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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. [PMID: 38682753 DOI: 10.1002/cm.21865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [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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Labus J, Tang K, Henklein P, Krüger U, Hofmann A, Hondke S, Wöltje K, Freund C, Lucka L, Danker K. The α 1 integrin cytoplasmic tail interacts with phosphoinositides and interferes with Akt activation. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184257. [PMID: 37992949 DOI: 10.1016/j.bbamem.2023.184257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 11/03/2023] [Accepted: 11/14/2023] [Indexed: 11/24/2023]
Abstract
Integrin α1β1 is an adhesion receptor that binds to collagen and laminin. It regulates cell adhesion, cytoskeletal organization, and migration. The cytoplasmic tail of the α1 subunit consists of 15 amino acids and contains six positively charged lysine residues. In this study, we present evidence that the α1 integrin cytoplasmic tail (α1CT) directly associates with phosphoinositides, preferentially with phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3). Since the association was disrupted by calcium, magnesium and phosphate ions, this interaction appears to be in ionic nature. Here, the peptide-lipid interaction was driven by the conserved KIGFFKR motif. The exchange of both two potential phospholipid-binding lysines for glycines in the KIGFFKR motif increased α1β1 integrin-specific adhesion and F-actin cytoskeleton formation compared to cells expressing the unmodified α1 subunit, whereas only mutation of the second lysine at position 1171 increased levels of constitutively active α1β1 integrins on the cell surface. In addition, enhanced focal adhesion formation and increased phosphorylation of focal adhesion kinase, but decreased phosphorylation of AKT was observed in these cells. We conclude that the KIGFFKR motif, and in particular lysine1171 is involved in the dynamic regulation of α1β1 integrin activity and that the interaction of α1CT with phosphoinositides may contribute to this process.
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Affiliation(s)
- Josephine Labus
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany; Hannover Medical School, Department of Cellular Neurophysiology, 30625 Hannover, Germany.
| | - Kerstin Tang
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany; Senate Department for Higher Education and Research, Health, Long-Term Care and Gender Equality, Sector Pharmaceuticals and Medical Devices, Oranienstraße 106, 10969 Berlin, Germany.
| | - Petra Henklein
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany.
| | - Ulrike Krüger
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany; BIH Core Facility Genomik, Charité-Universitätsmedizin Berlin, CVK, Charitéplatz 1, 10117 Berlin, Germany.
| | - Andreas Hofmann
- Structural Chemistry Program, Griffith Institute for Drug Discovery, Griffith University, Brisbane, Queensland 4111, Australia; Dept of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia; NRZ-Authent, Max-Rubner-Institut, Bundesforschungsinstitut für Ernährung und Lebensmittel, E.-C.-Baumann-Str. 20, 95326 Kulmbach, Germany.
| | - Sylvia Hondke
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany
| | - Kerstin Wöltje
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany; Charité-Universitätsmedizin Berlin, Med. Klinik m.S. Infektiologie & Pneumologie, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Christian Freund
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany.
| | - Lothar Lucka
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany.
| | - Kerstin Danker
- Institute for Biochemistry, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany.
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3
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Nakayama M, Goto S, Goto S. Development of the Integrated Computer Simulation Model of the Intracellular, Transmembrane, and Extracellular Domain of Platelet Integrin α IIb β 3 (Platelet Membrane Glycoprotein: GPIIb-IIIa). TH OPEN 2024; 8:e96-e105. [PMID: 38425453 PMCID: PMC10904213 DOI: 10.1055/a-2247-9438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 01/04/2024] [Indexed: 03/02/2024] Open
Abstract
Background The structure and functions of the extracellular domain of platelet integrin α IIb β 3 (platelet membrane glycoprotein: GPIIb-IIIa) change substantially upon platelet activation. However, the stability of the integrated model of extracellular/transmembrane/intracellular domains of integrin α IIb β 3 with the inactive state of the extracellular domain has not been clarified. Methods The integrated model of integrin α IIb β 3 was developed by combining the extracellular domain adopted from the crystal structure and the transmembrane and intracellular domain obtained by Nuclear Magnetic Resonace (NMR). The transmembrane domain was settled into the phosphatidylcholine (2-oleoyl-1-palmitoyl-sn-glycerol-3-phosphocholine (POPC)) lipid bilayer model. The position coordinates and velocity vectors of all atoms and water molecules around them were calculated by molecular dynamic (MD) simulation with the use of Chemistry at Harvard Macromolecular Mechanics force field in every 2 × 10 -15 seconds. Results The root-mean-square deviations (RMSDs) of atoms constructing the integrated α IIb β 3 model apparently stabilized at approximately 23 Å after 200 ns of calculation. However, minor fluctuation persisted during the entire calculation period of 650 ns. The RMSDs of both α IIb and β 3 showed similar trends before 200 ns. The RMSD of β 3 apparently stabilized approximately at 15 Å at 400 ns with persisting minor fluctuation afterward, while the structural fluctuation in α IIb persisted throughout the 650 ns calculation period. Conclusion In conclusion, the integrated model of the intracellular, transmembrane, and extracellular domain of integrin α IIb β 3 suggested persisting fluctuation even after convergence of MD calculation.
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Affiliation(s)
- Masamitsu Nakayama
- Department of Medicine (Cardiology), Tokai University School of Medicine, Isehara, Japan
| | - Shinichi Goto
- Department of Medicine (Cardiology), Tokai University School of Medicine, Isehara, Japan
| | - Shinya Goto
- Department of Medicine (Cardiology), Tokai University School of Medicine, Isehara, Japan
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Situ AJ, Ulmer TS. Comparison of Integrin αIIbβ3 Transmembrane Association in Vesicles and Bicelles. Biochemistry 2023. [PMID: 37279176 DOI: 10.1021/acs.biochem.3c00177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Membrane proteins are commonly reconstituted in membrane mimics exhibiting discontinuous lipid bilayers. In contrast, the continuous membranes of cells are conceptually best represented by large unilamellar vesicles (LUVs). Here, we compared the thermodynamic stability of the integrin αIIbβ3 transmembrane (TM) complex between vesicles and bicelles to assess the consequence of this simplification. In LUVs, we further evaluated the strength of the αIIb(G972S)-β3(V700T) interaction that corresponds to the hydrogen bond interaction postulated for β2 integrins. An upper limit of 0.9 kcal/mol was estimated for superior TM complex stabilization in LUVs relative to bicelles. Compared to the αIIbβ3 TM complex stability in LUVs of 5.6 ± 0.2 kcal/mol, this limit is modest, indicating that bicelles performed well relative to LUVs. The implementation of β3(V700T) alleviated αIIb(G972S) destabilization by 0.4 ± 0.2 kcal/mol in confirmation of relatively weak hydrogen bonding. Interestingly, the hydrogen bond adjusts the TM complex stability to a level that is not achievable by merely varying the residue corresponding to αIIb(Gly972).
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Affiliation(s)
- Alan J Situ
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, United States
| | - Tobias S Ulmer
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, United States
- Department of Biochemistry and Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, United States
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Xin H, Huang J, Song Z, Mao J, Xi X, Shi X. Structure, signal transduction, activation, and inhibition of integrin αIIbβ3. Thromb J 2023; 21:18. [PMID: 36782235 PMCID: PMC9923933 DOI: 10.1186/s12959-023-00463-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 02/06/2023] [Indexed: 02/15/2023] Open
Abstract
Integrins are heterodimeric receptors comprising α and β subunits. They are expressed on the cell surface and play key roles in cell adhesion, migration, and growth. Several types of integrins are expressed on the platelets, including αvβ3, αIIbβ3, α2β1, α5β1, and α6β1. Among these, physically αIIbβ3 is exclusively expressed on the platelet surface and their precursor cells, megakaryocytes. αIIbβ3 adopts at least three conformations: i) bent-closed, ii) extended-closed, and iii) extended-open. The transition from conformation i) to iii) occurs when αIIbβ3 is activated by stimulants. Conformation iii) possesses a high ligand affinity, which triggers integrin clustering and platelet aggregation. Platelets are indispensable for maintaining vascular system integrity and preventing bleeding. However, excessive platelet activation can result in myocardial infarction (MI) and stroke. Therefore, finding a novel strategy to stop bleeding without accelerating the risk of thrombosis is important. Regulation of αIIbβ3 activation is vital for this strategy. There are a large number of molecules that facilitate or inhibit αIIbβ3 activation. The interference of these molecules can accurately control the balance between hemostasis and thrombosis. This review describes the structure and signal transduction of αIIbβ3, summarizes the molecules that directly or indirectly affect integrin αIIbβ3 activation, and discusses some novel antiαIIbβ3 drugs. This will advance our understanding of the activation of αIIbβ3 and its essential role in platelet function and tumor development.
