1
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Chaisupa P, Wright RC. State-of-the-art in engineering small molecule biosensors and their applications in metabolic engineering. SLAS Technol 2024; 29:100113. [PMID: 37918525 PMCID: PMC11314541 DOI: 10.1016/j.slast.2023.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 10/18/2023] [Accepted: 10/25/2023] [Indexed: 11/04/2023]
Abstract
Genetically encoded biosensors are crucial for enhancing our understanding of how molecules regulate biological systems. Small molecule biosensors, in particular, help us understand the interaction between chemicals and biological processes. They also accelerate metabolic engineering by increasing screening throughput and eliminating the need for sample preparation through traditional chemical analysis. Additionally, they offer significantly higher spatial and temporal resolution in cellular analyte measurements. In this review, we discuss recent progress in in vivo biosensors and control systems-biosensor-based controllers-for metabolic engineering. We also specifically explore protein-based biosensors that utilize less commonly exploited signaling mechanisms, such as protein stability and induced degradation, compared to more prevalent transcription factor and allosteric regulation mechanism. We propose that these lesser-used mechanisms will be significant for engineering eukaryotic systems and slower-growing prokaryotic systems where protein turnover may facilitate more rapid and reliable measurement and regulation of the current cellular state. Lastly, we emphasize the utilization of cutting-edge and state-of-the-art techniques in the development of protein-based biosensors, achieved through rational design, directed evolution, and collaborative approaches.
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Affiliation(s)
- Patarasuda Chaisupa
- Department of Biological Systems Engineering, Virginia Tech, Blacksburg, VA 24061, United States
| | - R Clay Wright
- Department of Biological Systems Engineering, Virginia Tech, Blacksburg, VA 24061, United States; Translational Plant Sciences Center (TPSC), Virginia Tech, Blacksburg, VA 24061, United States.
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2
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Smith ES, Balch LA, Scrivens M, Shi S, Wang W, Harvey CD, Cornelison AA, Gil-Moore M, Kirk RA, Mueller LL, Hall RL, Howell AP, Reilly CA, Mayer JM, Murante FG, Viggiani KA, Gersz EM, Bussler H, Keefe MR, Evans EE, Paris MJ, Zauderer M. Use of poxvirus display to select antibodies specific for complex membrane antigens. MAbs 2023; 15:2249947. [PMID: 37635331 PMCID: PMC10464538 DOI: 10.1080/19420862.2023.2249947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 08/15/2023] [Accepted: 08/16/2023] [Indexed: 08/29/2023] Open
Abstract
Antibody discovery against complex antigens is limited by the availability of a reproducible pure source of concentrated properly folded antigen. We have developed a technology to enable direct incorporation of membrane proteins such as GPCRs and into the membrane of poxvirus. The protein of interest is correctly folded and expressed in the cell-derived viral membrane and does not require any detergents or refolding before downstream use. The poxvirus is selective in which proteins are incorporated into the viral membrane, making the antigen poxvirus an antigenically cleaner target for in vitro panning. Antigen-expressing virus can be readily purified at scale and used for antibody selection using any in vitro display platform.
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Affiliation(s)
| | | | | | | | - Wei Wang
- Research, Vaccinex, Inc, Rochester, NY, USA
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3
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Production of human embryonic kidney 293T cells stably expressing C-X-C chemokine receptor type 4 (CXCR4) as a screening tool for anticancer lead compound targeting CXCR4. Life Sci 2022; 303:120661. [PMID: 35643380 DOI: 10.1016/j.lfs.2022.120661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 05/19/2022] [Accepted: 05/23/2022] [Indexed: 11/24/2022]
Abstract
AIM The C-X-C chemokine-receptor type 4 (CXCR4) is an emerging target for cancer drug discovery due to its high expression in cancer cells. The present study aimed to produce CXCR4 overexpressing HEK293T cells for a non-radioactive binding assay as a platform to identify drug candidates targeting CXCR4. MAIN METHODS HEK293T cells stably expressing human CXCR4 were constructed by transfection of CXCR4 plasmids from the human CXCR4 gene. The CXCR4 overexpressing HEK293T cells were obtained by fluorescence-activated sorting and verified by conducting the competition binding assay of a known CXCR4 inhibitor, AMD3100 (plerixafor), to determine the IC50 value against monoclonal anti-human CD184 (hCD184) antibody tagged with fluorescence probe, phycoerythrin (PE). The non-radioactive binding assay using CXCR4 overexpressing HEK293T cells and PE-anti hCD184 was applied as a platform for identifying the target of natural compounds that exhibited cytotoxicity against cancer cell lines. KEY FINDINGS The CXCR4 overexpressing HEK293T cells were produced with high expression (99.8%). The IC50 value of plerixafor determined by fluorescence tagged antibody-based competition assay using our developed cells agree with previously reported values using a radioligand binding assay. We observed no significant displacement of bound PE-anti-hCD184 by the test natural compounds which could be due to non-specific binding to other functional targets or organelles, low potency of the natural compounds, or binding to CXCR4 at deeper pockets. SIGNIFICANCE The verified non-radioactive binding assay can serve as an alternative screening tool for anticancer lead compounds targeting CXCR4 and an essential tool for proof of mechanism study in the drug discovery.
