1
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Go YJ, Kalathingal M, Rhee YM. Elucidating activation and deactivation dynamics of VEGFR-2 transmembrane domain with coarse-grained molecular dynamics simulations. PLoS One 2023; 18:e0281781. [PMID: 36795710 PMCID: PMC9934429 DOI: 10.1371/journal.pone.0281781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 02/01/2023] [Indexed: 02/17/2023] Open
Abstract
The vascular endothelial growth factor receptor 2 (VEGFR-2) is a member of receptor tyrosine kinases (RTKs) and is a dimeric membrane protein that functions as a primary regulator of angiogenesis. As is usual with RTKs, spatial alignment of its transmembrane domain (TMD) is essential toward VEGFR-2 activation. Experimentally, the helix rotations within TMD around their own helical axes are known to participate importantly toward the activation process in VEGFR-2, but the detailed dynamics of the interconversion between the active and inactive TMD forms have not been clearly elucidated at the molecular level. Here, we attempt to elucidate the process by using coarse grained (CG) molecular dynamics (MD) simulations. We observe that inactive dimeric TMD in separation is structurally stable over tens of microseconds, suggesting that TMD itself is passive and does not allow spontaneous signaling of VEGFR-2. By starting from the active conformation, we reveal the mechanism of TMD inactivation through analyzing the CG MD trajectories. We observe that interconversions between a left-handed overlay and a right-handed one are essential for the process of going from an active TMD structure to the inactive form. In addition, our simulations find that the helices can rotate properly when the overlaying structure of the helices interconverts and when the crossing angle of the two helices changes by larger than ~40 degrees. As the activation right after the ligand attachment on VEGFR-2 will take place in the reverse manner of this inactivation process, these structural aspects will also appear importantly for the activation process. The rather large change in helix configuration for activation also explains why VEGFR-2 rarely self-activate and how the activating ligand structurally drive the whole VEGFR-2. This mechanism of TMD activation / inactivation within VEGFR-2 may help in further understanding the overall activation processes of other RTKs.
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Affiliation(s)
- Yeon Ju Go
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Mahroof Kalathingal
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - Young Min Rhee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
- * E-mail:
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2
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Keller F, Alavizargar A, Wedlich-Söldner R, Heuer A. The impact of bilayer composition on the dimerization properties of the Slg1 stress sensor TMD from a multiscale analysis. Phys Chem Chem Phys 2023; 25:1299-1309. [PMID: 36533706 DOI: 10.1039/d2cp03497b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The impact of mutual interactions between the transmembrane domains of membrane proteins and lipids on bilayer properties has gained major attraction. Most simulation studies of membranes rely on the Martini force field, which has proven extremely helpful in providing molecular insights into realistic systems. Accordingly, an evaluation of the accuracy of the Martini force field is crucial to be able to correctly interpret the reported data. In this study, we combine atomistic and coarse-grained Martini simulations to investigate the properties of transmembrane domains (TMDs) in a model yeast membrane. The results show that the TMD binding state (monomeric and dimeric with positive or negative crossing angle) and the membrane composition significantly influence the properties around the TMDs and change TMD-TMD and TMD-lipid affinities. Furthermore, ergosterol (ERG) exhibits a strong affinity to TMD dimers. Importantly, the right-handed TMD dimer configuration is stabilized via TMD-TMD contacts by the addition of asymmetric anionic phosphatidylserine (PS). The coarse-grained simulations corroborate many of these findings, with two notable exceptions: a systematic overestimation of TMD-ERG interaction and lack of stabilization of the right-handed TMD dimers with the addition of PS.
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Affiliation(s)
- Fabian Keller
- Institut für Physikalische Chemie, Corrensstraße 28, Münster, Germany.
| | | | | | - Andreas Heuer
- Institut für Physikalische Chemie, Corrensstraße 28, Münster, Germany.
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3
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Increased stability of the TM helix oligomer abrogates the apoptotic activity of the human Fas receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2022; 1864:183807. [PMID: 34662567 DOI: 10.1016/j.bbamem.2021.183807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 09/27/2021] [Accepted: 10/10/2021] [Indexed: 11/21/2022]
Abstract
Human death receptors control apoptotic events during cell differentiation, cell homeostasis and the elimination of damaged or infected cells. Receptor activation involves ligand-induced structural reorganizations of preformed receptor trimers. Here we show that the death receptor transmembrane domains only have a weak intrinsic tendency to homo-oligomerize within a membrane, and thus these domains potentially do not significantly contribute to receptor trimerization. However, mutation of Pro183 in the human CD95/Fas receptor transmembrane helix results in a dramatically increased interaction propensity, as shown by genetic assays. The increased interaction of the transmembrane domain is coupled with a decreased ligand-sensitivity of cells expressing the Fas receptor, and thus in a decreased number of apoptotic events. Mutation of Pro183 likely results in a substantial rearrangement of the self-associated Fas receptor transmembrane trimer, which likely abolishes further signaling of the apoptotic signal but may activate other signaling pathways. Our study shows that formation of a stable Fas receptor transmembrane helix oligomer does not per se result in receptor activation.
