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Henriques A, Poindron PLL, Fernando B, Hascup KN. Editorial: Neurotoxins in Alzheimer's disease and other dementias. Front Aging Neurosci 2024; 16:1363466. [PMID: 38282691 PMCID: PMC10808754 DOI: 10.3389/fnagi.2024.1363466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 01/03/2024] [Indexed: 01/30/2024] Open
Affiliation(s)
| | | | - Binosha Fernando
- Centre of Excellence for Alzheimer's Disease Research and Care School of Medical and Health Sciences, Edith Cowan University, SNRI, Nedlands, WA, Australia
| | - Kevin N. Hascup
- Department of Neurology, Pharmacology, and Medical Microbiology, Immunology and Cell Biology, Center for Alzheimer's Research and Treatment, Southern Illinois University School of Medicine, Springfield, IL, United States
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2
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Nolan KD, Franco OE, Hance MW, Hayward SW, Isaacs JS. Tumor-secreted Hsp90 subverts polycomb function to drive prostate tumor growth and invasion. J Biol Chem 2015; 290:8271-82. [PMID: 25670862 DOI: 10.1074/jbc.m115.637496] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Prostate cancer remains the second highest contributor to male cancer-related lethality. The transition of a subset of tumors from indolent to invasive disease is associated with a poor clinical outcome. Activation of the epithelial to mesenchymal transition (EMT) genetic program is a major risk factor for cancer progression. We recently reported that secreted extracellular Hsp90 (eHsp90) initiates EMT in prostate cancer cells, coincident with its enhanced expression in mesenchymal models. Our current work substantially extended these findings in defining a pathway linking eHsp90 signaling to EZH2 function, a methyltransferase of the Polycomb repressor complex. EZH2 is also implicated in EMT activation, and its up-regulation represents one of the most frequent epigenetic alterations during prostate cancer progression. We have now highlighted a novel epigenetic function for eHsp90 via its modulation of EZH2 expression and activity. Mechanistically, eHsp90 initiated sustained activation of MEK/ERK, a signal critical for facilitating EZH2 transcriptional up-regulation and recruitment to the E-cadherin promoter. We further demonstrated that an eHsp90-EZH2 pathway orchestrates an expanded repertoire of EMT-related events including Snail and Twist expression, tumor cell motility, and anoikis resistance. To evaluate the role of eHsp90 in vivo, eHsp90 secretion was stably enforced in a prostate cancer cell line resembling indolent disease. Remarkably, eHsp90 was sufficient to induce tumor growth, suppress E-cadherin, and initiate localized invasion, events that are exquisitely dependent upon EZH2 function. In summary, our findings illuminate a hitherto unknown epigenetic function for eHsp90 and support a model wherein tumor eHsp90 functions as a rheostat for EZH2 expression and activity to orchestrate mesenchymal properties and coincident aggressive behavior.
