1
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El-Assaad AM, Hamieh T. SARS-CoV-2: Prediction of critical ionic amino acid mutations. Comput Biol Med 2024; 178:108688. [PMID: 38870723 DOI: 10.1016/j.compbiomed.2024.108688] [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: 10/31/2023] [Revised: 05/26/2024] [Accepted: 06/01/2024] [Indexed: 06/15/2024]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that caused coronavirus disease 2019 (COVID-19), has been studied thoroughly, and several variants are revealed across the world with their corresponding mutations. Studies and vaccines development focus on the genetic mutations of the S protein due to its vital role in allowing the virus attach and fuse with the membrane of a host cell. In this perspective, we study the effects of all ionic amino acid mutations of the SARS-CoV-2 viral spike protein S1 when bound to Antibody CC12.1 within the SARS-CoV-2:CC12.1 complex model. Binding free energy calculations between SARS-CoV-2 and antibody CC12.1 are based on the Analysis of Electrostatic Similarities of Proteins (AESOP) framework, where the electrostatic potentials are calculated using Adaptive Poisson-Boltzmann Solver (APBS). The atomic radii and charges that feed into the APBS calculations are calculated using the PDB2PQR software. Our results are the first to propose in silico potential life-threatening mutations of SARS-CoV-2 beyond the present mutations found in the five common variants worldwide. We find each of the following mutations: K378A, R408A, K424A, R454A, R457A, K458A, and K462A, to play significant roles in the binding to Antibody CC12.1, since they are turned into strong inhibitors on both chains of the S1 protein, whereas the mutations D405A, D420A, and D427A, show to play important roles in this binding, as they are turned into mild inhibitors on both chains of the S1 protein.
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Affiliation(s)
- Atlal M El-Assaad
- Department of Electrical Engineering & Computer Science, University of Toledo (UT), Toledo OH 43606, USA; Department of Computer Science, Lebanese International University (LIU), Bekaa, Lebanon.
| | - Tayssir Hamieh
- Faculty of Science and Engineering, Maastricht University, P.O. Box 616, 6200 MD Maastricht, the Netherlands; Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences, Lebanese University, Hadath, Lebanon.
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2
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Mutational signatures in GATA3 transcription factor and its DNA binding domain that stimulate breast cancer and HDR syndrome. Sci Rep 2021; 11:22762. [PMID: 34815386 PMCID: PMC8611019 DOI: 10.1038/s41598-021-01832-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 10/14/2021] [Indexed: 11/08/2022] Open
Abstract
Transcription factors (TFs) play important roles in many biochemical processes. Many human genetic disorders have been associated with mutations in the genes encoding these transcription factors, and so those mutations became targets for medications and drug design. In parallel, since many transcription factors act either as tumor suppressors or oncogenes, their mutations are mostly associated with cancer. In this perspective, we studied the GATA3 transcription factor when bound to DNA in a crystal structure and assessed the effect of different mutations encountered in patients with different diseases and phenotypes. We generated all missense mutants of GATA3 protein and DNA within the adjacent and the opposite GATA3:DNA complex models. We mutated every amino acid and studied the new binding of the complex after each mutation. Similarly, we did for every DNA base. We applied Poisson-Boltzmann electrostatic calculations feeding into free energy calculations. After analyzing our data, we identified amino acids and DNA bases keys for binding. Furthermore, we validated those findings against experimental genetic data. Our results are the first to propose in silico modeling for GATA:DNA bound complexes that could be used to score effects of missense mutations in other classes of transcription factors involved in common and genetic diseases.
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3
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Narkhede YB, Gautam AK, Hsu RV, Rodriguez W, Zewde NT, Harrison RES, Arantes PR, Gaieb Z, Gorham RD, Kieslich C, Morikis D, Sahu A, Palermo G. Role of Electrostatic Hotspots in the Selectivity of Complement Control Proteins Toward Human and Bovine Complement Inhibition. Front Mol Biosci 2021; 8:618068. [PMID: 33829039 PMCID: PMC8020814 DOI: 10.3389/fmolb.2021.618068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/08/2021] [Indexed: 11/13/2022] Open
Abstract
Poxviruses are dangerous pathogens, which can cause fatal infection in unvaccinated individuals. The causative agent of smallpox in humans, variola virus, is closely related to the bovine vaccinia virus, yet the molecular basis of their selectivity is currently incompletely understood. Here, we examine the role of the electrostatics in the selectivity of the smallpox protein SPICE and vaccinia protein VCP toward the human and bovine complement protein C3b, a key component of the complement immune response. Electrostatic calculations, in-silico alanine-scan and electrostatic hotspot analysis, as introduced by Kieslich and Morikis (PLoS Comput. Biol. 2012), are used to assess the electrostatic complementarity and to identify sites resistant to local perturbation where the electrostatic potential is likely to be evolutionary conserved. The calculations suggest that the bovine C3b is electrostatically prone to selectively bind its VCP ligand. On the other hand, the human isoform of C3b exhibits a lower electrostatic complementarity toward its SPICE ligand. Yet, the human C3b displays a highly preserved electrostatic core, which suggests that this isoform could be less selective in binding different ligands like SPICE and the human Factor H. This is supported by experimental cofactor activity assays revealing that the human C3b is prone to bind both SPICE and Factor H, which exhibit diverse electrostatic properties. Additional investigations considering mutants of SPICE and VCP that revert their selectivity reveal an “electrostatic switch” into the central modules of the ligands, supporting the critical role of the electrostatics in the selectivity. Taken together, these evidences provide insights into the selectivity mechanism of the complement regulator proteins encoded by the variola and vaccinia viruses to circumvent the complement immunity and exert their pathogenic action. These fundamental aspects are valuable for the development of novel vaccines and therapeutic strategies.
