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Abstract
Heterologous expression of recombinant ion channel subunits in mammalian cell lines allows for characterization of their functional properties and pharmacological regulation. In this chapter, we describe methods for thawing, refreezing, passaging, cell culture, and transfection of tsA201 cells suitable for electrophysiology and imaging experiments. Furthermore, we discuss the strengths and limitations of using these methods.
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Olamendi-Portugal T, Bartok A, Zamudio-Zuñiga F, Balajthy A, Becerril B, Panyi G, Possani LD. Isolation, chemical and functional characterization of several new K+-channel blocking peptides from the venom of the scorpion Centruroides tecomanus. Toxicon 2016; 115:1-12. [DOI: 10.1016/j.toxicon.2016.02.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 02/04/2016] [Accepted: 02/18/2016] [Indexed: 11/29/2022]
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Bartok A, Toth A, Somodi S, Szanto TG, Hajdu P, Panyi G, Varga Z. Margatoxin is a non-selective inhibitor of human Kv1.3 K+ channels. Toxicon 2014; 87:6-16. [PMID: 24878374 DOI: 10.1016/j.toxicon.2014.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/07/2014] [Accepted: 05/12/2014] [Indexed: 11/28/2022]
Abstract
Margatoxin (MgTx), an alpha-KTx scorpion toxin, is considered a selective inhibitor of the Kv1.3K + channel. This peptide is widely used in ion channel research; however, a comprehensive study of its selectivity with electrophysiological methods has not been published yet. The lack of selectivity might lead to undesired side effects upon therapeutic application or may lead to incorrect conclusion regarding the role of a particular ion channel in a physiological or pathophysiological response either in vitro or in vivo. Using the patch-clamp technique we characterized the selectivity profile of MgTx using L929 cells expressing mKv1.1 channels, human peripheral lymphocytes expressing Kv1.3 channels and transiently transfected tsA201 cells expressing hKv1.1, hKv1.2, hKv1.3, hKv1.4-IR, hKv1.5, hKv1.6, hKv1.7, rKv2.1, Shaker-IR, hERG, hKCa1.1, hKCa3.1 and hNav1.5 channels. MgTx is indeed a high affinity inhibitor of Kv1.3 (Kd = 11.7 pM) but is not selective, it inhibits the Kv1.2 channel with similar affinity (Kd = 6.4 pM) and Kv1.1 in the nanomolar range (Kd = 4.2 nM). Based on our comprehensive data MgTX has to be considered a non-selective Kv1.3 inhibitor, and thus, experiments aiming at elucidating the significance of Kv1.3 in in vitro or in vivo physiological responses have to be carefully evaluated.
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Affiliation(s)
- Adam Bartok
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Agnes Toth
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Sandor Somodi
- Division of Metabolic Diseases, Department of Internal Medicine, University of Debrecen, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Tibor G Szanto
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Peter Hajdu
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Dentistry, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary; MTA-DE Cell Biology and Signaling Research Group, 4032 Debrecen, Egyetem tér 1, Hungary. http://biophys.med.unideb.hu/en/node/311
| | - Zoltan Varga
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
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Schlaeger EJ, Christensen K. Transient gene expression in mammalian cells grown in serum-free suspension culture. Cytotechnology 2011; 30:71-83. [PMID: 19003357 DOI: 10.1023/a:1008000327766] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In order to establish a simple and scaleable transfection system we have used the cationic polymer polyethylenimine (PEI) to study transient transfection in HEK293 and 293(EBNA) cells grown in serum-free suspension culture. The transfection complexes were made directly within the cell culture by consecutively adding plasmid and PEI (direct method). Alternatively, the DNA-PEI transfection complexes were prepared in fresh medium (1/10 culture volume) and then added to the cells (indirect method). The results of this study clearly show that the ratio of PEI nitrogen to DNA phosphate is very important for high expression levels. The precise ratio is dependent on the DNA concentration. For example, using 1 mug/ml DNA by the indirect method, the ratio of optimal PEI:DNA was about 10-13:1. However, the ratio increases to 33:1 for 0.1-0.2 mug/ml DNA. By testing several different molecular weights of the polycationic polymer we could show that the highest transfection efficiency was obtained with the PEI 25 kDa. Using PEI 25 kDa the indirect method is superior to the direct addition because significantly lower DNA concentrations are needed. The expression levels of the soluble human TNF receptor p55 are even higher at low DNA compared to 1 mug/ml plasmid. The EBV-based pREP vectors gave better transient gene expression when used in 293(EBNA) cells compared to HEK293 cells in suspension culture. No differences in expression levels in the two cell lines were observed when the pC1 (CMV)-TNFR was used. In conclusion, PEI is a low-toxic transfection agent which provides high levels of transient gene expression in 293(EBNA) cells grown in serum-free suspension culture. This system allows highly reproducible, cost-effective production of milligram amounts of recombinant proteins in 2-5 l spinner culture scale within 3-5 days. Fermentor scale experiments, however, are less efficient because the PEI-mediated transient tranfection is inhibited by conditioned medium.