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Affiliation(s)
- Honglei Xin
- grid.452511.6Department of Hematology, Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210003 China
| | - Jiansong Huang
- grid.13402.340000 0004 1759 700XDepartment of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang, Hangzhou 310003 China ,grid.412277.50000 0004 1760 6738Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025 China
| | - Zhiqun Song
- grid.412676.00000 0004 1799 0784Jiangsu Province People’s Hospital and Nanjing Medical University First Affiliated Hospital, Nanjing, Jiangsu 210029 China
| | - Jianhua Mao
- grid.412277.50000 0004 1760 6738Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025 China
| | - Xiaodong Xi
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
| | - Xiaofeng Shi
- Department of Hematology, Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210003, China. .,Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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6
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Tong D, Soley N, Kolasangiani R, Schwartz MA, Bidone TC. Integrin α IIbβ 3 intermediates: From molecular dynamics to adhesion assembly. Biophys J 2023; 122:533-543. [PMID: 36566352 PMCID: PMC9941721 DOI: 10.1016/j.bpj.2022.12.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 08/14/2022] [Accepted: 12/21/2022] [Indexed: 12/25/2022] Open
Abstract
The platelet integrin αIIbβ3 undergoes long-range conformational transitions associated with its functional conversion from inactive (low-affinity) to active (high-affinity) during hemostasis. Although new conformations that are intermediate between the well-characterized bent and extended states have been identified, their molecular dynamic properties and functions in the assembly of adhesions remain largely unexplored. In this study, we evaluated the properties of intermediate conformations of integrin αIIbβ3 and characterized their effects on the assembly of adhesions by combining all-atom simulations, principal component analysis, and mesoscale modeling. Our results show that in the low-affinity, bent conformation, the integrin ectodomain tends to pivot around the legs; in intermediate conformations, the headpiece becomes partially extended, away from the lower legs. In the fully open, active state, αIIbβ3 is flexible, and the motions between headpiece and lower legs are accompanied by fluctuations of the transmembrane helices. At the mesoscale, bent integrins form only unstable adhesions, but intermediate or open conformations stabilize the adhesions. These studies reveal a mechanism by which small variations in ligand binding affinity and enhancement of the ligand-bound lifetime in the presence of actin retrograde flow stabilize αIIbβ3 integrin adhesions.
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Affiliation(s)
- Dudu Tong
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah
| | - Nidhi Soley
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah
| | - Reza Kolasangiani
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah
| | - Martin A Schwartz
- Yale Cardiovascular Research Center, Department of Internal Medicine (Cardiology), Yale University, New Haven, Connecticut; Department of Cell Biology, Yale University, New Haven, Connecticut; Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University, New Haven, Connecticut
| | - Tamara C Bidone
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah; Department of Biochemistry, University of Utah, Salt Lake City, Utah; Department of Molecular Pharmaceutics, University of Utah, Salt Lake City, Utah.
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7
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Isothermal Titration Calorimetry of Membrane Proteins. Methods Mol Biol 2021. [PMID: 33877623 DOI: 10.1007/978-1-0716-1394-8_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The ability to quantify protein-protein interactions without adding labels to protein has made isothermal titration calorimetry (ITC) a preferred technique to study proteins in aqueous solution. Here, we describe the application of ITC to the study of protein-protein interactions in membrane mimics using the association of integrin αIIb and β3 transmembrane domains in phospholipid bicelles as an example. A higher conceptual and experimental effort compared to water-soluble proteins is required for membrane proteins and rewarded with rare thermodynamic insight into this central class of proteins.
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8
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Situ AJ, Kim J, An W, Kim C, Ulmer TS. Insight Into Pathological Integrin αIIbβ3 Activation From Safeguarding The Inactive State. J Mol Biol 2021; 433:166832. [PMID: 33539882 PMCID: PMC11025565 DOI: 10.1016/j.jmb.2021.166832] [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: 12/02/2020] [Revised: 01/01/2021] [Accepted: 01/12/2021] [Indexed: 11/20/2022]
Abstract
The inhibition of physiological activation pathways of the platelet adhesion receptor integrin αIIbβ3 may fail to prevent fatal thrombosis, suggesting that the receptor is at risk of activation by yet an unidentified pathway. Here, we report the discovery and characterization of a structural motif that safeguards the receptor by selectively destabilizing its inactive state. At the extracellular membrane border, an overpacked αIIb(W968)-β3(I693) contact prevents αIIb(Gly972) from optimally assembling the αIIbβ3 transmembrane complex, which maintains the inactive state. This destabilization of approximately 1.0 kcal/mol could be mitigated by hydrodynamic forces but not physiological agonists, thereby identifying hydrodynamic forces as pathological activation stimulus. As reproductive life spans are not generally limited by cardiovascular disease, it appears that the evolution of the safeguard was driven by fatal, hydrodynamic force-mediated integrin αIIbβ3 activation in the healthy cardiovascular system. The triggering of the safeguard solely by pathological stimuli achieves an effective increase of the free energy barrier between inactive and active receptor states without incurring an increased risk of bleeding. Thus, integrin αIIbβ3 has evolved an effective way to protect receptor functional states that indicates the availability of a mechanical activation pathway when hydrodynamic forces exceed physiological margins.
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Affiliation(s)
- Alan J Situ
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Jiyoon Kim
- Department of Life Sciences, Korea University, Seoul, Republic of Korea
| | - Woojin An
- Department of Biochemistry and Molecular Medicine, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA, USA
| | - Chungho Kim
- Department of Life Sciences, Korea University, Seoul, Republic of Korea.
| | - Tobias S Ulmer
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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9
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Lietha D, Izard T. Roles of Membrane Domains in Integrin-Mediated Cell Adhesion. Int J Mol Sci 2020; 21:ijms21155531. [PMID: 32752284 PMCID: PMC7432473 DOI: 10.3390/ijms21155531] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 12/13/2022] Open
Abstract
The composition and organization of the plasma membrane play important functional and regulatory roles in integrin signaling, which direct many physiological and pathological processes, such as development, wound healing, immunity, thrombosis, and cancer metastasis. Membranes are comprised of regions that are thick or thin owing to spontaneous partitioning of long-chain saturated lipids from short-chain polyunsaturated lipids into domains defined as ordered and liquid-disorder domains, respectively. Liquid-ordered domains are typically 100 nm in diameter and sometimes referred to as lipid rafts. We posit that integrin β senses membrane thickness and that mechanical force on the membrane regulates integrin activation through membrane thinning. This review examines what we know about the nature and mechanism of the interaction of integrins with the plasma membrane and its effects on regulating integrins and its binding partners.
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Affiliation(s)
- Daniel Lietha
- Cell Signaling and Adhesion Group, Structural and Chemical Biology, Margarita Salas Center for Biological Research (CIB-CSIC), E-28040 Madrid, Spain;
| | - Tina Izard
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, FL 33458, USA
- Correspondence:
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Dubey V, Mishra AK, Ghosh AR. Cell adherence efficacy of probiotic Pediococcus pentosaceus GS4 (MTCC 12683) and demonstrable role of its surface layer protein (Slp). J Proteomics 2020; 226:103894. [PMID: 32652219 DOI: 10.1016/j.jprot.2020.103894] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 06/08/2020] [Accepted: 07/06/2020] [Indexed: 12/16/2022]
Abstract
The current study examined the cell adherence property of probiotic Pediococcus pentosaceus GS4 (MTCC12683) with the characterization and functionality in adherence of its surface layer protein (GS4-Slp). The Slp of P. pentosaceus GS4 was extracted purified and detected using SDS-PAGE (98 kDa) and size exclusion chromatography. The cell adherence property of probiotic GS4 (Slp+/Slp-) was evaluated on buccal cells and HCT-116. Purified Slp was found neutralized with raised anti-Slp showing reduced adherence to HCT-116 as evident from SEM analysis. The structure of GS4-Slp was determined by MALDI-TOF analysis, CD analysis, atomic force microscopy (AFM), and FT-IR spectrometry. In Silico approach revealed its indirect similarity with cell membrane protein of Helicobacter pylori. Results thus reveal that GS4 has the potential of the production of 98 kDa Slp which facilitates the cell adherence property. This added probiotic attribute will enhance the probiotic potentials of P. pentosaceus GS4 to use it biotechnologically. SIGNIFICANCE: Probiotic Pediococcus pentosaceus GS4 facilitates demonstrable colonization by the elaboration of Slp. This property imparts a value to the strain and claims to be more useful biotechnologically.
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Affiliation(s)
- Vinay Dubey
- Department of Integrative Biology, School of BioSciences and Technology, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India
| | - Alok Kumar Mishra
- Department of Integrative Biology, School of BioSciences and Technology, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India
| | - Asit Ranjan Ghosh
- Department of Integrative Biology, School of BioSciences and Technology, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India.
