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Li D, Kirberger M, Qiao J, Gui Z, Xue S, Pu F, Jiang J, Xu Y, Tan S, Salarian M, Ibhagui O, Hekmatyar K, Yang JJ. Protein MRI Contrast Agents as an Effective Approach for Precision Molecular Imaging. Invest Radiol 2024; 59:170-186. [PMID: 38180819 DOI: 10.1097/rli.0000000000001057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2024]
Abstract
ABSTRACT Cancer and other acute and chronic diseases are results of perturbations of common molecular determinants in key biological and signaling processes. Imaging is critical for characterizing dynamic changes in tumors and metastases, the tumor microenvironment, tumor-stroma interactions, and drug targets, at multiscale levels. Magnetic resonance imaging (MRI) has emerged to be a primary imaging modality for both clinical and preclinical applications due to its advantages over other modalities, including sensitivity to soft tissues, nondepth limitations, and the use of nonionizing radiation. However, extending the application of MRI to achieve both qualitative and quantitative precise molecular imaging with the capability to quantify molecular biomarkers for early detection, staging, and monitoring therapeutic treatment requires the capacity to overcome several major challenges including the trade-off between metal-binding affinity and relaxivity, which is an issue frequently associated with small chelator contrast agents. In this review, we will introduce the criteria of ideal contrast agents for precision molecular imaging and discuss the relaxivity of current contrast agents with defined first shell coordination water molecules. We will then report our advances in creating a new class of protein-targeted MRI contrast agents (ProCAs) with contributions to relaxivity largely derived from the secondary sphere and correlation time. We will summarize our rationale, design strategy, and approaches to the development and optimization of our pioneering ProCAs with desired high relaxivity, metal stability, and molecular biomarker-targeting capability, for precision MRI. From first generation (ProCA1) to third generation (ProCA32), we have achieved dual high r1 and r2 values that are 6- to 10-fold higher than clinically approved contrast agents at magnetic fields of 1.5 T, and their relaxivity values at high field are also significantly higher, which enables high resolution during small animal imaging. Further engineering of multiple targeting moieties enables ProCA32 agents that have strong biomarker-binding affinity and specificity for an array of key molecular biomarkers associated with various chronic diseases, while maintaining relaxation and exceptional metal-binding and selectivity, serum stability, and resistance to transmetallation, which are critical in mitigating risks associated with metal toxicity. Our leading product ProCA32.collagen has enabled the first early detection of liver metastasis from multiple cancers at early stages by mapping the tumor environment and early stage of fibrosis from liver and lung in vivo, with strong translational potential to extend to precision MRI for preclinical and clinical applications for precision diagnosis and treatment.
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Affiliation(s)
- Dongjun Li
- From the Center for Diagnostics and Therapeutics, Advanced Translational Imaging Facility, Department of Chemistry, Georgia State University, Atlanta, GA (D.L., M.K., J.Q., Z.G., S.X., P.F., J.J., S.T., M.S., O.I., K.H., J.J.Y.); and InLighta BioSciences, LLC, Marietta, GA (Y.X., J.J.Y)
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Tang S, Deng X, Jiang J, Kirberger M, Yang JJ. Design of Calcium-Binding Proteins to Sense Calcium. Molecules 2020; 25:molecules25092148. [PMID: 32375353 PMCID: PMC7248937 DOI: 10.3390/molecules25092148] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 04/27/2020] [Accepted: 04/28/2020] [Indexed: 01/25/2023] Open
Abstract
Calcium controls numerous biological processes by interacting with different classes of calcium binding proteins (CaBP’s), with different affinities, metal selectivities, kinetics, and calcium dependent conformational changes. Due to the diverse coordination chemistry of calcium, and complexity associated with protein folding and binding cooperativity, the rational design of CaBP’s was anticipated to present multiple challenges. In this paper we will first discuss applications of statistical analysis of calcium binding sites in proteins and subsequent development of algorithms to predict and identify calcium binding proteins. Next, we report efforts to identify key determinants for calcium binding affinity, cooperativity and calcium dependent conformational changes using grafting and protein design. Finally, we report recent advances in designing protein calcium sensors to capture calcium dynamics in various cellular environments.
