potential decline, and caspases activation. Reactive oxygen species (ROS) production peaked in several hours after the addition of PES and before cell death. HSP70 and BiP levels were higher in cultures treated with PES for 24h, but this was blocked by NAC. As well, PES treatment caused HSP70, BiP and p53 to accumulate in the detergent-insoluble fraction, and this too was prevented by NAC. Of several possible scenarios to explain the results, the following one is the simplest. PES enhances the generation of ROS, possibly by inhibiting the anti-oxidant actions of p53 and HSP70. ER stress arises from the ROS and from PES inhibiting the chaperone activities of HSP70. The ER stress in turn initiates the unfolded protein response (UPR), but this fails to restore ER homeostasis so proteins aggregate and cells die. Despite these multiple actions, PES should be useful for studying fish cellular survival pathways.
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    • "Unfortunately, in vivo, VER-155008 is rapidly eliminated, and its level in tumor never reaches the predicted pharmacologically active level. Another study recently identified the small molecule 2-phenyle- thyenesulfonamide (PES) as a novel Hsp70 inhibitor (Leu et al. 2011). In tumor cells, this drug disrupts the Hsp70/ Hsp90 chaperone machines and impairs the autophagylysosome system and the proteasome pathway. "
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