51
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Subedi GP, Falconer DJ, Barb AW. Carbohydrate-Polypeptide Contacts in the Antibody Receptor CD16A Identified through Solution NMR Spectroscopy. Biochemistry 2017; 56:3174-3177. [PMID: 28613884 DOI: 10.1021/acs.biochem.7b00392] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Asparagine-linked carbohydrates (N-glycans) are common modifications of eukaryotic proteins that confer multiple properties, including the essential stabilization of therapeutic monoclonal antibodies. Here we present a rapid and efficient strategy for identifying N-glycans that contact polypeptide residues and apply the method to profile the five N-glycans attached to the human antibody receptor CD16A (Fc γ receptor IIIA). Human embryonic kidney 293S cells expressed CD16A with 13CU-labeled N-glycans using standard protein expression techniques and medium supplemented with 3 g/L [13CU]glucose. Anomeric resonances on the protein-linked N-acetylglucosamine residue at the reducing end of the glycan are particularly well suited to studies of multiply glycosylated N-glycoproteins because only one reducing end and nitrogen-linked residue is present in each N-glycan. Correlations between anomeric 1H1 and 13C1 nuclei on the reducing end residue generate crosspeaks in a conventional two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance (NMR) experiment that appear in a region of the spectrum devoid of other carbohydrate peaks or background protein signals. Two N-glycan peaks corresponding to the N45 and N162 N-glycans were dispersed from the rapidly averaged peaks corresponding to the N38, N74, and N169 N-glycans. We used a combination of NMR and 1 μs all-atom computational simulations to identify unexpected contacts between the N45 N-glycan and CD16A polypeptide residues.
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Affiliation(s)
- Ganesh P Subedi
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University , 2437 Pammel Drive, Molecular Biology Building, Room 4210, Ames, Iowa 50011, United States
| | - Daniel J Falconer
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University , 2437 Pammel Drive, Molecular Biology Building, Room 4210, Ames, Iowa 50011, United States
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University , 2437 Pammel Drive, Molecular Biology Building, Room 4210, Ames, Iowa 50011, United States
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52
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Bruggeman CW, Dekkers G, Bentlage AEH, Treffers LW, Nagelkerke SQ, Lissenberg-Thunnissen S, Koeleman CAM, Wuhrer M, van den Berg TK, Rispens T, Vidarsson G, Kuijpers TW. Enhanced Effector Functions Due to Antibody Defucosylation Depend on the Effector Cell Fcγ Receptor Profile. THE JOURNAL OF IMMUNOLOGY 2017; 199:204-211. [PMID: 28566370 DOI: 10.4049/jimmunol.1700116] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 05/04/2017] [Indexed: 01/12/2023]
Abstract
Abs of the IgG isotype are glycosylated in their Fc domain at a conserved asparagine at position 297. Removal of the core fucose of this glycan greatly increases the affinity for FcγRIII, resulting in enhanced FcγRIII-mediated effector functions. Normal plasma IgG contains ∼94% fucosylated Abs, but alloantibodies against, for example, Rhesus D (RhD) and platelet Ags frequently have reduced fucosylation that enhances their pathogenicity. The increased FcγRIII-mediated effector functions have been put to use in various afucosylated therapeutic Abs in anticancer treatment. To test the functional consequences of Ab fucosylation, we produced V-gene-matched recombinant anti-RhD IgG Abs of the four different subclasses (IgG1-4) with and without core fucose (i.e., 20% fucose remaining). Binding to all human FcγR types and their functional isoforms was assessed with surface plasmon resonance. All hypofucosylated anti-RhD IgGs of all IgG subclasses indeed showed enhanced binding affinity for isolated FcγRIII isoforms, without affecting binding affinity to other FcγRs. In contrast, when testing hypofucosylated anti-RhD Abs with FcγRIIIa-expressing NK cells, a 12- and 7-fold increased erythrocyte lysis was observed with the IgG1 and IgG3, respectively, but no increase with IgG2 and IgG4 anti-RhD Abs. Notably, none of the hypofucosylated IgGs enhanced effector function of macrophages, which, in contrast to NK cells, express a complex set of FcγRs, including FcγRIIIa. Our data suggest that the beneficial effects of afucosylated biologicals for clinical use can be particularly anticipated when there is a substantial involvement of FcγRIIIa-expressing cells, such as NK cells.
