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Golob-Urbanc A, Rajčević U, Strmšek Ž, Jerala R. Design of split superantigen fusion proteins for cancer immunotherapy. J Biol Chem 2019; 294:6294-6305. [PMID: 30782846 DOI: 10.1074/jbc.ra118.006742] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 01/26/2019] [Indexed: 11/06/2022] Open
Abstract
Several antibody-targeting cancer immunotherapies have been developed based on T cell activation at the target cells. One of the most potent activators of T cells are bacterial superantigens, which bind to major histocompatibility complex class II on antigen-presenting cells and activate T cells through T cell receptor. Strong T cell activation is also one of the main weaknesses of this strategy as it may lead to systemic T cell activation. To overcome the limitation of conventional antibody-superantigen fusion proteins, we have split a superantigen into two fragments, individually inactive, until both fragments came into close proximity and reassembled into a biologically active form capable of activating T cell response. A screening method based on fusion between SEA and coiled-coil heterodimers was developed that enabled detection of functional split SEA designs. The split SEA design that demonstrated efficacy in fusion with coiled-coil dimer forming polypeptides was fused to a single chain antibody specific for tumor antigen CD20. This design selectively activated T cells by split SEA-scFv fusion binding to target cells.
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Fink T, Lonzarić J, Praznik A, Plaper T, Merljak E, Leben K, Jerala N, Lebar T, Strmšek Ž, Lapenta F, Benčina M, Jerala R. Design of fast proteolysis-based signaling and logic circuits in mammalian cells. Nat Chem Biol 2019; 15:115-122. [PMID: 30531965 PMCID: PMC7069760 DOI: 10.1038/s41589-018-0181-6] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/05/2018] [Indexed: 01/05/2023]
Abstract
Cellular signal transduction is predominantly based on protein interactions and their post-translational modifications, which enable a fast response to input signals. Owing to difficulties in designing new unique protein-protein interactions, designed cellular logic has focused on transcriptional regulation; however, that process has a substantially slower response, because it requires transcription and translation. Here, we present de novo design of modular, scalable signaling pathways based on proteolysis and designed coiled coils (CC) and implemented in mammalian cells. A set of split proteases with highly specific orthogonal cleavage motifs was constructed and combined with strategically positioned cleavage sites and designed orthogonal CC dimerizing domains with tunable affinity for competitive displacement after proteolytic cleavage. This framework enabled the implementation of Boolean logic functions and signaling cascades in mammalian cells. The designed split-protease-cleavable orthogonal-CC-based (SPOC) logic circuits enable response to chemical or biological signals within minutes rather than hours and should be useful for diverse medical and nonmedical applications.
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Cochet F, Facchini FA, Zaffaroni L, Billod JM, Coelho H, Holgado A, Braun H, Beyaert R, Jerala R, Jimenez-Barbero J, Martin-Santamaria S, Peri F. Novel carboxylate-based glycolipids: TLR4 antagonism, MD-2 binding and self-assembly properties. Sci Rep 2019; 9:919. [PMID: 30696900 PMCID: PMC6351529 DOI: 10.1038/s41598-018-37421-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 11/14/2018] [Indexed: 12/31/2022] Open
Abstract
New monosaccharide-based lipid A analogues were rationally designed through MD-2 docking studies. A panel of compounds with two carboxylate groups as phosphates bioisosteres, was synthesized with the same glucosamine-bis-succinyl core linked to different unsaturated and saturated fatty acid chains. The binding of the synthetic compounds to purified, functional recombinant human MD-2 was studied by four independent methods. All compounds bound to MD-2 with similar affinities and inhibited in a concentration-dependent manner the LPS-stimulated TLR4 signaling in human and murine cells, while being inactive as TLR4 agonists when provided alone. A compound of the panel was tested in vivo and was not able to inhibit the production of proinflammatory cytokines in animals. This lack of activity is probably due to strong binding to serum albumin, as suggested by cell experiments in the presence of the serum. The interesting self-assembly property in solution of this type of compounds was investigated by computational methods and microscopy, and formation of large vesicles was observed by cryo-TEM microscopy.
