1
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Liu J, Lu Y, Zheng B, Huang D, Song J, Wang B, Zheng S. Talin1 promotes HCC progression by regulating NRG1/PI3K/AKT pathway. Discov Oncol 2024; 15:360. [PMID: 39162903 PMCID: PMC11335986 DOI: 10.1007/s12672-024-01243-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 08/14/2024] [Indexed: 08/21/2024] Open
Abstract
OBJECTIVE OF THE STUDY Hepatocellular carcinoma (HCC) stands as the third leading cause of cancer-related mortality globally. Metastasis, responsible for treatment failures, underscores the urgency to comprehend molecular drivers of invasion and migration. Central to the invasive and migratory processes underlying metastasis is the protein Talin1. However, the role and underlying mechanisms governing Talin1's involvement in HCC have remained elusive. METHODS A total of 100 HCC specimens were collected from patients who underwent hepatectomy in our center. The expression level of talin1 was measured to evaluate the correlationship of talin1 and the development of HCC. In vitro and in vivo experiments were conducted to verify the characteristic of talin1 in HCC. RNA-seq and bioinformatics analysis were performed to identify the downstream signal pathway of talin1 and their impact on HCC development. RESULTS Here, we reported elevated levels of Talin1 mRNA and protein in HCC tissues. Meanwhile, downregulation of Talin1 significantly reduced the HCC cell proliferation and metastasis in vitro and in vivo. Furthermore, elevating NRG-1, a downstream target of Talin1, enhanced metastasis of HCC cells. More importantly, attenuation of Talin1 inhibited HCC progression through decreasing the stabilization of NRG1 mRNA, consequently regulating the expression of NRG1 and its involvement in mediating the PI3K/AKT pathway. CONCLUSION Taken together, Talin1 regulates cellular proliferation, metastasis, and invasiveness by modulating NRG1/PI3K/AKT axis, suggesting that Talin1 emerges as a promising candidate for treating HCC.
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Affiliation(s)
- Jialong Liu
- Insititute of Hepatobiliary Surgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yao Lu
- Insititute of Hepatobiliary Surgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Bowen Zheng
- Insititute of Hepatobiliary Surgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Deng Huang
- Department of Hepatobiliary, General Hospital of Tibet Military Command Area, Lhasa, Tibet, China
| | - Juxian Song
- Department of Hepatobiliary Surgery, The 925th Hospital of the PLA, Guiyang, Guizhou, China
| | - Baolin Wang
- Department of Surgery, The 63650th Troop Hospital of the Chinese People's Liberation Army, Korla, Xinjiang, China
| | - Shuguo Zheng
- Insititute of Hepatobiliary Surgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China.
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2
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Xin H, Huang J, Song Z, Mao J, Xi X, Shi X. Structure, signal transduction, activation, and inhibition of integrin αIIbβ3. Thromb J 2023; 21:18. [PMID: 36782235 PMCID: PMC9923933 DOI: 10.1186/s12959-023-00463-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 02/06/2023] [Indexed: 02/15/2023] Open
Abstract
Integrins are heterodimeric receptors comprising α and β subunits. They are expressed on the cell surface and play key roles in cell adhesion, migration, and growth. Several types of integrins are expressed on the platelets, including αvβ3, αIIbβ3, α2β1, α5β1, and α6β1. Among these, physically αIIbβ3 is exclusively expressed on the platelet surface and their precursor cells, megakaryocytes. αIIbβ3 adopts at least three conformations: i) bent-closed, ii) extended-closed, and iii) extended-open. The transition from conformation i) to iii) occurs when αIIbβ3 is activated by stimulants. Conformation iii) possesses a high ligand affinity, which triggers integrin clustering and platelet aggregation. Platelets are indispensable for maintaining vascular system integrity and preventing bleeding. However, excessive platelet activation can result in myocardial infarction (MI) and stroke. Therefore, finding a novel strategy to stop bleeding without accelerating the risk of thrombosis is important. Regulation of αIIbβ3 activation is vital for this strategy. There are a large number of molecules that facilitate or inhibit αIIbβ3 activation. The interference of these molecules can accurately control the balance between hemostasis and thrombosis. This review describes the structure and signal transduction of αIIbβ3, summarizes the molecules that directly or indirectly affect integrin αIIbβ3 activation, and discusses some novel antiαIIbβ3 drugs. This will advance our understanding of the activation of αIIbβ3 and its essential role in platelet function and tumor development.
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Affiliation(s)
- Honglei Xin
- grid.452511.6Department of Hematology, Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210003 China
| | - Jiansong Huang
- grid.13402.340000 0004 1759 700XDepartment of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang, Hangzhou 310003 China ,grid.412277.50000 0004 1760 6738Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025 China
| | - Zhiqun Song
- grid.412676.00000 0004 1799 0784Jiangsu Province People’s Hospital and Nanjing Medical University First Affiliated Hospital, Nanjing, Jiangsu 210029 China
| | - Jianhua Mao
- grid.412277.50000 0004 1760 6738Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025 China
| | - Xiaodong Xi
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
| | - Xiaofeng Shi
- Department of Hematology, Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210003, China. .,Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, Collaborative Innovation Center of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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3
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Wen L, Lyu Q, Ley K, Goult BT. Structural Basis of β2 Integrin Inside—Out Activation. Cells 2022; 11:cells11193039. [PMID: 36231001 PMCID: PMC9564206 DOI: 10.3390/cells11193039] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 09/19/2022] [Accepted: 09/27/2022] [Indexed: 11/16/2022] Open
Abstract
β2 integrins are expressed on all leukocytes. Precise regulation of the β2 integrin is critical for leukocyte adhesion and trafficking. In neutrophils, β2 integrins participate in slow rolling. When activated by inside–out signaling, fully activated β2 integrins mediate rapid leukocyte arrest and adhesion. The two activation pathways, starting with selectin ligand engagement and chemokine receptor ligation, respectively, converge on phosphoinositide 3-kinase, talin-1, kindlin-3 and Rap1. Here, we focus on recent structural insights into autoinhibited talin-1 and autoinhibited trimeric kindlin-3. When activated, both talin-1 and kindlin-3 can bind the β2 cytoplasmic tail at separate but adjacent sites. We discuss possible pathways for talin-1 and kindlin-3 activation, recruitment to the plasma membrane, and their role in integrin activation. We propose new models of the final steps of integrin activation involving the complex of talin-1, kindlin-3, integrin and the plasma membrane.
