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  1. Article ; Online: KANK proteins.

    Guo, Shiny Shengzhen / Fässler, Reinhard

    Current biology : CB

    2022  Volume 32, Issue 19, Page(s) R990–R992

    MeSH term(s) Adaptor Proteins, Signal Transducing ; Cytoskeletal Proteins
    Chemical Substances Adaptor Proteins, Signal Transducing ; Cytoskeletal Proteins
    Language English
    Publishing date 2022-10-11
    Publishing country England
    Document type Journal Article
    ZDB-ID 1071731-6
    ISSN 1879-0445 ; 0960-9822
    ISSN (online) 1879-0445
    ISSN 0960-9822
    DOI 10.1016/j.cub.2022.08.073
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: β1 integrin-mediated mast cell immune-surveillance of blood vessel content.

    Link, Kristina / Muhandes, Lina / Polikarpova, Anastasia / Lämmermann, Tim / Sixt, Michael / Fässler, Reinhard / Roers, Axel

    The Journal of allergy and clinical immunology

    2024  

    Abstract: Background: Immunoglobulin E, IgE)-mediated degranulation of mast cells, MCs) provides rapid protection against environmental hazards, including animal venoms. A fraction of tissue-resident MCs intimately associates with blood vessels. These ... ...

    Abstract Background: Immunoglobulin E, IgE)-mediated degranulation of mast cells, MCs) provides rapid protection against environmental hazards, including animal venoms. A fraction of tissue-resident MCs intimately associates with blood vessels. These perivascular MCs were reported to extend projections into the vessel lumen and to be the first MCs to acquire intravenously injected IgE, suggesting that IgE loading of MCs depends on their vascular association.
    Objective: We sought to elucidate the molecular basis of the MC-blood vessel interaction and to determine its relevance for IgE-mediated immune responses.
    Methods: We selectively inactivated the Itgb1 gene, encoding the β1 chain of integrin adhesion molecules, ITGB1; in MCs by conditional gene targeting in mice. We analyzed skin MCs for blood vessel association, surface IgE density, capability to bind circulating antibody specific for MC surface molecules, as well as in vivo responses to antigen administered via different routes.
    Results: Lack of ITGB1 expression severely compromised MC blood vessel association. ITGB1-deficient MCs showed normal densities of surface IgE but reduced binding of intravenously injected antibodies. While their capacity to degranulate in response to IgE ligation in vivo was unimpaired, anaphylactic responses to antigen circulating in the vasculature were largely abolished.
    Conclusion: ITGB1-mediated association of MCs with blood vessels is key for MC immune-surveillance of blood vessel content, but is dispensable for slow steady-state loading of endogenous IgE onto tissue-resident MCs.
    Language English
    Publishing date 2024-04-15
    Publishing country United States
    Document type Journal Article
    ZDB-ID 121011-7
    ISSN 1097-6825 ; 1085-8725 ; 0091-6749
    ISSN (online) 1097-6825 ; 1085-8725
    ISSN 0091-6749
    DOI 10.1016/j.jaci.2024.03.022
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Talin and kindlin use integrin tail allostery and direct binding to activate integrins.

    Aretz, Jonas / Aziz, Masood / Strohmeyer, Nico / Sattler, Michael / Fässler, Reinhard

    Nature structural & molecular biology

    2023  Volume 30, Issue 12, Page(s) 1913–1924

    Abstract: Integrin affinity regulation, also termed integrin activation, is essential for metazoan life. Although talin and kindlin binding to the β-integrin cytoplasmic tail is indispensable for integrin activation, it is unknown how they achieve this function. ... ...

    Abstract Integrin affinity regulation, also termed integrin activation, is essential for metazoan life. Although talin and kindlin binding to the β-integrin cytoplasmic tail is indispensable for integrin activation, it is unknown how they achieve this function. By combining NMR, biochemistry and cell biology techniques, we found that talin and kindlin binding to the β-tail can induce a conformational change that increases talin affinity and decreases kindlin affinity toward it. We also discovered that this asymmetric affinity regulation is accompanied by a direct interaction between talin and kindlin, which promotes simultaneous binding of talin and kindlin to β-tails. Disrupting allosteric communication between the β-tail-binding sites of talin and kindlin or their direct interaction in cells severely compromised integrin functions. These data show how talin and kindlin cooperate to generate a small but critical population of ternary talin-β-integrin-kindlin complexes with high talin-integrin affinity and high dynamics.
    MeSH term(s) Animals ; Talin/chemistry ; Talin/metabolism ; Integrins/metabolism ; Binding Sites ; Protein Binding
    Chemical Substances Talin ; Integrins
    Language English
    Publishing date 2023-12-12
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2126708-X
    ISSN 1545-9985 ; 1545-9993
    ISSN (online) 1545-9985
    ISSN 1545-9993
    DOI 10.1038/s41594-023-01139-9
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  4. Article ; Online: CDK1-cyclin-B1-induced kindlin degradation drives focal adhesion disassembly at mitotic entry.

