scholarly journals The F1 loop of the talin head domain acts as a gatekeeper in integrin activation and clustering

2020 ◽  
Vol 133 (19) ◽  
pp. jcs239202 ◽  
Author(s):  
Sampo Kukkurainen ◽  
Latifeh Azizi ◽  
Pingfeng Zhang ◽  
Marie-Claude Jacquier ◽  
Mo Baikoghli ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Cytoplasmic Tail ◽  
First Person ◽  
Integrin Activation ◽  
Inner Membrane ◽  
Flexible Loop ◽  
Head Domain ◽  
Integrin Clustering ◽  
Membrane Bound ◽  
Β3 Integrin

ABSTRACTIntegrin 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.

scholarly journals Dynamic changes in the osteoclast cytoskeleton in response to growth factors and cell attachment are controlled by β3 integrin

2003 ◽  
Vol 162 (3) ◽  
pp. 499-509 ◽  
Author(s):  
Roberta Faccio ◽  
Deborah V. Novack ◽  
Alberta Zallone ◽  
F. Patrick Ross ◽  
Steven L. Teitelbaum
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Attachment ◽  
Cytoplasmic Tail ◽  
Cytoplasmic Domain ◽  
Small Gtpases ◽  
Cytoskeletal Reorganization ◽  
Integrin Activation ◽  
Intracellular Signals ◽  
Β3 Integrin

The β3 integrin cytoplasmic domain, and specifically S752, is critical for integrin localization and osteoclast (OC) function. Because growth factors such as macrophage colony–stimulating factor and hepatocyte growth factor affect integrin activation and function via inside-out signaling, a process requiring the β integrin cytoplasmic tail, we examined the effect of these growth factors on OC precursors. To this end, we retrovirally expressed various β3 integrins with cytoplasmic tail mutations in β3-deficient OC precursors. We find that S752 in the β3 cytoplasmic tail is required for growth factor–induced integrin activation, cytoskeletal reorganization, and membrane protrusion, thereby affecting OC adhesion, migration, and bone resorption. The small GTPases Rho and Rac mediate cytoskeletal reorganization, and activation of each is defective in OC precursors lacking a functional β3 subunit. Activation of the upstream mediators c-Src and c-Cbl is also dependent on β3. Interestingly, although the FAK-related kinase Pyk2 interacts with c-Src and c-Cbl, its activation is not disrupted in the absence of functional β3. Instead, its activation is dependent upon intracellular calcium, and on the β2 integrin. Thus, the β3 cytoplasmic domain is responsible for activation of specific intracellular signals leading to cytoskeletal reorganization critical for OC function.

Substrate Stiffness as a Regulator in Catalyzing Integrin-Mediated Cell Adhesion Nucleation: A Mechanochemical Model

2013 ◽  
Vol 459 ◽  
pp. 555-559
Author(s):  
Xiao Ling Peng
Keyword(s):  
Cell Adhesion ◽  
Energy Input ◽  
Experimental Studies ◽  
Substrate Stiffness ◽  
Dependent Manner ◽  
Integrin Activation ◽  
A Value ◽  
Integrin Clustering ◽  
Mechanochemical Model

We provide here a simplified mechanochemical model to describe the role of substrate stiffness in mediating the chemical reactions between integrins on cell membrane and ligands immobilized on the substrate. By taking into account the energy input for integrin activation on a compliant substrate, Our simulation shows that integrin activation and the downstream integrin clustering can be regulated by substrate stiffness in a value-dependent manner, which is consistent with previous experimental studies.

scholarly journals Integrins: An Important Link between Angiogenesis, Inflammation and Eye Diseases

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1703
Author(s):  
Małgorzata Mrugacz ◽  
Anna Bryl ◽  
Mariusz Falkowski ◽  
Katarzyna Zorena
Keyword(s):  
Cell Adhesion ◽  
Tissue Repair ◽  
Normal Development ◽  
Cell Attachment ◽  
Biological Activities ◽  
Integrin Receptors ◽  
Cytokine Activation ◽  
Eye Disorders ◽  
Membrane Bound ◽  
Cell To Cell Adhesion

Integrins belong to a group of cell adhesion molecules (CAMs) which is a large group of membrane-bound proteins. They are responsible for cell attachment to the extracellular matrix (ECM) and signal transduction from the ECM to the cells. Integrins take part in many other biological activities, such as extravasation, cell-to-cell adhesion, migration, cytokine activation and release, and act as receptors for some viruses, including severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2). They play a pivotal role in cell proliferation, migration, apoptosis, tissue repair and are involved in the processes that are crucial to infection, inflammation and angiogenesis. Integrins have an important part in normal development and tissue homeostasis, and also in the development of pathological processes in the eye. This review presents the available evidence from human and animal research into integrin structure, classification, function and their role in inflammation, infection and angiogenesis in ocular diseases. Integrin receptors and ligands are clinically interesting and may be promising as new therapeutic targets in the treatment of some eye disorders.

