1
|
Gu X, Nardone C, Kamitaki N, Mao A, Elledge SJ, Greenberg ME. The midnolin-proteasome pathway catches proteins for ubiquitination-independent degradation. Science 2023; 381:eadh5021. [PMID: 37616343 PMCID: PMC10617673 DOI: 10.1126/science.adh5021] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 07/11/2023] [Indexed: 08/26/2023]
Abstract
Cells use ubiquitin to mark proteins for proteasomal degradation. Although the proteasome also eliminates proteins that are not ubiquitinated, how this occurs mechanistically is unclear. Here, we found that midnolin promoted the destruction of many nuclear proteins, including transcription factors encoded by the immediate-early genes. Diverse stimuli induced midnolin, and its overexpression was sufficient to cause the degradation of its targets by a mechanism that did not require ubiquitination. Instead, midnolin associated with the proteasome via an α helix, used its Catch domain to bind a region within substrates that can form a β strand, and used a ubiquitin-like domain to promote substrate destruction. Thus, midnolin contains three regions that function in concert to target a large set of nuclear proteins to the proteasome for degradation.
Collapse
Affiliation(s)
- Xin Gu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Christopher Nardone
- Division of Genetics, Department of Medicine, Howard Hughes Medical Institute, Brigham and Women’s Hospital, Boston, MA 02115, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Nolan Kamitaki
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA 02115, USA
| | - Aoyue Mao
- Division of Genetics, Department of Medicine, Howard Hughes Medical Institute, Brigham and Women’s Hospital, Boston, MA 02115, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Stephen J. Elledge
- Division of Genetics, Department of Medicine, Howard Hughes Medical Institute, Brigham and Women’s Hospital, Boston, MA 02115, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | | |
Collapse
|
2
|
Zhou XE, Schultz CR, Suino Powell K, Henrickson A, Lamp J, Brunzelle JS, Demeler B, Vega IE, Bachmann AS, Melcher K. Structure and Enzymatic Activity of an Intellectual Disability-Associated Ornithine Decarboxylase Variant, G84R. ACS OMEGA 2022; 7:34665-34675. [PMID: 36188294 PMCID: PMC9520691 DOI: 10.1021/acsomega.2c04702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 08/30/2022] [Indexed: 06/13/2023]
Abstract
Ornithine decarboxylase (ODC) is a rate-limiting enzyme for the synthesis of polyamines (PAs). PAs are required for proliferation, and increased ODC activity is associated with cancer and neural over-proliferation. ODC levels and activity are therefore tightly regulated, including through the ODC-specific inhibitor, antizyme AZ1. Recently, ODC G84R has been reported as a partial loss-of-function variant that is associated with intellectual disability and seizures. However, G84 is distant from both the catalytic center and the ODC homodimerization interface. To understand how G84R modulates ODC activity, we have determined the crystal structure of ODC G84R in both the presence and the absence of the cofactor pyridoxal 5-phosphate. The structures show that the replacement of G84 by arginine leads to hydrogen bond formation of R84 with F420, the last residue of the ODC C-terminal helix, a structural element that is involved in the AZ1-mediated proteasomal degradation of ODC. In contrast, the catalytic center is essentially indistinguishable from that of wildtype ODC. We therefore reanalyzed the catalytic activity of ODC G84R and found that it is rescued when the protein is purified in the presence of a reducing agent to mimic the reducing environment of the cytoplasm. This suggests that R84 may exert its neurological effects not through reducing ODC catalytic activity but through misregulation of its AZ1-mediated proteasomal degradation.
Collapse
Affiliation(s)
- X. Edward Zhou
- Department
of Structural Biology, Van Andel Institute, Grand Rapids, Michigan 49503, United States
| | - Chad R. Schultz
- Department
of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan 49546, United States
| | - Kelly Suino Powell
- Department
of Structural Biology, Van Andel Institute, Grand Rapids, Michigan 49503, United States
| | - Amy Henrickson
- Department
of Chemistry and Biochemistry, The University
of Lethbridge, Lethbridge, AB T1K3M4, Canada
| | - Jared Lamp
- Department
of Translational Neuroscience, Integrated Mass Spectrometry Unit,
College of Human Medicine, Michigan State
University, Grand
Rapids, Michigan 49503, United States
| | - Joseph S. Brunzelle
- Northwestern
University Synchrotron Research Center, Life Sciences Collaborative
Access Team, Northwestern University, Argonne, Illinois 60439, United States
| | - Borries Demeler
- Department
of Chemistry and Biochemistry, The University
of Lethbridge, Lethbridge, AB T1K3M4, Canada
- Department
of Chemistry and Biochemistry, The University
of Montana, Missoula, Montana 59812, United
States
| | - Irving E. Vega
- Department
of Translational Neuroscience, Integrated Mass Spectrometry Unit,
College of Human Medicine, Michigan State
University, Grand
Rapids, Michigan 49503, United States
| | - André S. Bachmann
- Department
of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan 49546, United States
| | - Karsten Melcher
- Department
of Structural Biology, Van Andel Institute, Grand Rapids, Michigan 49503, United States
| |
Collapse
|
3
|
Tran JU, Brown BL. Structural Basis for Allostery in PLP-dependent Enzymes. Front Mol Biosci 2022; 9:884281. [PMID: 35547395 PMCID: PMC9081730 DOI: 10.3389/fmolb.2022.884281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
Pyridoxal 5'-phosphate (PLP)-dependent enzymes are found ubiquitously in nature and are involved in a variety of biological pathways, from natural product synthesis to amino acid and glucose metabolism. The first structure of a PLP-dependent enzyme was reported over 40 years ago, and since that time, there is a steady wealth of structural and functional information revealed for a wide array of these enzymes. A functional mechanism that is gaining more appreciation due to its relevance in drug design is that of protein allostery, where binding of a protein or ligand at a distal site influences the structure, organization, and function at the active site. Here, we present a review of current structure-based mechanisms of allostery for select members of each PLP-dependent enzyme family. Knowledge of these mechanisms may have a larger potential for identifying key similarities and differences among enzyme families that can eventually be exploited for therapeutic development.
Collapse
Affiliation(s)
- Jenny U. Tran
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Breann L. Brown
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, United States
- Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, United States
| |
Collapse
|
4
|
Structural basis of binding and inhibition of ornithine decarboxylase by 1-amino-oxy-3-aminopropane. Biochem J 2021; 478:4137-4149. [PMID: 34796899 DOI: 10.1042/bcj20210647] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 11/17/2021] [Accepted: 11/19/2021] [Indexed: 11/17/2022]
Abstract
Ornithine decarboxylase (ODC) is the rate-limiting enzyme for the synthesis of polyamines (PAs). PAs are oncometabolites that are required for proliferation, and pharmaceutical ODC inhibition is pursued for the treatment of hyperproliferative diseases, including cancer and infectious diseases. The most potent ODC inhibitor is 1-amino-oxy-3-aminopropane (APA). A previous crystal structure of an ODC-APA complex indicated that APA non-covalently binds ODC and its cofactor pyridoxal 5-phosphate (PLP) and functions by competing with the ODC substrate ornithine for binding to the catalytic site. We have revisited the mechanism of APA binding and ODC inhibition through a new crystal structure of APA-bound ODC, which we solved at 2.49 Å resolution. The structure unambiguously shows the presence of a covalent oxime between APA and PLP in the catalytic site, which we confirmed in solution by mass spectrometry. The stable oxime makes extensive interactions with ODC but cannot be catabolized, explaining APA's high potency in ODC inhibition. In addition, we solved an ODC/PLP complex structure with citrate bound at the substrate-binding pocket. These two structures provide new structural scaffolds for developing more efficient pharmaceutical ODC inhibitors.
Collapse
|
5
|
Stevens LM, Kim G, Koromila T, Steele JW, McGehee J, Stathopoulos A, Stein DS. Light-dependent N-end rule-mediated disruption of protein function in Saccharomyces cerevisiae and Drosophila melanogaster. PLoS Genet 2021; 17:e1009544. [PMID: 33999957 PMCID: PMC8158876 DOI: 10.1371/journal.pgen.1009544] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 05/27/2021] [Accepted: 04/12/2021] [Indexed: 12/12/2022] Open
Abstract
Here we describe the development and characterization of the photo-N-degron, a peptide tag that can be used in optogenetic studies of protein function in vivo. The photo-N-degron can be expressed as a genetic fusion to the amino termini of other proteins, where it undergoes a blue light-dependent conformational change that exposes a signal for the class of ubiquitin ligases, the N-recognins, which mediate the N-end rule mechanism of proteasomal degradation. We demonstrate that the photo-N-degron can be used to direct light-mediated degradation of proteins in Saccharomyces cerevisiae and Drosophila melanogaster with fine temporal control. In addition, we compare the effectiveness of the photo-N-degron with that of two other light-dependent degrons that have been developed in their abilities to mediate the loss of function of Cactus, a component of the dorsal-ventral patterning system in the Drosophila embryo. We find that like the photo-N-degron, the blue light-inducible degradation (B-LID) domain, a light-activated degron that must be placed at the carboxy terminus of targeted proteins, is also effective in eliciting light-dependent loss of Cactus function, as determined by embryonic dorsal-ventral patterning phenotypes. In contrast, another previously described photosensitive degron (psd), which also must be located at the carboxy terminus of associated proteins, has little effect on Cactus-dependent phenotypes in response to illumination of developing embryos. These and other observations indicate that care must be taken in the selection and application of light-dependent and other inducible degrons for use in studies of protein function in vivo, but importantly demonstrate that N- and C-terminal fusions to the photo-N-degron and the B-LID domain, respectively, support light-dependent degradation in vivo. Much of what we know about biological processes has come from the analysis of mutants whose loss-of-function phenotypes provide insight into their normal functions. However, for genes that are required for viability and which have multiple functions in the life of a cell or organism one can only observe mutant phenotypes produced up to the time of death. Normal functions performed in wild-type individuals later than the time of death of mutants cannot be observed. In one approach to overcoming this limitation, a class of peptide degradation signals (degrons) have been developed, which when fused to proteins-of-interest, can target those proteins for degradation in response to various stimuli (temperature, chemical agents, co-expressed proteins, or light). Here we describe a new inducible degron (the photo-N-degron or PND), which when fused to the N-terminus of a protein, can induce N-end rule-mediated degradation in response to blue-light illumination and have validated its use in both yeast and Drosophila embryos. Moreover, using the Drosophila embryonic patterning protein Cactus, we show that like the PND, the previously-described B-LID domain, but not the previously-described photosensitive degron (psd), can produce detectable light-inducible phenotypes in Drosophila embryos that are consistent with the role of Cactus in dorsal-ventral patterning.