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Affiliation(s)
- Yogesh B Narkhede
- Department of Bioengineering, University of California, Riverside, CA
| | - Avneesh K Gautam
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, India
| | - Rohaine V Hsu
- Department of Bioengineering, University of California, Riverside, CA
| | - Wilson Rodriguez
- Department of Bioengineering, University of California, Riverside, CA
| | - Nehemiah T Zewde
- Department of Bioengineering, University of California, Riverside, CA
| | - Reed E S Harrison
- Department of Bioengineering, University of California, Riverside, CA
| | - Pablo R Arantes
- Department of Bioengineering, University of California, Riverside, CA
| | - Zied Gaieb
- Department of Bioengineering, University of California, Riverside, CA
| | - Ronald D Gorham
- Department of Bioengineering, University of California, Riverside, CA
| | - Chris Kieslich
- Department of Bioengineering, University of California, Riverside, CA.,Department of Chemical Engineering, Auburn University, Auburn, AL
| | - Dimitrios Morikis
- Department of Bioengineering, University of California, Riverside, CA
| | - Arvind Sahu
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, India
| | - Giulia Palermo
- Department of Bioengineering, University of California, Riverside, CA.,Department of Chemistry, University of California, Riverside, CA
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4
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Agrawal P, Sharma S, Pal P, Ojha H, Mullick J, Sahu A. The imitation game: a viral strategy to subvert the complement system. FEBS Lett 2020; 594:2518-2542. [DOI: 10.1002/1873-3468.13856] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/10/2020] [Accepted: 05/23/2020] [Indexed: 11/09/2022]
Affiliation(s)
- Palak Agrawal
- Complement Biology Laboratory National Centre for Cell Science S. P. Pune University Campus Ganeshkhind Pune 411007 India
| | - Samriddhi Sharma
- Complement Biology Laboratory National Centre for Cell Science S. P. Pune University Campus Ganeshkhind Pune 411007 India
| | - Pradipta Pal
- Complement Biology Laboratory National Centre for Cell Science S. P. Pune University Campus Ganeshkhind Pune 411007 India
| | - Hina Ojha
- Complement Biology Laboratory National Centre for Cell Science S. P. Pune University Campus Ganeshkhind Pune 411007 India
| | - Jayati Mullick
- Microbial Containment Complex ICMR‐National Institute of Virology Pune 411021 India
| | - Arvind Sahu
- Complement Biology Laboratory National Centre for Cell Science S. P. Pune University Campus Ganeshkhind Pune 411007 India
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5
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Zhang Y, Guo J, Ning L, Tian J, Yao X, Liu H. The molecular mechanism of pH-regulating C3d-CR2 interactions: Insights from molecular dynamics simulation. Chem Biol Drug Des 2018; 93:628-637. [PMID: 30566277 DOI: 10.1111/cbdd.13460] [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: 09/17/2018] [Revised: 11/09/2018] [Accepted: 12/07/2018] [Indexed: 11/27/2022]
Abstract
The interactions of complement receptor 2 (CR2) and the degradation fragment C3d of complement component C3 mediate the innate and adaptive immune systems. Due to the importance of C3d-CR2 interaction in the design of vaccines, many studies have indicated the interactions are pH-dependent. Moreover, C3d-CR2 interactions at pH 5.0 are unknown. To investigate the molecular mechanism of pH-regulating C3d-CR2 interaction, molecular dynamics simulations for C3d-CR2 complex in different pH are performed. Our results revealed that the protonation of His9 in C3d at pH 6.0 slightly weakens C3d-CR2 association as reducing pH from 7.4 to 6.0, initiated from a key hydrogen bond formed between Gly270 and His9 in C3d at pH 6.0. When reducing pH from 6.0 to 5.0, the protonation of His33 in C3d weakens C3d-SCR1 association by changing the hydrogen-bond network of Asp36, Glu37, and Glu39 in C3d with Arg13 in CR2. In addition, the protonation of His90 significantly enhances C3d-SCR2 association. This is because the enhanced hydrogen-bond interactions of His90 with Glu63 and Ser69 of the linker change the conformations of the linker, Cys112-Asn116 and Pro87-Gly91 regions. This study uncovers the molecular mechanism of the mediation of pH on C3d-CR2 interaction, which is valuable for vaccine design.
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Affiliation(s)
- Yan Zhang
- School of Pharmacy, Lanzhou University, Lanzhou, China.,Guiyang College of Traditional Chinese Medicine, Guiyang, China.,State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou, China
| | - Jingjing Guo
- Henan Engineering Research Center of Chiral Hydroxyl Pharmaceutical, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan, China
| | - Lulu Ning
- State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou, China
| | - Jiaqi Tian
- School of Pharmacy, Lanzhou University, Lanzhou, China
| | - Xiaojun Yao
- State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou, China
| | - Huanxiang Liu
- School of Pharmacy, Lanzhou University, Lanzhou, China.,State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou, China
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6
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Zhang Y, Guo J, Li L, Liu X, Yao X, Liu H. The solvent at antigen-binding site regulated C3d–CR2 interactions through the C-terminal tail of C3d at different ion strengths: insights from molecular dynamics simulation. Biochim Biophys Acta Gen Subj 2016; 1860:2220-31. [DOI: 10.1016/j.bbagen.2016.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 03/16/2016] [Accepted: 05/02/2016] [Indexed: 12/11/2022]
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7
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El-Assaad A, Dawy Z, Nemer G. Electrostatic study of Alanine mutational effects on transcription: application to GATA-3:DNA interaction complex. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:4005-8. [PMID: 26737172 DOI: 10.1109/embc.2015.7319272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Protein-DNA interaction is of fundamental importance in molecular biology, playing roles in functions as diverse as DNA transcription, DNA structure formation, and DNA repair. Protein-DNA association is also important in medicine; understanding Protein-DNA binding kinetics can assist in identifying disease root causes which can contribute to drug development. In this perspective, this work focuses on the transcription process by the GATA Transcription Factor (TF). GATA TF binds to DNA promoter region represented by `G,A,T,A' nucleotides sequence, and initiates transcription of target genes. When proper regulation fails due to some mutations on the GATA TF protein sequence or on the DNA promoter sequence (weak promoter), deregulation of the target genes might lead to various disorders. In this study, we aim to understand the electrostatic mechanism behind GATA TF and DNA promoter interactions, in order to predict Protein-DNA binding in the presence of mutations, while elaborating on non-covalent binding kinetics. To generate a family of mutants for the GATA:DNA complex, we replaced every charged amino acid, one at a time, with a neutral amino acid like Alanine (Ala). We then applied Poisson-Boltzmann electrostatic calculations feeding into free energy calculations, for each mutation. These calculations delineate the contribution to binding from each Ala-replaced amino acid in the GATA:DNA interaction. After analyzing the obtained data in view of a two-step model, we are able to identify potential key amino acids in binding. Finally, we applied the model to GATA-3:DNA (crystal structure with PDB-ID: 3DFV) binding complex and validated it against experimental results from the literature.
