Topographical Association of the Platelet Fc-receptor with the Glycoprotein IIb-IIIa Complex

Berndt, Michael C.; Мазуров, А. В.; Vinogradov, D. V.; Burns, Gordon F.; Chesterman, C N

doi:10.3109/09537109309013216

Cited by 16 publications

(10 citation statements)

References 29 publications

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“…While there is no evidence for a direct physical association between αIIbβ3 and FcγRIIa, and they cannot be coimmunoprecipitated from detergent lysates (P.J. Newman and C. Gao, unpublished observations), they do appear to be topographically close to each other on the platelet surface, as evidenced by the finding that several αIIbβ3-specific mAbs, when prebound, are able to sterically block the binding of the anti-FcγRIIa mAb IV.3 (67,68). Because αIIbβ3 complexes are present at relatively high density on the platelet surface (~40,000-80,000 per platelet; refs.…”

Section: Discussionmentioning

confidence: 99%

Eptifibatide-induced thrombocytopenia and thrombosis in humans require FcγRIIa and the integrin β3 cytoplasmic domain

Gao¹,

Boylan²,

Bougie³

et al. 2009

J. Clin. Invest.

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Thrombocytopenia and thrombosis following treatment with the integrin αIIbβ3 antagonist eptifibatide are rare complications caused by patient antibodies specific for ligand-occupied αIIbβ3. Whether such antibodies induce platelet clearance by simple opsonization, by inducing mild platelet activation, or both is poorly understood. To gain insight into the mechanism by which eptifibatide-dependent antibodies initiate platelet clearance, we incubated normal human platelets with patient serum containing an αIIbβ3-specific, eptifibatide-dependent antibody. We observed that in the presence of eptifibatide, patient IgG induced platelet secretion and aggregation as well as tyrosine phosphorylation of the integrin β3 cytoplasmic domain, the platelet FcγRIIa Fc receptor, the protein-tyrosine kinase Syk, and phospholipase Cγ2. Each activation event was inhibited by preincubation of the platelets with Fab fragments of the FcγRIIa-specific mAb IV.3 or with the Src family kinase inhibitor PP2. Patient serum plus eptifibatide did not, however, activate platelets from a patient with a variant form of Glanzmann thrombasthenia that expressed normal levels of FcγRIIa and the αIIbβ3 complex but lacked most of the β3 cytoplasmic domain. Taken together, these data suggest a novel mechanism whereby eptifibatide-dependent antibodies engage the integrin β3 subunit such that FcγRIIa and its downstream signaling components become activated, resulting in thrombocytopenia and a predisposition to thrombosis.

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Section: Discussionmentioning

confidence: 99%

Eptifibatide-induced thrombocytopenia and thrombosis in humans require FcγRIIa and the integrin β3 cytoplasmic domain

Gao¹,

Boylan²,

Bougie³

et al. 2009

J. Clin. Invest.

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“…Monoclonal Antibodies-Monoclonal antibodies to GPIb-IX (AK2), ␣2␤1 (AK7), and CD36 (IE8) have been described previously (33,34); anti-␣v␤3 (AP-3) and anti-CD4 (OKT-4) were obtained from the American Type Culture Collection; and the anti-integrin-associated protein monoclonal antibody B6H12 (26) was a kind gift of Dr. Eric J. Brown (Washington University School of Medicine, St. Louis, MO).…”

Section: Methodsmentioning

confidence: 99%

Stimulation of Platelet Activation and Aggregation by a Carboxyl-terminal Peptide from Thrombospondin Binding to the Integrin-associated Protein Receptor