scholarly journals CD44 and β3 Integrin Organize Two Functionally Distinct Actin-based Domains in Osteoclasts

2007 ◽  
Vol 18 (12) ◽  
pp. 4899-4910 ◽  
Author(s):  
Anne Chabadel ◽  
Inmaculada Bañon-Rodríguez ◽  
David Cluet ◽  
Brian B. Rudkin ◽  
Bernhard Wehrle-Haller ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Actin Cytoskeleton ◽  
Interacting Protein ◽  
Wiskott Aldrich Syndrome ◽  
Diffuse Cloud ◽  
Sealing Zone ◽  
Β3 Integrin ◽  
Syndrome Protein

The actin cytoskeleton of mature osteoclasts (OCs) adhering to nonmineralized substrates is organized in a belt of podosomes reminiscent of the sealing zone (SZ) found in bone resorbing OCs. In this study, we demonstrate that the belt is composed of two functionally different actin-based domains: podosome cores linked with CD44, which are involved in cell adhesion, and a diffuse cloud associated with β3 integrin, which is involved in cell adhesion and contraction. Wiskott Aldrich Syndrome Protein (WASp) Interacting Protein (WIP)−/− OCs were devoid of podosomes, but they still exhibited actin clouds. Indeed, WIP−/− OCs show diminished expression of WASp, which is required for podosome formation. CD44 is a novel marker of OC podosome cores and the first nonintegrin receptor detected in these structures. The importance of CD44 is revealed by showing that its clustering restores podosome cores and WASp expression in WIP−/− OCs. However, although CD44 signals are sufficient to form a SZ, the presence of WIP is indispensable for the formation of a fully functional SZ.

Abstract 496: Competition Between Filamin and Kindlin-2 Regulates Integrin Activation

2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Mitali Das ◽  
Sujay Ithychanda ◽  
Kamila Bledzka ◽  
Jun Qin ◽  
Edward F Plow
Keyword(s):  
Cell Migration ◽  
K562 Cells ◽  
Cell Types ◽  
Suppressive Effect ◽  
Integrin Activation ◽  
Intracellular Signals ◽  
Integrin Binding Site ◽  
Multiple Cell ◽  
Β3 Integrin ◽  
Inside Out

Cell migration and adhesion during hemostasis, angiogenesis and inflammation are dynamically regulated by integrin heterodimeric adhesion receptors. Their interactions with cytosolic proteins, filamin (FLN), talin (TLN) and Kindlin (Kn2) enable them to convey intracellular signals (inside-out-signaling) to the external environment by engaging extracellular matrix ligands. While TLN and Kn2 activate integrins, FLN inhibits cell migration. TLN and Kn2 bind to membrane-proximal and -distal NPxY motifs of β integrin cytoplasmic tails (CTs), respectively, and an integrin binding site for FLN resides in between these two sequences. Competition between TLN and FLN regulates integrin activation, but it is unknown if FLN and Kn2 compete and regulate integrin inside-out signaling. This competition was tested using αIIbβ3 (platelet-specific) and β7 (lymphocyte-specific; strong FLN binder) integrins in multiple cell types. siRNA depletion of FLNA in K562 cells stably expressing αIIbβ3 integrin (K562-αIIbβ3) significantly enhanced PAC-1 (specific for activated αIIbβ3) binding compared to control siRNA, demonstrating its effect on β3 activation. In pulldown assays using GST-β3 CT, Kn2 bound β3 in CHO lysates transfected with Kn2, either alone or with FLN repeat 21; however, FLN binding to β3 CT was observed only when FLN repeat 21 was expressed alone. Under similar conditions using GST-β7 CT, FLN-β7 interaction was not perturbed by Kn2. This was more pronounced in endothelial cell lysates where GST-β7 CT bound endogenous FLNA but not Kn2. Weak talin-β7 CT binding in this assay was noted. Moreover, in K562-αIIbβ3 cells, exogenous Kn2 overcame the suppressive effect of FLN on αIIbβ3 activation. Overall, our data shows that FLN inhibits β3 integrin function, and competition between FLN and Kn2 can indeed regulate integrin activation.

scholarly journals Fibroblast Growth Factor Receptor-Mediated Rescue of x-Ephrin B1-Induced Cell Dissociation in XenopusEmbryos

2000 ◽  
Vol 20 (2) ◽  
pp. 724-734 ◽  
Author(s):  
Lisa D. Chong ◽  
Eui Kyun Park ◽  
Erin Latimer ◽  
Robert Friesel ◽  
Ira O. Daar
Keyword(s):  
Cell Adhesion ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Tyrosine Kinases ◽  
Growth Factor Receptor ◽  
Fibroblast Growth ◽  
Fgf Receptor ◽  
Cell Adhesion And Migration ◽  
Membrane Bound ◽  
And Migration