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8
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Abstract
![]()
Electrostatic effects
are ubiquitous in protein interactions and
are found to be pervasive in the complement system as well. The interaction
between complement fragment C3d and complement receptor 2 (CR2) has
evolved to become a link between innate and adaptive immunity. Electrostatic
interactions have been suggested to be the driving factor for the
association of the C3d:CR2 complex. In this study, we investigate
the effects of ionic strength and mutagenesis on the association of
C3d:CR2 through Brownian dynamics simulations. We demonstrate that
the formation of the C3d:CR2 complex is ionic strength-dependent,
suggesting the presence of long-range electrostatic steering that
accelerates the complex formation. Electrostatic steering occurs through
the interaction of an acidic surface patch in C3d and the positively
charged CR2 and is supported by the effects of mutations within the
acidic patch of C3d that slow or diminish association. Our data are
in agreement with previous experimental mutagenesis and binding studies
and computational studies. Although the C3d acidic patch may be locally
destabilizing because of unfavorable Coulombic interactions of like
charges, it contributes to the acceleration of association. Therefore,
acceleration of function through electrostatic steering takes precedence
to stability. The site of interaction between C3d and CR2 has been
the target for delivery of CR2-bound nanoparticle, antibody, and small
molecule biomarkers, as well as potential therapeutics. A detailed
knowledge of the physicochemical basis of C3d:CR2 association may
be necessary to accelerate biomarker and drug discovery efforts.
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Affiliation(s)
- Rohith R Mohan
- Department of Bioengineering, University of California , Riverside, California 92521, United States
| | - Gary A Huber
- Department of Chemistry and Biochemistry, University of California , San Diego, California 92093, United States
| | - Dimitrios Morikis
- Department of Bioengineering, University of California , Riverside, California 92521, United States
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9
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Electrostatic Interactions between Complement Regulator CD46(SCR1-2) and Adenovirus Ad11/Ad21 Fiber Protein Knob. Mol Biol Int 2015; 2015:967465. [PMID: 26357573 PMCID: PMC4556874 DOI: 10.1155/2015/967465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/12/2015] [Accepted: 07/16/2015] [Indexed: 11/24/2022] Open
Abstract
Adenoviruses bind to a variety of human cells to cause infection. Both the B2 adenovirus 11 and B1 adenovirus 21 use protein knobs to bind to complement regulator CD46(SCR1-2) in order to gain entry into host cells. In each complex, the two proteins are highly negatively charged but bind to each other at an interface with oppositely charged surface patches. We computationally generated single-alanine mutants of charged residues in the complexes CD46(SCR1-2)-Ad11k and CD46(SCR1-2)-Ad21k. We used electrostatic clustering and Poisson-Boltzmann free energy calculations to propose a hypothesis on the role of electrostatics in association. Our results delineate specific interfacial electrostatic interactions that are critical for association in both CD46(SCR1-2)-Ad11k and CD46(SCR1-2)-Ad21k. These results will serve as a predictive tool in the selection of mutants with desired binding affinity in experimental mutagenesis studies. This study will also serve as a foundation for the design of inhibitors to treat adenovirus infections.
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10
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A theoretical view of the C3d:CR2 binding controversy. Mol Immunol 2014; 64:112-22. [PMID: 25433434 DOI: 10.1016/j.molimm.2014.11.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 11/06/2014] [Indexed: 11/23/2022]
Abstract
The C3d:CR2(SCR1-2) interaction plays an important role in bridging innate and adaptive immunity, leading to enhanced antibody production at sites of complement activation. Over the past decade, there has been much debate over the binding mode of this interaction. An initial cocrystal structure (PDB: 1GHQ) was published in 2001, in which the only interactions observed were between the SCR2 domain of CR2 and a side-face of C3d whereas a cocrystal structure (PDB: 3OED) published in 2011 showed both the SCR1 and SCR2 domains of CR2 interacting with an acidic patch on the concave surface of C3d. The initial 1GHQ structure is at odds with the majority of existing biochemical data and the publication of the 3OED structure renewed uncertainty regarding the physiological relevance of 1GHQ, suggesting that crystallization may have been influenced by the presence of zinc acetate in the crystallization process. In our study, we used a variety of computational approaches to gain insight into the binding mode between C3d and CR2 and demonstrate that the binding site at the acidic patch (3OED) is electrostatically more favorable, exhibits better structural and dissociative stability, specifically at the SCR1 domain, and has higher binding affinity than the 1GHQ binding mode. We also observe that nonphysiological zinc ions enhance the formation of the C3d:CR2 complex at the side face of C3d (1GHQ) through increases in electrostatic favorability, intermolecular interactions, dissociative character and overall energetic favorability. These results provide a theoretical basis for the association of C3d:CR2 at the acidic cavity of C3d and provide an explanation for binding of CR2 at the side face of C3d in the presence of nonphysiological zinc ions.
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Ojha H, Panwar HS, Gorham RD, Morikis D, Sahu A. Viral regulators of complement activation: structure, function and evolution. Mol Immunol 2014; 61:89-99. [PMID: 24976595 DOI: 10.1016/j.molimm.2014.06.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 05/30/2014] [Accepted: 06/01/2014] [Indexed: 11/25/2022]
Abstract
The complement system surveillance in the host is effective in controlling viral propagation. Consequently, to subvert this effector mechanism, viruses have developed a series of adaptations. One among these is encoding mimics of host regulators of complement activation (RCA) which help viruses to avoid being labeled as 'foreign' and protect them from complement-mediated neutralization and complement-enhanced antiviral adaptive immunity. In this review, we provide an overview on the structure, function and evolution of viral RCA proteins.
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Affiliation(s)
- Hina Ojha
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India
| | - Hemendra Singh Panwar
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India
| | - Ronald D Gorham
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | - Dimitrios Morikis
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - Arvind Sahu
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India.
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12
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Wan H, Hu JP, Tian XH, Chang S. Molecular dynamics simulations of wild type and mutants of human complement receptor 2 complexed with C3d. Phys Chem Chem Phys 2013; 15:1241-51. [DOI: 10.1039/c2cp41388d] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Yadav VN, Pyaram K, Ahmad M, Sahu A. Species selectivity in poxviral complement regulators is dictated by the charge reversal in the central complement control protein modules. THE JOURNAL OF IMMUNOLOGY 2012; 189:1431-9. [PMID: 22732591 DOI: 10.4049/jimmunol.1200946] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Variola and vaccinia viruses, the two most important members of the family Poxviridae, are known to encode homologs of the human complement regulators named smallpox inhibitor of complement enzymes (SPICE) and vaccinia virus complement control protein (VCP), respectively, to subvert the host complement system. Intriguingly, consistent with the host tropism of these viruses, SPICE has been shown to be more human complement-specific than VCP, and in this study we show that VCP is more bovine complement-specific than SPICE. Based on mutagenesis and mechanistic studies, we suggest that the major determinant for the switch in species selectivity of SPICE and VCP is the presence of oppositely charged residues in the central complement control modules, which help enhance their interaction with factor I and C3b, the proteolytically cleaved form of C3. Thus, our results provide a molecular basis for the species selectivity in poxviral complement regulators.
