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Schardt JS, Pornnoppadol G, Desai AA, Park KS, Zupancic JM, Makowski EK, Smith MD, Chen H, Garcia de Mattos Barbosa M, Cascalho M, Lanigan TM, Moon JJ, Tessier PM. Discovery and characterization of high-affinity, potent SARS-CoV-2 neutralizing antibodies via single B cell screening. Sci Rep 2021; 11:20738. [PMID: 34671080 PMCID: PMC8528929 DOI: 10.1038/s41598-021-99401-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 09/22/2021] [Indexed: 12/17/2022] Open
Abstract
Monoclonal antibodies that target SARS-CoV-2 with high affinity are valuable for a wide range of biomedical applications involving novel coronavirus disease (COVID-19) diagnosis, treatment, and prophylactic intervention. Strategies for the rapid and reliable isolation of these antibodies, especially potent neutralizing antibodies, are critical toward improved COVID-19 response and informed future response to emergent infectious diseases. In this study, single B cell screening was used to interrogate antibody repertoires of immunized mice and isolate antigen-specific IgG1+ memory B cells. Using these methods, high-affinity, potent neutralizing antibodies were identified that target the receptor-binding domain of SARS-CoV-2. Further engineering of the identified molecules to increase valency resulted in enhanced neutralizing activity. Mechanistic investigation revealed that these antibodies compete with ACE2 for binding to the receptor-binding domain of SARS-CoV-2. These antibodies may warrant further development for urgent COVID-19 applications. Overall, these results highlight the potential of single B cell screening for the rapid and reliable identification of high-affinity, potent neutralizing antibodies for infectious disease applications.
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Affiliation(s)
- John S. Schardt
- grid.214458.e0000000086837370Departments of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Ghasidit Pornnoppadol
- grid.214458.e0000000086837370Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Alec A. Desai
- grid.214458.e0000000086837370Departments of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Kyung Soo Park
- grid.214458.e0000000086837370Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Jennifer M. Zupancic
- grid.214458.e0000000086837370Departments of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Emily K. Makowski
- grid.214458.e0000000086837370Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Matthew D. Smith
- grid.214458.e0000000086837370Departments of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Hongwei Chen
- grid.214458.e0000000086837370Departments of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | | | - Marilia Cascalho
- grid.214458.e0000000086837370Department of Surgery, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Thomas M. Lanigan
- grid.214458.e0000000086837370Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI USA
| | - James J. Moon
- grid.214458.e0000000086837370Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA
| | - Peter M. Tessier
- grid.214458.e0000000086837370Departments of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109 USA ,grid.214458.e0000000086837370University of Michigan, North Campus Research Complex, B10-179, 2800 Plymouth Road, Ann Arbor, MI 48109 USA
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Zupancic JM, Schardt JS, Desai AA, Makowski EK, Smith MD, Pornnoppadol G, Garcia de Mattos Barbosa M, Cascalho M, Lanigan TM, Tessier PM. Engineered Multivalent Nanobodies Potently and Broadly Neutralize SARS-CoV-2 Variants. Adv Ther (Weinh) 2021; 4:2100099. [PMID: 34514086 PMCID: PMC8420545 DOI: 10.1002/adtp.202100099] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 07/04/2021] [Indexed: 01/17/2023]
Abstract
The COVID-19 pandemic continues to be a severe threat to human health, especially due to current and emerging SARS-CoV-2 variants with potential to escape humoral immunity developed after vaccination or infection. The development of broadly neutralizing antibodies that engage evolutionarily conserved epitopes on coronavirus spike proteins represents a promising strategy to improve therapy and prophylaxis against SARS-CoV-2 and variants thereof. Herein, a facile multivalent engineering approach is employed to achieve large synergistic improvements in the neutralizing activity of a SARS-CoV-2 cross-reactive nanobody (VHH-72) initially generated against SARS-CoV. This synergy is epitope specific and is not observed for a second high-affinity nanobody against a non-conserved epitope in the receptor-binding domain. Importantly, a hexavalent VHH-72 nanobody retains binding to spike proteins from multiple highly transmissible SARS-CoV-2 variants (B.1.1.7 and B.1.351) and potently neutralizes them. Multivalent VHH-72 nanobodies also display drug-like biophysical properties, including high stability, high solubility, and low levels of non-specific binding. The unique neutralizing and biophysical properties of VHH-72 multivalent nanobodies make them attractive as therapeutics against SARS-CoV-2 variants.