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Affiliation(s)
- E J Schlaeger
- Research Laboratories, F. Hoffmann La Roche Ltd., CH-4070, Basel, Switzerland
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Eberhardy SR, Radzniak L, Liu Z. Iron (III) citrate inhibits polyethylenimine-mediated transient transfection of Chinese hamster ovary cells in serum-free medium. Cytotechnology 2009; 60:1. [PMID: 19557539 DOI: 10.1007/s10616-009-9198-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 05/18/2009] [Indexed: 11/25/2022] Open
Abstract
Recent advances in transient transfection protocols using polyethylenimine (PEI) as a transfection reagent have led to the development of economical methods that provide yields sufficient for industrial production of proteins for many preclinical needs. There are many variables that can be optimized to improve protein expression in transient transfection, and one of the most critical is the medium in which the cells are grown. While transfection with PEI works well in media containing serum, the biopharmaceutical industry is moving away from animal-derived components in media. A number of serum-free media have been found to allow transient transfection, but many others do not for reasons that are not clear. Thus, knowledge of the components of serum-free media that can cause inhibition of PEI-mediated transient transfection would be useful for media development. In this study, an analysis was performed of various components of a serum-free medium used for Chinese hamster ovary cells in which PEI-mediated transient transfection was inhibited. We found that an iron supplement added to the medium was responsible for the inhibition. Further investigation showed that iron (III) citrate, a common iron chelator found in serum-free medium, was the specific component that caused the effect. Further, we showed that inhibition of transient transfection was caused by iron (III) citrate specifically, rather than citrate or iron alone. Finally, we showed that various iron chelators in serum-free media other than iron (III) citrate do not inhibit antibody expression.
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Affiliation(s)
- Scott R Eberhardy
- Biological and Sterile Product Development, Schering-Plough Research Institute, 1011 Morris Avenue, Union, NJ, 07083, USA.
| | - Laurie Radzniak
- Biological and Sterile Product Development, Schering-Plough Research Institute, 1011 Morris Avenue, Union, NJ, 07083, USA
| | - Zhong Liu
- Biological and Sterile Product Development, Schering-Plough Research Institute, 1011 Morris Avenue, Union, NJ, 07083, USA
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Pashine A, Göpfert U, Chen J, Hoffmann E, Dietrich PS, Peng SL. Failed efficacy of soluble human CD83-Ig in allogeneic mixed lymphocyte reactions and experimental autoimmune encephalomyelitis: implications for a lack of therapeutic potential. Immunol Lett 2008; 115:9-15. [PMID: 18079004 DOI: 10.1016/j.imlet.2007.10.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 10/24/2007] [Indexed: 01/09/2023]
Abstract
Soluble forms of CD83, a dendritic cell-specific surface glycoprotein, have been strongly proposed to be of therapeutic utility in inflammatory conditions such as multiple sclerosis and transplantation. We demonstrate here, however, that eukaryotically expressed, recombinant soluble human CD83-Ig molecules fail to achieve efficacy in model systems for those conditions: mouse experimental autoimmune encephalomyelitis models in vivo or in mixed lymphocyte reactions in vitro. These results raise concern as to the viability of a eukaryotically expressed soluble CD83 strategy for clinical therapeutic use.
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MESH Headings
- Animals
- Antigens, CD/blood
- Antigens, CD/immunology
- Antigens, CD/therapeutic use
- Dendritic Cells/immunology
- Encephalomyelitis, Autoimmune, Experimental/drug therapy
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/metabolism
- Humans
- Immunoglobulins/blood
- Immunoglobulins/immunology
- Immunoglobulins/therapeutic use
- Lymphocyte Culture Test, Mixed
- Membrane Glycoproteins/blood
- Membrane Glycoproteins/immunology
- Membrane Glycoproteins/therapeutic use
- Mice
- Mice, Inbred C57BL
- Recombinant Fusion Proteins/immunology
- Recombinant Fusion Proteins/therapeutic use
- CD83 Antigen
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Stavreva DA, Kawasaki M, Dundr M, Koberna K, Müller WG, Tsujimura-Takahashi T, Komatsu W, Hayano T, Isobe T, Raska I, Misteli T, Takahashi N, McNally JG. Potential roles for ubiquitin and the proteasome during ribosome biogenesis. Mol Cell Biol 2006; 26:5131-45. [PMID: 16782897 PMCID: PMC1489179 DOI: 10.1128/mcb.02227-05] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have investigated the possible involvement of the ubiquitin-proteasome system (UPS) in ribosome biogenesis. We find by immunofluorescence that ubiquitin is present within nucleoli and also demonstrate by immunoprecipitation that complexes associated with pre-rRNA processing factors are ubiquitinated. Using short proteasome inhibition treatments, we show by fluorescence microscopy that nucleolar morphology is disrupted for some but not all factors involved in ribosome biogenesis. Interference with proteasome degradation also induces the accumulation of 90S preribosomes, alters the dynamic properties of a number of processing factors, slows the release of mature rRNA from the nucleolus, and leads to the depletion of 18S and 28S rRNAs. Together, these results suggest that the UPS is probably involved at many steps during ribosome biogenesis, including the maturation of the 90S preribosome.