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4
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Minh Hung H, Dieu Hang T, Nguyen MT. Structural Investigation of Human Prolactin Receptor Transmembrane Domain Homodimerization in a Membrane Environment through Multiscale Simulations. J Phys Chem B 2019; 123:4858-4866. [PMID: 31099581 DOI: 10.1021/acs.jpcb.9b01986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
It is well established that prolactin (PRL) and its receptor (PRLR) are associated with hundreds of biological functions. They have been postulated to be linked to breast and prostate cancers, and PRLR signaling has attracted considerable medical and pharmaceutical interest in the development of compounds targeting PRLR. Dimerization of the receptor through its transmembrane (TM) domain is a key step for understanding its signaling and related issues. Our multiscale simulation results revealed that its TM domain can form dimers in a membrane environment with distinct states stabilized by different residue motifs. On the basis of the simulated data, an activation mechanism of PRL with the importance of two symmetrical tryptophan residues was proposed in detail to determine the conformational change of its receptor, which is essential for signal transduction. The better knowledge of PRLR structure and its protein-protein interaction can considerably contribute to a further understanding of PRLR signaling action and thereby help to develop some new PRLR signaling-based strategies for PRL-related diseases.
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Affiliation(s)
- Huynh Minh Hung
- Department of Chemistry , KU Leuven , Celestijnenlaan 200F , B-3001 Leuven , Belgium.,Department of Chemistry , Quy Nhon University , Quy Nhon 590000 , Vietnam
| | - Tran Dieu Hang
- Department of Chemistry , KU Leuven , Celestijnenlaan 200F , B-3001 Leuven , Belgium.,Department of Chemistry , Quy Nhon University , Quy Nhon 590000 , Vietnam
| | - Minh Tho Nguyen
- Computational Chemistry Research Group , Ton Duc Thang University , Ho Chi Minh City 700000 Vietnam.,Faculty of Applied Sciences , Ton Duc Thang University , Ho Chi Minh City 700000 Vietnam
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5
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Corradi V, Sejdiu BI, Mesa-Galloso H, Abdizadeh H, Noskov SY, Marrink SJ, Tieleman DP. Emerging Diversity in Lipid-Protein Interactions. Chem Rev 2019; 119:5775-5848. [PMID: 30758191 PMCID: PMC6509647 DOI: 10.1021/acs.chemrev.8b00451] [Citation(s) in RCA: 239] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Membrane
lipids interact with proteins in a variety of ways, ranging
from providing a stable membrane environment for proteins to being
embedded in to detailed roles in complicated and well-regulated protein
functions. Experimental and computational advances are converging
in a rapidly expanding research area of lipid–protein interactions.
Experimentally, the database of high-resolution membrane protein structures
is growing, as are capabilities to identify the complex lipid composition
of different membranes, to probe the challenging time and length scales
of lipid–protein interactions, and to link lipid–protein
interactions to protein function in a variety of proteins. Computationally,
more accurate membrane models and more powerful computers now enable
a detailed look at lipid–protein interactions and increasing
overlap with experimental observations for validation and joint interpretation
of simulation and experiment. Here we review papers that use computational
approaches to study detailed lipid–protein interactions, together
with brief experimental and physiological contexts, aiming at comprehensive
coverage of simulation papers in the last five years. Overall, a complex
picture of lipid–protein interactions emerges, through a range
of mechanisms including modulation of the physical properties of the
lipid environment, detailed chemical interactions between lipids and
proteins, and key functional roles of very specific lipids binding
to well-defined binding sites on proteins. Computationally, despite
important limitations, molecular dynamics simulations with current
computer power and theoretical models are now in an excellent position
to answer detailed questions about lipid–protein interactions.
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Affiliation(s)
- Valentina Corradi
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Besian I Sejdiu
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Haydee Mesa-Galloso
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Haleh Abdizadeh
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials , University of Groningen , Nijenborgh 7 , 9747 AG Groningen , The Netherlands
| | - Sergei Yu Noskov
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials , University of Groningen , Nijenborgh 7 , 9747 AG Groningen , The Netherlands
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
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6
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Ulmschneider JP, Smith JC, White SH, Ulmschneider MB. The importance of the membrane interface as the reference state for membrane protein stability. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2539-2548. [PMID: 30293965 DOI: 10.1016/j.bbamem.2018.09.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/14/2018] [Accepted: 09/16/2018] [Indexed: 11/26/2022]
Abstract
The insertion of nascent polypeptide chains into lipid bilayer membranes and the stability of membrane proteins crucially depend on the equilibrium partitioning of polypeptides. For this, the transfer of full sequences of amino-acid residues into the bilayer, rather than individual amino acids, must be understood. Earlier studies have revealed that the most likely reference state for partitioning very hydrophobic sequences is the membrane interface. We have used μs-scale simulations to calculate the interface-to-transmembrane partitioning free energies ΔGS→TM for two hydrophobic carrier sequences in order to estimate the insertion free energy for all 20 amino acid residues when bonded to the center of a partitioning hydrophobic peptide. Our results show that prior single-residue scales likely overestimate the partitioning free energies of polypeptides. The correlation of ΔGS→TM with experimental full-peptide translocon insertion data is high, suggesting an important role for the membrane interface in translocon-based insertion. The choice of carrier sequence greatly modulates the contribution of each single-residue mutation to the overall partitioning free energy. Our results demonstrate the importance of quantifying the observed full-peptide partitioning equilibrium, which is between membrane interface and transmembrane inserted, rather than combining individual water-to-membrane amino acid transfer free energies.