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11
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Rohena C, Kalogriopoulos N, Rajapakse N, Roy S, Lopez-Sanchez I, Ablack J, Sahoo D, Ghosh P. GIV•Kindlin Interaction Is Required for Kindlin-Mediated Integrin Recognition and Activation. iScience 2020; 23:101209. [PMID: 32535026 PMCID: PMC7300163 DOI: 10.1016/j.isci.2020.101209] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 04/15/2020] [Accepted: 05/24/2020] [Indexed: 11/16/2022] Open
Abstract
Cells perceive and respond to the extracellular matrix via integrin receptors; their dysregulation has been implicated in inflammation and cancer metastasis. Here we show that a guanine nucleotide-exchange modulator of trimeric-GTPase Gαi, GIV (a.k.a Girdin), directly binds the integrin adaptor Kindlin-2. A non-canonical short linear motif within the C terminus of GIV binds Kindlin-2-FERM3 domain at a site that is distinct from the binding site for the canonical NPxY motif on the -integrin tail. Binding of GIV to Kindlin-2 allosterically enhances Kindlin-2's affinity for β1-integrin. Consequently, integrin activation and clustering are maximized, which augments cell adhesion, spreading, and invasion. Findings elucidate how the GIV•Kindlin-2 complex has a 2-fold impact: it allosterically synergizes integrin activation and enables β1-integrins to indirectly access and modulate trimeric GTPases via the complex. Furthermore, Cox proportional-hazard models on tumor transcriptomics provide trans-scale evidence of synergistic interactions between GIV•Kindlin-2•β1-integrin on time to progression to metastasis. GIV and Kindlin (K2), two integrin adaptors that promote metastasis, bind each other Binding of GIV or integrin to K2 allosterically enhances GIV•K2•integrin complexes Binding is required for the maximal recruitment of GIV and K2 to active integrins Binding facilitates integrin clustering, activation, tumor cell adhesion, invasion
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Affiliation(s)
- Cristina Rohena
- Department of Medicine, University of California San Diego, 9500 Gilman Drive (MC 0651), George E. Palade Bldg, Rm 239, La Jolla, CA 92093, USA
| | - Nicholas Kalogriopoulos
- Department of Medicine, University of California San Diego, 9500 Gilman Drive (MC 0651), George E. Palade Bldg, Rm 239, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, University of California San Diego, CA 92093, USA
| | - Navin Rajapakse
- Department of Cellular and Molecular Medicine, University of California San Diego, CA 92093, USA
| | - Suchismita Roy
- Department of Cellular and Molecular Medicine, University of California San Diego, CA 92093, USA
| | - Inmaculada Lopez-Sanchez
- Department of Medicine, University of California San Diego, 9500 Gilman Drive (MC 0651), George E. Palade Bldg, Rm 239, La Jolla, CA 92093, USA
| | - Jailal Ablack
- Department of Medicine, University of California San Diego, 9500 Gilman Drive (MC 0651), George E. Palade Bldg, Rm 239, La Jolla, CA 92093, USA
| | - Debashis Sahoo
- Department of Pediatrics, University of California San Diego, CA 92093, USA; Department of Computer Science and Engineering, Jacob's School of Engineering, University of California San Diego, CA 92093, USA; Rebecca and John Moore Comprehensive Cancer Center, University of California San Diego, CA 92093, USA
| | - Pradipta Ghosh
- Department of Medicine, University of California San Diego, 9500 Gilman Drive (MC 0651), George E. Palade Bldg, Rm 239, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, University of California San Diego, CA 92093, USA; Rebecca and John Moore Comprehensive Cancer Center, University of California San Diego, CA 92093, USA; Veterans Affairs Medical Center, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.
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12
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Chill JH, Qasim A, Sher I, Gross R. NMR Perspectives of the KcsA Potassium Channel in the Membrane Environment. Isr J Chem 2019. [DOI: 10.1002/ijch.201900107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jordan H. Chill
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
| | - Arwa Qasim
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
| | - Inbal Sher
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
| | - Renana Gross
- Department of ChemistryBar Ilan University Ramat Gan 52900 Israel
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13
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Topological analysis of the gp41 MPER on lipid bilayers relevant to the metastable HIV-1 envelope prefusion state. Proc Natl Acad Sci U S A 2019; 116:22556-22566. [PMID: 31624123 DOI: 10.1073/pnas.1912427116] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The membrane proximal external region (MPER) of HIV-1 envelope glycoprotein (gp) 41 is an attractive vaccine target for elicitation of broadly neutralizing antibodies (bNAbs) by vaccination. However, current details regarding the quaternary structural organization of the MPER within the native prefusion trimer [(gp120/41)3] are elusive and even contradictory, hindering rational MPER immunogen design. To better understand the structural topology of the MPER on the lipid bilayer, the adjacent transmembrane domain (TMD) was appended (MPER-TMD) and studied. Membrane insertion of the MPER-TMD was sensitive both to the TMD sequence and cytoplasmic residues. Antigen binding of MPER-specific bNAbs, in particular 10E8 and DH511.2_K3, was significantly impacted by the presence of the TMD. Furthermore, MPER-TMD assembly into 10-nm diameter nanodiscs revealed a heterogeneous membrane array comprised largely of monomers and dimers, as enumerated by bNAb Fab binding using single-particle electron microscopy analysis, arguing against preferential trimeric association of native MPER and TMD protein segments. Moreover, introduction of isoleucine mutations in the C-terminal heptad repeat to induce an extended MPER α-helical bundle structure yielded an antigenicity profile of cell surface-arrayed Env variants inconsistent with that found in the native prefusion state. In line with these observations, electron paramagnetic resonance analysis suggested that 10E8 inhibits viral membrane fusion by lifting the MPER N-terminal region out of the viral membrane, mandating the exposure of residues that would be occluded by MPER trimerization. Collectively, our data suggest that the MPER is not a stable trimer, but rather a dynamic segment adapted for structural changes accompanying fusion.
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14
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Rajagopal N, Nangia S. Obtaining Protein Association Energy Landscape for Integral Membrane Proteins. J Chem Theory Comput 2019; 15:6444-6455. [DOI: 10.1021/acs.jctc.9b00626] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Nandhini Rajagopal
- Department of Biomedical and Chemical Engineering, Syracuse University, 343 Link Hall, Syracuse, New York 13244, United States
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, 343 Link Hall, Syracuse, New York 13244, United States
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15
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SHARPIN at the nexus of integrin, immune, and inflammatory signaling in human platelets. Proc Natl Acad Sci U S A 2019; 116:4983-4988. [PMID: 30804189 DOI: 10.1073/pnas.1819156116] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Platelets mediate primary hemostasis, and recent work has emphasized platelet participation in immunity and inflammation. The function of the platelet-specific integrin αIIbβ3 as a fibrinogen receptor in hemostasis is well defined, but the roles of αIIbβ3 or integrin-associated proteins in nonhemostatic platelet functions are poorly understood. Here we show that human platelets express the integrin-associated protein SHARPIN with functional consequences. In leukocytes, SHARPIN interacts with integrin α cytoplasmic tails, and it is also an obligate member of the linear ubiquitin chain assembly complex (LUBAC), which mediates Met1 linear ubiquitination of proteins leading to canonical NF-κB activation. SHARPIN interacted with αIIb in pull-down and coimmunoprecipitation assays. SHARPIN was partially localized, as was αIIbβ3, at platelet edges, and thrombin stimulation induced more central SHARPIN localization. SHARPIN also coimmunoprecipitated from platelets with the two other proteins comprising LUBAC, the E3 ligase HOIP and HOIL-1. Platelet stimulation with thrombin or inflammatory agonists, including lipopolysaccharide or soluble CD40 ligand (sCD40L), induced Met1 linear ubiquitination of the NF-κB pathway protein NEMO and serine-536 phosphorylation of the p65 RelA subunit of NF-κB. In human megakaryocytes and/or platelets derived from induced pluripotent stem (iPS) cells, SHARPIN knockdown caused increased basal and agonist-induced fibrinogen binding to αIIbβ3 as well as reduced Met1 ubiquitination and RelA phosphorylation. Moreover, these SHARPIN knockdown cells exhibited increased surface expression of MHC class I molecules and increased release of sCD40L. These results establish that SHARPIN functions in the human megakaryocyte/platelet lineage through protein interactions at the nexus of integrin and immune/inflammatory signaling.
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16
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Tseng HY, Samarelli AV, Kammerer P, Scholze S, Ziegler T, Immler R, Zent R, Sperandio M, Sanders CR, Fässler R, Böttcher RT. LCP1 preferentially binds clasped αMβ2 integrin and attenuates leukocyte adhesion under flow. J Cell Sci 2018; 131:jcs.218214. [PMID: 30333137 DOI: 10.1242/jcs.218214] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 09/07/2018] [Indexed: 12/13/2022] Open
Abstract
Integrins are α/β heterodimers that interconvert between inactive and active states. In the active state the α/β cytoplasmic domains recruit integrin-activating proteins and separate the transmembrane and cytoplasmic (TMcyto) domains (unclasped TMcyto). Conversely, in the inactive state the α/β TMcyto domains bind integrin-inactivating proteins, resulting in the association of the TMcyto domains (clasped TMcyto). Here, we report the isolation of integrin cytoplasmic tail interactors using either lipid bicelle-incorporated integrin TMcyto domains (α5, αM, αIIb, β1, β2 and β3 integrin TMcyto) or a clasped, lipid bicelle-incorporated αMβ2 TMcyto. Among the proteins found to preferentially bind clasped rather than the isolated αM and β2 subunits was L-plastin (LCP1, also known as plastin-2), which binds to and maintains the inactive state of αMβ2 integrin in vivo and thereby regulates leukocyte adhesion to integrin ligands under flow. Our findings offer a global view on cytoplasmic proteins interacting with different integrins and provide evidence for the existence of conformation-specific integrin interactors.