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Lebar T, Verbič A, Ljubetič A, Jerala R. Polarized displacement by transcription activator-like effectors for regulatory circuits. Nat Chem Biol 2019; 15:80-87. [PMID: 30455466 DOI: 10.1038/s41589-018-0163-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 10/05/2018] [Indexed: 01/26/2023]
Abstract
The interplay between DNA-binding proteins plays an important role in transcriptional regulation and could increase the precision and complexity of designed regulatory circuits. Here we show that a transcription activator-like effector (TALE) can displace another TALE protein from DNA in a highly polarized manner, displacing only the 3'- but not 5'-bound overlapping or adjacent TALE. We propose that the polarized displacement by TALEs is based on its multipartite nature of binding to DNA. The polarized TALE displacement provides strategies for the specific regulation of gene expression, for construction of all two-input Boolean genetic logic circuits based on the robust propagation of the displacement across multiple neighboring sites, for displacement of zinc finger-based transcription factors and for suppression of Cas9-gRNA-mediated genome cleavage, enriching the synthetic biology toolbox and contributing to the understanding of the underlying principles of the facilitated displacement.
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Lainšček D, Kadunc L, Keber MM, Bratkovič IH, Romih R, Jerala R. Delivery of an Artificial Transcription Regulator dCas9-VPR by Extracellular Vesicles for Therapeutic Gene Activation. ACS Synth Biol 2018; 7:2715-2725. [PMID: 30513193 DOI: 10.1021/acssynbio.8b00192] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The CRISPR/Cas system has been developed as a potent tool for genome engineering and transcription regulation. However, the efficiency of the delivery of the system into cells, particularly for therapeutic in vivo applications, remains a major bottleneck. Extracellular vesicles (EVs), released by eukaryotic cells, can mediate the transfer of various molecules, including nucleic acids and proteins. We show the packaging and delivery of the CRISPR/Cas system via EVs to the target cells, combining the advantages of both technological platforms. A genome editing with designed extracellular vesicles (GEDEX) system generated by the producer cells can transfer the designed transcriptional regulator dCas9-VPR complexed with appropriate targeting gRNAs enabling activation of gene transcription. We show functional delivery in mammalian cells as well in the animals. The therapeutic efficiency of in vivo delivery of dCas9-VPR/sgRNA GEDEX is demonstrated in a mouse model of liver damage counteracted by upregulation of the endogenous hepatocyte growth factor, demonstrating the potential for therapeutic applications.
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56
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Hafner-Bratkovič I, Sušjan P, Lainšček D, Tapia-Abellán A, Cerović K, Kadunc L, Angosto-Bazarra D, Pelegrin P, Jerala R. NLRP3 lacking the leucine-rich repeat domain can be fully activated via the canonical inflammasome pathway. Nat Commun 2018; 9:5182. [PMID: 30518920 PMCID: PMC6281599 DOI: 10.1038/s41467-018-07573-4] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 11/08/2018] [Indexed: 11/23/2022] Open
Abstract
NLRP3 is a cytosolic sensor triggered by different pathogen- and self-derived signals that plays a central role in a variety of pathological conditions, including sterile inflammation. The leucine-rich repeat domain is present in several innate immune receptors, where it is frequently responsible for sensing danger signals and regulation of activation. Here we show by reconstitution of truncated and chimeric variants into Nlrp3−/− macrophages that the leucine-rich repeat domain is dispensable for activation and self-regulation of NLRP3 by several different triggers. The pyrin domain on the other hand is required to maintain NLRP3 in the inactive conformation. A fully responsive minimal NLRP3 truncation variant reconstitutes peritonitis in Nlrp3−/− mice. We demonstrate that in contrast to pathogen-activated NLRC4, the constitutively active NLRP3 molecule cannot engage wild-type NLRP3 molecules in a self-catalytic oligomerization. This lack of signal amplification is likely a protective mechanism to decrease sensitivity to endogenous triggers to impede autoinflammation. Activation of the NLRP3 inflammasome is associated with various diseases but its activation mechanism is not fully understood. Here, the authors determine the impact of different NLRP3 domains on sensing NLRP3 triggers, inflammasome assembly and regulation of NLRP3 inflammasome activation.