Collapse
Affiliation(s)
- Leslie M. Stevens
- Department of Molecular Biosciences and Institute for Molecular and Cellular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Goheun Kim
- Department of Molecular Biosciences and Institute for Molecular and Cellular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Theodora Koromila
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, United States of America
| | - John W. Steele
- Department of Molecular Biosciences and Institute for Molecular and Cellular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - James McGehee
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, United States of America
| | - Angelike Stathopoulos
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, United States of America
- * E-mail: (AS); (DSS)
| | - David S. Stein
- Department of Molecular Biosciences and Institute for Molecular and Cellular Biology, The University of Texas at Austin, Austin, Texas, United States of America
- * E-mail: (AS); (DSS)
| |
Collapse
|
6
|
Breton C, Furmanak T, Avitto AN, Smith MK, Latshaw C, Yan H, Greig JA, Wilson JM. Increasing the Specificity of AAV-Based Gene Editing through Self-Targeting and Short-Promoter Strategies. Mol Ther 2021; 29:1047-1056. [PMID: 33359790 DOI: 10.1016/j.ymthe.2020.12.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/07/2020] [Accepted: 12/18/2020] [Indexed: 12/28/2022] Open
Abstract
Our group previously used adeno-associated viral vectors (AAVs) to express an engineered meganuclease specific for a sequence in the PCSK9 gene (M2PCSK9), a clinical target for treating coronary heart disease. Upon testing this nuclease in non-human primates, we observed specific editing characterized by several insertions and deletions (indels) in the target sequence as well as indels in similar genomic sequences. We hypothesized that high nuclease expression increases off-target editing. Here, we reduced nuclease expression using two strategies. The first was a self-targeting strategy that involved inserting the M2PCSK9 target sequence into the AAV genome that expresses the nuclease and/or fusing the nuclease to a specific peptide to promote its degradation. The second strategy used a shortened version of the parental promoter to reduce nuclease expression. Mice administered with these second-generation AAV vectors showed reduced PCSK9 expression due to the nuclease on-target activity and reduced off-target activity. All vectors induced a stable reduction of PCSK9 in primates treated with self-targeting and short-promoter AAVs. Compared to the meganuclease-expressing parental AAV vector, we observed a significant reduction in off-target activity. In conclusion, we increased the in vivo nuclease specificity using a clinically relevant strategy that can be applied to other genome-editing nucleases.
Collapse
Affiliation(s)
- Camilo Breton
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Thomas Furmanak
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Alexa N Avitto
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Melanie K Smith
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Caitlin Latshaw
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hanying Yan
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jenny A Greig
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - James M Wilson
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| |
Collapse
|
7
|
Optimizing intracellular antibodies (intrabodies/nanobodies) to treat neurodegenerative disorders. Neurobiol Dis 2020; 134:104619. [DOI: 10.1016/j.nbd.2019.104619] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/05/2019] [Accepted: 09/19/2019] [Indexed: 01/27/2023] Open
|
8
|
Lopez‐Barbosa N, Ludwicki MB, DeLisa MP. Proteome editing using engineered proteins that hijack cellular quality control machinery. AIChE J 2019. [DOI: 10.1002/aic.16854] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Natalia Lopez‐Barbosa
- Robert F. Smith School of Chemical and Biomolecular Engineering Cornell University Ithaca New York
| | - Morgan B. Ludwicki
- Robert F. Smith School of Chemical and Biomolecular Engineering Cornell University Ithaca New York
| | - Matthew P. DeLisa
- Robert F. Smith School of Chemical and Biomolecular Engineering Cornell University Ithaca New York
- Nancy E. and Peter C. Meinig School of Biomedical Engineering Cornell University Ithaca New York
- Biochemistry, Molecular and Cell Biology Cornell University Ithaca New York
| |
Collapse
|
9
|
Lambertos A, Peñafiel R. Polyamine biosynthesis in Xenopus laevis: the xlAZIN2/xlODC2 gene encodes a lysine/ornithine decarboxylase. PLoS One 2019; 14:e0218500. [PMID: 31509528 PMCID: PMC6738921 DOI: 10.1371/journal.pone.0218500] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 08/26/2019] [Indexed: 11/29/2022] Open
Abstract
Ornithine decarboxylase (ODC) is a key enzyme in the biosynthesis of polyamines, organic cations that are implicated in many cellular processes. The enzyme is regulated at the post-translational level by an unusual system that includes antizymes (AZs) and antizyme inhibitors (AZINs). Most studies on this complex regulatory mechanism have been focused on human and rodent cells, showing that AZINs (AZIN1 and AZIN2) are homologues of ODC but devoid of enzymatic activity. Little is known about Xenopus ODC and its paralogues, in spite of the relevance of Xenopus as a model organism for biomedical research. We have used the information existing in different genomic databases to compare the functional properties of the amphibian ODC1, AZIN1 and AZIN2/ODC2, by means of transient transfection experiments of HEK293T cells. Whereas the properties of xlODC1 and xlAZIN1 were similar to those reported for their mammalian orthologues, the former catalyzing the decarboxylation of L-ornithine preferentially to that of L-lysine, xlAZIN2/xlODC2 showed important differences with respect to human and mouse AZIN2. xlAZIN2 did not behave as an antizyme inhibitor, but it rather acts as an authentic decarboxylase forming cadaverine, due to its higher affinity to L-lysine than to L-ornithine as substrate; so, in accordance with this, it should be named as lysine decarboxylase (LDC) or lysine/ornithine decarboxylase (LODC). In addition, AZ1 stimulated the degradation of xlAZIN2 by the proteasome, but the removal of the 21 amino acid C-terminal tail, with a sequence quite different to that of mouse or human ODC, made the protein resistant to degradation. Collectively, our results indicate that in Xenopus there is only one antizyme inhibitor (xlAZIN1) and two decarboxylases, xlODC1 and xlLDC, with clear preferences for L-ornithine and L-lysine, respectively.
Collapse
Affiliation(s)
- Ana Lambertos
- Department of Biochemistry and Molecular Biology B and Immunology, Faculty of Medicine, University of Murcia, Murcia, Spain
- Biomedical Research Institute of Murcia (IMIB), Murcia, Spain
| | - Rafael Peñafiel
- Department of Biochemistry and Molecular Biology B and Immunology, Faculty of Medicine, University of Murcia, Murcia, Spain
- Biomedical Research Institute of Murcia (IMIB), Murcia, Spain
- * E-mail:
| |
Collapse
|
10
|
Abstract
The ubiquitin proteasome system (UPS) degrades individual proteins in a highly regulated fashion and is responsible for the degradation of misfolded, damaged, or unneeded cellular proteins. During the past 20 years, investigators have established a critical role for the UPS in essentially every cellular process, including cell cycle progression, transcriptional regulation, genome integrity, apoptosis, immune responses, and neuronal plasticity. At the center of the UPS is the proteasome, a large and complex molecular machine containing a multicatalytic protease complex. When the efficiency of this proteostasis system is perturbed, misfolded and damaged protein aggregates can accumulate to toxic levels and cause neuronal dysfunction, which may underlie many neurodegenerative diseases. In addition, many cancers rely on robust proteasome activity for degrading tumor suppressors and cell cycle checkpoint inhibitors necessary for rapid cell division. Thus, proteasome inhibitors have proven clinically useful to treat some types of cancer, especially multiple myeloma. Numerous cellular processes rely on finely tuned proteasome function, making it a crucial target for future therapeutic intervention in many diseases, including neurodegenerative diseases, cystic fibrosis, atherosclerosis, autoimmune diseases, diabetes, and cancer. In this review, we discuss the structure and function of the proteasome, the mechanisms of action of different proteasome inhibitors, various techniques to evaluate proteasome function in vitro and in vivo, proteasome inhibitors in preclinical and clinical development, and the feasibility for pharmacological activation of the proteasome to potentially treat neurodegenerative disease.
Collapse
Affiliation(s)
- Tiffany A Thibaudeau
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
| | - David M Smith
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
| |
Collapse
|
11
|
Ferreira CR. The human phenotype of ornithine decarboxylase superactivity: A new syndrome. Am J Med Genet A 2018; 176:2545-2547. [DOI: 10.1002/ajmg.a.13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 11/05/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Carlos R. Ferreira
- National Human Genome Research Institute, National Institutes of Health; Bethesda Maryland
| |
Collapse
|
12
|
Abstract
The polyamines spermidine, spermine, and their precursor putrescine are organic polycations involved in various cellular processes and are absolutely essential for cellular proliferation. Because of their crucial function in the cell, their intracellular concentration must be maintained at optimal levels. To a large extent, this regulation is achieved through the activity of an autoregulatory loop that involves two proteins, antizyme (Az) and antizyme inhibitor (AzI), that regulate the first enzyme in polyamine biosynthesis, ornithine decarboxylase (ODC), and polyamine uptake activity in response to intracellular polyamine levels. In this Minireview, I will discuss what has been learned about the mechanism of Az expression and its physical interaction with both ODC and AzI in the regulation of polyamines.