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Affiliation(s)
- Hui-Yuan Tseng
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany
| | - Anna V Samarelli
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany
| | - Patricia Kammerer
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany
| | - Sarah Scholze
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany
| | - Tilman Ziegler
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany
| | - Roland Immler
- Walter Brendel Center for Experimental Medicine, Ludwig-Maximilians-University, 81377 Munich, Germany
| | - Roy Zent
- Division of Nephrology, Department of Medicine, Vanderbilt University, Nashville, 37232 Tennessee, USA.,Department of Medicine, Veterans Affairs Medical Center, Nashville, 37232 Tennessee, USA
| | - Markus Sperandio
- Walter Brendel Center for Experimental Medicine, Ludwig-Maximilians-University, 81377 Munich, Germany
| | - Charles R Sanders
- Department of Biochemistry, Center for Structural Biology, and Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, 37232 Tennessee, USA
| | - Reinhard Fässler
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, 80802 Munich, Germany
| | - Ralph T Böttcher
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany .,DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, 80802 Munich, Germany
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17
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Surya W, Li Y, Torres J. Structural model of the SARS coronavirus E channel in LMPG micelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1309-1317. [PMID: 29474890 PMCID: PMC7094280 DOI: 10.1016/j.bbamem.2018.02.017] [Citation(s) in RCA: 113] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/14/2018] [Accepted: 02/16/2018] [Indexed: 01/27/2023]
Abstract
Coronaviruses (CoV) cause common colds in humans, but are also responsible for the recent Severe Acute, and Middle East, respiratory syndromes (SARS and MERS, respectively). A promising approach for prevention are live attenuated vaccines (LAVs), some of which target the envelope (E) protein, which is a small membrane protein that forms ion channels. Unfortunately, detailed structural information is still limited for SARS-CoV E, and non-existent for other CoV E proteins. Herein, we report a structural model of a SARS-CoV E construct in LMPG micelles with, for the first time, unequivocal intermolecular NOEs. The model corresponding to the detergent-embedded region is consistent with previously obtained orientational restraints obtained in lipid bilayers and in vivo escape mutants. The C-terminal domain is mostly α-helical, and extramembrane intermolecular NOEs suggest interactions that may affect the TM channel conformation.
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Affiliation(s)
- Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Yan Li
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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18
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Situ AJ, Kang SM, Frey BB, An W, Kim C, Ulmer TS. Membrane Anchoring of α-Helical Proteins: Role of Tryptophan. J Phys Chem B 2018; 122:1185-1194. [PMID: 29323921 PMCID: PMC11025564 DOI: 10.1021/acs.jpcb.7b11227] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The function of membrane proteins relies on a defined orientation of protein relative to lipid. In apparent correlation to protein anchoring, tryptophan residues are enriched in the lipid headgroup region. To characterize the thermodynamic and structural basis of this relationship in α-helical membrane proteins, we examined the role of three conserved tryptophans in the folding of the heterodimeric integrin αIIbβ3 transmembrane (TM) complex in phospholipid bicelles and mammalian membranes. In the homogenous lipid environment of bicelles, tryptophan was replaceable by residues of distinct polarities. The appropriate polarity was guided by the electrostatic potential of the tryptophan surrounding, suggesting that tryptophan can complement diverse environments by adjusting the orientation of its anisotropic side chain to achieve site-specific anchoring. As a sole membrane anchor, tryptophan made a contribution of 0.4 kcal/mol to TM complex stability in bicelles. In membranes, it proved more difficult to replace tryptophan even by tyrosine, indicating a superior capacity to interact with heterogeneous lipids of biological membranes. Interestingly, at intracellular TM helix ends, where integrin activation is initiated, sequence motifs that interact with lipids via opposing polarity patterns were found to restrict TM helix orientations beyond tryptophan anchoring. In contrast to bicelles, phenylalanine became the least accepted substitute in membranes, demonstrating an increased role of the hydrophobic effect. Altogether, our study implicates a wide amphiphilic range of tryptophan, membrane complexity, and the hydrophobic effect to be important factors in tryptophan membrane anchoring.
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Affiliation(s)
- Alan J Situ
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - So-Min Kang
- Department of Life Sciences, Korea University , 145 Anam-Ro, Seongbuk-Gu, Seoul 136-701, South Korea
| | - Benjamin B Frey
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Woojin An
- Department of Biochemistry & Molecular Medicine and Norris Comprehensive Cancer Center, University of Southern California , Los Angeles, California 90033, United States
| | - Chungho Kim
- Department of Life Sciences, Korea University , 145 Anam-Ro, Seongbuk-Gu, Seoul 136-701, South Korea
| | - Tobias S Ulmer
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
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19
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Lu Z, Mathew S, Chen J, Hadziselimovic A, Palamuttam R, Hudson BG, Fässler R, Pozzi A, Sanders CR, Zent R. Implications of the differing roles of the β1 and β3 transmembrane and cytoplasmic domains for integrin function. eLife 2016; 5. [PMID: 27929375 PMCID: PMC5207772 DOI: 10.7554/elife.18633] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 12/07/2016] [Indexed: 12/26/2022] Open
Abstract
Integrins are transmembrane receptors composed of α and β subunits. Although most integrins contain β1, canonical activation mechanisms are based on studies of the platelet integrin, αIIbβ3. Its inactive conformation is characterized by the association of the αIIb transmembrane and cytosolic domain (TM/CT) with a tilted β3 TM/CT that leads to activation when disrupted. We show significant structural differences between β1 and β3 TM/CT in bicelles. Moreover, the 'snorkeling' lysine at the TM/CT interface of β subunits, previously proposed to regulate αIIbβ3 activation by ion pairing with nearby lipids, plays opposite roles in β1 and β3 integrin function and in neither case is responsible for TM tilt. A range of affinities from almost no interaction to the relatively high avidity that characterizes αIIbβ3 is seen between various α subunits and β1 TM/CTs. The αIIbβ3-based canonical model for the roles of the TM/CT in integrin activation and function clearly does not extend to all mammalian integrins.
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Affiliation(s)
- Zhenwei Lu
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, United States
| | - Sijo Mathew
- Division of Nephrology, Department of Medicine, Vanderbilt Medical Center, Nashville, United States
| | - Jiang Chen
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, United States
| | - Arina Hadziselimovic
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, United States
| | - Riya Palamuttam
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, United States
| | - Billy G Hudson
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, United States.,Division of Nephrology, Department of Medicine, Vanderbilt Medical Center, Nashville, United States.,Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, United States.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, United States
| | - Reinhard Fässler
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Ambra Pozzi
- Division of Nephrology, Department of Medicine, Vanderbilt Medical Center, Nashville, United States.,Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, United States.,Veterans Affairs Hospital, Nashville, United States.,Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, United States
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, United States
| | - Roy Zent
- Division of Nephrology, Department of Medicine, Vanderbilt Medical Center, Nashville, United States.,Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, United States.,Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, United States.,Veterans Affairs Hospital, Nashville, United States
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20
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Schmidt T, Situ AJ, Ulmer TS. Direct Evaluation of Protein-Lipid Contacts Reveals Protein Membrane Immersion and Isotropic Bicelle Structure. J Phys Chem Lett 2016; 7:4420-4426. [PMID: 27776216 PMCID: PMC11027914 DOI: 10.1021/acs.jpclett.6b02159] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The solvation of membrane proteins by both lipids and water makes their membrane immersion difficult to predict and the choice of a membrane mimic challenging. To characterize protein-lipid contacts and bicelle membrane mimics, we examined protein-lipid cross-relaxation of integrin αIIb and β3(A711P) transmembrane helices in isotropic phospholipid bicelles (q = 0.5 and 0.7). Long-chain bicelle lipids dominated contacts with central helix segments, whereas both short- and long-chain lipids contacted the terminal turns of each helix in corroboration of the mixed bicelle model. The saturation transfer profiles from long-chain lipids directly established helix midpoints in the lipid bilayer. Lipid headgroups and water molecules engaged the side chains of buried serine and threonine in competition with intrahelical hydrogen bonding, illustrating that polar side chains seek the most favorable electrostatic contacts.
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Affiliation(s)
- Thomas Schmidt
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
- Present address: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alan J. Situ
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
| | - Tobias S. Ulmer
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
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21
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Schmidt T, Ye F, Situ AJ, An W, Ginsberg MH, Ulmer TS. A Conserved Ectodomain-Transmembrane Domain Linker Motif Tunes the Allosteric Regulation of Cell Surface Receptors. J Biol Chem 2016; 291:17536-46. [PMID: 27365391 PMCID: PMC5016151 DOI: 10.1074/jbc.m116.733683] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 06/09/2016] [Indexed: 11/06/2022] Open
Abstract
In many families of cell surface receptors, a single transmembrane (TM) α-helix separates ecto- and cytosolic domains. A defined coupling of ecto- and TM domains must be essential to allosteric receptor regulation but remains little understood. Here, we characterize the linker structure, dynamics, and resulting ecto-TM domain coupling of integrin αIIb in model constructs and relate it to other integrin α subunits by mutagenesis. Cellular integrin activation assays subsequently validate the findings in intact receptors. Our results indicate a flexible yet carefully tuned ecto-TM coupling that modulates the signaling threshold of integrin receptors. Interestingly, a proline at the N-terminal TM helix border, termed NBP, is critical to linker flexibility in integrins. NBP is further predicted in 21% of human single-pass TM proteins and validated in cytokine receptors by the TM domain structure of the cytokine receptor common subunit β and its P441A-substituted variant. Thus, NBP is a conserved uncoupling motif of the ecto-TM domain transition and the degree of ecto-TM domain coupling represents an important parameter in the allosteric regulation of diverse cell surface receptors.