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4
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Shin G, Lim SI. Site-specific proximity ligation provides molecular insights into biologically relevant interfaces of protein-protein interaction. Biochem Biophys Res Commun 2020; 533:932-937. [PMID: 33008597 DOI: 10.1016/j.bbrc.2020.09.097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 09/10/2020] [Accepted: 09/23/2020] [Indexed: 11/30/2022]
Abstract
Dynamic protein-protein interactions (PPIs) are fundamental to spatiotemporal control of protein functions in biological systems. Dissecting binding interfaces in aqueous solution (i.e., biological interfaces) is of great importance for identifying molecular determinants that contribute to the affinity and specificity of PPIs. Herein, we describe a biochemical method, termed site-specific proximity ligation (SPL), that enables the identification and reconstruction of native binding interfaces distinct from those present in crystal structures and models from computational prediction. SPL involves the strategic incorporation of an aryl azide-containing unnatural amino acid (AZF) into residues of interest in a particular protein that forms a multiprotein complex. Depending on the interfacial role of a targeted residue, a photo-inducible highly reactive incorporated AZF moiety may react with neighboring functional groups to covalently capture an otherwise non-covalent or weak interaction with a specific partner protein, thereby revealing the landscape of biological interfaces. Using a heterotrimeric nuclear pore protein as a model, we show that the biological interfaces of the complex mapped by SPL provide new insight into dynamic molecular recognition that is missed by, or even in conflict with, static models.
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Affiliation(s)
- Goeun Shin
- Department of Chemical Engineering, Pukyong National University, Yongso-ro 45, Nam-gu, Busan, Republic of Korea
| | - Sung In Lim
- Department of Chemical Engineering, Pukyong National University, Yongso-ro 45, Nam-gu, Busan, Republic of Korea.
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5
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Photosensitive tyrosine analogues unravel site-dependent phosphorylation in TrkA initiated MAPK/ERK signaling. Commun Biol 2020; 3:706. [PMID: 33239753 PMCID: PMC7689462 DOI: 10.1038/s42003-020-01396-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 10/14/2020] [Indexed: 01/01/2023] Open
Abstract
Tyrosine kinase A (TrkA) is a membrane receptor which, upon ligand binding, activates several pathways including MAPK/ERK signaling, implicated in a spectrum of human pathologies; thus, TrkA is an emerging therapeutic target in treatment of neuronal diseases and cancer. However, mechanistic insights into TrKA signaling are lacking due to lack of site-dependent phosphorylation control. Here we engineer two light-sensitive tyrosine analogues, namely p-azido-L-phenylalanine (AzF) and the caged-tyrosine (ONB), through amber codon suppression to optically manipulate the phosphorylation state of individual intracellular tyrosines in TrkA. We identify TrkA-AzF and ONB mutants, which can activate the ERK pathway in the absence of NGF ligand binding through light control. Our results not only reveal how TrkA site-dependent phosphorylation controls the defined signaling process, but also extend the genetic code expansion technology to enable regulation of receptor-type kinase activation by optical control at the precision of a single phosphorylation site. It paves the way for comprehensive analysis of kinase-associated pathways as well as screening of compounds intervening in a site-directed phosphorylation pathway for targeted therapy. Using genetic code expansion, Zhao, Shi et al. generate light-sensitive tyrosine analogues to obtain insights into the activation of the NGF receptor, TrkA. They identify light-sensitive and NGF-insensitive phosphorylation sites, validating the approach and providing insights into TrkA signaling
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6
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Microtiter plate-based antibody-competition assay to determine binding affinities and plasma/blood stability of CXCR4 ligands. Sci Rep 2020; 10:16036. [PMID: 32994431 PMCID: PMC7525492 DOI: 10.1038/s41598-020-73012-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 09/07/2020] [Indexed: 12/28/2022] Open
Abstract