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Pohar J, Lainšček D, Kunšek A, Cajnko MM, Jerala R, Benčina M. Publisher Correction: Phosphodiester backbone of the CpG motif within immunostimulatory oligodeoxynucleotides augments activation of Toll-like receptor 9. Sci Rep 2018; 8:355. [PMID: 29305575 PMCID: PMC5756238 DOI: 10.1038/s41598-017-17988-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Aupič J, Lapenta F, Jerala R. SwitCCh: Metal-Site Design for Controlling the Assembly of a Coiled-Coil Homodimer. Chembiochem 2018; 19:2453-2457. [PMID: 30260542 DOI: 10.1002/cbic.201800578] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Indexed: 11/09/2022]
Abstract
Conformational change of proteins in response to chemical or physical signals is the underlying principle of many regulatory and transport mechanisms in biological systems. The ability to design proteins the conformational state of which can be precisely and reversibly controlled would facilitate the development of molecular machines tailored for specific applications. Here we explore metal-binding site design to engineer a peptide-based conformational switch called SwitCCh that assembles into a homodimeric coiled-coil in response to the addition of ZnII ions or low pH. Addition of ZnII promoted formation of a parallel homodimer with an increase in thermal stability by more than 30 °C. The peptide could be reversibly cycled between the coiled-coil and random conformation. Furthermore, the SwitCCh peptide was orthogonal to the previously developed coiled-coil dimer set, indicating it could be used for regulated self-assembly of coiled-coil based nanostructures and materials.
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Ulijn RV, Jerala R. Peptide and protein nanotechnology into the 2020s: beyond biology. Chem Soc Rev 2018; 47:3391-3394. [PMID: 29761188 DOI: 10.1039/c8cs90055h] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Guest editors Rein Ulijn and Roman Jerala introduce the Peptide and protein nanotechnology themed issue of Chemical Society Reviews.
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Ivičak-Kocjan K, Forstnerič V, Panter G, Jerala R, Benčina M. Extension and refinement of the recognition motif for Toll-like receptor 5 activation by flagellin. J Leukoc Biol 2018; 104:767-776. [PMID: 29920759 DOI: 10.1002/jlb.3vma0118-035r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/24/2018] [Accepted: 05/16/2018] [Indexed: 11/07/2022] Open
Abstract
TLRs sense conserved and essential molecular components of microbes that invade multicellular organisms. The wide range of TLR agonists, differing in size and shape, is recognized either through a single or a pair of binding sites on the ectodomains of TLRs. TLR5 recognizes bacterial flagellin through two distinct binding sites on the ectodomain, the first facilitating primary binding of flagellin and the second guiding receptor dimerization necessary for signaling. The regions of flagellin recognized by TLR5 encompass key functional regions within the D1 domain of flagellin, which is also required for the assembly of functional flagella. In addition to previously identified binding sites at the N-terminal and central segment of the TLR5 ectodomain, we extended the TLR5'-D1 interaction interface on TLR5 and showed a species-specific recognition relevance of this extended region. In addition, we showed that the loop and following β-hairpin region of flagellin, previously proposed to participate in the TLR5-flagellin dimerization interface, is not accountable for these species-specific differences. We further identified residues that contribute to the interaction between two TLR5 ectodomains in an active signaling complex. Our work demonstrates that flagellin is recognized by TLR5 through a more extensive interaction surface than previously characterized.
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Benčina M, Mori J, Gaber R, Jerala R. Metabolic Channeling Using DNA as a Scaffold. Synth Biol (Oxf) 2018. [DOI: 10.1002/9783527688104.ch12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Facchini FA, Zaffaroni L, Minotti A, Rapisarda S, Calabrese V, Forcella M, Fusi P, Airoldi C, Ciaramelli C, Billod JM, Schromm AB, Braun H, Palmer C, Beyaert R, Lapenta F, Jerala R, Pirianov G, Martin-Santamaria S, Peri F. Structure-Activity Relationship in Monosaccharide-Based Toll-Like Receptor 4 (TLR4) Antagonists. J Med Chem 2018; 61:2895-2909. [PMID: 29494148 DOI: 10.1021/acs.jmedchem.7b01803] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The structure-activity relationship was investigated in a series of synthetic TLR4 antagonists formed by a glucosamine core linked to two phosphate esters and two linear carbon chains. Molecular modeling showed that the compounds with 10, 12, and 14 carbons chains are associated with higher stabilization of the MD-2/TLR4 antagonist conformation than in the case of the C16 variant. Binding experiments with human MD-2 showed that the C12 and C14 variants have higher affinity than C10, while the C16 variant did not interact with the protein. The molecules, with the exception of the C16 variant, inhibited the LPS-stimulated TLR4 signal in human and murine cells, and the antagonist potency mirrored the MD-2 affinity calculated from in vitro binding experiments. Fourier-transform infrared, nuclear magnetic resonance, and small angle X-ray scattering measurements suggested that the aggregation state in aqueous solution depends on fatty acid chain lengths and that this property can influence TLR4 activity in this series of compounds.