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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
| | - Feng Ye
- the Department of Medicine, University of California San Diego, La Jolla, California 92093, and
| | - 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
| | - Woojin An
- the Department of Biochemistry & Molecular Biology and Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California 90033
| | - Mark H Ginsberg
- the Department of Medicine, University of California San Diego, La Jolla, California 92093, and
| | - 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,
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22
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Bugge K, Lindorff-Larsen K, Kragelund BB. Understanding single-pass transmembrane receptor signaling from a structural viewpoint-what are we missing? FEBS J 2016; 283:4424-4451. [PMID: 27350538 DOI: 10.1111/febs.13793] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/10/2016] [Accepted: 06/27/2016] [Indexed: 11/30/2022]
Abstract
Single-pass transmembrane receptors are involved in essential processes of both physiological and pathological nature and represent more than 1300 proteins in the human genome. Despite the high biological relevance of these receptors, the mechanisms of the signal transductions they facilitate are incompletely understood. One major obstacle is the lack of structures of the transmembrane domains that connect the extracellular ligand-binding domains to the intracellular signaling platforms. Over a period of almost 20 years since the first structure was reported, only 21 of these receptors have become represented by a transmembrane domain structure. This scarceness stands in strong contrast to the significance of these transmembrane α-helices for receptor functionality. In this review, we explore the properties and qualities of the current set of structures, as well as the methodological difficulties associated with their characterization and the challenges left to be overcome. Without an increased and focused effort to bring this class of proteins on par with the remaining membrane protein field, a serious lag in their biological understanding looms. Design of pharmaceutical agents, prediction of mutational affects in relation to disease, and deciphering of functional mechanisms require high-resolution structural information, especially when dealing with a domain carrying so much functionality in so few residues.
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Affiliation(s)
- Katrine Bugge
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
| | - Kresten Lindorff-Larsen
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
| | - Birthe B Kragelund
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
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23
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Dai A, Ye F, Taylor DW, Hu G, Ginsberg MH, Taylor KA. The Structure of a Full-length Membrane-embedded Integrin Bound to a Physiological Ligand. J Biol Chem 2015; 290:27168-27175. [PMID: 26391523 DOI: 10.1074/jbc.m115.682377] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Indexed: 11/06/2022] Open
Abstract
Increased ligand binding to integrin ("activation") underpins many biological processes, such as leukocyte trafficking, cell migration, host-pathogen interaction, and hemostasis. Integrins exist in several conformations, ranging from compact and bent to extended and open. However, the exact conformation of membrane-embedded, full-length integrin bound to its physiological macromolecular ligand is still unclear. Integrin αIIbβ3, the most abundant integrin in platelets, has been a prototype for integrin activation studies. Using negative stain electron microscopy and nanodisc-embedding to provide a membrane-like environment, we visualized the conformation of full-length αIIbβ3 in both a Mn(2+)-activated, ligand-free state and a Mn(2+)-activated, fibrin-bound state. Activated but ligand-free integrins exist mainly in the compact conformation, whereas fibrin-bound αIIbβ3 predominantly exists in a fully extended, headpiece open conformation. Our results show that membrane-embedded, full-length integrin adopts an extended and open conformation when bound to its physiological macromolecular ligand.
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Affiliation(s)
- Aguang Dai
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and
| | - Feng Ye
- Department of Hematology and Oncology, University of California at San Diego, La Jolla, California 92093-0726
| | - Dianne W Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and
| | - Guiqing Hu
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and
| | - Mark H Ginsberg
- Department of Hematology and Oncology, University of California at San Diego, La Jolla, California 92093-0726
| | - Kenneth A Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and.
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24
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Lee WH, Schaffner-Reckinger E, Tsoukatos DC, Aylward K, Moussis V, Tsikaris V, Trypou P, Egot M, Baruch D, Kieffer N, Bachelot-Loza C. Inhibition of αIIbβ3 Ligand Binding by an αIIb Peptide that Clasps the Hybrid Domain to the βI Domain of β3. PLoS One 2015; 10:e0134952. [PMID: 26332040 PMCID: PMC4557944 DOI: 10.1371/journal.pone.0134952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 07/15/2015] [Indexed: 11/22/2022] Open
Abstract
Agonist-stimulated platelet activation triggers conformational changes of integrin αIIbβ3, allowing fibrinogen binding and platelet aggregation. We have previously shown that an octapeptide, p1YMESRADR8, corresponding to amino acids 313–320 of the β-ribbon extending from the β-propeller domain of αIIb, acts as a potent inhibitor of platelet aggregation. Here we have performed in silico modelling analysis of the interaction of this peptide with αIIbβ3 in its bent and closed (not swing-out) conformation and show that the peptide is able to act as a substitute for the β-ribbon by forming a clasp restraining the β3 hybrid and βI domains in a closed conformation. The involvement of species-specific residues of the β3 hybrid domain (E356 and K384) and the β1 domain (E297) as well as an intrapeptide bond (pE315-pR317) were confirmed as important for this interaction by mutagenesis studies of αIIbβ3 expressed in CHO cells and native or substituted peptide inhibitory studies on platelet functions. Furthermore, NMR data corroborate the above results. Our findings provide insight into the important functional role of the αIIb β-ribbon in preventing integrin αIIbβ3 head piece opening, and highlight a potential new therapeutic approach to prevent integrin ligand binding.
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Affiliation(s)
- Wen Hwa Lee
- SGC, University of Oxford, Oxford, United Kingdom
| | - Elisabeth Schaffner-Reckinger
- Laboratoire de Biologie et Physiologie Intégrée, (CNRS/GDRE-ITI), University of Luxembourg, Luxembourg City, Luxembourg
| | | | - Kelly Aylward
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Vassilios Moussis
- Department of Chemistry, Section of Organic Chemistry and Biochemistry, Ioannina, Greece
| | - Vassilios Tsikaris
- Department of Chemistry, Section of Organic Chemistry and Biochemistry, Ioannina, Greece
| | - Paraskevi Trypou
- Department of Chemistry, Section of Organic Chemistry and Biochemistry, Ioannina, Greece
| | - Marion Egot
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Dominique Baruch
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Nelly Kieffer
- Laboratoire de Biologie et Physiologie Intégrée, (CNRS/GDRE-ITI), University of Luxembourg, Luxembourg City, Luxembourg
- CNRS-LIA124, Sino-French Research Center for Life Sciences and Genomics, Rui Jin Hospital, Jiao Tong University School of Medicine, Shanghai, China
| | - Christilla Bachelot-Loza
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- * E-mail:
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25
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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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Integrin αIIbβ3 transmembrane domain separation mediates bi-directional signaling across the plasma membrane. PLoS One 2015; 10:e0116208. [PMID: 25617834 PMCID: PMC4305291 DOI: 10.1371/journal.pone.0116208] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 12/06/2014] [Indexed: 11/19/2022] Open
Abstract
Integrins play an essential role in hemostasis, thrombosis, and cell migration, and they transmit bidirectional signals. Transmembrane/cytoplasmic domains are hypothesized to associate in the resting integrins; whereas, ligand binding and intracellular activating signals induce transmembrane domain separation. However, how this conformational change affects integrin outside-in signaling and whether the α subunit cytoplasmic domain is important for this signaling remain elusive. Using Chinese Hamster Ovary (CHO) cells that stably expressed different integrin αIIbβ3 constructs, we discovered that an αIIb cytoplasmic domain truncation led to integrin activation but not defective outside-in signaling. In contrast, preventing transmembrane domain separation abolished both inside-out and outside-in signaling regardless of removing the αIIb cytoplasmic tail. Truncation of the αIIb cytoplasmic tail did not obviously affect adhesion-induced outside-in signaling. Our research revealed that transmembrane domain separation is a downstream conformational change after the cytoplasmic domain dissociation in inside-out activation and indispensable for ligand-induced outside-in signaling. The result implicates that the β TM helix rearrangement after dissociation is essential for integrin transmembrane signaling. Furthermore, we discovered that the PI3K/Akt pathway is not essential for cell spreading but spreading-induced Erk1/2 activation is PI3K dependent implicating requirement of the kinase for cell survival in outside-in signaling.
