scholarly journals Skap2 is required for β2 integrin–mediated neutrophil recruitment and functions

2017 ◽  
Vol 214 (3) ◽  
pp. 851-874 ◽  
Author(s):  
Mark Boras ◽  
Stephanie Volmering ◽  
Arne Bokemeyer ◽  
Jan Rossaint ◽  
Helena Block ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Leukocyte Adhesion ◽  
Direct Interaction ◽  
Neutrophil Recruitment ◽  
Integrin Activation ◽  
Leukocyte Adhesion Deficiency ◽  
Β2 Integrin ◽  
Syndrome Protein

Integrin activation is required for neutrophil functions. Impaired integrin activation on neutrophils is the hallmark of leukocyte adhesion deficiency (LAD) syndrome in humans, characterized by impaired leukocyte recruitment and recurrent infections. The Src kinase–associated phosphoprotein 2 (Skap2) is involved in integrin functions in different leukocyte subtypes. However, the role of Skap2 in β2 integrin activation and neutrophil recruitment is unknown. In this study, we demonstrate the crucial role of Skap2 in regulating actin polymerization and binding of talin-1 and kindlin-3 to the β2 integrin cytoplasmic domain, thereby being indispensable for β2 integrin activation and neutrophil recruitment. The direct interaction of Skap2 with the Wiskott–Aldrich syndrome protein via its SH3 domain is critical for integrin activation and neutrophil recruitment in vivo. Furthermore, Skap2 regulates integrin-mediated outside-in signaling events and neutrophil functions. Thus, Skap2 is essential to activate the β2 integrins, and loss of Skap2 function is sufficient to cause a LAD-like phenotype in mice.

scholarly journals Direct Rap1/Talin1 interaction regulates platelet and neutrophil integrin activity in mice

Blood ◽  
2018 ◽  
Vol 132 (26) ◽  
pp. 2754-2762 ◽  
Author(s):  
Thomas Bromberger ◽  
Sarah Klapproth ◽  
Ina Rohwedder ◽  
Liang Zhu ◽  
Laura Mittmann ◽  
...  
Keyword(s):  
Leukocyte Adhesion ◽  
Thrombus Formation ◽  
Alternative Mechanism ◽  
Integrin Activation ◽  
Vessel Occlusion ◽  
Crucial Step ◽  
Β2 Integrin ◽  
Biological Studies ◽  
Integrin Ligands

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.

Mice Lacking the Signaling Molecule, CalDAG-GEFI, Represent a Mouse Model for Leukocyte Adhesion Deficiency Type III.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 674-674
Author(s):  
Wolfgang Bergmeier ◽  
Tobias Goerge ◽  
Hong-Wei Wang ◽  
Stephen M. Cifuni ◽  
Jill R. Crittenden ◽  
...  
Keyword(s):  
Intracellular Signaling ◽  
Leukocyte Adhesion ◽  
Thrombus Formation ◽  
Neutrophil Infiltration ◽  
Neutrophil Function ◽  
Calcium Flux ◽  
Leukocyte Adhesion Deficiency ◽  
Normal Surface