    Chen, Nan-Peng / Aretz, Jonas / Fässler, Reinhard

    Nature cell biology

    2022  Volume 24, Issue 5, Page(s) 723–736

    Abstract: The disassembly of integrin-containing focal adhesions (FAs) at mitotic entry is essential for cell rounding, mitotic retraction fibre formation, bipolar spindle positioning and chromosome segregation. The mechanism that drives FA disassembly at mitotic ... ...

    Abstract The disassembly of integrin-containing focal adhesions (FAs) at mitotic entry is essential for cell rounding, mitotic retraction fibre formation, bipolar spindle positioning and chromosome segregation. The mechanism that drives FA disassembly at mitotic entry is unknown. Here, we show that the CDK1-cyclin B1 complex phosphorylates the integrin activator kindlin, which results in the recruitment of the cullin 9-FBXL10 ubiquitin ligase complex that mediates kindlin ubiquitination and degradation. This molecular pathway is essential for FA disassembly and cell rounding, as phospho-inhibitory mutations of the CDK1 motif prevent kindlin degradation, FA disassembly and mitotic cell rounding. Conversely, phospho-mimetic mutations promote kindlin degradation in interphase, accelerate mitotic cell rounding and impair mitotic retraction fibre formation. Despite the opposing effects on kindlin stability, both types of mutations cause severe mitotic spindle defects, apoptosis and aneuploidy. Thus, the exquisite regulation of kindlin levels at mitotic entry is essential for cells to progress accurately through mitosis.
    MeSH term(s) CDC2 Protein Kinase/genetics ; CDC2 Protein Kinase/metabolism ; Cell Cycle Proteins/metabolism ; Cyclin B1/genetics ; Cyclin B1/metabolism ; Focal Adhesions/genetics ; Focal Adhesions/metabolism ; Integrins/metabolism ; Mitosis/genetics ; Phosphorylation ; Spindle Apparatus/genetics ; Spindle Apparatus/metabolism
    Chemical Substances Cell Cycle Proteins ; Cyclin B1 ; Integrins ; CDC2 Protein Kinase (EC 2.7.11.22)
    Language English
    Publishing date 2022-04-25
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1474722-4
    ISSN 1476-4679 ; 1465-7392
    ISSN (online) 1476-4679
    ISSN 1465-7392
    DOI 10.1038/s41556-022-00886-z
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  5. Article ; Online: Integrin β1 regulates marginal zone B cell differentiation and PI3K signaling.

    Andreani, Virginia / Ramamoorthy, Senthilkumar / Fässler, Reinhard / Grosschedl, Rudolf

    The Journal of experimental medicine

    2022  Volume 220, Issue 1

    Abstract: Marginal zone (MZ) B cells represent innate-like B cells that mediate a fast immune response. The adhesion of MZ B cells to the marginal sinus of the spleen is governed by integrins. Here, we address the question of whether β1-integrin has additional ... ...

    Abstract Marginal zone (MZ) B cells represent innate-like B cells that mediate a fast immune response. The adhesion of MZ B cells to the marginal sinus of the spleen is governed by integrins. Here, we address the question of whether β1-integrin has additional functions by analyzing Itgb1fl/flCD21Cre mice in which the β1-integrin gene is deleted in mature B cells. We find that integrin β1-deficient mice have a defect in the differentiation of MZ B cells and plasma cells. We show that integrin β1-deficient transitional B cells, representing the precursors of MZ B cells, have enhanced B cell receptor (BCR) signaling, altered PI3K and Ras/ERK pathways, and an enhanced interaction of integrin-linked kinase (ILK) with the adaptor protein Grb2. Moreover, the MZ B cell defect of integrin β1-deficient mice could, at least in part, be restored by a pharmacological inhibition of the PI3K pathway. Thus, β1-integrin has an unexpected function in the differentiation and function of MZ B cells.
    MeSH term(s) Mice ; Animals ; Integrin beta1/metabolism ; Phosphatidylinositol 3-Kinases/metabolism ; Signal Transduction ; Cell Differentiation ; Integrins
    Chemical Substances Integrin beta1 ; Phosphatidylinositol 3-Kinases (EC 2.7.1.-) ; Integrins
    Language English
    Publishing date 2022-11-09
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 218343-2
    ISSN 1540-9538 ; 0022-1007
    ISSN (online) 1540-9538
    ISSN 0022-1007
    DOI 10.1084/jem.20220342
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  6. Article ; Online: A FAK conundrum is solved: activation and organization of focal adhesion kinase at the plasma membrane.