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27
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CW-EPR studies revealed different motional properties and oligomeric states of the integrin β1a transmembrane domain in detergent micelles or liposomes. Sci Rep 2015; 5:7848. [PMID: 25597475 PMCID: PMC4297981 DOI: 10.1038/srep07848] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 12/16/2014] [Indexed: 12/15/2022] Open
Abstract
Integrins are heterodimeric membrane proteins that regulate essential processes: cell migration, cell growth, extracellular matrix assembly and tumor metastasis. Each integrin α or β subunit contains a large extracellular domain, a single transmembrane (TM) domain, and a short cytoplasmic tail. The integrin TM domains are important for heterodimeric association and dissociation during the conversion from inactive to active states. Moreover, integrin clustering occurs by homo-oligomeric interactions between the TM helices. Here, the transmembrane and cytoplasmic (TMC) domains of integrin β1a were overexpressed, and the protein was purified in detergent micelles and/or reconstituted in liposomes. To investigate the TM domain conformational properties of integrin β1a, 26 consecutive single cysteine mutants were generated for site-directed spin labeling and continuous-wave electron paramagnetic resonance (CW-EPR) mobility and accessibility analyses. The mobility analysis identified two integrin β1a-TM regions with different motional properties in micelles and a non-continuous integrin β1a-TM helix with high immobility in liposomes. The accessibility analysis verified the TM range (Val737-Lys752) of the integrin β1a-TMC in micelles. Further mobility and accessibility comparisons of the integrin β1a-TMC domains in micelles or liposomes identified distinctively different oligomeric states of integrin β1a-TM, namely a monomer embedded in detergent micelles and leucine-zipper-like homo-oligomeric clusters in liposomes.
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28
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Botelho SC, Enquist K, von Heijne G, Draheim RR. Differential repositioning of the second transmembrane helices from E. coli Tar and EnvZ upon moving the flanking aromatic residues. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:615-21. [PMID: 25445668 DOI: 10.1016/j.bbamem.2014.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/29/2014] [Accepted: 11/17/2014] [Indexed: 01/04/2023]
Abstract
Aromatic tuning, i.e. repositioning aromatic residues found at the cytoplasmic end of transmembrane (TM) domains within bacterial receptors, has been previously shown to modulate signal output from the aspartate chemoreceptor (Tar) and the major osmosensor EnvZ of Escherichia coli. In the case of Tar, changes in signal output consistent with the vertical position of the native Trp-Tyr aromatic tandem within TM2 were observed. In contrast, within EnvZ, where a Trp-Leu-Phe aromatic triplet was repositioned, the surface that the triplet resided upon was the major determinant governing signal output. However, these studies failed to determine whether moving the aromatic residues was sufficient to physically reposition the TM helix within a membrane. Recent coarse-grained molecular dynamics (CG-MD) simulations predicted displacement of Tar TM2 upon moving the aromatic residues at the cytoplasmic end of the helix. Here, we demonstrate that repositioning the Trp-Tyr tandem within Tar TM2 displaces the C-terminal boundary of the helix relative to the membrane. In a similar analysis of EnvZ, an abrupt initial displacement of TM2 was observed but no subsequent movement was seen, suggesting that the vertical position of TM2 is not governed by the location of the Trp-Leu-Phe triplet. Our results also provide another set of experimental data, i.e. the resistance of EnvZ TM2 to being displaced upon aromatic tuning, which could be useful for subsequent refinement of the initial CG-MD simulations. Finally, we discuss the limitations of these methodologies, how moving flanking aromatic residues might impact steady-state signal output and the potential to employ aromatic tuning in other bacterial membrane-spanning receptors.
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Affiliation(s)
- Salomé C Botelho
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Karl Enquist
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Gunnar von Heijne
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Roger R Draheim
- Division of Pharmacy, Durham University, Queen's Campus, Stockton-on-Tees TS17 6BH, England, UK; Wolfson Research Institute for Health and Wellbeing, Durham University, Queen's Campus, Stockton-on-Tees, TS17 6BH, England, UK.
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29
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Situ AJ, Schmidt T, Mazumder P, Ulmer TS. Characterization of Membrane Protein Interactions by Isothermal Titration Calorimetry. J Mol Biol 2014; 426:3670-80. [DOI: 10.1016/j.jmb.2014.08.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 08/18/2014] [Accepted: 08/25/2014] [Indexed: 12/11/2022]
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Provasi D, Negri A, Coller BS, Filizola M. Talin-driven inside-out activation mechanism of platelet αIIbβ3 integrin probed by multimicrosecond, all-atom molecular dynamics simulations. Proteins 2014; 82:3231-3240. [PMID: 24677266 DOI: 10.1002/prot.24540] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 02/06/2014] [Accepted: 02/10/2014] [Indexed: 01/20/2023]
Abstract
Platelet aggregation is the consequence of the binding of extracellular bivalent ligands such as fibrinogen and von Willebrand factor to the high affinity, active state of integrin αIIbβ3. This state is achieved through a so-called "inside-out" mechanism characterized by the membrane-assisted formation of a complex between the F2 and F3 subdomains of intracellular protein talin and the integrin β3 tail. Here, we present the results of multi-microsecond, all-atom molecular dynamics simulations carried on the complete transmembrane (TM) and C-terminal (CT) domains of αIIbβ3 integrin in an explicit lipid-water environment, and in the presence or absence of the talin-1 F2 and F3 subdomains. These large-scale simulations provide unprecedented molecular-level insights into the talin-driven inside-out activation of αIIbβ3 integrin. Specifically, they suggest a preferred conformation of the complete αIIbβ3 TM/CT domains in a lipid-water environment, and testable hypotheses of key intermolecular interactions between αIIbβ3 integrin and the F2/F3 domains of talin-1. Notably, not only do these simulations give support to a stable left-handed reverse turn conformation of the αIIb juxtamembrane motif rather than a helical turn, but they raise the question as to whether TM helix separation is required for talin-driven integrin activation.
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Affiliation(s)
- Davide Provasi
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1677, New York, New York 10029
| | - Ana Negri
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1677, New York, New York 10029
| | - Barry S Coller
- Allen and Frances Adler Laboratory of Blood and Vascular Biology, The Rockefeller University, 1230 York Avenue, Box 309, New York, New York 10065
| | - Marta Filizola
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1677, New York, New York 10029
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31
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Müller MA, Brunie L, Bächer AS, Kessler H, Gottschalk KE, Reuning U. Cytoplasmic salt bridge formation in integrin αvß3 stabilizes its inactive state affecting integrin-mediated cell biological effects. Cell Signal 2014; 26:2493-503. [PMID: 25041847 DOI: 10.1016/j.cellsig.2014.07.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 07/09/2014] [Indexed: 02/01/2023]
Abstract
Heterodimeric integrin receptors are mediators of cell adhesion, motility, invasion, proliferation, and survival. By this, they are crucially involved in (tumor) cell biological behavior. Integrins trigger signals bidirectionally across cell membranes: by outside-in, following binding of protein ligands of the extracellular matrix, and by inside-out, where proteins are recruited to ß-integrin cytoplasmic tails resulting in conformational changes leading to increased integrin binding affinity and integrin activation. Computational modeling and experimental/mutational approaches imply that associations of integrin transmembrane domains stabilize the low-affinity integrin state. Moreover, a cytoplasmic interchain salt bridge is discussed to contribute to a tight clasp of the α/ß-membrane-proximal regions; however, its existence and physiological relevance for integrin activation are still a controversial issue. In order to further elucidate the functional role of salt bridge formation, we designed mutants of the tumor biologically relevant integrin αvß3 by mutually exchanging the salt bridge forming amino acid residues on each chain (αvR995D and ß3D723R). Following transfection of human ovarian cancer cells with different combinations of wild type and mutated integrin chains, we showed that loss of salt bridge formation strengthened αvß3-mediated adhesion to vitronectin, provoked recruitment of cytoskeletal proteins, such as talin, and induced integrin signaling, ultimately resulting in enhanced cell migration, proliferation, and activation of integrin-related signaling molecules. These data support the notion of a functional relevance of integrin cytoplasmic salt bridge disruption during integrin activation.
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Affiliation(s)
- Martina A Müller
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany
| | - Leonora Brunie
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany
| | - Anne-Sophie Bächer
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany
| | - Horst Kessler
- Institute for Advanced Study and Centre of Integrated Protein Science, Department Chemie, Technische Universitaet München, Garching, Germany; Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | | | - Ute Reuning
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany.
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32
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Virkki M, Boekel C, Illergård K, Peters C, Shu N, Tsirigos KD, Elofsson A, von Heijne G, Nilsson I. Large tilts in transmembrane helices can be induced during tertiary structure formation. J Mol Biol 2014; 426:2529-38. [PMID: 24793448 DOI: 10.1016/j.jmb.2014.04.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/19/2014] [Accepted: 04/22/2014] [Indexed: 10/25/2022]
Abstract
While early structural models of helix-bundle integral membrane proteins posited that the transmembrane α-helices [transmembrane helices (TMHs)] were orientated more or less perpendicular to the membrane plane, there is now ample evidence from high-resolution structures that many TMHs have significant tilt angles relative to the membrane. Here, we address the question whether the tilt is an intrinsic property of the TMH in question or if it is imparted on the TMH during folding of the protein. Using a glycosylation mapping technique, we show that four highly tilted helices found in multi-spanning membrane proteins all have much shorter membrane-embedded segments when inserted by themselves into the membrane than seen in the high-resolution structures. This suggests that tilting can be induced by tertiary packing interactions within the protein, subsequent to the initial membrane-insertion step.