Collapse
Affiliation(s)
- Chaim Kahana
- From the Department of Molecular Genetics, the Weizmann Institute of Science, Rehovot 76100, Israel
| |
Collapse
|
13
|
Bupp CP, Schultz CR, Uhl KL, Rajasekaran S, Bachmann AS. Novel de novo pathogenic variant in the ODC1 gene in a girl with developmental delay, alopecia, and dysmorphic features. Am J Med Genet A 2018; 176:2548-2553. [PMID: 30239107 DOI: 10.1002/ajmg.a.40523] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 08/03/2018] [Accepted: 08/04/2018] [Indexed: 11/09/2022]
Abstract
The ornithine decarboxylase 1 (ODC1) gene plays an important role in physiological and cell developmental processes including embryogenesis, organogenesis, and neoplastic cell growth. Here, we report an 32-month-old Caucasian female with a heterozygous de novo nonsense mutation in the ODC1 gene that leads to a premature abrogation of 14-aa residues at the ODC protein c-terminus. This is the first human case confirming similar symptoms observed in a transgenic ODC1 mouse model first described over 20 years ago. Phenotypic manifestations include macrosomia, macrocephaly, developmental delay, alopecia, spasticity, hypotonia, cutaneous vascular malformation, delayed visual maturation, and sensorineural hearing loss. We here describe for the first time a new pediatric disorder that is directly linked to a de novo pathogenic variant in the ODC1 gene. The ODC1 gene mutation (c.1342 A>T) was identified by whole-exome sequencing and confirmed by Sanger sequencing. Red blood cells obtained from our patient showed elevated ODC protein and polyamine levels compared to healthy controls. Our autosomal dominant patient who carries this gain-of-function ODC1 mutation may benefit from treatment with α-difluoromethylornithine, a well-tolerated, U.S. Food and Drug Administration (FDA). FDA-approved drug.
Collapse
Affiliation(s)
- Caleb P Bupp
- Medical Genetics, Spectrum Health and Helen DeVos Children's Hospital, Grand Rapids, Michigan.,Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan
| | - Chad R Schultz
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan
| | - Katie L Uhl
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan
| | - Surender Rajasekaran
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan.,Pediatric Critical Care Medicine, Helen DeVos Children's Hospital, Grand Rapids, Michigan
| | - André S Bachmann
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan
| |
Collapse
|
14
|
Protein degradation, the main hub in the regulation of cellular polyamines. Biochem J 2017; 473:4551-4558. [PMID: 27941031 DOI: 10.1042/bcj20160519c] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 09/20/2016] [Accepted: 09/22/2016] [Indexed: 12/15/2022]
Abstract
Ornithine decarboxylase (ODC) is the first and rate-limiting enzyme in the biosynthesis of polyamines, low-molecular-mass aliphatic polycations that are ubiquitously present in all living cells and are essential for fundamental cellular processes. Most cellular polyamines are bound, whereas the free pools, which regulate cellular functions, are subjected to tight regulation. The regulation of the free polyamine pools is manifested by modulation of their synthesis, catabolism, uptake and excretion. A central element that enables this regulation is the rapid degradation of key enzymes and regulators of these processes, particularly that of ODC. ODC degradation is part of an autoregulatory circuit that responds to the intracellular level of the free polyamines. The driving force of this regulatory circuit is a protein termed antizyme (Az). Az stimulates the degradation of ODC and inhibits polyamine uptake. Az acts as a sensor of the free intracellular polyamine pools as it is expressed via a polyamine-stimulated ribosomal frameshifting. Az binds to monomeric ODC subunits to prevent their reassociation into active homodimers and facilitates their ubiquitin-independent degradation by the 26S proteasome. In addition, through a yet unidentified mechanism, Az inhibits polyamine uptake. Interestingly, a protein, termed antizyme inhibitor (AzI) that is highly homologous with ODC, but retains no ornithine decarboxylating activity, seems to regulate cellular polyamines through its ability to negate Az. Overall, the degradation of ODC is a net result of interactions with regulatory proteins and possession of signals that mediate its ubiquitin-independent recognition by the proteasome.
Collapse
|
15
|
Joshi RG, Ratna Prabha C. Degrons of yeast and mammalian ornithine decarboxylase enzymes make potent combination for regulated targeted protein degradation. Appl Microbiol Biotechnol 2016; 101:2905-2917. [DOI: 10.1007/s00253-016-8023-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 11/16/2016] [Indexed: 10/20/2022]
|
16
|
Structural basis of Ornithine Decarboxylase inactivation and accelerated degradation by polyamine sensor Antizyme1. Sci Rep 2015; 5:14738. [PMID: 26443277 PMCID: PMC4595762 DOI: 10.1038/srep14738] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/07/2015] [Indexed: 11/18/2022] Open
Abstract
Ornithine decarboxylase (ODC) catalyzes the first and rate-limiting step of polyamine biosynthesis in humans. Polyamines are essential for cell proliferation and are implicated in cellular processes, ranging from DNA replication to apoptosis. Excessive accumulation of polyamines has a cytotoxic effect on cells and elevated level of ODC activity is associated with cancer development. To maintain normal cellular proliferation, regulation of polyamine synthesis is imposed by Antizyme1 (AZ1). The expression of AZ1 is induced by a ribosomal frameshifting mechanism in response to increased intracellular polyamines. AZ1 regulates polyamine homeostasis by inactivating ODC activity and enhancing its degradation. Here, we report the structure of human ODC in complex with N-terminally truncated AZ1 (cAZ1). The structure shows cAZ1 binding to ODC, which occludes the binding of a second molecule of ODC to form the active homodimer. Consequently, the substrate binding site is disrupted and ODC is inactivated. Structural comparison shows that the binding of cAZ1 to ODC causes a global conformational change of ODC and renders its C-terminal region flexible, therefore exposing this region for degradation by the 26S proteasome. Our structure provides the molecular basis for the inactivation of ODC by AZ1 and sheds light on how AZ1 promotes its degradation.
Collapse
|
17
|
Kim M. Pathogenic polyglutamine expansion length correlates with polarity of the flanking sequences. Mol Neurodegener 2014; 9:45. [PMID: 25377768 PMCID: PMC4237751 DOI: 10.1186/1750-1326-9-45] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 10/23/2014] [Indexed: 11/10/2022] Open
Abstract
Background Polyglutamine (polyQ) repeat expansion within coding sequence of a soluble protein is responsible for eight autosomal-dominant genetic neurodegenerative disorders. These disorders affect cerebellum, striatum, basal ganglia and other brain regions. The pathogenic polyQ-expansion threshold in these proteins varies from 32Q to 54Q. Understanding the reasons for variability in pathogenic polyQ threshold may provide insights into pathogenic mechanisms responsible for development of these disorders. Findings Here we established a quantitative correlation between the polarity of the flanking sequences and pathogenic polyQ-expansion threshold in this protein family. We introduced an “edge polarity index” (EPI) to quantify polarity effects of the flanking regions and established a strong correlation between EPI index and critical polyQ expansion length in this protein family. Based on this analysis we subdivided polyQ-expanded proteins into 2 groups – with strong and weak dependence of polyQ threshold on EPI index. The main difference between members of the first and the second group is a polarity profile of these proteins outside of polyQ and flanking regions. PolyQ proteins are known substrates for proteasome and most likely mechanistic explanation for the observed correlation is that proteasome may have an impaired ability to process continuous non-polar regions of proteins. Conclusions The proposed hypothesis provides a quantitative explanation for variability in pathogenic threshold among polyQ-expansion disorders, which we established to correlate with polarity of flanking regions. To explain these results we propose that proteasome is not efficient in processing continuous non-polar regions of proteins, resulting in release of undigested and partially digested fragments. If supported experimentally, our hypothesis may have wide implications for further understanding the pathogensis of polyglutamine expansion disorders.
Collapse
Affiliation(s)
- Meewhi Kim
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
| |
Collapse
|
18
|
Jagannathan S, Vad N, Vallabhapurapu S, Vallabhapurapu S, Anderson KC, Driscoll JJ. MiR-29b replacement inhibits proteasomes and disrupts aggresome+autophagosome formation to enhance the antimyeloma benefit of bortezomib. Leukemia 2014; 29:727-38. [PMID: 25234165 PMCID: PMC4360212 DOI: 10.1038/leu.2014.279] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 08/22/2014] [Accepted: 09/02/2014] [Indexed: 12/24/2022]
Abstract
Evading apoptosis is a cancer hallmark that remains a serious obstacle in current treatment approaches. Although proteasome inhibitors (PIs) have transformed management of multiple myeloma (MM), drug resistance emerges through induction of the aggresome+autophagy pathway as a compensatory protein clearance mechanism. Genome-wide profiling identified microRNAs (miRs) differentially expressed in bortezomib-resistant myeloma cells compared with drug-naive cells. The effect of individual miRs on proteasomal degradation of short-lived fluorescent reporter proteins was then determined in live cells. MiR-29b was significantly reduced in bortezomib-resistant cells as well as in cells resistant to second-generation PIs carfilzomib and ixazomib. Luciferase reporter assays demonstrated that miR-29b targeted PSME4 that encodes the proteasome activator PA200. Synthetically engineered miR-29b replacements impaired the growth of myeloma cells, patient tumor cells and xenotransplants. MiR-29b replacements also decreased PA200 association with proteasomes, reduced the proteasome's peptidase activity and inhibited ornithine decarboxylase turnover, a proteasome substrate degraded through ubiquitin-independent mechanisms. Immunofluorescence studies revealed that miR-29b replacements enhanced the bortezomib-induced accumulation of ubiquitinated proteins but did not reveal aggresome or autophagosome formation. Taken together, our study identifies miR-29b replacements as the first-in-class miR-based PIs that also disrupt the autophagy pathway and highlight their potential to synergistically enhance the antimyeloma effect of bortezomib.
Collapse
Affiliation(s)
- S Jagannathan
- 1] The Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, OH, USA [2] Division of Hematology and Oncology, The Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - N Vad
- 1] The Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, OH, USA [2] Division of Hematology and Oncology, The Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - S Vallabhapurapu
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - S Vallabhapurapu
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - K C Anderson
- Jerome Lipper Multiple Myeloma Center and LeBow Institute for Myeloma Therapeutics, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - J J Driscoll
- 1] The Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, OH, USA [2] Division of Hematology and Oncology, The Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, OH, USA [3] Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| |
Collapse
|
19
|
Morozov AV, Spasskaya DS, Karpov DS, Karpov VL. The central domain of yeast transcription factor Rpn4 facilitates degradation of reporter protein in human cells. FEBS Lett 2014; 588:3713-9. [PMID: 25157437 DOI: 10.1016/j.febslet.2014.08.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 08/08/2014] [Accepted: 08/13/2014] [Indexed: 11/29/2022]
Abstract
Despite high interest in the cellular degradation machinery and protein degradation signals (degrons), few degrons with universal activity along species have been identified. It has been shown that fusion of a target protein with a degradation signal from mammalian ornithine decarboxylase (ODC) induces fast proteasomal degradation of the chimera in both mammalian and yeast cells. However, no degrons from yeast-encoded proteins capable to function in mammalian cells were identified so far. Here, we demonstrate that the yeast transcription factor Rpn4 undergoes fast proteasomal degradation and its central domain can destabilize green fluorescent protein and Alpha-fetoprotein in human HEK 293T cells. Furthermore, we confirm the activity of this degron in yeast. Thus, the Rpn4 central domain is an effective interspecies degradation signal.