C-X-C chemokine receptor type 4 (CXCR4) is involved in several intractable disease processes, including HIV infection, cancer cell metastasis, leukemia cell progression, rheumatoid arthritis, asthma and pulmonary fibrosis. Thus, CXCR4 represents a promising drug target and several CXCR4 antagonizing agents are in preclinical or clinical development. Important parameters in drug lead evaluation are determination of binding affinities to the receptor and assessment of their stability and activity in plasma or blood of animals and humans. Here, we designed a microtiter plate-based CXCR4 antibody competition assay that enables to measure inhibitory concentrations (IC50 values) and affinity constants (Ki values) of CXCR4 targeting drugs. The assay is based on the observation that most if not all CXCR4 antagonists compete with binding of the fluorescence-tagged CXCR4 antibody 12G5 to the receptor. We demonstrate that this antibody-competition assay allows a convenient and cheap determination of binding affinities of various CXCR4 antagonists in living cells within just 3 h. Moreover, the assay can be performed in the presence of high concentrations of physiologically relevant body fluids, and thus is a useful readout to evaluate stability (i.e. half-life) of CXCR4 ligands in serum/plasma, and even whole human and mouse blood ex vivo. Thus, this optimized 12G5 antibody-competition assay allows a robust and convenient determination and calculation of various important pharmacological parameters of CXCR4 receptor-drug interaction and may not only foster future drug development but also animal welfare by reducing the number of experimental animals.
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7
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Shah UH, Toneatti R, Gaitonde SA, Shin JM, González-Maeso J. Site-Specific Incorporation of Genetically Encoded Photo-Crosslinkers Locates the Heteromeric Interface of a GPCR Complex in Living Cells. Cell Chem Biol 2020; 27:1308-1317.e4. [PMID: 32726588 DOI: 10.1016/j.chembiol.2020.07.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 05/04/2020] [Accepted: 07/08/2020] [Indexed: 01/02/2023]
Abstract
G protein-coupled receptors (GPCRs) are critical mediators of cell signaling. Although capable of activating G proteins in a monomeric form, numerous studies reveal a possible association of class A GPCRs into dimers/oligomers. The relative location of individual protomers within these GPCR complexes remains a topic of intense debate. We previously reported that class A serotonin 5-HT2A receptor (5-HT2AR) and class C metabotropic glutamate 2 receptor (mGluR2) are able to form a GPCR heterocomplex. By introducing the photoactivatable unnatural amino acid p-azido-L-phenylalanine (azF) at selected individual positions along the transmembrane (TM) segments of mGluR2, we delineate the residues that physically interact at the heteromeric interface of the 5-HT2AR-mGluR2 complex. We show that 5-HT2AR crosslinked with azF incorporated at the intracellular end of mGluR2's TM4, while no crosslinking was observed at other positions along TM1 and TM4. Together, these findings provide important insights into the structural arrangement of the 5-HT2AR-mGluR2 complex.
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Affiliation(s)
- Urjita H Shah
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Rudy Toneatti
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Supriya A Gaitonde
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Jong M Shin
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Javier González-Maeso
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA.
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8
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Won Y, Pagar AD, Patil MD, Dawson PE, Yun H. Recent Advances in Enzyme Engineering through Incorporation of Unnatural Amino Acids. BIOTECHNOL BIOPROC E 2019. [DOI: 10.1007/s12257-019-0163-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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9
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Nödling AR, Spear LA, Williams TL, Luk LYP, Tsai YH. Using genetically incorporated unnatural amino acids to control protein functions in mammalian cells. Essays Biochem 2019; 63:237-266. [PMID: 31092687 PMCID: PMC6610526 DOI: 10.1042/ebc20180042] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 03/14/2019] [Accepted: 03/19/2019] [Indexed: 02/07/2023]
Abstract
Genetic code expansion allows unnatural (non-canonical) amino acid incorporation into proteins of interest by repurposing the cellular translation machinery. The development of this technique has enabled site-specific incorporation of many structurally and chemically diverse amino acids, facilitating a plethora of applications, including protein imaging, engineering, mechanistic and structural investigations, and functional regulation. Particularly, genetic code expansion provides great tools to study mammalian proteins, of which dysregulations often have important implications in health. In recent years, a series of methods has been developed to modulate protein function through genetically incorporated unnatural amino acids. In this review, we will first discuss the basic concept of genetic code expansion and give an up-to-date list of amino acids that can be incorporated into proteins in mammalian cells. We then focus on the use of unnatural amino acids to activate, inhibit, or reversibly modulate protein function by translational, optical or chemical control. The features of each approach will also be highlighted.