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Affiliation(s)
- Jakob P Ulmschneider
- School of Physics and Astronomy and the Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China.
| | - Jeremy C Smith
- Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Department of Biochemistry & Cellular Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | - Stephen H White
- Department of Physiology & Biophysics, University of California at Irvine, Irvine, CA, USA
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7
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Shams H, Soheilypour M, Peyro M, Moussavi-Baygi R, Mofrad MRK. Looking "Under the Hood" of Cellular Mechanotransduction with Computational Tools: A Systems Biomechanics Approach across Multiple Scales. ACS Biomater Sci Eng 2017; 3:2712-2726. [PMID: 33418698 DOI: 10.1021/acsbiomaterials.7b00117] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Signal modulation has been developed in living cells throughout evolution to promote utilizing the same machinery for multiple cellular functions. Chemical and mechanical modules of signal transmission and transduction are interconnected and necessary for organ development and growth. However, due to the high complexity of the intercommunication of physical intracellular connections with biochemical pathways, there are many missing details in our overall understanding of mechanotransduction processes, i.e., the process by which mechanical signals are converted to biochemical cascades. Cell-matrix adhesions are mechanically coupled to the nucleus through the cytoskeleton. This modulated and tightly integrated network mediates the transmission of mechanochemical signals from the extracellular matrix to the nucleus. Various experimental and computational techniques have been utilized to understand the basic mechanisms of mechanotransduction, yet many aspects have remained elusive. Recently, in silico experiments have made important contributions to the field of mechanobiology. Herein, computational modeling efforts devoted to understanding integrin-mediated mechanotransduction pathways are reviewed, and an outlook is presented for future directions toward using suitable computational approaches and developing novel techniques for addressing important questions in the field of mechanotransduction.
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Affiliation(s)
- Hengameh Shams
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohammad Soheilypour
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohaddeseh Peyro
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Ruhollah Moussavi-Baygi
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
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8
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Cao Y, Wu X, Yang R, Wang X, Sun H, Lee I. Self-assembling study of sarcolipin and its mutants in multiple molecular dynamic simulations. Proteins 2017; 85:1065-1077. [PMID: 28241400 DOI: 10.1002/prot.25273] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 01/16/2017] [Accepted: 02/12/2017] [Indexed: 01/12/2023]
Abstract
The Sarcolipin (SLN) is a single trans-membrane protein that can self-assembly to dimer and oligomer for playing importantphysiological function. In this work, we addressed the dimerization of wild type SLN (wSLN) and its mutants (mSLNs) - I17A and I20A, using both coarse-grained (CG) and atomistic (AT) molecular dynamics (MD) simulations. Our results demonstrated that wSLN homodimer assembled as a left-handed helical complex, while mSLNs heterodimers assembled as right-handed complexes. Analysis of residue-residue contacts map indicated that isoleucine (Ile)-leucione (Leu) zipper domain played an important role in dimerization. The potential of mean force (PMF) demonstrated that wSLN homodimer was more stable than mSLNs heterodimers. Meanwhile, the mSLNs heterodimers preferred right-handed rather than left-handed helix. AT-MD simulations for wSLN and mSLNs were also in line with CG-MD simulations. These results provided the insights for understanding the mechanisms of SLNs self-assembling. Proteins 2017; 85:1065-1077. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Yipeng Cao
- School of Physics, Nankai University, 94 Weijin Road, Tianjin, 300071, P.R.China
| | - Xue Wu
- School of Physics, Nankai University, 94 Weijin Road, Tianjin, 300071, P.R.China
| | - Rui Yang
- School of Medicine, Nankai University, 94 Weijin Road, Tianjin, 300071, P.R.China
| | - Xinyu Wang
- School of Physics, Nankai University, 94 Weijin Road, Tianjin, 300071, P.R.China
| | - Haiying Sun
- School of Physics, Nankai University, 94 Weijin Road, Tianjin, 300071, P.R.China
| | - Imshik Lee
- School of Physics, Nankai University, 94 Weijin Road, Tianjin, 300071, P.R.China
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9
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Lelimousin M, Limongelli V, Sansom MSP. Conformational Changes in the Epidermal Growth Factor Receptor: Role of the Transmembrane Domain Investigated by Coarse-Grained MetaDynamics Free Energy Calculations. J Am Chem Soc 2016; 138:10611-22. [PMID: 27459426 PMCID: PMC5010359 DOI: 10.1021/jacs.6b05602] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
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The epidermal growth
factor receptor (EGFR) is a dimeric membrane
protein that regulates key aspects of cellular function. Activation
of the EGFR is linked to changes in the conformation of the transmembrane
(TM) domain, brought about by changes in interactions of the TM helices
of the membrane lipid bilayer. Using an advanced computational approach
that combines Coarse-Grained molecular dynamics and well-tempered
MetaDynamics (CG-MetaD), we characterize the large-scale motions
of the TM helices, simulating multiple association and dissociation
events between the helices in membrane, thus leading to a free energy
landscape of the dimerization process. The lowest energy state of
the TM domain is a right-handed dimer structure in which the TM helices
interact through the N-terminal small-X3-small sequence
motif. In addition to this state, which is thought to correspond to
the active form of the receptor, we have identified further low-energy
states that allow us to integrate with a high level of detail a range
of previous experimental observations. These conformations may lead
to the active state via two possible activation pathways, which involve
pivoting and rotational motions of the helices, respectively. Molecular
dynamics also reveals correlation between the conformational changes
of the TM domains and of the intracellular juxtamembrane domains,
paving the way for a comprehensive understanding of EGFR signaling
at the cell membrane.
