Reinhard Fässler

Max Planck Institute of Biochemistry, München, Bavaria, Germany

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Publications (270)2369.21 Total impact

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    ABSTRACT: Integrins require an activation step prior to ligand binding and signaling. How talin and kindlin contribute to these events in non-hematopoietic cells is poorly understood. Here we report that fibroblasts lacking either talin or kindlin failed to activate β1 integrins, adhere to fibronectin (FN) or maintain their integrins in a high affinity conformation induced by Mn(2+). Despite compromised integrin activation and adhesion, Mn(2+) enabled talin- but not kindlin-deficient cells to initiate spreading on FN. This isotropic spreading was induced by the ability of kindlin to directly bind paxillin, which in turn bound focal adhesion kinase (FAK) resulting in FAK activation and the formation of lamellipodia. Our findings show that talin and kindlin cooperatively activate integrins leading to FN binding and adhesion, and that kindlin subsequently assembles an essential signaling node at newly formed adhesion sites in a talin-independent manner.
    Preview · Article · Jan 2016 · eLife Sciences
  • Benjamin Geiger · Reinhard Fässler

    No preview · Article · Jan 2016 · Experimental Cell Research
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    ABSTRACT: Hematopoietic cells depend on integrin-mediated adhesion and signaling, which is induced by kindlin-3 and talin-1. To determine whether platelet and polymorphonuclear neutrophil (PMNs) functions require specific thresholds of kindlin-3 we generated mouse strains expressing 50%, 10% or 5% of normal kindlin-3 levels. We report that in contrast to kindlin-3-null mice, which die perinatally of severe bleeding and leukocyte adhesion deficiency, mice expressing as little as 5% of kindlin-3 were viable and protected from spontaneous bleeding and infections. However, platelet adhesion and aggregation were reduced in vitro and bleeding times extended. Similarly, leukocyte adhesion, extravasation and bacterial clearance were diminished. Quantification of protein copy numbers revealed stoichiometric quantities of kindlin-3 and talin-1 in platelets and neutrophils indicating that reduction of kindlin-3 in our mouse strains progressively impairs the cooperation with talin-1. Our findings show that very low levels of kindlin-3 enable basal platelet and neutrophil functions, whereas in stress situations such as injury and infection platelets and neutrophils require a maximum of functional integrins that is achieved with high and stoichiometric quantities of kindlin-3 and talin-1.
    No preview · Article · Oct 2015 · Blood
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    ABSTRACT: Talin is an integrin adaptor, which controls integrin activity in all hematopoietic cells. How intracellular signals promote talin binding to the integrin tail leading to integrin activation is still poorly understood, especially in leukocytes. In vitro studies identified an integrin activation complex whose formation is initiated by the interaction of active, GTP-bound Rap1 with the adapter protein RIAM followed by the recruitment of talin to the plasma membrane. Unexpectedly, loss-of-function studies in mice have shown that the talin-activating role of RIAM is neither required for development nor for integrin activation in platelets. In this study, we show that leukocyte integrin activation critically depends on RIAM both in vitro and in vivo. RIAM deficiency results in a loss of β2 integrin activation in multiple leukocyte populations, impaired leukocyte adhesion to inflamed vessels and accumulation in the circulation. Surprisingly, however, the major leukocyte β1 integrin family member, α4β1 was only partially affected by RIAM deficiency in leukocytes. Thus, while talin is an essential, shared regulator of all integrin classes expressed by leukocytes, we report that β2 and α4 integrins use different RIAM-dependent and independent pathways to undergo activation by talin. Copyright © 2015 American Society of Hematology.