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Affiliation(s)
- Krystal D Nolan
- From the Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina 29425 and
| | - Omar E Franco
- the Department of Urology and Cancer Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Michael W Hance
- From the Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina 29425 and
| | - Simon W Hayward
- the Department of Urology and Cancer Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Jennifer S Isaacs
- From the Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina 29425 and
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Davis AL, Qiao S, Lesson JL, Rojo de la Vega M, Park SL, Seanez CM, Gokhale V, Cabello CM, Wondrak GT. The quinone methide aurin is a heat shock response inducer that causes proteotoxic stress and Noxa-dependent apoptosis in malignant melanoma cells. J Biol Chem 2014; 290:1623-38. [PMID: 25477506 DOI: 10.1074/jbc.m114.592626] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Pharmacological induction of proteotoxic stress is rapidly emerging as a promising strategy for cancer cell-directed chemotherapeutic intervention. Here, we describe the identification of a novel drug-like heat shock response inducer for the therapeutic induction of proteotoxic stress targeting malignant human melanoma cells. Screening a focused library of compounds containing redox-directed electrophilic pharmacophores employing the Stress & Toxicity PathwayFinder(TM) PCR Array technology as a discovery tool, a drug-like triphenylmethane-derivative (aurin; 4-[bis(p-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one) was identified as an experimental cell stress modulator that causes (i) heat shock factor transcriptional activation, (ii) up-regulation of heat shock response gene expression (HSPA6, HSPA1A, DNAJB4, HMOX1), (iii) early unfolded protein response signaling (phospho-PERK, phospho-eIF2α, CHOP (CCAAT/enhancer-binding protein homologous protein)), (iv) proteasome impairment with increased protein-ubiquitination, and (v) oxidative stress with glutathione depletion. Fluorescence polarization-based experiments revealed that aurin displays activity as a geldanamycin-competitive Hsp90α-antagonist, a finding further substantiated by molecular docking and ATPase inhibition analysis. Aurin exposure caused caspase-dependent cell death in a panel of human malignant melanoma cells (A375, G361, LOX-IMVI) but not in non-malignant human skin cells (Hs27 fibroblasts, HaCaT keratinocytes, primary melanocytes) undergoing the aurin-induced heat shock response without impairment of viability. Aurin-induced melanoma cell apoptosis depends on Noxa up-regulation as confirmed by siRNA rescue experiments demonstrating that siPMAIP1-based target down-regulation suppresses aurin-induced cell death. Taken together, our data suggest feasibility of apoptotic elimination of malignant melanoma cells using the quinone methide-derived heat shock response inducer aurin.
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Affiliation(s)
- Angela L Davis
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Shuxi Qiao
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Jessica L Lesson
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Montserrat Rojo de la Vega
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Sophia L Park
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Carol M Seanez
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Vijay Gokhale
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Christopher M Cabello
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
| | - Georg T Wondrak
- From the Department of Pharmacology and Toxicology, College of Pharmacy and Arizona Cancer Center, University of Arizona, Tucson, Arizona 85724
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Abstract
Aha1 (activator of Hsp90 ATPase) stimulates the ATPase activity of the molecular chaperone Hsp90 to accelerate the conformational cycle during which client proteins attain their final shape. Thereby, Aha1 promotes effective folding of Hsp90-dependent clients such as steroid receptors and many kinases involved in cellular signaling. In our current study, we find that Aha1 plays a novel, additional role beyond regulating the Hsp90 ATP hydrolysis rate. We propose a new concept suggesting that Aha1 acts as an autonomous chaperone and associates with stress-denatured proteins to prevent them from aggregation similar to the chaperonin GroEL. Our study reveals that an N-terminal sequence of 22 amino acids, present in human but absent from yeast Aha1, is critical for this capability. However, in lieu of fostering their refolding, Aha1 allows ubiquitination of bound clients by the E3 ubiquitin ligase CHIP. Accordingly, Aha1 may promote disposal of folding defective proteins by the cellular protein quality control.
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Affiliation(s)
- Vishwadeepak Tripathi
- From the Department of Cardiovascular Physiology, Ruhr-University Bochum, 44801 Bochum, Germany
| | - Stefanie Darnauer
- From the Department of Cardiovascular Physiology, Ruhr-University Bochum, 44801 Bochum, Germany
| | - Nadine R Hartwig
- From the Department of Cardiovascular Physiology, Ruhr-University Bochum, 44801 Bochum, Germany
| | - Wolfgang M J Obermann
- From the Department of Cardiovascular Physiology, Ruhr-University Bochum, 44801 Bochum, Germany
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Abstract
Cholera toxin (CT) moves from the cell surface to the endoplasmic reticulum (ER) where the catalytic CTA1 subunit separates from the rest of the toxin. CTA1 then unfolds and passes through an ER translocon pore to reach its cytosolic target. Due to its intrinsic instability, cytosolic CTA1 must be refolded to achieve an active conformation. The cytosolic chaperone Hsp90 is involved with the ER to cytosol export of CTA1, but the mechanistic role of Hsp90 in CTA1 translocation remains unknown. Moreover, potential post-translocation roles for Hsp90 in modulating the activity of cytosolic CTA1 have not been explored. Here, we show by isotope-edited Fourier transform infrared spectroscopy that Hsp90 induces a gain-of-structure in disordered CTA1 at physiological temperature. Only the ATP-bound form of Hsp90 interacts with disordered CTA1, and refolding of CTA1 by Hsp90 is dependent upon ATP hydrolysis. In vitro reconstitution of the CTA1 translocation event likewise required ATP hydrolysis by Hsp90. Surface plasmon resonance experiments found that Hsp90 does not release CTA1, even after ATP hydrolysis and the return of CTA1 to a folded conformation. The interaction with Hsp90 allows disordered CTA1 to attain an active state, which is further enhanced by ADP-ribosylation factor 6, a host cofactor for CTA1. Our data indicate CTA1 translocation involves a process that couples the Hsp90-mediated refolding of CTA1 with CTA1 extraction from the ER. The molecular basis for toxin translocation elucidated in this study may also apply to several ADP-ribosylating toxins that move from the endosomes to the cytosol in an Hsp90-dependent process.