Abstract Defective inside-out activation of β 1, β 2, and β 3 integrins in platelets and leukocytes is a main characteristic of patients with leukocyte adhesion deficiency (LAD)-III syndrome. We have recently shown that CalDAG-GEFI, a member of the CalDAG-GEF/RasGRP family of intracellular signaling molecules that catalyzes the exchange of GTP for GDP bound to Rap1, plays a key role for the activation of α IIbβ 3 in murine platelets. Here we studied the role of CalDAG-GEFI for neutrophil function as well as the activation of β 1 integrins in platelets. Neutrophils from CalDAG-GEFI−/ − mice showed normal surface expression of key adhesion receptors such as L-selectin, PSGL-1, or β 1/β 2 integrins. Calcium flux, degranulation, and oxygen radical formation were similar in wild-type (WT) and mutant cells. In contrast, β 2 integrin-mediated adhesion to fibrinogen was significantly reduced in cells lacking CalDAG-GEFI when compared to controls. In vivo, CalDAG-GEFI-deficient neutrophils showed normal rolling along stimulated venules, while firm adhesion was almost completely inhibited. A similar defect in firm adhesion was observed in WT mice pre-treated with blocking antibodies against β 2 integrins. To determine the role of CalDAG-GEFI in neutrophil emigration, inflammation was induced in the peritoneum or the skin. In both models, neutrophil infiltration was significantly reduced in CalDAG-GEFI−/ − mice when compared to controls. We further demonstrate that CalDAG-GEFI regulates the activation of β 1 integrins in platelets and that CalDAG-GEFI-deficiency leads to a complete inhibition of arterial thrombus formation in mice. Due to its central role in the activation of β 1, β 2, and β 3 integrins, we propose CalDAG-GEFI as a candidate gene defective in LAD-III patients.

β2-integrin activity: the role of thiols

Blood ◽  
2013 ◽  
Vol 121 (19) ◽  
pp. 3779-3780 ◽  
Author(s):  
Alexander Zarbock
Keyword(s):  
Disulfide Bonds ◽  
Protein Disulfide Isomerase ◽  
Neutrophil Recruitment ◽  
Regulatory Effect ◽  
Disulfide Isomerase ◽  
Isomerase Activity ◽  
Β2 Integrin ◽  
Protein Disulfide

In this issue of Blood, Hahm and colleagues identify the extracellular protein disulfide isomerase (PDI) as an essential regulator of the adhesiveness of the β2-integrin macrophage-1 antigen (Mac-1) on neutrophils.1 In the absence of PDI, Mac-1–dependent neutrophil adhesion and crawling is reduced in vivo. Rescue experiments with exogenous PDI showed that the isomerase activity of extracellular PDI is critical for its regulatory effect on neutrophil recruitment. This intriguing finding suggests that disulfide bonds in Mac-1 regulate integrin activity and neutrophil recruitment.

scholarly journals A novel pathway of rapid TLR-triggered activation of integrin-dependent leukocyte adhesion that requires Rap1 GTPase

2014 ◽  
Vol 25 (19) ◽  
pp. 2948-2955 ◽  
Author(s):  
Kyoung-Jin Chung ◽  
Ioannis Mitroulis ◽  
Johannes R. Wiessner ◽  
Ying Yi Zheng ◽  
Gabriele Siegert ◽  
...  
Keyword(s):  
Leukocyte Adhesion ◽  
Integrin Activation ◽  
Pathogen Invasion ◽  
Β2 Integrin ◽  
Tlr2 Ligand ◽  
Species Production ◽  
Rapid Activation ◽  
Slow Rolling ◽  
Inside Out

Rapid β2-integrin activation is indispensable for leukocyte adhesion and recruitment to sites of infection and is mediated by chemokine- or P-selectin glycoprotein ligand-1–induced inside-out signaling. Here we uncovered a novel pathway for rapid activation of integrin-dependent leukocyte adhesion, triggered by toll-like receptor (TLR)–mediated signaling. TLR2 or TLR5 ligation rapidly activated integrin-dependent leukocyte adhesion to immobilized ICAM-1 and fibronectin. Consistently, in vivo administration of the TLR2-ligand Pam3CSK4 increased integrin-dependent slow rolling and adhesion to endothelium within minutes, as identified by intravital microscopy in the cremaster model. TLR2 and TLR5 ligation increased β2-integrin affinity, as assessed by the detection of activation-dependent neoepitopes. TLR2- and TLR5-triggered integrin activation in leukocytes required enhanced Rap1 GTPase activity, which was mediated by Rac1 activation and NADPH oxidase-2–dependent reactive oxygen species production. This novel direct pathway linking initial pathogen recognition by TLRs to rapid β2-integrin activation may critically regulate acute leukocyte infiltration to sites of pathogen invasion.

