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VanDemark AP, Hrizo SL, Eicher SL, Kowalski J, Myers TD, Pfeifer MR, Riley KN, Koeberl DD, Palladino MJ. Itavastatin and resveratrol increase triosephosphate isomerase protein in a newly identified variant of TPI deficiency. Dis Model Mech 2022; 15:274792. [PMID: 35315486 PMCID: PMC9150114 DOI: 10.1242/dmm.049261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 03/14/2022] [Indexed: 11/20/2022] Open
Abstract
Triosephosphate isomerase (TPI) deficiency (TPI Df) is an untreatable glycolytic enzymopathy that results in hemolytic anemia, progressive muscular impairment and irreversible brain damage. Although there is a ‘common’ mutation (TPIE105D), other pathogenic mutations have been described. We identified patients who were compound heterozygous for a newly described mutation, TPIQ181P, and the common TPIE105D mutation. Intriguingly, these patients lacked neuropathy or cognitive impairment. We then initiated biochemical and structural studies of TPIQ181P. Surprisingly, we found that purified TPIQ181P protein had markedly impaired catalytic properties whereas crystallographic studies demonstrated that the TPIQ181P mutation resulted in a highly disordered catalytic lid. We propose that genetic complementation occurs between the two alleles, one with little activity (TPIQ181P) and one with low stability (TPIE105D). Consistent with this, TPIQ181P/E105D fibroblasts exhibit a significant reduction in the TPI protein. These data suggest that impaired stability, and not catalytic activity, is a better predictor of TPI Df severity. Lastly, we tested two recently discovered chemical modulators of mutant TPI stability, itavastatin and resveratrol, and observed a significant increase in TPI in TPIQ181P/E105D patient cells. Summary: A newly identified triosephosphate isomerase (TPI) variant (TPIQ181P) confers TPI deficiency, suggests a molecular and genetic model for its pathogenesis, and the potential for therapeutic intervention.
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Affiliation(s)
- Andrew P VanDemark
- Biological Sciences and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Stacy L Hrizo
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Department of Biology, Slippery Rock University of Pennsylvania, Slippery Rock, PA 16057, USA
| | - Samantha L Eicher
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Jules Kowalski
- Biological Sciences and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Tracey D Myers
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Megan R Pfeifer
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Kacie N Riley
- Department of Pediatrics, Division of Medical Genetics, Duke University Medical Center, Durham, NC 27710, USA
| | - Dwight D Koeberl
- Department of Pediatrics, Division of Medical Genetics, Duke University Medical Center, Durham, NC 27710, USA
| | - Michael J Palladino
- Biological Sciences and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA.,Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Vogt A, Eicher SL, Myers TD, Hrizo SL, Vollmer LL, Meyer EM, Palladino MJ. A High-Content Screening Assay for Small Molecules That Stabilize Mutant Triose Phosphate Isomerase (TPI) as Treatments for TPI Deficiency. SLAS Discov 2021; 26:1029-1039. [PMID: 34167376 DOI: 10.1177/24725552211018198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Triose phosphate isomerase deficiency (TPI Df) is an untreatable, childhood-onset glycolytic enzymopathy. Patients typically present with frequent infections, anemia, and muscle weakness that quickly progresses with severe neuromusclar dysfunction requiring aided mobility and often respiratory support. Life expectancy after diagnosis is typically ~5 years. There are several described pathogenic mutations that encode functional proteins; however, these proteins, which include the protein resulting from the "common" TPIE105D mutation, are unstable due to active degradation by protein quality control (PQC) pathways. Previous work has shown that elevating mutant TPI levels by genetic or pharmacological intervention can ameliorate symptoms of TPI Df in fruit flies. To identify compounds that increase levels of mutant TPI, we have developed a human embryonic kidney (HEK) stable knock-in model expressing the common TPI Df protein fused with green fluorescent protein (HEK TPIE105D-GFP). To directly address the need for lead TPI Df therapeutics, these cells were developed into an optical drug discovery platform that was implemented for high-throughput screening (HTS) and validated in 3-day variability tests, meeting HTS standards. We initially used this assay to screen the 446-member National Institutes of Health (NIH) Clinical Collection and validated two of the hits in dose-response, by limited structure-activity relationship studies with a small number of analogs, and in an orthogonal, non-optical assay in patient fibroblasts. The data form the basis for a large-scale phenotypic screening effort to discover compounds that stabilize TPI as treatments for this devastating childhood disease.