Collapse
Affiliation(s)
- A V Morozov
- W.A. Engelhardt Institute of Molecular Biology RAS, Moscow, Russia.
| | - D S Spasskaya
- W.A. Engelhardt Institute of Molecular Biology RAS, Moscow, Russia
| | - D S Karpov
- W.A. Engelhardt Institute of Molecular Biology RAS, Moscow, Russia
| | - V L Karpov
- W.A. Engelhardt Institute of Molecular Biology RAS, Moscow, Russia
| |
Collapse
|
20
|
Jia J, Delhon G, Tulman ER, Diel DG, Osorio FA, Wen X, Kutish GF, Rock DL. Novel gammaherpesvirus functions encoded by bovine herpesvirus 6 (bovine lymphotropic virus). J Gen Virol 2014; 95:1790-1798. [PMID: 24836671 DOI: 10.1099/vir.0.066951-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The genus Macavirus of the subfamily Gammaherpesvirinae includes viruses that infect lymphoid cells of domestic and wild ruminants and swine, causing asymptomatic latent infections in reservoir hosts. Here, we describe the genome of bovine herpesvirus 6 (BoHV-6), a macavirus ubiquitous in healthy cattle populations. The BoHV-6 genome exhibited architecture conserved in macaviruses, including a repetitive H-DNA region and unique 141 kbp L-DNA region predicted to encode 77 genes. BoHV-6 encoded, in variable genomic regions, a novel complement of genes relative to other characterized macaviruses, probably contributing to distinctive aspects of BoHV-6 infection biology and host range. Most notably, BoHV-6 encoded the first herpesviral protein (Bov2.b2) similar to cellular ornithine decarboxylase, an enzyme that catalyses the first and rate-limiting step in the biosynthesis of polyamines. Bov2.b2 conceivably mediates a novel mechanism by which BoHV-6 promotes cell-cycle-dependent viral replication.
Collapse
Affiliation(s)
- J Jia
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA.,Laboratory of Animal Infectious Disease and Microarray/Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Animal Veterinary Medicine, Sichuan Agricultural University, Yaan, Sichuan 625014, PR China
| | - G Delhon
- School of Veterinary Medicine & Biomedical Sciences and Nebraska Center for Virology, University of Nebraska, Lincoln, NE, USA
| | - E R Tulman
- Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, University of Connecticut, Storrs, CT, USA
| | - D G Diel
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA
| | - F A Osorio
- School of Veterinary Medicine & Biomedical Sciences and Nebraska Center for Virology, University of Nebraska, Lincoln, NE, USA
| | - X Wen
- Laboratory of Animal Infectious Disease and Microarray/Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Animal Veterinary Medicine, Sichuan Agricultural University, Yaan, Sichuan 625014, PR China
| | - G F Kutish
- Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, University of Connecticut, Storrs, CT, USA
| | - D L Rock
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA
| |
Collapse
|
21
|
Kim ER, Selyutina AA, Buldakov IA, Evdokimova V, Ovchinnikov LP, Sorokin AV. The proteolytic YB-1 fragment interacts with DNA repair machinery and enhances survival during DNA damaging stress. Cell Cycle 2013; 12:3791-803. [PMID: 24107631 PMCID: PMC3905071 DOI: 10.4161/cc.26670] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The Y-box binding protein 1 (YB-1) is a DNA/RNA-binding nucleocytoplasmic shuttling protein whose regulatory effect on many DNA and RNA-dependent events is determined by its localization in the cell. We have shown previously that YB-1 is cleaved by 20S proteasome between E219 and G220, and the truncated N-terminal YB-1 fragment accumulates in the nuclei of cells treated with DNA damaging drugs. We proposed that appearance of truncated YB-1 in the nucleus may predict multiple drug resistance. Here, we compared functional activities of the full-length and truncated YB-1 proteins and showed that the truncated form was more efficient in protecting cells against doxorubicin treatment. Both forms of YB-1 induced changes in expression of various genes without affecting those responsible for drug resistance. Interestingly, although YB-1 cleavage did not significantly affect its DNA binding properties, truncated YB-1 was detected in complexes with Mre11 and Rad50 under genotoxic stress conditions. We conclude that both full-length and truncated YB-1 are capable of protecting cells against DNA damaging agents, and the truncated form may have an additional function in DNA repair.
Collapse
Affiliation(s)
- Ekaterina R Kim
- Institute of Protein Research; Russian Academy of Sciences; Pushchino, Moscow Region, Russian Federation
| | - Anastasia A Selyutina
- Institute of Protein Research; Russian Academy of Sciences; Pushchino, Moscow Region, Russian Federation; University of Tartu; Institute of Technology; Tartu, Estonia
| | - Ilya A Buldakov
- Institute of Protein Research; Russian Academy of Sciences; Pushchino, Moscow Region, Russian Federation
| | - Valentina Evdokimova
- Institute of Protein Research; Russian Academy of Sciences; Pushchino, Moscow Region, Russian Federation; Department of Molecular Oncology; British Columbia Cancer Research Centre; Vancouver, British Columbia, Canada
| | - Lev P Ovchinnikov
- Institute of Protein Research; Russian Academy of Sciences; Pushchino, Moscow Region, Russian Federation
| | - Alexey V Sorokin
- Institute of Protein Research; Russian Academy of Sciences; Pushchino, Moscow Region, Russian Federation
| |
Collapse
|
22
|
Erales J, Coffino P. Ubiquitin-independent proteasomal degradation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:216-21. [PMID: 23684952 DOI: 10.1016/j.bbamcr.2013.05.008] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 10/26/2022]
Abstract
Most proteasome substrates are marked for degradation by ubiquitin conjugation, but some are targeted by other means. The properties of these exceptional cases provide insights into the general requirements for proteasomal degradation. Here the focus is on three ubiquitin-independent substrates that have been the subject of detailed study. These are Rpn4, a transcriptional regulator of proteasome homeostasis, thymidylate synthase, an enzyme required for production of DNA precursors and ornithine decarboxylase, the initial enzyme committed to polyamine biosynthesis. It can be inferred from these cases that proteasome association and the presence of an unstructured region are the sole prerequisites for degradation. Based on that inference, artificial substrates have been designed to test the proteasome's capacity for substrate processing and its limitations. Ubiquitin-independent substrates may in some cases be a remnant of the pre-ubiquitome world, but in other cases could provide optimized regulatory solutions. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
Collapse
Affiliation(s)
- Jenny Erales
- Department of Microbiology & Immunology, University of California, San Francisco, San Francisco, CA 94127, USA
| | | |
Collapse
|
23
|
Structural insight into DFMO resistant ornithine decarboxylase from Entamoeba histolytica: an inkling to adaptive evolution. PLoS One 2013; 8:e53397. [PMID: 23326423 PMCID: PMC3543441 DOI: 10.1371/journal.pone.0053397] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 11/28/2012] [Indexed: 11/19/2022] Open
Abstract
Background Polyamine biosynthetic pathway is a validated therapeutic target for large number of infectious diseases including cancer, giardiasis and African sleeping sickness, etc. α-Difluoromethylornithine (DFMO), a potent drug used for the treatment of African sleeping sickness is an irreversible inhibitor of ornithine decarboxylase (ODC), the first rate limiting enzyme of polyamine biosynthesis. The enzyme ODC of E. histolytica (EhODC) has been reported to exhibit resistance towards DFMO. Methodology/Principal Finding The basis for insensitivity towards DFMO was investigated by structural analysis of EhODC and conformational modifications at the active site. Here, we report cloning, purification and crystal structure determination of C-terminal truncated Entamoeba histolytica ornithine decarboxylase (EhODCΔ15). Structure was determined by molecular replacement method and refined to 2.8 Å resolution. The orthorhombic crystal exhibits P212121 symmetry with unit cell parameters a = 76.66, b = 119.28, c = 179.28 Å. Functional as well as evolutionary relations of EhODC with other ODC homologs were predicted on the basis of sequence analysis, phylogeny and structure. Conclusions/Significance We determined the tetrameric crystal structure of EhODCΔ15, which exists as a dimer in solution. Insensitivity towards DFMO is due to substitution of key substrate binding residues in active site pocket. Additionally, a few more substitutions similar to antizyme inhibitor (AZI), a non-functional homologue of ODCs, were identified in the active site. Here, we establish the fact that EhODC sequence has conserved PLP binding residues; in contrast few substrate binding residues are mutated similar to AZI. Further sequence analysis and structural studies revealed that EhODC may represent as an evolutionary bridge between active decarboxylase and inactive AZI.
Collapse
|
24
|
Production of functional soluble Dectin-1 glycoprotein using an IRES-linked destabilized-dihydrofolate reductase expression vector. PLoS One 2012; 7:e52785. [PMID: 23300776 PMCID: PMC3530475 DOI: 10.1371/journal.pone.0052785] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 11/21/2012] [Indexed: 11/30/2022] Open
Abstract
Dectin-1 (CLEC7A) is a C-type lectin receptor that binds to β-glucans found in fungal cell walls to act as a major pattern recognition receptor (PRR). Since β-glucans epitope is not present in human cells, we are of the opinion that Dectin-1 can have therapeutic functions against fungal infections. We thus set out to produce a soluble extracellular domain of murine Dectin-1 (called sDectin-1) in sufficient titers to facilitate such studies in mouse models. Since sDectin-1 has previously been shown to be glycosylated, we chose to produce this protein using Chinese Hamster Ovary (CHO) cells, a mammalian host cell line suitable for the high-titer production of recombinant glycoproteins. To ensure a high titer production of sDectin-1 and minimize the effects of gene fragmentation, we constructed a mammalian expression vector with a PEST-destabilized dhfr amplifiable marker downstream of an attenuated IRES element, which was in turn downstream of the sDectin-1 gene and a CMV IE promoter. Stably transfected and MTX-amplified cell pools were generated using this vector, and maximum sDectin-1 titers of 246 mg/l and 598 mg/l were obtained in shake flask batch culture and bioreactor fed-batch culture respectively. The purified recombinant sDectin-1 was shown to be glycosylated. Protein functionality was also demonstrated by its ability to bind to zymosan particles and to the cell wall of Saccharomyces cerevisiae. We describe for the first time the use of an attenuated IRES-linked PEST-destabilized dhfr amplifiable marker for the production of recombinant proteins with stably amplified cell pools. With our process, we reached the highest reported titer for producing recombinant proteins smaller than 50 kDa in cell pools. sDectin-1 protein produced is glycosylated and functional. This vector design can thus be used efficiently for the high-titer production of functional recombinant proteins.