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Affiliation(s)
- Mickaël Lelimousin
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, U.K.,CERMAV, Université Grenoble Alpes and CNRS , BP 53, F-38041 Grenoble Cedex 9, France
| | - Vittorio Limongelli
- Università della Svizzera Italiana (USI), Faculty of Informatics, Institute of Computational Science - Center for Computational Medicine in Cardiology , via G. Buffi 13, CH-6900 Lugano, Switzerland.,Department of Pharmacy, University of Naples "Federico II" , via D. Montesano 49, I-80131 Naples, Italy
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, U.K
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10
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Kalli AC, Rog T, Vattulainen I, Campbell ID, Sansom MSP. The Integrin Receptor in Biologically Relevant Bilayers: Insights from Molecular Dynamics Simulations. J Membr Biol 2016; 250:337-351. [PMID: 27465729 PMCID: PMC5579164 DOI: 10.1007/s00232-016-9908-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/25/2016] [Indexed: 11/27/2022]
Abstract
Integrins are heterodimeric (αβ) cell surface receptors that are potential therapeutic targets for a number of diseases. Despite the existence of structural data for all parts of integrins, the structure of the complete integrin receptor is still not available. We have used available structural data to construct a model of the complete integrin receptor in complex with talin F2-F3 domain. It has been shown that the interactions of integrins with their lipid environment are crucial for their function but details of the integrin/lipid interactions remain elusive. In this study an integrin/talin complex was inserted in biologically relevant bilayers that resemble the cell plasma membrane containing zwitterionic and charged phospholipids, cholesterol and sphingolipids to study the dynamics of the integrin receptor and its effect on bilayer structure and dynamics. The results of this study demonstrate the dynamic nature of the integrin receptor and suggest that the presence of the integrin receptor alters the lipid organization between the two leaflets of the bilayer. In particular, our results suggest elevated density of cholesterol and of phosphatidylserine lipids around the integrin/talin complex and a slowing down of lipids in an annulus of ~30 Å around the protein due to interactions between the lipids and the integrin/talin F2-F3 complex. This may in part regulate the interactions of integrins with other related proteins or integrin clustering thus facilitating signal transduction across cell membranes.
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Affiliation(s)
- Antreas C Kalli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Tomasz Rog
- Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland
- MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark, 5230, Odense M, Denmark
| | - Iain D Campbell
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
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11
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Han J, Pluhackova K, Wassenaar TA, Böckmann RA. Synaptobrevin Transmembrane Domain Dimerization Studied by Multiscale Molecular Dynamics Simulations. Biophys J 2016; 109:760-71. [PMID: 26287628 DOI: 10.1016/j.bpj.2015.06.049] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/25/2015] [Accepted: 06/25/2015] [Indexed: 11/25/2022] Open
Abstract
Synaptic vesicle fusion requires assembly of the SNARE complex composed of SNAP-25, syntaxin-1, and synaptobrevin-2 (sybII) proteins. The SNARE proteins found in vesicle membranes have previously been shown to dimerize via transmembrane (TM) domain interactions. While syntaxin homodimerization is supposed to promote the transition from hemifusion to complete fusion, the role of synaptobrevin's TM domain association in the fusion process remains poorly understood. Here, we combined coarse-grained and atomistic simulations to model the homodimerization of the sybII transmembrane domain and of selected TM mutants. The wild-type helix is shown to form a stable, right-handed dimer with the most populated helix-helix interface, including key residues predicted in a previous mutagenesis study. In addition, two alternative binding interfaces were discovered, which are essential to explain the experimentally observed higher-order oligomerization of sybII. In contrast, only one dimerization interface was found for a fusion-inactive poly-Leu mutant. Moreover, the association kinetics found for this mutant is lower as compared to the wild-type. These differences in dimerization between the wild-type and the poly-Leu mutant are suggested to be responsible for the reported differences in fusogenic activity between these peptides. This study provides molecular insight into the role of TM sequence specificity for peptide aggregation in membranes.
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Affiliation(s)
- Jing Han
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Kristyna Pluhackova
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Tsjerk A Wassenaar
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
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12
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Hall BA, Halim KBA, Buyan A, Emmanouil B, Sansom MSP. Sidekick for Membrane Simulations: Automated Ensemble Molecular Dynamics Simulations of Transmembrane Helices. J Chem Theory Comput 2015; 10:2165-75. [PMID: 26580541 DOI: 10.1021/ct500003g] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The interactions of transmembrane (TM) α-helices with the phospholipid membrane and with one another are central to understanding the structure and stability of integral membrane proteins. These interactions may be analyzed via coarse grained molecular dynamics (CGMD) simulations. To obtain statistically meaningful analysis of TM helix interactions, large (N ca. 100) ensembles of CGMD simulations are needed. To facilitate the running and analysis of such ensembles of simulations, we have developed Sidekick, an automated pipeline software for performing high throughput CGMD simulations of α-helical peptides in lipid bilayer membranes. Through an end-to-end approach, which takes as input a helix sequence and outputs analytical metrics derived from CGMD simulations, we are able to predict the orientation and likelihood of insertion into a lipid bilayer of a given helix of a family of helix sequences. We illustrate this software via analyses of insertion into a membrane of short hydrophobic TM helices containing a single cationic arginine residue positioned at different positions along the length of the helix. From analyses of these ensembles of simulations, we estimate apparent energy barriers to insertion which are comparable to experimentally determined values. In a second application, we use CGMD simulations to examine the self-assembly of dimers of TM helices from the ErbB1 receptor tyrosine kinase and analyze the numbers of simulation repeats necessary to obtain convergence of simple descriptors of the mode of packing of the two helices within a dimer. Our approach offers a proof-of-principle platform for the further employment of automation in large ensemble CGMD simulations of membrane proteins.
