1
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Joshi O, Skóra T, Yarema A, Rabbitt RD, Bidone TC. Contributions of the individual domains of α IIbβ 3 integrin to its extension: Insights from multiscale modeling. Cytoskeleton (Hoboken) 2024; 81:393-408. [PMID: 38682753 PMCID: PMC11333186 DOI: 10.1002/cm.21865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 04/09/2024] [Accepted: 04/10/2024] [Indexed: 05/01/2024]
Abstract
The platelet integrin αIIbβ3 undergoes long-range conformational transitions between bent and extended conformations to regulate platelet aggregation during hemostasis and thrombosis. However, how exactly αIIbβ3 transitions between conformations remains largely elusive. Here, we studied how transitions across bent and extended-closed conformations of αIIbβ3 integrin are regulated by effective interactions between its functional domains. We first carried out μs-long equilibrium molecular dynamics (MD) simulations of full-length αIIbβ3 integrins in bent and intermediate conformations, the latter characterized by an extended headpiece and closed legs. Then, we built heterogeneous elastic network models, perturbed inter-domain interactions, and evaluated their relative contributions to the energy barriers between conformations. Results showed that integrin extension emerges from: (i) changes in interfaces between functional domains; (ii) allosteric coupling of the head and upper leg domains with flexible lower leg domains. Collectively, these results provide new insights into integrin conformational activation based on short- and long-range interactions between its functional domains and highlight the importance of the lower legs in the regulation of integrin allostery.
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Affiliation(s)
- Onkar Joshi
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah, USA
| | - Tomasz Skóra
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah, USA
| | - Anna Yarema
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA
| | - Richard D Rabbitt
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA
| | - Tamara C Bidone
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah, USA
- Department of Molecular Pharmaceutics, University of Utah, Salt Lake City, Utah, USA
- Department of Biochemistry, University of Utah, Salt Lake City, Utah, USA
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2
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Li Z. A molecular arm: the molecular bending-unbending mechanism of integrin. Biomech Model Mechanobiol 2024; 23:781-792. [PMID: 38308770 DOI: 10.1007/s10237-023-01805-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 12/13/2023] [Indexed: 02/05/2024]
Abstract
The balance of integrin activation and deactivation regulates its function and mediates cell behaviors. Mechanical force triggers the unbending and activation of integrin. However, how an activated and extended integrin spontaneously bends back is unclear. I performed all-atom molecular dynamics simulations on an integrin or its subunits to reveal the bending-unbending mechanism of integrin. According to the simulations, the integrin structure works like a human arm. The integrin α subunit serves as the bones, while the β leg serves as the bicep. The integrin extension results in the stretching of the β leg, and the extended integrin spontaneously bends as a consequence of the contraction of the β leg. This study provides new insights into the mechanism of how the integrin secures in the bent inactivated state and sheds light on how the integrin could achieve a stable extended state.
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Affiliation(s)
- Zhenhai Li
- Shanghai Institute of Applied Mathematics and Mechanics, Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Frontier Science Center of Mechanoinformatics, School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200072, China.
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3
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Koy C, Röwer C, Thiesen HJ, Neamtu A, Glocker MO. Intact Transition Epitope Mapping-Force Interferences by Variable Extensions (ITEM-FIVE). Biomolecules 2024; 14:454. [PMID: 38672470 PMCID: PMC11048379 DOI: 10.3390/biom14040454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 04/28/2024] Open
Abstract
Investigations on binding strength differences of non-covalent protein complex components were performed by mass spectrometry. T4 fibritin foldon (T4Ff) is a well-studied miniprotein, which together with its biotinylated version served as model system to represent a compactly folded protein to which an Intrinsically Disordered Region (IDR) was attached. The apparent enthalpies of the gas phase dissociation reactions of the homo-trimeric foldon F-F-F and of the homo-trimeric triply biotinylated foldon bF-bF-bF have been determined to be rather similar (3.32 kJ/mol and 3.85 kJ/mol) but quite distinct from those of the singly and doubly biotinylated hetero-trimers F-F-bF and F-bF-bF (1.86 kJ/mol and 1.08 kJ/mol). Molecular dynamics simulations suggest that the ground states of the (biotinylated) T4Ff trimers are highly symmetric and well comparable to each other, indicating that the energy levels of all four (biotinylated) T4Ff trimer ground states are nearly indistinguishable. The experimentally determined differences and/or similarities in enthalpies of the complex dissociation reactions are explained by entropic spring effects, which are noticeable in the T4Ff hetero-trimers but not in the T4Ff homo-trimers. A lowering of the transition state energy levels of the T4Ff hetero-trimers seems likely because the biotin moieties, mimicking intrinsically disordered regions (IDRs), induced asymmetries in the transition states of the biotinylated T4Ff hetero-trimers. This transition state energy level lowering effect is absent in the T4Ff homo-trimer, as well as in the triply biotinylated T4Ff homo-trimer. In the latter, the IDR-associated entropic spring effects on complex stability cancel each other out. ITEM-FIVE enabled semi-quantitative determination of energy differences of complex dissociation reactions, whose differences were modulated by IDRs attached to compactly folded proteins.
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Affiliation(s)
- Cornelia Koy
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock Schillingallee 69, 18057 Rostock, Germany; (C.K.)
| | - Claudia Röwer
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock Schillingallee 69, 18057 Rostock, Germany; (C.K.)
| | - Hans-Jürgen Thiesen
- Institute for Immunology, Medical Faculty, University of Rostock, Schillingallee 70, 18057 Rostock, Germany;
| | - Andrei Neamtu
- Department of Physiology, “Gr. T. Popa” University of Medicine and Pharmacy, Str. Universitatii nr. 16, 700115 Iasi, Romania
- TRANSCEND Centre, Regional Institute of Oncology (IRO) Iasi, Str. General Henri Mathias Berthelot, Nr. 2–4, 700483 Iasi, Romania
| | - Michael O. Glocker
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock Schillingallee 69, 18057 Rostock, Germany; (C.K.)
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4
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Zhang H, Zhu DS, Zhu J. Family-wide analysis of integrin structures predicted by AlphaFold2. Comput Struct Biotechnol J 2023; 21:4497-4507. [PMID: 37753178 PMCID: PMC10518446 DOI: 10.1016/j.csbj.2023.09.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/17/2023] [Accepted: 09/17/2023] [Indexed: 09/28/2023] Open
Abstract
Recent advances in protein structure prediction using AlphaFold2, known for its high efficiency and accuracy, have opened new avenues for comprehensive analysis of all structures within a single protein family. In this study, we evaluated the capabilities of AphaFold2 in analyzing integrin structures. Integrins are heterodimeric cell surface receptors composed of a combination of 18 α and 8 β subunits, resulting in a family of 24 different members. Both α and β subunits consist of a large extracellular domain, a short transmembrane domain, and typically, a short cytoplasmic tail. Integrins play a pivotal role in a wide range of cellular functions by recognizing diverse ligands. Despite significant advances in integrin structural studies in recent decades, high-resolution structures have only been determined for a limited subsets of integrin members, thus limiting our understanding of the entire integrin family. Here, we first analyzed the single-chain structures of 18 α and 8 β integrins in the AlphaFold2 protein structure database. We then employed the newly developed AlphaFold2-multimer program to predict the α/β heterodimer structures of all 24 human integrins. The predicted structures show a high level of accuracy for the subdomains of both α and β subunits, offering high-resolution structure insights for all integrin heterodimers. Our comprehensive structural analysis of the entire integrin family unveils a potentially diverse range of conformations among the 24 members, providing a valuable structure database for studies related to integrin structure and function. We further discussed the potential applications and limitations of the AlphaFold2-derived integrin structures.