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Affiliation(s)
- Helen Burress
- From the Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32826 and
| | - Michael Taylor
- From the Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32826 and
| | - Tuhina Banerjee
- From the Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32826 and
| | - Suren A Tatulian
- the Department of Physics, University of Central Florida, Orlando, Florida 32816
| | - Ken Teter
- From the Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32826 and
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6
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El-Kasaby A, Koban F, Sitte HH, Freissmuth M, Sucic S. A cytosolic relay of heat shock proteins HSP70-1A and HSP90β monitors the folding trajectory of the serotonin transporter. J Biol Chem 2014; 289:28987-9000. [PMID: 25202009 PMCID: PMC4200255 DOI: 10.1074/jbc.m114.595090] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mutations in the C terminus of the serotonin transporter (SERT) disrupt folding and export from the endoplasmic reticulum. Here we examined the hypothesis that a cytosolic heat shock protein relay was recruited to the C terminus to assist folding of SERT. This conjecture was verified by the following observations. (i) The proximal portion of the SERT C terminus conforms to a canonical binding site for DnaK/heat shock protein of 70 kDa (HSP70). A peptide covering this segment stimulated ATPase activity of purified HSP70-1A. (ii) A GST fusion protein comprising the C terminus of SERT pulled down HSP70-1A. The interaction between HSP70-1A and SERT was visualized in live cells by Förster resonance energy transfer: it was restricted to endoplasmic reticulum-resident transporters and enhanced by an inhibitor that traps HSP70-1A in its closed state. (iv) Co-immunoprecipitation confirmed complex formation of SERT with HSP70-1A and HSP90β. Consistent with an HSP relay, co-chaperones (e.g. HSC70-HSP90-organizing protein) were co-immunoprecipitated with the stalled mutants SERT-R607A/I608A and SERT-P601A/G602A. (v) Depletion of HSP90β by siRNA or its inhibition increased the cell surface expression of wild type SERT and SERT-F604Q. In contrast, SERT-R607A/I608A and SERT-P601A/G602A were only rendered susceptible to inhibition of HSP70 and HSP90 by concomitant pharmacochaperoning with noribogaine. (vi) In JAR cells, inhibition of HSP90 also increased the levels of SERT, indicating that endogenously expressed transporter was also susceptible to control by HSP90β. These findings support the concept that the folding trajectory of SERT is sampled by a cytoplasmic chaperone relay.