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Murovec J, Guček K, Bohanec B, Avbelj M, Jerala R. DNA-Free Genome Editing of Brassica oleracea and B. rapa Protoplasts Using CRISPR-Cas9 Ribonucleoprotein Complexes. FRONTIERS IN PLANT SCIENCE 2018; 9:1594. [PMID: 30455712 PMCID: PMC6230560 DOI: 10.3389/fpls.2018.01594] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 10/15/2018] [Indexed: 05/22/2023]
Abstract
The CRISPR/Cas9 genome editing system has already proved its efficiency, versatility and simplicity in numerous applications in human, animal, microbe and plant cells. Together with the vast amount of genome and transcriptome databases available, it represents an enormous potential for plant breeding and research. Although most changes produced with CRISPR/Cas9 do not differ from naturally occurring mutations, the use of transgenesis during varietal development can still trigger GMO legislation in countries that rely on process-based regulation. Moreover, stable integration of DNA coding for genome-editing tools into plant genomes can result in insertional mutagenesis, while its prolonged expression can cause mutations in off-target sites. These pitfalls can be avoided with the delivery of preassembled ribonucleoprotein complexes (RNPs) composed of purified recombinant enzyme Cas9 and in vitro-transcribed or synthesized sgRNA. We therefore aimed to develop a DNA-free protocol for site-directed mutagenesis of three species of the genus Brassica (B. oleracea, B. napus, and B. rapa) with the use of RNPs. We chose cabbage, rapeseed and Chinese cabbage as species representatives and introduced RNPs into their protoplasts with PEG 4000. Four sgRNAs targeting two endogenous genes (the FRI and PDS genes, two sgRNAs per gene) were introduced into all three species. No mutations were detected after transfection of rapeseed protoplasts, while we obtained mutation frequencies of 0.09 to 2.25% and 1.15 to 24.51% in cabbage and Chinese cabbage, respectively. In both species, a positive correlation was displayed between the amount (7.5, 15, 30, and 60 μg) of Cas9 enzyme and sgRNA introduced and mutation frequency. Nucleotide changes (insertions and deletions) were detected 24 h after transfection and did not differ 72 h after transfection. They were species-, gene- and locus-dependent. In summary, we demonstrated the suitability of RNP transfection into B. oleracea and B. rapa protoplasts for high-efficiency indel induction of two endogenous genes. Due to the relatively high mutation frequencies detected (up to 24.51%), this study paves the way for regeneration of precisely mutated Brassica plants without the use of transgenesis.
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Lapenta F, Aupič J, Strmšek Ž, Jerala R. Coiled coil protein origami: from modular design principles towards biotechnological applications. Chem Soc Rev 2018; 47:3530-3542. [DOI: 10.1039/c7cs00822h] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This review illustrates the current state in designing coiled-coil-based proteins with an emphasis on coiled coil protein origami structures and their potential.
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Lebar T, Jerala R. Designed Transcriptional Regulation in Mammalian Cells Based on TALE- and CRISPR/dCas9. Methods Mol Biol 2018; 1772:191-203. [PMID: 29754229 DOI: 10.1007/978-1-4939-7795-6_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Transcriptional regulation lies at the center of many cellular processes and is the result of cellular response to different external and internal signals. Control of transcription of selected genes enables an unprecedented access to shape the cellular response. While orthogonal transcription factors from bacteria, yeast, plants, or other cells have been used to introduce new cellular logic into mammalian cells, the discovery of designable modular DNA binding domains, such as Transcription Activator-Like Effectors (TALEs) and the CRISPR system, enable targeting of almost any selected DNA sequence. Fusion or conditional association of DNA targeting domain with transcriptional effector domains enables controlled regulation of almost any endogenous or ectopic gene. Moreover, the designed regulators can be linked into genetic circuits to implement complex responses, such as different types of Boolean functions and switches. In this chapter, we describe the protocols for achieving efficient transcriptional regulation with TALE- and CRISPR-based designed transcription factors in mammalian cells.