    No preview · Article · Sep 2015 · Blood
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    ABSTRACT: Hematopoietic stem cells (HSCs) generate highly dividing hematopoietic progenitor cells (HPCs), which produce all blood cell lineages. HSCs are usually quiescent, retained by integrins in specific niches, and become activated when the pools of HPCs decrease. We report that Kindlin-3-mediated integrin activation controls homing of HSCs to the bone marrow (BM) and the retention of activated HSCs and HPCs but not of quiescent HSCs in their BM niches. Consequently, Kindlin-3-deficient HSCs enter quiescence and remain in the BM when cotransplanted with wild-type hematopoietic stem and progenitor cells (HSPCs), whereas they are hyperactivated and lost in the circulation when wild-type HSPCs are absent, leading to their exhaustion and reduced survival of recipients. The accumulation of HSPCs in the circulation of leukocyte adhesion deficiency type III patients, who lack Kindlin-3, underlines the conserved functions of Kindlin-3 in man and the importance of our findings for human disease. © 2015 Ruppert et al.
    No preview · Article · Aug 2015 · Journal of Experimental Medicine
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    Filippo G. Giancotti · Reinhard Fässler

    Preview · Article · Aug 2015 · Journal of Cell Science
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    Full-text · Dataset · Jul 2015
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    Full-text · Dataset · Mar 2015
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    ABSTRACT: PINCH1 is a LIM-only domain protein that forms a ternary complex with integrin-linked kinase (ILK) and parvin (IPP complex) downstream of integrins. Here we demonstrate that PINCH-1 gene ablation in the epidermis of mice caused epidermal detachment from the basement membrane, epidermal hyperthickening and progressive hair loss. PINCH-1 deficient keratinocytes also displayed profound adhesion, spreading and migration defects in vitro that were, however, significantly more severe than those of ILK-deficient keratinocytes indicating that PINCH-1 also exerts functions in an ILK-independent manner. By isolating the PINCH-1 interactome, the LIM domain containing and actin-binding protein Epithelial Protein Lost in Neoplasm (EPLIN) was identified as a novel PINCH-1 associated protein. EPLIN localized in a PINCH-1-dependent manner to integrin adhesion sites of keratinocytes in vivo and in vitro and its depletion severely attenuated keratinocyte spreading and migration on collagen and fibronectin without affecting PINCH-1 levels in FAs. Since the low PINCH-1 levels in ILK-deficient keratinocytes were sufficient to recruit EPLIN to integrin adhesions, our findings suggest that PINCH-1 regulates integrin-mediated adhesion of keratinocytes through the interactions with ILK as well as EPLIN.
    Preview · Article · Jan 2015 · Journal of Cell Science
  • Zhiqi Sun · Armin Lambacher · Reinhard Fässler
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    ABSTRACT: Integrins assemble a complex network of molecular interactions at cell-matrix adhesion sites. Fluorescence correlation microscopy has now shed light on the spatial, temporal and numerical distributions of protein complexes during assembly and stabilization of nascent adhesions.
    No preview · Article · Sep 2014 · Current Biology
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    Ralph Thomas Böttcher · Reinhard Fässler
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    ABSTRACT: Integrins anchor cells to the extracellular matrix (ECM) and control a multitude of essential cellular functions by activating a variety of signaling pathways. In this issue of The EMBO Journal, a study conducted by Ferraris and colleagues report that binding of urokinase-type plasminogen activator receptor (uPAR) to vitronectin is sufficient to trigger ligand-independent β1 and β3 integrin signaling. The coupling of uPAR and integrins occurs independent of lateral interaction between the two receptors, but relies on membrane tension (Ferraris et al, 2014).
    Preview · Article · Sep 2014 · The EMBO Journal
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    ABSTRACT: Trafficking of α5β1 integrin to lysosomes and its subsequent degradation is influenced by ligand-occupancy and the binding of sorting nexin 17 (SNX17) via its protein 4.1, ezrin, radixin, moesin (FERM) domain to the membrane distal NPxY motif in the cytoplasmic domain of β1 integrin in early endosomes. Two other sorting nexin family members, namely SNX27 and SNX31, share with SNX17 next to their obligate phox domain a FERM domain, which may enable them to bind β integrin tails. Here we report that in addition to SNX17, SNX31 but not SNX27 binds several β integrin tails in early endosomes in a PI3-kinase-dependent manner. Similarly like SNX17, binding of SNX31 with β1 integrin tails in early endosomes occurs between the FERM domain and the membrane-distal NPxY motif in the β1 integrin cytoplasmic domain. Furthermore, expression of SNX31 rescues β1 integrin surface levels and stability in SNX17-depleted cells. In contrast to SNX17, expression of SNX31 is restricted and found highly expressed in bladder and melanoma tissue. Altogether, these results demonstrate that SNX31 is an endosomal regulator of β integrins with a restricted expression pattern.
