MK-383 (Tirofiban) induces a GPIIb/IIIa receptor conformation which differs from the resting and activated receptor

Barlage, Stefan; Wimmer, Antonia; Pfeiffer, Alexandra; Rothe, Gregor; Schmitz, Gerd

doi:10.1080/09533710022149377

Cited by 8 publications

(7 citation statements)

References 18 publications

(22 reference statements)

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“…Also, a study by Barlage et al. [37] indicated that tirofiban induced a α IIb β 3 conformer that was different from both the inactive and activated integrin. It is possible that a ‘priming’ event has occurred in our studies during pre‐incubation of platelets with α IIb β 3 antagonists and this maybe responsible for the observed potentiation of Src and Syk kinases.…”

Section: Discussionmentioning

confidence: 99%

RGD‐ligand mimetic antagonists of integrin αIIbβ3 paradoxically enhance GPVI‐induced human platelet activation

Jones

Harper

Aitken

et al. 2010

Journal of Thrombosis and Haemostasis

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To cite this article: Jones ML, Harper MT, Aitken EW, Williams CM, Poole AW. RGD-ligand mimetic antagonists of integrin a IIb b 3 paradoxically enhance GPVI-induced human platelet activation. J Thromb Haemost 2010; 8: 567-76.Summary. Background: The integrin a IIb b 3 is the major mediator of platelet aggregation and has, therefore, become an important target of antithrombotic therapy. Antagonists of a IIb b 3 , for example abciximab, tirofiban and eptifibatide, are used in the treatment of acute coronary syndromes. However, in addition to effective blockade of the integrin, binding of can induce conformational changes in the integrin and can also induce integrin clustering. This class effect of RGD-ligand mimetics might, therefore, underlie paradoxical platelet activation and thrombosis previously reported. Objectives: To examine the components of signaling pathways and functional responses in platelets that may underlie this phenomenon of paradoxical platelet activation. Methods:We assessed the effect of lotrafiban, and other a IIb b 3 antagonists including the clinically used drug tirofiban, on tyrosine phosphorylation of key signaling proteins in platelets by immunoblotting and also platelet functional outputs such as cytosolic calcium responses, phosphatidylserine exposure (pro-coagulant activity) and dense granule release. Results: In all cases, no effect of a IIb b 3 antagonists were observed on their own, but these integrin antagonists did lead to a marked potentiation of glycoprotein VI (GPVI)-associated FcR c-chain phosphorylation, activation of Src family kinases and Syk kinase. This correlated with increased dense granule secretion, cytosolic calcium response and exposure of phosphatidylserine on the platelet surface. P2Y 12 antagonism abolished the potentiated phosphatidylserine exposure and dense granule secretion but not the cytosolic calcium response. Conclusions: These data provide a mechanism for enhancement of platelet activity by a IIb b 3 inhibitors, but also reveal a potentially important signaling pathway operating from the integrin to GPVI signaling.

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Section: Discussionmentioning

confidence: 99%

RGD‐ligand mimetic antagonists of integrin αIIbβ3 paradoxically enhance GPVI‐induced human platelet activation

Jones

Harper

Aitken

et al. 2010

Journal of Thrombosis and Haemostasis

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“…After two additional washing steps, streptavidin‐Cy5 (Jackson Immuno Research, Cambridgeshire, UK) was added and samples were incubated for 5 min, followed by another two washing steps and addition of 1 ml PBS prior to analysis. As a control for FRET analysis, platelets were also incubated with two monoclonal antibodies (clone SZ22 and P2, Beckman‐Coulter, Krefeld, Germany) directed against different epitopes of the GPIIb/IIIa, and analysis of FRET efficacy was performed as described earlier (7, 8).…”

Section: Methodsmentioning

confidence: 99%

High density lipoprotein modulates platelet function

Barlage

Boettcher

et al. 2006

Cytometry Pt A

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Background: Platelet activation by atherogenic lipoproteins can be antagonized by high density lipoprotein (HDL), probably via interaction with the ATP-binding cassette transporter A1 (ABCA1). Methods: ABCA1 expression and its association with cholesterol rich membrane domains was analyzed by mRNA and Western blot analysis. HDL effects on platelet receptor clustering were analyzed by flow cytometric analysis of fluorescence resonance energy transfer between fluorochrome-labeled antibodies. Results: ABCA1 expression increased upon megakaryocytic differentiation of human stem cells and ABCA1 pro-

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“…Similarly, the therapeutic integrin antagonist tirofiban has been reported to induce a receptor conformation that differs from both resting and ADP-primed receptors [10]. The conformational changes reported by mAbs can be propagated to and from the cytoplasmic face of integrins, suggesting that conformational regulation is an important feature of bi-directional signalling by integrins.…”

Section: Evidence That Conformational Changes Take Place In Integrinsmentioning

confidence: 98%

Monoclonal antibodies as probes of integrin priming and activation

Humphries

2004

Biochemical Society Transactions

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Integrins are a family of heterodimeric, transmembrane receptors that mediate a range of cell-cell and cell-extracellular matrix interactions in an array of physiological and pathophysiological situations. Integrin-mediated cell adhesion is dynamically regulated in vivo to facilitate cell anchorage and movement, but prevents aberrant trafficking and aggregation. Following ligand engagement, integrin signalling imposes a spatial constraint on the assembly of signalling complexes and controls the transduction of mechanical force to the cytoskeleton. This transmembrane passage of signals via integrins is achieved both by clustering of receptors, which makes the ligand and effector engagement more favourable kinetically, and by induction of conformational changes, that theoretically creates ligand and effector binding sites de novo. Clustering and conformational changes can be triggered both from the inside of the cell (resulting in acquisition of ligand-competent conformers) and from the outside (ligand-induced signalling). In this paper, these processes will be described and distinguished by the terms priming and activation, respectively. Although both clustering and conformation are important for integrin function, the latter will be the main focus of this article; in particular, the importance of monoclonal antibodies for the study of integrin shape changes.

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MK-383 (Tirofiban) induces a GPIIb/IIIa receptor conformation which differs from the resting and activated receptor

Cited by 8 publications

References 18 publications

RGD‐ligand mimetic antagonists of integrin αIIbβ3 paradoxically enhance GPVI‐induced human platelet activation

RGD‐ligand mimetic antagonists of integrin αIIbβ3 paradoxically enhance GPVI‐induced human platelet activation

High density lipoprotein modulates platelet function

Monoclonal antibodies as probes of integrin priming and activation

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