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Affiliation(s)
- Christine W Bruggeman
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands;
| | - Gillian Dekkers
- Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Arthur E H Bentlage
- Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Louise W Treffers
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Sietse Q Nagelkerke
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Suzanne Lissenberg-Thunnissen
- Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Carolien A M Koeleman
- Center for Proteomics and Metabolomics, Leiden University Medical Center, 2300 RC Leiden, the Netherlands
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, 2300 RC Leiden, the Netherlands
| | - Timo K van den Berg
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Theo Rispens
- Department of Immunopathology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands; and
| | - Gestur Vidarsson
- Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands
| | - Taco W Kuijpers
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, the Netherlands.,Emma Children's Hospital, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam, the Netherlands
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53
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Abstract
Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.
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Affiliation(s)
- Ajit Varki
- Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California at San Diego, La Jolla, CA 92093-0687, USA
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54
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Bispecific Antibodies as a Development Platform for New Concepts and Treatment Strategies. Int J Mol Sci 2016; 18:ijms18010048. [PMID: 28036020 PMCID: PMC5297683 DOI: 10.3390/ijms18010048] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/16/2016] [Accepted: 12/21/2016] [Indexed: 12/11/2022] Open
Abstract
With the development of molecular cloning technology and the deep understanding of antibody engineering, there are diverse bispecific antibody formats from which to choose to pursue the optimal biological activity and clinical purpose. The single-chain-based bispecific antibodies usually bridge tumor cells with immune cells and form an immunological synapse because of their relatively small size. Bispecific antibodies in the IgG format include asymmetric bispecific antibodies and homodimerized bispecific antibodies, all of which have an extended blood half-life and their own crystalline fragment (Fc)-mediated functions. Besides retargeting effector cells to the site of cancer, new applications were established for bispecific antibodies. Bispecific antibodies that can simultaneously bind to cell surface antigens and payloads are a very ideal delivery system for therapeutic use. Bispecific antibodies that can inhibit two correlated signaling molecules at the same time can be developed to overcome inherent or acquired resistance and to be more efficient angiogenesis inhibitors. Bispecific antibodies can also be used to treat hemophilia A by mimicking the function of factor VIII. Bispecific antibodies also have broad application prospects in bone disorders and infections and diseases of the central nervous system. The latest developments of the formats and application of bispecific antibodies will be reviewed. Furthermore, the challenges and perspectives are summarized in this review.
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55
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Dekkers G, Plomp R, Koeleman CAM, Visser R, von Horsten HH, Sandig V, Rispens T, Wuhrer M, Vidarsson G. Multi-level glyco-engineering techniques to generate IgG with defined Fc-glycans. Sci Rep 2016; 6:36964. [PMID: 27872474 PMCID: PMC5131652 DOI: 10.1038/srep36964] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 10/21/2016] [Indexed: 12/20/2022] Open
Abstract
Immunoglobulin G (IgG) mediates its immune functions through complement and cellular IgG-Fc receptors (FcγR). IgG contains an evolutionary conserved N-linked glycan at position Asn297 in the Fc-domain. This glycan consists of variable levels of fucose, galactose, sialic acid, and bisecting N-acetylglucosamine (bisection). Of these variations, the lack of fucose strongly enhances binding to the human FcγRIII, a finding which is currently used to improve the efficacy of therapeutic monoclonal antibodies. The influence of the other glycan traits is largely unknown, mostly due to lack of glyco-engineering tools. We describe general methods to produce recombinant proteins of any desired glycoform in eukaryotic cells. Decoy substrates were used to decrease the level of fucosylation or galactosylation, glycosyltransferases were transiently overexpressed to enhance bisection, galactosylation and sialylation and in vitro sialylation was applied for enhanced sialylation. Combination of these techniques enable to systematically explore the biological effect of these glycosylation traits for IgG and other glycoproteins.