scholarly journals Positive Regulation of fur Gene Expression via Direct Interaction of Fur in a Pathogenic Bacterium, Vibrio vulnificus

2007 ◽  
Vol 189 (7) ◽  
pp. 2629-2636 ◽  
Author(s):  
Hyun-Jung Lee ◽  
So Hyun Bang ◽  
Kyu-Ho Lee ◽  
Soon-Jung Park
Keyword(s):  
Gene Expression ◽  
Pathogenic Bacteria ◽  
Vibrio Vulnificus ◽  
Iron Concentration ◽  
Direct Interaction ◽  
Repeated Sequence ◽  
Upstream Region ◽  
Fur Protein

ABSTRACT In pathogenic bacteria, the ability to acquire iron, which is mainly regulated by the ferric uptake regulator (Fur), is essential to maintain growth as well as its virulence. In Vibrio vulnificus, a human pathogen causing gastroenteritis and septicemia, fur gene expression is positively regulated by Fur when the iron concentration is limited (H.-J. Lee et al., J. Bacteriol. 185:5891-5896, 2003). Footprinting analysis revealed that an upstream region of the fur gene was protected by the Fur protein from DNase I under iron-depleted conditions. The protected region, from −142 to −106 relative to the transcription start site of the fur gene, contains distinct AT-rich repeats. Mutagenesis of this repeated sequence resulted in abolishment of binding by Fur. To confirm the role of this cis-acting element in Fur-mediated control of its own gene in vivo, fur expression was monitored in V. vulnificus strains using a transcriptional fusion containing the mutagenized Fur-binding site (fur mt::luxAB). Expression of fur mt::luxAB showed that it was not regulated by Fur and was not influenced by iron concentration. Therefore, this study demonstrates that V. vulnificus Fur acts as a positive regulator under iron-limited conditions by direct interaction with the fur upstream region.

LAD-III, a leukocyte adhesion deficiency syndrome associated with defective Rap1 activation and impaired stabilization of integrin bonds

Blood ◽  
2004 ◽  
Vol 103 (3) ◽  
pp. 1033-1036 ◽  
Author(s):  
Tatsuo Kinashi ◽  
Memet Aker ◽  
Maya Sokolovsky-Eisenberg ◽  
Valentin Grabovsky ◽  
Chisato Tanaka ◽  
...  
Keyword(s):  
Shear Flow ◽  
Ligand Binding ◽  
Phorbol Esters ◽  
Leukocyte Adhesion ◽  
Deficiency Syndrome ◽  
Small Gtpase ◽  
High Avidity ◽  
Integrin Activation ◽  
Leukocyte Adhesion Deficiency ◽  
Rap1 Activation

AbstractRecently, we reported a rare leukocyte adhesion deficiency (LAD) associated with severe defects in integrin activation by chemokine signals, despite normal ligand binding of leukocyte integrins.1 We now report that the small GTPase, Rap1, a key regulator of inside-out integrin activation is abnormally regulated in LAD Epstein-Barr virus (EBV) lymphocyte cells. Both constitutive and chemokine-triggered activation of Rap1 were abolished in LAD lymphocytes despite normal chemokine signaling. Nevertheless, Rap1 expression and activation by phorbol esters were intact, ruling out an LAD defect in Rap1 guanosine triphosphate (GTP) loading. The very late antigen 4 (VLA-4) integrin abnormally tethered LAD EBV lymphocytes to its ligand vascular cell adhesion molecule 1 (VCAM-1) under shear flow due to impaired generation of high-avidity contacts despite normal ligand binding and intact avidity to surface-bound anti-VLA-4 monoclonal antibody (mAb). Thus, a defect in constitutive Rap1 activation results in an inability of ligand-occupied integrins to generate high-avidity binding to ligand under shear flow. This is a first report of an inherited Rap1 activation defect associated with a pathologic disorder in leukocyte integrin function, we herein term it “LAD-III.” (Blood. 2004;103:1033-1036)

scholarly journals Differential attenuation of β2 integrin–dependent and –independent neutrophil migration by Ly6G ligation