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Affiliation(s)
- Heng Zhang
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Daniel S. Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Jieqing Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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5
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Zhang H, Zhu DS, Zhu J. Family-wide analysis of integrin structures predicted by AlphaFold2. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.02.539023. [PMID: 37205578 PMCID: PMC10187181 DOI: 10.1101/2023.05.02.539023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Recent advances in protein structure prediction using AlphaFold2, known for its high efficiency and accuracy, have opened new avenues for comprehensive analysis of all structures within a single protein family. In this study, we evaluated the capabilities of AphaFold2 in analyzing integrin structures. Integrins are heterodimeric cell surface receptors composed of a combination of 18 α and 8 β subunits, resulting in a family of 24 different members. Both α and β subunits consist of a large extracellular domain, a short transmembrane domain, and typically, a short cytoplasmic tail. Integrins play a pivotal role in a wide range of cellular functions by recognizing diverse ligands. Despite significant advances in integrin structural studies in recent decades, high-resolution structures have only been determined for a limited subsets of integrin members, thus limiting our understanding of the entire integrin family. Here, we first analyzed the single-chain structures of 18 α and 8 β integrins in the AlphaFold2 protein structure database. We then employed the newly developed AlphaFold2-multimer program to predict the α/β heterodimer structures of all 24 human integrins. The predicted structures show a high level of accuracy for the subdomains of both α and β subunits, offering high-resolution structure insights for all integrin heterodimers. Our comprehensive structural analysis of the entire integrin family unveils a potentially diverse range of conformations among the 24 members, providing a valuable structure database for studies related to integrin structure and function. We further discussed the potential applications and limitations of the AlphaFold2-derived integrin structures.
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Affiliation(s)
- Heng Zhang
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Daniel S. Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Jieqing Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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6
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Chen Y, Kong F, Li Z, Ju LA, Zhu C. Force-regulated spontaneous conformational changes of integrins α 5 β 1 and α V β 3. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.523308. [PMID: 36712101 PMCID: PMC9881988 DOI: 10.1101/2023.01.09.523308] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Force can modulate the properties and functions of macromolecules by inducing conformational changes, such as coiling/uncoiling, zipping/unzipping, and folding/unfolding. Here we compared force-modulated bending/unbending of two purified integrin ectodomains, α 5 β 1 and α V β 3 , using single-molecule approaches. Similar to previously characterized mechano-sensitive macromolecules, the conformation of α 5 β 1 is determined by a threshold head-to-tail tension, suggesting a canonical energy landscape with a deep energy well that traps the integrin in the bent state until sufficient force tilts the energy landscape to accelerate transition to the extended state. By comparison, α V β 3 exhibits bi-stability even without force and can spontaneously transition between the bent and extended conformations in a wide range of forces without energy supplies. Molecular dynamics simulations revealed consecutive formation and disruption of 7 hydrogen bonds during α V β 3 bending and unbending, respectively. Accordingly, we constructed an energy landscape with hexa-stable intermediate states to break down the energy barrier separating the bent and extended states into smaller ones, making it possible for the thermal agitation energy to overcome them sequentially and to be accumulated and converted into mechanical work required for α V β 3 to bend against force. Our study elucidates the different inner workings of α 5 β 1 and α V β 3 at the sub-molecular level, sheds lights on how their respectively functions are facilitated by their distinctive mechano-sensitivities, helps understand their signal initiation processes, and provides critical concepts and useful design principles for engineering of protein-based biomechanical nanomachines.
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7
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Integrin Conformational Dynamics and Mechanotransduction. Cells 2022; 11:cells11223584. [PMID: 36429013 PMCID: PMC9688440 DOI: 10.3390/cells11223584] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/04/2022] [Accepted: 11/10/2022] [Indexed: 11/16/2022] Open
Abstract
The function of the integrin family of receptors as central mediators of cell-extracellular matrix (ECM) and cell-cell adhesion requires a remarkable convergence of interactions and influences. Integrins must be anchored to the cytoskeleton and bound to extracellular ligands in order to provide firm adhesion, with force transmission across this linkage conferring tissue integrity. Integrin affinity to ligands is highly regulated by cell signaling pathways, altering affinity constants by 1000-fold or more, via a series of long-range conformational transitions. In this review, we first summarize basic, well-known features of integrin conformational states and then focus on new information concerning the impact of mechanical forces on these states and interstate transitions. We also discuss how these effects may impact mechansensitive cell functions and identify unanswered questions for future studies.
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8
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Zhou D, Thinn AMM, Zhao Y, Wang Z, Zhu J. Structure of an extended β 3 integrin. Blood 2018; 132:962-972. [PMID: 30018079 PMCID: PMC6117741 DOI: 10.1182/blood-2018-01-829572] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 07/10/2018] [Indexed: 12/23/2022] Open
Abstract
Cells use adhesion receptor integrins to communicate with their surroundings. Integrin activation and cellular signaling are coupled with change from bent to extended conformation. β3 integrins, including αIIbβ3, which is essential for the function of platelets in hemostasis and thrombosis, and αVβ3, which plays multiple roles in diverse cell types, have been prototypes in understanding integrin structure and function. Despite extensive structural studies, a high-resolution integrin structure in an extended conformation remains to be determined. The human β3 Leu33Pro polymorphism, located at the PSI domain, defines human platelet-specific alloantigens 1a and 1b (HPA-1a/b), immune response to which is a cause of posttransfusion purpura and fetal/neonatal alloimmune thrombocytopenia. Leu33Pro substitution has also been suggested to be a risk factor for thrombosis. Here we report the crystal structure of the β3 headpiece in either Leu33 or Pro33 form, both of which reveal intermediate and fully extended conformations coexisting in 1 crystal. These were used to build high-resolution structures of full-length β3 integrin in the intermediate and fully extended states, agreeing well with the corresponding conformations observed by electron microscopy. Our structures reveal how β3 integrin becomes extended at its β-knee region and how the flexibility of β-leg domains is determined. In addition, our structures reveal conformational changes of the PSI and I-EGF1 domains upon β3 extension, which may affect the binding of conformation-dependent anti-HPA-1a alloantibodies. Our structural and functional data show that Leu33Pro substitution does not directly alter the conformation or ligand binding of β3 integrin.