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Affiliation(s)
- Viveka Nand Yadav
- National Centre for Cell Science, Pune University, Ganeshkhind, Pune 411007, India
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14
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Heinrich V, Lee CY. Blurred line between chemotactic chase and phagocytic consumption: an immunophysical single-cell perspective. J Cell Sci 2012; 124:3041-51. [PMID: 21914817 DOI: 10.1242/jcs.086413] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
An innate immune cell can sense a pathogen, either from a distance by recognizing chemoattractant stimuli or by direct physical contact. The pathogen is subsequently neutralized, which usually occurs through its phagocytic internalization. By investigating chemotaxis and phagocytosis from an immunophysical single-cell perspective, it now appears that the demarcation between these two processes is less distinct than originally thought. Several lines of evidence support this notion. First, chemotactic stimulation does not cease at the moment of initial contact between the cell and the pathogenic target. Second, even when classical chemotaxis of neutrophils is suppressed, the early cell response to contact with typical chemoattractant targets, such as zymosan, fungal spores or chemokine-coated particles, can still involve morphological attributes of chemotaxis. Recognizing that the changing morphology of motile cells is inextricably linked to physical cell behavior, this Commentary focuses on the mechanical aspects of the early response of innate immune cells to chemotactic and phagocytic stimuli. On the basis of this perspective, we propose that the combined study of chemotaxis and phagocytosis will, potentially, not only advance our grasp of the mechanisms underlying immune-cell motility but also open new lines of research that will promote a deeper understanding of the innate recognition of pathogens.
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Affiliation(s)
- Volkmar Heinrich
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA.
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15
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López de Victoria A, Kieslich CA, Rizos AK, Krambovitis E, Morikis D. Clustering of HIV-1 Subtypes Based on gp120 V3 Loop electrostatic properties. BMC BIOPHYSICS 2012; 5:3. [PMID: 22313935 PMCID: PMC3295656 DOI: 10.1186/2046-1682-5-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 02/07/2012] [Indexed: 11/10/2022]
Abstract
BACKGROUND The V3 loop of the glycoprotein gp120 of HIV-1 plays an important role in viral entry into cells by utilizing as coreceptor CCR5 or CXCR4, and is implicated in the phenotypic tropisms of HIV viruses. It has been hypothesized that the interaction between the V3 loop and CCR5 or CXCR4 is mediated by electrostatics. We have performed hierarchical clustering analysis of the spatial distributions of electrostatic potentials and charges of V3 loop structures containing consensus sequences of HIV-1 subtypes. RESULTS Although the majority of consensus sequences have a net charge of +3, the spatial distribution of their electrostatic potentials and charges may be a discriminating factor for binding and infectivity. This is demonstrated by the formation of several small subclusters, within major clusters, which indicates common origin but distinct spatial details of electrostatic properties. Some of this information may be present, in a coarse manner, in clustering of sequences, but the spatial details are largely lost. We show the effect of ionic strength on clustering of electrostatic potentials, information that is not present in clustering of charges or sequences. We also make correlations between clustering of electrostatic potentials and net charge, coreceptor selectivity, global prevalence, and geographic distribution. Finally, we interpret coreceptor selectivity based on the N6X7T8|S8X9 sequence glycosylation motif, the specific positive charge location according to the 11/24/25 rule, and the overall charge and electrostatic potential distribution. CONCLUSIONS We propose that in addition to the sequence and the net charge of the V3 loop of each subtype, the spatial distributions of electrostatic potentials and charges may also be important factors for receptor recognition and binding and subsequent viral entry into cells. This implies that the overall electrostatic potential is responsible for long-range recognition of the V3 loop with coreceptors CCR5/CXCR4, whereas the charge distribution contributes to the specific short-range interactions responsible for the formation of the bound complex. We also propose a scheme for coreceptor selectivity based on the sequence glycosylation motif, the 11/24/25 rule, and net charge.
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Affiliation(s)
| | - Chris A Kieslich
- Department of Bioengineering, University of California, Riverside 92521, USA
| | - Apostolos K Rizos
- Department of Chemistry, University of Crete and Foundation for Research and Technology-Hellas, FORTH-IESL, GR-71003, Heraklion, Crete, Greece
| | - Elias Krambovitis
- Department of Veterinary Medicine, University of Thessaly, Karditsa, Greece
| | - Dimitrios Morikis
- Department of Bioengineering, University of California, Riverside 92521, USA
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16
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Complement Inhibition by Staphylococcus aureus: Electrostatics of C3d–EfbC and C3d–Ehp Association. Cell Mol Bioeng 2011. [DOI: 10.1007/s12195-011-0195-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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17
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Electrostatic exploration of the C3d-FH4 interaction using a computational alanine scan. Mol Immunol 2011; 48:1844-50. [PMID: 21683447 DOI: 10.1016/j.molimm.2011.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 05/09/2011] [Indexed: 11/20/2022]
Abstract
The complement system is a component of innate immunity and is activated by a cascade of protein interactions whose function is vital to our ability to fight infection. When proper regulation fails, the complement system is unable to recognize "self" from "nonself" and, therefore, attacks own tissues leading to autoimmune diseases. The central protein of the complement system is C3, which is the convergence point of three independently activated but communicating pathways. Regulation of C3 occurs through modular proteins which consist of many repeats of complement control protein (CCP) modules. CCP modules have diverse sequences, similar structures, and diverse physicochemical compositions, with excess of charge being a predominant characteristic. The goal of our study is to understand the electrostatic mechanism that underlies the interaction between the C3d domain of C3 and the fourth module of the complement regulator Factor H (FH4). We have performed a computational alanine scan in which we have replaced every ionizable amino acid, one at a time, with an alanine to generate a family of mutants for the C3d-FH4 complex. We have used Poisson-Boltzmann electrostatic calculations in combination with clustering of spatial distributions of electrostatic potentials and free energy calculations to delineate the contribution of each replaced amino acid to the C3d-FH4 interaction. We have analyzed our data in view of a two-step model which separates association into long-range recognition and short-range binding and we have identified key amino acids that contribute to association. We discuss the complex role of C3d in binding FH4 and the bacterial proteins Efb/Ehp from Staphylococcus aureus.
