1
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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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2
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Feng H, Huang G, Cao B, Zan Z, Wei Q. Maximum amplitude and mean platelet volume in the blood as biomarkers to detect lung adenocarcinoma cancer featured with ground-glass nodules. EUR J INFLAMM 2023. [DOI: 10.1177/1721727x231151530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Objectives The development and progression of malignancies are closely linked to hypercoagulability. As an early type of lung adenocarcinoma, ground glass nodules (GGNs) have been detected increasingly. Blood Maximum amplitude (MA) and mean platelet volume (MPV) are related to various conditions of hypercoagulability. Therefore, the role of MA and MPV in diagnosing lung adenocarcinoma cancer featured with GGNs was investigated in this case-control study. Methods The analyzed data of this study is derived from GGNs patients and healthy individuals in West China (Airport) Hospital Sichuan University. The differences between GGNs patients and healthy individuals were determined by one-way ANOVA, logistic regression or chi-squared test. The accuracy of diagnostic was performed by receiver operating characteristic curve (ROC). The relative mRNA expressions were studied by RT-qPCR. Results 470 patients diagnosed with GGNs which benign lesions (BN group) are inflammatory and malignant lesions (LC group) are adenocarcinoma in stage IA, and 235 healthy subjects (HC group) were enrolled in this study. Levels of MA and MPV were increased in LC group compared with BN and HC group ( p < 0.001, p < 0.001). When we combined MA and MPV, MA and MPV presented a sensitivity (SEN) of 0.809 and a specificity (SPE) of 0.774. And the area under the curve (AUC) increased to 0.871 (0.837–0.900) when confidence interval was 95%. Conclusion This study demonstrates that there have been systemic changes in coagulation disorders in the pathogenesis of GGNs. The diagnostic ability to different lung adenocarcinoma cancer featured with GGNs from benign or healthy controls can be improved by the combination of MA and MPV. Maximum amplitude and MPV may be used as biomarkers to detect lung adenocarcinoma cancer featured with GGNs.
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Affiliation(s)
- Hao Feng
- Department of Thoracic Surgery, The First People’s Hospital of Shuangliu District, Chengdu, China
| | - Gaigai Huang
- Department of Clinical Laboratory, The First People’s Hospital of Shuangliu District, Chengdu, China
| | - Boxiong Cao
- Department of Thoracic Surgery, The First People’s Hospital of Shuangliu District, Chengdu, China
| | - Ziliang Zan
- Department of Thoracic Surgery, The First People’s Hospital of Shuangliu District, Chengdu, China
| | - Qiang Wei
- Department of Thoracic Surgery, The First People’s Hospital of Shuangliu District, Chengdu, China
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3
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Zhang H, Zhu DS, Zhu J. Family-wide analysis of integrin structures predicted by AlphaFold2. Comput Struct Biotechnol J 2023; 21:4497-4507. [PMID: 37753178 PMCID: PMC10518446 DOI: 10.1016/j.csbj.2023.09.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/17/2023] [Accepted: 09/17/2023] [Indexed: 09/28/2023] Open
Abstract
Recent advances in protein structure prediction using AlphaFold2, known for its high efficiency and accuracy, have opened new avenues for comprehensive analysis of all structures within a single protein family. In this study, we evaluated the capabilities of AphaFold2 in analyzing integrin structures. Integrins are heterodimeric cell surface receptors composed of a combination of 18 α and 8 β subunits, resulting in a family of 24 different members. Both α and β subunits consist of a large extracellular domain, a short transmembrane domain, and typically, a short cytoplasmic tail. Integrins play a pivotal role in a wide range of cellular functions by recognizing diverse ligands. Despite significant advances in integrin structural studies in recent decades, high-resolution structures have only been determined for a limited subsets of integrin members, thus limiting our understanding of the entire integrin family. Here, we first analyzed the single-chain structures of 18 α and 8 β integrins in the AlphaFold2 protein structure database. We then employed the newly developed AlphaFold2-multimer program to predict the α/β heterodimer structures of all 24 human integrins. The predicted structures show a high level of accuracy for the subdomains of both α and β subunits, offering high-resolution structure insights for all integrin heterodimers. Our comprehensive structural analysis of the entire integrin family unveils a potentially diverse range of conformations among the 24 members, providing a valuable structure database for studies related to integrin structure and function. We further discussed the potential applications and limitations of the AlphaFold2-derived integrin structures.
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Affiliation(s)
- Heng Zhang
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Daniel S. Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Jieqing Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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4
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Zhang H, Zhu DS, Zhu J. Family-wide analysis of integrin structures predicted by AlphaFold2. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.02.539023. [PMID: 37205578 PMCID: PMC10187181 DOI: 10.1101/2023.05.02.539023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Recent advances in protein structure prediction using AlphaFold2, known for its high efficiency and accuracy, have opened new avenues for comprehensive analysis of all structures within a single protein family. In this study, we evaluated the capabilities of AphaFold2 in analyzing integrin structures. Integrins are heterodimeric cell surface receptors composed of a combination of 18 α and 8 β subunits, resulting in a family of 24 different members. Both α and β subunits consist of a large extracellular domain, a short transmembrane domain, and typically, a short cytoplasmic tail. Integrins play a pivotal role in a wide range of cellular functions by recognizing diverse ligands. Despite significant advances in integrin structural studies in recent decades, high-resolution structures have only been determined for a limited subsets of integrin members, thus limiting our understanding of the entire integrin family. Here, we first analyzed the single-chain structures of 18 α and 8 β integrins in the AlphaFold2 protein structure database. We then employed the newly developed AlphaFold2-multimer program to predict the α/β heterodimer structures of all 24 human integrins. The predicted structures show a high level of accuracy for the subdomains of both α and β subunits, offering high-resolution structure insights for all integrin heterodimers. Our comprehensive structural analysis of the entire integrin family unveils a potentially diverse range of conformations among the 24 members, providing a valuable structure database for studies related to integrin structure and function. We further discussed the potential applications and limitations of the AlphaFold2-derived integrin structures.
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Affiliation(s)
- Heng Zhang
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Daniel S. Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Jieqing Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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5
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Gc JB, Chen J, Pokharel SM, Mohanty I, Mariasoosai C, Obi P, Panipinto P, Bandyopadhyay S, Bose S, Natesan S. Molecular basis for the recognition of 24-(S)-hydroxycholesterol by integrin αvβ3. Sci Rep 2023; 13:9166. [PMID: 37280310 DOI: 10.1038/s41598-023-36040-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 05/28/2023] [Indexed: 06/08/2023] Open
Abstract
A growing body of evidence suggests that oxysterols such as 25-hydroxycholesterol (25HC) are biologically active and involved in many physiological and pathological processes. Our previous study demonstrated that 25HC induces an innate immune response during viral infections by activating the integrin-focal adhesion kinase (FAK) pathway. 25HC produced the proinflammatory response by binding directly to integrins at a novel binding site (site II) and triggering the production of proinflammatory mediators such as tumor necrosis factor-α (TNF) and interleukin-6 (IL-6). 24-(S)-hydroxycholesterol (24HC), a structural isomer of 25HC, plays a critical role in cholesterol homeostasis in the human brain and is implicated in multiple inflammatory conditions, including Alzheimer's disease. However, whether 24HC can induce a proinflammatory response like 25HC in non-neuronal cells has not been studied and remains unknown. The aim of this study was to examine whether 24HC produces such an immune response using in silico and in vitro experiments. Our results indicate that despite being a structural isomer of 25HC, 24HC binds at site II in a distinct binding mode, engages in varied residue interactions, and produces significant conformational changes in the specificity-determining loop (SDL). In addition, our surface plasmon resonance (SPR) study reveals that 24HC could directly bind to integrin αvβ3, with a binding affinity three-fold lower than 25HC. Furthermore, our in vitro studies with macrophages support the involvement of FAK and NFκB signaling pathways in triggering 24HC-mediated production of TNF. Thus, we have identified 24HC as another oxysterol that binds to integrin αvβ3 and promotes a proinflammatory response via the integrin-FAK-NFκB pathway.
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Affiliation(s)
- Jeevan B Gc
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, 992020, USA
| | - Justin Chen
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, 992020, USA
| | - Swechha M Pokharel
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA, 99210, USA
| | - Indira Mohanty
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA, 99210, USA
| | - Charles Mariasoosai
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, 992020, USA
| | - Peter Obi
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, 992020, USA
| | - Paul Panipinto
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, 992020, USA
| | - Smarajit Bandyopadhyay
- Molecular Biotechnology Core Laboratory, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Santanu Bose
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA, 99210, USA
| | - Senthil Natesan
- Department of Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, 992020, USA.
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6
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Cai T, Lenoir Capello R, Pi X, Wu H, Chou JJ. Structural basis of γ -chain family receptor sharing at the membrane level. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.05.539662. [PMID: 37205582 PMCID: PMC10187304 DOI: 10.1101/2023.05.05.539662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The common γ-chain (γc) family of cytokine receptors, including interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 receptors, are activated upon engagement with the common γc receptor in ligand dependent manner. Sharing of γc by the IL receptors (ILRs) is thought to be achieved by concomitant binding of γc and ILR ectodomains to a cytokine. Here, we found that direct interactions between the transmembrane domain (TMD) of γc and those of the ILRs are also required for receptor activation, and remarkably, the same γc TMD can specifically recognize multiple ILR TMDs of diverse sequences. Heterodimer structures of γc TMD bound to the TMDs of IL-7R and IL-9R, determined in near lipid bilayer environment, reveal a conserved knob-into-hole mechanism of recognition that mediates receptor sharing within the membrane. Functional mutagenesis data indicate the requirement of the heterotypic interactions of TMDs in signaling, which could explain disease mutations within the receptor TMDs. One-Sentence Summary The transmembrane anchors of interleukin receptors of the gamma-chain family are critical for receptor sharing and activation.