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Affiliation(s)
- Lai Wen
- Department of Pharmacology, Center for Molecular and Cellular Signaling in the Cardiovascular System, Reno School of Medicine, University of Nevada, Reno, NV 89577, USA
- Center for Autoimmunity and Inflammation, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | - Qingkang Lyu
- Center for Autoimmunity and Inflammation, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
- Immunology Center of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Klaus Ley
- Center for Autoimmunity and Inflammation, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
- Immunology Center of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Benjamin T. Goult
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
- Correspondence: ; Tel.: +44-(0)1227-816-142
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4
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Fan S, Boerner K, Muraleedharan CK, Nusrat A, Quiros M, Parkos CA. Epithelial JAM-A is fundamental for intestinal wound repair in vivo. JCI Insight 2022; 7:e158934. [PMID: 35943805 PMCID: PMC9536273 DOI: 10.1172/jci.insight.158934] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 08/03/2022] [Indexed: 12/01/2022] Open
Abstract
Junctional adhesion molecule-A (JAM-A) is expressed in several cell types, including epithelial and endothelial cells, as well as some leukocytes. In intestinal epithelial cells (IEC), JAM-A localizes to cell junctions and plays a role in regulating barrier function. In vitro studies with model cell lines have shown that JAM-A contributes to IEC migration; however, in vivo studies investigating the role of JAM-A in cell migration-dependent processes such as mucosal wound repair have not been performed. In this study, we developed an inducible intestinal epithelial-specific JAM-A-knockdown mouse model (Jam-aERΔIEC). While acute induction of IEC-specific loss of JAM-A did not result in spontaneous colitis, such mice had significantly impaired mucosal healing after chemically induced colitis and after biopsy colonic wounding. In vitro primary cultures of JAM-A-deficient IEC demonstrated impaired migration in wound healing assays. Mechanistic studies revealed that JAM-A stabilizes formation of protein signaling complexes containing Rap1A/Talin/β1 integrin at focal adhesions of migrating IECs. Loss of JAM-A in primary IEC led to decreased Rap1A activity and protein levels of Talin and β1 integrin, and it led to a reduction in focal adhesion structures. These findings suggest that epithelial JAM-A plays a critical role in controlling mucosal repair in vivo through dynamic regulation of focal adhesions.
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5
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Azizi L, Varela L, Turkki P, Mykuliak VV, Korpela S, Ihalainen TO, Church J, Hytönen VP, Goult BT. Talin variant P229S compromises integrin activation and associates with multifaceted clinical symptoms. Hum Mol Genet 2022; 31:4159-4172. [PMID: 35861643 PMCID: PMC9759328 DOI: 10.1093/hmg/ddac163] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 06/13/2022] [Accepted: 07/12/2022] [Indexed: 01/21/2023] Open
Abstract
Adhesion of cells to the extracellular matrix (ECM) must be exquisitely coordinated to enable development and tissue homeostasis. Cell-ECM interactions are regulated by multiple signalling pathways that coordinate the activation state of the integrin family of ECM receptors. The protein talin is pivotal in this process, and talin's simultaneous interactions with the cytoplasmic tails of the integrins and the plasma membrane are essential to enable robust, dynamic control of integrin activation and cell-ECM adhesion. Here, we report the identification of a de novo heterozygous c.685C>T (p.Pro229Ser) variant in the TLN1 gene from a patient with a complex phenotype. The mutation is located in the talin head region at the interface between the F2 and F3 domains. The characterization of this novel p.P229S talin variant reveals the disruption of adhesion dynamics that result from disturbance of the F2-F3 domain interface in the talin head. Using biophysical, computational and cell biological techniques, we find that the variant perturbs the synergy between the integrin-binding F3 and the membrane-binding F2 domains, compromising integrin activation, adhesion and cell migration. Whilst this remains a variant of uncertain significance, it is probable that the dysregulation of adhesion dynamics we observe in cells contributes to the multifaceted clinical symptoms of the patient and may provide insight into the multitude of cellular processes dependent on talin-mediated adhesion dynamics.
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Affiliation(s)
| | | | | | - Vasyl V Mykuliak
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Sanna Korpela
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Teemu O Ihalainen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Joseph Church
- To whom correspondence should be addressed. (Benjamin T. Goult), (Vesa P. Hytönen), (Joe Church)
| | - Vesa P Hytönen
- To whom correspondence should be addressed. (Benjamin T. Goult), (Vesa P. Hytönen), (Joe Church)
| | - Benjamin T Goult
- To whom correspondence should be addressed. (Benjamin T. Goult), (Vesa P. Hytönen), (Joe Church)
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6
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Integrin Regulators in Neutrophils. Cells 2022; 11:cells11132025. [PMID: 35805108 PMCID: PMC9266208 DOI: 10.3390/cells11132025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 02/01/2023] Open
Abstract
Neutrophils are the most abundant leukocytes in humans and are critical for innate immunity and inflammation. Integrins are critical for neutrophil functions, especially for their recruitment to sites of inflammation or infections. Integrin conformational changes during activation have been heavily investigated but are still not fully understood. Many regulators, such as talin, Rap1-interacting adaptor molecule (RIAM), Rap1, and kindlin, are critical for integrin activation and might be potential targets for integrin-regulating drugs in treating inflammatory diseases. In this review, we outline integrin activation regulators in neutrophils with a focus on the above critical regulators, as well as newly discovered modulators that are involved in integrin activation.
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7
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Sun H, Lagarrigue F, Ginsberg MH. The Connection Between Rap1 and Talin1 in the Activation of Integrins in Blood Cells. Front Cell Dev Biol 2022; 10:908622. [PMID: 35721481 PMCID: PMC9198492 DOI: 10.3389/fcell.2022.908622] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 04/25/2022] [Indexed: 01/13/2023] Open
Abstract
Integrins regulate the adhesion and migration of blood cells to ensure the proper positioning of these cells in the environment. Integrins detect physical and chemical stimuli in the extracellular matrix and regulate signaling pathways in blood cells that mediate their functions. Integrins are usually in a resting state in blood cells until agonist stimulation results in a high-affinity conformation ("integrin activation"), which is central to integrins' contribution to blood cells' trafficking and functions. In this review, we summarize the mechanisms of integrin activation in blood cells with a focus on recent advances understanding of mechanisms whereby Rap1 regulates talin1-integrin interaction to trigger integrin activation in lymphocytes, platelets, and neutrophils.