    Brod, Florian / Fässler, Reinhard

    The EMBO journal

    2020  Volume 39, Issue 19, Page(s) e106234

    Abstract: Focal adhesion kinase (FAK) is a central mediator of cell adhesion, acting both as a scaffold and as catalytically active kinase. Acebrón et al (2020) use cryo-electron microscopy (cryo-EM) to visualize the dramatic structural changes that occur upon FAK ...

    Abstract Focal adhesion kinase (FAK) is a central mediator of cell adhesion, acting both as a scaffold and as catalytically active kinase. Acebrón et al (2020) use cryo-electron microscopy (cryo-EM) to visualize the dramatic structural changes that occur upon FAK recruitment to the plasma membrane, which releases FAK autoinhibition and induces its oligomerization. Since activity control via autoinhibition and protein clustering are features also utilized by other focal adhesion (FA) proteins, they have moved center stage in the endeavor to understand the complex process of cell adhesion regulation.
    MeSH term(s) Cell Adhesion ; Cell Membrane ; Cryoelectron Microscopy ; Focal Adhesion Kinase 1 ; Focal Adhesion Protein-Tyrosine Kinases ; Lipids ; Phosphorylation ; Signal Transduction
    Chemical Substances Lipids ; Focal Adhesion Kinase 1 (EC 2.7.10.2) ; Focal Adhesion Protein-Tyrosine Kinases (EC 2.7.10.2)
    Language English
    Publishing date 2020-08-31
    Publishing country England
    Document type News ; Comment
    ZDB-ID 586044-1
    ISSN 1460-2075 ; 0261-4189
    ISSN (online) 1460-2075
    ISSN 0261-4189
    DOI 10.15252/embj.2020106234
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  7. Article ; Online: In mitosis integrins reduce adhesion to extracellular matrix and strengthen adhesion to adjacent cells.

    Huber, Maximilian / Casares-Arias, Javier / Fässler, Reinhard / Müller, Daniel J / Strohmeyer, Nico

    Nature communications

    2023  Volume 14, Issue 1, Page(s) 2143

    Abstract: To enter mitosis, most adherent animal cells reduce adhesion, which is followed by cell rounding. How mitotic cells regulate adhesion to neighboring cells and extracellular matrix (ECM) proteins is poorly understood. Here we report that, similar to ... ...

    Abstract To enter mitosis, most adherent animal cells reduce adhesion, which is followed by cell rounding. How mitotic cells regulate adhesion to neighboring cells and extracellular matrix (ECM) proteins is poorly understood. Here we report that, similar to interphase, mitotic cells can employ integrins to initiate adhesion to the ECM in a kindlin- and talin-dependent manner. However, unlike interphase cells, we find that mitotic cells cannot engage newly bound integrins to actomyosin via talin or vinculin to reinforce adhesion. We show that the missing actin connection of newly bound integrins leads to transient ECM-binding and prevents cell spreading during mitosis. Furthermore, β1 integrins strengthen the adhesion of mitotic cells to adjacent cells, which is supported by vinculin, kindlin, and talin1. We conclude that this dual role of integrins in mitosis weakens the cell-ECM adhesion and strengthens the cell-cell adhesion to prevent delamination of the rounding and dividing cell.
    MeSH term(s) Animals ; Integrins/metabolism ; Vinculin/metabolism ; Talin/metabolism ; Cell Adhesion/physiology ; Extracellular Matrix/metabolism ; Mitosis
    Chemical Substances Integrins ; Vinculin (125361-02-6) ; Talin
    Language English
    Publishing date 2023-04-14
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-023-37760-x
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  8. Article ; Online: Surface-induced phase separation of reconstituted nascent integrin clusters on lipid membranes.

    Hsu, Chiao-Peng / Aretz, Jonas / Hordeichyk, Arsenii / Fässler, Reinhard / Bausch, Andreas R

    Proceedings of the National Academy of Sciences of the United States of America

    2023  Volume 120, Issue 31, Page(s) e2301881120

    Abstract: Integrin adhesion complexes are essential membrane-associated cellular compartments for metazoan life. The formation of initial integrin adhesion complexes is a dynamic process involving focal adhesion proteins assembled at the integrin cytoplasmic tails ...