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Affiliation(s)
- Dongwen Zhou
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
| | - Aye Myat Myat Thinn
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI; and
| | - Yan Zhao
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
- Department of Physiology, School of Basic Medical Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Zhengli Wang
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
| | - Jieqing Zhu
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI; and
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9
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Cryo-EM structure of the αvβ8 integrin reveals a mechanism for stabilizing integrin extension. Nat Struct Mol Biol 2018; 25:698-704. [PMID: 30061598 PMCID: PMC6214843 DOI: 10.1038/s41594-018-0093-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 06/21/2018] [Indexed: 01/06/2023]
Abstract
Integrins are conformationally flexible cell surface receptors that survey the extracellular environment for their cognate ligands. Interactions with ligands are thought to be linked to global structural rearrangements involving transitions between bent, extended-closed and -open forms. Thus far, structural details are lacking for integrins in the extended conformation due to extensive flexibility between the headpiece and legs within this conformation. Here we present single-particle electron cryo-microscopy structures of human αvβ8 integrin in the extended-closed conformation, which has been considered to be a low-affinity intermediate. Our structures show the headpiece rotating about a flexible αv-knee, suggesting a ligand surveillance mechanism for integrins in their extended-closed form. Our model predicts that the extended conformation is mainly stabilized by an interface formed between flexible loops in the upper and lower domains of the αv-leg. Confirming these findings with the αvβ3 integrin suggests that our model of stabilizing the extended-closed conformation is generalizable to other integrins.
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10
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Afanasyeva A, Bockwoldt M, Cooney CR, Heiland I, Gossmann TI. Human long intrinsically disordered protein regions are frequent targets of positive selection. Genome Res 2018; 28:975-982. [PMID: 29858274 PMCID: PMC6028134 DOI: 10.1101/gr.232645.117] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 06/01/2018] [Indexed: 12/20/2022]
Abstract
Intrinsically disordered regions occur frequently in proteins and are characterized by a lack of a well-defined three-dimensional structure. Although these regions do not show a higher order of structural organization, they are known to be functionally important. Disordered regions are rapidly evolving, largely attributed to relaxed purifying selection and an increased role of genetic drift. It has also been suggested that positive selection might contribute to their rapid diversification. However, for our own species, it is currently unknown whether positive selection has played a role during the evolution of these protein regions. Here, we address this question by investigating the evolutionary pattern of more than 6600 human proteins with intrinsically disordered regions and their ordered counterparts. Our comparative approach with data from more than 90 mammalian genomes uses a priori knowledge of disordered protein regions, and we show that this increases the power to detect positive selection by an order of magnitude. We can confirm that human intrinsically disordered regions evolve more rapidly, not only within humans but also across the entire mammalian phylogeny. They have, however, experienced substantial evolutionary constraint, hinting at their fundamental functional importance. We find compelling evidence that disordered protein regions are frequent targets of positive selection and estimate that the relative rate of adaptive substitutions differs fourfold between disordered and ordered protein regions in humans. Our results suggest that disordered protein regions are important targets of genetic innovation and that the contribution of positive selection in these regions is more pronounced than in other protein parts.
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Affiliation(s)
- Arina Afanasyeva
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S102TN, United Kingdom.,Institute of Nanobiotechnologies, Peter the Great St. Petersburg Polytechnic University, Saint-Petersburg 195251, Russia.,Petersburg Nuclear Physics Institute, B.P. Konstantinov NRC Kurchatov Institute, Gatchina, Leningrad District 188300, Russia.,National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki City, Osaka 567-0085, Japan
| | - Mathias Bockwoldt
- Department of Arctic and Marine Biology, UiT The Arctic University of Norway, 9037 Tromsø, Norway
| | - Christopher R Cooney
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S102TN, United Kingdom
| | - Ines Heiland
- Department of Arctic and Marine Biology, UiT The Arctic University of Norway, 9037 Tromsø, Norway
| | - Toni I Gossmann
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S102TN, United Kingdom
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11
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Pillois X, Peters P, Segers K, Nurden AT. In silico analysis of structural modifications in and around the integrin αIIb genu caused by ITGA2B variants in human platelets with emphasis on Glanzmann thrombasthenia. Mol Genet Genomic Med 2018; 6:249-260. [PMID: 29385657 PMCID: PMC5902390 DOI: 10.1002/mgg3.365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 12/01/2017] [Accepted: 12/20/2017] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Studies on the inherited bleeding disorder, Glanzmann thrombasthenia (GT), have helped define the role of the αIIbβ3 integrin in platelet aggregation. Stable bent αIIbβ3 undergoes conformation changes on activation allowing fibrinogen binding and its taking an extended form. The αIIb genu assures the fulcrum of the bent state. Our goal was to determine how structural changes induced by missense mutations in the αIIb genu define GT phenotype. METHODS Sanger sequencing of ITGA2B and ITGB3 in the index case followed by in silico modeling of all known GT-causing missense mutations extending from the lower part of the β-propeller, and through the thigh and upper calf-1 domains. RESULTS A homozygous c.1772A>C transversion in exon 18 of ITGA2B coding for a p.Asp591Ala substitution in an interconnecting loop of the lower thigh domain of αIIb in a patient with platelets lacking αIIbβ3 led us to extend our in silico modeling to all 16 published disease-causing missense variants potentially affecting the αIIb genu. Modifications of structuring H-bonding were the major cause in the thigh domain although one mutation gave mRNA decay. In contrast, short-range changes induced in calf-1 appeared minor suggesting long-range effects. All result in severe to total loss of αIIbβ3 in platelets. The absence of mutations within a key Ca2+-binding loop in the genu led us to scan public databases; three potential single allele variants giving major structural changes were identiffied suggesting that this key region is not protected from genetic variation. CONCLUSIONS It appears that the αIIb genu is the object of stringent quality control to prevent platelets from circulating with activated and extended integrin.