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Affiliation(s)
- Jennifer M. Zupancic
- Department of Chemical EngineeringUniversity of MichiganAnn ArborMI48109USA
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
| | - John S. Schardt
- Department of Chemical EngineeringUniversity of MichiganAnn ArborMI48109USA
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
- Department of Pharmaceutical SciencesUniversity of MichiganAnn ArborMI48109USA
| | - Alec A. Desai
- Department of Chemical EngineeringUniversity of MichiganAnn ArborMI48109USA
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
| | - Emily K. Makowski
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
- Department of Pharmaceutical SciencesUniversity of MichiganAnn ArborMI48109USA
| | - Matthew D. Smith
- Department of Chemical EngineeringUniversity of MichiganAnn ArborMI48109USA
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
| | - Ghasidit Pornnoppadol
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
- Department of Pharmaceutical SciencesUniversity of MichiganAnn ArborMI48109USA
| | | | - Marilia Cascalho
- Department of SurgeryUniversity of MichiganAnn ArborMI48109USA
- Department of Microbiology and ImmunologyUniversity of MichiganAnn ArborMI48109USA
| | - Thomas M. Lanigan
- Division of RheumatologyDepartment of Internal MedicineUniversity of Michigan Medical SchoolAnn ArborMI48109USA
| | - Peter M. Tessier
- Department of Chemical EngineeringUniversity of MichiganAnn ArborMI48109USA
- Biointerfaces InstituteUniversity of MichiganAnn ArborMI48109USA
- Department of Pharmaceutical SciencesUniversity of MichiganAnn ArborMI48109USA
- Department of Biomedical EngineeringUniversity of MichiganAnn ArborMI48109USA
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3
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Zupancic JM, Desai AA, Schardt JS, Pornnoppadol G, Makowski EK, Smith MD, Kennedy AA, Garcia de Mattos Barbosa M, Cascalho M, Lanigan TM, Tai AW, Tessier PM. Directed evolution of potent neutralizing nanobodies against SARS-CoV-2 using CDR-swapping mutagenesis. Cell Chem Biol 2021; 28:1379-1388.e7. [PMID: 34171229 PMCID: PMC8223476 DOI: 10.1016/j.chembiol.2021.05.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 04/06/2021] [Accepted: 05/27/2021] [Indexed: 02/01/2023]
Abstract
There is widespread interest in facile methods for generating potent neutralizing antibodies, nanobodies, and other affinity proteins against SARS-CoV-2 and related viruses to address current and future pandemics. While isolating antibodies from animals and humans are proven approaches, these methods are limited to the affinities, specificities, and functional activities of antibodies generated by the immune system. Here we report a surprisingly simple directed evolution method for generating nanobodies with high affinities and neutralization activities against SARS-CoV-2. We demonstrate that complementarity-determining region swapping between low-affinity lead nanobodies, which we discovered unintentionally but find is simple to implement systematically, results in matured nanobodies with unusually large increases in affinity. Importantly, the matured nanobodies potently neutralize both SARS-CoV-2 pseudovirus and live virus, and possess drug-like biophysical properties. We expect that our methods will improve in vitro nanobody discovery and accelerate the generation of potent neutralizing nanobodies against diverse coronaviruses.
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Affiliation(s)
- Jennifer M Zupancic
- Department of Chemical Engineering, University of Michigan, North Campus Research Complex, 2800 Plymouth Road, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alec A Desai
- Department of Chemical Engineering, University of Michigan, North Campus Research Complex, 2800 Plymouth Road, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - John S Schardt
- Department of Chemical Engineering, University of Michigan, North Campus Research Complex, 2800 Plymouth Road, Ann Arbor, MI 48109, USA; Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ghasidit Pornnoppadol
- Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Emily K Makowski
- Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Matthew D Smith
- Department of Chemical Engineering, University of Michigan, North Campus Research Complex, 2800 Plymouth Road, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Andrew A Kennedy
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | | | - Marilia Cascalho
- Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA; Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Thomas M Lanigan
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Andrew W Tai
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA; Medicine Service, Ann Arbor Veterans Administration Health System, Ann Arbor, MI, USA
| | - Peter M Tessier
- Department of Chemical Engineering, University of Michigan, North Campus Research Complex, 2800 Plymouth Road, Ann Arbor, MI 48109, USA; Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA.
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de Mattos Barbosa MG, Liu H, Huynh D, Shelley G, Keller ET, Emmer BT, Sherman E, Ginsburg D, Kennedy AA, Tai AW, Wobus C, Mirabeli C, Lanigan TM, Samaniego M, Meng W, Rosenfeld AM, Prak ETL, Platt JL, Cascalho M. IgV somatic mutation of human anti-SARS-CoV-2 monoclonal antibodies governs neutralization and breadth of reactivity. JCI Insight 2021; 6:147386. [PMID: 33769311 PMCID: PMC8262290 DOI: 10.1172/jci.insight.147386] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 03/24/2021] [Indexed: 12/24/2022] Open
Abstract
Abs that neutralize SARS-CoV-2 are thought to provide the most immediate and effective treatment for those severely afflicted by this virus. Because coronavirus potentially diversifies by mutation, broadly neutralizing Abs are especially sought. Here, we report a possibly novel approach to rapid generation of potent broadly neutralizing human anti-SARS-CoV-2 Abs. We isolated SARS-CoV-2 spike protein-specific memory B cells by panning from the blood of convalescent subjects after infection with SARS-CoV-2 and sequenced and expressed Ig genes from individual B cells as human mAbs. All of 43 human mAbs generated in this way neutralized SARS-CoV-2. Eighteen of the forty-three human mAbs exhibited half-maximal inhibitory concentrations (IC50) of 6.7 × 10-12 M to 6.7 × 10-15 M for spike-pseudotyped virus. Seven of the human mAbs also neutralized (with IC50 < 6.7 × 10-12 M) viruses pseudotyped with mutant spike proteins (including receptor-binding domain mutants and the S1 C-terminal D614G mutant). Neutralization of the Wuhan Hu-1 founder strain and of some variants decreased when coding sequences were reverted to germline, suggesting that potency of neutralization was acquired by somatic hypermutation and selection of B cells. These results indicate that infection with SARS-CoV-2 evokes high-affinity B cell responses, some products of which are broadly neutralizing and others highly strain specific. We also identify variants that would potentially resist immunity evoked by infection with the Wuhan Hu-1 founder strain or by vaccines developed with products of that strain, suggesting evolutionary courses that SARS-CoV-2 could take.