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7
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Wang Z, Huo T, Wu H, Moussa Z, Sen M, Dalton V. Full-length αIIbβ3 CryoEM structure reveals intact integrin initiate-activation intrinsic architecture. RESEARCH SQUARE 2023:rs.3.rs-2394542. [PMID: 36865117 PMCID: PMC9980189 DOI: 10.21203/rs.3.rs-2394542/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Integrin αIIbβ3 is the key receptor regulating platelet retraction and accumulation, thus pivotal for hemostasis, and arterial thrombosis as well as a proven drug-target for antithrombotic therapies. Here we resolve the cryoEM structures of the intact full-length αIIbβ3, which covers three distinct states along the activation pathway. Here, we resolve intact αIIbβ3 structure at 3Å resolution, revealing the overall topology of the heterodimer with the transmembrane (TM) helices and the head region ligand-binding domain tucked in a specific angle proximity to the TM region. In response to the addition of an Mn2+ agonist, we resolved two coexisting states, "intermediate" and "pre-active". Our structures show conformational changes of the intact αIIbβ3 activating trajectory, as well as a unique twisting of the lower integrin legs representing intermediate state (TM region at a twisting conformation) integrin and a coexisting pre-active state (bent and opening in leg), which is required for inducing the transitioning platelets to accumulate. Our structure provides for the first time direct structural evidence for the lower legs' involvement in full-length integrin activation mechanisms. Additionally, our structure offers a new strategy to target the αIIbβ3 lower leg allosterically instead of modulating the affinity of the αIIbβ3 head region.
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8
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Bhattacharjya S. The structural basis of β2 integrin intra-cellular multi-protein complexes. Biophys Rev 2022; 14:1183-1195. [PMID: 36345283 PMCID: PMC9636337 DOI: 10.1007/s12551-022-00995-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/24/2022] [Indexed: 01/03/2023] Open
Abstract
In multicellular organisms, cell adhesion is a pivotal physiological process which is essential for cell-cell communications, cell migration, and interactions with extracellular matrix. Integrins, a family of large hetero-dimeric type I membrane proteins, are known for driving cell adhesion functions. Among 24 different integrins, four β2 integrins, αL β2, αM β2, αX β2 and αD β2, are specific for cell adhesion and migration of leukocytes. Many cytosolic proteins interact with short cytosolic tails (CTs) of β2 and other integrins which are essential in bi-directional signaling processes. Further, phosphorylation of CTs of integrins regulates binding of intra-cellular proteins and signaling systems. In this review, recent advances in structures and interactions of multi-protein complexes of integrin tails, with a focus on β2 integrin, and cytosolic proteins are discussed along with a proposed future direction.
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Affiliation(s)
- Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551 Singapore
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9
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Su Y, Iacob RE, Li J, Engen JR, Springer TA. Dynamics of integrin α5β1, fibronectin, and their complex reveal sites of interaction and conformational change. J Biol Chem 2022; 298:102323. [PMID: 35931112 PMCID: PMC9483561 DOI: 10.1016/j.jbc.2022.102323] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 12/04/2022] Open
Abstract
Integrin α5β1 mediates cell adhesion to the extracellular matrix by binding fibronectin (Fn). Selectivity for Fn by α5β1 is achieved through recognition of an RGD motif in the 10th type III Fn domain (Fn10) and the synergy site in the ninth type III Fn domain (Fn9). However, details of the interaction dynamics are unknown. Here, we compared synergy-site and Fn-truncation mutations for their α5β1-binding affinities and stabilities. We also interrogated binding of the α5β1 ectodomain headpiece fragment to Fn using hydrogen-deuterium exchange (HDX) mass spectrometry to probe binding sites and sites of integrin conformational change. Our results suggest the synergistic effect of Fn9 requires both specific residues and a folded domain. We found some residues considered important for synergy are required for stability. Additionally, we show decreases in fibronectin HDX are localized to a synergy peptide containing contacting residues in two β-strands, an intervening loop in Fn9, and the RGD-containing loop in Fn10, indicative of binding sites. We also identified binding sites in the α5-subunit β-propeller domain for the Fn9 synergy site and in the β1-subunit βI domain for Fn10 based on decreases in α5β1 HDX. Interestingly, the dominant effect of Fn binding was an increase in α5β1 deuterium exchange distributed over multiple sites that undergo changes in conformation or solvent accessibility and appear to be sites where energy is stored in the higher-energy, open-integrin conformation. Together, our results highlight regions important for α5β1 binding to Fn and dynamics associated with this interaction.
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Affiliation(s)
- Yang Su
- Program in Cellular and Molecular Medicine, Boston Children's Hospital; Departments of Biological Chemistry and Molecular Pharmacology and of Pediatrics, Harvard Medical School, Boston, MA 02115
| | - Roxana E Iacob
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA 02115
| | - Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital; Departments of Biological Chemistry and Molecular Pharmacology and of Pediatrics, Harvard Medical School, Boston, MA 02115
| | - John R Engen
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA 02115
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital; Departments of Biological Chemistry and Molecular Pharmacology and of Pediatrics, Harvard Medical School, Boston, MA 02115.
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10
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Anderson JM, Li J, Springer TA. Regulation by metal ions and the ADMIDAS of integrin α5β1 conformational states and intrinsic affinities. Mol Biol Cell 2022; 33:ar56. [PMID: 35108026 PMCID: PMC9265148 DOI: 10.1091/mbc.e21-11-0536] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activation of integrins by Mn2+ is a benchmark in the integrin field, but how Mn2+ works and whether it reproduces physiological activation is unknown. We show that Mn2+ and high Mg2+ concentrations compete with Ca2+ at the ADMIDAS and shift the conformational equilibrium toward the open state, but the shift is far from complete. Additionally, replacement of Mg2+ by Mn2+ at the MIDAS increases the intrinsic affinities of both the high-affinity open and low-affinity closed states of integrins, in agreement with stronger binding of Mn2+ than Mg2+ to oxygen atoms. Mutation of the ADMIDAS increases the affinity of closed states and decreases the affinity of the open state and thus reduces the difference in affinity between the open and closed states. An important biological function of the ADMIDAS may be to stabilize integrins in highly discrete states, so that when integrins support cell adhesion and migration, their high and low affinity correspond to discrete on and off states, respectively.
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Affiliation(s)
- Jordan M Anderson
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston MA 02115.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston MA 02115
| | - Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston MA 02115.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston MA 02115
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston MA 02115.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston MA 02115
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11
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Kratochvil HT, Newberry RW, Mensa B, Mravic M, DeGrado WF. Spiers Memorial Lecture: Analysis and de novo design of membrane-interactive peptides. Faraday Discuss 2021; 232:9-48. [PMID: 34693965 PMCID: PMC8979563 DOI: 10.1039/d1fd00061f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Membrane-peptide interactions play critical roles in many cellular and organismic functions, including protection from infection, remodeling of membranes, signaling, and ion transport. Peptides interact with membranes in a variety of ways: some associate with membrane surfaces in either intrinsically disordered conformations or well-defined secondary structures. Peptides with sufficient hydrophobicity can also insert vertically as transmembrane monomers, and many associate further into membrane-spanning helical bundles. Indeed, some peptides progress through each of these stages in the process of forming oligomeric bundles. In each case, the structure of the peptide and the membrane represent a delicate balance between peptide-membrane and peptide-peptide interactions. We will review this literature from the perspective of several biologically important systems, including antimicrobial peptides and their mimics, α-synuclein, receptor tyrosine kinases, and ion channels. We also discuss the use of de novo design to construct models to test our understanding of the underlying principles and to provide useful leads for pharmaceutical intervention of diseases.
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Affiliation(s)
- Huong T Kratochvil
- Department of Pharmaceutical Chemistry, University of California - San Francisco, San Francisco, CA 94158, USA.
| | - Robert W Newberry
- Department of Pharmaceutical Chemistry, University of California - San Francisco, San Francisco, CA 94158, USA.
| | - Bruk Mensa
- Department of Pharmaceutical Chemistry, University of California - San Francisco, San Francisco, CA 94158, USA.
| | - Marco Mravic
- Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California - San Francisco, San Francisco, CA 94158, USA.
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12
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Li J, Yan J, Springer TA. Low affinity integrin states have faster ligand binding kinetics than the high affinity state. eLife 2021; 10:73359. [PMID: 34854380 PMCID: PMC8730728 DOI: 10.7554/elife.73359] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 12/01/2021] [Indexed: 11/29/2022] Open
Abstract
Integrin conformational ensembles contain two low-affinity states, bent-closed and extended-closed, and an active, high-affinity, extended-open state. It is widely thought that integrins must be activated before they bind ligand; however, one model holds that activation follows ligand binding. As ligand-binding kinetics are not only rate limiting for cell adhesion but also have important implications for the mechanism of activation, we measure them here for integrins α4β1 and α5β1 and show that the low-affinity states bind substantially faster than the high-affinity state. On- and off-rates are similar for integrins on cell surfaces and as ectodomain fragments. Although the extended-open conformation’s on-rate is ~20-fold slower, its off-rate is ~25,000-fold slower, resulting in a large affinity increase. The tighter ligand-binding pocket in the open state may slow its on-rate. Low-affinity integrin states not only bind ligand more rapidly, but are also more populous on the cell surface than high-affinity states. Thus, our results suggest that integrin binding to ligand may precede, rather than follow, activation by ‘inside-out signaling.’