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Affiliation(s)
| | - Luke A Spear
- School of Chemistry, Cardiff University, Cardiff, Wales, United Kingdom
| | - Thomas L Williams
- School of Chemistry, Cardiff University, Cardiff, Wales, United Kingdom
| | - Louis Y P Luk
- School of Chemistry, Cardiff University, Cardiff, Wales, United Kingdom
| | - Yu-Hsuan Tsai
- School of Chemistry, Cardiff University, Cardiff, Wales, United Kingdom
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10
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Miyazaki R, Akiyama Y, Mori H. A photo-cross-linking approach to monitor protein dynamics in living cells. Biochim Biophys Acta Gen Subj 2019; 1864:129317. [PMID: 30851405 DOI: 10.1016/j.bbagen.2019.03.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/26/2019] [Accepted: 03/04/2019] [Indexed: 11/16/2022]
Abstract
BACKGROUND Proteins, which comprise one of the major classes of biomolecules that constitute a cell, interact with other cellular factors during both their biogenesis and functional states. Studying not only static but also transient interactions of proteins is important to understand their physiological roles and regulation mechanisms. However, only a limited number of methods are available to analyze the dynamic behaviors of proteins at the molecular level in a living cell. The site-directed in vivo photo-cross-linking approach is an elegant technique to capture protein interactions with high spatial resolution in a living cell. SCOPE OF REVIEW Here, we review the in vivo photo-cross-linking approach including its recent applications and the potential problems to be considered. We also introduce a new in vivo photo-cross-linking-based technique (PiXie) to study protein dynamics with high spatiotemporal resolution. MAJOR CONCLUSIONS In vivo photo-cross-linking enables us to capture weak/transient protein interactions with high spatial resolution, and allows for identification of interacting factors. Moreover, the PiXie approach can be used to monitor rapid folding/assembly processes of proteins in living cells. GENERAL SIGNIFICANCE In vivo photo-cross-linking is a simple method that has been used to analyze the dynamic interactions of many cellular proteins. Originally developed in Escherichia coli, this system has been extended to studies in various organisms, making it a fundamental technique for investigating dynamic protein interactions in many cellular processes. This article is part of a Special issue entitled "Novel major techniques for visualizing 'live' protein molecules" edited by Dr. Daisuke Kohda.
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Affiliation(s)
- Ryoji Miyazaki
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Yoshinori Akiyama
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Hiroyuki Mori
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
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11
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Nguyen TA, Cigler M, Lang K. Expanding the Genetic Code to Study Protein-Protein Interactions. Angew Chem Int Ed Engl 2018; 57:14350-14361. [PMID: 30144241 DOI: 10.1002/anie.201805869] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 08/20/2018] [Indexed: 12/19/2022]
Abstract
Protein-protein interactions are central to many biological processes. A considerable challenge consists however in understanding and deciphering when and how proteins interact, and this can be particularly difficult when interactions are weak and transient. The site-specific incorporation of unnatural amino acids (UAAs) that crosslink with nearby molecules in response to light provides a powerful tool for mapping transient protein-protein interactions and for defining the structure and topology of protein complexes both in vitro and in vivo. Complementary strategies consist in site-specific incorporation of UAAs bearing electrophilic moieties that react with natural nucleophilic amino acids in a proximity-dependent manner, thereby chemically stabilizing low-affinity interactions and providing additional constraints on distances and geometries in protein complexes. Herein, we review how UAAs bearing fine-tuned chemical moieties that react with proteins in their vicinity can be utilized to map, study, and characterize weak and transient protein-protein interactions in living systems.