Collapse
|
25
|
Abstract
SIGNIFICANCE Parasitic infections continue to be a major problem for global human health. Vaccines are practically not available and chemotherapy is highly unsatisfactory. One approach toward a novel antiparasitic drug development is to unravel pathways that may be suited as future targets. Parasitic organisms show a remarkable diversity with respect to the nature and functions of their main low-molecular-mass antioxidants and many of them developed pathways that do not have a counterpart in their mammalian hosts. RECENT ADVANCES Work of the last years disclosed the individual antioxidants employed by parasites and their distinct pathways. Entamoeba, Trichomonas, and Giardia directly use cysteine as main low-molecular-mass thiol but have divergent cysteine metabolisms. Malarial parasites rely exclusively on cysteine uptake and generate glutathione (GSH) as main free thiol as do metazoan parasites. Trypanosomes and Leishmania have a unique trypanothione-based thiol metabolism but employ individual mechanisms for their cysteine supply. In addition, some trypanosomatids synthesize ovothiol A and/or ascorbate. Various essential parasite enzymes such as trypanothione synthetase and trypanothione reductase in Trypanosomatids and the Schistosoma thioredoxin GSH reductase are currently intensively explored as drug target molecules. CRITICAL ISSUES Essentiality is a prerequisite but not a sufficient property of an enzyme to become a suited drug target. The availability of an appropriate in vivo screening system and many other factors are equally important. FUTURE DIRECTIONS The current organism-wide RNA-interference and proteome analyses are supposed to reveal many more interesting candidates for future drug development approaches directed against the parasite antioxidant defense systems.
Collapse
|
26
|
Morozov AV, Morozov VA, Astakhova TM, Timofeev AV, Karpov VL. DNA vaccine encoding α-fetoprotein fused with the ornithine decarboxylase degradation signal significantly suppresses the hepatocellular carcinoma growth in mice. Mol Biol 2012. [DOI: 10.1134/s0026893312030089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
27
|
Zou T, Rao JN, Liu L, Xiao L, Cui YH, Jiang Z, Ouyang M, Donahue JM, Wang JY. Polyamines inhibit the assembly of stress granules in normal intestinal epithelial cells regulating apoptosis. Am J Physiol Cell Physiol 2012; 303:C102-11. [PMID: 22555848 DOI: 10.1152/ajpcell.00009.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Polyamines regulate multiple signaling pathways and are implicated in many aspects of cellular functions, but the exact molecular processes governed by polyamines remain largely unknown. In response to environmental stress, repression of translation is associated with the assembly of stress granules (SGs) that contain a fraction of arrested mRNAs and are thought to function as mRNA storage. Here we show that polyamines modulate the assembly of SGs in normal intestinal epithelial cells (IECs) and that induced SGs following polyamine depletion are implicated in the protection of IECs against apoptosis. Increasing the levels of cellular polyamines by ectopic overexpression of the ornithine decarboxylase gene decreased cytoplasmic levels of SG-signature constituent proteins eukaryotic initiation factor 3b and T-cell intracellular antigen-1 (TIA-1)-related protein and repressed the assembly of SGs induced by exposure to arsenite-induced oxidative stress. In contrast, depletion of cellular polyamines by inhibiting ornithine decarboxylase with α-difluoromethylornithine increased cytoplasmic eukaryotic initiation factor 3b and TIA-1 related protein abundance and enhanced arsenite-induced SG assembly. Polyamine-deficient cells also exhibited an increase in resistance to tumor necrosis factor-α/cycloheximide-induced apoptosis, which was prevented by inhibiting SG formation with silencing SG resident proteins Sort1 and TIA-1. These results indicate that the elevation of cellular polyamines represses the assembly of SGs in normal IECs and that increased SGs in polyamine-deficient cells are crucial for increased resistance to apoptosis.
Collapse
Affiliation(s)
- Tongtong Zou
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Butler DC, McLear JA, Messer A. Engineered antibody therapies to counteract mutant huntingtin and related toxic intracellular proteins. Prog Neurobiol 2012; 97:190-204. [PMID: 22120646 PMCID: PMC3908675 DOI: 10.1016/j.pneurobio.2011.11.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 11/03/2011] [Accepted: 11/08/2011] [Indexed: 02/07/2023]
Abstract
The engineered antibody approach to Huntington's disease (HD) therapeutics is based on the premise that significantly lowering the levels of the primary misfolded mutant protein will reduce abnormal protein interactions and direct toxic effects of the misfolded huntingtin (HTT). This will in turn reduce the pathologic stress on cells, and normalize intrinsic proteostasis. Intracellular antibodies (intrabodies) are single-chain (scFv) and single-domain (dAb; nanobody) variable fragments that can retain the affinity and specificity of full-length antibodies, but can be selected and engineered as genes. Functionally, they represent a protein-based approach to the problem of aberrant mutant protein folding, post-translational modifications, protein-protein interactions, and aggregation. Several intrabodies that bind on either side of the expanded polyglutamine tract of mutant HTT have been reported to improve the mutant phenotype in cell and organotypic cultures, fruit flies, and mice. Further refinements to the difficult challenges of intraneuronal delivery, cytoplasmic folding, and long-term efficacy are in progress. This review covers published studies and emerging approaches on the choice of targets, selection and engineering methods, gene and protein delivery options, and testing of candidates in cell and animal models. The resultant antibody fragments can be used as direct therapeutics and as target validation/drug discovery tools for HD, while the technology is also applicable to a wide range of neurodegenerative and other diseases that are triggered by toxic proteins.
Collapse
Affiliation(s)
- David C. Butler
- Wadsworth Center, New York State Dept. of Health, Albany, NY, United States, 12208
| | | | - Anne Messer
- Wadsworth Center, New York State Dept. of Health, Albany, NY, United States, 12208
- Department of Biomedical Sciences, School of Public Health, University at Albany, SUNY, NY 12201
| |
Collapse
|
29
|
Ng SK. Generation of high-expressing cells by methotrexate amplification of destabilized dihydrofolate reductase selection marker. Methods Mol Biol 2012; 801:161-172. [PMID: 21987253 DOI: 10.1007/978-1-61779-352-3_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A method combining the use of a destabilized dihydrofolate reductase (DHFR) selection marker with methotrexate (MTX) amplification to generate high-expressing cells is described here. The selection marker expression is weakened with the use of the murine ornithine decarboxylase PEST region and AU-rich element to target the DHFR protein and mRNA, respectively, for degradation in the cell. Cells that produce higher levels of DHFR protein, and the adjoining recombinant protein gene, can compensate for the more rapid turnover of the DHFR protein and survive the selection process. This effect can complement MTX amplification to reduce the amount of MTX and shorten the time needed to generate a high-expressing clone. The gene of interest is first inserted into an expression vector that contains a destabilized DHFR selection marker. The resulting expression vector is then linearized and transfected into suspension CHO-DG44 cells. Selection is performed by culturing the cells in a selection medium lacking hypoxanthine and thymidine. Low concentrations of MTX are then used to amplify the transfected genes for increased protein expression. A single cell cloning protocol is also described. This can be used after each stage of MTX amplification to isolate high-expressing clones that are also consistent producers over longer culture periods.
Collapse
Affiliation(s)
- Say Kong Ng
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore.
| |
Collapse
|
30
|
Butler DC, Messer A. Bifunctional anti-huntingtin proteasome-directed intrabodies mediate efficient degradation of mutant huntingtin exon 1 protein fragments. PLoS One 2011; 6:e29199. [PMID: 22216210 PMCID: PMC3245261 DOI: 10.1371/journal.pone.0029199] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 11/22/2011] [Indexed: 12/31/2022] Open
Abstract
Huntington's disease (HD) is a fatal autosomal dominant neurodegenerative disorder caused by a trinucleotide (CAG)(n) repeat expansion in the coding sequence of the huntingtin gene, and an expanded polyglutamine (>37Q) tract in the protein. This results in misfolding and accumulation of huntingtin protein (htt), formation of neuronal intranuclear and cytoplasmic inclusions, and neuronal dysfunction/degeneration. Single-chain Fv antibodies (scFvs), expressed as intrabodies that bind htt and prevent aggregation, show promise as immunotherapeutics for HD. Intrastriatal delivery of anti-N-terminal htt scFv-C4 using an adeno-associated virus vector (AAV2/1) significantly reduces the size and number of aggregates in HDR6/1 transgenic mice; however, this protective effect diminishes with age and time after injection. We therefore explored enhancing intrabody efficacy via fusions to heterologous functional domains. Proteins containing a PEST motif are often targeted for proteasomal degradation and generally have a short half life. In ST14A cells, fusion of the C-terminal PEST region of mouse ornithine decarboxylase (mODC) to scFv-C4 reduces htt exon 1 protein fragments with 72 glutamine repeats (httex1-72Q) by ~80-90% when compared to scFv-C4 alone. Proteasomal targeting was verified by either scrambling the mODC-PEST motif, or via proteasomal inhibition with epoxomicin. For these constructs, the proteasomal degradation of the scFv intrabody proteins themselves was reduced<25% by the addition of the mODC-PEST motif, with or without antigens. The remaining intrabody levels were amply sufficient to target N-terminal httex1-72Q protein fragment turnover. Critically, scFv-C4-PEST prevents aggregation and toxicity of httex1-72Q fragments at significantly lower doses than scFv-C4. Fusion of the mODC-PEST motif to intrabodies is a valuable general approach to specifically target toxic antigens to the proteasome for degradation.