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Affiliation(s)
- Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
| | - Jiabin Yan
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
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13
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Wang Z, Zhu J. Structural determinants of the integrin transmembrane domain required for bidirectional signal transmission across the cell membrane. J Biol Chem 2021; 297:101318. [PMID: 34678312 PMCID: PMC8569584 DOI: 10.1016/j.jbc.2021.101318] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 10/12/2021] [Accepted: 10/18/2021] [Indexed: 11/26/2022] Open
Abstract
Studying the tight activity regulation of platelet-specific integrin αIIbβ3 is foundational and paramount to our understanding of integrin structure and activation. αIIbβ3 is essential for the aggregation and adhesion function of platelets in hemostasis and thrombosis. Structural and mutagenesis studies have previously revealed the critical role of αIIbβ3 transmembrane (TM) association in maintaining the inactive state. Gain-of-function TM mutations were identified and shown to destabilize the TM association leading to integrin activation. Studies using isolated TM peptides have suggested an altered membrane embedding of the β3 TM α-helix coupled with αIIbβ3 activation. However, controversies remain as to whether and how the TM α-helices change their topologies in the context of full-length integrin in native cell membrane. In this study, we utilized proline scanning mutagenesis and cysteine scanning accessibility assays to analyze the structure and function correlation of the αIIbβ3 TM domain. Our identification of loss-of-function proline mutations in the TM domain suggests the requirement of a continuous TM α-helical structure in transmitting activation signals bidirectionally across the cell membrane, characterized by the inside-out activation for ligand binding and the outside-in signaling for cell spreading. Similar results were found for αLβ2 and α5β1 TM domains, suggesting a generalizable mechanism. We also detected a topology change of β3 TM α-helix within the cell membrane, but only under conditions of cell adhesion and the absence of αIIb association. Our data demonstrate the importance of studying the structure and function of the integrin TM domain in the native cell membrane.
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Affiliation(s)
- Zhengli Wang
- Blood Research Institute, Versiti, Milwaukee, Wisconsin, USA
| | - Jieqing Zhu
- Blood Research Institute, Versiti, Milwaukee, Wisconsin, USA; Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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14
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Sun G, Guillon E, Holley SA. Integrin intra-heterodimer affinity inversely correlates with integrin activatability. Cell Rep 2021; 35:109230. [PMID: 34107244 PMCID: PMC8227800 DOI: 10.1016/j.celrep.2021.109230] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 03/13/2021] [Accepted: 05/17/2021] [Indexed: 11/21/2022] Open
Abstract
Integrins are heterodimeric cell surface receptors composed of an α and β subunit that mediate cell adhesion to extracellular matrix proteins such as fibronectin. We previously studied integrin α5β1 activation during zebrafish somitogenesis, and in the present study, we characterize the integrin αV fibronectin receptors. Integrins are activated via a conformational change, and we perform single-molecule biophysical measurements of both integrin activation via fluorescence resonance energy transfer (FRET)-fluorescence lifetime imaging microscopy (FLIM) and integrin intra-heterodimer stability via fluorescence cross-correlation spectroscopy (FCCS) in living embryos. We find that integrin heterodimers that exhibit robust cell surface expression, including αVβ3, αVβ5, and αVβ6, are never activated in this in vivo context, even in the presence of fibronectin matrix. In contrast, activatable integrins, such as integrin αVβ1, and alleles of αVβ3, αVβ5, αVβ6 that are biased to the active conformation exhibit poor cell surface expression and have a higher intra-heterodimer dissociation constant (KD). These observations suggest that a weak integrin intra-heterodimer affinity decreases integrin cell surface stability and increases integrin activatability.
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Affiliation(s)
- Guangyu Sun
- Department of Molecular, Cellular and Developmental Biology, Yale University, 260 Whitney Avenue, New Haven, CT 06520, USA
| | - Emilie Guillon
- Department of Molecular, Cellular and Developmental Biology, Yale University, 260 Whitney Avenue, New Haven, CT 06520, USA
| | - Scott A Holley
- Department of Molecular, Cellular and Developmental Biology, Yale University, 260 Whitney Avenue, New Haven, CT 06520, USA.
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15
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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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16
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Song G, Luo BH. Effects of the association of the α v β 8 lower legs on integrin ligand binding. J Cell Biochem 2021; 122:801-813. [PMID: 33619784 DOI: 10.1002/jcb.29912] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 02/08/2021] [Accepted: 02/10/2021] [Indexed: 12/18/2022]
Abstract
Many integrins transmit signals through global conformational changes. However, it is unclear whether integrin αv β8 adopts a similar mechanism during integrin activation and signaling on the cell surface. Here, we showed that disulfide-bonded mutants, which prevented integrin αv β8 lower leg dissociation, bound ligands with similar level as the wild-type protein, suggesting that αv β8 ligand binding did not require lower leg disassociation. We further showed that the N-glycosylation mutant at the interface between the β I and hybrid domains did not affect ligand binding, suggesting that the αv β8 open headpiece was not present on the cell surface. We proposed that αv β8 integrin may adopt only one state, that is, the extended conformation with a closed headpiece. Our results showed that two lower legs retained heterodimeric interfaces, and this association might be important for stabilizing integrin in the extended conformation. Therefore, αv β8 may not transmit bidirectional signals across the plasma membrane but instead may serve as an anchoring site with high affinity and high accessibility for extracellular ligands.
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Affiliation(s)
- Guannan Song
- Department of Life Science, University of Louisiana State University, Baton Rouge, Louisiana, USA
| | - Bing-Hao Luo
- Department of Life Science, University of Louisiana State University, Baton Rouge, Louisiana, USA
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17
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Song G, Luo BH. Atypical structure and function of integrin α V β 8. J Cell Physiol 2020; 236:4874-4887. [PMID: 33368230 DOI: 10.1002/jcp.30242] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/10/2020] [Accepted: 12/12/2020] [Indexed: 12/12/2022]
Abstract
Integrins are heterodimeric transmembrane proteins that play important roles in various biological processes. Most integrins serve as adhesion molecules and transmit bidirectional signaling across the cell membrane through global conformational changes from the bent closed to the extended open conformation. However, integrin β8 is distinctive in structure and function. Its cytoplasmic domain lacks the conserved protein-binding sequence, which is important in transmitting inside-out signals, suggesting that integrin β8 may have a different activation mechanism or lack such signaling. In addition, the ligand-binding or activating metal ion Mn2+ does not induce a global conformational change in integrin β8 . It may have only one conformation, that is, an extended, closed conformation, but with high affinity for ligands under physiological conditions, and is, therefore, considered an atypical integrin member. The extended structure and high ligand-binding affinity of integrin αv β8 make it ideal for encountering and binding ligands expressed on an opposing cell or in the extracellular matrix. In this review, we summarize the progress in integrin β8 research with a focus on its distinctive function and structure among integrin members.
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Affiliation(s)
- Guannan Song
- Department of Life Science, University of Louisiana State University, Baton Rouge, Louisiana, USA
| | - Bing-Hao Luo
- Department of Life Science, University of Louisiana State University, Baton Rouge, Louisiana, USA
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18
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Leddon SA, Fettis MM, Abramo K, Kelly R, Oleksyn D, Miller J. The CD28 Transmembrane Domain Contains an Essential Dimerization Motif. Front Immunol 2020; 11:1519. [PMID: 32765524 PMCID: PMC7378745 DOI: 10.3389/fimmu.2020.01519] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 06/09/2020] [Indexed: 12/13/2022] Open
Abstract
CD28 plays a critical role in regulating immune responses both by enhancing effector T cell activation and differentiation and controlling the development and function of regulatory T cells. CD28 is expressed at the cell surface as a disulfide linked homodimer that is thought to bind ligand monovalently. How ligand binding triggers CD28 to induce intracellular signaling as well as the proximal signaling pathways that are induced are not well-understood. In addition, recent data suggest inside-out signaling initiated by the T cell antigen receptor can enhance CD28 ligand binding, possibly by inducing a rearrangement of the CD28 dimer interface to allow for bivalent binding. To understand how possible conformational changes during ligand-induced receptor triggering and inside-out signaling are mediated, we examined the CD28 transmembrane domain. We identified an evolutionarily conserved YxxxxT motif that is shared with CTLA-4 and resembles the transmembrane dimerization motif within CD3ζ. We show that the CD28 transmembrane domain can drive protein dimerization in a bacterial expression system at levels equivalent to the well-known glycophorin A transmembrane dimerization motif. In addition, ectopic expression of the CD28 transmembrane domain into monomeric human CD25 can drive dimerization in murine T cells as detected by an increase in FRET by flow cytometry. Mutation of the polar YxxxxT motif to hydrophobic leucine residues (Y145L/T150L) attenuated CD28 transmembrane mediated dimerization in both the bacterial and mammalian assays. Introduction of the Y145L/T150L mutation of the CD28 transmembrane dimerization motif into the endogenous CD28 locus by CRISPR resulted in a dramatic loss in CD28 cell surface expression. These data suggest that under physiological conditions the YxxxxT dimerization motif within the CD28 transmembrane domain plays a critical role in the assembly and/or expression of stable CD28 dimers at the cell surface.
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Affiliation(s)
- Scott A Leddon
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - Margaret M Fettis
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - Kristin Abramo
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - Ryan Kelly
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - David Oleksyn
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - Jim Miller
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
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19
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Torres-Gomez A, Cabañas C, Lafuente EM. Phagocytic Integrins: Activation and Signaling. Front Immunol 2020; 11:738. [PMID: 32425937 PMCID: PMC7203660 DOI: 10.3389/fimmu.2020.00738] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 03/31/2020] [Indexed: 01/06/2023] Open
Abstract
Phagocytic integrins are endowed with the ability to engulf and dispose of particles of different natures. Evolutionarily conserved from worms to humans, they are involved in pathogen elimination and apoptotic and tumoral cell clearance. Research in the field of integrin-mediated phagocytosis has shed light on the molecular events controlling integrin activation and their effector functions. However, there are still some aspects of the regulation of the phagocytic process that need to be clarified. Here, we have revised the molecular events controlling phagocytic integrin activation and the downstream signaling driving particle engulfment, and we have focused particularly on αMβ2/CR3, αXβ2/CR4, and a brief mention of αVβ5/αVβ3integrins.