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Affiliation(s)
- Tuan-Anh Nguyen
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Group of Synthetic Biochemistry, Technical University of Munich, Institute for Advanced Study, Lichtenbergstr. 4, 85748, Garching, Germany
| | - Marko Cigler
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Group of Synthetic Biochemistry, Technical University of Munich, Institute for Advanced Study, Lichtenbergstr. 4, 85748, Garching, Germany
| | - Kathrin Lang
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Group of Synthetic Biochemistry, Technical University of Munich, Institute for Advanced Study, Lichtenbergstr. 4, 85748, Garching, Germany
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12
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Nguyen TA, Cigler M, Lang K. Expanding the Genetic Code to Study Protein-Protein Interactions. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201805869] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Tuan-Anh Nguyen
- Center for Integrated Protein Science Munich (CIPSM); Department of Chemistry; Group of Synthetic Biochemistry; Technical University of Munich; Institute for Advanced Study; Lichtenbergstr. 4 85748 Garching Germany
| | - Marko Cigler
- Center for Integrated Protein Science Munich (CIPSM); Department of Chemistry; Group of Synthetic Biochemistry; Technical University of Munich; Institute for Advanced Study; Lichtenbergstr. 4 85748 Garching Germany
| | - Kathrin Lang
- Center for Integrated Protein Science Munich (CIPSM); Department of Chemistry; Group of Synthetic Biochemistry; Technical University of Munich; Institute for Advanced Study; Lichtenbergstr. 4 85748 Garching Germany
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13
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Huang Y, Liu T. Therapeutic applications of genetic code expansion. Synth Syst Biotechnol 2018; 3:150-158. [PMID: 30345400 PMCID: PMC6190509 DOI: 10.1016/j.synbio.2018.09.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 09/16/2018] [Accepted: 09/18/2018] [Indexed: 12/05/2022] Open
Abstract
In nature, a limited, conservative set of amino acids are utilized to synthesize proteins. Genetic code expansion technique reassigns codons and incorporates noncanonical amino acids (ncAAs) through orthogonal aminoacyl-tRNA synthetase (aaRS)/tRNA pairs. The past decade has witnessed the rapid growth in diversity and scope for therapeutic applications of this technology. Here, we provided an update on the recent progress using genetic code expansion in the following areas: antibody-drug conjugates (ADCs), bispecific antibodies (BsAb), immunotherapies, long-lasting protein therapeutics, biosynthesized peptides, engineered viruses and cells, as well as other therapeutic related applications, where the technique was used to elucidate the mechanisms of biotherapeutics and drug targets.
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Affiliation(s)
| | - Tao Liu
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
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14
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Heredia JD, Park J, Brubaker RJ, Szymanski SK, Gill KS, Procko E. Mapping Interaction Sites on Human Chemokine Receptors by Deep Mutational Scanning. THE JOURNAL OF IMMUNOLOGY 2018; 200:3825-3839. [PMID: 29678950 DOI: 10.4049/jimmunol.1800343] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 03/30/2018] [Indexed: 02/02/2023]
Abstract
Chemokine receptors CXCR4 and CCR5 regulate WBC trafficking and are engaged by the HIV-1 envelope glycoprotein gp120 during infection. We combine a selection of human CXCR4 and CCR5 libraries comprising nearly all of ∼7000 single amino acid substitutions with deep sequencing to define sequence-activity landscapes for surface expression and ligand interactions. After consideration of sequence constraints for surface expression, known interaction sites with HIV-1-blocking Abs were appropriately identified as conserved residues following library sorting for Ab binding, validating the use of deep mutational scanning to map functional interaction sites in G protein-coupled receptors. Chemokine CXCL12 was found to interact with residues extending asymmetrically into the CXCR4 ligand-binding cavity, similar to the binding surface of CXCR4 recognized by an antagonistic viral chemokine previously observed crystallographically. CXCR4 mutations distal from the chemokine binding site were identified that enhance chemokine recognition. This included disruptive mutations in the G protein-coupling site that diminished calcium mobilization, as well as conservative mutations to a membrane-exposed site (CXCR4 residues H792.45 and W1614.50) that increased ligand binding without loss of signaling. Compared with CXCR4-CXCL12 interactions, CCR5 residues conserved for gp120 (HIV-1 BaL strain) interactions map to a more expansive surface, mimicking how the cognate chemokine CCL5 makes contacts across the entire CCR5 binding cavity. Acidic substitutions in the CCR5 N terminus and extracellular loops enhanced gp120 binding. This study demonstrates how comprehensive mutational scanning can define functional interaction sites on receptors, and novel mutations that enhance receptor activities can be found simultaneously.