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Affiliation(s)
- Hao Sun
- Department of Medicine, University of California San Diego, San Diego, CA, United States
| | - Frederic Lagarrigue
- Institut de Pharmacologie et Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, Toulouse, France
| | - Mark H. Ginsberg
- Department of Medicine, University of California San Diego, San Diego, CA, United States
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8
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LFA1 Activation: Insights from a Single-Molecule Approach. Cells 2022; 11:cells11111751. [PMID: 35681446 PMCID: PMC9179313 DOI: 10.3390/cells11111751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 02/04/2023] Open
Abstract
Integrin LFA1 is a cell adhesion receptor expressed exclusively in leukocytes, and plays crucial roles in lymphocyte trafficking, antigen recognition, and effector functions. Since the discovery that the adhesiveness of LFA1 can be dynamically changed upon stimulation, one challenge has been understanding how integrins are regulated by inside-out signaling coupled with macromolecular conformational changes, as well as ligand bindings that transduce signals from the extracellular domain to the cytoplasm in outside-in signaling. The small GTPase Rap1 and integrin adaptor proteins talin1 and kindlin-3 have been recognized as critical molecules for integrin activation. However, their cooperative regulation of integrin adhesiveness in lymphocytes requires further research. Recent advances in single-molecule imaging techniques have revealed dynamic molecular processes in real-time and provided insight into integrin activation in cellular environments. This review summarizes integrin regulation and discusses new findings regarding the bidirectionality of LFA1 activation and signaling processes in lymphocytes.
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9
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Zhao Y, Lykov N, Tzeng C. Talin‑1 interaction network in cellular mechanotransduction (Review). Int J Mol Med 2022; 49:60. [PMID: 35266014 PMCID: PMC8930095 DOI: 10.3892/ijmm.2022.5116] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 02/23/2022] [Indexed: 11/16/2022] Open
Abstract
The mechanical signals within the extracellular matrix (ECM) regulate cell growth, proliferation and differentiation, and integrins function as the hub between the ECM and cellular actin. Focal adhesions (FAs) are multi‑protein, integrin‑containing complexes, acting as tension‑sensing anchoring points that bond cells to the extracellular microenvironment. Talin‑1 serves as the central protein of FAs that participates in the activation of integrins and connects them with the actin cytoskeleton. As a cytoplasmic protein, Talin‑1 consists of a globular head domain and a long rod comprised of a series of α‑helical bundles. The unique structure of the Talin‑1 rod domain permits folding and unfolding in response to the mechanical stress, revealing various binding sites. Thus, conformation changes of the Talin‑1 rod domain enable the cell to convert mechanical signals into chemical through multiple signaling pathways. The present review discusses the binding partners of Talin‑1, their interactions, effects on the cellular processes, and their possible roles in diseases.
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Affiliation(s)
- Ye Zhao
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, Jiangsu 211800, P.R. China
| | - Nikita Lykov
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, Jiangsu 211800, P.R. China
| | - Chimeng Tzeng
- Translational Medicine Research Center-Key Laboratory for Cancer T-Cell Theragnostic and Clinical Translation, School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian 361005, P.R. China
- Xiamen Chang Gung Hospital Medical Research Center, Xiamen, Fujian 361005, P.R. China
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10
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Lagarrigue F, Tan B, Du Q, Fan Z, Lopez-Ramirez MA, Gingras AR, Wang H, Qi W, Sun H. Direct Binding of Rap1 to Talin1 and to MRL Proteins Promotes Integrin Activation in CD4 + T Cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2022; 208:1378-1388. [PMID: 35197328 PMCID: PMC9644409 DOI: 10.4049/jimmunol.2100843] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 12/27/2021] [Indexed: 12/26/2022]
Abstract
Agonist-induced Rap1 GTP loading results in integrin activation involved in T cell trafficking and functions. MRL proteins Rap1-interacting adapter molecule (RIAM) and lamellipodin (LPD) are Rap1 effectors that can recruit talin1 to integrins, resulting in integrin activation. Recent work also implicates direct Rap1-talin1 interaction in integrin activation. Here, we analyze in mice the connections between Rap1 and talin1 that support integrin activation in conventional CD4+ T (Tconv) and CD25HiFoxp3+CD4+ regulatory T (Treg) cells. Talin1(R35E, R118E) mutation that disrupts both Rap1 binding sites results in a partial defect in αLβ2, α4β1, and α4β7 integrin activation in both Tconv and Treg cells with resulting defects in T cell homing. Talin1(R35E,R118E) Tconv manifested reduced capacity to induce colitis in an adoptive transfer mouse model. Loss of RIAM exacerbates the defects in Treg cell function caused by the talin1(R35E,R118E) mutation, and deleting both MRL proteins in combination with talin1(R35E,R118E) phenocopy the complete lack of integrin activation observed in Rap1a/b-null Treg cells. In sum, these data reveal the functionally significant connections between Rap1 and talin1 that enable αLβ2, α4β1, and α4β7 integrin activation in CD4+ T cells.
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Affiliation(s)
- Frederic Lagarrigue
- Institut de Pharmacologie et Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, Toulouse, France
| | - Boyang Tan
- Department of Medicine, University of California, San Diego, La Jolla, CA; and
| | - Qinyi Du
- Department of Medicine, University of California, San Diego, La Jolla, CA; and
| | - Zhichao Fan
- Department of Immunology, School of Medicine, University of Connecticut, UConn Health, Farmington, CT
| | | | - Alexandre R Gingras
- Department of Medicine, University of California, San Diego, La Jolla, CA; and
| | - Hsin Wang
- Department of Medicine, University of California, San Diego, La Jolla, CA; and
| | - Weiwei Qi
- Department of Medicine, University of California, San Diego, La Jolla, CA; and
| | - Hao Sun
- Department of Medicine, University of California, San Diego, La Jolla, CA; and
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11
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Bromberger T, Klapproth S, Rohwedder I, Weber J, Pick R, Mittmann L, Min-Weißenhorn SJ, Reichel CA, Scheiermann C, Sperandio M, Moser M. Binding of Rap1 and Riam to Talin1 Fine-Tune β2 Integrin Activity During Leukocyte Trafficking. Front Immunol 2021; 12:702345. [PMID: 34489950 PMCID: PMC8417109 DOI: 10.3389/fimmu.2021.702345] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 08/04/2021] [Indexed: 01/13/2023] Open
Abstract
β2 integrins mediate key processes during leukocyte trafficking. Upon leukocyte activation, the structurally bent β2 integrins change their conformation towards an extended, intermediate and eventually high affinity conformation, which mediate slow leukocyte rolling and firm arrest, respectively. Translocation of talin1 to integrin adhesion sites by interactions with the small GTPase Rap1 and the Rap1 effector Riam precede these processes. Using Rap1 binding mutant talin1 and Riam deficient mice we show a strong Riam-dependent T cell homing process to lymph nodes in adoptive transfer experiments and by intravital microscopy. Moreover, neutrophils from compound mutant mice exhibit strongly increased rolling velocities to inflamed cremaster muscle venules compared to single mutants. Using Hoxb8 cell derived neutrophils generated from the mutant mouse strains, we show that both pathways regulate leukocyte rolling and adhesion synergistically by inducing conformational changes of the β2 integrin ectodomain. Importantly, a simultaneous loss of both pathways results in a rolling phenotype similar to talin1 deficient neutrophils suggesting that β2 integrin regulation primarily occurs via these two pathways.
