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Unique integrated stress response sensors regulate cancer cell susceptibility when Hsp70 activity is compromised

ABSTRACT: Molecular chaperones prevent the accumulation of toxic proteins in the cell, but when chaperones are overwhelmed, the rapid modulation of proteostasis pathways provide corrective responses. One molecular chaperone in particular, Hsp70, plays a central role in both cellular protection and the response to proteotoxic insults. This is perhaps most evident in cancer cells, some of which overexpress Hsp70 and thrive even when harboring high levels of misfolded, aggregated, and/or unassembled protein complexes. In an effort to define how cells compensate for compromised proteostasis, we examined the adaptive response in breast cancer cells after challenge with a specific Hsp70 inhibitor, MAL3-101 and further define the pathways involved in the differential MAL3-101 response between sensitive and resistant cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE178352 | GEO | 2021/07/01

REPOSITORIES: GEO

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Allosteric HSP70 inhibitors perturb mitochondrial proteostasis and overcome proteasome inhibitor resistance in multiple myeloma

Project description:Proteasome inhibitor (PI) resistance remains a central challenge in multiple myeloma. To identify pathways mediating resistance, we first map proteasome-associated genetic co-dependencies. We identify cytosolic heat shock protein 70 (HSP70) chaperones as a potential target, consistent with proposed mechanisms of myeloma tumor cells overcoming PI-induced stress. These results led us to explore allosteric HSP70 inhibitors as myeloma therapeutics. We show these compounds exhibit increased efficacy against both acquired and intrinsic PI-resistant myeloma models, unlike HSP90 inhibition. Surprisingly, shotgun and pulsed-SILAC proteomics reveal that JG’s overcome PI resistance not via the expected mechanism of inhibiting cytosolic HSP70s, but instead through mitochondrial-localized HSP70, HSPA9, destabilizing the 55S mitoribosome. Analysis of myeloma patient data further supports strong effects of global proteostasis capacity, and particularly HSPA9 expression, on PI response. Our results characterize dynamics of myeloma proteostasis networks under therapeutic pressure while further motivating investigation of HSPA9 as a specific target in PI-resistant disease.

2020-04-15 | GSE148659 | GEO

Hsp70 ATP-dependent dimerization and Chaperone/Co-chaperone Interactions

Project description:Eukaryotic protein homeostasis (proteostasis) is largely dependent on the action of highly conserved Hsp70 molecular chaperones. Recent evidence indicates that apart from conserved molecular allostery, Hsp70 proteins retained and adapted throughout the evolution the ability to assemble as functionally relevant ATP-bound dimers. Here we have compared the ATP-dependent dimerization of DnaK, human stress-inducible Hsp70, Hsc70 and BiP Hsp70 proteins showing that their dimerization propensities differ with stress-inducible Hsp70 being predominantly dimeric in the presence of ATP. The structural analyses using hydrogen/deuterium exchange mass spectrometry, native electrospray ionization mass spectrometry, chemical cross-linking and small-angle X-ray scattering revealed that stress-inducible Hsp70 assembles in solution as an antiparallel dimer with the intermolecular interface closely resembling the ATP-bound dimer interfaces captured in DnaK and BiP crystal structures. ATP-dependent dimerization of stress-inducible Hsp70 is necessary for its efficient interaction with Hsp40 as shown by experiments with dimerization-deficient mutants. Moreover, dimerization of ATP-bound Hsp70 is required for its participation in high molecular weight protein complexes detected ex vivo supporting its functional role in vivo. As human cytosolic Hsp70 has the ability to interact with tetratricopeptide repeat (TPR) domain containing co-chaperones, we tested the interaction of Hsp70 ATP-dependent dimer with Chip and Tomm34 co-chaperones. While Chip associates with intact Hsp70 dimer to form a larger complex, binding of Tomm34 disrupts Hsp70 dimer and this event plays an important role in Hsp70 activity regulation. In summary, this study provides structural evidence of robust ATP-dependent antiparallel dimerization of human inducible Hsp70 protein and suggests novel role of TPR domain co-chaperones in multichaperone complexes involving Hsp70 ATP-bound dimers.