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The effect of electrostatics on factor H function and related pathologies. J Mol Graph Model 2011; 29:1047-55. [PMID: 21605993 DOI: 10.1016/j.jmgm.2011.04.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 04/26/2011] [Accepted: 04/28/2011] [Indexed: 12/15/2022]
Abstract
Factor H (FH) contributes to the regulation of the complement system by binding to polyanionic surfaces and the proteins C3b/C3c/C3d. This implicates charge and electrostatic interactions in recognition and binding of FH. Despite the large amount of experimental and pathology data the exact mechanism at molecular level is not yet known. We have implemented a computational framework for comparative analysis of the charge and electrostatic diversity of FH modules and C3b domains to identify electrostatic hotspots and predict potential binding sites. Our electrostatic potential clustering analysis shows that charge distributions and electrostatic potential distributions are more useful in understanding C3b-FH interactions than net charges alone. We present a model of non-specific electrostatic interactions of FH with polyanion-rich surfaces and specific interactions with C3b, using our computational data and existing experimental data. We discuss the electrostatic contributions to the formation of the C3b-FH complex and the competition between FH and Factor Bb (Bb) for binding to C3b. We also discuss the significance of mutations of charged amino acids in the pathobiology of FH-mediated disease, such as age-related macular degeneration, atypical hemolytic uremic syndrome, and dense deposit disease. Our data can be used to guide future experimental studies.
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Kieslich CA, Morikis D, Yang J, Gunopulos D. Automated computational framework for the analysis of electrostatic similarities of proteins. Biotechnol Prog 2011; 27:316-25. [PMID: 21485028 DOI: 10.1002/btpr.541] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2010] [Indexed: 12/14/2022]
Abstract
Charge plays an important role in protein-protein interactions. In the case of excessively charged proteins, their electrostatic potentials contribute to the processes of recognition and binding with other proteins or ligands. We present an automated computational framework for determining the contribution of each charged amino acid to the electrostatic properties of proteins, at atomic resolution level. This framework involves computational alanine scans, calculation of Poisson-Boltzmann electrostatic potentials, calculation of electrostatic similarity distances (ESDs), hierarchical clustering analysis of ESDs, calculation of solvation free energies of association, and visualization of the spatial distributions of electrostatic potentials. The framework is useful to classify families of mutants with similar electrostatic properties and to compare them with the parent proteins in the complex. The alanine scan mutants introduce perturbations in the local electrostatic properties of the proteins and aim in delineating the contribution of each mutated amino acid in the spatial distribution of electrostatic potential, and in biological function when electrostatics is a dominant contributing factor in protein-protein interactions. The framework can be used to design new proteins with tailored electrostatic properties, such as immune system regulators, inhibitors, and vaccines, and in guiding experimental studies. We present an example for the interaction of the immune system protein C3d (the d-fragment of complement protein C3) with its receptor CR2, and we discuss our data in view of a binding site controversy.
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Affiliation(s)
- Chris A Kieslich
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
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20
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Electrostatic clustering and free energy calculations provide a foundation for protein design and optimization. Ann Biomed Eng 2010; 39:1252-63. [PMID: 21140293 PMCID: PMC3069318 DOI: 10.1007/s10439-010-0226-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2010] [Accepted: 11/24/2010] [Indexed: 01/14/2023]
Abstract
Electrostatic interactions are ubiquitous in proteins and dictate stability and function. In this review, we discuss several methods for the analysis of electrostatics in protein–protein interactions. We discuss alanine-scanning mutagenesis, Poisson–Boltzmann electrostatics, free energy calculations, electrostatic similarity distances, and hierarchical clustering of electrostatic potentials. Our recently developed computational framework, known as Analysis of Electrostatic Similarities Of Proteins (AESOP), incorporates these tools to efficiently elucidate the role of electrostatic potentials in protein interactions. We present the application of AESOP to several proteins and protein complexes, for which charge is purported to facilitate protein association. Specifically, we illustrate how recent work has shaped the formulation of electrostatic calculations, the correlation of electrostatic free energies and electrostatic potential clustering results with experimental binding and activity data, the pH dependence of protein stability and association, the design of mutant proteins with enhanced immunological activity, and how AESOP can expose deficiencies in structural models and experimental data. This integrative approach can be utilized to develop mechanistic models and to guide experimental studies by predicting mutations with desired physicochemical properties and function. Alteration of the electrostatic properties of proteins offers a basis for the design of proteins with optimized binding and activity.
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Pyaram K, Yadav VN, Reza MJ, Sahu A. Virus–complement interactions: an assiduous struggle for dominance. Future Virol 2010. [DOI: 10.2217/fvl.10.60] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The complement system is a major component of the innate immune system that recognizes invading pathogens and eliminates them by means of an array of effector mechanisms, in addition to using direct lytic destruction. Viruses, in spite of their small size and simple composition, are also deftly recognized and neutralized by the complement system. In turn, as a result of years of coevolution with the host, viruses have developed multiple mechanisms to evade the host complement. These complex interactions between the complement system and viruses have been an area of focus for over three decades. In this article, we provide a broad overview of the field using key examples and up-to-date information on the complement-evasion strategies of viruses.
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Affiliation(s)
- Kalyani Pyaram
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India
| | - Viveka Nand Yadav
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India
| | - Malik Johid Reza
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India
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Contribution of specific amino acid changes in penicillin binding protein 1 to amoxicillin resistance in clinical Helicobacter pylori isolates. Antimicrob Agents Chemother 2010; 55:101-9. [PMID: 20956585 DOI: 10.1128/aac.00545-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Amoxicillin is commonly used to treat Helicobacter pylori, a major cause of peptic ulcers, stomach cancer, and B-cell mucosa-associated lymphoid tissue lymphoma. Amoxicillin resistance in H. pylori is increasing steadily, especially in developing countries, leading to treatment failures. In this study, we characterize the mechanism of amoxicillin resistance in the U.S. clinical isolate B258. Transformation of amoxicillin-susceptible strain 26695 with the penicillin binding protein 1 gene (pbp1) from B258 increased the amoxicillin resistance of 26695 to equal that of B258, while studies using biotinylated amoxicillin showed a decrease in the binding of amoxicillin to the PBP1 of B258. Transformation with 4 pbp1 fragments, each encompassing several amino acid substitutions, combined with site-directed mutagenesis studies, identified 3 amino acid substitutions in PBP1 of B258 which affected amoxicillin susceptibility (Val 469 Met, Phe 473 Leu, and Ser 543 Arg). Homology modeling showed the spatial orientation of these specific amino acid changes in PBP1 from 26695 and B258. The results of these studies demonstrate that amoxicillin resistance in the clinical U.S. isolate B258 is due solely to an altered PBP1 protein with a lower binding affinity for amoxicillin. Homology modeling analyses using previously identified amino acid substitutions of amoxicillin-resistant PBP1s demonstrate the importance of specific amino acid substitutions in PBP1 that affect the binding of amoxicillin in the putative binding cleft, defining those substitutions deemed most important in amoxicillin resistance.