Collapse
Affiliation(s)
- David C. Butler
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, University at Albany, Albany, New York, United States of America
| | - Anne Messer
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, University at Albany, Albany, New York, United States of America
- * E-mail:
| |
Collapse
|
31
|
Assessment of hypoxia inducible factor levels in cancer cell lines upon hypoxic induction using a novel reporter construct. PLoS One 2011; 6:e27460. [PMID: 22132102 PMCID: PMC3223176 DOI: 10.1371/journal.pone.0027460] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 10/17/2011] [Indexed: 01/04/2023] Open
Abstract
Hypoxia Inducible Factor (HIF) signaling pathway is important for tumor cells with limited oxygen supplies, as it is shown to be involved in the process of proliferation and angiogenesis. Given its pivotal role in cancer biology, robust assays for tracking changes in HIF expression are necessary for understanding its regulation in cancer as well as developing therapies that target HIF signaling. Here we report a novel HIF reporter construct containing tandem repeats of minimum HIF binding sites upstream of eYFP coding sequence. We show that the reporter construct has an excellent signal to background ratio and the reporter activity is HIF dependent and directly correlates with HIF protein levels. By utilizing this new construct, we assayed HIF activity levels in different cancer cell lines cultured in various degrees of hypoxia. This analysis reveals a surprising cancer cell line specific variation of HIF activity in the same level of hypoxia. We further show that in two cervical cancer cell lines, ME180 and HeLa, the different HIF activity levels observed correlate with the levels of hsp90, a cofactor that protects HIF against VHL-independent degradation. This novel HIF reporter construct serves as a tool to rapidly define HIF activity levels and therefore the therapeutic capacity of potential HIF repressors in individual cancers.
Collapse
|
32
|
Liu YC, Hsu DH, Huang CL, Liu YL, Liu GY, Hung HC. Determinants of the differential antizyme-binding affinity of ornithine decarboxylase. PLoS One 2011; 6:e26835. [PMID: 22073206 PMCID: PMC3207831 DOI: 10.1371/journal.pone.0026835] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 10/05/2011] [Indexed: 01/26/2023] Open
Abstract
Ornithine decarboxylase (ODC) is a ubiquitous enzyme that is conserved in all species from bacteria to humans. Mammalian ODC is degraded by the proteasome in a ubiquitin-independent manner by direct binding to the antizyme (AZ). In contrast, Trypanosoma brucei ODC has a low binding affinity toward AZ. In this study, we identified key amino acid residues that govern the differential AZ binding affinity of human and Trypanosoma brucei ODC. Multiple sequence alignments of the ODC putative AZ-binding site highlights several key amino acid residues that are different between the human and Trypanosoma brucei ODC protein sequences, including residue 119, 124,125, 129, 136, 137 and 140 (the numbers is for human ODC). We generated a septuple human ODC mutant protein where these seven bases were mutated to match the Trypanosoma brucei ODC protein sequence. The septuple mutant protein was much less sensitive to AZ inhibition compared to the WT protein, suggesting that these amino acid residues play a role in human ODC-AZ binding. Additional experiments with sextuple mutants suggest that residue 137 plays a direct role in AZ binding, and residues 119 and 140 play secondary roles in AZ binding. The dissociation constants were also calculated to quantify the affinity of the ODC-AZ binding interaction. The Kd value for the wild type ODC protein-AZ heterodimer ([ODC_WT]-AZ) is approximately 0.22 μM, while the Kd value for the septuple mutant-AZ heterodimer ([ODC_7M]-AZ) is approximately 12.4 μM. The greater than 50-fold increase in [ODC_7M]-AZ binding affinity shows that the ODC-7M enzyme has a much lower binding affinity toward AZ. For the mutant proteins ODC_7M(-Q119H) and ODC_7M(-V137D), the Kd was 1.4 and 1.2 μM, respectively. These affinities are 6-fold higher than the WT_ODC Kd, which suggests that residues 119 and 137 play a role in AZ binding.
Collapse
Affiliation(s)
- Yen-Chin Liu
- Department of Life Sciences and Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung, Taiwan
| | - Den-Hua Hsu
- Department of Life Sciences and Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung, Taiwan
| | - Chi-Liang Huang
- Department of Life Sciences and Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung, Taiwan
| | - Yi-Liang Liu
- Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan
- Division of Allergy, Immunology, and Rheumatology, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Guang-Yaw Liu
- Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan
- Division of Allergy, Immunology, and Rheumatology, Chung Shan Medical University Hospital, Taichung, Taiwan
- * E-mail: (HCH); (GYL)
| | - Hui-Chih Hung
- Department of Life Sciences and Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung, Taiwan
- Agricultural Biotechnology Center, National Chung Hsing University, Taichung, Taiwan
- * E-mail: (HCH); (GYL)
| |
Collapse
|
33
|
Hsieh JY, Yang JY, Lin CL, Liu GY, Hung HC. Minimal antizyme peptide fully functioning in the binding and inhibition of ornithine decarboxylase and antizyme inhibitor. PLoS One 2011; 6:e24366. [PMID: 21931692 PMCID: PMC3170320 DOI: 10.1371/journal.pone.0024366] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 08/08/2011] [Indexed: 01/10/2023] Open
Abstract
Antizyme (AZ) is a protein with 228 amino acid residues that regulates ornithine decarboxylase (ODC) by binding to ODC and dissociating its homodimer, thus inhibiting its enzyme activity. Antizyme inhibitor (AZI) is homologous to ODC, but has a higher affinity than ODC for AZ. In this study, we quantified the biomolecular interactions between AZ and ODC as well as AZ and AZI to identify functional AZ peptides that could bind to ODC and AZI and inhibit their function as efficiently as the full-length AZ protein. For these AZ peptides, the inhibitory ability of AZ_95-228 was similar to that of AZ_WT. Furthermore, AZ_95-176 displayed an inhibition (IC50: 0.20 µM) similar to that of AZ-95-228 (IC50: 0.16 µM), even though a large segment spanning residues 177–228 was deleted. However, further deletion of AZ_95-176 from either the N-terminus or the C-terminus decreased its ability to inhibit ODC. The AZ_100-176 and AZ_95-169 peptides displayed a noteworthy decrease in ability to inhibit ODC, with IC50 values of 0.43 and 0.37 µM, respectively. The AZ_95-228, AZ_100-228 and AZ_95-176 peptides had IC50 values comparable to that of AZ_WT and formed AZ-ODC complexes with Kd,AZ-ODC values of 1.5, 5.3 and 5.6 µM, respectively. Importantly, our data also indicate that AZI can rescue AZ peptide-inhibited ODC enzyme activity and that it can bind to AZ peptides with a higher affinity than ODC. Together, these data suggest that these truncated AZ proteins retain their AZI-binding ability. Thus, we suggest that AZ_95-176 is the minimal AZ peptide that is fully functioning in the binding of ODC and AZI and inhibition of their function.
Collapse
Affiliation(s)
- Ju-Yi Hsieh
- Department of Life Sciences and Institute of Bioinformatics, National Chung Hsing University, Taichung, Taiwan
| | - Jung-Yen Yang
- National Nano Device Laboratories and Department of Electrical Engineering, National Chiao Tung University, Hsinchu, Taiwan
| | - Chih-Li Lin
- Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Guang-Yaw Liu
- Institute of Microbiology & Immunology, Chung Shan Medical University, and Division of Allergy, Immunology, and Rheumatology, Chung Shan Medical University Hospital, Taichung, Taiwan
- * E-mail: (H-CH); (G-YL)
| | - Hui-Chih Hung
- Department of Life Sciences and Institute of Bioinformatics, National Chung Hsing University, Taichung, Taiwan
- Agricultural Biotechnology Center, National Chung Hsing University, Taichung, Taiwan
- * E-mail: (H-CH); (G-YL)
| |
Collapse
|
34
|
Morozov AV, Timofeev AV, Morozov VA, Karpov VL. Availability and canonical positioning of key amino acids of ornithine-decarboxylase degron is insufficient for alpha-fetoprotein degradation. Mol Biol 2011. [DOI: 10.1134/s0026893311030101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
35
|
Lee NKL, MacLean HE. Polyamines, androgens, and skeletal muscle hypertrophy. J Cell Physiol 2011; 226:1453-60. [PMID: 21413019 DOI: 10.1002/jcp.22569] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The naturally occurring polyamines, spermidine, spermine, and their precursor putrescine, play indispensible roles in both prokaryotic and eukaryotic cells, from basic DNA synthesis to regulation of cell proliferation and differentiation. The rate-limiting polyamine biosynthetic enzymes, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase, are essential for mammalian development, with knockout of the genes encoding these enzymes, Odc1 and Amd1, causing early embryonic lethality in mice. In muscle, the involvement of polyamines in muscle hypertrophy is suggested by the concomitant increase in cardiac and skeletal muscle mass and polyamine levels in response to anabolic agents including β-agonists. In addition to β-agonists, androgens, which increase skeletal mass and strength, have also been shown to stimulate polyamine accumulation in a number of tissues. In muscle, androgens act via the androgen receptor to regulate expression of polyamine biosynthetic enzyme genes, including Odc1 and Amd1, which may be one mechanism via which androgens promote muscle growth. This review outlines the role of polyamines in proliferation and hypertrophy, and explores their possible actions in mediating the anabolic actions of androgens in muscle.
Collapse
Affiliation(s)
- Nicole K L Lee
- Department of Medicine, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia
| | | |
Collapse
|
36
|
Abstract
Genetic lesions in the polyamine biosynthetic pathway of Leishmania donovani, the causal agent of visceral leishmaniasis, are conditionally lethal mutations that render the insect vector form of the parasite auxotrophic for polyamines. Recently, we have demonstrated that a Δodc L. donovani null mutant lacking ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, was profoundly compromised in its ability to infect mice, indicating that ODC is essential for the infectious mammalian stage of the parasite and further validating the enzyme as a possible drug target. To assess whether other components of the polyamine biosynthetic pathway were also essential for parasite virulence, a cell line deficient in spermidine synthase (SPDSYN), the enzyme that converts putrescine to spermidine, was created by double-targeted gene replacement within a virulent L. donovani background. This Δspdsyn strain was auxotrophic for polyamines, required spermidine for growth in its insect vector form, and was adversely impacted in its ability to infect mice. These findings establish that SPDSYN, like ODC, is essential for maintaining a robust infection in mammals and indicate that pharmacologic inhibition of SPDSYN, and perhaps all components of the polyamine biosynthetic pathway, is a valid therapeutic strategy for the treatment of visceral and, potentially, other forms of leishmaniasis.