2018-12-11 | PXD010069 | Pride

Transcriptional response to the HSP70 inhibitor MAL3-101 in parental rhabdomyosarcoma cells and isogenic acquired-resistance lines.

Project description:We demonstrate that inhibition of HSP70 with MAL3-101 induces activation of the unfolded protein response, and that cells with acquired resistance upregulate a cytosolic HSP70 at the level of mRNA. Whole transcriptome sequencing was undertaken of parental or acquired-resistance RMS13 cells treated with either DMSO or 10 micromolar MAL3-101.

2016-05-15 | E-GEOD-80525 | biostudies-arrayexpress

Transcriptional response to the HSP70 inhibitor MAL3-101 in parental rhabdomyosarcoma cells and isogenic acquired-resistance lines.

2016-05-15 | GSE80525 | GEO

Regulation of the Hsf1-dependent transcriptome via conserved bipartite contacts with Hsp70 promotes survival in yeast

Project description:Protein homeostasis and cellular fitness in the presence of proteotoxic stress is promoted by heat shock factor 1 (HSF1), which controls basal and stress-induced expression of molecular chaperones and other targets. The major heat shock proteins Hsp70 and Hsp90 in turn participate in a negative feedback loop that ensures appropriate coordination of the heat shock response with environmental conditions. Features of this regulatory circuit in the budding yeast Saccharomyces cerevisiae have been recently defined, most notably regarding direct interaction between Hsf1 and the constitutively expressed Hsp70 Ssa1. We sought to further explore the complex nature of Ssa1/Hsf1 regulation. Ssa1 is found to interact independently with both the previously defined CE2 site in the Hsf1 carboxyl-terminal transcriptional activation domain as well as a novel site that we identify within the amino-terminal activation domain. Consistent with both sites bearing a recognition signature for Hsp70, we demonstrate that Ssa1 contacts Hsf1 using its substrate binding domain and abolishing either regulatory site results in loss of Ssa1 association. Removing Hsp70 regulation of Hsf1 results in global dysregulation of Hsf1 transcriptional activity, with synergistic effects when both sites are disrupted together on both gene expression and cellular fitness. Finally, we find that Hsp70 interacts with both transcriptional activation domains of Hsf1 in the related yeast Lachancea kluyveri, implying a conserved mechanism of regulation to promote cellular proteostasis.

2019-04-16 | GSE129832 | GEO

Cytosolic splice isoform of Hsp70 nucleotide exchange factor Fes1 is required for the degradation of misfolded proteins in yeast

Project description:Cells maintain proteostasis by selectively recognizing and targeting misfolded proteins for degradation. In Saccharomyces cerevisiae, the Hsp70 nucleotide exchange factor Fes1 is essential for the degradation of chaperone-associated misfolded proteins by the ubiquitin-proteasome system. Here we show that the FES1 transcript undergoes unique 3' alternative splicing that results in two equally active isoforms with alternative C-termini, Fes1L and Fes1S. Fes1L is actively targeted to the nucleus and represents the first identified nuclear Hsp70 nucleotide exchange factor. In contrast, Fes1S localizes to the cytosol and is essential to maintain proteostasis. In the absence of Fes1S, the heat-shock response is constitutively induced at normally non-stressful conditions. Moreover, cells display severe growth defects when elevated temperatures, amino acid analogues or the ectopic expression of misfolded proteins, induce protein misfolding. Importantly, misfolded proteins are not targeted for degradation by the ubiquitin-proteasome system. These observations support the notion that cytosolic Fes1S maintains proteostasis by supporting the removal of toxic misfolded proteins by proteasomal degradation. This study provides key findings for the understanding of the organization of protein quality control mechanisms in the cytosol and nucleus. 4 strains (WT, fes1Î, fes1ÎS, fes1ÎL) were sequenced in triplicates from independent RNA isolations.

