Surface Recruitment but Not Activation of Integrin α
            <sub>IIb</sub>
            β
            <sub>3</sub>
            (GPIIb-IIIa) Requires a Functional Actin Cytoskeleton

Addo, John B.; Bray, Paul F.; Grigoryev, Dmitriy; Faraday, Nauder; Goldschmidt‐Clermont, Pascal J.

doi:10.1161/01.atv.15.9.1466

Cited by 25 publications

(13 citation statements)

References 30 publications

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“…Partial inhibition by cytochalasin B implies that translocation of a subset of GPIIb-IIIa involved actin depolymerization/polymerization. This agrees in part with a previous study by Addo et al [16] showing that ADP-induced translocation of GPIIb-IIIa in normal platelets is inhibited by cytochalasin D.…”

Section: Agonist Activation Caused Gpiib and Gpiiia To Reassociatesupporting

confidence: 93%

Reassociation and translocation of glycoprotein IIB-IIIA in EDTA-treated human platelets

Wong

2007

Platelets

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Platelet membrane glycoproteins IIb and IIIa form a calcium-dependent heterodimer that plays a key role in platelet adhesion and aggregation. The present objective was to measure the dissociation and reassociation of GPIIb-IIIa by flow cytometric analysis of platelets labelled with mAbs specific for the glycoprotein complex or each monomer. In agreement with previous studies, EDTA chelation of extracellular calcium, [Ca2+]o, dissociated the heterodimer in a time and temperature dependent manner. Agonist stimulation of EDTA-treated platelets induced subunits to reassociate with the following order of potency: thrombin > collagen > ADP. Two-fold increases in GPIIb-IIIa and GPIIb indicate that thrombin caused reassociation of surface subunits and concurrent translocation of complexes from intracellular pools. The latter was partially inhibited by cytochalasin B thus indicating that a subpopulation of GPIIb-IIIa required cytoskeletal remodelling for translocation. Surface GPIIIa as reported by anti-CD61 declined more and upregulated less compared with GPIIb-IIIa or GPIIb. Results suggest that EDTA incubation might have altered the conformation of this epitope and decreased mAb binding. Collagen induced GPIIb-IIIa reassociation but not translocation of cryptic complexes. BAPTA suppression of rises in cytosolic calcium concentration or low [Ca2+]o inhibited GPIIb-IIIa reassociation, thus indicating that this reaction was driven by signal transduction. Thrombin and collagen induced a comparable level of aggregation of EDTA-treated platelets despite a 3-fold difference in cell surface GPIIb-IIIa. It is concluded that the effects of EDTA on GPIIb-IIIa dissociation and loss of adhesive functions are largely but not completely reversible.

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Section: Agonist Activation Caused Gpiib and Gpiiia To Reassociatesupporting

confidence: 93%

Reassociation and translocation of glycoprotein IIB-IIIA in EDTA-treated human platelets

Wong

2007

Platelets

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“…Because cytochalasin D treatment or C. difficile toxin B treatment of ME180 cells diminishes cellular ACP accumulation, including surface staining in confocal images, we believe that actin polymerization is required for optimal ACP-receptor interaction at the cell surface. Apparently induced by the presence of free ACP, the actin-dependent process may include clustering, recruitment, recycling, affinity modulation, or synthesis of receptors; these processes require actin polymerization in other systems (43)(44)(45)(46)(47)(48). The tempo of the interaction and the lack of effect of brefeldin A treatment on association of ACP with ME180 cells suggest that de novo protein synthesis is not required for the interaction.…”

Section: N-terminal and Repeat Region Domains Are Necessary Formentioning

confidence: 99%

Alpha C Protein of Group B Streptococcus Binds Host Cell Surface Glycosaminoglycan and Enters Cells by an Actin-dependent Mechanism