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Lonzaric J, Fink T, Jerala R. Design and applications of synthetic information processing circuits in mammalian cells. Synth Biol (Oxf) 2017. [DOI: 10.1039/9781782622789-00001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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67
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Drobnak I, Ljubetič A, Gradišar H, Pisanski T, Jerala R. Designed Protein Origami. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 940:7-27. [PMID: 27677507 DOI: 10.1007/978-3-319-39196-0_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Proteins are highly perfected natural molecular machines, owing their properties to the complex tertiary structures with precise spatial positioning of different functional groups that have been honed through millennia of evolutionary selection. The prospects of designing new molecular machines and structural scaffolds beyond the limits of natural proteins make design of new protein folds a very attractive prospect. However, de novo design of new protein folds based on optimization of multiple cooperative interactions is very demanding. As a new alternative approach to design new protein folds unseen in nature, folds can be designed as a mathematical graph, by the self-assembly of interacting polypeptide modules within the single chain. Orthogonal coiled-coil dimers seem like an ideal building module due to their shape, adjustable length, and above all their designability. Similar to the approach of DNA nanotechnology, where complex tertiary structures are designed from complementary nucleotide segments, a polypeptide chain composed of a precisely specified sequence of coiled-coil forming segments can be designed to self-assemble into polyhedral scaffolds. This modular approach encompasses long-range interactions that define complex tertiary structures. We envision that by expansion of the toolkit of building blocks and design strategies of the folding pathways protein origami technology will be able to construct diverse molecular machines.
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Ljubetič A, Lapenta F, Gradišar H, Drobnak I, Aupič J, Strmšek Ž, Lainšček D, Hafner-Bratkovič I, Majerle A, Krivec N, Benčina M, Pisanski T, Veličković TĆ, Round A, Carazo JM, Melero R, Jerala R. Design of coiled-coil protein-origami cages that self-assemble in vitro and in vivo. Nat Biotechnol 2017; 35:1094-1101. [DOI: 10.1038/nbt.3994] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 09/25/2017] [Indexed: 12/13/2022]
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Forstnerič V, Ivičak-Kocjan K, Plaper T, Jerala R, Benčina M. The role of the C-terminal D0 domain of flagellin in activation of Toll like receptor 5. PLoS Pathog 2017; 13:e1006574. [PMID: 28827825 PMCID: PMC5578693 DOI: 10.1371/journal.ppat.1006574] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 08/31/2017] [Accepted: 08/09/2017] [Indexed: 11/19/2022] Open
Abstract
Flagellin is a wide-spread bacterial virulence factor sensed by the membrane-bound Toll-like receptor 5 (TLR5) and by the intracellular NAIP5/NLRC4 inflammasome receptor. TLR5 recognizes a conserved region within the D1 domain of flagellin, crucial for the interaction between subunits in the flagellum and for bacterial motility. While it is known that a deletion of the D0 domain of flagellin, which lines the interior of flagella, also completely abrogates activation of TLR5, its functional role remains unknown. Using a protein fusion strategy, we propose a role for the D0 domain in the stabilization of an active dimeric signaling complex of flagellin-TLR5 at a 2:2 stoichiometric ratio. Alanine-scanning mutagenesis of flagellin revealed a previously unidentified region of flagellin, the C-terminal D0 domain, to play a crucial role in TLR5 activation. Interestingly, we show that TLR5 recognizes the same hydrophobic motif of the D0 domain of flagellin as the intracellular NAIP5/NLRC4 inflammasome receptor. Further, we show that residues within the D0 domain play a previously unrecognized role in the evasion of TLR5 recognition by Helicobacter pylori. These findings demonstrate that TLR5 is able to simultaneously sense several spatially separated sites of flagellin that are essential for its functionality, hindering bacterial evasion of immune recognition. Our findings significantly contribute to the understanding of the mechanism of TLR5 activation, which plays an important role in host defense against several pathogens, but also in several diseases, such as Crohn’s disease, cystic fibrosis and rheumatoid arthritis. Receptors of the innate immune system typically recognize conserved microbial patterns, crucial for pathogen fitness and survival. Flagellin, the main structural protein of bacterial flagella, is recognized by two receptors of the innate immune system, the intracellular inflammasome receptor NAIP5/NLRC4 and the membrane-bound Toll-like receptor 5. Ligand-induced dimerization is a crucial step in Toll-like receptor 5 activation. A crystal structure of segments of the ligand-bound receptor revealed binding interfaces on the ligand and receptor, but failed to fully clarify the activation mechanism, since the D0 domain of flagellin, which is crucial for receptor activation, is missing in the structure. We propose a role for the D0 domain in receptor dimerization and pinpoint specific amino-acid residues within the D0 domain, which contribute to Toll-like receptor 5 activation. We show that Toll-like receptor 5 recognizes the same protein motif detected by the intracellular NAIP5/NLRC4 receptor. Our work represents an important advance in the understanding of the mechanism of activation of Toll-like receptor 5.