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Affiliation(s)
- Thomas Bromberger
- Center for Translational Cancer Research (TranslaTUM), TUM School of Medicine, Technische Universität München, Munich, Germany
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Sarah Klapproth
- Center for Translational Cancer Research (TranslaTUM), TUM School of Medicine, Technische Universität München, Munich, Germany
| | - Ina Rohwedder
- Walter Brendel Center of Experimental Medicine (WBex), Biomedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Jasmin Weber
- Walter Brendel Center of Experimental Medicine (WBex), Biomedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Robert Pick
- Department of Pathology and Immunology, School of Medicine, University of Geneva, Geneva, Switzerland
| | - Laura Mittmann
- Walter Brendel Centre of Experimental Medicine (WBex), Klinikum der Universität München, Ludwig-Maximilians-Universität München, Munich, Germany
- Department of Otorhinolaryngology, Ludwig-Maximilians-Universität München, Munich, Germany
| | | | - Christoph A. Reichel
- Walter Brendel Centre of Experimental Medicine (WBex), Klinikum der Universität München, Ludwig-Maximilians-Universität München, Munich, Germany
- Department of Otorhinolaryngology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Christoph Scheiermann
- Walter Brendel Center of Experimental Medicine (WBex), Biomedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
- Department of Pathology and Immunology, School of Medicine, University of Geneva, Geneva, Switzerland
| | - Markus Sperandio
- Walter Brendel Center of Experimental Medicine (WBex), Biomedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Markus Moser
- Center for Translational Cancer Research (TranslaTUM), TUM School of Medicine, Technische Universität München, Munich, Germany
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
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12
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Kondo N, Ueda Y, Kinashi T. Kindlin-3 disrupts an intersubunit association in the integrin LFA1 to trigger positive feedback activation by Rap1 and talin1. Sci Signal 2021; 14:14/686/eabf2184. [PMID: 34103420 DOI: 10.1126/scisignal.abf2184] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Integrin activation by the intracellular adaptor proteins talin1 and kindlin-3 is essential for lymphocyte adhesion. These adaptors cooperatively control integrin activation through bidirectional (inside-out and outside-in) activation signals. Using single-molecule measurements, we revealed the distinct dynamics of talin1 and kindlin-3 interactions with the integrin LFA1 (αLβ2) and their functions in LFA1 activation and LFA1-mediated adhesion. The kinetics of talin1 binding to the tail of the β2 subunit corresponded to those of LFA1 binding to its ligand ICAM1. ICAM1 binding induced transient interactions between the membrane-proximal cytoplasmic region of the β2 subunit with an N-terminal domain of kindlin-3, leading to disruption of the association between the integrin subunits (the α/β clasp) and unbending of the ectodomains of the α/β heterodimer. These conformational changes promoted high-affinity talin1 binding to the β2 tail that required the talin rod domain and the actomyosin cytoskeleton. Inside-out signaling induced by the GTPase Rap1 did not markedly stabilize the binding of talin1 and kindlin-3 to LFA1. In contrast, ligand-induced outside-in signaling, the stabilization of open LFA1 conformers, or shear force substantially altered the dynamics of talin1 and kindlin-3 association with LFA1 and enhanced both Rap1 and LFA1 activation. In migrating lymphocytes, asymmetrical distribution of talin1 and kindlin-3 correlated with the maturation of LFA1 from a low-affinity conformation at the leading edge to a high-affinity conformation in the adherent mid-body. Our results suggest that kindlin-3 spatiotemporally mediates a positive feedback circuit of LFA1 activation to control dynamic adhesion and migration of lymphocytes.
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Affiliation(s)
- Naoyuki Kondo
- Department of Molecule Genetics, Institute of Biomedical Science, Kansai Medical University, Hirakata, Osaka, 573-1010, Japan
| | - Yoshihiro Ueda
- Department of Molecule Genetics, Institute of Biomedical Science, Kansai Medical University, Hirakata, Osaka, 573-1010, Japan
| | - Tatsuo Kinashi
- Department of Molecule Genetics, Institute of Biomedical Science, Kansai Medical University, Hirakata, Osaka, 573-1010, Japan.
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13
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Bu W, Levitskaya Z, Tan SM, Gao YG. Emerging evidence for kindlin oligomerization and its role in regulating kindlin function. J Cell Sci 2021; 134:256567. [PMID: 33912917 DOI: 10.1242/jcs.256115] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrin-mediated cell-extracellular matrix (ECM) interactions play crucial roles in a broad range of physiological and pathological processes. Kindlins are important positive regulators of integrin activation. The FERM-domain-containing kindlin family comprises three members, kindlin-1, kindlin-2 and kindlin-3 (also known as FERMT1, FERMT2 and FERMT3), which share high sequence similarity (identity >50%), as well as domain organization, but exhibit diverse tissue-specific expression patterns and cellular functions. Given the significance of kindlins, analysis of their atomic structures has been an attractive field for decades. Recently, the structures of kindlin and its β-integrin-bound form have been obtained, which greatly advance our understanding of the molecular functions that involve kindlins. In particular, emerging evidence indicates that oligomerization of kindlins might affect their integrin binding and focal adhesion localization, positively or negatively. In this Review, we presented an update on the recent progress of obtaining kindlin structures, and discuss the implication for integrin activation based on kindlin oligomerization, as well as the possible regulation of this process.
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Affiliation(s)
- Wenting Bu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore637551.,Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China518055
| | - Zarina Levitskaya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore637551
| | - Suet-Mien Tan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore637551
| | - Yong-Gui Gao
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore637551.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore639798
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14
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Sun H, Zhi K, Hu L, Fan Z. The Activation and Regulation of β2 Integrins in Phagocytes and Phagocytosis. Front Immunol 2021; 12:633639. [PMID: 33868253 PMCID: PMC8044391 DOI: 10.3389/fimmu.2021.633639] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 03/11/2021] [Indexed: 01/10/2023] Open
Abstract
Phagocytes, which include neutrophils, monocytes, macrophages, and dendritic cells, protect the body by removing foreign particles, bacteria, and dead or dying cells. Phagocytic integrins are greatly involved in the recognition of and adhesion to specific antigens on cells and pathogens during phagocytosis as well as the recruitment of immune cells. β2 integrins, including αLβ2, αMβ2, αXβ2, and αDβ2, are the major integrins presented on the phagocyte surface. The activation of β2 integrins is essential to the recruitment and phagocytic function of these phagocytes and is critical for the regulation of inflammation and immune defense. However, aberrant activation of β2 integrins aggravates auto-immune diseases, such as psoriasis, arthritis, and multiple sclerosis, and facilitates tumor metastasis, making them double-edged swords as candidates for therapeutic intervention. Therefore, precise regulation of phagocyte activities by targeting β2 integrins should promote their host defense functions with minimal side effects on other cells. Here, we reviewed advances in the regulatory mechanisms underlying β2 integrin inside-out signaling, as well as the roles of β2 integrin activation in phagocyte functions.