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Affiliation(s)
- Benjamin A Hall
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
| | | | - Amanda Buyan
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Beatrice Emmanouil
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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13
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14
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Activation of the bacterial thermosensor DesK involves a serine zipper dimerization motif that is modulated by bilayer thickness. Proc Natl Acad Sci U S A 2015; 112:6353-8. [PMID: 25941408 DOI: 10.1073/pnas.1422446112] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
DesK is a bacterial thermosensor protein involved in maintaining membrane fluidity in response to changes in environmental temperature. Most likely, the protein is activated by changes in membrane thickness, but the molecular mechanism of sensing and signaling is still poorly understood. Here we aimed to elucidate the mode of action of DesK by studying the so-called "minimal sensor DesK" (MS-DesK), in which sensing and signaling are captured in a single transmembrane segment. This simplified version of the sensor allows investigation of membrane thickness-dependent protein-lipid interactions simply by using synthetic peptides, corresponding to the membrane-spanning parts of functional and nonfunctional mutants of MS-DesK incorporated in lipid bilayers with varying thicknesses. The lipid-dependent behavior of the peptides was investigated by circular dichroism, tryptophan fluorescence, and molecular modeling. These experiments were complemented with in vivo functional studies on MS-DesK mutants. Based on the results, we constructed a model that suggests a new mechanism for sensing in which the protein is present as a dimer and responds to an increase in bilayer thickness by membrane incorporation of a C-terminal hydrophilic motif. This results in exposure of three serines on the same side of the transmembrane helices of MS-DesK, triggering a switching of the dimerization interface to allow the formation of a serine zipper. The final result is activation of the kinase state of MS-DesK.
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15
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Schmidt T, Suk JE, Ye F, Situ AJ, Mazumder P, Ginsberg MH, Ulmer TS. Annular anionic lipids stabilize the integrin αIIbβ3 transmembrane complex. J Biol Chem 2015; 290:8283-93. [PMID: 25632962 DOI: 10.1074/jbc.m114.623504] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cationic membrane-proximal amino acids determine the topology of membrane proteins by interacting with anionic lipids that are restricted to the intracellular membrane leaflet. This mechanism implies that anionic lipids interfere with electrostatic interactions of membrane proteins. The integrin αIIbβ3 transmembrane (TM) complex is stabilized by a membrane-proximal αIIb(Arg(995))-β3(Asp(723)) interaction; here, we examine the influence of anionic lipids on this complex. Anionic lipids compete for αIIb(Arg(995)) contacts with β3(Asp(723)) but paradoxically do not diminish the contribution of αIIb(Arg(995))-β3(Asp(723)) to TM complex stability. Overall, anionic lipids in annular positions stabilize the αIIbβ3 TM complex by up to 0.50 ± 0.02 kcal/mol relative to zwitterionic lipids in a headgroup structure-dependent manner. Comparatively, integrin receptor activation requires TM complex destabilization of 1.5 ± 0.2 kcal/mol, revealing a sizeable influence of lipid composition on TM complex stability. We implicate changes in lipid headgroup accessibility to small molecules (physical membrane characteristics) and specific but dynamic protein-lipid contacts in this TM helix-helix stabilization. Thus, anionic lipids in ubiquitous annular positions can benefit the stability of membrane proteins while leaving membrane-proximal electrostatic interactions intact.
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Affiliation(s)
- Thomas Schmidt
- From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | - Jae-Eun Suk
- From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | - Feng Ye
- the Department of Medicine, University of California San Diego, La Jolla, California 92093
| | - Alan J Situ
- From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | - Parichita Mazumder
- From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | - Mark H Ginsberg
- the Department of Medicine, University of California San Diego, La Jolla, California 92093
| | - Tobias S Ulmer
- From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
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16
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Shamloo A, Nikbin E, Mehboudi N, Damirchi B. Homo-oligomerization of transmembrane α-domain of integrin. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:1162-5. [PMID: 25570170 DOI: 10.1109/embc.2014.6943802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Integrins contribute to form focal adhesions complex. Therefore, simulation of integrin interactions can be helpful in clarifying the mechanism of focal adhesion formation. Interactions of integrins can also initiate signal transduction in the focal adhesions. Since integrins contain α and β subunits that are separated in an active state, studying both subunits separately is crucial, since, in the active state of integrins, the distance between these subunits is long enough that they do not influence one another significantly. Thus, this study aims to investigate the tendency of α subunits of integrins to form homodimers. All simulations were carried out via MARTINI coarse grain (CG) molecular dynamics technique. α subunits were placed in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer at a distance of 5 nm, and they were allowed to diffuse in the lipid bilayer. All simulations showed that α subunits have a tendency to form stable dimers.
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17
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Pawar AB, Deshpande SA, Gopal SM, Wassenaar TA, Athale CA, Sengupta D. Thermodynamic and kinetic characterization of transmembrane helix association. Phys Chem Chem Phys 2015; 17:1390-8. [DOI: 10.1039/c4cp03732d] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The transient dimerization of transmembrane proteins is an important event in several cellular processes and here we use coarse-grain and meso-scale modeling methods to quantify their underlying dynamics.