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Affiliation(s)
- Gillian Dekkers
- Sanquin Research, Department Experimental Immunohematology, Amsterdam, The Netherlands, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Rosina Plomp
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Carolien A. M. Koeleman
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Remco Visser
- Sanquin Research, Department Experimental Immunohematology, Amsterdam, The Netherlands, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Hans H. von Horsten
- ProBioGen AG, Berlin, Germany
- HTW-Berlin University of Applied Sciences, Life Science Engineering, Berlin, Germany
| | | | - Theo Rispens
- Sanquin Research, Department Immunopathology, Amsterdam, The Netherlands, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Gestur Vidarsson
- Sanquin Research, Department Experimental Immunohematology, Amsterdam, The Netherlands, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
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56
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Subedi GP, Barb AW. The immunoglobulin G1 N-glycan composition affects binding to each low affinity Fc γ receptor. MAbs 2016; 8:1512-1524. [PMID: 27492264 DOI: 10.1080/19420862.2016.1218586] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Immunoglobulin G1 (IgG1) is the most abundant circulating human antibody and also the scaffold for many therapeutic monoclonal antibodies (mAbs). The destruction of IgG-coated targets by cell-mediated pathways begins with an interaction between the IgG Fc region and multiple varieties of membrane-bound Fc γ receptors (FcγRs) on the surface of leukocytes. This interaction requires the presence of an asparagine-linked (N-)glycan on the Fc, and variations in the N-glycan composition can affect the affinity of CD16A binding (an FcγR). Contemporary efforts to glycoengineer mAbs focus on increasing CD16A affinity, and thus treatment efficacy, but it is unclear how these changes affect affinity for the other FcγRs. Here, we measure binding of the extracellular Fc-binding domains for human CD16A and B, CD32A, B and C, and CD64 to 6 well-defined IgG1 Fc glycoforms that cover ∼85% of the pool of human IgG1 Fc glycoforms. Core α1-6 fucosylation showed the greatest changes with CD16B (8.5-fold decrease), CD16A (3.9-fold decrease) and CD32B/C (1.8-fold decrease), but did not affect binding to CD32A. Adding galactose to the non-reducing termini of the complex-type, biantennary glycan increased affinity for all CD16s and 32s tested by 1.7-fold. Sialylation did not change the affinity of core-fucosylated Fc, but increased the affinity of afucosylated Fc slightly by an average of 1.16-fold for all CD16s and CD32s tested. The effects of fucose and galactose modification are additive, suggesting the contributions of these residues to Fc γ receptor affinity are independent.
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Affiliation(s)
- Ganesh P Subedi
- a Roy J. Carver Department of Biochemistry , Biophysics and Molecular Biology, Iowa State University , Ames , IA , USA
| | - Adam W Barb
- a Roy J. Carver Department of Biochemistry , Biophysics and Molecular Biology, Iowa State University , Ames , IA , USA
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57
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Chen W, Kong L, Connelly S, Dendle JM, Liu Y, Wilson IA, Powers ET, Kelly JW. Stabilizing the CH2 Domain of an Antibody by Engineering in an Enhanced Aromatic Sequon. ACS Chem Biol 2016; 11:1852-61. [PMID: 27128252 DOI: 10.1021/acschembio.5b01035] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Monoclonal antibodies (mAbs) exhibiting highly selective binding to a protein target constitute a large and growing proportion of the therapeutics market. Aggregation of mAbs results in the loss of their therapeutic efficacy and can result in deleterious immune responses. The CH2 domain comprising part of the Fc portion of Immunoglobulin G (IgG) is typically the least stable domain in IgG-type antibodies and therefore influences their aggregation propensity. We stabilized the CH2 domain by engineering an enhanced aromatic sequon (EAS) into the N-glycosylated C'E loop and observed a 4.8 °C increase in the melting temperature of the purified IgG1 Fc fragment. This EAS-stabilized CH2 domain also conferred enhanced stability against thermal and low pH induced aggregation in the context of a full-length monoclonal IgG1 antibody. The crystal structure of the EAS-stabilized (Q295F/Y296A) IgG1 Fc fragment confirms the design principle, i.e., the importance of the GlcNAc1•F295 interaction, and surprisingly reveals that the core fucose attached to GlcNAc1 also engages in an interaction with F295. Inhibition of core fucosylation confirms the contribution of the fucose-Phe interaction to the stabilization. The Q295F/Y296A mutations also modulate the binding affinity of the full-length antibody to Fc receptors by decreasing the binding to low affinity Fc gamma receptors (FcγRIIa, FcγRIIIa, and FcγRIIIb), while maintaining wild-type binding affinity to FcRn and FcγRI. Our results demonstrate that engineering an EAS into the N-glycosylated reverse turn on the C'E loop leads to stabilizing N-glycan-protein interactions in antibodies and that this modification modulates antibody-Fc receptor binding.