    Abstract Integrin adhesion complexes are essential membrane-associated cellular compartments for metazoan life. The formation of initial integrin adhesion complexes is a dynamic process involving focal adhesion proteins assembled at the integrin cytoplasmic tails and the inner leaflet of the plasma membrane. The weak multivalent protein interactions within the complex and with the plasma membrane suggest that liquid-liquid phase separation could play a role in the nascent adhesion assembly. Here, we report that solid-supported lipid membranes supplemented with phosphoinositides induce the phase separation of minimal integrin adhesion condensates composed of integrin
    MeSH term(s) Animals ; Integrins/metabolism ; Paxillin/metabolism ; Talin/metabolism ; Cell Membrane/metabolism ; Integrin beta1/metabolism ; Phosphatidylinositols ; Cell Adhesion/physiology
    Chemical Substances Integrins ; Paxillin ; Talin ; Integrin beta1 ; Phosphatidylinositols
    Language English
    Publishing date 2023-07-26
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.2301881120
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  9. Article ; Online: Kindlin stabilizes the talin·integrin bond under mechanical load by generating an ideal bond.

    Bodescu, Mihai Adrian / Aretz, Jonas / Grison, Marco / Rief, Matthias / Fässler, Reinhard

    Proceedings of the National Academy of Sciences of the United States of America

    2023  Volume 120, Issue 26, Page(s) e2218116120

    Abstract: Integrin-mediated adhesion is essential for metazoan life. Integrin binding to ligand requires an activation step prior to binding ligand that depends on direct binding of talin and kindlin to the β-integrin cytoplasmic tail and the transmission of force ...

    Abstract Integrin-mediated adhesion is essential for metazoan life. Integrin binding to ligand requires an activation step prior to binding ligand that depends on direct binding of talin and kindlin to the β-integrin cytoplasmic tail and the transmission of force from the actomyosin via talin to the integrin-ligand bonds. However, the affinity of talin for integrin tails is low. It is therefore still unclear how such low-affinity bonds are reinforced to transmit forces up to 10 to 40 pN. In this study, we use single-molecule force spectroscopy by optical tweezers to investigate the mechanical stability of the talin•integrin bond in the presence and absence of kindlin. While talin and integrin alone form a weak and highly dynamic slip bond, the addition of kindlin-2 induces a force-independent, ideal talin•integrin bond, which relies on the steric proximity of and the intervening amino acid sequences between the talin- and kindlin-binding sites in the β-integrin tail. Our findings show how kindlin cooperates with talin to enable transmission of high forces required to stabilize cell adhesion.
    MeSH term(s) Animals ; Talin/metabolism ; Integrins ; Ligands ; Membrane Proteins/metabolism ; Cell Adhesion
    Chemical Substances Talin ; Integrins ; Ligands ; Membrane Proteins
    Language English
    Publishing date 2023-06-20
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.2218116120
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  10. Article ; Online: New insights into the phosphorylation of the threonine motif of the β1 integrin cytoplasmic domain.

    Böttcher, Ralph T / Strohmeyer, Nico / Aretz, Jonas / Fässler, Reinhard

    Life science alliance

    2022  Volume 5, Issue 4

    Abstract: Integrins require an activation step before ligand binding and signaling that is mediated by talin and kindlin binding to the β integrin cytosolic domain (β-tail). Conflicting reports exist about the contribution of phosphorylation of a conserved ... ...

    Abstract Integrins require an activation step before ligand binding and signaling that is mediated by talin and kindlin binding to the β integrin cytosolic domain (β-tail). Conflicting reports exist about the contribution of phosphorylation of a conserved threonine motif in the β1-tail (β1-pT788/pT789) to integrin activation. We show that widely used and commercially available antibodies against β1-pT788/pT789 integrin do not detect specific β1-pT788/pT789 integrin signals in immunoblots of several human and mouse cell lysates but bind bi-phosphorylated threonine residues in numerous proteins, which were identified by mass spectrometry experiments. Furthermore, we found that fibroblasts and epithelial cells expressing the phospho-mimicking β1-TT788/789DD integrin failed to activate β1 integrins and displayed reduced integrin ligand binding, adhesion initiation and cell spreading. These cellular defects are specifically caused by the inability of kindlin to bind β1-tail polypeptides carrying a phosphorylated threonine motif or phospho-mimicking TT788/789DD substitutions. Our findings indicate that the double-threonine motif in β1-class integrins is not a major phosphorylation site but if phosphorylated would curb integrin function.
    MeSH term(s) Amino Acid Motifs/physiology ; Animals ; Cells, Cultured ; Fibroblasts/metabolism ; Humans ; Integrin beta1/chemistry ; Integrin beta1/metabolism ; Mice ; Phosphorylation ; Threonine/chemistry ; Threonine/metabolism
    Chemical Substances Integrin beta1 ; Threonine (2ZD004190S)
    Language English
    Publishing date 2022-01-07
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2575-1077
    ISSN (online) 2575-1077
    DOI 10.26508/lsa.202101301
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