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Affiliation(s)
- Alvaro Torres-Gomez
- Department of Immunology, Ophthalmology and Otorhinolaryngology, School of Medicine, Universidad Complutense de Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12), Madrid, Spain
| | - Carlos Cabañas
- Department of Immunology, Ophthalmology and Otorhinolaryngology, School of Medicine, Universidad Complutense de Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12), Madrid, Spain.,Severo Ochoa Center for Molecular Biology (CSIC-UAM), Madrid, Spain
| | - Esther M Lafuente
- Department of Immunology, Ophthalmology and Otorhinolaryngology, School of Medicine, Universidad Complutense de Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12), Madrid, Spain
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20
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Chen SH, Perez-Aguilar JM, Zhou R. Graphene-extracted membrane lipids facilitate the activation of integrin α vβ 8. NANOSCALE 2020; 12:7939-7949. [PMID: 32232233 DOI: 10.1039/c9nr10469k] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Despite the remarkable electrochemical properties of graphene, strong van der Waals attraction between graphene and biomolecules often causes cytotoxicity, which hinders its applications in the biomedical field. Unfortunately, surface passivation of graphene might stimulate undesired immune response as the nanomaterial triggers cytokine production through membrane receptor activation. Herein, we use all-atom Molecular Dynamics (MD) simulations to unravel the underlying mechanism of graphene-induced inside-out activation of integrin αvβ8, a prominent membrane receptor expressed in immune cells. We model the transmembrane (TM) domains of integrin αvβ8 in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer and observe the structural changes in the integrin-membrane complex when interacting with a graphene nanosheet across the membrane. We find that the β8 TM domain interacts with the graphene nanosheet directly or indirectly through extracted lipids, facilitating the pulling of a β8 subunit away from an αv subunit and thus leading to the disruption of the TM domain association by breaking the hydrophobic cluster in the cytoplasmic domains of the αv and β8 subunits. Alanine substitution of two conserved phenylalanine residues on the αv subunit at this hydrophobic cluster further reveals the importance of a stable T-shaped structure in retaining integrin in its inactive state. Our results agree with previous studies on the interactions between other integrin subtypes and their endogenous activators, suggesting an intriguing role that the graphene nanosheet may play in the integrin-related signal transduction during its interaction with the membrane.
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Affiliation(s)
- Serena H Chen
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA.
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21
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Klimovich PS, Semina EV, Karagyaur MN, Rysenkova KD, Sysoeva VY, Mironov NA, Sagaradze GD, Az'muko AA, Popov VS, Rubina KA, Tkachuk VA. Urokinase receptor regulates nerve regeneration through its interaction with α5β1-integrin. Biomed Pharmacother 2020; 125:110008. [PMID: 32187956 DOI: 10.1016/j.biopha.2020.110008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 01/30/2020] [Accepted: 02/12/2020] [Indexed: 10/24/2022] Open
Abstract
PURPOSE Urokinase receptor (uPAR) promotes extracellular matrix proteolysis, regulates adhesion and cell migration, transduces intracellular signals through interactions with the lateral partners. The expression of uPAR and urokinase (uPA) is significantly upregulated in peripheral nerves after injury, however, little is known about uPAR function in nerve regeneration or the molecular mechanisms involved. The purpose of this study is to investigate the role of uPAR in nerve regeneration after traumatic injury of n. Peroneus communis in uPA-/-, uPAR-/- or control mice (WT) and in neuritogenesis in an in vitro Neuro 2A cell model. RESULTS Electrophysiological analysis indicates that nerve recovery is significantly impaired in uPAR-/- mice, but not in uPA-/- mice. These data correlate with the reduced amount of NF200-positive axons in regenerating nerves from uPAR-/- mice compared to uPA-/- or control mice. There is an increase in uPAR expression and remarkable colocalization of uPAR with α5 and β1 integrin in uPA-/- mice in recovering nerves, pointing to a potential link between uPAR and its lateral partner α5β1-integrin. Using an in vitro model of neuritogenesis and α325 blocking peptide, which abrogates uPAR-α5β1 interaction in Neuro 2A cells but has no effect on their function, we have further confirmed the significance of uPAR-α5β1 interaction. CONCLUSION Taken together, we report evidence pointing to an important role of uPAR, rather than uPA, in peripheral nerve recovery and neuritogenesis.
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Affiliation(s)
- P S Klimovich
- Laboratory of Molecular Endocrinology, Federal State Budgetary Organization National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 3d Cherepkovskaya st. 15а, Moscow, 121552, Russia; Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia
| | - E V Semina
- Laboratory of Molecular Endocrinology, Federal State Budgetary Organization National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 3d Cherepkovskaya st. 15а, Moscow, 121552, Russia; Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia.
| | - M N Karagyaur
- Institute of Regenerative Medicine, Medical Research and Education Center, Lomonosov Moscow State University, Lomonosovsky av. 27-10, Moscow, 119191, Russia
| | - K D Rysenkova
- Laboratory of Molecular Endocrinology, Federal State Budgetary Organization National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 3d Cherepkovskaya st. 15а, Moscow, 121552, Russia; Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia
| | - V Yu Sysoeva
- Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia
| | - N A Mironov
- Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia
| | - G D Sagaradze
- Institute of Regenerative Medicine, Medical Research and Education Center, Lomonosov Moscow State University, Lomonosovsky av. 27-10, Moscow, 119191, Russia
| | - A A Az'muko
- Laboratory for the Synthesis of Peptides, Federal State Budgetary Organization National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 3d Cherepkovskaya st. 15а, Moscow, 121552, Russia
| | - V S Popov
- Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia
| | - K A Rubina
- Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia; Laboratory of Morphogenesis and Tissue Reparation, Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia
| | - V A Tkachuk
- Laboratory of Molecular Endocrinology, Federal State Budgetary Organization National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 3d Cherepkovskaya st. 15а, Moscow, 121552, Russia; Faculty of Medicine, Lomonosov Moscow State University, Lomonosovsky av. 27-1, Moscow, 119991, Russia; Institute of Regenerative Medicine, Medical Research and Education Center, Lomonosov Moscow State University, Lomonosovsky av. 27-10, Moscow, 119191, Russia
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22
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Kulke M, Langel W. Molecular dynamics simulations to the bidirectional adhesion signaling pathway of integrin α V β 3. Proteins 2019; 88:679-688. [PMID: 31693219 DOI: 10.1002/prot.25849] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 10/10/2019] [Accepted: 11/03/2019] [Indexed: 12/27/2022]
Abstract
The bidirectional force transmission process of integrin through the cell membrane is still not well understood. Several possible mechanisms have been discussed in literature on the basis of experimental data, and in this study, we investigate these mechanisms by free and steered molecular dynamics simulations. For the first time, constant velocity pulling on the complete integrin molecule inside a dipalmitoyl-phosphatidylcholine membrane is conducted. From the results, the most likely mechanism for inside-out and outside-in signaling is the switchblade model with further separation of the transmembrane helices.
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Affiliation(s)
- Martin Kulke
- Institut für Biochemie, Universität Greifswald, Greifswald, Germany
| | - Walter Langel
- Institut für Biochemie, Universität Greifswald, Greifswald, Germany
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23
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Moore TI, Aaron J, Chew TL, Springer TA. Measuring Integrin Conformational Change on the Cell Surface with Super-Resolution Microscopy. Cell Rep 2019; 22:1903-1912. [PMID: 29444440 PMCID: PMC5851489 DOI: 10.1016/j.celrep.2018.01.062] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/19/2017] [Accepted: 01/19/2018] [Indexed: 02/08/2023] Open
Abstract
We use super-resolution interferometric photoactivation and localization microscopy (iPALM) and a constrained photoactivatable fluorescent protein integrin fusion to measure the displacement of the head of integrin lymphocyte function-associated 1 (LFA-1) resulting from integrin conformational change on the cell surface. We demonstrate that the distance of the LFA-1 head increases substantially between basal and ligand-engaged conformations, which can only be explained at the molecular level by integrin extension. We further demonstrate that one class of integrin antagonist maintains the bent conformation, while another antagonist class induces extension. Our molecular scale measurements on cell-surface LFA-1 are in excellent agreement with distances derived from crystallographic and electron microscopy structures of bent and extended integrins. Our distance measurements are also in excellent agreement with a previous model of LFA-1 bound to ICAM-1 derived from the orientation of LFA-1 on the cell surface measured using fluorescence polarization microscopy.
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Affiliation(s)
- Travis I Moore
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Jesse Aaron
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Teng-Leong Chew
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Timothy A Springer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
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24
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Unique transmembrane domain interactions differentially modulate integrin αvβ3 and αIIbβ3 function. Proc Natl Acad Sci U S A 2019; 116:12295-12300. [PMID: 31160446 DOI: 10.1073/pnas.1904867116] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lateral transmembrane (TM) helix-helix interactions between single-span membrane proteins play an important role in the assembly and signaling of many cell-surface receptors. Often, these helices contain two highly conserved yet distinct interaction motifs, arranged such that the motifs cannot be engaged simultaneously. However, there is sparse experimental evidence that dual-engagement mechanisms play a role in biological signaling. Here, we investigate the function of the two conserved interaction motifs in the TM domain of the integrin β3-subunit. The first motif uses reciprocating "large-large-small" amino acid packing to mediate the interaction of the β3 and αIIb TM domains and maintain the inactive resting conformation of the platelet integrin αIIbβ3. The second motif, S-x3-A-x3-I, is a variant of the classical "G-x3-G" motif. Using site-directed mutagenesis, optical trap-based force spectroscopy, and molecular modeling, we show that S-x3-A-x3-I does not engage αIIb but rather mediates the interaction of the β3 TM domain with the TM domain of the αv-subunit of the integrin αvβ3. Like αIIbβ3, αvβ3 on circulating platelets is inactive, and in the absence of platelet stimulation is unable to interact with components of the subendothelial matrix. However, disrupting any residue in the β3 S-x3-A-x3-I motif by site-directed mutations is sufficient to induce αvβ3 binding to the αvβ3 ligand osteopontin and to the monoclonal antibody WOW-1. Thus, the β3-integrin TM domain is able to engage in two mutually exclusive interactions that produce alternate α-subunit pairing, creating two integrins with distinct biological functions.