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Affiliation(s)
- Xavier Pillois
- Institut de Rhythmologie et de Modélisation Cardiaque, Plateforme Technologique d'Innovation BiomédicaleHôpital Xavier ArnozanBordeauxFrance
- Université de BordeauxINSERM U1034BordeauxFrance
| | - Pierre Peters
- Laboratoire de Thrombose‐HémostaseService d'Hématologie biologique et Immuno‐HématologieCHU Sart TilmanLiègeBelgium
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12
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Bondu V, Wu C, Cao W, Simons PC, Gillette J, Zhu J, Erb L, Zhang XF, Buranda T. Low-affinity binding in cis to P2Y 2R mediates force-dependent integrin activation during hantavirus infection. Mol Biol Cell 2017; 28:2887-2903. [PMID: 28835374 PMCID: PMC5638590 DOI: 10.1091/mbc.e17-01-0082] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 08/08/2017] [Accepted: 08/17/2017] [Indexed: 12/22/2022] Open
Abstract
Atomic force microscopy is used to establish that low-affinity integrins bind in cis to P2Y2R. Integrin activation is initiated by a membrane-normal switchblade motion triggered by integrin priming after the virus binds to the integrin PSI domain. Tensile force between the P2Y2R and unbending integrin stimulates outside-in signaling. Pathogenic hantaviruses bind to the plexin-semaphorin-integrin (PSI) domain of inactive, β3 integrins. Previous studies have implicated a cognate cis interaction between the bent conformation β5/β3 integrins and an arginine-glycine-aspartic acid (RGD) sequence in the first extracellular loop of P2Y2R. With single-molecule atomic force microscopy, we show a specific interaction between an atomic force microscopy tip decorated with recombinant αIIbβ3 integrins and (RGD)P2Y2R expressed on cell membranes. Mutation of the RGD sequence to RGE in the P2Y2R removes this interaction. Binding of inactivated and fluorescently labeled Sin Nombre virus (SNV) to the integrin PSI domain stimulates higher affinity for (RGD)P2Y2R on cells, as measured by an increase in the unbinding force. In CHO cells, stably expressing αIIbβ3 integrins, virus engagement at the integrin PSI domain, recapitulates physiologic activation of the integrin as indicated by staining with the activation-specific mAB PAC1. The data also show that blocking of the Gα13 protein from binding to the cytoplasmic domain of the β3 integrin prevents outside-in signaling and infection. We propose that the cis interaction with P2Y2R provides allosteric resistance to the membrane-normal motion associated with the switchblade model of integrin activation, where the development of tensile force yields physiological integrin activation.
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Affiliation(s)
- Virginie Bondu
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131
| | - Chenyu Wu
- Department of Mechanical Engineering and Mechanics and Department of Bioengineering, Lehigh University, Bethlehem, PA 18015
| | - Wenpeng Cao
- Department of Mechanical Engineering and Mechanics and Department of Bioengineering, Lehigh University, Bethlehem, PA 18015
| | - Peter C Simons
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131
| | - Jennifer Gillette
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131
| | - Jieqing Zhu
- Blood Research Institute, Bloodcenter of Wisconsin, Milwaukee, WI 53226
| | - Laurie Erb
- Department of Biochemistry, 540F Bond Life Sciences Center, Columbia, MO 65211
| | - X Frank Zhang
- Department of Mechanical Engineering and Mechanics and Department of Bioengineering, Lehigh University, Bethlehem, PA 18015
| | - Tione Buranda
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131 .,Center for Infectious Diseases and Immunity, University of New Mexico School of Medicine, Albuquerque, NM 87131
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13
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Zhu G, Saw WG, Nalaparaju A, Grüber G, Lu L. Coarse-Grained Molecular Modeling of the Solution Structure Ensemble of Dengue Virus Nonstructural Protein 5 with Small-Angle X-ray Scattering Intensity. J Phys Chem B 2017; 121:2252-2264. [DOI: 10.1021/acs.jpcb.7b00051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Guanhua Zhu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
| | - Wuan Geok Saw
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
| | - Anjaiah Nalaparaju
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
| | - Gerhard Grüber
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
| | - Lanyuan Lu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
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14
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Li J, Su Y, Xia W, Qin Y, Humphries MJ, Vestweber D, Cabañas C, Lu C, Springer TA. Conformational equilibria and intrinsic affinities define integrin activation. EMBO J 2017; 36:629-645. [PMID: 28122868 PMCID: PMC5331762 DOI: 10.15252/embj.201695803] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/12/2016] [Accepted: 12/15/2016] [Indexed: 11/25/2022] Open
Abstract
We show that the three conformational states of integrin α5β1 have discrete free energies and define activation by measuring intrinsic affinities for ligand of each state and the equilibria linking them. The 5,000-fold higher affinity of the extended-open state than the bent-closed and extended-closed states demonstrates profound regulation of affinity. Free energy requirements for activation are defined with protein fragments and intact α5β1 On the surface of K562 cells, α5β1 is 99.8% bent-closed. Stabilization of the bent conformation by integrin transmembrane and cytoplasmic domains must be overcome by cellular energy input to stabilize extension. Following extension, headpiece opening is energetically favored. N-glycans and leg domains in each subunit that connect the ligand-binding head to the membrane repel or crowd one another and regulate conformational equilibria in favor of headpiece opening. The results suggest new principles for regulating signaling in the large class of receptors built from extracellular domains in tandem with single-span transmembrane domains.
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Affiliation(s)
- Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Yang Su
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Wei Xia
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Yan Qin
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Martin J Humphries
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester, UK
| | | | - Carlos Cabañas
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM) and Departamento de Microbiología I Facultad de Medicina UCM, Madrid, Spain
| | - Chafen Lu
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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15
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Structural flexibility at a major conserved antibody target on hepatitis C virus E2 antigen. Proc Natl Acad Sci U S A 2016; 113:12768-12773. [PMID: 27791120 DOI: 10.1073/pnas.1609780113] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Hepatitis C virus (HCV) is a major cause of liver disease, affecting over 2% of the world's population. The HCV envelope glycoproteins E1 and E2 mediate viral entry, with E2 being the main target of neutralizing antibody responses. Structural investigations of E2 have produced templates for vaccine design, including the conserved CD81 receptor-binding site (CD81bs) that is a key target of broadly neutralizing antibodies (bNAbs). Unfortunately, immunization with recombinant E2 and E1E2 rarely elicits sufficient levels of bNAbs for protection. To understand the challenges for eliciting bNAb responses against the CD81bs, we investigated the E2 CD81bs by electron microscopy (EM), hydrogen-deuterium exchange (HDX), molecular dynamics (MD), and calorimetry. By EM, we observed that HCV1, a bNAb recognizing the N-terminal region of the CD81bs, bound a soluble E2 core construct from multiple angles of approach, suggesting components of the CD81bs are flexible. HDX of multiple E2 constructs consistently indicated the entire CD81bs was flexible relative to the rest of the E2 protein, which was further confirmed by MD simulations. However, E2 has a high melting temperature of 84.8 °C, which is more akin to proteins from thermophilic organisms. Thus, recombinant E2 is a highly stable protein overall, but with an exceptionally flexible CD81bs. Such flexibility may promote induction of nonneutralizing antibodies over bNAbs to E2 CD81bs, underscoring the necessity of rigidifying this antigenic region as a target for rational vaccine design.
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16
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Deller MC, Kong L, Rupp B. Protein stability: a crystallographer's perspective. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2016; 72:72-95. [PMID: 26841758 PMCID: PMC4741188 DOI: 10.1107/s2053230x15024619] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 12/21/2015] [Indexed: 12/18/2022]
Abstract
Protein stability is a topic of major interest for the biotechnology, pharmaceutical and food industries, in addition to being a daily consideration for academic researchers studying proteins. An understanding of protein stability is essential for optimizing the expression, purification, formulation, storage and structural studies of proteins. In this review, discussion will focus on factors affecting protein stability, on a somewhat practical level, particularly from the view of a protein crystallographer. The differences between protein conformational stability and protein compositional stability will be discussed, along with a brief introduction to key methods useful for analyzing protein stability. Finally, tactics for addressing protein-stability issues during protein expression, purification and crystallization will be discussed.
