| 1. |
- Dib, Karim, et al.
(författare)
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beta 2 Integrins target Rap GTPases to the plasma membrane by means of degranulation
- 2008
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 376:4, s. 642-646
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Tidskriftsartikel (refereegranskat)abstract
- We report the novel observation that engagement of beta 2 integrins on human neutrophils is accompanied by increased levels of the small GTPases Rap1 and Rap2 in a membrane-enriched fraction and a concomitant decrease of these proteins in a granule-enriched fraction. In parallel, we observed a similar time-dependent decrease of gelatinase B (a marker of specific and gelatinase B-containing granules) but not myeloperoxidase (a marker of azurophil granules) in the granule fraction, and release of lactoferrin (a marker of specific granules) in the extracellular medium. Furthermore, inhibition of Src tyrosine kinases, or phosphoinositide 3-kinase with PP1 or LY294002, respectively, blocked 02 integrin-induced degranulation and the redistribution of Rap1 and Rap2 to a membrane-enriched fraction. Consequently, the 02 integrin-dependent exocytosis of specific and gelatinase B-containing granules occurs via a Src tyrosine kinase/phosphoinositide 3-kinase signaling pathway and is responsible for the translocation of Rap1 and Rap2 to the plasma membrane in human neutrophils. (C) 2008 Elsevier Inc. All rights reserved.
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| 2. |
- Dib, Karim, et al.
(författare)
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Down-regulation of Rac activity during beta 2 integrin-mediated adhesion of human neutrophils
- 2003
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 278:26, s. 24181-24188
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Tidskriftsartikel (refereegranskat)abstract
- In human neutrophils, beta2 integrin engagement mediated a decrease in GTP-bound Rac1 and Rac2. Pretreatment of neutrophils with LY294002 or PP1 (inhibiting phosphatidylinositol 3-kinase (PI 3-kinase) and Src kinases, respectively) partly reversed the beta2 integrin-induced down-regulation of Rac activities. In contrast, beta2 integrins induced stimulation of Cdc42 that was independent of Src family members. The PI 3-kinase dependence of the beta2 integrin-mediated decrease in GTP-bound Rac could be explained by an enhanced Rac-GAP activity, since this activity was blocked by LY204002, whereas PP1 only had a minor effect. The fact that only Rac1 but not Rac2 (the dominating Rac) redistributed to the detergent-insoluble fraction and that it was independent of GTP loading excludes the possibility that down-regulation of Rac activities was due to depletion of GTP-bound Rac from the detergent-soluble fraction. The beta2 integrin-triggered relocalization of Rac1 to the cytoskeleton was enabled by a PI 3-kinase-induced dissociation of Rac1 from LyGDI. The dissociations of Rac1 and Rac2 from LyGDI also explained the PI 3-kinase-dependent translocations of Rac GTPases to the plasma membrane. However, these accumulations of Rac in the membrane, as well as that of p47phox and p67phox, were also regulated by Src tyrosine kinases. Inasmuch as Rac GTPases are part of the NADPH oxidase and the respiratory burst is elicited in neutrophils adherent by beta2 integrins, our results indicate that activation of the NADPH oxidase does not depend on the levels of Rac-GTP but instead requires a beta2 integrin-induced targeting of the Rac GTPases as well as p47phox and p67phox to the plasma membrane.
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| 3. |
- Dib, Karim, et al.
(författare)
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Role of p190RhoGAP in beta(2) integrin regulation of RhoA in human neutrophils
- 2001
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Ingår i: Journal of Immunology. - 1550-6606. ; 166:10, s. 6311-6322
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Tidskriftsartikel (refereegranskat)abstract
- We found that engagement of beta (2) integrins on human neutrophils induced activation of RhoA, as indicated by the increased ratio of GTP:GTP + GDP recovered on RhoA and translocation of RhoA to a membrane fraction. The clustering of beta (2) integrins also induced a time-dependent increase in GDP bound to RhoA, which correlated with beta (2) integrin-induced activation of p190RhoGAP. The activation of p190RhoGAP was completely blocked by [4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine] (PP1), a selective inhibitor of Src family tyrosine kinases. However, clustering of beta (2) integrins did not increase the basal tyrosine phosphorylation of p190RhoGAP, nor did it affect the amount of p120RasGAP bound to p190RhoGAP. Instead, the beta (2) integrin-induced activation of p190RhoGAP was accompanied by increased tyrosine phosphorylation of a p190RhoGAP-associated protein, p120RasGAP, and accumulation of both p120RasGAP and p190RhoGAP in a membrane fraction. PP1 blocked the beta (2) integrin-induced phosphorylation of p120RasGAP, as well as the translocation of p190RhoGAP and p120RasGAP, but it did not affect the accumulation of RhoA in the membrane fraction. In agreement with the mentioned findings, PP1 also increased the GTP:GTP + GDP ratio recovered on RhoA immunoprecipitated from beta (2) integrin-stimulated cells. Thus, in neutrophils, beta (2) integrin-induced activation of p190RhoGAP requires a signal from a Src family tyrosine kinase, but it does not occur via the signaling pathway responsible for activation of RhoA.