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26
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Autonomous conformational regulation of β 3 integrin and the conformation-dependent property of HPA-1a alloantibodies. Proc Natl Acad Sci U S A 2018; 115:E9105-E9114. [PMID: 30209215 DOI: 10.1073/pnas.1806205115] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Integrin α/β heterodimer adopts a compact bent conformation in the resting state, and upon activation undergoes a large-scale conformational rearrangement. During the inside-out activation, signals impinging on the cytoplasmic tail of β subunit induce the α/β separation at the transmembrane and cytoplasmic domains, leading to the extended conformation of the ectodomain with the separated leg and the opening headpiece that is required for the high-affinity ligand binding. It remains enigmatic which integrin subunit drives the bent-to-extended conformational rearrangement in the inside-out activation. The β3 integrins, including αIIbβ3 and αVβ3, are the prototypes for understanding integrin structural regulation. The Leu33Pro polymorphism located at the β3 PSI domain defines the human platelet-specific alloantigen (HPA) 1a/b, which provokes the alloimmune response leading to clinically important bleeding disorders. Some, but not all, anti-HPA-1a alloantibodies can distinguish the αIIbβ3 from αVβ3 and affect their functions with unknown mechanisms. Here we designed a single-chain β3 subunit that mimics a separation of α/β heterodimer on inside-out activation. Our crystallographic and functional studies show that the single-chain β3 integrin folds into a bent conformation in solution but spontaneously extends on the cell surface. This demonstrates that the β3 subunit autonomously drives the membrane-dependent conformational rearrangement during integrin activation. Using the single-chain β3 integrin, we identified the conformation-dependent property of anti-HPA-1a alloantibodies, which enables them to differently recognize the β3 in the bent state vs. the extended state and in the complex with αIIb vs. αV This study provides deeper understandings of integrin conformational activation on the cell surface.
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27
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Differential Binding of Active and Inactive Integrin to Talin. Protein J 2018; 37:280-289. [PMID: 29785642 DOI: 10.1007/s10930-018-9776-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Bi-directional signaling of integrins plays an important role in platelet and leukocyte function. Talin plays a key role in integrin bi-directional signaling and its binding to integrin is highly regulated. The precise regulation of the recruitment and binding of talin to integrin is still being elucidated. In particular, the recruitment of talin to integrin is controlled by the RAP-1 and RIAM/lamellipodin signaling axis and the affinity between talin and integrin is regulated by the conformation or protease cleavage of talin. However, whether the binding between integrin and talin is also regulated by integrin conformation has not been thoroughly explored before. In this work, we used biochemical binding assays to study the potential role of integrin conformational changes in integrin-talin interactions. Constitutively active integrin αIIbb3 binds markedly stronger to talin than inactive αIIbb3. Inactive αIIbb3 markedly increases its binding to talin once activated, regardless of how αIIbb3 is activated. Further, the increased binding to talin is b3 tail dependent. Our results suggest that integrin conformation is another regulatory mechanism for integrin-talin interaction.
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28
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Pagani G, Gohlke H. On the contributing role of the transmembrane domain for subunit-specific sensitivity of integrin activation. Sci Rep 2018; 8:5733. [PMID: 29636500 PMCID: PMC5893634 DOI: 10.1038/s41598-018-23778-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 03/20/2018] [Indexed: 12/20/2022] Open
Abstract
Integrins are α/β heterodimeric transmembrane adhesion receptors. Evidence exists that their transmembrane domain (TMD) separates upon activation. Subunit-specific differences in activation sensitivity of integrins were reported. However, whether sequence variations in the TMD lead to differential TMD association has remained elusive. Here, we show by molecular dynamics simulations and association free energy calculations on TMDs of integrin αIIbβ3, αvβ3, and α5β1 that αIIbβ3 TMD is most stably associated; this difference is related to interaction differences across the TMDs. The order of TMD association stability is paralleled by the basal activity of these integrins, which suggests that TMD differences can have a decisive effect on integrin conformational free energies. We also identified a specific order of clasp disintegration upon TMD dissociation, which suggests that the closed state of integrins may comprise several microstates. Our results provide unprecedented insights into a possibly contributing role of TMD towards subunit-specific sensitivity of integrin activation.
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Affiliation(s)
- Giulia Pagani
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich-Heine-Universität Düsseldorf, 40225, Düsseldorf, Germany
| | - Holger Gohlke
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich-Heine-Universität Düsseldorf, 40225, Düsseldorf, Germany.
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC) & Institute for Complex Systems - Structural Biochemistry (ICS 6), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
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29
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Thinn AMM, Wang Z, Zhu J. The membrane-distal regions of integrin α cytoplasmic domains contribute differently to integrin inside-out activation. Sci Rep 2018; 8:5067. [PMID: 29568062 PMCID: PMC5864728 DOI: 10.1038/s41598-018-23444-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 03/13/2018] [Indexed: 12/20/2022] Open
Abstract
Functioning as signal receivers and transmitters, the integrin α/β cytoplasmic tails (CT) are pivotal in integrin activation and signaling. 18 α integrin subunits share a conserved membrane-proximal region but have a highly diverse membrane-distal (MD) region at their CTs. Recent studies demonstrated that the presence of α CTMD region is essential for talin-induced integrin inside-out activation. However, it remains unknown whether the non-conserved α CTMD regions differently regulate the inside-out activation of integrin. Using αIIbβ3, αLβ2, and α5β1 as model integrins and by replacing their α CTMD regions with those of α subunits that pair with β3, β2, and β1 subunits, we analyzed the function of CTMD regions of 17 α subunits in talin-mediated integrin activation. We found that the α CTMD regions play two roles on integrin, which are activation-supportive and activation-regulatory. The regulatory but not the supportive function depends on the sequence identity of α CTMD region. A membrane-proximal tyrosine residue present in the CTMD regions of a subset of α integrins was identified to negatively regulate integrin inside-out activation. Our study provides a useful resource for investigating the function of α integrin CTMD regions.
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Affiliation(s)
- Aye Myat Myat Thinn
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI, 53226, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Zhengli Wang
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI, 53226, USA
| | - Jieqing Zhu
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI, 53226, USA.
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
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30
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Ju L, McFadyen JD, Al-Daher S, Alwis I, Chen Y, Tønnesen LL, Maiocchi S, Coulter B, Calkin AC, Felner EI, Cohen N, Yuan Y, Schoenwaelder SM, Cooper ME, Zhu C, Jackson SP. Compression force sensing regulates integrin α IIbβ 3 adhesive function on diabetic platelets. Nat Commun 2018; 9:1087. [PMID: 29540687 PMCID: PMC5852038 DOI: 10.1038/s41467-018-03430-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 02/09/2018] [Indexed: 01/25/2023] Open
Abstract
Diabetes is associated with an exaggerated platelet thrombotic response at sites of vascular injury. Biomechanical forces regulate platelet activation, although the impact of diabetes on this process remains ill-defined. Using a biomembrane force probe (BFP), we demonstrate that compressive force activates integrin αIIbβ3 on discoid diabetic platelets, increasing its association rate with immobilized fibrinogen. This compressive force-induced integrin activation is calcium and PI 3-kinase dependent, resulting in enhanced integrin affinity maturation and exaggerated shear-dependent platelet adhesion. Analysis of discoid platelet aggregation in the mesenteric circulation of mice confirmed that diabetes leads to a marked enhancement in the formation and stability of discoid platelet aggregates, via a mechanism that is not inhibited by therapeutic doses of aspirin and clopidogrel, but is eliminated by PI 3-kinase inhibition. These studies demonstrate the existence of a compression force sensing mechanism linked to αIIbβ3 adhesive function that leads to a distinct prothrombotic phenotype in diabetes.
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Affiliation(s)
- Lining Ju
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - James D McFadyen
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - Saheb Al-Daher
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - Imala Alwis
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - Yunfeng Chen
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Coulter Department of Biomedical Engineering; and Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, 30332, USA
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, 92037, CA, USA
| | - Lotte L Tønnesen
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - Sophie Maiocchi
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
| | - Brianna Coulter
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
| | - Anna C Calkin
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
- Lipid Metabolism and Cardiometabolic Disease Laboratory, Baker Heart and Diabetes Institute, Melbourne, Victoria, 3004, Australia
| | - Eric I Felner
- Division of Pediatric Endocrinology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Neale Cohen
- Clinical Diabetes, Baker Heart and Diabetes Institute, Melbourne, Victoria, 3004, Australia
| | - Yuping Yuan
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - Simone M Schoenwaelder
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia
| | - Mark E Cooper
- Department of Diabetes, Central Clinical School, Monash University, Melbourne, 3004, Victoria, Australia
| | - Cheng Zhu
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia.
- Coulter Department of Biomedical Engineering; and Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
| | - Shaun P Jackson
- Heart Research Institute, Thrombosis Group, Newtown, New South Wales, 2042, Australia.
- Charles Perkins Centre, Level 3E Cardiovascular Division, The University of Sydney, New South Wales, 2006, Australia.
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia.
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, 92037, CA, USA.