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Chae K, Gonong BJ, Kim SC, Kieslich CA, Morikis D, Balasubramanian S, Lord EM. A multifaceted study of stigma/style cysteine-rich adhesin (SCA)-like Arabidopsis lipid transfer proteins (LTPs) suggests diversified roles for these LTPs in plant growth and reproduction. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:4277-90. [PMID: 20667964 PMCID: PMC2955742 DOI: 10.1093/jxb/erq228] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 07/02/2010] [Accepted: 07/06/2010] [Indexed: 05/19/2023]
Abstract
Lily stigma/style cysteine-rich adhesin (SCA), a plant lipid transfer protein (LTP) which is secreted into the extracellular matrix, functions in pollen tube guidance in fertilization. A gain-of-function mutant (ltp5-1) for Arabidopsis LTP5, an SCA-like molecule, was recently shown to display defects in sexual reproduction. In the current study, it is reported that ltp5-1 plants have dwarfed primary shoots, delayed hypocotyl elongation, various abnormal tissue fusions, and display multibranching. These mutant phenotypes in vegetative growth are recessive. No abnormality was found in ltp5-1/+ plants. In a phylogenetic analysis of plant LTPs, SCA-like Arabidopsis LTPs were classified with conventional plant LTPs. Homology modelling-based electrostatic similarity index (ESI) clustering was used to show diversity in spatial distributions of electrostatic potentials of SCA-like LTPs, suggestive of their various roles in interaction in the extracellular matrix space. β-Glucuronidase (GUS) analysis showed that SCA-like Arabidopsis LTP genes are diversely present in various tissues. LTP4 was found specifically in the guard cells and LTP6 in trichomes as well as in other tissues. LTP1 levels were specifically abundant in the stigma, and both LTP3 and LTP6 in the ovules. LTP2 and LTP4 gene levels were up-regulated in whole seedlings with 20% polyethylene glycol (PEG) and 300 mM NaCl treatments, respectively. LTP5 was up-regulated in the hypocotyl with 3 d dark growth conditions. LTP6 was specifically expressed in the tip of the cotyledon under drought stress conditions. The results suggest that SCA-like Arabidopsis LTPs are multifunctional, with diversified roles in plant growth and reproduction.
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Affiliation(s)
- Keun Chae
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
- Center for Plant Cell Biology, University of California, Riverside, CA 92521, USA
| | - Benedict J. Gonong
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
| | - Seung-Chul Kim
- Department of Biological Sciences, SungKyunKwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746, Korea
| | - Chris A. Kieslich
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | - Dimitrios Morikis
- Center for Plant Cell Biology, University of California, Riverside, CA 92521, USA
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | | | - Elizabeth M. Lord
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
- Center for Plant Cell Biology, University of California, Riverside, CA 92521, USA
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Pyaram K, Kieslich CA, Yadav VN, Morikis D, Sahu A. Influence of electrostatics on the complement regulatory functions of Kaposica, the complement inhibitor of Kaposi's sarcoma-associated herpesvirus. THE JOURNAL OF IMMUNOLOGY 2010; 184:1956-67. [PMID: 20089702 DOI: 10.4049/jimmunol.0903261] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Kaposica, the complement regulator of Kaposi's sarcoma-associated herpesvirus, inhibits complement by supporting factor I-mediated inactivation of the proteolytically activated form of C3 (C3b) and C4 (C4b) (cofactor activity [CFA]) and by accelerating the decay of classical and alternative pathway C3-convertases (decay-accelerating activity [DAA]). Previous data suggested that electrostatic interactions play a critical role in the binding of viral complement regulators to their targets, C3b and C4b. We therefore investigated how electrostatic potential on Kaposica influences its activities. We built a homology structure of Kaposica and calculated the electrostatic potential of the molecule, using the Poisson-Boltzmann equation. Mutants were then designed to alter the overall positive potential of the molecule or of each of its domains and linkers by mutating Lys/Arg to Glu/Gln, and the functional activities of the expressed mutants were analyzed. Our data indicate that 1) positive potential at specific sites and not the overall positive potential on the molecule guides the CFAs and classical pathway DAA; 2) positive potential around the linkers between complement control protein domains (CCPs) 1-2 and 2-3 is more important for DAAs than for CFAs; 3) positive potential in CCP1 is crucial for binding to C3b and C4b, and thereby its functional activities; 4) conversion to negative or enhancement of negative potential for CCPs 2-4 has a marked effect on C3b-linked activities as opposed to C4b-linked activities; and 5) reversal of the electrostatic potential of CCP4 to negative has a differential effect on classical and alternative pathway DAAs. Together, our data provide functional relevance to conservation of positive potential in CCPs 1 and 4 and the linkers of viral complement regulators.
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Affiliation(s)
- Kalyani Pyaram
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune, India
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25
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Liszewski MK, Leung MK, Hauhart R, Fang CJ, Bertram P, Atkinson JP. Smallpox inhibitor of complement enzymes (SPICE): dissecting functional sites and abrogating activity. THE JOURNAL OF IMMUNOLOGY 2009; 183:3150-9. [PMID: 19667083 DOI: 10.4049/jimmunol.0901366] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although smallpox was eradicated as a global illness more than 30 years ago, variola virus and other related pathogenic poxviruses, such as monkeypox, remain potential bioterrorist weapons or could re-emerge as natural infections. Poxviruses express virulence factors that down-modulate the host's immune system. We previously compared functional profiles of the poxviral complement inhibitors of smallpox, vaccinia, and monkeypox known as SPICE, VCP (or VICE), and MOPICE, respectively. SPICE was the most potent regulator of human complement and attached to cells via glycosaminoglycans. The major goals of the present study were to further characterize the complement regulatory and heparin binding sites of SPICE and to evaluate a mAb that abrogates its function. Using substitution mutagenesis, we established that (1) elimination of the three heparin binding sites severely decreases but does not eliminate glycosaminoglycan binding, (2) there is a hierarchy of activity for heparin binding among the three sites, and (3) complement regulatory sites overlap with each of the three heparin binding motifs. By creating chimeras with interchanges of SPICE and VCP residues, a combination of two SPICE amino acids (H77 plus K120) enhances VCP activity approximately 200-fold. Also, SPICE residue L131 is critical for both complement regulatory function and accounts for the electrophoretic differences between SPICE and VCP. An evolutionary history for these structure-function adaptations of SPICE is proposed. Finally, we identified and characterized a mAb that inhibits the complement regulatory activity of SPICE, MOPICE, and VCP and thus could be used as a therapeutic agent.