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Affiliation(s)
| | | | | | | | | | | | - Emily Sherman
- Department of Internal Medicine
- Life Sciences Institute
| | - David Ginsburg
- Department of Internal Medicine
- Life Sciences Institute
- Departments of Human Genetics and Pediatrics and Howard Hughes Medical Institute
| | | | | | | | | | - Thomas M. Lanigan
- Department of Internal Medicine
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, Michigan, USA
| | - Milagros Samaniego
- Department of Medicine, Henry Ford Health Systems, Detroit, Michigan, USA
| | - Wenzhao Meng
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Aaron M. Rosenfeld
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Eline T. Luning Prak
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jeffrey L. Platt
- Department of Surgery
- Department of Microbiology and Immunology, and
| | - Marilia Cascalho
- Department of Surgery
- Department of Microbiology and Immunology, and
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Ruth JH, Gurrea-Rubio M, Athukorala KS, Rasmussen SM, Weber DP, Randon PM, Gedert RJ, Lind ME, Amin MA, Campbell PL, Tsou PS, Mao-Draayer Y, Wu Q, Lanigan TM, Keshamouni VG, Singer NG, Lin F, Fox DA. CD6 is a target for cancer immunotherapy. JCI Insight 2021; 6:145662. [PMID: 33497367 PMCID: PMC8021120 DOI: 10.1172/jci.insight.145662] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 01/20/2021] [Indexed: 12/12/2022] Open
Abstract
Limitations of checkpoint inhibitor cancer immunotherapy include induction of autoimmune syndromes and resistance of many cancers. Since CD318, a novel CD6 ligand, is associated with the aggressiveness and metastatic potential of human cancers, we tested the effect of an anti-CD6 monoclonal antibody, UMCD6, on killing of cancer cells by human lymphocytes. UMCD6 augmented killing of breast, lung, and prostate cancer cells through direct effects on both CD8+ T cells and NK cells, increasing cancer cell death and lowering cancer cell survival in vitro more robustly than monoclonal antibody checkpoint inhibitors that interrupt the programmed cell death 1 (PD-1)/PD-1 ligand 1 (PD-L1) axis. UMCD6 also augmented in vivo killing by human peripheral blood lymphocytes of a human breast cancer line xenotransplanted into immunodeficient mice. Mechanistically, UMCD6 upregulated the expression of the activating receptor NKG2D and downregulated expression of the inhibitory receptor NKG2A on both NK cells and CD8+ T cells, with concurrent increases in perforin and granzyme B production. The combined capability of an anti-CD6 monoclonal antibody to control autoimmunity through effects on CD4+ lymphocyte differentiation while enhancing killing of cancer cells through distinct effects on CD8+ and NK cells opens a potential new approach to cancer immunotherapy that would suppress rather than instigate autoimmunity.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | - Qi Wu
- Department of Neurology, and
| | | | | | - Nora G Singer
- Case Western Reserve University.,Division of Rheumatology, MetroHealth Medical Center, Cleveland, Ohio, USA
| | - Feng Lin
- Department of Immunity and Inflammation, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
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Lanigan TM, Rasmussen SM, Weber DP, Athukorala KS, Campbell PL, Fox DA, Ruth JH. Real time visualization of cancer cell death, survival and proliferation using fluorochrome-transfected cells in an IncuCyte ® imaging system. J Biol Methods 2020; 7:e133. [PMID: 32577423 PMCID: PMC7300428 DOI: 10.14440/jbm.2020.323] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 04/07/2020] [Accepted: 04/24/2020] [Indexed: 12/19/2022] Open
Abstract
Cancer immunotherapy is a rapidly advancing and viable approach to treating cancer along with more traditional forms of therapy. Real-time cell analysis technologies that examine the dynamic interactions between cancer cells and the cells of the immune system are becoming more important for assessment of novel therapeutics. In this report, we use the IncuCyte® imaging system to study the killing potential of various immune cells on cancer cell lines. The IncuCyte® system tracks living cells, labeled by a red fluorescent protein, and cell death, as indicated by the caspase-3/7 reagent, which generates a green fluorescent signal upon activation of apoptotic pathways. Despite the power of this approach, obtaining commercially fluorescent cancer cell lines is expensive and limited in the range of cell lines that are available. To overcome this barrier, we developed an inexpensive method using a lentiviral construct expressing nuclear localized mKate2 red fluorescent protein to stably label cancer cells. We demonstrate that this method is effective in labeling a wide variety of cell lines, allowing for analyses of different cancers as well as different cell lines of the same type of cancer.