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31
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High integrin α Vβ 6 affinity reached by hybrid domain deletion slows ligand-binding on-rate. Proc Natl Acad Sci U S A 2018; 115:E1429-E1436. [PMID: 29378937 DOI: 10.1073/pnas.1718662115] [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] [Indexed: 11/18/2022] Open
Abstract
The role of the hybrid domain in integrin affinity regulation is unknown, as is whether the kinetics of ligand binding is modulated by integrin affinity state. Here, we compare cell surface and soluble integrin αVβ6 truncation mutants for ligand-binding affinity, kinetics, and thermodynamics. Removal of the integrin transmembrane/cytoplasmic domains or lower legs has little effect on αVβ6 affinity, in contrast to β1 integrins. In integrin opening, rearrangement at the interface between the βI and hybrid domains is linked to remodeling at the ligand-binding site at the opposite end of the βI domain, which greatly increases in affinity in the open conformation. The larger size of the βI-hybrid interface in the closed state suggests that the hybrid domain stabilizes closing. In agreement, deletion of the hybrid domain raised affinity by 50-fold. Surface plasmon resonance and isothermal titration calorimetry gave similar results and the latter revealed tradeoffs between enthalpy and entropy not apparent from affinity. At extremely high affinity reached in Mn2+ with hybrid domain truncation, αVβ6 on-rate for both pro-TGF-β1 and fibronectin declined. The results suggest that the open conformation of αVβ6 has lower on-rate than the closed conformation, correlate with constriction of the ligand-binding pocket in open αVβ6 structures, and suggest that the extended-closed conformation is kinetically selected for ligand binding. Subsequent transition to the extended-open conformation is stabilized by its much higher affinity for ligand and would also be stabilized by force exerted across ligand-bound integrins by the actin cytoskeleton.
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32
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Hanein D, Volkmann N. Conformational Equilibrium of Human Platelet Integrin Investigated by Three-Dimensional Electron Cryo-Microscopy. Subcell Biochem 2018; 87:353-363. [PMID: 29464566 DOI: 10.1007/978-981-10-7757-9_12] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Integrins are bidirectional transmembrane receptors that play central roles in hemostasis and arterial thrombosis. They have been subject to structural studies for many years, in particular using X-ray crystallography, nuclear magnetic resonance spectroscopy, and two-dimensional negative stain electron microscopy. Despite considerable progress, a full consensus on the molecular mechanism of integrin activation is still lacking. Three-dimensional reconstructions of full-length human platelet integrin αIIbβ3 in lipid-bilayer nanodiscs obtained by electron cryo-microscopy and single-particle reconstruction have shed new light on the activation process. These studies show that integrin αIIbβ3 exists in a continuous conformational equilibrium ranging from a compact nodular conformation similar to that obtained in crystal structures to a fully extended state with the leg domains separated. This equilibrium is shifted towards the extended conformation when extracellular ligands, cytosolic activators and lipid-bilayer nanodiscs are added. Addition of cytosolic activators and extracellular ligands in the absense of nanodiscs produces significantly less dramatic shifts, emphasizing the importance of the membrane bilayer in the activation process.
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Affiliation(s)
- Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford-Burnham-Prebys Medical Discovery Institute, San Diego, CA, USA
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford-Burnham-Prebys Medical Discovery Institute, San Diego, CA, USA.
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33
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Nordenfelt P, Moore TI, Mehta SB, Kalappurakkal JM, Swaminathan V, Koga N, Lambert TJ, Baker D, Waters JC, Oldenbourg R, Tani T, Mayor S, Waterman CM, Springer TA. Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration. Nat Commun 2017; 8:2047. [PMID: 29229906 PMCID: PMC5725580 DOI: 10.1038/s41467-017-01848-y] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 10/20/2017] [Indexed: 12/31/2022] Open
Abstract
Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here, we test whether the integrin, when engaged to an extracellular ligand and the cytoskeleton, adopts a specific orientation dictated by the direction of actin flow on the surface of migrating cells. We insert GFP into the rigid, ligand-binding head of the integrin, model with Rosetta the orientation of GFP and its transition dipole relative to the integrin head, and measure orientation with fluorescence polarization microscopy. Cytoskeleton and ligand-bound integrins orient in the same direction as retrograde actin flow with their cytoskeleton-binding β-subunits tilted by applied force. The measurements demonstrate that intracellular forces can orient cell surface integrins and support a molecular model of integrin activation by cytoskeletal force. Our results place atomic, Å-scale structures of cell surface receptors in the context of functional and cellular, μm-scale measurements. Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here the authors show that actin flow can orient cell surface integrins during leukocyte migration, suggesting integrin activation by cytoskeletal force.
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Affiliation(s)
- Pontus Nordenfelt
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Division of Infection Medicine, Department of Clinical Sciences Lund, Faculty of Medicine, Lund University, Lund, 221 84, Sweden
| | - Travis I Moore
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Shalin B Mehta
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Chan Zuckerberg Biohub, San Francisco, CA, 94158, USA
| | - Joseph Mathew Kalappurakkal
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,National Center for Biological Sciences, Bangalore, 560065, India
| | - Vinay Swaminathan
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Cell Biology and Physiology Center, NHLBI, NIH, Bethesda, MD, 20824, USA
| | - Nobuyasu Koga
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA.,Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan
| | - Talley J Lambert
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - David Baker
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA
| | - Jennifer C Waters
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Rudolf Oldenbourg
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Tomomi Tani
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Satyajit Mayor
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,National Center for Biological Sciences, Bangalore, 560065, India
| | - Clare M Waterman
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.,Cell Biology and Physiology Center, NHLBI, NIH, Bethesda, MD, 20824, USA
| | - Timothy A Springer
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA. .,Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA. .,Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA.
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34
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Nurden AT, Pillois X. ITGA2B and ITGB3 gene mutations associated with Glanzmann thrombasthenia. Platelets 2017; 29:98-101. [PMID: 29125375 DOI: 10.1080/09537104.2017.1371291] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Alan T Nurden
- a Institut de Rhythmologie et de Modélisation Cardiaque, Plateforme Technologique d'Innovation Biomédicale, Hôpital Xavier Arnozan , Pessac , France
| | - Xavier Pillois
- a Institut de Rhythmologie et de Modélisation Cardiaque, Plateforme Technologique d'Innovation Biomédicale, Hôpital Xavier Arnozan , Pessac , France.,b Université de Bordeaux, INSERM U1034 , Pessac , France
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35
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Li J, Springer TA. Energy landscape differences among integrins establish the framework for understanding activation. J Cell Biol 2017; 217:397-412. [PMID: 29122968 PMCID: PMC5748972 DOI: 10.1083/jcb.201701169] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 09/15/2017] [Accepted: 10/04/2017] [Indexed: 11/22/2022] Open
Abstract
Li and Springer demonstrate differences between integrins α4β1 and α5β1 in intrinsic affinities and relative free energies of three conformational states. Integrin conformational equilibria are both subunit and cell type specific. The energy landscapes of intact receptors on the cell surface provide a framework for understanding regulation of integrin adhesiveness. Why do integrins differ in basal activity, and how does affinity for soluble ligand correlate with cellular adhesiveness? We show that basal conformational equilibrium set points for integrin α4β1 are cell type specific and differ from integrin α5β1 when the two integrins are coexpressed on the same cell. Although α4β1 is easier to activate, its high-affinity state binds vascular cell adhesion molecule and fibronectin 100- to 1,000-fold more weakly than α5β1 binds fibronectin. Furthermore, the difference in affinity between the high- and low-affinity states is more compressed in α4β1 (600- to 800-fold) than in α5β1 (4,000- to 6,000-fold). α4β1 basal conformational equilibria differ among three cell types, define affinity for soluble ligand and readiness for priming, and may reflect differences in interactions with intracellular adaptors but do not predict cellular adhesiveness for immobilized ligand. The measurements here provide a necessary framework for understanding integrin activation in intact cells, including activation of integrin adhesiveness by application of tensile force by the cytoskeleton, across ligand–integrin–adaptor complexes.
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Affiliation(s)
- Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA .,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA
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36
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Anderson SM, Mueller BK, Lange EJ, Senes A. Combination of Cα-H Hydrogen Bonds and van der Waals Packing Modulates the Stability of GxxxG-Mediated Dimers in Membranes. J Am Chem Soc 2017; 139:15774-15783. [PMID: 29028318 PMCID: PMC5927632 DOI: 10.1021/jacs.7b07505] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The GxxxG motif is frequently found at the dimerization interface of a transmembrane structural motif called GASright, which is characterized by a short interhelical distance and a right-handed crossing angle between the helices. In GASright dimers, such as glycophorin A (GpA), BNIP3, and members of the ErbB family, the backbones of the helices are in contact, and they invariably display networks of 4 to 8 weak hydrogen bonds between Cα-H carbon donors and carbonyl acceptors on opposing helices (Cα-H···O═C hydrogen bonds). These networks of weak hydrogen bonds at the helix-helix interface are presumably stabilizing, but their energetic contribution to dimerization has yet to be determined experimentally. Here, we present a computational and experimental structure-based analysis of GASright dimers of different predicted stabilities, which show that a combination of van der Waals packing and Cα-H hydrogen bonding predicts the experimental trend of dimerization propensities. This finding provides experimental support for the hypothesis that the networks of Cα-H hydrogen bonds are major contributors to the free energy of association of GxxxG-mediated dimers. The structural comparison between groups of GASright dimers of different stabilities reveals distinct sequence as well as conformational preferences. Stability correlates with shorter interhelical distances, narrower crossing angles, better packing, and the formation of larger networks of Cα-H hydrogen bonds. The identification of these structural rules provides insight on how nature could modulate stability in GASright and finely tune dimerization to support biological function.