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Affiliation(s)
| | | | | | - Tsjerk A. Wassenaar
- Department of Biology
- Computational Biology
- University of Erlangen-Nürnberg
- 91058 Erlangen
- Germany
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18
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Koldsø H, Shorthouse D, Hélie J, Sansom MSP. Lipid clustering correlates with membrane curvature as revealed by molecular simulations of complex lipid bilayers. PLoS Comput Biol 2014; 10:e1003911. [PMID: 25340788 PMCID: PMC4207469 DOI: 10.1371/journal.pcbi.1003911] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 09/16/2014] [Indexed: 12/21/2022] Open
Abstract
Cell membranes are complex multicomponent systems, which are highly heterogeneous in the lipid distribution and composition. To date, most molecular simulations have focussed on relatively simple lipid compositions, helping to inform our understanding of in vitro experimental studies. Here we describe on simulations of complex asymmetric plasma membrane model, which contains seven different lipids species including the glycolipid GM3 in the outer leaflet and the anionic lipid, phosphatidylinositol 4,5-bisphophate (PIP2), in the inner leaflet. Plasma membrane models consisting of 1500 lipids and resembling the in vivo composition were constructed and simulations were run for 5 µs. In these simulations the most striking feature was the formation of nano-clusters of GM3 within the outer leaflet. In simulations of protein interactions within a plasma membrane model, GM3, PIP2, and cholesterol all formed favorable interactions with the model α-helical protein. A larger scale simulation of a model plasma membrane containing 6000 lipid molecules revealed correlations between curvature of the bilayer surface and clustering of lipid molecules. In particular, the concave (when viewed from the extracellular side) regions of the bilayer surface were locally enriched in GM3. In summary, these simulations explore the nanoscale dynamics of model bilayers which mimic the in vivo lipid composition of mammalian plasma membranes, revealing emergent nanoscale membrane organization which may be coupled both to fluctuations in local membrane geometry and to interactions with proteins. Cell membranes play important roles in vivo both in shielding the cell interior from the surrounding environment and in cell function through lipid components of the membrane having roles in controlling protein function, cell signaling etc. We employ molecular dynamics simulations to explore the behavior of biologically realistic membrane models. Our simulations reveal nano-domain clustering of the glycolipid GM3 and to a lesser extent of the anionic lipid phosphatidylinositol 4,5-bisphophate (PIP2). When including transmembrane proteins we are able to observe preferential interactions of known regulatory lipids (e.g. GM3, PIP2 and cholesterol) with the proteins. Membrane curvature is shown to be coupled to the local lipid composition, suggestive of a link between lipid nano-domains and membrane geometry.
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Affiliation(s)
- Heidi Koldsø
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David Shorthouse
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Jean Hélie
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- * E-mail:
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19
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Chavent M, Chetwynd AP, Stansfeld PJ, Sansom MSP. Dimerization of the EphA1 receptor tyrosine kinase transmembrane domain: Insights into the mechanism of receptor activation. Biochemistry 2014; 53:6641-52. [PMID: 25286141 PMCID: PMC4298228 DOI: 10.1021/bi500800x] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
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EphA1
is a receptor tyrosine kinase (RTK) that plays a key role
in developmental processes, including guidance of the migration of
axons and cells in the nervous system. EphA1, in common with other
RTKs, contains an N-terminal extracellular domain, a single transmembrane
(TM) α-helix, and a C-terminal intracellular kinase domain.
The TM helix forms a dimer, as seen in recent NMR studies. We have
modeled the EphA1 TM dimer using a multiscale approach combining coarse-grain
(CG) and atomistic molecular dynamics (MD) simulations. The one-dimensional
potential of mean force (PMF) for this system, based on interhelix
separation, has been calculated using CG MD simulations. This provides
a view of the free energy landscape for helix–helix interactions
of the TM dimer in a lipid bilayer. The resulting PMF profiles suggest
two states, consistent with a rotation-coupled activation mechanism.
The more stable state corresponds to a right-handed helix dimer interacting
via an N-terminal glycine zipper motif, consistent with a recent NMR
structure (2K1K). A second metastable state corresponds to a structure in which
the glycine zipper motif is not involved. Analysis of unrestrained
CG MD simulations based on representative models from the PMF calculations
or on the NMR structure reveals possible pathways of interconversion
between these two states, involving helix rotations about their long
axes. This suggests that the interaction of TM helices in EphA1 dimers
may be intrinsically dynamic. This provides a potential mechanism
for signaling whereby extracellular events drive a shift in the repopulation
of the underlying TM helix dimer energy landscape.
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Affiliation(s)
- Matthieu Chavent
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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20
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Reddy T, Manrique S, Buyan A, Hall BA, Chetwynd A, Sansom MSP. Primary and secondary dimer interfaces of the fibroblast growth factor receptor 3 transmembrane domain: characterization via multiscale molecular dynamics simulations. Biochemistry 2014; 53:323-32. [PMID: 24397339 DOI: 10.1021/bi401576k] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Receptor tyrosine kinases are single-pass membrane proteins that form dimers within the membrane. The interactions of their transmembrane domains (TMDs) play a key role in dimerization and signaling. Fibroblast growth factor receptor 3 (FGFR3) is of interest as a G380R mutation in its TMD is the underlying cause of ~99% of the cases of achondroplasia, the most common form of human dwarfism. The structural consequences of this mutation remain uncertain: the mutation shifts the position of the TMD relative to the lipid bilayer but does not alter the association free energy. We have combined coarse-grained and all-atom molecular dynamics simulations to study the dimerization of wild-type, heterodimer, and mutant FGFR3 TMDs. The simulations reveal that the helices pack together in the dimer to form a flexible interface. The primary packing mode is mediated by a Gx3G motif. There is also a secondary dimer interface that is more highly populated in heterodimer and mutant configurations that may feature in the molecular mechanism of pathology. Both coarse-grained and atomistic simulations reveal a significant shift of the G380R mutant dimer TMD relative to the bilayer to allow interactions of the arginine side chain with lipid headgroup phosphates.