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Affiliation(s)
- Jeremiah D Heredia
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Jihye Park
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Riley J Brubaker
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Steven K Szymanski
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Kevin S Gill
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Erik Procko
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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15
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Seidel L, Coin I. Mapping of Protein Interfaces in Live Cells Using Genetically Encoded Crosslinkers. Methods Mol Biol 2018; 1728:221-235. [PMID: 29405001 DOI: 10.1007/978-1-4939-7574-7_14] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the topology of protein-protein interactions is a matter of fundamental importance in the biomedical field. Biophysical approaches such as X-ray crystallography and nuclear magnetic resonance can investigate in detail only isolated protein complexes that are reconstituted in an artificial environment. Alternative methods are needed to investigate protein interactions in a physiological context, as well as to characterize protein complexes that elude the direct structural characterization. We describe here a general strategy to investigate protein interactions at the molecular level directly in the live mammalian cell, which is based on the genetic incorporation of photo- and chemical crosslinking noncanonical amino acids. First a photo-crosslinking amino acid is used to map putative interaction surfaces and determine which positions of a protein come into proximity of an associated partner. In a second step, the subset of residues that belong to the binding interface are substituted with a chemical crosslinker that reacts selectively with proximal cysteines strategically placed in the interaction partner. This allows determining inter-molecular spatial constraints that provide the basis for building accurate molecular models. In this chapter, we illustrate the detailed application of this experimental strategy to unravel the binding modus of the 40-mer neuropeptide hormone Urocortin1 to its class B G-protein coupled receptor, the corticotropin releasing factor receptor type 1. The approach is in principle applicable to any protein complex independent of protein type and size, employs established techniques of noncanonical amino acid mutagenesis, and is feasible in any molecular biology laboratory.
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Affiliation(s)
- Lisa Seidel
- Institute of Biochemistry, University of Leipzig, Leipzig, Germany
| | - Irene Coin
- Institute of Biochemistry, University of Leipzig, Leipzig, Germany.
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16
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Huber T, Sakmar TP. Probing Antibody Binding Sites on G Protein-Coupled Receptors Using Genetically Encoded Photo-Activatable Cross-Linkers. Methods Mol Biol 2018; 1785:65-75. [PMID: 29714012 DOI: 10.1007/978-1-4939-7841-0_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We describe a methodology to map epitopes of monoclonal antibodies that bind to G protein-coupled receptors (GPCRs). The method relies on an amber codon suppression strategy to genetically encode photo-activatable cross-linkers, such as p-azido-L-phenylalanine (azF) or p-benzoly-L-phenylalanine (BzF), in GPCRs expressed in mammalian cells in culture. Individual receptor variants that harbor a site-specific photo-crosslinker residue can be assayed for functional activity in standard cell-based assays. The interaction sites between the receptor variants and an antibody can be mapped by determining which of the azF or BzF residues cross-link to the antibody upon UV irradiation. A whole cell enzyme-linked immunosorbent assay (ELISA) is used to quantiate cross-linking efficiency. A binding "footprint" of the antibody of the surface of the receptor is obtained by comparing the sites of amino acid replacements that cause loss of antibody binding with those that create colvalent cross-links with bound antibody. The precision of the receptor-antibody binding-site map is determined by the number of mutants tested and whether or not high resolution crystal structures or homology models are available. The targeted photo-cross-linking method is complementary to loss-of-function mutagenesis and is especially useful to study anti-receptor antibodies with discontinuous epitopes.
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Affiliation(s)
- Thomas Huber
- Laboratory of Chemical Biology and Signal Transduction, The Rockefeller University, New York, NY, USA
| | - Thomas P Sakmar
- Laboratory of Chemical Biology and Signal Transduction, The Rockefeller University, New York, NY, USA.