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Affiliation(s)
- Marc C Deller
- Stanford ChEM-H, Macromolecular Structure Knowledge Center, Stanford University, Shriram Center, 443 Via Ortega, Room 097, MC5082, Stanford, CA 94305-4125, USA
| | - Leopold Kong
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Building 8, Room 1A03, 8 Center Drive, Bethesda, MD 20814, USA
| | - Bernhard Rupp
- Department of Forensic Crystallography, k.-k. Hofkristallamt, 91 Audrey Place, Vista, CA 92084, USA
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17
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Terakawa T, Higo J, Takada S. Multi-scale ensemble modeling of modular proteins with intrinsically disordered linker regions: application to p53. Biophys J 2015; 107:721-729. [PMID: 25099811 DOI: 10.1016/j.bpj.2014.06.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 05/28/2014] [Accepted: 06/18/2014] [Indexed: 10/24/2022] Open
Abstract
In eukaryotic proteins, intrinsically disordered regions (IDRs) are ubiquitous and often exist in linker regions that flank the functional domains of modular proteins, regulating their functions. For detailed structural ensemble modeling of IDRs, we propose a multiscale method for IDRs that possess significant long-range order in modular proteins and apply it to the eukaryotic transcription factor p53 as an example. First, we performed all-atom (AA) molecular dynamics (MD) simulations of the explicitly solvated p53 linker region, without experimental restraint terms, finding fractional long-range contacts within the linker. Second, we fed this AA MD ensemble into a coarse-grained (CG) model, finding an optimal set of contact potentials. The optimized CG MD simulations reproduced the contact probability map from the AA MD simulations. Finally, we performed the CG MD simulation of the tetrameric p53 fragments including the core domains, the linker, and the tetramerization domain. Using the obtained ensemble, we theoretically calculated the small angle x-ray scattering (SAXS) profile of this fragment. The obtained SAXS profile agrees well with the experiment. We also found that the long-range contacts in the p53 linker region are required to reproduce the experimental SAXS profile. The developed framework in which we calculate the long-range contact probability map from the AA MD simulation and incorporate it to the CG model can be applied to broad range of IDRs.
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Affiliation(s)
- Tsuyoshi Terakawa
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo, Kyoto, 606-8502, Japan
| | - Junichi Higo
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo, Kyoto, 606-8502, Japan.
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18
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Varadi M, Vranken W, Guharoy M, Tompa P. Computational approaches for inferring the functions of intrinsically disordered proteins. Front Mol Biosci 2015; 2:45. [PMID: 26301226 PMCID: PMC4525029 DOI: 10.3389/fmolb.2015.00045] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/21/2015] [Indexed: 01/09/2023] Open
Abstract
Intrinsically disordered proteins (IDPs) are ubiquitously involved in cellular processes and often implicated in human pathological conditions. The critical biological roles of these proteins, despite not adopting a well-defined fold, encouraged structural biologists to revisit their views on the protein structure-function paradigm. Unfortunately, investigating the characteristics and describing the structural behavior of IDPs is far from trivial, and inferring the function(s) of a disordered protein region remains a major challenge. Computational methods have proven particularly relevant for studying IDPs: on the sequence level their dependence on distinct characteristics determined by the local amino acid context makes sequence-based prediction algorithms viable and reliable tools for large scale analyses, while on the structure level the in silico integration of fundamentally different experimental data types is essential to describe the behavior of a flexible protein chain. Here, we offer an overview of the latest developments and computational techniques that aim to uncover how protein function is connected to intrinsic disorder.
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Affiliation(s)
- Mihaly Varadi
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium
| | - Wim Vranken
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium ; ULB-VUB - Interuniversity Institute of Bioinformatics in Brussels (IB)2 Brussels, Belgium
| | - Mainak Guharoy
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium
| | - Peter Tompa
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium
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19
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Minagawa S, Lou J, Seed RI, Cormier A, Wu S, Cheng Y, Murray L, Tsui P, Connor J, Herbst R, Govaerts C, Barker T, Cambier S, Yanagisawa H, Goodsell A, Hashimoto M, Brand OJ, Cheng R, Ma R, McKnelly KJ, Wen W, Hill A, Jablons D, Wolters P, Kitamura H, Araya J, Barczak AJ, Erle DJ, Reichardt LF, Marks JD, Baron JL, Nishimura SL. Selective targeting of TGF-β activation to treat fibroinflammatory airway disease. Sci Transl Med 2015; 6:241ra79. [PMID: 24944194 DOI: 10.1126/scitranslmed.3008074] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Airway remodeling, caused by inflammation and fibrosis, is a major component of chronic obstructive pulmonary disease (COPD) and currently has no effective treatment. Transforming growth factor-β (TGF-β) has been widely implicated in the pathogenesis of airway remodeling in COPD. TGF-β is expressed in a latent form that requires activation. The integrin αvβ8 (encoded by the itgb8 gene) is a receptor for latent TGF-β and is essential for its activation. Expression of integrin αvβ8 is increased in airway fibroblasts in COPD and thus is an attractive therapeutic target for the treatment of airway remodeling in COPD. We demonstrate that an engineered optimized antibody to human αvβ8 (B5) inhibited TGF-β activation in transgenic mice expressing only human and not mouse ITGB8. The B5 engineered antibody blocked fibroinflammatory responses induced by tobacco smoke, cytokines, and allergens by inhibiting TGF-β activation. To clarify the mechanism of action of B5, we used hydrodynamic, mutational, and electron microscopic methods to demonstrate that αvβ8 predominantly adopts a constitutively active, extended-closed headpiece conformation. Epitope mapping and functional characterization of B5 revealed an allosteric mechanism of action due to locking-in of a low-affinity αvβ8 conformation. Collectively, these data demonstrate a new model for integrin function and present a strategy to selectively target the TGF-β pathway to treat fibroinflammatory airway diseases.
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Affiliation(s)
- Shunsuke Minagawa
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Jianlong Lou
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Robert I Seed
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Anthony Cormier
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Shenping Wu
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Yifan Cheng
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Lynne Murray
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA. Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Cambridge CB21 6GH, UK
| | - Ping Tsui
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA
| | - Jane Connor
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA
| | - Ronald Herbst
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA
| | - Cedric Govaerts
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Cambridge CB21 6GH, UK
| | - Tyren Barker
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Stephanie Cambier
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Haruhiko Yanagisawa
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Amanda Goodsell
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Mitsuo Hashimoto
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Oliver J Brand
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Ran Cheng
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Royce Ma
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Kate J McKnelly
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Weihua Wen
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Arthur Hill
- Department of Surgery, University of California, San Francisco, San Francisco, CA 94110, USA
| | - David Jablons
- Department of Surgery, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Paul Wolters
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Hideya Kitamura
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Jun Araya
- Department of Pulmonary Medicine, Jikei University, Tokyo 105 8461, Japan
| | - Andrea J Barczak
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - David J Erle
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Louis F Reichardt
- Genetics, Development, and Behavioral Sciences, University of California, San Francisco, San Francisco, CA 94110, USA
| | - James D Marks
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Jody L Baron
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Stephen L Nishimura
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA.