Collapse
|
37
|
Gödderz D, Schäfer E, Palanimurugan R, Dohmen RJ. The N-Terminal Unstructured Domain of Yeast ODC Functions as a Transplantable and Replaceable Ubiquitin-Independent Degron. J Mol Biol 2011; 407:354-67. [DOI: 10.1016/j.jmb.2011.01.051] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 01/18/2011] [Accepted: 01/27/2011] [Indexed: 01/01/2023]
|
38
|
Henderson A, Erales J, Hoyt MA, Coffino P. Dependence of proteasome processing rate on substrate unfolding. J Biol Chem 2011; 286:17495-502. [PMID: 21454622 DOI: 10.1074/jbc.m110.212027] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein degradation by eukaryotic proteasomes is a multi-step process involving substrate recognition, ATP-dependent unfolding, translocation into the proteolytic core particle, and finally proteolysis. To date, most investigations of proteasome function have focused on the first and the last steps in this process. Here we examine the relationship between the stability of a folded protein domain and its degradation rate. Test proteins were targeted to the proteasome independently of ubiquitination by directly tethering them to the protease. Degradation kinetics were compared for test protein pairs whose stability was altered by either point mutation or ligand binding, but were otherwise identical. In both intact cells and in reactions using purified proteasomes and substrates, increased substrate stability led to an increase in substrate turnover time. The steady-state time for degradation ranged from ∼5 min (dihydrofolate reductase) to 40 min (I27 domain of titin). ATP turnover was 110/min./proteasome, and was not markedly changed by substrate. Proteasomes engage tightly folded substrates in multiple iterative rounds of ATP hydrolysis, a process that can be rate-limiting for degradation.
Collapse
Affiliation(s)
- Allen Henderson
- Department of Microbiology & Immunology, University of California, San Francisco, San Francisco, California 94127, USA
| | | | | | | |
Collapse
|
39
|
Jungbluth M, Renicke C, Taxis C. Targeted protein depletion in Saccharomyces cerevisiae by activation of a bidirectional degron. BMC SYSTEMS BIOLOGY 2010; 4:176. [PMID: 21190544 PMCID: PMC3024245 DOI: 10.1186/1752-0509-4-176] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 12/29/2010] [Indexed: 12/04/2022]
Abstract
Background Tools for in vivo manipulation of protein abundance or activity are highly beneficial for life science research. Protein stability can be efficiently controlled by conditional degrons, which induce target protein degradation at restrictive conditions. Results We used the yeast Saccharomyces cerevisiae for development of a conditional, bidirectional degron to control protein stability, which can be fused to the target protein N-terminally, C-terminally or placed internally. Activation of the degron is achieved by cleavage with the tobacco etch virus (TEV) protease, resulting in quick proteolysis of the target protein. We found similar degradation rates of soluble substrates using destabilization by the N- or C-degron. C-terminal tagging of essential yeast proteins with the bidirectional degron resulted in deletion-like phenotypes at non-permissive conditions. Developmental process-specific mutants were created by N- or C-terminal tagging of essential proteins with the bidirectional degron in combination with sporulation-specific production of the TEV protease. Conclusions We developed a system to influence protein abundance and activity genetically, which can be used to create conditional mutants, to regulate the fate of single protein domains or to design artificial regulatory circuits. Thus, this method enhances the toolbox to manipulate proteins in systems biology approaches considerably.
Collapse
Affiliation(s)
- Marc Jungbluth
- Department of Genetics, Philipps-Universität Marburg, Germany
| | | | | |
Collapse
|
40
|
Post-transcriptional regulation of MEK-1 by polyamines through the RNA-binding protein HuR modulating intestinal epithelial apoptosis. Biochem J 2010; 426:293-306. [PMID: 20001965 DOI: 10.1042/bj20091459] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
MEK-1 [MAPK (mitogen-activated protein kinase) kinase-1] is an important signal transducing enzyme that is implicated in many aspects of cellular functions. In the present paper, we report that cellular polyamines regulate MEK-1 expression at the post-transcriptional level through the RNA-binding protein HuR (Hu-antigen R) in IECs (intestinal epithelial cells). Decreasing the levels of cellular polyamines by inhibiting ODC (ornithine decarboxylase) stabilized MEK-1 mRNA and promoted its translation through enhancement of the interaction between HuR and the 3'-untranslated region of MEK-1 mRNA, whereas increasing polyamine levels by ectopic ODC overexpression destabilized the MEK-1 transcript and repressed its translation by reducing the abundance of HuR-MEK-1 mRNA complex; neither intervention changed MEK-1 gene transcription via its promoter. HuR silencing rendered the MEK-1 mRNA unstable and inhibited its translation, thus preventing increases in MEK-1 mRNA and protein in polyamine-deficient cells. Conversely, HuR overexpression increased MEK-1 mRNA stability and promoted its translation. Inhibition of MEK-1 expression by MEK-1 silencing or HuR silencing prevented the increased resistance of polyamine-deficient cells to apoptosis. Moreover, HuR overexpression did not protect against apoptosis if MEK-1 expression was silenced. These results indicate that polyamines destabilize the MEK-1 mRNA and repress its translation by inhibiting the association between HuR and the MEK-1 transcript. Our findings indicate that MEK-1 is a key effector of the HuR-elicited anti-apoptotic programme in IECs.
Collapse
|
41
|
Abstract
The polyamines are essential for a variety of functions in the mammalian cell. Although their specific effects have not been fully elucidated, it is clear that the cellular polyamines have to be kept within certain levels for normal cell function. Polyamine homoeostasis in mammalian cells is achieved by a complex network of regulatory mechanisms affecting synthesis and degradation, as well as membrane transport of polyamines. The two key enzymes in the polyamine biosynthetic pathway, ODC (ornithine decarboxylase) and AdoMetDC (S-adenosylmethionine decarboxylase), are strongly regulated by feedback mechanisms at several levels, including transcriptional, translational and post-translational. Some of these mechanisms have been shown to be truly unique and include upstream reading frames and ribosomal frameshifting, as well as ubiquitin-independent proteasomal degradation. SSAT (spermidine/spermine N1-acetyltransferase), which is a crucial enzyme for degradation and efflux of polyamines, is also highly regulated by polyamines. A cellular excess of polyamines rapidly induces SSAT, resulting in increased degradation/efflux of the polyamines. The polyamines appear to induce both transcription and translation of the SSAT mRNA. However, the major part of the polyamine-induced increase in SSAT is caused by a marked stabilization of the enzyme against degradation by the 26S proteasome. In addition, active transport of extracellular polyamines into the cell contributes to cellular polyamine homoeostasis. Depletion of cellular polyamines rapidly induces an increased uptake of exogenous polyamines, whereas an excess of polyamines down-regulates the polyamine transporter(s). However, the protein(s) involved in polyamine transport and the exact mechanisms by which the polyamines regulate the transporter(s) are not yet known.
Collapse
|
42
|
Liu L, Rao JN, Zou T, Xiao L, Wang PY, Turner DJ, Gorospe M, Wang JY. Polyamines regulate c-Myc translation through Chk2-dependent HuR phosphorylation. Mol Biol Cell 2009; 20:4885-98. [PMID: 19812253 DOI: 10.1091/mbc.e09-07-0550] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
All mammalian cells depend on polyamines for normal growth and proliferation, but the exact roles of polyamines at the molecular level remain largely unknown. The RNA-binding protein HuR modulates the stability and translation of many target mRNAs. Here, we show that in rat intestinal epithelial cells (IECs), polyamines enhanced HuR association with the 3'-untranslated region of the c-Myc mRNA by increasing HuR phosphorylation by Chk2, in turn promoting c-Myc translation. Depletion of cellular polyamines inhibited Chk2 and reduced the affinity of HuR for c-Myc mRNA; these effects were completely reversed by addition of the polyamine putrescine or by Chk2 overexpression. In cells with high content of cellular polyamines, HuR silencing or Chk2 silencing reduced c-Myc translation and c-Myc expression levels. Our findings demonstrate that polyamines regulate c-Myc translation in IECs through HuR phosphorylation by Chk2 and provide new insight into the molecular functions of cellular polyamines.
Collapse
Affiliation(s)
- Lan Liu
- Cell Biology Group, Department of Surgery, and Department of Pathology, University of Maryland School of Medicine and Baltimore Veterans Affairs Medical Center, Baltimore, MD 21201, USA
| | | | | | | | | | | | | | | |
Collapse
|
43
|
Kahana C. Antizyme and antizyme inhibitor, a regulatory tango. Cell Mol Life Sci 2009; 66:2479-88. [PMID: 19399584 PMCID: PMC11115672 DOI: 10.1007/s00018-009-0033-3] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 03/29/2009] [Accepted: 04/07/2009] [Indexed: 12/14/2022]
Abstract
The polyamines are small basic molecules essential for cellular proliferation and viability. An autoregulatory circuit that responds to the intracellular level of polyamines regulates their production. In the center of this circuit is a family of small proteins termed antizymes. Antizymes are themselves regulated at the translational level by the level of polyamines. Antizymes bind ornithine decarboxylase (ODC) subunits and target them to ubiquitin-independent degradation by the 26S proteasome. In addition, antizymes inhibit polyamine transport across the plasma membrane via an as yet unresolved mechanism. Antizymes may also interact with and target degradation of other growth-regulating proteins. An inactive ODC-related protein termed antizyme inhibitor regulates polyamine metabolism by negating antizyme functions. The ability of antizymes to degrade ODC, inhibit polyamine uptake and consequently suppress cellular proliferation suggests that they act as tumor suppressors, while the ability of antizyme inhibitors to negate antizyme function indicates their growth-promoting and oncogenic potential.
Collapse
Affiliation(s)
- Chaim Kahana
- Department of Molecular Genetics, The Weizmann Institute of Science, 76100 Rehovot, Israel.
| |
Collapse
|
44
|
Abstract
A chicken embryo cDNA library was screened with a mouse probe for ornithine decarboxylase (ODC) and 14 positively hybridizing clones isolated. The longest of these (1.7 kb) was sub-cloned and sequenced. It is estimated that the clone comprises approximately 98% of the coding region for chicken ODC. The DNA sequence shows 78% identity with the human ODC cDNA sequence and the deduced amino acid sequence is almost 90% homologous to mouse and human. Both the peptide and cDNA sequences show interesting potential regulatory features which are discussed here.