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Affiliation(s)
- Ali El-Kasaby
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and the Department of Pharmacology, Faculty of Veterinary Medicine, Mansoura University, 35516 Mansoura, Egypt
| | - Florian Koban
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Harald H Sitte
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Michael Freissmuth
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Sonja Sucic
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
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He Q, Wen D, Jia Q, Cui C, Wang J, Palli SR, Li S. Heat shock protein 83 (Hsp83) facilitates methoprene-tolerant (Met) nuclear import to modulate juvenile hormone signaling. J Biol Chem 2014; 289:27874-85. [PMID: 25122763 DOI: 10.1074/jbc.m114.582825] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Juvenile hormone (JH) receptors, methoprene-tolerant (Met) and Germ-cell expressed (Gce), transduce JH signals to induce Kr-h1 expression in Drosophila. Dual luciferase assay identified a 120-bp JH response region (JHRR) in the Kr-h1α promoter. Both in vitro and in vivo experiments revealed that Met and Gce transduce JH signals to induce Kr-h1 expression through the JHRR. DNA affinity purification identified chaperone protein Hsp83 as one of the proteins bound to the JHRR in the presence of JH. Interestingly, Hsp83 physically interacts with PAS-B and basic helix-loop-helix domains of Met, and JH induces Met-Hsp83 interaction. As determined by immunohistochemistry, Met is mainly distributed in the cytoplasm of fat body cells of the larval when the JH titer is low and JH induces Met nuclear import. Hsp83 was accumulated in the cytoplasm area adjunct to the nucleus in the presence of JH and Met/Gce. Loss-of-function of Hsp83 attenuated JH binding and JH-induced nuclear import of Met, resulting in a decrease in the JHRR-driven reporter activity leading to reduction of Kr-h1 expression. These data show that Hsp83 facilitates the JH-induced nuclear import of Met that induces Kr-h1 expression through the JHRR.
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Affiliation(s)
- Qianyu He
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China, the College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing 163319, China
| | - Di Wen
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Qiangqiang Jia
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Chunlai Cui
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jian Wang
- the Department of Entomology, University of Maryland, College Park, Maryland 20742, and
| | - Subba R Palli
- the Department of Entomology, College of Agriculture, University of Kentucky, Lexington, Kentucky 40546
| | - Sheng Li
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China,
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Erlejman AG, De Leo SA, Mazaira GI, Molinari AM, Camisay MF, Fontana V, Cox MB, Piwien-Pilipuk G, Galigniana MD. NF-κB transcriptional activity is modulated by FK506-binding proteins FKBP51 and FKBP52: a role for peptidyl-prolyl isomerase activity. J Biol Chem 2014; 289:26263-26276. [PMID: 25104352 DOI: 10.1074/jbc.m114.582882] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Hsp90 binding immunophilins FKBP51 and FKBP52 modulate steroid receptor trafficking and hormone-dependent biological responses. With the purpose to expand this model to other nuclear factors that are also subject to nuclear-cytoplasmic shuttling, we analyzed whether these immunophilins modulate NF-κB signaling. It is demonstrated that FKBP51 impairs both the nuclear translocation rate of NF-κB and its transcriptional activity. The inhibitory action of FKBP51 requires neither the peptidylprolyl-isomerase activity of the immunophilin nor its association with Hsp90. The TPR domain of FKBP51 is essential. On the other hand, FKBP52 favors the nuclear retention time of RelA, its association to a DNA consensus binding sequence, and NF-κB transcriptional activity, the latter effect being strongly dependent on the peptidylprolyl-isomerase activity and also on the TPR domain of FKBP52, but its interaction with Hsp90 is not required. In unstimulated cells, FKBP51 forms endogenous complexes with cytoplasmic RelA. Upon cell stimulation with phorbol ester, the NF-κB soluble complex exchanges FKBP51 for FKBP52, and the NF-κB biological effect is triggered. Importantly, FKBP52 is functionally recruited to the promoter region of NF-κB target genes, whereas FKBP51 is released. Competition assays demonstrated that both immunophilins antagonize one another, and binding assays with purified proteins suggest that the association of RelA and immunophilins could be direct. These observations suggest that the biological action of NF-κB in different cell types could be positively regulated by a high FKBP52/FKBP51 expression ratio by favoring NF-κB nuclear retention, recruitment to the promoter regions of target genes, and transcriptional activity.