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Affiliation(s)
- Wentao Chen
- Department
of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
- Department
of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Leopold Kong
- Department
of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Stephen Connelly
- Department
of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Julia M. Dendle
- Department
of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
- Department
of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Yu Liu
- Department
of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
- Department
of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Ian A. Wilson
- Department
of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, United States
- The
Skaggs Institute for Chemical Biology, The Scripps Research Institute, La
Jolla, California 92037, United States
| | - Evan T. Powers
- Department
of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Jeffery W. Kelly
- Department
of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
- Department
of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States
- The
Skaggs Institute for Chemical Biology, The Scripps Research Institute, La
Jolla, California 92037, United States
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58
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Boulton S, Melacini G. Advances in NMR Methods To Map Allosteric Sites: From Models to Translation. Chem Rev 2016; 116:6267-304. [PMID: 27111288 DOI: 10.1021/acs.chemrev.5b00718] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The last five years have witnessed major developments in the understanding of the allosteric phenomenon, broadly defined as coupling between remote molecular sites. Such advances have been driven not only by new theoretical models and pharmacological applications of allostery, but also by progress in the experimental approaches designed to map allosteric sites and transitions. Among these techniques, NMR spectroscopy has played a major role given its unique near-atomic resolution and sensitivity to the dynamics that underlie allosteric couplings. Here, we highlight recent progress in the NMR methods tailored to investigate allostery with the goal of offering an overview of which NMR approaches are best suited for which allosterically relevant questions. The picture of the allosteric "NMR toolbox" is provided starting from one of the simplest models of allostery (i.e., the four-state thermodynamic cycle) and continuing to more complex multistate mechanisms. We also review how such an "NMR toolbox" has assisted the elucidation of the allosteric molecular basis for disease-related mutations and the discovery of novel leads for allosteric drugs. From this overview, it is clear that NMR plays a central role not only in experimentally validating transformative theories of allostery, but also in tapping the full translational potential of allosteric systems.
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Affiliation(s)
- Stephen Boulton
- Department of Chemistry and Chemical Biology Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main St. W., Hamilton L8S 4M1, Canada
| | - Giuseppe Melacini
- Department of Chemistry and Chemical Biology Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main St. W., Hamilton L8S 4M1, Canada
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59
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Production, Characterization, and Biological Evaluation of Well-Defined IgG1 Fc Glycoforms as a Model System for Biosimilarity Analysis. J Pharm Sci 2016; 105:559-574. [PMID: 26869419 DOI: 10.1016/j.xphs.2015.11.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 10/27/2015] [Accepted: 10/29/2015] [Indexed: 12/18/2022]
Abstract
Four different well-defined IgG1 Fc glycoforms are proposed as a model system to examine important biological and physicochemical features for protein drug biosimilar analyses. The IgG1 Fc glycoforms were produced by yeast expression combined with in vitro enzymatic synthesis as a series of sequentially truncated high-mannose IgG1 Fc glycoforms with an anticipated range of biological activity and structural stability. Initial characterization with mass spectrometry, SDS-PAGE, size exclusion HPLC, and capillary isoelectric focusing confirmed that the glycoproteins are overall highly similar with the only major difference being glycosylation state. Binding to the activating Fc receptor, FcγRIIIa was used to evaluate the potential biological activity of the IgG1 Fc glycoproteins. Two complementary methods using biolayer interferometry, 1 with protein G-immobilized IgG1 Fc and the other with streptavidin-immobilized FcγRIIIa, were developed to assess FcγRIIIa affinity in kinetic binding studies. The high-mannose IgG1 Fc and Man5-IgG1 Fc glycoforms were highly similar to one another with high affinity for FcγRIIIa, whereas GlcNAc-Fc had weak affinity, and the nonglycosylated N297Q-Fc had no measurable affinity for FcγRIIIa. These 4 IgG1 Fc glycoforms were also evaluated in terms of physical and chemical stability profiles and then used as a model system to mathematically assess overall biosimilarity, as described in a series of companion articles.