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20
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Forman-Kay JD, Mittag T. From sequence and forces to structure, function, and evolution of intrinsically disordered proteins. Structure 2014; 21:1492-9. [PMID: 24010708 DOI: 10.1016/j.str.2013.08.001] [Citation(s) in RCA: 166] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 08/02/2013] [Accepted: 08/06/2013] [Indexed: 01/27/2023]
Abstract
Intrinsically disordered proteins (IDPs), which lack persistent structure, are a challenge to structural biology due to the inapplicability of standard methods for characterization of folded proteins as well as their deviation from the dominant structure/function paradigm. Their widespread presence and involvement in biological function, however, has spurred the growing acceptance of the importance of IDPs and the development of new tools for studying their structure, dynamics, and function. The interplay of folded and disordered domains or regions for function and the existence of a continuum of protein states with respect to conformational energetics, motional timescales, and compactness are shaping a unified understanding of structure-dynamics-disorder/function relationships. In the 20(th) anniversary of Structure, we provide a historical perspective on the investigation of IDPs and summarize the sequence features and physical forces that underlie their unique structural, functional, and evolutionary properties.
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Affiliation(s)
- Julie D Forman-Kay
- Molecular Structure and Function, Hospital for Sick Children, Toronto, ON, M5G 1X8, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
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21
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Cheng M, Li J, Negri A, Coller BS. Swing-out of the β3 hybrid domain is required for αIIbβ3 priming and normal cytoskeletal reorganization, but not adhesion to immobilized fibrinogen. PLoS One 2013; 8:e81609. [PMID: 24349096 PMCID: PMC3857192 DOI: 10.1371/journal.pone.0081609] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 10/15/2013] [Indexed: 12/24/2022] Open
Abstract
Structural and functional analyses of integrin αIIbβ3 has implicated swing-out motion of the β3 hybrid domain in αIIbβ3 activation and ligand binding. Using data from targeted molecular dynamics (TMD) simulations, we engineered two disulfide-bonded mutant receptors designed to limit swing-out (XS-O). XS-O mutants cannot bind the high Mr ligand fibrinogen in the presence of an activating mAb or after introducing mutations into the αIIb subunit designed to simulate inside-out signaling. They also have reduced capacity to be “primed” to bind fibrinogen by pretreatment with eptifibatide. They can, however, bind the small RGD venom protein kistrin. Despite their inability to bind soluble fibrinogen, the XS-O mutants can support adhesion to immobilized fibrinogen, although such adhesion does not initiate outside-in signaling leading to normal cytoskeletal reorganization. Collectively, our data further define the biologic role of β3 hybrid domain swing-out in both soluble and immobilized high Mr ligand binding, as well as in priming and outside-in signaling. We also infer that swing-out is likely to be a downstream effect of receptor extension.
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Affiliation(s)
- Ming Cheng
- Allen and Frances Adler Laboratory of Blood and Vascular Biology, The Rockefeller University, New York, New York, United States of America
| | - Jihong Li
- Allen and Frances Adler Laboratory of Blood and Vascular Biology, The Rockefeller University, New York, New York, United States of America
| | - Ana Negri
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Barry S. Coller
- Allen and Frances Adler Laboratory of Blood and Vascular Biology, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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22
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Abstract
Crystals soaked with RGD peptides reveal six intermediate conformational states between the closed and higher affinity, fully open state of the integrin αIIbβ3 headpiece. Carefully soaking crystals with Arg-Gly-Asp (RGD) peptides, we captured eight distinct RGD-bound conformations of the αIIbβ3 integrin headpiece. Starting from the closed βI domain conformation, we saw six intermediate βI conformations and finally the fully open βI with the hybrid domain swung out in the crystal lattice. The β1-α1 backbone that hydrogen bonds to the Asp side chain of RGD was the first element to move followed by adjacent to metal ion-dependent adhesion site Ca2+, α1 helix, α1’ helix, β6-α7 loop, α7 helix, and hybrid domain. We define in atomic detail how conformational change was transmitted over long distances in integrins, 40 Å from the ligand binding site to the opposite end of the βI domain and 80 Å to the far end of the hybrid domain. During these movements, RGD slid in its binding groove toward αIIb, and its Arg side chain became ordered. RGD concentration requirements in soaking suggested a >200-fold higher affinity after opening. The thermodynamic cycle shows how higher affinity pays the energetic cost of opening.
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Affiliation(s)
- Jieqing Zhu
- Department of Biological Chemistry and Molecular Pharmacology, Program in Cellular and Molecular Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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23
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Stegmann M, Metcalfe C, Barclay AN. Immunoregulation through membrane proteins modified by reducing conditions induced by immune reactions. Eur J Immunol 2013; 43:15-21. [PMID: 23233323 PMCID: PMC7163605 DOI: 10.1002/eji.201242849] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 10/22/2012] [Accepted: 12/05/2012] [Indexed: 01/19/2023]
Abstract
Selected disulfide bonds in membrane proteins are labile and are thus susceptible to changes in redox potential and/or the presence of thiol isomerase enzymes. Modification of these disulfide bonds can lead to conformational changes of the protein that in turn may alter protein activity and function. This occurs in the entry of several enveloped viruses into their host cells, e.g. HIV, hepatitis C virus and Newcastle disease virus. Labile disulfide bonds are also important in platelet activation, cytokine signalling and in a variety of diseases including cancer and arthritis. In this review we will concentrate on recent advances in understanding the conditions that lead to disulfide bond reduction in membrane proteins and their effects in regulating immune function.
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Affiliation(s)
- Monika Stegmann
- Oxford Molecular Pathology Institute, Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, United Kingdom
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24
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Abstract
It has been known for many decades that cell surface, soluble-secreted, and extracellular matrix proteins are generally rich in disulfide bonds, but only more recently has the functional diversity of disulfide bonding in extracellular proteins been appreciated. In addition to the classic mechanisms by which disulfide bonds enhance protein thermodynamic stability, disulfides in certain configurations contribute particular mechanical properties to proteins that sense and respond to tensile forces. Disulfides may help warp protein folds for the evolution of new functions, or they may fasten aggregation-prone flaps of polypeptide to protein surfaces to prevent fibrilization or oligomerization. Disulfides can also be used to package and secure macromolecular cargo for intercellular transport. A series of case studies illustrating diverse biophysical roles of disulfide bonding are reviewed, with a focus on proteins functioning in the extracellular environment.