Dorahy

Thorne

Fecondo

et al. 1997

Journal of Biological Chemistry

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Thrombospondin, a major secretory product of the ␣-granules of activated platelets, is a large trimeric glycoprotein that plays an important role in platelet aggregation. On resting platelets, thrombospondin binds to a single receptor in a cation-independent manner, but upon platelet activation it binds at least two further, distinct receptors that are both dependent upon divalent cations. Each of these receptors on the platelet surface binds to different regions of the thrombospondin molecule, and such binding may be responsible for the multifunctional role of thrombospondin in aggregation. We show here that a peptide from the carboxyl terminus of thrombospondin, RFYVVMWK, directly and specifically induces the activation and aggregation of washed human platelets from different donors at concentrations of 5-25 M. At lower concentrations the peptide synergizes with suboptimal concentrations of ADP to induce aggregation. Peptide affinity chromatography and immunoprecipitation with a monoclonal antibody were used to identify the receptor for the carboxyl-terminal peptide as the integrin-associated protein. The integrinassociated protein remained bound to the RFYVVMWKcontaining peptide column when washed with a scrambled peptide in the presence of 5 mM EDTA, indicating a divalent cation-independent association. It is suggested that integrin-associated protein is the primary receptor for thrombospondin on the surface of resting platelets and is implicated in potentiating the platelet aggregation response.

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“…Thus, although the induction of aggregation by mAbs still required Fc-FcgRII interaction, the triggering of FcgRII signal alone by crosslinked Fab 2 fragments of IV.3 mAb gave only a weak response, whereas the aggregation response to LeoA1 and SYB-1 was much stronger and more persistent. Since FcgRII expression is increased following platelet activation (from a range of 1000-2000 receptors/platelet on resting platelets to values >2000 receptors/platelet on activated cells (McCrae et al, 1990)), any change in antigen density as a result of platelet degranulation (Berndt et al, 1993) is very unlikely to account for the observed weak response of degranulated platelets to FcgRII engagement as compared with their much stronger and apparently equal responses to both SYB-1 and LeoA1. Resting platelets express 1200 and 35 000-65 000 molecules/cell of PTA-1 (Scott et al, 1989) and CD9 (Hato et al, 1988) respectively.…”

Section: Discussionmentioning

confidence: 99%

analysis of CD9, CD32 and p67 signalling: use of degranulated platelets indicates direct involvement of CD9 and p67 in integrin activation

et al. 1997

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Summary. The use of agonist monoclonal antibodies (mAbs) to probe the signalling function of platelet membrane proteins is severely limited by the dependence of the mAb effect on Fc-FcgRII interaction. Furthermore, in addition to its anchoring role, the FcgRII receptor itself generates a stimulation signal resulting in granule secretion. Platelet stimulation by the released granule contents can then further obscure the original activation signal. Here we demonstrate that these problems are largely overcome by the use of platelets which had been degranulated with thrombin prior to stimulation with mAbs. We found that, like intact cells, degranulated platelets could also be activated and induced to aggregate by mAbs against a 67 kD membrane protein (known as PTA1) and CD9, and by crosslinked CD32 (FcgRII). However, the signal generated by crosslinked FcgRII was weak compared with that induced by the other monoclonal antibodies. Thus, by diminishing the FcgRII signal contribution, we have succeeded for the first time to clearly dissect the target antigen signal from that generated by FcgRII. In addition to differences in the degree of aggregation, analysis of the signals generated by each mAb showed differences in Ca 2+ fluxes and protein phosphorylation. Moreover, the signals generated by CD9 and PTA1 antigens differed significantly in their sensitivity to PKC inhibition or ADP-ribosylation of the small GTP-binding protein rhoA. Despite these differences, the signals initiated by all three antigens converged to a common signalling pathway which included activation of tyrosine kinase(s). The pattern of protein phosphorylation strongly resembled that induced by gpIIb/IIIa-mediated platelet interaction with macromolecular ligands and by mutual cell contact. The multiple intercellular links formed by mAb would have a similar effect since the Fc-receptor anchorage required for antigen stimulation is already known to be provided by adjacent cells. The present findings suggest that the function of both CD9 and PTA1 antigens is closely associated with gpIIb/IIIa activation.

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Topographical Association of the Platelet Fc-receptor with the Glycoprotein IIb-IIIa Complex

Cited by 16 publications

References 29 publications

Eptifibatide-induced thrombocytopenia and thrombosis in humans require FcγRIIa and the integrin β3 cytoplasmic domain

Eptifibatide-induced thrombocytopenia and thrombosis in humans require FcγRIIa and the integrin β3 cytoplasmic domain

Stimulation of Platelet Activation and Aggregation by a Carboxyl-terminal Peptide from Thrombospondin Binding to the Integrin-associated Protein Receptor

analysis of CD9, CD32 and p67 signalling: use of degranulated platelets indicates direct involvement of CD9 and p67 in integrin activation

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