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60
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Subedi GP, Johnson RW, Moniz HA, Moremen KW, Barb AW. High Yield Expression of Recombinant Human Proteins with the Transient Transfection of HEK293 Cells in Suspension. J Vis Exp 2015:e53568. [PMID: 26779721 PMCID: PMC4780855 DOI: 10.3791/53568] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and function. The rapid establishment and high recovery from transiently-transfected mammalian cell lines addresses this barrier and is an effective means of expressing proteins that are naturally channeled through the ER and Golgi-mediated secretory pathway. Here is one protocol for protein expression using the human HEK293F and HEK293S cell lines transfected with a mammalian expression vector designed for high protein yields. The applicability of this system is demonstrated using three representative glycoproteins that expressed with yields between 95-120 mg of purified protein recovered per liter of culture. These proteins are the human FcγRIIIa and the rat α2-6 sialyltransferase, ST6GalI, both expressed with an N-terminal GFP fusion, as well as the unmodified human immunoglobulin G1 Fc. This robust system utilizes a serum-free medium that is adaptable for expression of isotopically enriched proteins and carbohydrates for structural studies using mass spectrometry and nuclear magnetic resonance spectroscopy. Furthermore, the composition of the N-glycan can be tuned by adding a small molecule to prevent certain glycan modifications in a manner that does not reduce yield.
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Affiliation(s)
- Ganesh P Subedi
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University
| | - Roy W Johnson
- Complex Carbohydrate Research Center, University of Georgia
| | | | | | - Adam W Barb
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University;
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61
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Mimura Y, Kelly RM, Unwin L, Albrecht S, Jefferis R, Goodall M, Mizukami Y, Mimura-Kimura Y, Matsumoto T, Ueoka H, Rudd PM. Enhanced sialylation of a human chimeric IgG1 variant produced in human and rodent cell lines. J Immunol Methods 2015; 428:30-6. [PMID: 26627984 DOI: 10.1016/j.jim.2015.11.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 11/11/2015] [Accepted: 11/23/2015] [Indexed: 12/11/2022]
Abstract
Glycosylation of the IgG-Fc is essential for optimal binding and activation of Fcγ receptors and the C1q component of complement. However, it has been reported that the effector functions are down-regulated when the Fc glycans terminate in sialic acid residues and that sialylated IgG mediates anti-inflammatory effects of intravenous immunoglobulin (IVIG). Although recombinant IgG is hypo-sialylated, Fc sialylation is shown to be markedly increased when a mouse/human chimeric IgG3 Phe243Ala (F243A) variant is expressed in Chinese hamster ovary (CHO)-K1 cells. Here we investigate whether sialylation is increased in IgG1 F243A when expressed in CHO-K1, mouse myeloma J558L and human embryonic kidney (HEK) 293. Although the sialylation level was 2-5% for IgG1 wild type (WT), it was increased to 31%, 10% and 33% for the variant from CHO-K1, J558L and HEK293 cells, respectively. Interestingly, an increased addition of bisecting GlcNAc and α(1-3)-galactose residues to the Fc glycan was observed for HEK293-derived and J558L-derived IgG1 F243A, respectively. Fucosylation of HEK293-derived IgG1 F243A was maintained despite increased bisecting GlcNAc content. Although sialic acid and bisecting GlcNAc residues are reported to have an opposing effect on antibody-dependent cellular cytotoxicity (ADCC), IgG1 F243A showed 7 times lower ADCC activities than IgG1 WT, irrespective of bisecting GlcNAc residue. Thus, highly sialylated, human cell-derived IgG1 F243A with lowered ADCC activity may be of interest for the development of therapeutic antibodies with anti-inflammatory properties as an alternative to IVIG.
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Affiliation(s)
- Yusuke Mimura
- Department of Clinical Research, NHO Yamaguchi-Ube Medical Center, 685 Higashi-Kiwa, Ube 755-0241, Japan; NIBRT GlycoScience Group, National Institute for Bioprocessing Research and Training, Mount Merrion, Blackrock, Dublin 4, Ireland.