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Affiliation(s)
- Hao Sun
- Department of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Kangkang Zhi
- Department of Vascular Surgery, Changzheng Hospital, Shanghai, China
| | - Liang Hu
- Department of Cardiology, Cardiovascular Institute of Zhengzhou University, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Zhichao Fan
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, United States
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15
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Liao Z, Gingras AR, Lagarrigue F, Ginsberg MH, Shattil SJ. Optogenetics-based localization of talin to the plasma membrane promotes activation of β3 integrins. J Biol Chem 2021; 296:100675. [PMID: 33865854 PMCID: PMC8131925 DOI: 10.1016/j.jbc.2021.100675] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/01/2021] [Accepted: 04/14/2021] [Indexed: 11/30/2022] Open
Abstract
Interaction of talin with the cytoplasmic tails of integrin β triggers integrin activation, leading to an increase of integrin affinity/avidity for extracellular ligands. In talin KO mice, loss of talin interaction with platelet integrin αIIbβ3 causes a severe hemostatic defect, and loss of talin interaction with endothelial cell integrin αVβ3 affects angiogenesis. In normal cells, talin is autoinhibited and localized in the cytoplasm. Here, we used an optogenetic platform to assess whether recruitment of full-length talin to the plasma membrane was sufficient to induce integrin activation. A dimerization module (Arabidopsis cryptochrome 2 fused to the N terminus of talin; N-terminal of cryptochrome-interacting basic helix-loop-helix domain ended with a CAAX box protein [C: cysteine; A: aliphatic amino acid; X: any C-terminal amino acid]) responsive to 450 nm (blue) light was inserted into Chinese hamster ovary cells and endothelial cells also expressing αIIbβ3 or αVβ3, respectively. Thus, exposure of the cells to blue light caused a rapid and reversible recruitment of Arabidopsis cryptochrome 2-talin to the N-terminal of cryptochrome-interacting basic helix-loop-helix domain ended with a CAAX box protein [C: cysteine; A: aliphatic amino acid; X: any C-terminal amino acid]-decorated plasma membrane. This resulted in β3 integrin activation in both cell types, as well as increasing migration of the endothelial cells. However, membrane recruitment of talin was not sufficient for integrin activation, as membrane-associated Ras-related protein 1 (Rap1)-GTP was also required. Moreover, talin mutations that interfered with its direct binding to Rap1 abrogated β3 integrin activation. Altogether, these results define a role for the plasma membrane recruitment of talin in β3 integrin activation, and they suggest a nuanced sequence of events thereafter involving Rap1-GTP.
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Affiliation(s)
- Zhongji Liao
- Department of Medicine, University of California, San Diego, La Jolla, California, USA.
| | - Alexandre R Gingras
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Frederic Lagarrigue
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Mark H Ginsberg
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Sanford J Shattil
- Department of Medicine, University of California, San Diego, La Jolla, California, USA.
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16
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Kukkurainen S, Azizi L, Zhang P, Jacquier MC, Baikoghli M, von Essen M, Tuukkanen A, Laitaoja M, Liu X, Rahikainen R, Orłowski A, Jänis J, Määttä JAE, Varjosalo M, Vattulainen I, Róg T, Svergun D, Cheng RH, Wu J, Hytönen VP, Wehrle-Haller B. The F1 loop of the talin head domain acts as a gatekeeper in integrin activation and clustering. J Cell Sci 2020; 133:jcs239202. [PMID: 33046605 PMCID: PMC10679385 DOI: 10.1242/jcs.239202] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 07/31/2020] [Indexed: 12/15/2022] Open
Abstract
Integrin activation and clustering by talin are early steps of cell adhesion. Membrane-bound talin head domain and kindlin bind to the β integrin cytoplasmic tail, cooperating to activate the heterodimeric integrin, and the talin head domain induces integrin clustering in the presence of Mn2+ Here we show that kindlin-1 can replace Mn2+ to mediate β3 integrin clustering induced by the talin head, but not that induced by the F2-F3 fragment of talin. Integrin clustering mediated by kindlin-1 and the talin head was lost upon deletion of the flexible loop within the talin head F1 subdomain. Further mutagenesis identified hydrophobic and acidic motifs in the F1 loop responsible for β3 integrin clustering. Modeling, computational and cysteine crosslinking studies showed direct and catalytic interactions of the acidic F1 loop motif with the juxtamembrane domains of α- and β3-integrins, in order to activate the β3 integrin heterodimer, further detailing the mechanism by which the talin-kindlin complex activates and clusters integrins. Moreover, the F1 loop interaction with the β3 integrin tail required the newly identified compact FERM fold of the talin head, which positions the F1 loop next to the inner membrane clasp of the talin-bound integrin heterodimer.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Sampo Kukkurainen
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, FI-33520 Tampere, Finland
- Fimlab Laboratories, Biokatu 4, FI-33520 Tampere, Finland
| | - Latifeh Azizi
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, FI-33520 Tampere, Finland
- Fimlab Laboratories, Biokatu 4, FI-33520 Tampere, Finland
| | - Pingfeng Zhang
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Marie-Claude Jacquier
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Rue Michel-Servet 1, 1211 Geneva 4, Switzerland
| | - Mo Baikoghli
- Department of Molecular and Cellular Biology, University of California, 1 Shields Ave, Davis, CA 95616, USA
| | - Magdaléna von Essen
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, FI-33520 Tampere, Finland
- Fimlab Laboratories, Biokatu 4, FI-33520 Tampere, Finland
| | - Anne Tuukkanen
- EMBL Hamburg c/o DESY, European Molecular Biology Laboratory, Notkestrasse 85, 22607 Hamburg, Germany
- European Bioinformatics Institute (EMBL-EBI), European Molecular Biology Laboratory, Wellcome Genome Campus, Hinxton, Cambridgeshire CB10 1SD, UK
| | - Mikko Laitaoja
- Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Xiaonan Liu
- Proteomics Unit, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| | - Rolle Rahikainen
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, FI-33520 Tampere, Finland
- Fimlab Laboratories, Biokatu 4, FI-33520 Tampere, Finland
| | - Adam Orłowski
- Proteomics Unit, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| | - Janne Jänis
- Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Juha A E Määttä
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, FI-33520 Tampere, Finland
- Fimlab Laboratories, Biokatu 4, FI-33520 Tampere, Finland
| | - Markku Varjosalo
- Proteomics Unit, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| | - Ilpo Vattulainen
- Computational Physics Laboratory, Tampere University, FI-33520 Tampere, Finland
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
| | - Tomasz Róg
- Computational Physics Laboratory, Tampere University, FI-33520 Tampere, Finland
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
| | - Dmitri Svergun
- EMBL Hamburg c/o DESY, European Molecular Biology Laboratory, Notkestrasse 85, 22607 Hamburg, Germany
| | - R Holland Cheng