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Affiliation(s)
- Diana A Stavreva
- Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research [corrected] National Cancer Institute, Bethesda, MD 20892, USA
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Abstract
Recent work demonstrates that RNA interference (RNAi) can coordinate protein expression. Inhibitory RNAs are expressed naturally in cells as microRNAs (miRNAs) or introduced into cells as small interfering RNAs (siRNAs). Both types of small RNAs can be used at the bench to silence mRNA expression. For many researchers, transfection of siRNAs synthesized in vitro or purchased from commercial sources is impractical for the cellular system under study. As an alternative to transfection-based methods, we provide a practical approach to accomplish siRNA-mediated gene silencing through the generation and introduction of recombinant viral vectors expressing short hairpin RNAs (shRNAs). shRNAs are subsequently processed to siRNAs in vivo, leading to efficient, and, in some cases, long-term silencing.
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Affiliation(s)
- Beverly L Davidson
- Department of Internal Medicine, Neurology, Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, 52242, USA
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Stein CS, Davidson BL. Gene transfer to the brain using feline immunodeficiency virus-based lentivirus vectors. Methods Enzymol 2002; 346:433-54. [PMID: 11883084 DOI: 10.1016/s0076-6879(02)46070-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Colleen S Stein
- College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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Van Craenenbroeck K, Vanhoenacker P, Haegeman G. Episomal vectors for gene expression in mammalian cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:5665-78. [PMID: 10971576 DOI: 10.1046/j.1432-1327.2000.01645.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
An important reason for preferring mammalian cells for heterologous gene expression is their ability to make authentic proteins containing post-translational modifications similar to those of the native protein. The development of expression systems for mammalian cells has been ongoing for several years, resulting in a wide variety of effective expression vectors. The aim of this review is to highlight episomal expression vectors. Such episomal plasmids are usually based on sequences from DNA viruses, such as BK virus, bovine papilloma virus 1 and Epstein-Barr virus. In this review we will mainly focus on the improvements made towards the usefulness of these systems for gene expression studies and gene therapy.
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Affiliation(s)
- D Mackey
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706, USA
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Horlick RA, Sperle K, Breth LA, Reid CC, Shen ES, Robbins AK, Cooke GM, Largent BL. Rapid generation of stable cell lines expressing corticotropin-releasing hormone receptor for drug discovery. Protein Expr Purif 1997; 9:301-8. [PMID: 9126600 DOI: 10.1006/prep.1996.0701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Human HEK293 cells that stably express the Epstein Barr nuclear antigen 1 (EBNA1) support the episomal replication of plasmids containing the Epstein Barr virus origin of replication (EBV oriP). A 293EBNA (293E) cell line expressing the human corticotropin-releasing hormone receptor subtype I (CRHR1) from an episomal plasmid was generated (293CR1s), analyzed, adapted to spinner culture, and scaled-up for production in less than 6 weeks. Forty-seven stable CHO cell lines transfected with CRHR1 were also isolated. Expression of the receptor in the best of these lines (as judged by CRH-induced cAMP production), CHO-R22, was compared to that in 293CR1s cells. Results indicate that the CRHR1 episomal expression vector in 293E cells (1) rapidly generates stable cell lines suitable for scale-up; (2) is stably maintained during 3 months in culture; (3) expresses high levels of CRHR1 mRNA; and (4) expresses significantly more CRHR1 than the CHO-R22 line. Coexpression of additional G protein alpha subunit (G alpha s) with CRHR1 in 293E cells converts a higher percentage of receptor to the agonist high-affinity G-protein-coupled state. Our data support the idea that using the EBV oriP-driven episomal system for gene expression results in greater production of protein in a relatively short period of time.
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Affiliation(s)
- R A Horlick
- Applied Biotechnology Department, DuPont Merck Pharmaceutical Co., Wilmington, Delaware 19880-0400, USA
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Abstract
Recent years have seen a dramatic expansion in the range of applications of expression cloning techniques. New vectors and detection methods promise to further broaden the applicability of function-based screening approaches to problems in gene discovery. A major theme in the past year has been the introduction of engineered reporter cells that heighten the sensitivity with which clones expressing cDNAs can be identified.
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Affiliation(s)
- B Seed
- Department of Molecular Biology, Massachusetts General Hospital, Boston 02114, USA
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