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Affiliation(s)
- Shen Tang
- Department of Chemistry, Center for Diagnostics and Therapeutics and Advanced Translational Imaging Facility, Georgia State University, Atlanta, GA 30303, USA; (S.T.); (X.D.); (J.J.)
| | - Xiaonan Deng
- Department of Chemistry, Center for Diagnostics and Therapeutics and Advanced Translational Imaging Facility, Georgia State University, Atlanta, GA 30303, USA; (S.T.); (X.D.); (J.J.)
| | - Jie Jiang
- Department of Chemistry, Center for Diagnostics and Therapeutics and Advanced Translational Imaging Facility, Georgia State University, Atlanta, GA 30303, USA; (S.T.); (X.D.); (J.J.)
| | - Michael Kirberger
- School of Science and Technology, Georgia Gwinnett College, Lawrenceville, GA 30043, USA;
| | - Jenny J. Yang
- Department of Chemistry, Center for Diagnostics and Therapeutics and Advanced Translational Imaging Facility, Georgia State University, Atlanta, GA 30303, USA; (S.T.); (X.D.); (J.J.)
- Correspondence: ; Tel.: +1-404-413-5520
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Molecular Basis for Modulation of Metabotropic Glutamate Receptors and Their Drug Actions by Extracellular Ca 2. Int J Mol Sci 2017; 18:ijms18030672. [PMID: 28335551 PMCID: PMC5372683 DOI: 10.3390/ijms18030672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 03/13/2017] [Accepted: 03/17/2017] [Indexed: 12/24/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) associated with the slow phase of the glutamatergic signaling pathway in neurons of the central nervous system have gained importance as drug targets for chronic neurodegenerative diseases. While extracellular Ca2+ was reported to exhibit direct activation and modulation via an allosteric site, the identification of those binding sites was challenged by weak binding. Herein, we review the discovery of extracellular Ca2+ in regulation of mGluRs, summarize the recent developments in probing Ca2+ binding and its co-regulation of the receptor based on structural and biochemical analysis, and discuss the molecular basis for Ca2+ to regulate various classes of drug action as well as its importance as an allosteric modulator in mGluRs.
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Zhang C, Miller CL, Gorkhali R, Zou J, Huang K, Brown EM, Yang JJ. Molecular Basis of the Extracellular Ligands Mediated Signaling by the Calcium Sensing Receptor. Front Physiol 2016; 7:441. [PMID: 27746744 PMCID: PMC5043022 DOI: 10.3389/fphys.2016.00441] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 09/16/2016] [Indexed: 12/20/2022] Open
Abstract
Ca2+-sensing receptors (CaSRs) play a central role in regulating extracellular calcium concentration ([Ca2+]o) homeostasis and many (patho)physiological processes in multiple organs. This regulation is orchestrated by a cooperative response to extracellular stimuli such as small changes in Ca2+, Mg2+, amino acids, and other ligands. In addition, CaSR is a pleiotropic receptor regulating several intracellular signaling pathways, including calcium mobilization and intracellular calcium oscillation. Nearly 200 mutations and polymorphisms have been found in CaSR in relation to a variety of human disorders associated with abnormal Ca2+ homeostasis. In this review, we summarize efforts directed at identifying binding sites for calcium and amino acids. Both homotropic cooperativity among multiple calcium binding sites and heterotropic cooperativity between calcium and amino acid were revealed using computational modeling, predictions, and site-directed mutagenesis coupled with functional assays. The hinge region of the bilobed Venus flytrap (VFT) domain of CaSR plays a pivotal role in coordinating multiple extracellular stimuli, leading to cooperative responses from the receptor. We further highlight the extensive number of disease-associated mutations that have also been shown to affect CaSR's cooperative action via several types of mechanisms. These results provide insights into the molecular bases of the structure and functional cooperativity of this receptor and other members of family C of the G protein-coupled receptors (cGPCRs) in health and disease states, and may assist in the prospective development of novel receptor-based therapeutics.