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Affiliation(s)
- Alejandra G Erlejman
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina
| | - Sonia A De Leo
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina
| | - Gisela I Mazaira
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina
| | - Alejandro M Molinari
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina
| | - María Fernanda Camisay
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina
| | - Vanina Fontana
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina
| | - Marc B Cox
- Border Biomedical Research Center and Department of Biological Sciences, University of Texas, El Paso, Texas 79968
| | - Graciela Piwien-Pilipuk
- Laboratorio de Arquitectura Nuclear, Instituto de Biología y Medicina Experimental/CONICET, Buenos Aires C1428ADN, Argentina, and
| | - Mario D Galigniana
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica de Ciencias Exactas y Naturales (IQUIBICEN)/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1428ADN Argentina,; Laboratorio de Receptores Nucleares, Instituto de Biología y Medicina Experimental/CONICET, Buenos Aires C1428ADN, Argentina.
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Paul A, Garcia YA, Zierer B, Patwardhan C, Gutierrez O, Hildenbrand Z, Harris DC, Balsiger HA, Sivils JC, Johnson JL, Buchner J, Chadli A, Cox MB. The cochaperone SGTA (small glutamine-rich tetratricopeptide repeat-containing protein alpha) demonstrates regulatory specificity for the androgen, glucocorticoid, and progesterone receptors. J Biol Chem 2014; 289:15297-308. [PMID: 24753260 DOI: 10.1074/jbc.m113.535229] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Steroid hormone receptors are ligand-dependent transcription factors that require the ordered assembly of multichaperone complexes for transcriptional activity. Although heat shock protein (Hsp) 90 and Hsp70 are key players in this process, multiple Hsp70- and Hsp90-associated cochaperones associate with receptor-chaperone complexes to regulate receptor folding and activation. Small glutamine-rich tetratricopeptide repeat-containing protein alpha (SGTA) was recently characterized as an Hsp70 and Hsp90-associated cochaperone that specifically regulates androgen receptor activity. However, the specificity of SGTA for additional members of the steroid hormone receptor superfamily and the mechanism by which SGTA regulates receptor activity remain unclear. Here we report that SGTA associates with and specifically regulates the androgen, glucocorticoid, and progesterone receptors and has no effect on the mineralocorticoid and estrogen receptors in both yeast and mammalian cell-based reporter assays. In both systems, SGTA knockdown/deletion enhances receptor activity, whereas SGTA overexpression suppresses receptor activity. We demonstrate that SGTA binds directly to Hsp70 and Hsp90 in vitro with similar affinities yet predominately precipitates with Hsp70 from cell lysates, suggesting a role for SGTA in early, Hsp70-mediated folding. Furthermore, SGTA expression completely abrogates the regulation of receptor function by FKBP52 (52-kDa FK506-binding protein), which acts at a later stage of the chaperone cycle. Taken together, our data suggest a role for SGTA at distinct steps in the chaperone-dependent modulation of androgen, glucocorticoid, and progesterone receptor activity.
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Affiliation(s)
- Atanu Paul
- From the Border Biomedical Research Center and Department of Biological Sciences and
| | - Yenni A Garcia
- From the Border Biomedical Research Center and Department of Biological Sciences and
| | - Bettina Zierer
- the Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Garching, Germany
| | - Chaitanya Patwardhan
- the Cancer Research Center, Georgia Regents University, Augusta, Georgia 30912, and
| | - Omar Gutierrez
- From the Border Biomedical Research Center and Department of Biological Sciences and
| | - Zacariah Hildenbrand
- the Department of Chemistry, University of Texas at El Paso, El Paso, Texas 79968
| | - Diondra C Harris
- From the Border Biomedical Research Center and Department of Biological Sciences and
| | - Heather A Balsiger
- From the Border Biomedical Research Center and Department of Biological Sciences and
| | - Jeffrey C Sivils
- From the Border Biomedical Research Center and Department of Biological Sciences and
| | - Jill L Johnson
- the Department of Biological Sciences, University of Idaho, Moscow, Idaho 83844
| | - Johannes Buchner
- the Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Garching, Germany
| | - Ahmed Chadli
- the Cancer Research Center, Georgia Regents University, Augusta, Georgia 30912, and
| | - Marc B Cox
- From the Border Biomedical Research Center and Department of Biological Sciences and
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