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Affiliation(s)
- Samantha M Anderson
- Department of Biochemistry, University of Wisconsin-Madison , 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - Benjamin K Mueller
- Department of Biochemistry, University of Wisconsin-Madison , 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - Evan J Lange
- Department of Biochemistry, University of Wisconsin-Madison , 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - Alessandro Senes
- Department of Biochemistry, University of Wisconsin-Madison , 433 Babcock Drive, Madison, Wisconsin 53706, United States
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37
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Gao J, Huang M, Lai J, Mao K, Sun P, Cao Z, Hu Y, Zhang Y, Schulte ML, Jin C, Wang J, White GC, Xu Z, Ma YQ. Kindlin supports platelet integrin αIIbβ3 activation by interacting with paxillin. J Cell Sci 2017; 130:3764-3775. [PMID: 28954813 DOI: 10.1242/jcs.205641] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 09/18/2017] [Indexed: 12/30/2022] Open
Abstract
Kindlins play an important role in supporting integrin activation by cooperating with talin; however, the mechanistic details remain unclear. Here, we show that kindlins interacted directly with paxillin and that this interaction could support integrin αIIbβ3 activation. An exposed loop in the N-terminal F0 subdomain of kindlins was involved in mediating the interaction. Disruption of kindlin binding to paxillin by structure-based mutations significantly impaired the function of kindlins in supporting integrin αIIbβ3 activation. Both kindlin and talin were required for paxillin to enhance integrin activation. Interestingly, a direct interaction between paxillin and the talin head domain was also detectable. Mechanistically, paxillin, together with kindlin, was able to promote the binding of the talin head domain to integrin, suggesting that paxillin complexes with kindlin and talin to strengthen integrin activation. Specifically, we observed that crosstalk between kindlin-3 and the paxillin family in mouse platelets was involved in supporting integrin αIIbβ3 activation and in vivo platelet thrombus formation. Taken together, our findings uncover a novel mechanism by which kindlin supports integrin αIIbβ3 activation, which might be beneficial for developing safer anti-thrombotic therapies.
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Affiliation(s)
- Juan Gao
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Ming Huang
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Jingjing Lai
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Kaijun Mao
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Peisen Sun
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Zhongyuan Cao
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Youpei Hu
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Yingying Zhang
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China
| | - Marie L Schulte
- Blood Research Institute, Blood Center of Wisconsin, Wisconsin, WI 53226, USA
| | - Chaozhi Jin
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences, Beijing 102206, China
| | - Jian Wang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences, Beijing 102206, China
| | - Gilbert C White
- Blood Research Institute, Blood Center of Wisconsin, Wisconsin, WI 53226, USA.,Department of Biochemistry, Medical College of Milwaukee, Wisconsin, WI 53226, USA
| | - Zhen Xu
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China .,Blood Research Institute, Blood Center of Wisconsin, Wisconsin, WI 53226, USA
| | - Yan-Qing Ma
- Collaborative Research Program for Cell Adhesion Molecules, Shanghai University School of Life Sciences, Shanghai 200444, China .,Blood Research Institute, Blood Center of Wisconsin, Wisconsin, WI 53226, USA.,Department of Biochemistry, Medical College of Milwaukee, Wisconsin, WI 53226, USA
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38
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The importance of N-glycosylation on β 3 integrin ligand binding and conformational regulation. Sci Rep 2017; 7:4656. [PMID: 28680094 PMCID: PMC5498496 DOI: 10.1038/s41598-017-04844-w] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 05/19/2017] [Indexed: 11/25/2022] Open
Abstract
N-glycosylations can regulate the adhesive function of integrins. Great variations in both the number and distribution of N-glycosylation sites are found in the 18 α and 8 β integrin subunits. Crystal structures of αIIbβ3 and αVβ3 have resolved the precise structural location of each N-glycan site, but the structural consequences of individual N-glycan site on integrin activation remain unclear. By site-directed mutagenesis and structure-guided analyses, we dissected the function of individual N-glycan sites in β3 integrin activation. We found that the N-glycan site, β3-N320 at the headpiece and leg domain interface positively regulates αIIbβ3 but not αVβ3 activation. The β3-N559 N-glycan at the β3-I-EGF3 and αIIb-calf-1 domain interface, and the β3-N654 N-glycan at the β3-β-tail and αIIb-calf-2 domain interface positively regulate the activation of both αIIbβ3 and αVβ3 integrins. In contrast, removal of the β3-N371 N-glycan near the β3 hybrid and I-EGF3 interface, or the β3-N452 N-glycan at the I-EGF1 domain rendered β3 integrin more active than the wild type. We identified one unique N-glycan at the βI domain of β1 subunit that negatively regulates α5β1 activation. Our study suggests that the bulky N-glycans influence the large-scale conformational rearrangement by potentially stabilizing or destabilizing the domain interfaces of integrin.
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39
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Integrin extension enables ultrasensitive regulation by cytoskeletal force. Proc Natl Acad Sci U S A 2017; 114:4685-4690. [PMID: 28416675 DOI: 10.1073/pnas.1704171114] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Integrins undergo large-scale conformational changes upon activation. Signaling events driving integrin activation have previously been discussed conceptually, but not quantitatively. Here, recent measurements of the intrinsic ligand-binding affinity and free energy of each integrin conformational state on the cell surface, together with the length scales of conformational change, are used to quantitatively compare models of activation. We examine whether binding of cytoskeletal adaptors to integrin cytoplasmic domains is sufficient for activation or whether exertion of tensile force by the actin cytoskeleton across the integrin-ligand complex is also required. We find that only the combination of adaptor binding and cytoskeletal force provides ultrasensitive regulation. Moreover, switch-like activation by force depends on the large, >130 Å length-scale change in integrin extension, which is well tailored to match the free-energy difference between the inactive (bent-closed) and active (extended-open) conformations. The length scale and energy cost in integrin extension enable activation by force in the low pN range and appear to be the key specializations that enable cell adhesion through integrins to be coordinated with cytoskeletal dynamics.
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40
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Nurden AT. Should studies on Glanzmann thrombasthenia not be telling us more about cardiovascular disease and other major illnesses? Blood Rev 2017; 31:287-299. [PMID: 28395882 DOI: 10.1016/j.blre.2017.03.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/23/2017] [Indexed: 12/17/2022]
Abstract
Glanzmann thrombasthenia (GT) is a rare inherited bleeding disorder caused by loss of αIIbβ3 integrin function in platelets. Most genetic variants of β3 also affect the widely expressed αvβ3 integrin. With brief mention of mouse models, I now look at the consequences of disease-causing ITGA2B and ITGB3 mutations on the non-hemostatic functions of platelets and other cells. Reports of arterial thrombosis in GT patients are rare, but other aspects of cardiovascular disease do occur including deep vein thrombosis and congenital heart defects. Thrombophilic and other risk factors for thrombosis and lessons from heterozygotes and variant forms of GT are discussed. Assessed for GT patients are reports of leukemia and cancer, loss of fertility, bone pathology, inflammation and wound repair, infections, kidney disease, autism and respiratory disease. This survey shows an urgent need for a concerted international effort to better determine how loss of αIIbβ3 and αvβ3 influences health and disease.
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Affiliation(s)
- Alan T Nurden
- Institut de Rhythmologie et de Modélisation Cardiaque, Plateforme Technologique d'Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France.
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Li J, Su Y, Xia W, Qin Y, Humphries MJ, Vestweber D, Cabañas C, Lu C, Springer TA. Conformational equilibria and intrinsic affinities define integrin activation. EMBO J 2017; 36:629-645. [PMID: 28122868 PMCID: PMC5331762 DOI: 10.15252/embj.201695803] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/12/2016] [Accepted: 12/15/2016] [Indexed: 11/25/2022] Open
Abstract
We show that the three conformational states of integrin α5β1 have discrete free energies and define activation by measuring intrinsic affinities for ligand of each state and the equilibria linking them. The 5,000-fold higher affinity of the extended-open state than the bent-closed and extended-closed states demonstrates profound regulation of affinity. Free energy requirements for activation are defined with protein fragments and intact α5β1 On the surface of K562 cells, α5β1 is 99.8% bent-closed. Stabilization of the bent conformation by integrin transmembrane and cytoplasmic domains must be overcome by cellular energy input to stabilize extension. Following extension, headpiece opening is energetically favored. N-glycans and leg domains in each subunit that connect the ligand-binding head to the membrane repel or crowd one another and regulate conformational equilibria in favor of headpiece opening. The results suggest new principles for regulating signaling in the large class of receptors built from extracellular domains in tandem with single-span transmembrane domains.
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Affiliation(s)
- Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Yang Su
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Wei Xia
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Yan Qin
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Martin J Humphries
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester, UK
| | | | - Carlos Cabañas
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM) and Departamento de Microbiología I Facultad de Medicina UCM, Madrid, Spain
| | - Chafen Lu
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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42
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Role of the Helix in Talin F3 Domain (F3 Helix) in Talin-Mediated Integrin Activation. Cell Biochem Biophys 2017; 75:79-86. [PMID: 28101696 DOI: 10.1007/s12013-017-0781-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 01/09/2017] [Indexed: 02/05/2023]
Abstract
Increases in ligand binding to cellular integrins (activation) play an important role in platelet and leukocyte function. Talin is necessary in vivo and sufficient in vitro for integrin αIIbβ3 activation. The precise mechanisms by which talin activates integrin are still being elucidated. In particular, talin undergoes conformational changes (around the F3 helix) and inserts the F3 helix into lipid bilayer; however, the connection between this lipid-inserting mechanism of talin and talin's capacity to activate integrin has never been explored before. In this work, we used rational mutagenesis, modeled cell systems, and structural modeling to study the potential role of membrane-induced talin conformational changes in talin-mediated integrin activation. Mutations of the residues critical for talin F3 helix to insert into membrane completely abolished talin-mediated integrin activation without affecting the binding of talin to integrins. Furthermore, mutations of the lipid-binding sequences in talin F3 helix significantly reduced the capacity of talin to activate integrin. Our results suggest that the F3 helix may contribute to talin-mediated integrin activation.