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Affiliation(s)
- Chen Zhang
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | | | - Rakshya Gorkhali
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | - Juan Zou
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | - Kenneth Huang
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | - Edward M Brown
- Center for Diagnostics and Therapeutics, Georgia State UniversityAtlanta, GA, USA; Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's HospitalBoston, MA, USA
| | - Jenny J Yang
- Department of Chemistry, Georgia State University Atlanta, GA, USA
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Xue S, Qiao J, Jiang J, Hubbard K, White N, Wei L, Li S, Liu ZR, Yang JJ. Design of ProCAs (protein-based Gd(3+) MRI contrast agents) with high dose efficiency and capability for molecular imaging of cancer biomarkers. Med Res Rev 2014; 34:1070-99. [PMID: 24615853 DOI: 10.1002/med.21313] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Magnetic resonance imaging (MRI) is the leading imaging technique for disease diagnostics, providing high resolution, three-dimensional images noninvasively. MRI contrast agents are designed to improve the contrast and sensitivity of MRI. However, current clinically used MRI contrast agents have relaxivities far below the theoretical upper limit, which largely prevent advancing molecular imaging of biomarkers with desired sensitivity and specificity. This review describes current progress in the development of a new class of protein-based MRI contrast agents (ProCAs) with high relaxivity using protein design to optimize the parameters that govern relaxivity. Further, engineering with targeting moiety allows these contrast agents to be applicable for molecular imaging of prostate cancer biomarkers by MRI. The developed protein-based contrast agents also exhibit additional in vitro and in vivo advantages for molecular imaging of disease biomarkers, such as high metal-binding stability and selectivity, reduced toxicity, proper blood circulation time, and higher permeability in tumor tissue in addition to improved relaxivities.
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Affiliation(s)
- Shenghui Xue
- Departments of Chemistry and Biology, Georgia State University, Atlanta, Georgia; Center for Diagnostics & Therapeutics (CDT), Georgia State University, Atlanta, Georgia; Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia
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Molecular imaging of EGFR/HER2 cancer biomarkers by protein MRI contrast agents. J Biol Inorg Chem 2013; 19:259-70. [PMID: 24366655 DOI: 10.1007/s00775-013-1076-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 12/06/2013] [Indexed: 12/22/2022]
Abstract
Epidermal growth factor receptor (EGFR) and HER2 are major prognosis biomarkers and drug targets overexpressed in various types of cancer cells. There is a pressing need to develop MRI contrast agents capable of enhancing the contrast between normal tissues and tumors with high relaxivity, capable of targeting tumors, and with high intratumoral distribution and minimal toxicity. In this review, we first discuss EGFR signaling and its role in tumor progression as a major drug target. We then report our progress in the development of protein contrast agents with significant improvement of both r1 and r2 relaxivities, pharmacokinetics, in vivo retention time, and in vivo dose efficiency. Finally, we report our effort in the development of EGFR-targeted protein contrast agents with the capability to cross the endothelial boundary and with good tissue distribution across the entire tumor mass. The noninvasive capability of MRI to visualize spatially and temporally the intratumoral distribution as well as quantify the levels of EGFR and HER2 would greatly improve our ability to track changes of the biomarkers during tumor progression, monitor treatment efficacy, aid in patient selection, and further develop novel targeted therapies for clinical application.
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Xue S, Qiao J, Pu F, Cameron M, Yang JJ. Design of a novel class of protein-based magnetic resonance imaging contrast agents for the molecular imaging of cancer biomarkers. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2013; 5:163-79. [PMID: 23335551 DOI: 10.1002/wnan.1205] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Magnetic resonance imaging (MRI) of disease biomarkers, especially cancer biomarkers, could potentially improve our understanding of the disease and drug activity during preclinical and clinical drug treatment and patient stratification. MRI contrast agents with high relaxivity and targeting capability to tumor biomarkers are highly required. Extensive work has been done to develop MRI contrast agents. However, only a few limited literatures report that protein residues can function as ligands to bind Gd(3+) with high binding affinity, selectivity, and relaxivity. In this paper, we focus on reporting our current progress on designing a novel class of protein-based Gd(3+) MRI contrast agents (ProCAs) equipped with several desirable capabilities for in vivo application of MRI of tumor biomarkers. We will first discuss our strategy for improving the relaxivity by a novel protein-based design. We then discuss the effect of increased relaxivity of ProCAs on improving the detection limits for MRI contrast agent, especially for in vivo application. We will further report our efforts to improve in vivo imaging capability and our achievement in molecular imaging of cancer biomarkers with potential preclinical and clinical applications.