Baron

Bolduc²,

Goldberg

et al. 2004

Journal of Biological Chemistry

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Group B Streptococcus (GBS) colonizes mucosal surfaces of the human gastrointestinal and gynecological tracts and causes disease in a wide range of patients. Invasive illness occurs after organisms traverse an epithelial boundary and enter deeper tissues. Previously we have reported that the alpha C protein (ACP) on the surface of GBS mediates GBS entry into ME180 cervical epithelial cells and GBS translocation across layers of these cells. We now demonstrate that ACP interacts with host cell glycosaminoglycan (GAG); the interaction of ACP with ME180 cells is inhibited if cells are pretreated with sodium chlorate, an inhibitor of sulfate incorporation, or with heparitinases. The interaction is also inhibited in the presence of soluble heparin or heparan sulfate or host cell-derived GAG. In addition, ACP binds soluble heparin specifically in inhibition and dot blot assays. After interaction with host GAG, soluble ACP enters ME180 cells and fractionates to the eukaryotic cell cytosol. These events are inhibited in cells pretreated with cytochalasin D or with Clostridium difficile toxin B. These data indicate that full-length ACP interacts with ME180 cell GAG and enters the eukaryotic cell cytosol by a mechanism that involves Rho GTPase-dependent actin rearrangements. We suggest that these molecular interactions drive ACP-mediated translocation of GBS across epithelial barriers, thereby facilitating invasive GBS infection.Streptococcus agalactiae (Group B Streptococcus, GBS) 1 has long been recognized as an important cause of infection in pregnant/peripartum women and neonates. A frequent colonizer of the human gastrointestinal and gynecological tracts, GBS has been noted more recently to cause a range of invasive syndromes in non-pregnant adults. Most commonly these patients have comorbid conditions, including malignancy, diabetes, and renal disease (1), that may predispose to bacterial invasion because of a loss of epithelial barrier protection in a chronically colonized site such as the rectum, vagina, cervix, urethra, skin, or pharynx. The molecular basis of the interaction between GBS and epithelial cells remains poorly understood.We have reported that the alpha C protein (ACP) on the surface of GBS interacts with epithelial cells. Expressed by many serotype Ia, Ib, and II GBS strains, ACP is the prototype for a family of Gram-positive surface proteins, the alpha-like proteins (Alps). Found on most GBS strains and some Enterococcus and group A Streptococcus strains, Alps share considerable sequence homology and common structural elements, including an N-terminal region, a series of tandem repeats of ϳ80 amino acids each, and a C-terminal region containing a cellwall anchor LPXTG motif common to several Gram-positive species. Despite the fact that these proteins may vary in size due to gene truncation within the repeat region (2), Alps elicit protective antibody in both adult and neonatal mouse models of GBS sepsis (3). In a neonatal mouse model of disease, deletion of the gene encoding ACP attenuates the virul...

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“…Platelet aggregation was studied on plateletrich plasma (PRP) obtained from the citrated blood of human volunteers under standardized conditions. 21 Platelet counts were normalized to 3ϫ10 8 mL Ϫ1 . PRP samples were preincubated with or without inhibitors (NAC, apyrase, genistin, or genistein) for 15 minutes at 37°C in 0.5-cm-diameter cuvettes before being supplemented with agonists (H 2 O 2 , NaVO 4 , ADP, arachidonate, and thrombin receptor TRAP), and then aggregation was followed for 15 to 30 minutes (single-channel aggregometer from Chrono-Log Corp).…”

Section: Platelet Aggregation Assaymentioning

confidence: 99%

“…22 Expressed in percent, aggregation at 30 minutes was recorded and normalized to a standard deflection, corresponding to light transmission through platelet-poor plasma. 21 For some experiments, platelets were washed as described 21 and then reconstituted at 3ϫ10 8 mL Ϫ1 in Tyrode's solution supplemented with fibrinogen (3 g/L).…”

Section: Platelet Aggregation Assaymentioning

confidence: 99%

“…The content of ␣-granules was not released on exposure of platelets to H 2 O 2 and NaVO 4 . Using the surface expression of P-selectin as a probe for ␣-granule secretion, 21 we found that the combination of H 2 O 2 and NaVO 4 had minimal effect on P-selectin expression on the surface of platelets in the absence of stirring (Figure 4).…”

Section: Activation Of Plateletmentioning

confidence: 99%

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Priming of Platelet α _IIb β ₃ by Oxidants Is Associated With Tyrosine Phosphorylation of β ₃