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Affiliation(s)
- Tyler Reddy
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, U.K
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21
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22
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Kalli AC, Campbell ID, Sansom MSP. Conformational changes in talin on binding to anionic phospholipid membranes facilitate signaling by integrin transmembrane helices. PLoS Comput Biol 2013; 9:e1003316. [PMID: 24204243 PMCID: PMC3814715 DOI: 10.1371/journal.pcbi.1003316] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Accepted: 09/19/2013] [Indexed: 01/01/2023] Open
Abstract
Integrins are heterodimeric (αβ) cell surface receptors that are activated to a high affinity state by the formation of a complex involving the α/β integrin transmembrane helix dimer, the head domain of talin (a cytoplasmic protein that links integrins to actin), and the membrane. The talin head domain contains four sub-domains (F0, F1, F2 and F3) with a long cationic loop inserted in the F1 domain. Here, we model the binding and interactions of the complete talin head domain with a phospholipid bilayer, using multiscale molecular dynamics simulations. The role of the inserted F1 loop, which is missing from the crystal structure of the talin head, PDB:3IVF, is explored. The results show that the talin head domain binds to the membrane predominantly via cationic regions on the F2 and F3 subdomains and the F1 loop. Upon binding, the intact talin head adopts a novel V-shaped conformation which optimizes its interactions with the membrane. Simulations of the complex of talin with the integrin α/β TM helix dimer in a membrane, show how this complex promotes a rearrangement, and eventual dissociation of, the integrin α and β transmembrane helices. A model for the talin-mediated integrin activation is proposed which describes how the mutual interplay of interactions between transmembrane helices, the cytoplasmic talin protein, and the lipid bilayer promotes integrin inside-out activation. Transmission of signals across the cell membrane is an essential process for all living organisms. Integrins are one example of cell surface receptors (αβ) which, uniquely, form a bidirectional signalling pathway across the membrane. Integrins are crucial for many cellular processes and play key roles in pathological defects such as cardiovascular diseases and cancer. They are activated to a high affinity state by the intracellular protein talin in a process known as ‘inside-out activation’. Despite their importance and the existence of functional and structural data, the mechanism by which talin activates integrin remains elusive. In this study we use a multi-scale computational approach, which combines coarse-grained and atomistic molecular dynamics simulations, to suggest how the formation of the complex between the talin head domain, the cell membrane and the integrin moves the integrin equilibrium towards an active state. Our results show that conformational changes within the talin head domains optimize its interactions with the cell membrane. Upon binding to the integrin, talin facilitates rearrangement of the integrin TM region thus promoting integrin activation. This study also provides a demonstration of the strengths of a computational multi-scale approach in studies of membrane interactions and receptor conformational changes and associated proteins that enable transmembrane signaling.
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Affiliation(s)
- Antreas C. Kalli
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Iain D. Campbell
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- * E-mail:
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23
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Localized lipid packing of transmembrane domains impedes integrin clustering. PLoS Comput Biol 2013; 9:e1002948. [PMID: 23516344 PMCID: PMC3597534 DOI: 10.1371/journal.pcbi.1002948] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 01/11/2013] [Indexed: 12/12/2022] Open
Abstract
Integrin clustering plays a pivotal role in a host of cell functions. Hetero-dimeric integrin adhesion receptors regulate cell migration, survival, and differentiation by communicating signals bidirectionally across the plasma membrane. Thus far, crystallographic structures of integrin components are solved only separately, and for some integrin types. Also, the sequence of interactions that leads to signal transduction remains ambiguous. Particularly, it remains controversial whether the homo-dimerization of integrin transmembrane domains occurs following the integrin activation (i.e. when integrin ectodomain is stretched out) or if it regulates integrin clustering. This study employs molecular dynamics modeling approaches to address these questions in molecular details and sheds light on the crucial effect of the plasma membrane. Conducting a normal mode analysis of the intact αllbβ3 integrin, it is demonstrated that the ectodomain and transmembrane-cytoplasmic domains are connected via a membrane-proximal hinge region, thus merely transmembrane-cytoplasmic domains are modeled. By measuring the free energy change and force required to form integrin homo-oligomers, this study suggests that the β-subunit homo-oligomerization potentially regulates integrin clustering, as opposed to α-subunit, which appears to be a poor regulator for the clustering process. If α-subunits are to regulate the clustering they should overcome a high-energy barrier formed by a stable lipid pack around them. Finally, an outside-in activation-clustering scenario is speculated, explaining how further loading the already-active integrin affects its homo-oligomerization so that focal adhesions grow in size. Focal adhesions are complex, dynamic structures of multiple proteins that act as the cell's mechanical anchorage to its surrounding. Integrins are proteins linking the cell inner and outer environments, which act as a bridge that crosses the cell membrane. Integrins respond to mechanical loads exerted to them by changing their conformations. Several diseases, such as atherosclerosis and different types of cancer, are caused by altered function of integrins. Essential to the formation of focal adhesions is the process of integrin clustering. Bidirectional integrin signaling involves conformational changes in this protein, clustering, and finally the assembly of a large intracellular adhesion complex. Integrin clustering is defined as the interaction of integrins to form lateral assemblies that eventually lead to focal adhesion formation. The effect of the plasma membrane on formation of integrin clusters has been largely neglected in current literature; subsequently some apparently contradictory data has been reported by a number of researchers in the field. Using a molecular dynamics modeling approach, a computational method that simulates systems in a full-atomic scale, we probe the role of the plasma membrane in integrin clustering and hypothesize a clustering scenario that explains the relationship between integrin activation and focal adhesion growth.