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Affiliation(s)
- Thomas M Lanigan
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Stephanie M Rasmussen
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Daniel P Weber
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Kalana S Athukorala
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Phillip L Campbell
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - David A Fox
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Jeffrey H Ruth
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
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Abstract
Genetic engineering is the use of molecular biology technology to modify DNA sequence(s) in genomes, using a variety of approaches. For example, homologous recombination can be used to target specific sequences in mouse embryonic stem (ES) cell genomes or other cultured cells, but it is cumbersome, poorly efficient, and relies on drug positive/negative selection in cell culture for success. Other routinely applied methods include random integration of DNA after direct transfection (microinjection), transposon-mediated DNA insertion, or DNA insertion mediated by viral vectors for the production of transgenic mice and rats. Random integration of DNA occurs more frequently than homologous recombination, but has numerous drawbacks, despite its efficiency. The most elegant and effective method is technology based on guided endonucleases, because these can target specific DNA sequences. Since the advent of clustered regularly interspaced short palindromic repeats or CRISPR/Cas9 technology, endonuclease-mediated gene targeting has become the most widely applied method to engineer genomes, supplanting the use of zinc finger nucleases, transcription activator-like effector nucleases, and meganucleases. Future improvements in CRISPR/Cas9 gene editing may be achieved by increasing the efficiency of homology-directed repair. Here, we describe principles of genetic engineering and detail: (1) how common elements of current technologies include the need for a chromosome break to occur, (2) the use of specific and sensitive genotyping assays to detect altered genomes, and (3) delivery modalities that impact characterization of gene modifications. In summary, while some principles of genetic engineering remain steadfast, others change as technologies are ever-evolving and continue to revolutionize research in many fields.
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Affiliation(s)
- Thomas M. Lanigan
- Biomedical Research Core Facilities, Vector Core, University of Michigan, Ann Arbor, MI 48109, USA; (T.M.L.); (H.C.K.)
- Department of Internal Medicine, Division of Rheumatology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Huira C. Kopera
- Biomedical Research Core Facilities, Vector Core, University of Michigan, Ann Arbor, MI 48109, USA; (T.M.L.); (H.C.K.)
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Thomas L. Saunders
- Biomedical Research Core Facilities, Transgenic Animal Model Core, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Internal Medicine, Division of Genetic Medicine, University of Michigan, Ann Arbor, MI 48109, USA
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Kopera HC, Hilgarth RS, Kopas TL, Lanigan TM. Development and validation of a reporter cell line for rapid AAV quality control assessment. MethodsX 2020; 7:100800. [PMID: 32021830 PMCID: PMC6995252 DOI: 10.1016/j.mex.2020.100800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 01/15/2020] [Indexed: 11/06/2022] Open
Abstract
Adenovirus-associated virus is a powerful vector system for transducing cells in vivo. It is widely used in animal systems due to high transduction efficiency of non-dividing cells with more than a dozen serotypes that have preferential tissue tropism. The viral genome remains episomal in the nucleus but maintains sustained expression in terminally differentiated cells for several weeks to months. Despite the popularity of recombinant AAV (rAAV) vectors, quality control testing of the virus after production is largely limited to physical characteristics such as viral genomes/ml determinations and silver staining acrylamide gels to determine purity. Functional testing, in vivo, is not practical due to high cost and restricted access of animal care and long duration of the assay (2-3 weeks). Some functional testing can be accomplished in cultured cells such as HEK293 cells, but HEK293 cells limit the types of rAAV constructs that can be tested. Many rAAV constructs are designed to study neurons in the brain with neural-specific promoters and many are floxed with loxp sites to be "activated" only in Cre-expressing neurons in transgenic animals. To develop a reporter cell line for rapid rAAV quality control assessment of these neural-specific, floxed rAAV constructs, we used the lentiviral system to stably express Cre recombinase in the SH-SY5Y neuroblastoma cell line. •A simple and economic method to evaluate recombinant AAV in vitro.•Allows functional validation of rAAV across a wide range of serotypes and promoters.•Allows functional validation of Cre-dependent rAAV constructs.
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Affiliation(s)
- Huira C. Kopera
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, United States
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI 48109, United States
| | - Roland S. Hilgarth
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI 48109, United States
| | - Tonya L. Kopas
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI 48109, United States
| | - Thomas M. Lanigan
- Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, United States
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI 48109, United States
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Abstract
PCR is a powerful tool for generating specific fragments of DNA that can be used to create gene variations or tagged expression constructs. Overlap extension PCR is a valuable technique that is commonly used for cloning large complex fragments, making edits to cloned genes or fusing two gene elements together. After difficulties in utilizing this technique following existing methods, we developed an optimized protocol. To accomplish this, three significant changes were made; 1) touchdown PCR cycling parameters were used to eliminate the need for optimizing PCR cycling conditions, 2) the high-fidelity, high-processivity Q5 DNA polymerase was used to improve full-length amplification quality, and 3) a reduced amount of primer in the final PCR amplification step decreased non-specific amplimers. This modified protocol results in consistent generation of gene fusion products, with little to no background and enhanced efficiency of the transgene construction process.