| | - Ronan M Kelly
- NIBRT GlycoScience Group, National Institute for Bioprocessing Research and Training, Mount Merrion, Blackrock, Dublin 4, Ireland; Eli Lilly and Company, Indianapolis, USA
| | - Louise Unwin
- NIBRT GlycoScience Group, National Institute for Bioprocessing Research and Training, Mount Merrion, Blackrock, Dublin 4, Ireland
| | - Simone Albrecht
- NIBRT GlycoScience Group, National Institute for Bioprocessing Research and Training, Mount Merrion, Blackrock, Dublin 4, Ireland
| | - Roy Jefferis
- School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Margaret Goodall
- School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Yoichi Mizukami
- Center for Gene Research, Yamaguchi University, 1-1-1 Minami-Kogushi, Ube 755-8505, Japan
| | - Yuka Mimura-Kimura
- Department of Clinical Research, NHO Yamaguchi-Ube Medical Center, 685 Higashi-Kiwa, Ube 755-0241, Japan; NIBRT GlycoScience Group, National Institute for Bioprocessing Research and Training, Mount Merrion, Blackrock, Dublin 4, Ireland
| | - Tsuneo Matsumoto
- Department of Clinical Research, NHO Yamaguchi-Ube Medical Center, 685 Higashi-Kiwa, Ube 755-0241, Japan
| | - Hiroshi Ueoka
- Department of Clinical Research, NHO Yamaguchi-Ube Medical Center, 685 Higashi-Kiwa, Ube 755-0241, Japan
| | - Pauline M Rudd
- NIBRT GlycoScience Group, National Institute for Bioprocessing Research and Training, Mount Merrion, Blackrock, Dublin 4, Ireland
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62
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Caaveiro JMM, Kiyoshi M, Tsumoto K. Structural analysis of Fc/FcγR complexes: a blueprint for antibody design. Immunol Rev 2015; 268:201-21. [DOI: 10.1111/imr.12365] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Jose M. M. Caaveiro
- Department of Bioengineering; School of Engineering; The University of Tokyo; Tokyo Japan
| | - Masato Kiyoshi
- Department of Bioengineering; School of Engineering; The University of Tokyo; Tokyo Japan
- Division of Biological Chemistry and Biologicals; National Institute of Health Sciences; Tokyo Japan
| | - Kouhei Tsumoto
- Department of Bioengineering; School of Engineering; The University of Tokyo; Tokyo Japan
- Institute of Medical Science; The University of Tokyo; Tokyo Japan
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63
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Subedi GP, Barb AW. The Structural Role of Antibody N-Glycosylation in Receptor Interactions. Structure 2015; 23:1573-1583. [PMID: 26211613 PMCID: PMC4558368 DOI: 10.1016/j.str.2015.06.015] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 06/08/2015] [Accepted: 06/10/2015] [Indexed: 01/06/2023]
Abstract
Asparagine(N)297-linked glycosylation of immunoglobulin G (IgG) Fc is required for binding to FcγRIIa, IIb, and IIIa, although it is unclear how it contributes. We found the quaternary structure of glycosylated Fc was indistinguishable from aglycosylated Fc, indicating that N-glycosylation does not maintain relative Fc Cγ2/Cγ3 domain orientation. However, the conformation of the C'E loop, which contains N297, was significantly perturbed in the aglycosylated Fc variant. The conformation of the C'E loop as measured with a range of Fc variants shows a strong correlation with FcγRIIIa affinity. These results indicate that the primary role of the IgG1 Fc N-glycan is to stabilize the C'E loop through intramolecular interactions between carbohydrate and amino acid residues, and preorganize the FcγRIIIa interface for optimal binding affinity. The features that contribute to the capacity of the IgG1 Fc N-glycan to restrict protein conformation and tune binding affinity are conserved in other antibodies including IgG2-IgG4, IgD, IgE, and IgM.
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Affiliation(s)
- Ganesh P Subedi
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 2214 Molecular Biology Building, Ames, IA 50011, USA
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 2214 Molecular Biology Building, Ames, IA 50011, USA.
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Marcella AM, Jing F, Barb AW. Preparation of holo- and malonyl-[acyl-carrier-protein] in a manner suitable for analog development. Protein Expr Purif 2015; 115:39-45. [PMID: 26008118 DOI: 10.1016/j.pep.2015.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 12/31/2022]
Abstract
The fatty acid biosynthetic pathway generates highly reduced carbon based molecules. For this reason fatty acid synthesis is a target of pathway engineering to produce novel specialty or commodity chemicals using renewable techniques to supplant molecules currently derived from petroleum. Malonyl-[acyl carrier protein] (malonyl-ACP) is a key metabolite in the fatty acid pathway and donates two carbon units to the growing fatty acid chain during each step of biosynthesis. Attempts to test engineered fatty acid biosynthesis enzymes in vitro will require malonyl-ACP or malonyl-ACP analogs. Malonyl-ACP is challenging to prepare due to the instability of the carboxylate leaving group and the multiple steps of post-translational modification required to activate ACP. Here we report the expression and purification of holo- and malonyl-ACP from Escherichia coli with high yields (>15 mg per L of expression). The malonyl-ACP is efficiently recognized by the E. coli keto-acyl synthase enzyme, FabH. A FabH assay using malonyl-ACP and a coumarin-based fluorescent reagent is described that provides a high throughput alternative to reported radioactive assays.