    No preview · Article · Jul 2014 · Journal of Molecular Biology
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    ABSTRACT: Tubulointerstitial fibrosis underlies all forms of end-stage kidney disease. TGF-β mediates both the development and the progression of kidney fibrosis through binding and activation of the serine/threonine kinase type II TGF-β receptor (TβRII), which in turn promotes a TβRI-mediated SMAD-dependent fibrotic signaling cascade. Autophosphorylation of serine residues within TβRII is considered the principal regulatory mechanism of TβRII-induced signaling; however, there are 5 tyrosine residues within the cytoplasmic tail that could potentially mediate TβRII-dependent SMAD activation. Here, we determined that phosphorylation of tyrosines within the TβRII tail was essential for SMAD-dependent fibrotic signaling within cells of the kidney collecting duct. Conversely, the T cell protein tyrosine phosphatase (TCPTP) dephosphorylated TβRII tail tyrosine residues, resulting in inhibition of TβR-dependent fibrotic signaling. The collagen-binding receptor integrin α1β1 was required for recruitment of TCPTP to the TβRII tail, as mice lacking this integrin exhibited impaired TCPTP-mediated tyrosine dephosphorylation of TβRII that led to severe fibrosis in a unilateral ureteral obstruction model of renal fibrosis. Together, these findings uncover a crosstalk between integrin α1β1 and TβRII that is essential for TβRII-mediated SMAD activation and fibrotic signaling pathways.
    Full-text · Article · Jul 2014 · Journal of Clinical Investigation
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    ABSTRACT: The liver has a unique regenerative capability, which involves extensive remodelling of cell-cell and cell-matrix contacts. Here we study the role of integrins in mouse liver regeneration using Cre/loxP-mediated gene deletion or intravenous delivery of β1-integrin siRNA formulated into nanoparticles that predominantly target hepatocytes. We show that although short-term loss of β1-integrin has no obvious consequences for normal livers, partial hepatectomy leads to severe liver necrosis and reduced hepatocyte proliferation. Mechanistically, loss of β1-integrin in hepatocytes impairs ligand-induced phosphorylation of the epidermal growth factor and hepatocyte growth factor receptors, thereby attenuating downstream receptor signalling in vitro and in vivo. These results identify a crucial role and novel mechanism of action of β1-integrins in liver regeneration and demonstrate that protein depletion by nanoparticle-based delivery of specific siRNA is a powerful strategy to study gene function in the regenerating liver.
    No preview · Article · May 2014 · Nature Communications
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    ABSTRACT: Cell migration is mediated by the dynamic remodeling of focal adhesions (FAs). Recently, an important role of endosomal signaling in regulation of cell migration was recognized. Here, we show an essential function for late endosomes carrying the p14-MP1 (LAMTOR2/3) complex in FA dynamics. p14-MP1-positive endosomes move to the cell periphery along microtubules (MTs) in a kinesin1- and Arl8b-dependent manner. There they specifically target FAs to regulate FA turnover, which is required for cell migration. Using genetically modified fibroblasts from p14-deficient mice and Arl8b-depleted cells, we demonstrate that MT plus end-directed traffic of p14-MP1-positive endosomes triggered IQGAP1 disassociation from FAs. The release of IQGAP was required for FA dynamics. Taken together, our results suggest that late endosomes contribute to the regulation of cell migration by transporting the p14-MP1 scaffold complex to the vicinity of FAs.