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Affiliation(s)
- Roland S. Hilgarth
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI, 48109, United States
| | - Thomas M. Lanigan
- Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48109, United States
- Vector Core, Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI, 48109, United States
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10
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Ohara RA, Edhayan G, Rasmussen SM, Isozaki T, Remmer HA, Lanigan TM, Campbell PL, Urquhart AG, Lawton JN, Chung KC, Fox DA, Ruth JH. Citrullinated Inhibitor of DNA Binding 1 Is a Novel Autoantigen in Rheumatoid Arthritis. Arthritis Rheumatol 2019; 71:1241-1251. [PMID: 30861322 PMCID: PMC6663620 DOI: 10.1002/art.40886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 03/07/2019] [Indexed: 02/02/2023]
Abstract
Objective To explore the intrinsic role of inhibitor of DNA binding 1 (ID‐1) in rheumatoid arthritis (RA) fibroblast‐like synoviocytes (FLS) and to investigate whether ID‐1 is citrullinated and autoantigenic in RA. Methods RA patient serum ID‐1 levels were measured before and after infliximab treatment. RA FLS were transfected with a clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR‐associated protein 9 construct targeting ID‐1 to examine the effects of ID‐1 deletion. RA synovial fluid (SF) and homogenized synovial tissue (ST) were immunoprecipitated for ID‐1 and measured for citrullinated residues using an enzyme‐linked immunosorbent assay and Western blotting. Liquid chromatography tandem mass spectrometry (LC‐MS/MS) was performed on in vitro–citrullinated recombinant human ID‐1 (cit–ID‐1) to localize the sites of citrullination. Normal and RA sera and SF were analyzed by immunodot blotting for anti–citrullinated protein antibodies (ACPAs) to cit–ID‐1. Results RA patient serum ID‐1 levels positively correlated with several disease parameters and were reduced after infliximab treatment. RA FLS displayed reduced growth and a robust increase in interleukin‐6 (IL‐6) and IL‐8 production upon deletion of ID‐1. ID‐1 immunodepletion significantly reduced the levels of citrullinated residues in RA SF, and citrullinated ID‐1 was detected in homogenized RA ST (n = 5 samples; P < 0.05). Immunodot blot analyses revealed ACPAs to cit–ID‐1 but not to native ID‐1, in RA peripheral blood (PB) sera (n = 30 samples; P < 0.001) and SF (n = 18 samples; P < 0.05) but not in normal PB sera. Following analyses of LC‐MS/MS results for citrullination sites and corresponding reactivity in immunodot assays, we determined the critical arginines in ID‐1 for autoantigenicity: R33, R52, and R121. Conclusion Novel roles of ID‐1 in RA include regulation of FLS proliferation and cytokine secretion as well as autoantigenicity following citrullination.
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Affiliation(s)
- Ray A Ohara
- University of Michigan Medical School, Ann Arbor
| | | | | | | | | | | | | | - Andrew G Urquhart
- University of Michigan Health System and A. Alfred Taubman Health Care Center, Ann Arbor, Michigan
| | - Jeffrey N Lawton
- University of Michigan Health System and A. Alfred Taubman Health Care Center, Ann Arbor, Michigan
| | - Kevin C Chung
- University of Michigan Health System and A. Alfred Taubman Health Care Center, Ann Arbor, Michigan
| | - David A Fox
- University of Michigan Medical School, Ann Arbor
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Ohba S, Lanigan TM, Roessler BJ. Leptin receptor JAK2/STAT3 signaling modulates expression of Frizzled receptors in articular chondrocytes. Osteoarthritis Cartilage 2010; 18:1620-9. [PMID: 20868760 PMCID: PMC2997121 DOI: 10.1016/j.joca.2010.09.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 09/13/2010] [Accepted: 09/14/2010] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Differentiated articular chondrocytes express a functional bisoform of the leptin receptor (LRb); however, leptin-LRb signaling in these cells is poorly understood. We hypothesized that leptin-LRb signaling in articular chondrocytes functions to modulate canonical Wnt signaling events by altering the expression of Frizzled (FZD) receptors. METHODS Human chondrocyte cell lines and primary articular chondrocytes were grown in serum containing growth media for 24h, followed by a media change to Dulbecco's modified Eagle's medium (DMEM) containing 1% Nutridoma-SP to obtain a serum-deficient environment for 24h before treatment. Treatments included recombinant human leptin (10-100nM), recombinant human IL-6 (0.3-3nM), or recombinant human erythropoietin (Epo) (10mU/ml). Cells were harvested 30min-48h after treatment and whole cell lysates were analyzed using immunoblots or luciferase assays. RESULTS Treatment of cells with leptin resulted in activation of Janus kinase 2 (JAK2) and subsequent phosphorylation of specific tyrosine residues on LRb, followed by dose- and time-dependent increases in the expression of Frizzled-1 (FZD1) and Frizzled-7 (FZD7). Leptin-mediated increases in the expression of FZD1 were blocked by pre-treatment with the protein synthesis inhibitor cycloheximide or the JAK2 inhibitor AG490. Experiments using a series of hybrid Epo extracellular domain-leptin intracellular domain receptors (ELR) harboring mutations of specific tyrosine residues in the cytoplasmic tail showed that increases in the expression of FZD1 were dependent on LRb-mediated phosphorylation of STAT3, but not ERK1/2 or STAT5. Leptin pre-treatment of chondrocytes prior to Wnt3a stimulation resulted in an increased magnitude of canonical Wnt signaling. CONCLUSION These experiments show that leptin-LRb signaling in articular chondrocytes modulates expression of canonical Wnt signaling receptors and suggests that direct cross-talk between these pathways is important in determining chondrocyte homeostasis.