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Affiliation(s)
- Andreas Vogt
- Department of Computational & Systems Biology, Drug Discovery Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Samantha L Eicher
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Tracey D Myers
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Stacy L Hrizo
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Department of Biology, Slippery Rock University of Pennsylvania, Slippery Rock, PA, USA
| | - Laura L Vollmer
- Department of Computational & Systems Biology, Drug Discovery Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | | | - Michael J Palladino
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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Hrizo SL, Eicher SL, Myers TD, McGrath I, Wodrich APK, Venkatesh H, Manjooran D, Swoger S, Gagnon K, Bruskin M, Lebedev MV, Zheng S, Vitantonio A, Kim S, Lamb ZJ, Vogt A, Ruzhnikov MRZ, Palladino MJ. Identification of protein quality control regulators using a Drosophila model of TPI deficiency. Neurobiol Dis 2021; 152:105299. [PMID: 33600953 PMCID: PMC7993632 DOI: 10.1016/j.nbd.2021.105299] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 02/07/2023] Open
Abstract
Triosephosphate isomerase (TPI) deficiency (Df) is a rare recessive metabolic disorder that manifests as hemolytic anemia, locomotor impairment, and progressive neurodegeneration. Research suggests that TPI Df mutations, including the "common" TPIE105Dmutation, result in reduced TPI protein stability that appears to underlie disease pathogenesis. Drosophila with the recessive TPIsugarkill allele (a.k.a. sgk or M81T) exhibit progressive locomotor impairment, neuromuscular impairment and reduced longevity, modeling the human disorder. TPIsugarkill produces a functional protein that is degraded by the proteasome. Molecular chaperones, such as Hsp70 and Hsp90, have been shown to contribute to the regulation of TPIsugarkill degradation. In addition, stabilizing the mutant protein through chaperone modulation results in improved TPI deficiency phenotypes. To identify additional regulators of TPIsugarkill degradation, we performed a genome-wide RNAi screen that targeted known and predicted quality control proteins in the cell to identify novel factors that modulate TPIsugarkill turnover. Of the 430 proteins screened, 25 regulators of TPIsugarkill were identified. Interestingly, 10 proteins identified were novel, previously undescribed Drosophila proteins. Proteins involved in co-translational protein quality control and ribosome function were also isolated in the screen, suggesting that TPIsugarkill may undergo co-translational selection for polyubiquitination and proteasomal degradation as a nascent polypeptide. The proteins identified in this study may reveal novel pathways for the degradation of a functional, cytosolic protein by the ubiquitin proteasome system and define therapeutic pathways for TPI Df and other biomedically important diseases.
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Affiliation(s)
- Stacy L Hrizo
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Department of Biology, Slippery Rock University of Pennsylvania, Slippery Rock, PA 16057, USA
| | - Samantha L Eicher
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Tracey D Myers
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Ian McGrath
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Andrew P K Wodrich
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Hemanth Venkatesh
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Daniel Manjooran
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Sabrina Swoger
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Kim Gagnon
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Matthew Bruskin
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Maria V Lebedev
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Sherry Zheng
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Ana Vitantonio
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Sungyoun Kim
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Zachary J Lamb
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Andreas Vogt
- Department of Computational & Systems Biology, Drug Discovery Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Maura R Z Ruzhnikov
- Department of Neurology, Stanford University School of Medicine, Stanford, CA 94304, USA; Department of Pediatrics, Division of Medical Genetics, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Michael J Palladino
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Roland BP, Richards KR, Hrizo SL, Eicher S, Barile ZJ, Chang TC, Savon G, Bianchi P, Fermo E, Ricerca BM, Tortorolo L, Vockley J, VanDemark AP, Palladino MJ. Missense variant in TPI1 (Arg189Gln) causes neurologic deficits through structural changes in the triosephosphate isomerase catalytic site and reduced enzyme levels in vivo. Biochim Biophys Acta Mol Basis Dis 2019; 1865:2257-2266. [PMID: 31075491 DOI: 10.1016/j.bbadis.2019.05.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 12/20/2018] [Accepted: 01/06/2019] [Indexed: 12/27/2022]
Abstract
Mutations in the gene triosephosphate isomerase (TPI) lead to a severe multisystem condition that is characterized by hemolytic anemia, a weakened immune system, and significant neurologic symptoms such as seizures, distal neuropathy, and intellectual disability. No effective therapy is available. Here we report a compound heterozygous patient with a novel TPI pathogenic variant (NM_000365.5:c.569G>A:p.(Arg189Gln)) in combination with the common (NM_000365.5:c.315G>C:p.(Glu104Asp)) allele. We characterized the novel variant by mutating the homologous Arg in Drosophila using a genomic engineering system, demonstrating that missense mutations at this position cause a strong loss of function. Compound heterozygote animals were generated and exhibit motor behavioural deficits and markedly reduced protein levels. Furthermore, examinations of the TPIArg189Gln/TPIGlu104Asp patient fibroblasts confirmed the reduction of TPI levels, suggesting that Arg189Gln may also affect the stability of the protein. The Arg189 residue participates in two salt bridges on the backside of the TPI enzyme dimer, and we reveal that a mutation at this position alters the coordination of the substrate-binding site and important catalytic residues. Collectively, these data reveal a new human pathogenic variant associated with TPI deficiency, identify the Arg189 salt bridge as critical for organizing the catalytic site of the TPI enzyme, and demonstrates that reduced TPI levels are associated with human TPI deficiency. These findings advance our understanding of the molecular pathogenesis of the disease, and suggest new therapeutic avenues for pre-clinical trials.