Irani

Pham

Coleman

et al. 1998

ATVB

Self Cite

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Abstract-Reactive oxygen species play an important role at the site of vascular injuries and arterial thromboses. We studied the mechanism mediating platelet aggregation induced by H 2 O 2 , a major cellular oxidant. Exposure to H 2 O 2 triggered platelet aggregation, but only when the platelets were stirred. Strong platelet aggregation induced by H 2 O 2 required the presence of the tyrosine phosphatase inhibitor sodium orthovanadate (NaVO 4 ) and was dependent on the participation of integrin ␣ IIb ␤ 3 (glycoprotein IIb-IIIa 2 Leukocytes and platelets have been found adjacent during acute coronary syndromes and even circulate as clusters in the blood of patients with unstable angina.3-5 Leukocytes and, in particular, neutrophils produce large amounts of reactive oxygen species (ROS), which could influence platelet function in a paracrine fashion. 6 Moreover, superoxide and hydroxyl radicals have been shown to be produced by anoxic and subsequently reoxygenated platelets.7 Previous studies on the effects of ROS and, in particular, hydrogen peroxide (H 2 O 2 ) on platelets indicated that ROS might exert a dual effect on platelets. In the presence of nitric oxide (NO), H 2 O 2 seems to potentiate the inhibitory effect of NO on agonist-mediated platelet activation. 8 In contrast, in the presence of arachidonate, H 2 O 2 enhances aggregation induced by phospholipid-derived arachidonate.9,10 To further characterize the effect of H 2 O 2 on platelet reactivity, we sought to characterize the effect of ROS and, in particular, of H 2 O 2 on platelet signaling pathways.Integrin ␣ IIb ␤ 3 , the classic platelet fibrinogen receptor, can exist in resting or activated states, and the latter can occur with or without ligand engagement. Activation corresponds to a structural change, whereby the affinity of ␣ IIb ␤ 3 for fibrinogen and other adhesive molecules in solution is markedly increased.11 Moreover, integrin ␣ IIb ␤ 3 can be found in 2 different compartments relative to extracellular ligands: exposed (to extracellular ligands) or cryptic (not accessible to extracellular ligands).12 Receptor molecules can be recruited from cryptic storage to the platelet surface or removed from the surface through a process of endocytosis.12-14 The molecular reactions that lead to receptor activation have been studied: ␤ 3 seems to play the role of a regulatory subunit of the receptor, whereas ␣ IIb appears to mediate receptor specificity. 15,16 There is good evidence that the activation process utilizes ATP 15 and involves interaction of the short cytoplasmic domain of ␤ 3 with a regulatory factor. 15,17,18 H 2 O 2 can induce a strong tyrosine kinase response in smooth muscle cells, especially in cells whose tyrosine phosphatases are concurrently inhibited with orthovanadate.

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Surface Recruitment but Not Activation of Integrin α _IIb β ₃ (GPIIb-IIIa) Requires a Functional Actin Cytoskeleton

Cited by 25 publications

References 30 publications

Reassociation and translocation of glycoprotein IIB-IIIA in EDTA-treated human platelets

Reassociation and translocation of glycoprotein IIB-IIIA in EDTA-treated human platelets

Alpha C Protein of Group B Streptococcus Binds Host Cell Surface Glycosaminoglycan and Enters Cells by an Actin-dependent Mechanism

Priming of Platelet α _IIb β ₃ by Oxidants Is Associated With Tyrosine Phosphorylation of β ₃

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Surface Recruitment but Not Activation of Integrin α IIb β 3 (GPIIb-IIIa) Requires a Functional Actin Cytoskeleton

Cited by 25 publications

References 30 publications

Reassociation and translocation of glycoprotein IIB-IIIA in EDTA-treated human platelets

Reassociation and translocation of glycoprotein IIB-IIIA in EDTA-treated human platelets

Alpha C Protein of Group B Streptococcus Binds Host Cell Surface Glycosaminoglycan and Enters Cells by an Actin-dependent Mechanism

Priming of Platelet α IIb β 3 by Oxidants Is Associated With Tyrosine Phosphorylation of β 3

Contact Info

Product

Resources

About

Surface Recruitment but Not Activation of Integrin α _IIb β ₃ (GPIIb-IIIa) Requires a Functional Actin Cytoskeleton

Priming of Platelet α _IIb β ₃ by Oxidants Is Associated With Tyrosine Phosphorylation of β ₃