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Affiliation(s)
- Seigo Ohba
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-5688
| | - Thomas M. Lanigan
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-5688
| | - Blake J. Roessler
- Division of Rheumatology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-5688
- To whom correspondence should be addressed: 3560 MSRB2, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-5688, Tel.: 734-763-7949, Fax: 734-764-3596,
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Abstract
Bile acids conjugated to oligoarginine-containing peptides (BACs) form complexes with DNA based on the electrostatic interactions between negatively charged phosphate groups of the nucleic acid and the positively charged side chain guanidinium groups of the oligoarginine in the BACs. Charge neutralization of both components and subsequent increases of the net positive charge of the complex combined with the water-soluble lipophilic nature of the bile acid results in changes in the physicochemistry and biological properties of the complexes. We have examined the relationship of a series of 13 BACs on their interaction with circular plasmid DNA (pDNA). The formation of soluble, low-density and insoluble, high-density complexes was analyzed using several methods. The formation of high-density complexes was dependent on the DNA concentration, and was enhanced by increasing the BAC to pDNA charge ratio. Several of the BAC:pDNA complexes demonstrated exclusion of the DNA-intercalator Hoechst 33258 from pDNA, and were also protected from DNase activity. Several BAC conjugates interacted with pDNA to form nanometer-sized particles suitable for cell transfection in vitro. Five of the 13 BACs were transfection competent as single agents, and 11 of the 13 BACs showed enhancement of transfection in combination with DOPE containing liposomes or silica nanoparticles.
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Affiliation(s)
- Phillip E Kish
- TSRL, Inc., 540 Avis Drive, Suite A, Ann Arbor, Michigan 48108, USA.
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13
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Abstract
Connector enhancer of KSR (CNK) is a multidomain protein that participates in Ras signaling in Drosophila eye development. In this report we identify the human homologue of CNK, termed CNK2A, and a truncated alternatively spliced variant, CNK2B. We characterize CNK2 phosphorylation, membrane localization, and interaction with Ras effector molecules. Our results show that MAPK signaling appears to play a role in the phosphorylation of CNK2 in vivo. CNK2 is found in both membrane and cytoplasmic fractions of the cell. In MDCK cells, full-length CNK2 is localized to the lateral plasma membrane. Consistent with previous reports, we show CNK2 interacts with Raf. CNK2 interaction was mapped to the regulatory and kinase domains of Raf, as well as to the carboxyl-terminal half of CNK2. CNK2 also interacts with the Ral signaling components, Ral GTPase, and the RalGDS family member Rlf. CNK2 interaction was mapped to the GEF domain of Rlf. The ability of CNK2 to interact with both Ras effector proteins Raf and Rlf suggests that CNK2 may integrate signals between MAPK and Ral pathways through a complex interplay of components.
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Affiliation(s)
- Thomas M Lanigan
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA
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Lanigan TM, DeRaad SK, Russo AF. Requirement of the MASH-1 transcription factor for neuroendocrine differentiation of thyroid C cells. J Neurobiol 1998; 34:126-34. [PMID: 9468384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Thyroid C cells are neural crest-derived neuroendocrine cells that can acquire features similar to serotonergic neurons. Based on developmental and phenotypic markers, we have previously proposed that C cells and serotonergic enteric neurons arise from a common sympathoadrenal progenitor. In this report, we genetically examined this relationship using mice lacking the mammalian achaete-scute homologue 1 (MASH-1) transcription factor, since MASH-1 has recently been shown to be required for differentiation of serotonergic enteric neurons. We found that MASH-1 knockout mice have a greatly reduced number of C cells based on the lack of calcitonin and serotonin immunoreactivity. In contrast, calcitonin and serotonin were still expressed in cultured mature C cells that no longer express MASH-1, demonstrating that MASH-1 is not directly required for the expression of these two markers. Hence, MASH-1 is required to establish the C-cell phenotype and supports the model that C cells lie in the neuronal differentiation pathway of the sympathoadrenal neural crest.