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| 4. |
- Jenei, V, et al.
(författare)
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E3B1, a human homologue of the mouse gene product Abi-1, sensitizes activation of Rap1 in response to epidermal growth factor
- 2005
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 1090-2422 .- 0014-4827. ; 310:2, s. 463-473
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Tidskriftsartikel (refereegranskat)abstract
- E3B1, a human homologue of the mouse gene product Abi-1, has been implicated in growth-factor-mediated regulation of the small GTPases p21(Ras) and Rac. E3b1 is a regulator of Rac because it can form a complex with Sos-1 and eps8, and such a Sos-1-e3B1-eps8 complex serves as a guanine nucleotide exchange factor for Rac. In the present study, we found that overexpression of e3B1 in NIH3T3/ EGFR cells sensitized EGF-induced activation of Rac1, whereas it had no impact on EGF-induced activation of p21(Ras). Remarkably, we found that EGF-induced activation of the p21(Ras)-related GTPase Rapt was also sensitized in NIH3T3/EGFR-e3B1 cells. Thus, in NIH3T3/ EGFR-e3B1 cells, maximal EGF-induced activation of Rap1 occurs with a dose of EGF much lower than in NIH3T3/EGFR cells. We also report that overexpression of e3B1 in NIH3T3/EGFR cells renders EGF-induced activation of Rapt completely dependent on Src tyrosine kinases but not on c-Abl. However, EGF-induced tyrosine phosphorylation of the Rap GEF C3G occurred regardless of whether e3B1 was overexpressed or not, and this did not involve Src tyrosine kinases. Accordingly, we propose that overexpression of e3B1 in NIH3T3/EGFR cells leads to mobilization of Src tyrosine kinases that participate in EGF-induced activation of Rap1 and inhibition of cell proliferation.
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| 5. |
- Jenei, Veronika, et al.
(författare)
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Nitric oxide produced in response to engagement of beta 2 integrins on human neutrophils activates the monomeric GTPases Rap1 and Rap2 and promotes adhesion
- 2006
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 281:46, s. 35008-35020
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Tidskriftsartikel (refereegranskat)abstract
- We found that engagement of beta 2 integrins on human neutrophils increased the levels of GTP-bound Rap1 and Rap2. Also, the activation of Rap1 was blocked by PP1, SU6656, LY294002, GF109203X, or BAPTA-AM, which indicates that the downstream signaling events in Rap1 activation involve Src tyrosine kinases, phosphoinositide 3-kinase, protein kinase C, and release of calcium. Surprisingly, the beta 2 integrin-induced activation of Rap2 was not regulated by any of the signaling pathways mentioned above. However, we identified nitric oxide as the signaling molecule involved in beta 2 integrin-induced activation of Rap1 and Rap2. This was illustrated by the fact that engagement of beta 2 integrins increased the production of nitrite, a stable end-product of nitric oxide. Furthermore, pretreatment of neutrophils with N-omega-mono-methy1-L-arginine, or 1400W, which are inhibitors of inducible nitric- oxide synthase, blocked beta 2 integrin-induced activation of Rap1 and Rap2. Similarly, R-P-8pCPT-cGMPS, an inhibitor of cGMP-dependent serine/threonine kinases, also blunted the beta 2 integrin-induced activation of Rap GTPases. Also nitric oxide production and its downstream activation of cGMP-dependent serine/threonine kinases were essential for proper neutrophil adhesion by beta 2 integrins. Thus, we made the novel findings that beta 2 integrin engagement on human neutrophils triggers production of nitric oxide and its downstream signaling is essential for activation of Rap GTPases and neutrophil adhesion.
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| 6. |
- McAuley, Daniel F., et al.
(författare)
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Simvastatin decreases the level of heparin-binding protein in patients with acute lung injury
- 2013
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Ingår i: BMC Pulmonary Medicine. - : Springer Science and Business Media LLC. - 1471-2466. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: Heparin-binding protein is released by neutrophils during inflammation and disrupts the integrity of the alveolar and capillary endothelial barrier implicated in the development of acute lung injury and systemic organ failure. We sought to investigate whether oral administration of simvastatin to patients with acute lung injury reduces plasma heparin-binding protein levels and improves intensive care unit outcome. Methods: Blood samples were collected from patients with acute lung injury with 48 h of onset of acute lung injury (day 0), day 3, and day 7. Patients were given placebo or 80 mg simvastatin for up to 14 days. Plasma heparin-binding protein levels from patients with acute lung injury and healthy volunteers were measured by ELISA. Results: Levels of plasma heparin-binding protein were significantly higher in patients with acute lung injury than healthy volunteers on day 0 (p = 0.011). Simvastatin 80 mg administered enterally for 14 days reduced plasma level of heparin-binding protein in patients. Reduced heparin-binding protein was associated with improved intensive care unit survival. Conclusions: A reduction in heparin-binding protein with simvastatin is a potential mechanism by which the statin may modify outcome from acute lung injury.
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