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Drobnak I, Gradišar H, Ljubetič A, Merljak E, Jerala R. Modulation of Coiled-Coil Dimer Stability through Surface Residues while Preserving Pairing Specificity. J Am Chem Soc 2017; 139:8229-8236. [PMID: 28553984 DOI: 10.1021/jacs.7b01690] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The coiled-coil dimer is a widespread protein structural motif and, due to its designability, represents an attractive building block for assembling modular nanostructures. The specificity of coiled-coil dimer pairing is mainly based on hydrophobic and electrostatic interactions between residues at positions a, d, e, and g of the heptad repeat. Binding affinity, on the other hand, can also be affected by surface residues that face away from the dimerization interface. Here we show how design of the local helical propensity of interacting peptides can be used to tune the stabilities of coiled-coil dimers over a wide range. By designing intramolecular charge pairs, regions of high local helical propensity can be engineered to form trigger sequences, and dimer stability is adjusted without changing the peptide length or any of the directly interacting residues. This general principle is demonstrated by a change in thermal stability by more than 30 °C as a result of only two mutations outside the binding interface. The same approach was successfully used to modulate the stabilities in an orthogonal set of coiled-coils without affecting their binding preferences. The stability effects of local helical propensity and peptide charge are well described by a simple linear model, which should help improve current coiled-coil stability prediction algorithms. Our findings enable tuning the stabilities of coiled-coil-based building modules match a diverse range of applications in synthetic biology and nanomaterials.
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Pirher N, Pohar J, Manček-Keber M, Benčina M, Jerala R. Activation of cell membrane-localized Toll-like receptor 3 by siRNA. Immunol Lett 2017; 189:55-63. [PMID: 28392198 DOI: 10.1016/j.imlet.2017.03.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 03/30/2017] [Indexed: 11/25/2022]
Abstract
Small interfering RNA molecules (siRNA) are short dsRNAs that are used for different therapeutic applications. On the other hand, dsRNAs can bind to and activate cell RNA sensors and consequently trigger inflammatory response. Here we show that siRNA activates primary human endothelial cells and human lymphatic endothelial cells and that this response is inhibited by antibodies against TLR3. In contrast, the activation of human lymphatic endothelial cells by poly(I:C) was inhibited by bafilomycin but not by anti-TLR3 antibodies. Bafilomycin also inhibited poly(I:C) but not siRNA cell stimulation in TLR3-transfected HEK293. The response to siRNA required the expression of UNC93B1, which directs TLR3 to the surface of HEK293 cells. We propose that the engaged signaling pathway of TLR3 depends on the receptor localization and on the length of the dsRNA, where the activation of cell membrane TLR3 by short dsRNA leads to a predominantly proinflammatory response, whereas TLR3 activation in endosomal compartments by long dsRNA is characterized by the production of type I IFN. A molecular model suggests that the siRNA can bind to the binding sites of the TLR3 ectodomain and trigger receptor dimerization. These results contribute to understanding of the mechanism of side effects seen in the therapeutic application of naked, unmodified siRNA as a result of the activation of TLR3 localized at the plasma membrane.
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Pohar J, Yamamoto C, Fukui R, Cajnko MM, Miyake K, Jerala R, Benčina M. Selectivity of Human TLR9 for Double CpG Motifs and Implications for the Recognition of Genomic DNA. THE JOURNAL OF IMMUNOLOGY 2017; 198:2093-2104. [PMID: 28115525 DOI: 10.4049/jimmunol.1600757] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 12/19/2016] [Indexed: 12/18/2022]
Abstract
TLR9 acts as a first-line host defense against pathogens recognizing DNA comprising unmethylated CpG motifs present in bacteria and viruses. Species- and sequence-specific recognition differences were demonstrated for TLR9 receptors. Activation of human (h)TLR9 requires a pair of closely positioned CpG motifs within oligodeoxyribonucleotides (ODNs), whereas mouse TLR9 is effectively activated by an ODN with a single CpG motif. Molecular model-directed mutagenesis identified two regions, site A and site B, as important for receptor activation. Amino acid residues Gln346 and Arg348 within site A contribute to the sequence-specific recognition by hTLR9 in determining the bias for two appropriately spaced CpG motifs within immunostimulatory ODNs. Mutation of Gln562 at site B, in combination with Gln346 and Arg348 mutations of mouse counterparts, increased activation of hTLR9 by mouse-specific ODN, mammalian genomic DNA, and bacterial DNA. We propose that the double CpG motif sequence-specificity of hTLR9 results in decreased activation by ODNs with a lower frequency of CpG motifs, such as from mammalian genomic DNA, which increases hTLR9 selectivity for pathogen versus host DNA.