ABSTRACT The Eph family of receptor tyrosine kinases and their membrane-bound ligands, the ephrins, have been implicated in regulating cell adhesion and migration during development by mediating cell-to-cell signaling events. Genetic evidence suggests that ephrins may transduce signals and become tyrosine phosphorylated during embryogenesis. However, the induction and functional significance of ephrin phosphorylation is not yet clear. Here, we report that when we used ectopically expressed proteins, we found that an activated fibroblast growth factor (FGF) receptor associated with and induced the phosphorylation of ephrin B1 on tyrosine. Moreover, this phosphorylation reduced the ability of overexpressed ephrin B1 to reduce cell adhesion. In addition, we identified a region in the cytoplasmic tail of ephrin B1 that is critical for interaction with the FGF receptor; we also report FGF-induced phosphorylation of ephrins in a neural tissue. This is the first demonstration of communication between the FGF receptor family and the Eph ligand family and implicates cross talk between these two cell surface molecules in regulating cell adhesion.

scholarly journals A LAD-III syndrome is associated with defective expression of the Rap-1 activator CalDAG-GEFI in lymphocytes, neutrophils, and platelets

2007 ◽  
Vol 204 (7) ◽  
pp. 1571-1582 ◽  
Author(s):  
Ronit Pasvolsky ◽  
Sara W. Feigelson ◽  
Sara Sebnem Kilic ◽  
Amos J. Simon ◽  
Guy Tal-Lapidot ◽  
...  
Keyword(s):  
T Lymphocytes ◽  
Leukocyte Adhesion ◽  
Splice Junction ◽  
Integrin Activation ◽  
Leukocyte Adhesion Deficiency ◽  
Protein Levels ◽  
Guanine Exchange Factor ◽  
Β3 Integrin ◽  
Inside Out

Leukocyte and platelet integrins rapidly alter their affinity and adhesiveness in response to various activation (inside-out) signals. A rare leukocyte adhesion deficiency (LAD), LAD-III, is associated with severe defects in leukocyte and platelet integrin activation. We report two new LAD cases in which lymphocytes, neutrophils, and platelets share severe defects in β1, β2, and β3 integrin activation. Patients were both homozygous for a splice junction mutation in their CalDAG-GEFI gene, which is a key Rap-1/2 guanine exchange factor (GEF). Both mRNA and protein levels of the GEF were diminished in LAD lymphocytes, neutrophils, and platelets. Consequently, LAD-III platelets failed to aggregate because of an impaired αIIbβ3 activation by key agonists. β2 integrins on LAD-III neutrophils were unable to mediate leukocyte arrest on TNFα-stimulated endothelium, despite normal selectin-mediated rolling. In situ subsecond activation of neutrophil β2 integrin adhesiveness by surface-bound chemoattractants and of primary T lymphocyte LFA-1 by the CXCL12 chemokine was abolished. Chemokine inside-out signals also failed to stimulate lymphocyte LFA-1 extension and high affinity epitopes. Chemokine-triggered VLA-4 adhesiveness in T lymphocytes was partially defective as well. These studies identify CalDAG-GEFI as a critical regulator of inside-out integrin activation in human T lymphocytes, neutrophils, and platelets.

Membrane protein import in yeast mitochondria

2000 ◽  
Vol 28 (4) ◽  
pp. 495-499 ◽  
Author(s):  
K. Tokatlidis ◽  
S. Vial ◽  
P. Luciano ◽  
M. Vergnolle ◽  
S. Clémence
Keyword(s):  
Membrane Protein ◽  
Molecular Mechanism ◽  
Protein Import ◽  
Mitochondrial Matrix ◽  
Yeast Mitochondria ◽  
Inner Membrane ◽  
Protein Insertion ◽  
The Past ◽  
Membrane Protein Insertion ◽  
Membrane Bound

The protein import pathway that targets proteins to the mitochondrial matrix has been extensively characterized in the past 15 years. Variations of this import pathway account for the sorting of proteins to other compartments as well, but the insertion of integral inner membrane proteins lacking a presequence is mediated by distinct translocation machinery. This consists of a complex of Tim9 and Tim10, two homologous, Zn2+-binding proteins that chaperone the passage of the hydrophobic precursor across the aqueous inter-membrane space. The precursor is then targeted to another, inner-membrane-bound, complex of at least five subunits that facilitates insertion. Biochemical and genetic experiments have identified the key components of this process; we are now starting to understand the molecular mechanism. This review highlights recent advances in this new membrane protein insertion pathway.

Freezing from the inside: Ice nucleation in Escherichia coli and Escherichia coli ghosts by inner membrane bound ice nucleation protein InaZ

2020 ◽  
Vol 15 (3) ◽  
pp. 031003
Author(s):  
Johannes Kassmannhuber ◽  
Sergio Mauri ◽  
Mascha Rauscher ◽  
Nadja Brait ◽  
Lea Schöner ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Ice Nucleation ◽  
Ice Nucleation Protein ◽  
Inner Membrane ◽  
Membrane Bound
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