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Affiliation(s)
- Shenghui Xue
- Departments of Chemistry and Biology, Center for Diagnostics & Therapeutics, Georgia State University, Atlanta, GA, USA
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Wei L, Li S, Yang J, Ye Y, Zou J, Wang L, Long R, Zurkiya O, Zhao T, Johnson J, Qiao J, Zhou W, Castiblanco A, Maor N, Chen Y, Mao H, Hu X, Yang JJ, Liu ZR. Protein-based MRI contrast agents for molecular imaging of prostate cancer. Mol Imaging Biol 2011; 13:416-423. [PMID: 20574851 DOI: 10.1007/s11307-010-0342-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE The purpose of this study was to demonstrate a novel protein-based magnetic resonance imaging (MRI) contrast agent that has the capability of targeting prostate cancer and which provides high-sensitivity MR imaging in tumor cells and mouse models. PROCEDURE A fragment of gastrin-releasing peptide (GRP) was fused into a protein-based MRI contrast agent (ProCA1) at different regions. MR imaging was obtained in both tumor cells (PC3 and H441) and a tumor mouse model administrated with ProCA1.GRP. RESULTS PC3 and DU145 cells treated with ProCA1.GRPs exhibited enhanced signal in MRI. Intratumoral injection of ProCA1.GRP in a PC3 tumor model displayed enhanced MRI signal. The contrast agent was retained in the PC3 tumor up to 48 h post-injection. CONCLUSIONS Protein-based MRI contrast agent with tumor targeting modality can specifically target GRPR-positive prostate cancer. Intratumoral injection of the ProCA1 agent in the prostate cancer mouse model verified the targeting capability of ProCA1.GRP and showed a prolonged retention time in tumors.
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Affiliation(s)
- Lixia Wei
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Shunyi Li
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Jianhua Yang
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Yiming Ye
- Biotechnology Core Facility Branch, Center for Disease Control and Prevention, Atlanta, GA, 30333, USA
| | - Jin Zou
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Liya Wang
- Department of Radiology, Emory University, Atlanta, GA, 30322, USA
| | - Robert Long
- Department of Radiology, Emory University, Atlanta, GA, 30322, USA
| | - Omar Zurkiya
- Department of Biomedical Engineering, Emory University, Atlanta, GA, 30322, USA
| | - Tiejun Zhao
- Department of Biomedical Engineering, Emory University, Atlanta, GA, 30322, USA
| | - Julian Johnson
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Jingjuan Qiao
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Wangda Zhou
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Adriana Castiblanco
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Natalie Maor
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Yanyi Chen
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
| | - Hui Mao
- Department of Radiology, Emory University, Atlanta, GA, 30322, USA
| | - Xiaoping Hu
- Department of Biomedical Engineering, Emory University, Atlanta, GA, 30322, USA
| | - Jenny J Yang
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA.
| | - Zhi-Ren Liu
- Department of Chemistry and Biology, Georgia State University, Atlanta, GA, 30302, USA
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Yang CM, Zhang J. Insights into intramolecular Trp and His side-chain orientation and stereospecific π interactions surrounding metal centers: an investigation using protein metal-site mimicry in solution. Chemistry 2011; 16:10854-65. [PMID: 20669189 DOI: 10.1002/chem.200903149] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Metal-binding scaffolds incorporating a Trp/His-paired epitope are instrumental in giving novel insights into the physicochemical basis of functional and mechanistic versatility conferred by the Trp-His interplay at a metal site. Herein, by coupling biometal site mimicry and (1)H and (13)C NMR spectroscopy experiments, modular constructs EDTA-(L-Trp, L-His) (EWH; EDTA=ethylenediamino tetraacetic acid) and DTPA-(L-Trp, L-His) (DWH; DTPA=diethylenetriamino pentaacetic acid) were employed to dissect the static and transient physicochemical properties of hydrophobic/hydrophilic aromatic interactive modes surrounding biometal centers. The binding feature and identities of the stoichiometric metal-bound complexes in solution were investigated by using (1)H and (13)C NMR spectroscopy, which facilitated a cross-validation of the carboxylate, amide oxygen, and tertiary amino groups as the primary ligands and indole as the secondary ligand, with the imidazole (Im) N3 nitrogen being weakly bound to metals such as Ca(2+) owing to a multivalency effect. Surrounding the metal centers, the stereospecific orientation of aromatic rings in the diastereoisomerism is interpreted with the Ca(2+)-EWH complex. With respect to perturbed Trp side-chain rotamer heterogeneity, drastically restricted Trp side-chain flexibility and thus a dynamically constrained rotamer interconversion due to π interactions is evident from the site-selective (13)C NMR spectroscopic signal broadening of the Trp indolyl C3 atom. Furthermore, effects of Trp side-chain fluctuation on indole/Im orientation were the subject of a 2D NMR spectroscopy study by using the Ca(2+)-bound state; a C-H2(indolyl)/C-H5(Im(+)) connectivity observed in the NOESY spectra captured direct evidence that the N-H1 of the Ca(2+)-Im(+) unit interacted with the pyrrole ring of the indole unit in Ca(2+)-bound EWH but not in DWH, which is assignable to a moderately static, anomalous, T-shaped, interplanar π(+)-π stacking alignment. Nevertheless, a comparative (13)C NMR spectroscopy study of the two homologous scaffolds revealed that the overall response of the indole unit arises predominantly from global attractions between the indole ring and the entire positively charged first coordination sphere. The study thus demonstrates the coordination-sphere/geometry dependence of the Trp/His side-chain interplay, and established that π interactions allow (13)C NMR spectroscopy to offer a new window for investigating Trp rotamer heterogeneity near metal-binding centers.