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Affiliation(s)
- Deborah Fass
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
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25
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Zhang K, Pan Y, Qi J, Yue J, Zhang M, Xu C, Li G, Chen J. Disruption of disulfide-restriction at integrin knees induces activation and ligand-independent signaling of α4β7. J Cell Sci 2013; 126:5030-41. [DOI: 10.1242/jcs.134528] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Control of integrin activation and signaling plays critical roles in cell adhesion, spreading, and migration. Here, we report that selective breakage of two conserved disulfide bonds located at the knees of integrin, α4C589–C594 and β7C494–C526, induced α4β7 activation. This activated α4β7 had a unique structure different from the typical extended conformation of active integrin. In addition, these activated α4β7 integrins spontaneously clustered on the cell membrane and triggered integrin downstream signaling independent of ligand binding. Although these disulfide bonds were not broken during α4β7 activation by inside-out signaling or Mn2+, they could be specifically reduced by 0.1 mM dithiothreitol, a reducing strength that could be produced in vivo under certain conditions. Our findings reveal a novel mechanism of integrin activation under specific reducing conditions by which integrin can signal and promote cell spreading in the absence of ligand.
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26
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Dong X, Mi LZ, Zhu J, Wang W, Hu P, Luo BH, Springer TA. α(V)β(3) integrin crystal structures and their functional implications. Biochemistry 2012; 51:8814-28. [PMID: 23106217 PMCID: PMC3495331 DOI: 10.1021/bi300734n] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many questions about the significance of structural features of integrin α(V)β(3) with respect to its mechanism of activation remain. We have determined and re-refined crystal structures of the α(V)β(3) ectodomain linked to C-terminal coiled coils (α(V)β(3)-AB) and four transmembrane (TM) residues in each subunit (α(V)β(3)-1TM), respectively. The α(V) and β(3) subunits with four and eight extracellular domains, respectively, are bent at knees between the integrin headpiece and lower legs, and the headpiece has the closed, low-affinity conformation. The structures differ in the occupancy of three metal-binding sites in the βI domain. Occupancy appears to be related to the pH of crystallization, rather than to the physiologic regulation of ligand binding at the central, metal ion-dependent adhesion site. No electron density was observed for TM residues and much of the α(V) linker. α(V)β(3)-AB and α(V)β(3)-1TM demonstrate flexibility in the linker between their extracellular and TM domains, rather than the previously proposed rigid linkage. A previously postulated interface between the α(V) and β(3) subunits at their knees was also not supported, because it lacks high-quality density, required rebuilding in α(V)β(3)-1TM, and differed markedly between α(V)β(3)-1TM and α(V)β(3)-AB. Together with the variation in domain-domain orientation within their bent ectodomains between α(V)β(3)-AB and α(V)β(3)-1TM, these findings are compatible with the requirement for large structural changes, such as extension at the knees and headpiece opening, in conveying activation signals between the extracellular ligand-binding site and the cytoplasm.
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Affiliation(s)
- Xianchi Dong
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
| | - Li-Zhi Mi
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
| | - Jianghai Zhu
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
| | - Wei Wang
- Department of Biological Sciences, 202 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803
| | - Ping Hu
- Department of Biological Sciences, 202 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803
| | - Bing-Hao Luo
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
- Department of Biological Sciences, 202 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803
| | - Timothy A. Springer
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
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27
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Schürpf T, Chen Q, Liu JH, Wang R, Springer TA, Wang JH. The RGD finger of Del-1 is a unique structural feature critical for integrin binding. FASEB J 2012; 26:3412-20. [PMID: 22601780 DOI: 10.1096/fj.11-202036] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Developmental endothelial cell locus-1 (Del-1) glycoprotein is secreted by endothelial cells and a subset of macrophages. Del-1 plays a regulatory role in vascular remodeling and functions in innate immunity through interaction with integrin α(V)β(3). Del-1 contains 3 epidermal growth factor (EGF)-like repeats and 2 discoidin-like domains. An Arg-Gly-Asp (RGD) motif in the second EGF domain (EGF2) mediates adhesion by endothelial cells and phagocytes. We report the crystal structure of its 3 EGF domains. The RGD motif of EGF2 forms a type II' β turn at the tip of a long protruding loop, dubbed the RGD finger. Whereas EGF2 and EGF3 constitute a rigid rod via an interdomain calcium ion binding site, the long linker between EGF1 and EGF2 lends considerable flexibility to EGF1. Two unique O-linked glycans and 1 N-linked glycan locate to the opposite side of EGF2 from the RGD motif. These structural features favor integrin binding of the RGD finger. Mutagenesis data confirm the importance of having the RGD motif at the tip of the RGD finger. A database search for EGF domain sequences shows that this RGD finger is likely an evolutionary insertion and unique to the EGF domain of Del-1 and its homologue milk fat globule-EGF 8.
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Affiliation(s)
- Thomas Schürpf
- Immune Disease Institute, Harvard Medical School, Boston, MA, USA
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Mor-Cohen R, Rosenberg N, Einav Y, Zelzion E, Landau M, Mansour W, Averbukh Y, Seligsohn U. Unique disulfide bonds in epidermal growth factor (EGF) domains of β3 affect structure and function of αIIbβ3 and αvβ3 integrins in different manner. J Biol Chem 2012; 287:8879-91. [PMID: 22308022 DOI: 10.1074/jbc.m111.311043] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The β3 subunit of αIIbβ3 and αvβ3 integrins contains four epidermal growth factor (EGF)-like domains. Each domain harbors four disulfide bonds of which one is unique for integrins. We previously discerned a regulatory role of the EGF-4 Cys-560-Cys-583 unique bond for αIIbβ3 activation. In this study we further investigated the role of all four integrin unique bonds in both αIIbβ3 and αvβ3. We created β3 mutants harboring serine substitutions of each or both cysteines that disrupt the four unique bonds (Cys-437-Cys-457 in EGF-1, Cys-473-Cys-503 in EGF-2, Cys-523-Cys-544 in EGF-3, and Cys-560-Cys-583 in EGF-4) and transfected them into baby hamster kidney cells together with normal αv or αIIb. Flow cytometry was used to measure surface expression of αIIbβ3 and αvβ3 and their activity state by soluble fibrinogen binding. Most cysteine substitutions caused similarly reduced surface expression of both receptors. Disrupting all four unique disulfide bonds by single cysteine substitutions resulted in variable constitutive activation of αIIbβ3 and αvβ3. In contrast, whereas double C437S/C457S and C473S/C503S mutations yielded constitutively active αIIbβ3 and αvβ3, the C560S/C583S mutation did not, and the C523S/C544S mutation only yielded constitutively active αIIbβ3. Activation of C523S/C544S αvβ3 mutant by activating antibody and dithiothreitol was also impaired. Molecular dynamics of C523S/C544S β3 in αIIbβ3 but not in αvβ3 displayed an altered stable conformation. Our findings indicate that unique disulfide bonds in β3 differently affect the function of αIIbβ3 and αvβ3 and suggest a free sulfhydryl-dependent regulatory role for Cys-560-Cys-583 in both αIIbβ3 and αvβ3 and for Cys-523-Cys-544 only in αvβ3.
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Affiliation(s)
- Ronit Mor-Cohen
- the Amalia Biron Research Institute of Thrombosis and Hemostasis, Chaim Sheba Medical Center, Tel-Hashomer, Israel.