    Full-text · Article · May 2014 · The Journal of Cell Biology
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    ABSTRACT: Kindlin-1 is an integrin tail binding protein that controls integrin activation. Mutations in the FERMT-1 gene, which encodes for Kindlin-1, lead to Kindler syndrome in man, which is characterized by skin blistering, premature skin aging and skin cancer of unknown etiology. Here we show that loss of Kindlin-1 in mouse keratinocytes recapitulates Kindler syndrome and also produces enlarged and hyperactive stem cell compartments, which lead to hyperthickened epidermis, ectopic hair follicle development and increased skin tumor susceptibility. Mechanistically, Kindlin-1 controls keratinocyte adhesion through β1-class integrins and proliferation and differentiation of cutaneous epithelial stem cells by promoting αvβ6 integrin-mediated transforming growth factor-β (TGF-β) activation and inhibiting Wnt-β-catenin signaling through integrin-independent regulation of Wnt ligand expression. Our findings assign Kindlin-1 the previously unknown and essential task of controlling cutaneous epithelial stem cell homeostasis by balancing TGF-β-mediated growth-inhibitory signals and Wnt-β-catenin-mediated growth-promoting signals.
    Full-text · Article · Mar 2014 · Nature medicine
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    ABSTRACT: The adhesive interactions of cells with their environment through the integrin family of transmembrane receptors have key roles in regulating multiple aspects of cellular physiology, including cell proliferation, viability, differentiation and migration. Consequently, failure to establish functional cell adhesions, and thus the assembly of associated cytoplasmic scaffolding and signalling networks, can have severe pathological effects. The roles of specific constituents of integrin-mediated adhesions, which are collectively known as the 'integrin adhesome', in diverse pathological states are becoming clear. Indeed, the prominence of mutations in specific adhesome molecules in various human diseases is now appreciated, and experimental as well as in silico approaches provide insights into the molecular mechanisms underlying these pathological conditions.
    No preview · Article · Mar 2014 · Nature Reviews Molecular Cell Biology
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    ABSTRACT: Collagens constitute nearly 30% of all proteins in our body. Type IV collagen is a major and crucial component of basement membranes. Collagen chains undergo several posttranslational modifications that are indispensable for proper collagen function. One of these modifications, prolyl 3-hydroxylation, is accomplished by a family of prolyl 3-hydroxylases (P3H1, P3H2, and P3H3). The present study shows that P3H2-null mice are embryonic-lethal by embryonic day 8.5. The mechanism of the unexpectedly early lethality involves the interaction of non-3-hydroxylated embryonic type IV collagen with the maternal platelet-specific glycoprotein VI (GPVI). This interaction results in maternal platelet aggregation, thrombosis of the maternal blood, and death of the embryo. The phenotype is completely rescued by producing double KOs of P3H2 and GPVI. Double nulls are viable and fertile. Under normal conditions, subendothelial collagens bear the GPVI-binding sites that initiate platelet aggregation upon blood exposure during injuries. In type IV collagen, these sites are normally 3-hydroxylated. Thus, prolyl 3-hydroxylation of type IV collagen has an important function preventing maternal platelet aggregation in response to the early developing embryo. A unique link between blood coagulation and the ECM is established. The newly described mechanism may elucidate some unexplained fetal losses in humans, where thrombosis is often observed at the maternal/fetal interface. Moreover, epigenetic silencing of P3H2 in breast cancers implies that the interaction between GPVI and non-3-hydroxylated type IV collagen might also play a role in the progression of malignant tumors and metastasis.