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17
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Chen Y, Lu L, Ye S. Genetic Code Expansion and Optoproteomics. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2017; 90:599-610. [PMID: 29259524 PMCID: PMC5733852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Nature has invented photoreceptor proteins that are involved in sensing and response to light in living organisms. Genetic code expansion (GCE) technology has provided new tools to transform light insensitive proteins into novel photoreceptor proteins. It is achieved by the site-specific incorporation of unnatural amino acids (Uaas) that carry light sensitive moieties serving as "pigments" that react to light via photo-decaging, cross-linking, or isomerization. Over the last two decades, various proteins including ion channels, GPCRs, transporters, and kinases have been successfully rendered light responsive owing to the functionalities of Uaas. Very recently, Cas9 protein has been engineered to enable light activation of genomic editing by CRISPR. Those novel proteins have not only led to discoveries of dynamic protein conformational changes with implications in diseases, but also facilitated the screening of ligand-protein and protein-protein interactions of pharmacological significance. This review covers the genetic editing principles for genetic code expansion and design concepts that guide the engineering of light-sensitive proteins. The applications have brought up a new concept of "optoproteomics" that, in contrast to "optogenetics," aims to combine optical methods and site-specific proteomics for investigating and intervening in biological functions.
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Affiliation(s)
- Yuting Chen
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University (ECNU), Shanghai, China
| | - Linjie Lu
- Université Pierre-et-Marie-Curie, Laboratory of Computational and Quantitative Biology (LCQB), Institute of Biology Paris-Seine, Paris, France
| | - Shixin Ye
- Université Pierre-et-Marie-Curie, Laboratory of Computational and Quantitative Biology (LCQB), Institute of Biology Paris-Seine, Paris, France,Institut National de la Santé et de la Recherche Médicale, Paris, France,Centre National de la Recherche Scientifique, Paris, France,To whom all correspondence should be addressed: Shixin Ye-Lehmann, Laboratory of Computational and Quantitative Biology, Institute of Biology Paris-Seine, University of Pierre and Marie Curie, Bldg. C, 3rd floor, Room 311a, 4 Place Jussieu, 75006 Paris, France, Tel: 33.(0)1.44.27.60.57, .
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Expanding the genetic code of mammalian cells. Biochem Soc Trans 2017; 45:555-562. [PMID: 28408495 DOI: 10.1042/bst20160336] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 02/22/2017] [Accepted: 02/24/2017] [Indexed: 12/27/2022]
Abstract
In the last two decades, unnatural amino acid (UAA) mutagenesis has emerged as a powerful new method to probe and engineer protein structure and function. This technology enables precise incorporation of a rapidly expanding repertoire of UAAs into predefined sites of a target protein expressed in living cells. Owing to the small footprint of these genetically encoded UAAs and the large variety of enabling functionalities they offer, this technology has tremendous potential for deciphering the delicate and complex biology of the mammalian cells. Over the last few years, exciting progress has been made toward expanding the toolbox of genetically encoded UAAs in mammalian cells, improving the efficiency of their incorporation and developing innovative applications. Here, we provide our perspective on these recent developments and highlight the current challenges that must be overcome to realize the full potential of this technology.
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Tian H, Fürstenberg A, Huber T. Labeling and Single-Molecule Methods To Monitor G Protein-Coupled Receptor Dynamics. Chem Rev 2016; 117:186-245. [DOI: 10.1021/acs.chemrev.6b00084] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- He Tian
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Alexandre Fürstenberg
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Thomas Huber
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
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Naganathan S, Ray-Saha S, Park M, Tian H, Sakmar TP, Huber T. Multiplex detection of functional G protein-coupled receptors harboring site-specifically modified unnatural amino acids. Biochemistry 2015; 54:776-86. [PMID: 25524496 PMCID: PMC4310623 DOI: 10.1021/bi501267x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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We developed a strategy for identifying
positions in G protein-coupled
receptors that are amenable to bioorthogonal modification with a peptide
epitope tag under cell culturing conditions. We introduced the unnatural
amino acid p-azido-l-phenylalanine (azF)
into human CC chemokine receptor 5 (CCR5) at site-specific amber codon
mutations. We then used strain-promoted azide–alkyne [3+2]
cycloaddition to label the azF-CCR5 variants with a FLAG peptide epitope-conjugated
aza-dibenzocyclooctyne (DBCO) reagent. A microtiter plate-based sandwich
fluorophore-linked immunosorbent assay was used to probe simultaneously
the FLAG epitope and the receptor using infrared dye-conjugated antibodies
so that the extent of DBCO incorporation, corresponding nominally
to labeling efficiency, could be quantified ratiometrically. The extent
of incorporation of DBCO at the various sites was evaluated in the
context of a recent crystal structure of maraviroc-bound CCR5. We
observed that labeling efficiency varied dramatically depending on
the topological location of the azF in CCR5. Interestingly, position
109 in transmembrane helix 3, located in a hydrophobic cavity on the
extracellular side of the receptor, was labeled most efficiently.