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Affiliation(s)
- M Kathryn Liszewski
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Mapping of functional domains in herpesvirus saimiri complement control protein homolog: complement control protein domain 2 is the smallest structural unit displaying cofactor and decay-accelerating activities. J Virol 2009; 83:10299-304. [PMID: 19640995 DOI: 10.1128/jvi.00217-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Herpesvirus saimiri encodes a functional homolog of human regulator-of-complement-activation proteins named CCPH that inactivates complement by accelerating the decay of C3 convertases and by serving as a cofactor in factor I-mediated inactivation of their subunits C3b and C4b. Here, we map the functional domains of CCPH. We demonstrate that short consensus repeat 2 (SCR2) is the minimum domain essential for classical/lectin pathway C3 convertase decay-accelerating activity as well as for factor I cofactor activity for C3b and C4b. Thus, CCPH is the first example wherein a single SCR domain has been shown to display complement regulatory functions.
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27
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Inhibition of complement and CD14 attenuates the Escherichia coli-induced inflammatory response in porcine whole blood. Infect Immun 2008; 77:725-32. [PMID: 19047409 DOI: 10.1128/iai.01305-08] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The innate immune response is a double-edged sword in systemic inflammation and sepsis. Uncontrolled or inappropriate activation can damage and be lethal to the host. Several studies have investigated inhibition of downstream mediators, including tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta). Emerging evidence indicates that upstream inhibition is a better therapeutic approach for attenuating damaging immune activation. Therefore, we investigated inhibition of two central innate immune pathways, those of complement and CD14/Toll-like receptor 4 (TLR4)/myeloid differentiation protein 2 (MD-2), in a porcine in vitro model of Escherichia coli-induced inflammation. Porcine whole blood anticoagulated with lepuridin, which did not interfere with the complement system, was incubated with E. coli lipopolysaccharide (LPS) or whole bacteria. Inhibitors of complement and CD14 and thus the LPS CD14/TLR4/MD-2 receptor complex were tested to investigate the effect on the inflammatory response. A broad range of inflammatory readouts were used to monitor the effect. Anti-CD14 was found to saturate the CD14 molecule on granulocytes and completely inhibited LPS-induced proinflammatory cytokines in a dose-dependent manner. Anti-CD14 significantly reduced the levels of the E. coli-induced proinflammatory cytokines TNF-alpha and IL-1beta, but not IL-8, in a dose-dependent manner. No effect on bacterial clearance was seen. Vaccinia complement control protein and smallpox inhibitor of complement enzymes, two Orthopoxvirus-encoded complement inhibitors, completely inhibited complement activation. Furthermore, these agents almost completely inhibited the expression of wCD11R3, which is associated with CD18 as a beta2 integrin, on porcine granulocytes and decreased IL-8 levels significantly in a dose-dependent manner. As expected, complement inhibition reduced bacterial clearance. We conclude that inhibition of complement and CD14 attenuates E. coli-induced inflammation and might be used as a therapeutic regimen in gram-negative sepsis along with appropriate treatment with antibiotics.
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28
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Liszewski MK, Bertram P, Leung MK, Hauhart R, Zhang L, Atkinson JP. Smallpox inhibitor of complement enzymes (SPICE): regulation of complement activation on cells and mechanism of its cellular attachment. THE JOURNAL OF IMMUNOLOGY 2008; 181:4199-207. [PMID: 18768877 DOI: 10.4049/jimmunol.181.6.4199] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Despite eradication of smallpox three decades ago, public health concerns remain due to its potential use as a bioterrorist weapon. Smallpox and other orthopoxviruses express virulence factors that inhibit the host's complement system. In this study, our goals were to characterize the ability of the smallpox inhibitor of complement enzymes, SPICE, to regulate human complement on the cell surface. We demonstrate that SPICE binds to a variety of cell types and that the heparan sulfate and chondroitin sulfate glycosaminoglycans serve as attachment sites. A transmembrane-engineered version as well as soluble recombinant SPICE inhibited complement activation at the C3 convertase step with equal or greater efficiency than that of the related host regulators. Moreover, SPICE attached to glycosaminoglycans was more efficient than transmembrane SPICE. We also demonstrate that this virulence activity of SPICE on cells could be blocked by a mAb to SPICE. These results provide insights related to the complement inhibitory activities of poxviral inhibitors of complement and describe a mAb with therapeutic potential.
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Affiliation(s)
- M Kathryn Liszewski
- Department of Medicine/Division of Rheumatology, Washington University School of Medicine, St. Louis, MO 63110, USA
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29
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Identification of hot spots in the variola virus complement inhibitor (SPICE) for human complement regulation. J Virol 2008; 82:3283-94. [PMID: 18216095 DOI: 10.1128/jvi.01935-07] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Variola virus, the causative agent of smallpox, encodes a soluble complement regulator named SPICE. Previously, SPICE has been shown to be much more potent in inactivating human complement than the vaccinia virus complement control protein (VCP), although they differ only in 11 amino acid residues. In the present study, we have expressed SPICE, VCP, and mutants of VCP by substituting each or more of the 11 non-variant VCP residues with the corresponding residue of SPICE to identify hot spots that impart functional advantage to SPICE over VCP. Our data indicate that (i) SPICE is approximately 90-fold more potent than VCP in inactivating human C3b, and the residues Y98, Y103, K108 and K120 are predominantly responsible for its enhanced activity; (ii) SPICE is 5.4-fold more potent in inactivating human C4b, and residues Y98, Y103, K108, K120 and L193 mainly dictate this increase; (iii) the classical pathway decay-accelerating activity of activity is only twofold higher than that of VCP, and the 11 mutations in SPICE do not significantly affect this activity; (iv) SPICE possesses significantly greater binding ability to human C3b compared to VCP, although its binding to human C4b is lower than that of VCP; (v) residue N144 is largely responsible for the increased binding of SPICE to human C3b; and (vi) the human specificity of SPICE is dictated primarily by residues Y98, Y103, K108, and K120 since these are enough to formulate VCP as potent as SPICE. Together, these results suggest that principally 4 of the 11 residues that differ between SPICE and VCP partake in its enhanced function against human complement.