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Affiliation(s)
- T M Lanigan
- Molecular Biology Program, University of Iowa, Iowa City 52242, USA
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Lanigan TM, Russo AF. Binding of upstream stimulatory factor and a cell-specific activator to the calcitonin/calcitonin gene-related peptide enhancer. J Biol Chem 1997; 272:18316-24. [PMID: 9218472 DOI: 10.1074/jbc.272.29.18316] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The calcitonin/calcitonin gene-related peptide (CT/CGRP) gene is selectively transcribed in thyroid C cells and neurons. We have previously shown that the rat CT/CGRP cell-specific enhancer is synergistically regulated by a helix-loop-helix (HLH) protein and the OB2 octamer-binding protein. In this report, we show that the HLH-OB2 enhancer is required for full promoter activity, even in the context of other HLH elements. Since this enhancer appears to be a major controlling element, we have characterized the HLH and OB2 DNA binding proteins. We have identified the major HLH complex as a heterodimer of the ubiquitous upstream stimulatory factor (USF)-1 and USF-2 proteins. USF bound the enhancer with a reasonably high affinity (KD 1.6 nM), comparable to other genes. Characterization of a series of mutations revealed that a portion of the HLH motif is also recognized by OB2 and confirmed that HLH activity requires OB2. We have shown that OB2 is a single DNA binding protein based on UV cross-linking studies. The 68-kDa protein-DNA complex was detected only in C cell lines, including a human C cell line that has robust HLH-OB2 enhancer activity. These results suggest that the calcitonin/CGRP gene is controlled by the combinatorial activity of a ubiquitous USF HLH heterodimer and an associated cell-specific activator.
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Affiliation(s)
- T M Lanigan
- Molecular Biology Program, University of Iowa, Iowa City, Iowa 52242, USA
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Clark MS, Lanigan TM, Page NM, Russo AF. Induction of a serotonergic and neuronal phenotype in thyroid C-cells. J Neurosci 1995; 15:6167-78. [PMID: 7666199 PMCID: PMC6577694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have investigated whether rat thyroid C-cells can acquire a phenotype similar to serotonergic neurons. C-cells are neural crest derived endocrine cells with some intrinsic neuronal and serotonergic properties. A relatively simple isolation scheme yielded cultures of about 50% initial purity, as measured by fluorescence activated cell sorting. These enriched C-cells could extend neurites up to 550 microns on a laminin-containing substratum in the presence of NGF. The cultured C-cells expressed neurofilaments and this expression was enhanced by NGF treatment. The C-cells also expressed two markers of the sympathoadrenal neural crest lineage, the mammalian achaete scute homolog-1 (MASH-1) transcription factor, and the B2 cell surface antigen. Interestingly, MASH-1 was not detectable after the C-cells were placed in culture, which is consistent with neuronal differentiation, since MASH-1 is only expressed in neuronal progenitors prior to differentiation. We then demonstrated that C-cells possess the fundamental features of serotonergic neurons: synthesis and secretion, uptake, and feedback control. The enriched C-cells, as well as the CA77 C-cell line, showed 5-HT immunostaining, expression of tryptophan hydroxylase mRNA, 5-HT1B autoreceptor mRNA, and 5-HT transporter mRNA and activity. NGF greatly induced 5-HT transporter activity as determined by sensitivity to sertraline, a selective 5-HT reuptake inhibitor. Based on these results, we propose that thyroid C-cells are derived from a vagal sympathoadrenal progenitor, similar to serotonergic enteric neurons, and can undergo neuronal transdifferentiation. Hence, these cells should provide suitable and convenient models for molecular and cellular studies on serotonergic neurons.
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Affiliation(s)
- M S Clark
- Molecular Biology Program, University of Iowa, Iowa City 52242, USA
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Lanigan TM, Tverberg LA, Russo AF. Retinoic acid repression of cell-specific helix-loop-helix-octamer activation of the calcitonin/calcitonin gene-related peptide enhancer. Mol Cell Biol 1993; 13:6079-88. [PMID: 8413210 PMCID: PMC364668 DOI: 10.1128/mcb.13.10.6079-6088.1993] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We have investigated the mechanism underlying repression of calcitonin/calcitonin gene-related peptide (CT/CGRP) gene expression by retinoic acid. Retinoic acid treatment of the CA77 thyroid C-cell line decreased CT/CGRP promoter activity two- to threefold, which correlates well with the decrease in calcitonin and CGRP mRNA levels. Repression is mediated through the nuclear retinoic acid receptors (RAR) on the basis of the retinoid specificity, the sensitivity of repression (half-maximal repression at 0.2 nM), and the additional repression caused by cotransfection of an alpha-RAR expression vector. The sequences required for retinoic acid repression were localized to an 18-bp element containing cell-specific enhancer activity. The enhancer binds helix-loop-helix (HLH) and octamer transcription factors that act synergistically to activate transcription. Retinoic acid repression requires both these factors since mutations in either motif resulted in the loss of repression. Furthermore, repression was observed only in cell lines containing enhancer activity. We have used electrophoretic mobility shift assays to show that repression does not involve direct DNA binding of RAR or RAR-retinoid X receptor heterodimers. Instead, repression appears to involve interactions with the stimulatory enhancer factors. Following retinoic acid treatment, there was a specific decrease in an enhancer complex containing both HLH and octamer proteins. Formation of the HLH-octamer complex was also specifically blocked by the addition of exogenous RAR-retinoid X receptor protein. These results demonstrate that RAR can repress CT/CGRP gene transcription by interfering with combinatorial activation by cell-specific HLH and octamer proteins.