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Smole A, Lainšček D, Bezeljak U, Horvat S, Jerala R. A Synthetic Mammalian Therapeutic Gene Circuit for Sensing and Suppressing Inflammation. Mol Ther 2017; 25:102-119. [PMID: 28129106 DOI: 10.1016/j.ymthe.2016.10.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 10/20/2016] [Accepted: 10/21/2016] [Indexed: 12/20/2022] Open
Abstract
Inflammation, which is a highly regulated host response against danger signals, may be harmful if it is excessive and deregulated. Ideally, anti-inflammatory therapy should autonomously commence as soon as possible after the onset of inflammation, should be controllable by a physician, and should not systemically block beneficial immune response in the long term. We describe a genetically encoded anti-inflammatory mammalian cell device based on a modular engineered genetic circuit comprising a sensor, an amplifier, a "thresholder" to restrict activation of a positive-feedback loop, a combination of advanced clinically used biopharmaceutical proteins, and orthogonal regulatory elements that linked modules into the functional device. This genetic circuit was autonomously activated by inflammatory signals, including endogenous cecal ligation and puncture (CLP)-induced inflammation in mice and serum from a systemic juvenile idiopathic arthritis (sIJA) patient, and could be reset externally by a chemical signal. The microencapsulated anti-inflammatory device significantly reduced the pathology in dextran sodium sulfate (DSS)-induced acute murine colitis, demonstrating a synthetic immunological approach for autonomous anti-inflammatory therapy.
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Lebar T, Jerala R. Benchmarking of TALE- and CRISPR/dCas9-Based Transcriptional Regulators in Mammalian Cells for the Construction of Synthetic Genetic Circuits. ACS Synth Biol 2016; 5:1050-1058. [PMID: 27344932 DOI: 10.1021/acssynbio.5b00259] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Transcriptional activator-like effector (TALE)- and CRISPR/Cas9-based designable recognition domains represent a technological breakthrough not only for genome editing but also for building designed genetic circuits. Both platforms are able to target rarely occurring DNA segments, even within complex genomes. TALE and dCas9 domains, genetically fused to transcriptional regulatory domains, can be used for the construction of engineered logic circuits. Here we benchmarked the performance of the two platforms, targeting the same DNA sequences, to compare their advantages for the construction of designed circuits in mammalian cells. Optimal targeting strands for repression and activation of dCas9-based designed transcription factors were identified; both platforms exhibited good orthogonality and were used to construct functionally complete NOR gates. Although the CRISPR/dCas9 system is clearly easier to construct, TALE-based activators were significantly stronger, and the TALE-based platform performed better, especially for the construction of layered circuits.
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Forstnerič V, Ivičak-Kocjan K, Ljubetič A, Jerala R, Benčina M. Distinctive Recognition of Flagellin by Human and Mouse Toll-Like Receptor 5. PLoS One 2016; 11:e0158894. [PMID: 27391968 PMCID: PMC4938411 DOI: 10.1371/journal.pone.0158894] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 06/22/2016] [Indexed: 11/23/2022] Open
Abstract
Toll-like receptor 5 (TLR5) is a receptor of the innate immune system that recognizes flagellin from certain bacterial species and triggers an inflammatory response. The Salmonella dublin flagellin in complex with zebrafish TLR5 has been crystallized previously. In the present study, we extrapolate the structure of this complex using structure-guided mutagenesis to determine the recognition modes of human and mouse TLR5 receptors and demonstrate species-specific differences in flagellin recognition. In general, the recognition mode of the mouse receptor can be said to be more robust in comparison to that of the human receptor. All-atom molecular dynamics simulation showed differences between the two receptors within the primary binding region. Using a functional motility assay, we show that although the highly conserved area of the flagellin analyzed in this study encompasses key structural requirements for flagella formation, a direct correlation between immune recognition and structure on the level of amino acid residues is not observed.
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