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Affiliation(s)
- Chi Ming Yang
- Neurochemistry & Biophysical Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China.
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Yanyi C, Shenghui X, Yubin Z, Jie YJ. Calciomics: prediction and analysis of EF-hand calcium binding proteins by protein engineering. Sci China Chem 2010; 53:52-60. [PMID: 20802784 PMCID: PMC2926812 DOI: 10.1007/s11426-010-0011-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ca2+ plays a pivotal role in the physiology and biochemistry of prokaryotic and mammalian organisms. Viruses also utilize the universal Ca2+ signal to create a specific cellular environment to achieve coexistence with the host, and to propagate. In this paper we first describe our development of a grafting approach to understand site-specific Ca2+ binding properties of EF-hand proteins with a helix-loop-helix Ca2+ binding motif, then summarize our prediction and identification of EF-hand Ca2+ binding sites on a genome-wide scale in bacteria and virus, and next report the application of the grafting approach to probe the metal binding capability of predicted EF-hand motifs within the streptococcal hemoprotein receptor (Shr) of Streptococcus pyrogenes and the nonstructural protein 1 (nsP1) of Sindbis virus. When methods such as the grafting approach are developed in conjunction with prediction algorithms we are better able to probe continuous Ca2+-binding sites that have been previously underrepresented due to the limitation of conventional methodology.
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Affiliation(s)
- Chen Yanyi
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
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Holder AN, Ellis AL, Zou J, Chen N, Yang JJ. Facilitating chromophore formation of engineered Ca(2+) binding green fluorescent proteins. Arch Biochem Biophys 2009; 486:27-34. [PMID: 19358822 PMCID: PMC2774846 DOI: 10.1016/j.abb.2009.03.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 03/26/2009] [Accepted: 03/28/2009] [Indexed: 01/24/2023]
Abstract
Green fluorescent protein (GFP) containing a self-coded chromophore has been applied in protein trafficking and folding, gene expression, and as sensors in living cells. While the "cycle3" mutation denoted as C3 mutation (F99S/M153T/V163A) offers the ability to increase GFP fluorescence at 37 degrees C, it is not clear whether such mutations will also be able to assist the folding and formation of the chromophore upon the addition of metal ion binding sites. Here, we investigate in both bacterial and mammalian systems, the effect of C2 (M153T/V163A) and C3 (F99S/M153T/V163A) mutations on the folding of enhanced GFP (EGFP, includes F64L/S65T) and its variants engineered with two types of Ca(2+) binding sites: (1) a designed discontinuous Ca(2+) binding site and (2) a grafted continuous Ca(2+) binding motif. We show that, for the constructed EGFP variants, the C2 mutation is sufficient to facilitate the production of fluorescence in both bacterial and mammalian cells. Further addition of the mutation F99S decreases the folding efficiency of these variants although a similar effect is not detectable for EGFP, likely due to the already greatly enhanced mutation F64L/S65T from the original GFP, which hastens the chromophore formation. The extinction coefficient and quantum yield of purified proteins of each construct were also examined to compare the effects of both C2 and C3 mutations on protein spectroscopic properties. Our quantitative analyses of the effect of C2 and C3 mutations on the folding and formation of GFP chromophore that undergoes different folding trajectories in bacterial versus mammalian cells provide insights into the development of fluorescent protein-based analytical sensors.