Because the bioorthogonal labeling and detection strategy described
might be used to introduce a variety of different peptide epitopes
or fluorophores into engineered expressed receptors, it might prove
to be useful for a wide range of applications, including single-molecule
detection studies of receptor trafficking and signaling mechanism.
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Affiliation(s)
- Saranga Naganathan
- Laboratory of Chemical Biology & Signal Transduction, The Rockefeller University , New York, New York 10065, United States
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Park M, Tian H, Naganathan S, Sakmar TP, Huber T. Quantitative Multi-color Detection Strategies for Bioorthogonally Labeled GPCRs. Methods Mol Biol 2015; 1335:67-93. [PMID: 26260595 DOI: 10.1007/978-1-4939-2914-6_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We describe multiple bioorthogonal approaches to label G protein-coupled receptors (GPCRs) heterologously expressed in mammalian cells. The use of genetically encoded unnatural amino acids as bioorthogonal tags results in receptors that are expressed at lower levels than even their low abundance wild-type counterparts. Therefore, reproducible and sensitive quantification of the labeled GPCRs is extremely important and conventional methods are simply not sufficiently accurate and precise. Silver stains lack reproducibility, spectroscopic methods using fluorescent ligands are limited to quantifying only functional receptor molecules, and immunoassays using epitope tags derived from rhodopsin are particularly variable for low-abundance GPCRs. To avoid these shortcomings, we employ near infrared (NIR) imaging-based methods that enable simultaneous multi-color detection of two different antigens, thus facilitating the ratiometric analysis of bioorthogonally modified GPCRs. We anticipate that these multi-color detection strategies will provide new tools for quantitatively assessing stoichiometrically labeled GPCRs for studies of signalosomes and for structure-function relationships at a single molecule level.
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Affiliation(s)
- Minyoung Park
- Laboratory of Chemical Biology & Signal Transduction, The Rockefeller University, New York, NY, 10065, USA
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Ye Z, Williams GJ. Mapping a Ketosynthase:Acyl Carrier Protein Binding Interface via Unnatural Amino Acid-Mediated Photo-Cross-Linking. Biochemistry 2014; 53:7494-502. [DOI: 10.1021/bi500936u] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Zhixia Ye
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Gavin J. Williams
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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Huber T, Sakmar T. Chemical Biology Methods for Investigating G Protein-Coupled Receptor Signaling. ACTA ACUST UNITED AC 2014; 21:1224-37. [DOI: 10.1016/j.chembiol.2014.08.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/21/2014] [Accepted: 08/20/2014] [Indexed: 11/26/2022]
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Tian H, Naganathan S, Kazmi MA, Schwartz TW, Sakmar TP, Huber T. Bioorthogonal fluorescent labeling of functional G-protein-coupled receptors. Chembiochem 2014; 15:1820-9. [PMID: 25045132 DOI: 10.1002/cbic.201402193] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Indexed: 11/12/2022]
Abstract
Novel methods are required for site-specific, quantitative fluorescent labeling of G-protein-coupled receptors (GPCRs) and other difficult-to-express membrane proteins. Ideally, fluorescent probes should perturb the native structure and function as little as possible. We evaluated bioorthogonal reactions to label genetically encoded p-acetyl-L-phenylalanine (AcF) or p-azido-L-phenylalanine (azF) residues in receptors heterologously expressed in mammalian cells. We found that keto-selective reagents were not truly bioorthogonal, possibly owing to post-translational protein oxidation reactions. In contrast, the strain-promoted [3+2] azide-alkyne cycloaddition (SpAAC) with dibenzocyclooctyne (DIBO) reagents yielded stoichiometric conjugates with azF-rhodopsin while undergoing negligible background reactions. As one application of this technique, we used Alexa488-rhodopsin to measure the kinetics of ligand uptake and release in membrane-mimetic bicelles using a novel fluorescence-quenching assay.
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Affiliation(s)
- He Tian
- Laboratory of Chemical Biology and Signal Transduction, The Rockefeller University, 1230 York Avenue, New York, NY 10065 (USA)
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