2016-02-29 | E-GEOD-78136 | biostudies-arrayexpress

Allosteric HSP70 inhibitors in Proteasome Inhibitor Resistant Multiple Myeloma

Project description:Proteasome inhibitor (PI) resistance remains a central challenge in multiple myeloma. To identify pathways mediating resistance, we first mapped proteasome-associated genetic co-dependencies. We identified cytosolic heat shock protein 70 (HSP70) chaperones as potential targets, consistent with proposed mechanisms of myeloma tumor cells overcoming PI-induced stress. These results led us to explore allosteric HSP70 inhibitors (JG compounds) as myeloma therapeutics. We showed these compounds exhibit increased efficacy against acquired and intrinsic PI-resistant myeloma models, unlike HSP90 inhibition. Surprisingly, shotgun and pulsed-SILAC mass spectrometry found that JGs have the most pronounced effect on the proteome not through inhibiting cytosolic HSP70s but instead through mitochondrial-localized HSP70, HSPA9/mortalin, destabilizing the 55S mitoribosome. Analysis of myeloma patient data further supports strong effects of global proteostasis capacity, and particularly HSPA9 expression, on PI response. Our results characterize myeloma proteostasis networks under therapeutic pressure while motivating further investigation of HSPA9 as a specific vulnerability in PI-resistant disease.

2022-05-27 | PXD032030 | Pride

Proteostasis by STUB1/HSP70 complex controls sensitivity to androgen receptor targeted therapy in advanced prostate cancer (Affymetrix)

Project description:Constitutively active androgen receptor (AR) signaling confers resistance to AR-targeted therapies. Here we show that the ubiquitin-mediated proteolysis pathway plays a critical role in the degradation of AR and its variants, particularly variant 7 (AR-V7). AR/AR-V7 proteinhomeostasis (proteostasis) requires interaction of the E3 ubiquitin ligase STUB1 and HSP70complex. STUB1 disassociates AR/AR-V7 from HSP70, leading to AR/AR-V7 ubiquitination and degradation. Inhibition of HSP70 reduces AR/AR-V7 expression which significantly inhibits prostate tumor growth and improves enzalutamide/abiraterone treatments. Clinically, HSP70 expression is upregulated and correlated with AR/AR-V7 levels in high Gleason scores prostate tumors. Our results reveal a novel mechanism of AR-V7 modulation via proteostasis which could be targeted to reduce AR-V7 expression and overcome resistance to AR-targeted therapies.

2018-10-05 | GSE120005 | GEO

Proteostasis by STUB1/HSP70 complex controls sensitivity to androgen receptor targeted therapy in advanced prostate cancer (RNA-Seq)

2018-10-05 | GSE120004 | GEO

The essential chaperone DNAJC17 activates HSP70 to coordinate RNA splicing and G2-M progression

Project description:Molecular chaperones including the heat-shock protein 70-kilodalton (HSP70) family and the J-domain containing protein (JDP) co-chaperones maintain homeostatic balance in eukaryotic cells through regulation of the proteome. The expansive JDP family helps direct specific HSP70 functions, and yet loss of single JDP-encoding genes is widely tolerated by mammalian cells, suggesting a high degree of redundancy. Using a genetic screen of DJPs in human cancer cell lines, we found the RNA recognition motif (RRM) containing DNAJC17 to be pan-essential. Knockdown of DNAJC17 leads to relatively few conserved changes in the abundance of individual mRNAs, but instead deranges gene expression through exon skipping, primarily of genes involved in cell cycle progression. Concordant with cell viability experiments, the C-terminal portions of DNAJC17 are dispensable for restoring splicing and G2-M progression. Our findings identify essential cellular JDPs and suggest that diversification in JDP structure extends the HSP70-JDP system to control divergent processes such as RNA splicing.

2023-06-20 | GSE235379 | GEO

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