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Affiliation(s)
- Angela N. Holder
- Department of Chemistry and Center for Drug Design and Advanced Biotechnology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302, USA
| | - April L. Ellis
- Department of Chemistry and Center for Drug Design and Advanced Biotechnology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302, USA
| | - Jin Zou
- Department of Chemistry and Center for Drug Design and Advanced Biotechnology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302, USA
| | - Ning Chen
- Department of Chemistry and Center for Drug Design and Advanced Biotechnology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302, USA
| | - Jenny J. Yang
- Department of Chemistry and Center for Drug Design and Advanced Biotechnology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302, USA
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Li S, Yang W, Maniccia AW, Barrow D, Tjong H, Zhou HX, Yang JJ. Rational design of a conformation-switchable Ca2+- and Tb3+-binding protein without the use of multiple coupled metal-binding sites. FEBS J 2008; 275:5048-61. [PMID: 18785925 DOI: 10.1111/j.1742-4658.2008.06638.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Ca2+, as a messenger of signal transduction, regulates numerous target molecules via Ca2+-induced conformational changes. Investigation into the determinants for Ca2+-induced conformational change is often impeded by cooperativity between multiple metal-binding sites or protein oligomerization in naturally occurring proteins. To dissect the relative contributions of key determinants for Ca2+-dependent conformational changes, we report the design of a single-site Ca2+-binding protein (CD2.trigger) created by altering charged residues at an electrostatically sensitive location on the surface of the host protein rat Cluster of Differentiation 2 (CD2).CD2.trigger binds to Tb3+ and Ca2+ with dissociation constants of 0.3 +/- 0.1 and 90 +/- 25 microM, respectively. This protein is largely unfolded in the absence of metal ions at physiological pH, but Tb3+ or Ca2+ binding results in folding of the native-like conformation. Neutralization of the charged coordination residues, either by mutation or protonation, similarly induces folding of the protein. The control of a major conformational change by a single Ca2+ ion, achieved on a protein designed without reliance on sequence similarity to known Ca2+-dependent proteins and coupled metal-binding sites, represents an important step in the design of trigger proteins.
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Affiliation(s)
- Shunyi Li
- Department of Chemistry, Center of Drug Design and Biotechnology, Georgia State University, Atlanta, GA, USA
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Yang JJ, Yang J, Wei L, Zurkiya O, Yang W, Li S, Zou J, Zhou Y, Maniccia ALW, Mao H, Zhao F, Malchow R, Zhao S, Johnson J, Hu X, Krogstad E, Liu ZR. Rational design of protein-based MRI contrast agents. J Am Chem Soc 2008; 130:9260-7. [PMID: 18576649 DOI: 10.1021/ja800736h] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the rational design of a novel class of magnetic resonance imaging (MRI) contrast agents with engineered proteins (CAi.CD2, i = 1, 2,..., 9) chelated with gadolinium. The design of protein-based contrast agents involves creating high-coordination Gd(3+) binding sites in a stable host protein using amino acid residues and water molecules as metal coordinating ligands. Designed proteins show strong selectivity for Gd(3+) over physiological metal ions such as Ca(2+), Zn(2+), and Mg(2+). These agents exhibit a 20-fold increase in longitudinal and transverse relaxation rate values over the conventional small-molecule contrast agents, e.g., Gd-DTPA (diethylene triamine pentaacetic acid), used clinically. Furthermore, they exhibit much stronger contrast enhancement and much longer blood retention time than Gd-DTPA in mice. With good biocompatibility and potential functionalities, these protein contrast agents may be used as molecular imaging probes to target disease markers, thereby extending applications of MRI.
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Affiliation(s)
- Jenny J Yang
- Department of Chemistry, Center for Drug Design and Advanced Biotechnology, Georgia State University, Atlanta, Georgia 30303, USA.