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Affiliation(s)
- Aaron M Marcella
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, United States
| | - Fuyuan Jing
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, United States
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, United States.
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Hanson QM, Barb AW. A perspective on the structure and receptor binding properties of immunoglobulin G Fc. Biochemistry 2015; 54:2931-42. [PMID: 25926001 DOI: 10.1021/acs.biochem.5b00299] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Recombinant antibodies spurred a revolution in medicine that saw the introduction of powerful therapeutics for treating a wide range of diseases, from cancers to autoimmune disorders and transplant rejection, with more applications looming on the horizon. Many of these therapeutic monoclonal antibodies (mAbs) are based on human immunoglobulin G1 (IgG1) or contain at least a portion of the molecule. Most mAbs require interactions with cell surface receptors for efficacy, including the Fc γ receptors. High-resolution structural models of antibodies and antibody fragments have been available for nearly 40 years; however, a thorough description of the structural features that determine the affinity with which antibodies interact with human receptors has not been published. In this review, we will cover the relevant history of IgG-related literature and how recent developments have changed our view of critical antibody-cell interactions at the atomic level with a nod to outstanding questions in the field and future prospects.
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Affiliation(s)
- Quinlin M Hanson
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 2214 Molecular Biology Building, Ames, Iowa 50011, United States
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 2214 Molecular Biology Building, Ames, Iowa 50011, United States
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Barb AW. Intramolecular N-glycan/polypeptide interactions observed at multiple N-glycan remodeling steps through [(13)C,(15)N]-N-acetylglucosamine labeling of immunoglobulin G1. Biochemistry 2014; 54:313-22. [PMID: 25551295 PMCID: PMC4302832 DOI: 10.1021/bi501380t] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
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Asparagine-linked (N) glycosylation
is a common eukaryotic protein
modification that affects protein folding, function, and stability
through intramolecular interactions between N-glycan
and polypeptide residues. Attempts to characterize the structure–activity
relationship of each N-glycan are hindered by inherent
properties of the glycoprotein, including glycan conformational and
compositional heterogeneity. These limitations can be addressed by
using a combination of nuclear magnetic resonance techniques following
enzymatic glycan remodeling to simultaneously generate homogeneous
glycoforms. However, widely applicable methods do not yet exist. To
address this technological gap, immature glycoforms of the immunoglobulin
G1 fragment crystallizable (Fc) were isolated in a homogeneous state
and enzymatically remodeled with [13C,15N]-N-acetylglucosamine (GlcNAc). UDP-[13C,15N]GlcNAc was synthesized enzymatically in a one-pot reaction from
[13C]glucose and [15N-amido]glutamine. Modifying Fc with recombinantly expressed glycosyltransferases
(Gnt1 and Gnt2) and UDP-[13C,15N]GlcNAc resulted
in complete glycoform conversion as judged by mass spectrometry. Two-dimensional
heteronuclear single-quantum coherence spectra of the Gnt1 product,
containing a single [13C,15N]GlcNAc residue
on each N-glycan, showed that the N-glycan is stabilized through interactions with polypeptide residues.
Similar spectra of homogeneous glycoforms, halted at different points
along the N-glycan remodeling pathway, revealed the
presence of an increased level of interaction between the N-glycan and polypeptide at each step, including mannose
trimming, as the N-glycan was converted to a complex-type,
biantennary form. Thus, conformational restriction increases as Fc N-glycan maturation proceeds. Gnt1 and Gnt2 catalyze fundamental
reactions in the synthesis of every glycoprotein with a complex-type N-glycan; thus, the strategies presented herein can be applied
to a broad range of glycoprotein studies.
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Affiliation(s)
- Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University , Ames, Iowa 50011, United States
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