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Affiliation(s)
- T M Lanigan
- Department of Physiology and Biophysics, University of Iowa, Iowa City 52242
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Crawford JA, Mutchler KJ, Sullivan BE, Lanigan TM, Clark MS, Russo AF. Neural expression of a novel alternatively spliced and polyadenylated Gs alpha transcript. J Biol Chem 1993; 268:9879-85. [PMID: 8486667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We have isolated an alternative transcript of the rat Gs alpha signal transduction protein gene, referred to as Gs alpha N1. Gs alpha N1 was isolated by differential hybridization screening of genes induced upon dexamethasone treatment of the neuronal-like CA77 rat thyroid C-cell line. The 1-kilobase Gs alpha N1 transcript is generated by alternative splicing and polyadenylation of a novel terminal exon. This exon lies 800 base pairs downstream of exon 3 in the Gs alpha gene. Dexamethasone differentially induced Gs alpha N1 severalfold relative to Gs alpha mRNA in the CA77 cells, similar to the bias seen with alternative processing of the calcitonin/calcitonin gene-related peptide transcript. In addition to the differential regulation by dexamethasone, the expression pattern of Gs alpha N1 in rat tissues differed markedly from Gs alpha. Gs alpha N1 mRNA was much more abundant in the brain, with intermediate levels in skeletal muscle and very low levels in other tissues. This was in contrast to the more ubiquitously expressed Gs alpha mRNA. Within the brain, Gs alpha N1 was particularly abundant in discrete regions of the brainstem and hypothalamus that modulate autonomic functions. Examination of rat embryos demonstrated that Gs alpha is expressed in both brain and nonneural tissue at least 1 day before Gs alpha N1 mRNA could be detected in the embryonic brain. Based on the regulated expression of the Gs alpha N1 transcript and previous studies on G alpha proteins, the predicted Gs alpha N1 protein may potentially modulate several heterotrimeric G protein functions in the nervous system.
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Affiliation(s)
- J A Crawford
- Department of Physiology and Biophysics, University of Iowa, Iowa City 52242
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Abstract
We have analyzed the effect of extracellular stimuli on the differentiation state of the CA77 thyroid C-cell line as a model to understand the control of neural crest cell differentiation. In contrast to the endocrine C-cell phenotype, we found that CA77 cells have a neuronal phenotype characterized by laminin-induced neurites, neuronal antigens, and calcitonin gene-related peptide (CGRP) mRNA expression. Treatment with dexamethasone and retinoic acid reversibly repressed some of these neuronal characteristics to induce features more characteristic of the parental C-cells. In the case of dexamethasone treatment, there was a partial retraction and thinning of neurites, an increased number of secretory vesicles in the cell bodies, and about a 10-fold decrease in DNA synthesis. Treatment with retinoic acid alone or in combination with dexamethasone caused decreased cell adhesion and an even more extensive retraction of the neurites. Dexamethasone also biased the steady state levels of the alternatively spliced transcripts from the calcitonin/CGRP gene to favor calcitonin relative to CGRP mRNA. While retinoic acid treatment decreased both calcitonin and CGRP mRNA levels, the combination of dexamethasone and retinoic acid still yielded the increase in calcitonin relative to CGRP mRNA. These results suggest that glucocorticoids and retinoic acid may contribute to a late and reversible differentiation of thyroid C-cells by partly repressing neuronal properties.
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Affiliation(s)
- A F Russo
- Department of Physiology and Biophysics, University of Iowa, Iowa City 52242
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Dunn SM, Lanigan TM, Howell EE. Dihydrofolate reductase from Escherichia coli: probing the role of aspartate-27 and phenylalanine-137 in enzyme conformation and the binding of NADPH. Biochemistry 1990; 29:8569-76. [PMID: 2271540 DOI: 10.1021/bi00489a010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In the absence of ligands, dihydrofolate reductase from Escherichia coli exists in at least two interconvertible conformations, only one of which binds NADPH with high affinity. This equilibrium is pH dependent, involving an ionizable group of the enzyme (pK approximately 5.5), and the proportion of the NADPH-binding conformer increases from 42% at pH 5 to 65% at pH 8. The role of specific amino acids in enzyme conformation has been investigated by studying the kinetics of NADPH binding to three dihydrofolate reductase mutants: (i) a mutant in which Asp-27, a residue that is directly involved in the binding of folates and antifolates but not NADPH, has been replaced by a serine, (ii) a mutant in which Phe-137 on the exterior of the molecule and distant from the binding sites has been replaced by a serine, and (iii) a mutant in which both Asp-27 and Phe-137 have been replaced by serines. Mutation of the Asp-27 residue reduces the affinity for NADPH by approximately 7-fold. Kinetic measurements have suggested that this is due mainly to an increase in the rate of dissociation of the initial complex and a slight shift in the enzyme equilibrium to favor the nonbinding conformation. The pH dependence of the conformer equilibrium is also shifted by approximately one pH unit to higher pH (pK approximately 6.5). In addition, the pH profile suggests the involvement of a second ionizable group having a pK of about 8 since, above pH 7, the proportion of the NADPH-binding form decreases.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S M Dunn
- Department of Pharmacology, University of Alberta, Edmonton, Canada
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