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29
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Integrin inside-out signaling and the immunological synapse. Curr Opin Cell Biol 2011; 24:107-15. [PMID: 22129583 DOI: 10.1016/j.ceb.2011.10.004] [Citation(s) in RCA: 291] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 10/19/2011] [Indexed: 11/22/2022]
Abstract
Integrins dynamically equilibrate between three conformational states on cell surfaces. A bent conformation has a closed headpiece. Two extended conformations contain either a closed or an open headpiece. Headpiece opening involves hybrid domain swing-out and a 70 Å separation at the integrin knees, which is conveyed by allostery from the hybrid-proximal end of the βI domain to a 3 Å rearrangement of the ligand-binding site at the opposite end of the βI domain. Both bent-closed and extended-closed integrins have low affinity, whereas extended-open integrin affinity is 10(3) to 10(4) higher. Integrin-mediated adhesion requires the extended-open conformation, which in physiological contexts is stabilized by post-ligand binding events. Integrins thus discriminate between substrate-bound and soluble ligands. Analysis of LFA-1-ICAM-1 interactions in the immunological synapse suggests that bond lifetimes are on the order of seconds, which is consistent with high affinity interactions subjected to cytoskeletal forces that increase the dissociation rate. LFA-1 βI domain antagonists abrogate function in the immunological synapse, further supporting a critical role for high affinity LFA-1.
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30
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Weitz-Schmidt G, Schürpf T, Springer TA. The C-terminal αI domain linker as a critical structural element in the conformational activation of αI integrins. J Biol Chem 2011; 286:42115-42122. [PMID: 21965670 DOI: 10.1074/jbc.m111.282830] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activation of α/β heterodimeric integrins is the result of highly coordinated rearrangements within both subunits. The molecular interactions between the two subunits, however, remain to be characterized. In this study, we use the integrin α(L)β(2) to investigate the functional role of the C-linker polypeptide that connects the C-terminal end of the inserted (I) domain with the β-propeller domain on the α subunit and is located at the interface with the βI domain of the β chain. We demonstrate that shortening of the C-linker by eight or more amino acids results in constitutively active α(L)β(2) in which the αI domain is no longer responsive to the regulation by the βI domain. Despite this intersubunit uncoupling, both I domains remain individually sensitive to intrasubunit conformational changes induced by allosteric modulators. Interestingly, the length and not the sequence of the C-linker appears to be critical for its functionality in α/β intersubunit communication. Using two monoclonal antibodies (R7.1 and CBR LFA-1/1) we further demonstrate that shortening of the C-linker results in the gradual loss of combinational epitopes that require both the αI and β-propeller domains for full reactivity. Taken together, our findings highlight the role of the C-linker as a spring-like element that allows relaxation of the αI domain in the resting state and controlled tension of the αI domain during activation, exerted by the β chain.
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Affiliation(s)
- Gabriele Weitz-Schmidt
- Immune Disease Institute, Children's Hospital Boston and Department of Pathology, Harvard Medical School, Boston Massachusetts 02115; University Basel, PharmaCenter, Klingelbergstr. 50-70, 4056 Basel, Switzerland.
| | - Thomas Schürpf
- Immune Disease Institute, Children's Hospital Boston and Department of Pathology, Harvard Medical School, Boston Massachusetts 02115
| | - Timothy A Springer
- Immune Disease Institute, Children's Hospital Boston and Department of Pathology, Harvard Medical School, Boston Massachusetts 02115.
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31
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Huang PS, Ban YEA, Richter F, Andre I, Vernon R, Schief WR, Baker D. RosettaRemodel: a generalized framework for flexible backbone protein design. PLoS One 2011; 6:e24109. [PMID: 21909381 PMCID: PMC3166072 DOI: 10.1371/journal.pone.0024109] [Citation(s) in RCA: 241] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 07/29/2011] [Indexed: 12/12/2022] Open
Abstract
We describe RosettaRemodel, a generalized framework for flexible protein design that provides a versatile and convenient interface to the Rosetta modeling suite. RosettaRemodel employs a unified interface, called a blueprint, which allows detailed control over many aspects of flexible backbone protein design calculations. RosettaRemodel allows the construction and elaboration of customized protocols for a wide range of design problems ranging from loop insertion and deletion, disulfide engineering, domain assembly, loop remodeling, motif grafting, symmetrical units, to de novo structure modeling.
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Affiliation(s)
- Po-Ssu Huang
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Yih-En Andrew Ban
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Florian Richter
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Interdisciplinary Program in Biomolecular Structure and Design, University of Washington, Seattle, Washington, United States of America
| | - Ingemar Andre
- Department of Biochemistry and Structural Biology, Lund University, Lund, Sweden
| | - Robert Vernon
- Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, Ontario, Canada
| | - William R. Schief
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail: (WRS); (DB)
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, United States of America
- * E-mail: (WRS); (DB)
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32
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Eng ET, Smagghe BJ, Walz T, Springer TA. Intact alphaIIbbeta3 integrin is extended after activation as measured by solution X-ray scattering and electron microscopy. J Biol Chem 2011; 286:35218-26. [PMID: 21832081 DOI: 10.1074/jbc.m111.275107] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrins are bidirectional signaling molecules on the cell surface that have fundamental roles in regulating cell behavior and contribute to cell migration and adhesion. Understanding of the mechanism of integrin signaling and activation has been advanced with truncated ectodomain preparations; however, the nature of conformational change in the full-length intact integrin molecule remains an active area of research. Here we used small angle x-ray scattering and electron microscopy to study detergent-solubilized, intact platelet integrin α(IIb)β(3). In the resting state, the intact α(IIb)β(3) adopted a compact, bent conformation. Upon activation with Mn(2+), the average integrin extension increased. Further activation by addition of ligand led to stabilization of the extended state and opening of the headpiece. The observed extension and conformational rearrangement upon activation are consistent with the extension and headpiece opening model of integrin activation.
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Affiliation(s)
- Edward T Eng
- Immune Disease Institute, Children's Hospital Boston, and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA
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33
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Anthis NJ, Campbell ID. The tail of integrin activation. Trends Biochem Sci 2011; 36:191-8. [PMID: 21216149 DOI: 10.1016/j.tibs.2010.11.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 11/29/2010] [Accepted: 11/30/2010] [Indexed: 12/13/2022]
Abstract
Integrins are essential adhesion receptors found on the surfaces of all metazoan cells. As regulators of cell migration and extracellular matrix assembly, these membrane-spanning heterodimers are critical for embryonic development, tissue repair and immune responses. Signals transmitted by integrins from outside to inside the cell promote cell survival and proliferation, but integrin affinity for extracellular ligands can also be controlled by intracellular cues. This bidirectional signaling is mediated by the short cytoplasmic tails of the two integrin subunits. Recent structural and functional studies of various integrin fragments and complexes between the cytoplasmic tails and intracellular proteins, such as talin, have provided new insight into the signaling processes centered around the tails, particularly inside-out integrin activation.
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Affiliation(s)
- Nicholas J Anthis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA
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