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Affiliation(s)
- Minttu Virkki
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden
| | - Carolina Boekel
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Kristoffer Illergård
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden
| | - Christoph Peters
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden
| | - Nanjiang Shu
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden
| | - Konstantinos D Tsirigos
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden
| | - Arne Elofsson
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden
| | - Gunnar von Heijne
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-17177 Solna, Sweden.
| | - IngMarie Nilsson
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden.
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33
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Song Y, Kenworthy AK, Sanders CR. Cholesterol as a co-solvent and a ligand for membrane proteins. Protein Sci 2013; 23:1-22. [PMID: 24155031 DOI: 10.1002/pro.2385] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 09/27/2013] [Accepted: 10/01/2013] [Indexed: 01/23/2023]
Abstract
As of mid 2013 a Medline search on "cholesterol" yielded over 200,000 hits, reflecting the prominence of this lipid in numerous aspects of animal cell biology and physiology under conditions of health and disease. Aberrations in cholesterol homeostasis underlie both a number of rare genetic disorders and contribute to common sporadic and complex disorders including heart disease, stroke, type II diabetes, and Alzheimer's disease. The corresponding author of this review and his lab stumbled only recently into the sprawling area of cholesterol research when they discovered that the amyloid precursor protein (APP) binds cholesterol, a topic covered by the Hans Neurath Award lecture at the 2013 Protein Society Meeting. Here, we first provide a brief overview of cholesterol-protein interactions and then offer our perspective on how and why binding of cholesterol to APP and its C99 domain (β-CTF) promotes the amyloidogenic pathway, which is closely related to the etiology of Alzheimer's disease.
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Affiliation(s)
- Yuanli Song
- Department of Biochemistry, Center for Structural Biology and Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, 37232
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34
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Surya W, Li Y, Millet O, Diercks T, Torres J. Transmembrane and Juxtamembrane Structure of αL Integrin in Bicelles. PLoS One 2013; 8:e74281. [PMID: 24069290 PMCID: PMC3771934 DOI: 10.1371/journal.pone.0074281] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 07/30/2013] [Indexed: 12/28/2022] Open
Abstract
The accepted model for the interaction of α and β integrins in the transmembrane (TM) domain is based on the pair αIIbβ3. This involves the so-called outer and inner membrane association clasps (OMC and IMC, respectively). In the α chain, the OMC involves a GxxxG-like motif, whereas in the IMC a conserved juxtamembrane GFFKR motif experiences a backbone reversal that partially fills the void generated by TM separation towards the cytoplasmic half. However, the GFFKR motif of several α integrin cytoplasmic tails in non-bicelle environments has been shown to adopt an α-helical structure that is not membrane-embedded and which was shown to bind a variety of cytoplasmic proteins. Thus it is not known if a membrane-embedded backbone reversal is a conserved structural feature in α integrins. We have studied the system αLβ2 because of its importance in leukocytes, where integrin deactivation is particularly important. Herein we show that the backbone reversal feature is not only present in αIIb but also in αL-TM when reconstituted in bicelles. Additionally, titration with β2 TM showed eight residues clustering along one side of αL-TM, forming a plausible interacting face with β2. The latter orientation is consistent with a previously predicted reported polar interaction between αL Ser-1071 and β2 Thr-686.
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Affiliation(s)
- Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yan Li
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Oscar Millet
- Structural Biology Unit, CIC BioGUNE, Derio Vizcaya, Spain
| | - Tammo Diercks
- Structural Biology Unit, CIC BioGUNE, Derio Vizcaya, Spain
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail:
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35
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Lai C, Liu X, Tian C, Wu F. Integrin α1 has a long helix, extending from the transmembrane region to the cytoplasmic tail in detergent micelles. PLoS One 2013; 8:e62954. [PMID: 23646163 PMCID: PMC3639902 DOI: 10.1371/journal.pone.0062954] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/26/2013] [Indexed: 12/12/2022] Open
Abstract
Integrin proteins are very important adhesion receptors that mediate cell-cell and cell-extracellular matrix interactions. They play essential roles in cell signaling and the regulation of cellular shape, motility, and the cell cycle. Here, the transmembrane and cytoplasmic (TMC) domains of integrin α1 and β1 were over-expressed and purified in detergent micelles. The structure and backbone relaxations of α1-TMC in LDAO micelles were determined and analyzed using solution NMR. A long helix, extending from the transmembrane region to the cytoplasmic tail, was observed in α1-TMC. Structural comparisons of α1-TMC with reported αIIb-TMC domains indicated different conformations in the transmembrane regions and cytoplasmic tails. An NMR titration experiment indicated weak interactions between α1-TMC and β1-TMC through several α1-TMC residues located at its N-terminal juxta-transmembrane region and C-terminal extended helix region.
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Affiliation(s)
- Chaohua Lai
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Xiaoxi Liu
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Changlin Tian
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
- * E-mail: (CT); (FW)
| | - Fangming Wu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
- * E-mail: (CT); (FW)
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36
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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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Abstract
Integrins are heterodimeric cell adhesion molecules that are important in many biological functions, such as cell migration, proliferation, differentiation, and survival. They can transmit bi-directional signals across the plasma membrane. Inside-out activating signal from some cell surface receptors bound with soluble agonists triggers integrins conformational change leading to high affinity for extracellular ligands. Then binding of ligands to integrins results in outside-in signaling, leading to formation of focal adhesion complex at the integrin cytoplasmic tail and activation of downstream signal pathways. This bi-directional signaling is essential for rapid response of cell to surrounding environmental changes. During this process, the conformational change of integrin extracellular and transmembrane/cytoplasmic domains is particularly important. In this review, we will summarize recent progress in both inside-out and outside-in signaling with specific focus on the mechanism how integrins transmit bi-directional signals through transmembrane/cytoplasmic domains.
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Affiliation(s)
- Ping Hu
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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39
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Dürr UN, Gildenberg M, Ramamoorthy A. The magic of bicelles lights up membrane protein structure. Chem Rev 2012; 112:6054-74. [PMID: 22920148 PMCID: PMC3497859 DOI: 10.1021/cr300061w] [Citation(s) in RCA: 266] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Indexed: 12/12/2022]
Affiliation(s)
| | - Melissa Gildenberg
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055,
United States
| | - Ayyalusamy Ramamoorthy
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055,
United States
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40
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β1 integrin NPXY motifs regulate kidney collecting-duct development and maintenance by induced-fit interactions with cytosolic proteins. Mol Cell Biol 2012; 32:4080-91. [PMID: 22869523 DOI: 10.1128/mcb.00568-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Loss of β1 integrin expression inhibits renal collecting-system development. Two highly conserved NPXY motifs in the distal β1 tail regulate integrin function by associating with phosphtyrosine binding (PTB) proteins, such as talin and kindlin. Here, we define the roles of these two tyrosines in collecting-system development and delineate the structural determinants of the distal β1 tail using nuclear magnetic resonance (NMR). Mice carrying alanine mutations have moderate renal collecting-system developmental abnormalities relative to β1-null mice. Phenylalanine mutations did not affect renal collecting-system development but increased susceptibility to renal injury. NMR spectra in bicelles showed the distal β1 tail is disordered and does not interact with the model membrane surface. Alanine or phenylalanine mutations did not alter β1 structure or interactions between α and β1 subunit transmembrane/cytoplasmic domains; however, they did decrease talin and kindlin binding. Thus, these studies highlight the fact that the functional roles of the NPXY motifs are organ dependent. Moreover, the β1 cytoplasmic tail, in the context of the adjacent transmembrane domain in bicelles, is significantly different from the more ordered, membrane-associated β3 integrin tail. Finally, tyrosine mutations of β1 NPXY motifs induce phenotypes by disrupting their interactions with critical integrin binding proteins like talins and kindlins.
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Suk JE, Situ AJ, Ulmer TS. Construction of covalent membrane protein complexes and high-throughput selection of membrane mimics. J Am Chem Soc 2012; 134:9030-3. [PMID: 22626249 PMCID: PMC3415561 DOI: 10.1021/ja304247f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The association of transmembrane (TM) helices underlies membrane protein structure and folding. Structural studies of TM complexes are limited by complex stability and the often time-consuming selection of suitable membrane mimics. Here, methodology for the efficient, preparative scale construction of covalent TM complexes and the concomitant high-throughput selection of membrane mimics is introduced. For the employed integrin αIIbβ3 model system, the methodology identified phospholipid bicelles, including their specific composition, as the best membrane mimic. The method facilitates structure determination by NMR spectroscopy as exemplified by the measurement of previously inaccessible residual dipolar couplings and (15)N relaxation parameters.