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14
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Jones LM, Yang W, Maniccia AW, Harrison A, van der Merwe PA, Yang JJ. Rational design of a novel calcium-binding site adjacent to the ligand-binding site on CD2 increases its CD48 affinity. Protein Sci 2008; 17:439-49. [PMID: 18287277 PMCID: PMC2248323 DOI: 10.1110/ps.073328208] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 12/04/2007] [Accepted: 12/07/2007] [Indexed: 10/22/2022]
Abstract
Electrostatic interactions are important for molecular recognition processes including Ca2+-binding and cell adhesion. To understand these processes, we have successfully introduced a novel Ca2+-binding site into the non-Ca2+-dependent cell adhesion protein CD2 using our criteria that are specifically tailored to the structural and functional properties of the protein environment and charged adhesion surface. This designed site with ligand residues exclusively from the beta-sheets selectively binds to Ca2+ and Ln3+ over other mono- and divalent cations. While Ca2+ and Ln3+ binding specifically alters the local environment of the designed Ca2+-binding site, the designed protein undergoes a significantly smaller conformation change compared with those observed in naturally occurring Ca2+-binding sites that are composed of at least part of the flexible loop and helical regions. In addition, the CD2-CD48-binding affinity increased approximately threefold after protein engineering, suggesting that the cell adhesion of CD2 can be modulated by altering the local electrostatic environment. The study provides site-specific information for regulating cell adhesion within CD2 and gives insight into the structural factors required for Ca2+-modulated biological processes.
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Affiliation(s)
- Lisa M Jones
- Department of Chemistry, Center for Drug Design and Biotechnology, Georgia State University, Atlanta, Georgia 30303, USA
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Huang Y, Zhou Y, Yang W, Butters R, Lee HW, Li S, Castiblanco A, Brown EM, Yang JJ. Identification and dissection of Ca(2+)-binding sites in the extracellular domain of Ca(2+)-sensing receptor. J Biol Chem 2007; 282:19000-10. [PMID: 17478419 PMCID: PMC2867057 DOI: 10.1074/jbc.m701096200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Ca(2+)-sensing receptors (CaSRs) represent a class of receptors that respond to changes in the extracellular Ca(2+) concentration ([Ca(2+)](o)) and activate multiple signaling pathways. A major barrier to advancing our understanding of the role of Ca(2+) in regulating CaSRs is the lack of adequate information about their Ca(2+)-binding locations, which is largely hindered by the lack of a solved three-dimensional structure and rapid off rates due to low Ca(2+)-binding affinities. In this paper, we have reported the identification of three potential Ca(2+)-binding sites in a modeled CaSR structure using computational algorithms based on the geometric description and surface electrostatic potentials. Mutation of the predicted ligand residues in the full-length CaSR caused abnormal responses to [Ca(2+)](o), similar to those observed with naturally occurring activating or inactivating mutations of the CaR, supporting the essential role of these predicted Ca(2+)-binding sites in the sensing capability of the CaSR. In addition, to probe the intrinsic Ca(2+)-binding properties of the predicted sequences, we engineered two predicted continuous Ca(2+)-binding sequences individually into a scaffold protein provided by a non-Ca(2+)-binding protein, CD2. We report herein the estimation of the metal-binding affinities of these predicted sites in the CaSR by monitoring aromatic-sensitized Tb(3+) fluorescence energy transfer. Removing the predicted Ca(2+)-binding ligands resulted in the loss of or significantly weakened cation binding. The potential Ca(2+)-binding residues were shown to be involved in Ca(2+)/Ln(3+) binding by high resolution NMR and site-directed mutagenesis, further validating our prediction of Ca(2+)-binding sites within the extracellular domain of the CaSR.
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MESH Headings
- Algorithms
- Animals
- Binding Sites/physiology
- Calcium/metabolism
- Cell Line
- Extracellular Space/metabolism
- Humans
- Kidney/cytology
- Mice
- Models, Chemical
- Mutagenesis, Site-Directed
- Nuclear Magnetic Resonance, Biomolecular
- Protein Engineering
- Protein Structure, Quaternary
- Protein Structure, Tertiary
- Receptors, Calcium-Sensing/chemistry
- Receptors, Calcium-Sensing/genetics
- Receptors, Calcium-Sensing/metabolism
- Receptors, Metabotropic Glutamate/chemistry
- Receptors, Metabotropic Glutamate/metabolism
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Affiliation(s)
- Yun Huang
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Yubin Zhou
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Wei Yang
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Robert Butters
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Hsiau-Wei Lee
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Shunyi Li
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Adriana Castiblanco
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Edward M. Brown
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Jenny J. Yang
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
- To whom correspondence should be addressed: Dept. of Chemistry, Georgia State University, University Plaza, Atlanta, GA 30303. Tel.: 404-651-4620; Fax: 404-651-2751;
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