- Department of Molecular and Cellular Biology, University of California, 1 Shields Ave, Davis, CA 95616, USA
| | - Jinhua Wu
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Vesa P Hytönen
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, FI-33520 Tampere, Finland
- Fimlab Laboratories, Biokatu 4, FI-33520 Tampere, Finland
| | - Bernhard Wehrle-Haller
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Rue Michel-Servet 1, 1211 Geneva 4, Switzerland
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17
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Lagarrigue F, Paul DS, Gingras AR, Valadez AJ, Sun H, Lin J, Cuevas MN, Ablack JN, Lopez-Ramirez MA, Bergmeier W, Ginsberg MH. Talin-1 is the principal platelet Rap1 effector of integrin activation. Blood 2020; 136:1180-1190. [PMID: 32518959 PMCID: PMC7472713 DOI: 10.1182/blood.2020005348] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 04/29/2020] [Indexed: 12/14/2022] Open
Abstract
Ras-related protein 1 (Rap1) is a major convergence point of the platelet-signaling pathways that result in talin-1 binding to the integrin β cytoplasmic domain and consequent integrin activation, platelet aggregation, and effective hemostasis. The nature of the connection between Rap1 and talin-1 in integrin activation is an important remaining gap in our understanding of this process. Previous work identified a low-affinity Rap1-binding site in the talin-1 F0 domain that makes a small contribution to integrin activation in platelets. We recently identified an additional Rap1-binding site in the talin-1 F1 domain that makes a greater contribution than F0 in model systems. Here we generated mice bearing point mutations, which block Rap1 binding without affecting talin-1 expression, in either the talin-1 F1 domain (R118E) alone, which were viable, or in both the F0 and F1 domains (R35E,R118E), which were embryonic lethal. Loss of the Rap1-talin-1 F1 interaction in platelets markedly decreases talin-1-mediated activation of platelet β1- and β3-integrins. Integrin activation and platelet aggregation in mice whose platelets express only talin-1(R35E, R118E) are even more impaired, resembling the defect seen in platelets lacking both Rap1a and Rap1b. Although Rap1 is important in thrombopoiesis, platelet secretion, and surface exposure of phosphatidylserine, loss of the Rap1-talin-1 interaction in talin-1(R35E, R118E) platelets had little effect on these processes. These findings show that talin-1 is the principal direct effector of Rap1 GTPases that regulates platelet integrin activation in hemostasis.
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Affiliation(s)
- Frederic Lagarrigue
- Department of Medicine, University of California, San Diego, La Jolla, CA
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Centre National de la Recherche Scientifique (CNRS), Université Paul Sabatier (UPS), Université de Toulouse, Toulouse, France
| | - David S Paul
- UNC Blood Research Center and
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC; and
| | | | - Andrew J Valadez
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Hao Sun
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Jenny Lin
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Monica N Cuevas
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Jailal N Ablack
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Miguel Alejandro Lopez-Ramirez
- Department of Medicine, University of California, San Diego, La Jolla, CA
- Department of Pharmacology, University of California, San Diego, La Jolla, CA
| | - Wolfgang Bergmeier
- UNC Blood Research Center and
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC; and
| | - Mark H Ginsberg
- Department of Medicine, University of California, San Diego, La Jolla, CA
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18
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Kadry YA, Calderwood DA. Chapter 22: Structural and signaling functions of integrins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183206. [PMID: 31991120 PMCID: PMC7063833 DOI: 10.1016/j.bbamem.2020.183206] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/21/2020] [Accepted: 01/22/2020] [Indexed: 02/06/2023]
Abstract
The integrin family of transmembrane adhesion receptors is essential for sensing and adhering to the extracellular environment. Integrins are heterodimers composed of non-covalently associated α and β subunits that engage extracellular matrix proteins and couple to intracellular signaling and cytoskeletal complexes. Humans have 24 different integrin heterodimers with differing ligand binding specificities and non-redundant functions. Complex structural rearrangements control the ability of integrins to engage ligands and to activate diverse downstream signaling networks, modulating cell adhesion and dynamics, processes which are crucial for metazoan life and development. Here we review the structural and signaling functions of integrins focusing on recent advances which have enhanced our understanding of how integrins are activated and regulated, and the cytoplasmic signaling networks downstream of integrins.
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Affiliation(s)
- Yasmin A Kadry
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, United States of America
| | - David A Calderwood
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, United States of America; Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, United States of America..
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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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Sarker M, Goliaei A, Golesi F, Poggi M, Cook A, Khan MAI, Temple BR, Stefanini L, Canault M, Bergmeier W, Campbell SL. Subcellular localization of Rap1 GTPase activator CalDAG-GEFI is orchestrated by interaction of its atypical C1 domain with membrane phosphoinositides. J Thromb Haemost 2020; 18:693-705. [PMID: 31758832 PMCID: PMC7050387 DOI: 10.1111/jth.14687] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 10/17/2019] [Accepted: 11/14/2019] [Indexed: 12/21/2022]
Abstract
BACKGROUND The small GTPase Rap1 and its guanine nucleotide exchange factor, CalDAG-GEFI (CDGI), are critical for platelet function and hemostatic plug formation. CDGI function is regulated by a calcium binding EF hand regulatory domain and an atypical C1 domain with unknown function. OBJECTIVE Here, we investigated whether the C1 domain controls CDGI subcellular localization, both in vitro and in vivo. METHODS CDGI interaction with phosphoinositides was studied by lipid co-sedimentation assays and molecular dynamics simulations. Cellular localization of CDGI was studied in heterologous cells by immunofluorescence and subcellular fractionation assays. RESULTS Lipid co-sedimentation studies demonstrated that the CDGI C1 domain associates with membranes through exclusive recognition of phosphoinositides, phosphatidylinositol (4,5)-biphosphate (PIP2) and phosphatidylinositol (3,4,5)-triphosphate (PIP3). Molecular dynamics simulations identified a phospholipid recognition motif consisting of residues exclusive to the CDGI C1 domain. Mutation of those residues abolished co-sedimentation of the C1 domain with lipid vesicles and impaired membrane localization of CDGI in heterologous cells. CONCLUSION Our studies identify a novel interaction between an atypical C1 domain and phosphatidylinositol (4,5)-biphosphate and phosphatidylinositol (3,4,5)-triphosphate in cellular membranes, which is critical for Rap1 signaling in health and disease.