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Affiliation(s)
- Jae-Eun Suk
- Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Alan J. Situ
- Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Tobias S. Ulmer
- Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
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Kurtz L, Kao L, Newman D, Kurtz I, Zhu Q. Integrin αIIbβ3 inside-out activation: an in situ conformational analysis reveals a new mechanism. J Biol Chem 2012; 287:23255-65. [PMID: 22613710 DOI: 10.1074/jbc.m112.360966] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrins are a family of heterodimeric adhesion receptors that transmit signals bi-directionally across the plasma membranes. The transmembrane domain (TM) of integrin plays a critical role in mediating transition of the receptor from the default inactive to the active state on the cell surfaces. In this study, we successfully applied the substituted cysteine scanning accessibility method to determine the intracellular border of the integrin α(IIb)β(3) TM in the inactive and active states in living cells. We examined the aqueous accessibility of 75 substituted cysteines comprising the C terminus of both α(IIb) and β(3) TMs, the intracellular membrane-proximal regions, and the whole cytoplasmic tails, to the labeling of a membrane-permeable, cysteine-specific chemical biotin maleimide (BM). The active state of integrin α(IIb)β(3) heterodimer was generated by co-expression of activating partners with the cysteine-substituted constructs. Our data revealed that, in the inactive state, the intracellular lipid/aqueous border of α(IIb) TM was at Lys(994) and β(3) TM was at Phe(727) respectively; in the active state, the border of α(IIb) TM shifted to Pro(998), whereas the border of β(3) TM remained unchanged, suggesting that complex conformational changes occurred in the TMs upon α(IIb)β(3) inside-out activation. On the basis of the results, we propose a new inside-out activation mechanism for integrin α(IIb)β(3) and by inference, all of the integrins in their native cellular environment.
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Affiliation(s)
- Lisa Kurtz
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-1689, USA
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43
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Burgess JK, Weckmann M. Matrikines and the lungs. Pharmacol Ther 2012; 134:317-37. [PMID: 22366287 DOI: 10.1016/j.pharmthera.2012.02.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 02/03/2012] [Indexed: 01/09/2023]
Abstract
The extracellular matrix is a complex network of fibrous and nonfibrous molecules that not only provide structure to the lung but also interact with and regulate the behaviour of the cells which it surrounds. Recently it has been recognised that components of the extracellular matrix proteins are released, often through the action of endogenous proteases, and these fragments are termed matrikines. Matrikines have biological activities, independent of their role within the extracellular matrix structure, which may play important roles in the lung in health and disease pathology. Integrins are the primary cell surface receptors, characterised to date, which are used by the matrikines to exert their effects on cells. However, evidence is emerging for the need for co-factors and other receptors for the matrikines to exert their effects on cells. The potential for matrikines, and peptides derived from these extracellular matrix protein fragments, as therapeutic agents has recently been recognised. The natural role of these matrikines (including inhibitors of angiogenesis and possibly inflammation) make them ideal targets to mimic as therapies. A number of these peptides have been taken forward into clinical trials. The focus of this review will be to summarise our current understanding of the role, and potential for highly relevant actions, of matrikines in lung health and disease.
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Affiliation(s)
- Janette K Burgess
- Cell Biology, Woolcock Institute of Medical Research, Sydney, NSW, Australia.
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Kim C, Schmidt T, Cho EG, Ye F, Ulmer TS, Ginsberg MH. Basic amino-acid side chains regulate transmembrane integrin signalling. Nature 2011; 481:209-13. [PMID: 22178926 PMCID: PMC3257387 DOI: 10.1038/nature10697] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 11/03/2011] [Indexed: 01/05/2023]
Abstract
Side chains of Lys/Arg near transmembrane domain (TMD)1–3 membrane-water interfaces can “snorkel” placing their positive charge near negatively-charged phospholipid head groups4–6; however, snorkeling's functional effects are obscure. Integrin β TMDs exhibit such conserved basic amino acids; here we used nuclear magnetic resonance (NMR) spectroscopy7, 8 to show that integrin β3(Lys716) helps determine β3 TMD topography. The αIIbβ3 TMD structure suggests that precise β3 TMD crossing angles enable the assembly of outer and inner membrane “clasps” (OMC and IMC) that hold the αβ TMD together to limit transmembrane signalling9 . Mutation of β3(Lys716) caused dissociation of αIIbβ3 TMDs and integrin activation. To confirm that altered topography of β3(Lys716) mutants activated αIIbβ3, we utilized directed evolution of β3(K716A) to identify substitutions restoring default state. Introduction Pro(711) at the midpoint of β3 TMD (A711P) increased αIIbβ3 TMD association and inactivated integrin αIIbβ3(A711P,K716A). β3(Pro711) introduced a TMD kink of 30 ± 1° precisely at the OMC/IMC border, thereby decoupling the tilt between these segments. Thus, widely-occurring snorkeling residues in TMDs can help maintain TMD topography and membrane-embedding thereby regulating transmembrane signalling.
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Affiliation(s)
- Chungho Kim
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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45
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Kang C, Li Q. Solution NMR study of integral membrane proteins. Curr Opin Chem Biol 2011; 15:560-9. [DOI: 10.1016/j.cbpa.2011.05.025] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 05/12/2011] [Accepted: 05/23/2011] [Indexed: 11/29/2022]
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Multiscale simulations suggest a mechanism for integrin inside-out activation. Proc Natl Acad Sci U S A 2011; 108:11890-5. [PMID: 21730166 DOI: 10.1073/pnas.1104505108] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Integrins are large cell-surface adhesion receptors that can be activated to a high affinity state by the formation of an intracellular complex between the integrin β-subunit tail, the membrane, and talin. The F2 and F3 subdomains of the talin head play a key role in formation of this complex. Here, activation of the integrin αIIb/β3 dimer by the talin head domain was probed using multiscale molecular dynamics simulations. A number of novel insights emerge from these studies, including (i) the importance of the integrin αIIb subunit F992 and F993 residues in stabilizing the "off" state of the αIIb/β3 dimer, (ii) a crucial role for negatively charged groups in the F2-F3/membrane interaction, (iii) binding of the talin F2-F3 domain to negatively charged lipid headgroups in the membrane induces a reorientation of the β transmembrane (TM) domain, (iv) an increase in the tilt angle of the β TM domain relative to the bilayer normal helps to destabilize the α/β TM interaction and promote a scissor-like movement of the integrin TM helices. These results, combined with various published experimental observations, suggest a model for the mechanism of inside-out activation of integrins by talin.
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Abstract
Regulation of cell-cell and cell-matrix interaction is essential for the normal physiology of metazoans and is important in many diseases. Integrin adhesion receptors can rapidly increase their affinity (integrin activation) in response to intracellular signaling events in a process termed inside-out signaling. The transmembrane domains of integrins and their interactions with the membrane are important in inside-out signaling. Moreover, integrin activation is tightly regulated by a complex network of signaling pathways. Here, we review recent progress in understanding how the membrane environment can, in cooperation with integrin-binding proteins, regulate integrin activation.
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Affiliation(s)
- Chungho Kim
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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A view into the blind spot: solution NMR provides new insights into signal transduction across the lipid bilayer. Structure 2011; 18:1559-69. [PMID: 21134635 DOI: 10.1016/j.str.2010.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 11/15/2010] [Accepted: 11/16/2010] [Indexed: 01/29/2023]
Abstract
One of the most fundamental problems in cell biology concerns how cells communicate with their surroundings through surface receptors. The last few decades have seen major advances in understanding the mechanisms of receptor-ligand recognition and the biochemical consequences of such encounters. This review describes the emergence of solution nuclear magnetic resonance (NMR) spectroscopy as a powerful tool for the structural characterization of membrane-associated protein domains involved in transmembrane signaling. We highlight particularly instructive examples from the fields of immunoreceptor biology, growth hormone signaling, and cell adhesion. These signaling complexes comprise multiple subunits each spanning the membrane with a single helical segment that links extracellular ligand-binding domains to the cell interior. The apparent simplicity of this domain organization belies the complexity involved in cooperative assembly of functional structures that translate information across the cellular boundary.
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Abstract
Integrins are large, membrane-spanning, heterodimeric proteins that are essential for a metazoan existence. All members of the integrin family adopt a shape that resembles a large "head" on two "legs," with the head containing the sites for ligand binding and subunit association. Most of the receptor dimer is extracellular, but both subunits traverse the plasma membrane and terminate in short cytoplasmic domains. These domains initiate the assembly of large signaling complexes and thereby bridge the extracellular matrix to the intracellular cytoskeleton. To allow cells to sample and respond to a dynamic pericellular environment, integrins have evolved a highly responsive receptor activation mechanism that is regulated primarily by changes in tertiary and quaternary structure. This review summarizes recent progress in the structural and molecular functional studies of this important class of adhesion receptor.
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Affiliation(s)
- Iain D Campbell
- Department of Biochemistry, University of Oxford, United Kingdom.
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50
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Abstract
Integrins are cell adhesion molecules that play important roles in many biological processes including hemostasis, immune responses, development, and cancer. Their adhesiveness is dynamically regulated through a process termed inside-out signaling. In addition, ligand binding transduces outside-in signals from the extracellular domain to the cytoplasm. Advances in the past several years have shed light on structural basis for integrin regulation and signaling, especially how the large-scale reorientations of the ectodomain are related to the inter-domain and intra-domain shape shifting that changes ligand-binding affinity. Experiments have also shown how the conformational changes of the ectodomain are linked to changes in the α- and β-subunit transmembrane and cytoplasmic domains.
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Affiliation(s)
- Guanyuan Fu
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
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