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Affiliation(s)
- Bartholomew P Roland
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Kristen R Richards
- Biological Sciences and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Stacy L Hrizo
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Department of Biology, Slippery Rock University, Slippery Rock, PA 16057, USA
| | - Samantha Eicher
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Zackery J Barile
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Tien-Chien Chang
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Grace Savon
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Paola Bianchi
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, UOC Ematologia, UOS Fisiopatologia delle Anemie, Via F Sforza, 35, 20122 Milan, Italy
| | - Elisa Fermo
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, UOC Ematologia, UOS Fisiopatologia delle Anemie, Via F Sforza, 35, 20122 Milan, Italy
| | - Bianca Maria Ricerca
- Hematology Institute, Universitary Hospital A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy
| | - Luca Tortorolo
- Pediatric Intensive Care Unit, Universitary Hospital A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy
| | - Jerry Vockley
- Department of Pediatrics and Human Genetics, University of Pittsburgh Schools of Medicine and Public health, Pittsburgh, PA 15261, USA
| | - Andrew P VanDemark
- Biological Sciences and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA.
| | - Michael J Palladino
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Institute for Neurodegenerative Diseases (PIND), University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Hrizo SL, Fisher IJ, Long DR, Hutton JA, Liu Z, Palladino MJ. Early mitochondrial dysfunction leads to altered redox chemistry underlying pathogenesis of TPI deficiency. Neurobiol Dis 2013; 54:289-96. [PMID: 23318931 DOI: 10.1016/j.nbd.2012.12.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 11/28/2012] [Accepted: 12/21/2012] [Indexed: 12/19/2022] Open
Abstract
Triose phosphate isomerase (TPI) is responsible for the interconversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate in glycolysis. Point mutations in this gene are associated with a glycolytic enzymopathy called TPI deficiency. This study utilizes a Drosophila melanogaster model of TPI deficiency; TPI(sugarkill) is a mutant allele with a missense mutation (M80T) that causes phenotypes similar to human TPI deficiency. In this study, the redox status of TPI(sugarkill) flies was examined and manipulated to provide insight into the pathogenesis of this disease. Our data show that TPI(sugarkill) animals exhibit higher levels of the oxidized forms of NAD(+), NADP(+) and glutathione in an age-dependent manner. Additionally, we demonstrate that mitochondrial redox state is significantly more oxidized in TPI(sugarkill) animals. We hypothesized that TPI(sugarkill) animals may be more sensitive to oxidative stress and that this may underlie the progressive nature of disease pathogenesis. The effect of oxidizing and reducing stressors on behavioral phenotypes of the TPI(sugarkill) animals was tested. As predicted, oxidative stress worsened these phenotypes. Importantly, we discovered that reducing stress improved the behavioral and longevity phenotypes of the mutant organism without having an effect on TPI(sugarkill) protein levels. Overall, these data suggest that reduced activity of TPI leads to an oxidized redox state in these mutants and that the alleviation of this stress using reducing compounds can improve the mutant phenotypes.
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Affiliation(s)
- Stacy L Hrizo
- Deparment of Pharmacology & Chemical Biology, University of Pittsburgh Medical School, Pittsburgh, PA 15261, USA.