    No preview · Article · Dec 2013 · Proceedings of the National Academy of Sciences
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    Vaibhao C Janbandhu · Daniel Moik · Reinhard Fässler
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    ABSTRACT: The spatiotemporal manipulations of gene expression by the Cre recombinase (Cre) of bacteriophage P1 has become an essential asset to understanding mammalian genetics. Accumulating evidence suggests that Cre activity can, in addition to excising targeted loxP sites, induce cytotoxic effects, including abnormal cell cycle progression, genomic instability, and apoptosis, which can accelerate cancer progression. It is speculated that these defects are caused by Cre-induced DNA damage at off-target sites. Here we report the formation of tetraploid keratinocytes in the epidermis of keratin 5 and/or keratin 14 promoter-driven Cre (KRT5- and KRT14-Cre) expressing mouse skin. Biochemical analyses and flow cytometry demonstrated that Cre expression also induces DNA damage, genomic instability, and tetraploidy in HCT116 cells, and live-cell imaging revealed an extension of the G 2 cell cycle phase followed by defective or skipping of mitosis as cause for the tetraploidy. Since tetraploidy eventually leads to aneuploidy, a hallmark of cancer, our findings highlight the importance of distinguishing non-specific cytopathic effects from specific Cre/loxP-driven genetic manipulations when using Cre-mediated gene deletions.
    Preview · Article · Nov 2013 · Cell cycle (Georgetown, Tex.)
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    ABSTRACT: Increased ligand binding to cellular integrins ("activation") plays important roles in processes such as development, cell migration, extracellular matrix assembly, tumor metastasis, hemostasis, and thrombosis [1-5]. Integrin activation encompasses both increased integrin monomer affinity and increased receptor clustering [6] and depends on integrin-talin interactions [5]. Loss of kindlins results in reduced activation of integrins [7-13]. Kindlins might promote talin binding to integrins through a cooperative mechanism [5, 14-16]; however, kindlins do not increase talin association with integrins [17]. Here, we report that, unlike talin head domain (THD), kindlin-3 has little effect on the affinity of purified monomeric αIIbβ3, and it does not enhance activation by THD. Furthermore, studies with ligands of varying valency show that kindlins primarily increase cellular αIIbβ3 avidity rather than monomer affinity. In platelets or nucleated cells, loss of kindlins markedly reduces αIIbβ3 binding to multivalent but not monovalent ligands. Finally, silencing of kindlins reduces the clustering of ligand-occupied αIIbβ3 as revealed by total internal reflection fluorescence and electron microscopy. Thus, in contrast to talins, kindlins have little primary effect on integrin αIIbβ3 affinity for monovalent ligands and increase multivalent ligand binding by promoting the clustering of talin-activated integrins.
    Full-text · Article · Nov 2013 · Current biology: CB

Publication Stats

20k Citations
2,369.21 Total Impact Points


  • 1996-2015
    • Max Planck Institute of Biochemistry
      • Department of Molecular Medicine
      München, Bavaria, Germany
  • 2012
    • Johns Hopkins University
      Baltimore, Maryland, United States
  • 2011
    • Max Planck Institute for Biology of Ageing
      Köln, North Rhine-Westphalia, Germany
  • 2010
    • Universität Heidelberg
      Heidelburg, Baden-Württemberg, Germany
  • 1999-2008
    • Ludwig-Maximilians-University of Munich
      • Max-von-Pettenkofer Institute for Hygiene and Medical Microbiology
      München, Bavaria, Germany
  • 2007
    • University of Sydney
      • School of Medical Sciences
      Sydney, New South Wales, Australia
  • 1998-2006
    • Lund University
      • Department of Paediatrics
      Lund, Skåne, Sweden
    • University of Vienna
      • Institute of Neurophysiology
      Wien, Vienna, Austria
    • University of Wisconsin–Madison
      • Department of Medicine
      Madison, Wisconsin, United States
  • 1997-2006
    • University of Cologne
      • • Institute for Genetics
      • • Institute of Anatomy I
      Köln, North Rhine-Westphalia, Germany
  • 2002
    • Umeå University
      Umeå, Västerbotten, Sweden
    • Sigmund-Freud-Institut
      Frankfurt, Hesse, Germany
  • 2000
    • Ghent University
      Gand, Flanders, Belgium
  • 1995
    • Harvard University
      Cambridge, Massachusetts, United States
    • University of Alberta
      • Faculty of Pharmacy and Pharmaceutical Sciences
      Edmonton, Alberta, Canada