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Affiliation(s)
- Muzaddid Sarker
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ardeshir Goliaei
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | | | - Marjorie Poggi
- Aix Marseille University, INSERM, INRA, Marseille, France
| | - Aaron Cook
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Mohammad A. I. Khan
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Brenda R. Temple
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- RL Juliano Structural Bioinformatics Core, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Lucia Stefanini
- Department of Internal Medicine and Medical Specialties, Sapienza University of Rome, Rome, Italy
| | | | - Wolfgang Bergmeier
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Sharon L. Campbell
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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21
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Activation and suppression of hematopoietic integrins in hemostasis and immunity. Blood 2020; 135:7-16. [DOI: 10.1182/blood.2019003336] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 10/31/2019] [Indexed: 12/15/2022] Open
Abstract
Nolte and Margadant review the current understanding of the activation and inactivation of integrin receptors expressed by hematopoietic cells and the role of these conformational changes in modulating platelet and leukocyte function.
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22
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Bromberger T, Zhu L, Klapproth S, Qin J, Moser M. Rap1 and membrane lipids cooperatively recruit talin to trigger integrin activation. J Cell Sci 2019; 132:jcs235531. [PMID: 31578239 PMCID: PMC6857594 DOI: 10.1242/jcs.235531] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 09/24/2019] [Indexed: 12/15/2022] Open
Abstract
Recruitment and tethering of talin to the plasma membrane initiate the process of integrin activation. Multiple factors including the Rap1 proteins, RIAM (also known as APBB1IP) and PIP2 bind talin proteins and have been proposed to regulate these processes, but not systematically analyzed. By expressing specific talin mutants into talin-null fibroblasts, we show that binding of the talin F0 domain to Rap1 synergizes with membrane lipid binding of the talin F2 domain during talin membrane targeting and integrin activation, whereas the interaction of the talin rod with RIAM was dispensable. We also characterized a second Rap1-binding site within the talin F1 domain by detailed NMR analysis. Interestingly, while talin F1 exhibited significantly weaker Rap1-binding affinity than talin F0, expression of a talin F1 Rap1-binding mutant inhibited cell adhesion, spreading, talin recruitment and integrin activation similarly to the talin F0 Rap1-binding mutant. Moreover, the defects became significantly stronger when both Rap1-binding sites were mutated. In conclusion, our data suggest a model in which cooperative binding of Rap1 to the talin F0 and F1 domains synergizes with membrane PIP2 binding to spatiotemporally position and activate talins to regulate integrin activity.
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Affiliation(s)
- Thomas Bromberger
- Max-Planck-Institute of Biochemistry, Department of Molecular Medicine, 82152 Martinsried, Germany
| | - Liang Zhu
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA
| | - Sarah Klapproth
- Max-Planck-Institute of Biochemistry, Department of Molecular Medicine, 82152 Martinsried, Germany
| | - Jun Qin
- Department of Cardiovascular & Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA
| | - Markus Moser
- Max-Planck-Institute of Biochemistry, Department of Molecular Medicine, 82152 Martinsried, Germany
- Center for Translational Cancer Research (TranslaTUM), TUM School of Medicine, Technische Universität München, 81675 Munich, Germany
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23
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Gingras AR, Lagarrigue F, Cuevas MN, Valadez AJ, Zorovich M, McLaughlin W, Lopez-Ramirez MA, Seban N, Ley K, Kiosses WB, Ginsberg MH. Rap1 binding and a lipid-dependent helix in talin F1 domain promote integrin activation in tandem. J Cell Biol 2019; 218:1799-1809. [PMID: 30988001 PMCID: PMC6548133 DOI: 10.1083/jcb.201810061] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 02/11/2019] [Accepted: 03/28/2019] [Indexed: 02/07/2023] Open
Abstract
Rap1 GTPases bind effectors, such as RIAM, to enable talin1 to induce integrin activation. In addition, Rap1 binds directly to the talin1 F0 domain (F0); however, this interaction makes a limited contribution to integrin activation in CHO cells or platelets. Here, we show that talin1 F1 domain (F1) contains a previously undetected Rap1-binding site of similar affinity to that in F0. A structure-guided point mutant (R118E) in F1, which blocks Rap1 binding, abolishes the capacity of Rap1 to potentiate talin1-induced integrin activation. The capacity of F1 to mediate Rap1-dependent integrin activation depends on a unique loop in F1 that has a propensity to form a helix upon binding to membrane lipids. Basic membrane-facing residues of this helix are critical, as charge-reversal mutations led to dramatic suppression of talin1-dependent activation. Thus, a novel Rap1-binding site and a transient lipid-dependent helix in F1 work in tandem to enable a direct Rap1-talin1 interaction to cause integrin activation.
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Affiliation(s)
| | | | - Monica N Cuevas
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Andrew J Valadez
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Marcus Zorovich
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Wilma McLaughlin
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | | | - Nicolas Seban
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Klaus Ley
- Division of Inflammation Biology, La Jolla Institute for Immunology, La Jolla, CA
- Department of Bioengineering, University of California, San Diego, La Jolla, CA
| | - William B Kiosses
- Microscopy Core Facility, La Jolla Institute for Immunology, La Jolla, CA
| | - Mark H Ginsberg
- Department of Medicine, University of California, San Diego, La Jolla, CA
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Huang J, Li X, Shi X, Zhu M, Wang J, Huang S, Huang X, Wang H, Li L, Deng H, Zhou Y, Mao J, Long Z, Ma Z, Ye W, Pan J, Xi X, Jin J. Platelet integrin αIIbβ3: signal transduction, regulation, and its therapeutic targeting. J Hematol Oncol 2019; 12:26. [PMID: 30845955 PMCID: PMC6407232 DOI: 10.1186/s13045-019-0709-6] [Citation(s) in RCA: 198] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 02/21/2019] [Indexed: 12/18/2022] Open
Abstract
Integrins are a family of transmembrane glycoprotein signaling receptors that can transmit bioinformation bidirectionally across the plasma membrane. Integrin αIIbβ3 is expressed at a high level in platelets and their progenitors, where it plays a central role in platelet functions, hemostasis, and arterial thrombosis. Integrin αIIbβ3 also participates in cancer progression, such as tumor cell proliferation and metastasis. In resting platelets, integrin αIIbβ3 adopts an inactive conformation. Upon agonist stimulation, the transduction of inside-out signals leads integrin αIIbβ3 to switch from a low- to high-affinity state for fibrinogen and other ligands. Ligand binding causes integrin clustering and subsequently promotes outside-in signaling, which initiates and amplifies a range of cellular events to drive essential platelet functions such as spreading, aggregation, clot retraction, and thrombus consolidation. Regulation of the bidirectional signaling of integrin αIIbβ3 requires the involvement of numerous interacting proteins, which associate with the cytoplasmic tails of αIIbβ3 in particular. Integrin αIIbβ3 and its signaling pathways are considered promising targets for antithrombotic therapy. This review describes the bidirectional signal transduction of integrin αIIbβ3 in platelets, as well as the proteins responsible for its regulation and therapeutic agents that target integrin αIIbβ3 and its signaling pathways.