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Kuttner-Kondo L, Hourcade DE, Anderson VE, Muqim N, Mitchell L, Soares DC, Barlow PN, Medof ME. Structure-based mapping of DAF active site residues that accelerate the decay of C3 convertases. J Biol Chem 2007; 282:18552-18562. [PMID: 17395591 DOI: 10.1074/jbc.m611650200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Focused complement activation on foreign targets depends on regulatory proteins that decay the bimolecular C3 convertases. Although this process is central to complement control, how the convertases engage and disassemble is not established. The second and third complement control protein (CCP) modules of the cell surface regulator, decay-accelerating factor (DAF, CD55), comprise the simplest structure mediating this activity. Positioning the functional effects of 31 substitution mutants of DAF CCP2 to -4 on partial structures was previously reported. In light of the high resolution crystal structure of the DAF four-CCP functional region, we now reexamine the effects of these and 40 additional mutations. Moreover, we map six monoclonal antibody epitopes and overlap their effects with those of the amino acid substitutions. The data indicate that the interaction of DAF with the convertases is mediated predominantly by two patches approximately 13 A apart, one centered around Arg69 and Arg96 on CCP2 and the other around Phe148 and Leu171 on CCP3. These patches on the same face of the adjacent modules bracket an intermodular linker of critical length (16 A.) Although the key DAF residues in these patches are present or there are conservative substitutions in all other C3 convertase regulators that mediate decay acceleration and/or provide factor I-cofactor activity, the linker region is highly conserved only in the former. Intra-CCP regions also differ. Linker region comparisons suggest that the active CCPs of the decay accelerators are extended, whereas those of the cofactors are tilted. Intra-CCP comparisons suggest that the two classes of regulators bind different regions on their respective ligands.
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Affiliation(s)
- Lisa Kuttner-Kondo
- Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Dennis E Hourcade
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Vernon E Anderson
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Nasima Muqim
- Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Lynne Mitchell
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Dinesh C Soares
- Institute of Structural and Molecular Biology and School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, Scotland, United Kingdom
| | - Paul N Barlow
- Institute of Structural and Molecular Biology and School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, Scotland, United Kingdom
| | - M Edward Medof
- Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106.
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31
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Zhang L, Mallik B, Morikis D. Immunophysical exploration of C3d-CR2(CCP1-2) interaction using molecular dynamics and electrostatics. J Mol Biol 2007; 369:567-83. [PMID: 17434528 DOI: 10.1016/j.jmb.2007.02.101] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Revised: 01/31/2007] [Accepted: 02/21/2007] [Indexed: 10/23/2022]
Abstract
The formation of the complex between the d-fragment of the complement component C3 (C3d) and the modular complement receptor-2 (CR2) is important for cross-linking foreign antigens with surface-bound antibodies and C3d on the surface of B cells. The first two modules of CR2, complement control protein modules (CCPs), participate in non-bonded interactions with C3d. We have used computational methods to analyze the dynamic and electrostatic properties of the C3d-CR2(CCP1-2) complex. The interaction between C3d and CR2 is known to depend on pH and ionic strength. Also, the intermodular mobility of the CR2 modules has been questioned before. We performed a 10 ns molecular dynamics simulation to generate a relaxed structure from crystal packing effects for the C3d-CR2(CCP1-2) complex and to study the energetics of the C3d-CR2(CCP1-2) association. The MD simulation suggests a tendency for intermodular twisting in CR2(CCP1-2). We propose a two-step model for recognition and binding of C3d with CR2(CCP1-2), driven by long and short/medium-range electrostatic interactions. We have calculated the matrix of specific short/medium-range pairwise electrostatic free energies of interaction involved in binding and in intermodular communications. Electrostatic interactions may mediate allosteric effects important for C3d-CR2(CCP1-2) association. We present calculations for the pH and ionic strength-dependence of C3d-CR2(CCP1-2) ionization free energies, which are in overall agreement with experimental binding data. We show how comparison of the calculated and experimental data allows for the decomposition of the contributions of electrostatic from other effects in association. We critically compare predicted stabilities for several mutants of the C3d-CR2(CCP1-2) complex with the available experimental data for binding ability. Finally, we propose that CR2(CCP1-2) is capable of assuming a large array of intermodular topologies, ranging from closed V-shaped to open linear states, with similar recognition properties for C3d, but we cannot exclude an additional contact site with C3d.
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Affiliation(s)
- Li Zhang
- Department of Chemistry, University of California at Riverside, Riverside, CA 92521, USA
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Singh AK, Mullick J, Bernet J, Sahu A. Functional characterization of the complement control protein homolog of herpesvirus saimiri: ARG-118 is critical for factor I cofactor activities. J Biol Chem 2006; 281:23119-28. [PMID: 16760474 DOI: 10.1074/jbc.m603085200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Herpesvirus saimiri (HVS) is a lymphotropic virus that causes T-cell lymphomas in New World primates. It encodes a structural homolog of complement control proteins named complement control protein homolog (CCPH). Previously, CCPH has been shown to inhibit C3d deposition on target cells exposed to complement. Here we have studied the mechanism by which it inactivates complement. We have expressed the soluble form of CCPH in Escherichia coli, purified to homogeneity and compared its activity to vaccinia virus complement control protein (VCP) and human complement regulators factor H and soluble complement receptor 1. The expressed soluble form of CCPH bound to C3b (KD = 19.2 microm) as well as to C4b (KD = 0.8 microm) and accelerated the decay of the classical/lectin as well as alternative pathway C3-convertases. In addition, it also served as factor I cofactor and supported factor I-mediated inactivation of both C3b and C4b. Time course analysis indicated that although its rate of inactivation of C4b is comparable with VCP, it is 14-fold more potent than VCP in inactivating C3b. Site-directed mutagenesis revealed that Arg-118, which corresponds to Lys-120 of variola virus complement regulator SPICE (a residue critical for its enhanced C3b cofactor activity), contributes significantly in enhancing this activity. Thus, our data indicate that HVS encodes a potent complement inhibitor that allows HVS to evade the host complement attack.
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Affiliation(s)
- Akhilesh K Singh
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India
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