2019 ◽  
Vol 3 (3) ◽  
pp. 256-267 ◽  
Author(s):  
Pierre Cunin ◽  
Pui Y. Lee ◽  
Edy Kim ◽  
Angela B. Schmider ◽  
Nathalie Cloutier ◽  
...  
Keyword(s):  
Interleukin 1 ◽  
Neutrophil Migration ◽  
Surface Protein ◽  
Joint Inflammation ◽  
Selective Inhibition ◽  
Β2 Integrin ◽  
Β2 Integrins ◽  
Neutrophil Surface

Abstract Antibody ligation of the murine neutrophil surface protein Ly6G disrupts neutrophil migration in some contexts but not others. We tested whether this variability reflected divergent dependence of neutrophil migration on β2 integrins, adhesion molecules that interact with Ly6G at the neutrophil surface. In integrin-dependent murine arthritis, Ly6G ligation attenuated joint inflammation, even though mice lacking Ly6G altogether developed arthritis normally. By contrast, Ly6G ligation had no impact on integrin-independent neutrophil migration into inflamed lung. In peritoneum, the role of β2 integrins varied with stimulus, proving dispensable for neutrophil entry in Escherichia coli peritonitis but contributory in interleukin 1 (IL-1)–mediated sterile peritonitis. Correspondingly, Ly6G ligation attenuated only IL-1 peritonitis, disrupting the molecular association between integrins and Ly6G and inducing cell-intrinsic blockade restricted to integrin-dependent migration. Consistent with this observation, Ly6G ligation impaired integrin-mediated postadhesion strengthening for neutrophils arresting on activated cremaster endothelium in vivo. Together, these findings identify selective inhibition of integrin-mediated neutrophil emigration through Ly6G ligation, highlighting the marked site and stimulus specificity of β2 integrin dependence in neutrophil migration.

scholarly journals Selectins mediate eosinophil recruitment in vivo: a comparison with their role in neutrophil influx

Blood ◽  
1996 ◽  
Vol 87 (12) ◽  
pp. 5297-5304 ◽  
Author(s):  
GM Henriques ◽  
JM Miotla ◽  
SB Cordeiro ◽  
BA Wolitzky ◽  
ST Woolley ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Adhesion Molecule ◽  
Functional Redundancy ◽  
Neutrophil Recruitment ◽  
Eosinophil Recruitment ◽  
Neutrophil Influx ◽  
Eosinophil Accumulation

The role of selectins in mediating eosinophil recruitment in vivo was assessed in a model of lipopolysaccharide (LPS)-induced mouse pleurisy. LPS administration resulted in significant eosinophil influx at 24 hours, whereas neutrophil recruitment to the cavity peaked at 4 hours and persisted for 24 hours. The anti-L-selectin monoclonal antibody (MoAb) MEL-14 effectively inhibited (by 97%) eosinophil influx at 24 hours and also inhibited neutrophil recruitment at both times (75% to 95%). Eosinophil recruitment was partially reduced (54%) by the anti-P- selectin MoAb 5H1 but, in contrast, was unaffected by the anti-E- selectin MoAb 10E6. Neutrophil influx at 4 or 24 hours was not affected by the anti-P- or anti-E-selectin MoAbs. However, coadministration of anti-P-selectin and anti-E-selectin was very effective at inhibiting eosinophil influx at 24 hours (86%) and neutrophil influx at 4 (93%) and 24 hours (92%). These results show that all three selectins play a role in LPS-induced eosinophil and neutrophil recruitment in vivo, although P- and E-selectin show a degree of functional redundancy. The demonstration that P-selectin mediates eosinophil but not neutrophil influx suggests that suppressing the function of this adhesion molecule may be beneficial in blocking eosinophil accumulation in pleural inflammation.

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