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Affiliation(s)
- Jiansong Huang
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xia Li
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xiaofeng Shi
- Department of Hematology, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu, China
| | - Mark Zhu
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Jinghan Wang
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Shujuan Huang
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xin Huang
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Huafeng Wang
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Department of Hematological Malignancies Translational Science, Gehr Family Center for Leukemia Research, Hematologic Malignancies and Stem Cell Transplantation Institute, Beckman Research Institute, City of Hope Medical Center, Duarte, CA, 91010, USA
| | - Ling Li
- Department of Hematological Malignancies Translational Science, Gehr Family Center for Leukemia Research, Hematologic Malignancies and Stem Cell Transplantation Institute, Beckman Research Institute, City of Hope Medical Center, Duarte, CA, 91010, USA
| | - Huan Deng
- Department of Pathology, The Fourth Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Yulan Zhou
- Department of Hematology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Jianhua Mao
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Collaborative Innovation Center of Hematology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Sino-French Research Centre for Life Sciences and Genomics, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhangbiao Long
- Department of Hematology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Zhixin Ma
- Clinical Prenatal Diagnosis Center, Women's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Wenle Ye
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Jiajia Pan
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China.,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xiaodong Xi
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Collaborative Innovation Center of Hematology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China. .,Sino-French Research Centre for Life Sciences and Genomics, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Jie Jin
- Department of Hematology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China. .,Key Laboratory of Hematologic Malignancies, Diagnosis and Treatment, Hangzhou, Zhejiang, China. .,Institute of Hematology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
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Bromberger T, Klapproth S, Rohwedder I, Zhu L, Mittmann L, Reichel CA, Sperandio M, Qin J, Moser M. Direct Rap1/Talin1 interaction regulates platelet and neutrophil integrin activity in mice. Blood 2018; 132:2754-2762. [PMID: 30442677 PMCID: PMC6307989 DOI: 10.1182/blood-2018-04-846766] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 11/08/2018] [Indexed: 12/27/2022] Open
Abstract
Targeting Talin1 to the plasma membrane is a crucial step in integrin activation, which in leukocytes is mediated by a Rap1/RIAM/Talin1 pathway, whereas in platelets, it is RIAM independent. Recent structural, biochemical, and cell biological studies have suggested direct Rap1/Talin1 interaction as an alternative mechanism to recruit Talin1 to the membrane and induce integrin activation. To test whether this pathway is of relevance in vivo, we generated Rap1 binding-deficient Talin1 knockin (Tln13mut) mice. Although Tln13mut mice showed no obvious abnormalities, their platelets exhibited reduced integrin activation, aggregation, adhesion, and spreading, resulting in prolonged tail-bleeding times and delayed thrombus formation and vessel occlusion in vivo. Surprisingly, neutrophil adhesion to different integrin ligands and β2 integrin-dependent phagocytosis were also significantly impaired, which caused profound leukocyte adhesion and extravasation defects in Tln13mut mice. In contrast, macrophages exhibited no defect in adhesion or spreading despite reduced integrin activation. Taken together, our findings suggest that direct Rap1/Talin1 interaction is of particular importance in regulating the activity of different integrin classes expressed on platelets and neutrophils, which both depend on fast and dynamic integrin-mediated responses.
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Affiliation(s)
- Thomas Bromberger
- Department Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Sarah Klapproth
- Department Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Ina Rohwedder
- Walter Brendel Centre of Experimental Medicine, Klinikum der Universität Munich, Ludwig Maximilians University Munich, Martinsried, Germany
| | - Liang Zhu
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Laura Mittmann
- Walter Brendel Centre of Experimental Medicine, Klinikum der Universität Munich, Ludwig Maximilians University Munich, Martinsried, Germany
- Department of Otorhinolarynology, Ludwig Maximilians University Munich, Munich, Germany; and
| | - Christoph A Reichel
- Walter Brendel Centre of Experimental Medicine, Klinikum der Universität Munich, Ludwig Maximilians University Munich, Martinsried, Germany
- Department of Otorhinolarynology, Ludwig Maximilians University Munich, Munich, Germany; and
| | - Markus Sperandio
- Walter Brendel Centre of Experimental Medicine, Klinikum der Universität Munich, Ludwig Maximilians University Munich, Martinsried, Germany
- German Centre for Cardiovascular Research, Munich Heart Alliance, Munich, Germany
| | - Jun Qin
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Markus Moser
- Department Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
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Camp D, Haage A, Solianova V, Castle WM, Xu QA, Lostchuck E, Goult BT, Tanentzapf G. Direct binding of Talin to Rap1 is required for cell-ECM adhesion in Drosophila. J Cell Sci 2018; 131:jcs.225144. [PMID: 30446511 DOI: 10.1242/jcs.225144] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/08/2018] [Indexed: 12/27/2022] Open
Abstract
Attachment of cells to the extracellular matrix (ECM) via integrins is essential for animal development and tissue maintenance. The cytoplasmic protein Talin (encoded by rhea in flies) is necessary for linking integrins to the cytoskeleton, and its recruitment is a key step in the assembly of the adhesion complex. However, the mechanisms that regulate Talin recruitment to sites of adhesion in vivo are still not well understood. Here, we show that Talin recruitment to, and maintenance at, sites of integrin-mediated adhesion requires a direct interaction between Talin and the GTPase Rap1. A mutation that blocks the direct binding of Talin to Rap1 abolished Talin recruitment to sites of adhesion and the resulting phenotype phenocopies that seen with null alleles of Talin. Moreover, we show that Rap1 activity modulates Talin recruitment to sites of adhesion via its direct binding to Talin. These results identify the direct Talin-Rap1 interaction as a key in vivo mechanism for controlling integrin-mediated cell-ECM adhesion.
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Affiliation(s)
- Darius Camp
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada V6T 1Z3
| | - Amanda Haage
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada V6T 1Z3
| | - Veronika Solianova
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada V6T 1Z3
| | - William M Castle
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Qinyuan A Xu
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada V6T 1Z3
| | - Emily Lostchuck
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada V6T 1Z3
| | - Benjamin T Goult
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Guy Tanentzapf
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada V6T 1Z3
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