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Hrizo SL, Palladino MJ. Hsp70- and Hsp90-mediated proteasomal degradation underlies TPI sugarkill pathogenesis in Drosophila. Neurobiol Dis 2010; 40:676-83. [PMID: 20727972 DOI: 10.1016/j.nbd.2010.08.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 08/04/2010] [Accepted: 08/12/2010] [Indexed: 10/19/2022] Open
Abstract
Triosephosphate isomerase (TPI) deficiency is a severe glycolytic enzymopathy that causes progressive locomotor impairment and neurodegeneration, susceptibility to infection, and premature death. The recessive missense TPI(sugarkill) mutation in Drosophila melanogaster exhibits phenotypes analogous to human TPI deficiency such as progressive locomotor impairment, neurodegeneration, and reduced life span. We have shown that the TPI(sugarkill) protein is an active stable dimer; however, the mutant protein is turned over by the proteasome reducing cellular levels of this glycolytic enzyme. As proteasome function is often coupled with molecular chaperone activity, we hypothesized that TPI(sugarkill) is recognized by molecular chaperones that mediate the proteasomal degradation of the mutant protein. Coimmunoprecipitation data and analyses of TPI(sugarkill) turnover in animals with reduced or enhanced molecular chaperone activity indicate that both Hsp90 and Hsp70 are important for targeting TPI(sugarkill) for degradation. Furthermore, molecular chaperone and proteasome activity modified by pharmacological or genetic manipulations resulted in improved TPI(sugarkill) protein levels and rescue some but not all of the disease phenotypes suggesting that TPI deficiency pathology is complex. Overall, these data demonstrate a surprising role for Hsp70 and Hsp90 in the progression of neural dysfunction associated with TPI deficiency.
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Affiliation(s)
- Stacy L Hrizo
- Deparment of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Hrizo SL, Kaufmann N. Illuminating cell signaling: Using Vibrio harveyi in an introductory biology laboratory. Biochem Mol Biol Educ 2009; 37:164-169. [PMID: 21567726 DOI: 10.1002/bmb.20262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Cell signaling is an essential cellular process that is performed by all living organisms. Bacteria communicate with each other using a chemical language in a signaling pathway that allows bacteria to evaluate the size of their population, determine when they have reached a critical mass (quorum sensing), and then change their behavior in unison to carry out processes that require many cells acting together to be effective. Here, we describe a laboratory exercise in which the students observe the induction of bioluminescence or light production as an output of the quorum sensing pathway in Vibrio harveyi. Using both wildtype and mutant bacterial strains they explore the induction of community behavior via cell-cell communication by determining whether there is a correlation between the density of the bacterial population and the production of light by the bacterial culture. Using data from a cross-feeding assay the students make predictions about the identity of their strains and directly test these predictions using conditioned media from various liquid cultures. This two part exercise is designed for an introductory biology course to begin familiarizing students with collecting data, making predictions based upon the data and directly testing their hypotheses using a model organism with a cell signaling pathway that has a simple visual output: light production.
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Affiliation(s)
- Stacy L Hrizo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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Hrizo SL, Gusarova V, Habiel DM, Goeckeler JL, Fisher EA, Brodsky JL. The Hsp110 molecular chaperone stabilizes apolipoprotein B from endoplasmic reticulum-associated degradation (ERAD). J Biol Chem 2007; 282:32665-75. [PMID: 17823116 PMCID: PMC2666968 DOI: 10.1074/jbc.m705216200] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein B (apoB) is the most abundant protein in low density lipoproteins and plays key roles in cholesterol homeostasis. The co-translational degradation of apoB is controlled by fatty acid levels in the endoplasmic reticulum (ER) and is mediated by the proteasome. To define the mechanism of apoB degradation, we employed a cell-free system in which proteasome-dependent degradation is recapitulated with yeast cytosol, and we developed an apoB yeast expression system. We discovered that a yeast Hsp110, Sse1p, associates with and stabilizes apoB, which contrasts with data indicating that select Hsp70s and Hsp90s facilitate apoB degradation. However, the Ssb Hsp70 chaperones have no effect on apoB turnover. To determine whether our results are relevant in mammalian cells, Hsp110 was overexpressed in hepatocytes, and enhanced apoB secretion was observed. This study indicates that chaperones within distinct complexes can play unique roles during ER-associated degradation (ERAD), establishes a role for Sse1/Hsp110 in ERAD, and identifies Hsp110 as a target to lower cholesterol.
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Affiliation(s)
- Stacy L. Hrizo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Viktoria Gusarova
- Departments of Medicine (Cardiology) and Cell Biology, New York University School of Medicine, New York, New York 10016
| | - David M. Habiel
- Departments of Medicine (Cardiology) and Cell Biology, New York University School of Medicine, New York, New York 10016
| | - Jennifer L. Goeckeler
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Edward A. Fisher
- Departments of Medicine (Cardiology) and Cell Biology, New York University School of Medicine, New York, New York 10016
| | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
- To whom correspondence should be addressed: Dept. of Biological Sciences, 274 Crawford Hall, University of Pittsburgh, Pittsburgh, PA 15260. Tel.: 412-624-4830; Fax: 412-624-4759; E-mail:
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