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43
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Xu XP, Kim E, Swift M, Smith JW, Volkmann N, Hanein D. Three-Dimensional Structures of Full-Length, Membrane-Embedded Human α(IIb)β(3) Integrin Complexes. Biophys J 2016; 110:798-809. [PMID: 26910421 DOI: 10.1016/j.bpj.2016.01.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 12/08/2015] [Accepted: 01/13/2016] [Indexed: 10/22/2022] Open
Abstract
Integrins are bidirectional, allosteric transmembrane receptors that play a central role in hemostasis and arterial thrombosis. Using cryo-electron microscopy, multireference single-particle reconstruction methods, and statistics-based computational fitting approaches, we determined three-dimensional structures of human integrin αIIbβ3 embedded in a lipid bilayer (nanodiscs) while bound to domains of the cytosolic regulator talin and to extracellular ligands. We also determined the conformations of integrin in solution by itself to localize the membrane and the talin-binding site. To our knowledge, our data provide unprecedented three-dimensional information about the conformational states of intact, full-length integrin within membrane bilayers under near-physiological conditions and in the presence of cytosolic activators and extracellular ligands. We show that αIIbβ3 integrins exist in a conformational equilibrium clustered around four main states. These conformations range from a compact bent nodule to two partially extended intermediate conformers and finally to a fully upright state. In the presence of nanodiscs and the two ligands, the equilibrium is significantly shifted toward the upright conformation. In this conformation, the receptor extends ∼20 nm upward from the membrane. There are no observable contacts between the two subunits other than those in the headpiece near the ligand-binding pocket, and the α- and β-subunits are well separated with their cytoplasmic tails ∼8 nm apart. Our results indicate that extension of the ectodomain is possible without separating the legs or extending the hybrid domain, and that the ligand-binding pocket is not occluded by the membrane in any conformations of the equilibrium. Further, they suggest that integrin activation may be influenced by equilibrium shifts.
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Affiliation(s)
- Xiao-Ping Xu
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Eldar Kim
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Mark Swift
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Jeffrey W Smith
- Infectious Disease Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
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44
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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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45
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Structural and functional aspects of decorsin and its analog as recognized by integrin αIIbβ3. J Mol Model 2016; 22:281. [PMID: 27796783 DOI: 10.1007/s00894-016-3147-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 10/09/2016] [Indexed: 10/20/2022]
Abstract
Decorsin is an antagonist of platelet glycoprotein integrin αIIbβ3 on platelets; the protein is 39 amino acids long with three disulfide bridges in its tertiary structure. To demonstrate decorsin's mechanism of action, we applied the computational virtual technique and platelet aggregation inhibition assay, which showed that the flanking amino-acid residues of the Arg-Gly-Asp (RGD) motif play an important role in platelet aggregation. The computational simulations revealed that the RGD motif mainly contributes to the stability of the complex when decorsion interacts with integrin αIIbβ3. However, the C-terminal residues, such as 34A→W and 35D→R, was also found to possibly play a key role in their binding structures. Moreover, we produced a decorsin analog (A34W plus D35R decorsin), in which the 34A (alanine) and 35D (aspartic acid) residues were respectively substituted by W (tryptophan) and R (arginine). This isoform was then recombinantly expressed in Escherichia coli. Intriguingly, this mutant type showed higher anti-platelet aggregation activity than the wildtype. Our study may further contribute to finding decorsin mutants with higher anti-platelet aggregation activity.
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46
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Fan Z, Ley K. Leukocyte arrest: Biomechanics and molecular mechanisms of β2 integrin activation. Biorheology 2016; 52:353-77. [PMID: 26684674 DOI: 10.3233/bir-15085] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Integrins are a group of heterodimeric transmembrane receptors that play essential roles in cell-cell and cell-matrix interaction. Integrins are important in many physiological processes and diseases. Integrins acquire affinity to their ligand by undergoing molecular conformational changes called activation. Here we review the molecular biomechanics during conformational changes of integrins, integrin functions in leukocyte biorheology (adhesive functions during rolling and arrest) and molecules involved in integrin activation.
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Affiliation(s)
- Zhichao Fan
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA
| | - Klaus Ley
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.,Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
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47
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A conserved αβ transmembrane interface forms the core of a compact T-cell receptor-CD3 structure within the membrane. Proc Natl Acad Sci U S A 2016; 113:E6649-E6658. [PMID: 27791034 DOI: 10.1073/pnas.1611445113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The T-cell antigen receptor (TCR) is an assembly of eight type I single-pass membrane proteins that occupies a central position in adaptive immunity. Many TCR-triggering models invoke an alteration in receptor complex structure as the initiating event, but both the precise subunit organization and the pathway by which ligand-induced alterations are transferred to the cytoplasmic signaling domains are unknown. Here, we show that the receptor complex transmembrane (TM) domains form an intimately associated eight-helix bundle organized by a specific interhelical TCR TM interface. The salient features of this core structure are absolutely conserved between αβ and γδ TCR sequences and throughout vertebrate evolution, and mutations at key interface residues caused defects in the formation of stable TCRαβ:CD3δε:CD3γε:ζζ complexes. These findings demonstrate that the eight TCR-CD3 subunits form a compact and precisely organized structure within the membrane and provide a structural basis for further investigation of conformationally regulated models of transbilayer TCR signaling.
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48
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Bennett JS. Regulation of integrins in platelets. Biopolymers 2016; 104:323-33. [PMID: 26010651 DOI: 10.1002/bip.22679] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 05/07/2015] [Accepted: 05/08/2015] [Indexed: 11/08/2022]
Abstract
Blood platelets prevent bleeding after trauma by forming occlusive aggregates at sites of vascular injury. Platelet aggregation is mediated by the integrin heterodimer αIIbβ3 and occurs when platelet agonists generated at the injury site convert αIIbβ3 from its resting to its active conformation. Active αIIbβ3 is then able to bind macromolecular ligands such as fibrinogen that crosslink adjacent platelets into hemostatic aggregates. Platelets circulate in a plasma milieu containing high concentrations of the principal αIIbβ3 ligand fibrinogen. Thus, αIIbβ3 activity is tightly regulated to prevent the spontaneous formation of platelet aggregates. αIIbβ3 activity is regulated at least three levels. First, intramolecular interactions involving motifs located in the membrane-proximal stalk regions, transmembrane domains, and the membrane-proximal cytosolic tails of αIIb and β3 maintain αIIbβ3 in its inactive conformation. Transmembrane domain interactions appear particularly important because disrupting these interactions causes constitutive αIIbβ3 activation. Second, the agonist-stimulated binding of the cytosolic proteins talin and kindlin-3 to the β3 cytosolic tail rapidly causes αIIbβ3 activation by disrupting the intramolecular interactions constraining αIIbβ3 activity. Third, the strength of ligand binding to active αIIbβ3 seems to be allosterically regulated. Thus, αIIbβ3 exists in a minimum of three interconvertible states: an inactive (resting) state that does not interact with ligands and two active ligand binding states that differ in their affinity for fibrinogen and in the mechanical stability of fibrinogen complexes they form.
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Affiliation(s)
- Joel S Bennett
- Hematology-Oncology Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania Philadelphia, 19104, Pennsylvania
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49
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Fu Q, Fu TM, Cruz AC, Sengupta P, Thomas SK, Wang S, Siegel RM, Wu H, Chou JJ. Structural Basis and Functional Role of Intramembrane Trimerization of the Fas/CD95 Death Receptor. Mol Cell 2016; 61:602-613. [PMID: 26853147 DOI: 10.1016/j.molcel.2016.01.009] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Revised: 11/17/2015] [Accepted: 01/04/2016] [Indexed: 11/30/2022]
Abstract
Fas (CD95, Apo-1, or TNFRSF6) is a prototypical apoptosis-inducing death receptor in the tumor necrosis factor receptor (TNFR) superfamily. While the extracellular domains of TNFRs form trimeric complexes with their ligands and the intracellular domains engage in higher-order oligomerization, the role of the transmembrane (TM) domains is unknown. We determined the NMR structures of mouse and human Fas TM domains in bicelles that mimic lipid bilayers. Surprisingly, these domains use proline motifs to create optimal packing in homotrimer assembly distinct from classical trimeric coiled-coils in solution. Cancer-associated and structure-based mutations in Fas TM disrupt trimerization in vitro and reduce apoptosis induction in vivo, indicating the essential role of intramembrane trimerization in receptor activity. Our data suggest that the structures represent the signaling-active conformation of Fas TM, which appears to be different from the pre-ligand conformation. Analysis of other TNFR sequences suggests proline-containing sequences as common motifs for receptor TM trimerization.
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Affiliation(s)
- Qingshan Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Tian-Min Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Anthony C Cruz
- Immunoregulation Section, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20892, USA
| | - Prabuddha Sengupta
- Section on Organelle Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA
| | - Stacy K Thomas
- Immunoregulation Section, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20892, USA
| | - Shuqing Wang
- School of Pharmacy, Tianjin Medical University, Tianjin 300070, China
| | - Richard M Siegel
- Immunoregulation Section, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20892, USA
| | - Hao Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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50
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Trenker R, Call ME, Call MJ. Crystal Structure of the Glycophorin A Transmembrane Dimer in Lipidic Cubic Phase. J Am Chem Soc 2015; 137:15676-9. [PMID: 26642914 DOI: 10.1021/jacs.5b11354] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanisms of assembly and function for many important type I/II (single-pass) transmembrane (TM) receptors are proposed to involve the formation and/or alteration of specific interfaces among their membrane-embedded α-helical TM domains. The application of lipidic cubic phase (LCP) bilayer media for crystallization of single-α-helical TM complexes has the potential to provide valuable structural and mechanistic insights into many such systems. However, the fidelity of the interfaces observed in crowded crystalline arrays has been difficult to establish from the very limited number of such structures determined using X-ray diffraction data. Here we examine this issue using the glycophorin A (GpA) model system, whose homodimeric TM helix interface has been characterized by solution and solid-state NMR and biochemical techniques but never crystallographically. We report that a GpA-TM peptide readily crystallized in a monoolein cubic phase bilayer, yielding a dimeric α-helical structure that is in excellent agreement with previously reported NMR measurements made in several different types of host media. These results provide compelling support for the wider application of LCP techniques to enable X-ray crystallographic analysis of single-pass TM interactions.
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Affiliation(s)
- Raphael Trenker
- Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research , Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne , Parkville, Victoria 3052, Australia
| | - Matthew E Call
- Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research , Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne , Parkville, Victoria 3052, Australia
| | - Melissa J Call
- Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research , Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne , Parkville, Victoria 3052, Australia
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