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24
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Sharma S, Juffer AH. An atomistic model for assembly of transmembrane domain of T cell receptor complex. J Am Chem Soc 2013; 135:2188-97. [PMID: 23320396 DOI: 10.1021/ja308413e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The T cell receptor (TCR) together with accessory cluster of differentiation 3 (CD3) molecules (TCR-CD3 complex) is a key component in the primary function of T cells. The nature of association of the transmembrane domains is of central importance to the assembly of the complex and is largely unknown. Using multiscale molecular modeling and simulations, we have investigated the structure and assembly of the TCRα-CD3ε-CD3δ transmembrane domains both in membrane and in micelle environments. We demonstrate that in a membrane environment the transmembrane basic residue of the TCR closely interacts with both of the transmembrane acidic residues of the CD3 dimer. In contrast, in a micelle the basic residue interacts with only one of the acidic residues. Simulations of a recent micellar nuclear magnetic resonance structure of the natural killer (NK) cell-activating NKG2C-DAP12-DAP12 trimer in a membrane further indicate that the environment significantly affects the way these trimers associate. Since the currently accepted model for transmembrane association is entirely based on a micellar structure, we propose a revised model for the association of transmembrane domains of the activating immune receptors in a membrane environment.
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Affiliation(s)
- Satyan Sharma
- Biocenter Oulu and Department of Biochemistry, University of Oulu, P.O. Box 3000, Oulu FI-90014, Finland
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25
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Ulmschneider JP, Smith JC, Ulmschneider MB, Ulrich AS, Strandberg E. Reorientation and dimerization of the membrane-bound antimicrobial peptide PGLa from microsecond all-atom MD simulations. Biophys J 2013; 103:472-482. [PMID: 22947863 DOI: 10.1016/j.bpj.2012.06.040] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/27/2012] [Accepted: 06/28/2012] [Indexed: 10/28/2022] Open
Abstract
The membrane-active antimicrobial peptide PGLa from Xenopus laevis is known from solid-state (2)H-, (15)N-, and (19)F-NMR spectroscopy to occupy two distinct α-helical surface adsorbed states in membranes: a surface-bound S-state with a tilt angle of ~95° at low peptide/lipid molar ratio (P/L = 1:200), and an obliquely tilted T-state with a tilt angle of 127° at higher peptide concentration (P/L = 1:50). Using a rapid molecular-dynamics insertion protocol in combination with microsecond-scale simulation, we have characterized the structure of both states in detail. As expected, the amphiphilic peptide resides horizontally on the membrane surface in a monomeric form at a low P/L, whereas the T-state is seen in the simulations to be a symmetric antiparallel dimer, with close contacts between small glycine and alanine residues at the interface. The computed tilt angles and azimuthal rotations, as well as the quadrupolar splittings predicted from the simulations agree with the experimental NMR data. The simulations reveal many structural details previously inaccessible, such as the immersion depth of the peptide in the membrane and the packing of the dimerization interface. The study highlights the ability and limitations of current state-of-the-art multimicrosecond all-atom simulations of membrane-active peptides to complement experimental data from solid-state NMR.
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Affiliation(s)
| | | | | | - Anne S Ulrich
- Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, Karlsruhe, Germany; Institute of Organic Chemistry and CFN, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Erik Strandberg
- Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, Karlsruhe, Germany
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26
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27
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Reddy T, Rainey JK. Multifaceted Substrate Capture Scheme of a Rhomboid Protease. J Phys Chem B 2012; 116:8942-54. [DOI: 10.1021/jp305077k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tyler Reddy
- Department of Biochemistry & Molecular Biology and ‡Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Jan K. Rainey
- Department of Biochemistry & Molecular Biology and ‡Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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28
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Parton DL, Akhmatskaya EV, Sansom MSP. Multiscale simulations of the antimicrobial peptide maculatin 1.1: water permeation through disordered aggregates. J Phys Chem B 2012; 116:8485-93. [PMID: 22380536 DOI: 10.1021/jp212358y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The antimicrobial peptide maculatin 1.1 (M1.1) is an amphipathic α-helix that permeabilizes lipid bilayers. In coarse-grained molecular dynamics (CG MD) simulations, M1.1 has previously been shown to form membrane-spanning aggregates in DPPC bilayers. In this study, a simple multiscale methodology has been applied to allow sampling of important regions of the free energy surface at higher resolution. Thus, by back-converting the CG configurations to atomistic representations, it is shown that water is able to permeate through the M1.1 aggregates. Investigation of aggregate stoichiometry shows that at least six peptides are required for water permeation. The aggregates are dynamically disordered structures, and water flux occurs through irregular, fluctuating channels. The results are discussed in relation to experimental data and other simulations of antimicrobial peptides.
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Affiliation(s)
- Daniel L Parton
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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29
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Stansfeld P, Sansom M. Molecular Simulation Approaches to Membrane Proteins. Structure 2011; 19:1562-72. [DOI: 10.1016/j.str.2011.10.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/29/2011] [Accepted: 10/03/2011] [Indexed: 11/17/2022]
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