Collapse
Affiliation(s)
- R Johnson
- AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian, UK
| | | |
Collapse
|
45
|
Antizyme 3 inhibits polyamine uptake and ornithine decarboxylase (ODC) activity, but does not stimulate ODC degradation. Biochem J 2009; 419:99-103, 1 p following 103. [PMID: 19076071 DOI: 10.1042/bj20081874] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Azs (antizymes) are small polyamine-induced proteins that function as feedback regulators of cellular polyamine homoeostasis. They bind to transient ODC (ornithine decarboxylase) monomeric subunits, resulting in inhibition of ODC activity and targeting ODC to ubiquitin-independent proteasomal degradation. Az3 is a mammalian Az isoform expressed exclusively in testicular germ cells and therefore considered as a potential regulator of polyamines during spermatogenesis. We show here that, unlike Az1 and Az2, which efficiently inhibit ODC activity and stimulate its proteasomal degradation, Az3 poorly inhibits ODC activity and fails to promote ODC degradation. Furthermore, Az3 actually stabilizes ODC, probably by protecting it from the effect of Az1. Its inhibitory effect is revealed only when it is present in excess compared with ODC. All three Azs efficiently inhibit the ubiquitin-dependent degradation of AzI (Az inhibitor) 1 and 2. Az3, similar to Az1 and Az2, efficiently inhibits polyamine uptake. The potential significance of the differential behaviour of Az3 is discussed.
Collapse
|
46
|
Tank EMH, True HL. Disease-associated mutant ubiquitin causes proteasomal impairment and enhances the toxicity of protein aggregates. PLoS Genet 2009; 5:e1000382. [PMID: 19214209 PMCID: PMC2633047 DOI: 10.1371/journal.pgen.1000382] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Accepted: 01/14/2009] [Indexed: 11/18/2022] Open
Abstract
Protein homeostasis is critical for cellular survival and its dysregulation has been implicated in Alzheimer's disease (AD) and other neurodegenerative disorders. Despite the growing appreciation of the pathogenic mechanisms involved in familial forms of AD, much less is known about the sporadic cases. Aggregates found in both familial and sporadic AD often include proteins other than those typically associated with the disease. One such protein is a mutant form of ubiquitin, UBB+1, a frameshift product generated by molecular misreading of a wild-type ubiquitin gene. UBB+1 has been associated with multiple disorders. UBB+1 cannot function as a ubiquitin molecule, and it is itself a substrate for degradation by the ubiquitin/proteasome system (UPS). Accumulation of UBB+1 impairs the proteasome system and enhances toxic protein aggregation, ultimately resulting in cell death. Here, we describe a novel model system to investigate how UBB+1 impairs UPS function and whether it plays a causal role in protein aggregation. We expressed a protein analogous to UBB+1 in yeast (Ub(ext)) and demonstrated that it caused UPS impairment. Blocking ubiquitination of Ub(ext) or weakening its interactions with other ubiquitin-processing proteins reduced the UPS impairment. Expression of Ub(ext) altered the conjugation of wild-type ubiquitin to a UPS substrate. The expression of Ub(ext) markedly enhanced cellular susceptibility to toxic protein aggregates but, surprisingly, did not induce or alter nontoxic protein aggregates in yeast. Taken together, these results suggest that Ub(ext) interacts with more than one protein to elicit impairment of the UPS and affect protein aggregate toxicity. Furthermore, we suggest a model whereby chronic UPS impairment could inflict deleterious consequences on proper protein aggregate sequestration.
Collapse
Affiliation(s)
- Elizabeth M. H. Tank
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Heather L. True
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
| |
Collapse
|
47
|
Jariel-Encontre I, Bossis G, Piechaczyk M. Ubiquitin-independent degradation of proteins by the proteasome. Biochim Biophys Acta Rev Cancer 2008; 1786:153-77. [PMID: 18558098 DOI: 10.1016/j.bbcan.2008.05.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 05/15/2008] [Accepted: 05/15/2008] [Indexed: 02/08/2023]
Abstract
The proteasome is the main proteolytic machinery of the cell and constitutes a recognized drugable target, in particular for treating cancer. It is involved in the elimination of misfolded, altered or aged proteins as well as in the generation of antigenic peptides presented by MHC class I molecules. It is also responsible for the proteolytic maturation of diverse polypeptide precursors and for the spatial and temporal regulation of the degradation of many key cell regulators whose destruction is necessary for progression through essential processes, such as cell division, differentiation and, more generally, adaptation to environmental signals. It is generally believed that proteins must undergo prior modification by polyubiquitin chains to be addressed to, and recognized by, the proteasome. In reality, however, there is accumulating evidence that ubiquitin-independent proteasomal degradation may have been largely underestimated. In particular, a number of proto-oncoproteins and oncosuppressive proteins are privileged ubiquitin-independent proteasomal substrates, the altered degradation of which may have tumorigenic consequences. The identification of ubiquitin-independent mechanisms for proteasomal degradation also poses the paramount question of the multiplicity of catabolic pathways targeting each protein substrate. As this may help design novel therapeutic strategies, the underlying mechanisms are critically reviewed here.
Collapse
Affiliation(s)
- Isabelle Jariel-Encontre
- Institut de Génétique Moléculaire de Montpellier, CNRS, UMR5535, IFR122, 1919 Route de Mende, Montpellier, F-34293, France
| | | | | |
Collapse
|
48
|
ODCp, a brain- and testis-specific ornithine decarboxylase paralogue, functions as an antizyme inhibitor, although less efficiently than AzI1. Biochem J 2008; 410:613-9. [PMID: 18062773 DOI: 10.1042/bj20071423] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
ODC (ornithine decarboxylase), the first enzyme in the polyamine biosynthesis pathway in mammalian cells, is a labile protein. ODC degradation is stimulated by Az (antizyme), a polyamine-induced protein, which in turn is regulated by an ODC-related protein termed AzI (Az inhibitor). Recently, another ODCp (ODC paralogue) was suggested to function as AzI, on the basis of its ability to increase ODC activity and inhibit Az-stimulated ODC degradation in vitro. We show in the present study that ODCp is indeed capable of negating Az functions, as reflected by its ability to increase ODC activity and polyamine uptake and by its ability to provide growth advantage in stably transfected cells. However, ODCp is less potent than AzI1 in stimulating ODC activity, polyamine uptake and growth rate. The superiority of AzI1 to ODCp in inhibiting the Az-stimulated ODC degradation is also demonstrated using an in vitro degradation assay. We show that the basis for the inferiority of ODCp as an AzI is its lower affinity towards Az (Az1 and Az3). Further, we show here that ODCp, like AzI, is degraded in a ubiquitin-dependent manner, in a reaction that does not require either interaction with Az or the integrity of its C-terminus. Interaction with Az actually stabilizes ODCp by interfering with its ubiquitination. This results in sequestration of Az into a stable complex with ODCp, which is the central feature contributing to the ability of ODCp to function as AzI.
Collapse
|
49
|
Structural elements of the ubiquitin-independent proteasome degron of ornithine decarboxylase. Biochem J 2008; 410:401-7. [PMID: 17979831 DOI: 10.1042/bj20071239] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mouse ODC (ornithine decarboxylase) is quickly degraded by the 26S proteasome in mammalian and fungal cells. Its degradation is independent of ubiquitin but requires a degradation signal composed of residues 425-461 at the ODC C-terminus, cODC (the last 37 amino acids of the ODC C-terminus). Mutational analysis of cODC revealed the presence of two essential elements in the degradation signal. The first consists of cysteine and alanine at residues 441 and 442 respectively. The second element is the C-terminus distal to residue 442; it has little or no sequence specificity, but is intolerant of insertions or deletions that alter its span. Reducing conditions, which preclude all well-characterized chemical reactions of the Cys(441) thiol, are essential for in vitro degradation. These experiments imply that the degradative function of Cys(441) does not involve its participation in chemical reaction; it, instead, functions within a structural element for recognition by the 26S proteasome.
Collapse
|
50
|
Polyamines modulate the subcellular localization of RNA-binding protein HuR through AMP-activated protein kinase-regulated phosphorylation and acetylation of importin alpha1. Biochem J 2008; 409:389-98. [PMID: 17919121 DOI: 10.1042/bj20070860] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Polyamines are required for maintenance of intestinal epithelial integrity, and a decrease in cellular polyamines increases the cytoplasmic levels of RNA-binding protein HuR stabilizing p53 and nucleophosmin mRNAs, thus inhibiting IEC (intestinal epithelial cell) proliferation. The AMPK (AMP-activated protein kinase), an enzyme involved in responding to metabolic stress, was recently found to be implicated in regulating the nuclear import of HuR. Here, we provide evidence showing that polyamines modulate subcellular localization of HuR through AMPK-regulated phosphorylation and acetylation of Impalpha1 (importin alpha1) in IECs. Decreased levels of cellular polyamines as a result of inhibiting ODC (ornithine decarboxylase) with DFMO (D,L-alpha-difluoromethylornithine) repressed AMPK activity and reduced Impalpha1 levels, whereas increased levels of polyamines as a result of ODC overexpression induced both AMPK and Impalpha1 levels. AMPK activation by overexpression of the AMPK gene increased Impalpha1 but reduced the cytoplasmic levels of HuR in control and polyamine-deficient cells. IECs overexpressing wild-type Impalpha1 exhibited a decrease in cytoplasmic HuR abundance, while cells overexpressing Impalpha1 proteins bearing K22R (lacking acetylation site), S105A (lacking phosphorylation site) or K22R/S105A (lacking both sites) mutations displayed increased levels of cytoplasmic HuR. Ectopic expression of these Impalpha1 mutants also prevented the increased levels of cytoplasmic HuR following polyamine depletion. These results indicate that polyamine-mediated AMPK activation triggers HuR nuclear import through phosphorylation and acetylation of Impalpha1 in IECs and that polyamine depletion increases cytoplasmic levels of HuR as a result of inactivation of the AMPK-driven Impalpha1 pathway.
Collapse
|