Dynamic measurements of the platelet membrane glycoprotein IIb-IIIa receptor for fibrinogen by flow cytometry. I. Methodology, theory and results for two distinct activators

Frojmovic, Mony M.; Wong, Truman; Ven, Theo van de

doi:10.1016/s0006-3495(91)82294-9

Cited by 60 publications

(47 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To assess the activation state of ␣IIb␤3 more precisely, we performed initial velocity analysis at a specific time point. The kinetic approach with the use of flow cytometry has been proposed for assessing the dynamics of ␣IIb␤3 activation, 36 and we have modified it as the initial velocity analysis for assessing reversible ␣IIb␤3 activation. On-rate of PAC-1 binding reflects the number of activated receptors, and the initial velocity analysis showed that PAR1 stimulation induced only transient activation.…”

Section: Discussionmentioning

confidence: 99%

A potential role for α-actinin in inside-out αIIbβ3 signaling

Tadokoro

Nakazawa

Kamae

et al. 2011

Blood

View full text Add to dashboard Cite

Many different biochemical signaling pathways regulate integrin activation through the integrin cytoplasmic tail. Here, we describe a new role for ␣-actinin in inside-out integrin activation. In resting human platelets, ␣-actinin was associated with ␣IIb␤3, whereas inside-out signaling (␣IIb␤3 activation signals) from protease-activated receptors (PARs) dephosphorylated and dissociated ␣-actinin from ␣IIb␤3. We evaluated the time-dependent changes of the ␣IIb␤3 activation state by measuring PAC-1 binding velocity. The initial velocity analysis clearly showed that PAR1-activating peptide stimulation induced only transient ␣IIb␤3 activation, whereas PAR4-activating peptide induced long-lasting ␣IIb␤3 activation. When ␣IIb␤3 activation signaling dwindled, ␣-actinin became rephosphorylated and reassociated with ␣IIb␤3. Compared with control platelets, the dissociation of ␣-actinin from ␣IIb␤3 was only transient in PAR4-stimulated P2Y 12 -deficient platelets in which the sustained ␣IIb␤3 activation was markedly impaired. Overexpression of wild-type ␣-actinin, but not the mutant Y12F ␣-actinin, increased its binding to ␣IIb␤3 and inhibited PAR1-induced initial ␣IIb␤3 activation in the human megakaryoblastic cell line, CMK. In contrast, knockdown of ␣-actinin augmented PAR-induced ␣IIb␤3 activation in CMK. These observations suggest that ␣-actinin might play a potential role in setting integrins to a default low-affinity ligand-binding state in resting platelets and regulating ␣IIb␤3 activation by inside-out signaling. (Blood. 2011;117(1):250-258) IntroductionIntegrins and their ligands play key roles in development, immune responses, leukocyte traffic, hemostasis, and cancer and are at the core of numerous human diseases. 1 Many integrins are expressed with their extracellular domains in a default low-affinity ligandbinding state. The main platelet integrin, ␣IIb␤3, also known as GPIIb/IIIa, is present at a high density on circulating platelets. It is inactive on circulating platelets; if it were not, platelets would bind their main ligand, fibrinogen, from the plasma and aggregate, leading to thrombosis. This inactivation is important for the biologic function of integrins, as is most evident from assessments of their status on circulating blood cells. However, the molecular mechanisms of their being set to an inactive, low-affinity state remain unknown.High-affinity ligand binding requires activation of integrins through conformational changes regulated by inside-out signaling. 2 Integrin cytoplasmic domains play a pivotal role in integrin signaling because the cytoplasmic tails of the integrin ␣ and ␤ subunits are directly accessible to the intracellular signaling apparatus, namely the integrin activation complex (IAC). 3 Moreover, ligand binding to the integrin induces outside-in signaling that leads to integrin clustering and subsequent recruitment of actin filaments to the integrin cytoplasmic domain. From the perspective that this recruitment occurs by a complex of interacting cytoskeletal proteins, many studie...

show abstract

Section: Discussionmentioning

confidence: 99%

A potential role for α-actinin in inside-out αIIbβ3 signaling

Tadokoro

Nakazawa

Kamae

et al. 2011

Blood

View full text Add to dashboard Cite

show abstract

“…The membrane-bound complexes GpIb and GpIIbIIIa play an important role in this process (Frojmovic, 1998;Ruggeri et al, 1999). The extension of long pseudopods, usually after a time lag (Frojmovic et al, 1991;, facilitates aggregation, by increasing the probability of collisions with other platelets and by increased membrane fluidity. The shape change, followed by binding of macromolecules, leads to enhanced 'stickiness' thus promoting clot formation.…”

Section: Platelet Activation Adhesion and Aggregationmentioning

confidence: 99%

A Model Incorporating Some of the Mechanical and Biochemical Factors Underlying Clot Formation and Dissolution in Flowing Blood

Mohan

Rajagopal

2003

Journal of Theoretical Medicine

136

120

View full text Add to dashboard Cite

Multiple interacting mechanisms control the formation and dissolution of clots to maintain blood in a state of delicate balance. In addition to a myriad of biochemical reactions, rheological factors also play a crucial role in modulating the response of blood to external stimuli. To date, a comprehensive model for clot formation and dissolution, that takes into account the biochemical, medical and rheological factors, has not been put into place, the existing models emphasizing either one or the other of the factors. In this paper, after discussing the various biochemical, physiologic and rheological factors at some length, we develop a model for clot formation and dissolution that incorporates many of the relevant crucial factors that have a bearing on the problem. The model, though just a first step towards understanding a complex phenomenon, goes further than previous models in integrating the biochemical, physiologic and rheological factors that come into play.

show abstract

“…For the decreases in PtdInsP, and PtdInsP to be dependent on fibrinogen binding to GPIIbDIIa, the binding must occur before the inositol phospholipid changes take place. Substantial aggregation [32, 331, fibrinogen receptor activation [34] and fibrinogen binding [17] have been reported to occur within the first 1-10 s after platelet stimulation by ADP, satisfying this requirement.…”

Section: Discussionmentioning

confidence: 99%

ADP‐stimulated fibrinogen binding is necessary for some of the inositol phospholipid changes found in ADP‐stimulated platelets

Vickers

1993

European Journal of Biochemistry

View full text Add to dashboard Cite

ADP-stimulation of washed human platelets suspended in Tyrode/albumin solution containing Ca' + (2 mM) and fibrinogen (0.4 mg/ml) causes extensive, reversible aggregation without appreciable secretion of granule contents. Under these conditions ADP (10 pM) stimulation decreased the amounts of phosphatidylinositol 4,5-bisphosphate (PtdInsP,) and phosphatidylinositol 4-phosphate (PtdInsP) at 10 s. Omitting fibrinogen from the suspending medium or blocking fibrinogen binding to the platelets using Arg-Gly-Asp-Ser (RGDS, 0.23 mM) inhibited these decreases in PtdInsP, and PtdinsP. in contrast, ADP-induced decreases in PtdInsP, and increases in PtdInsP at 60 s compared to 10 s were not affected by RGDS or the absence of fibrinogen. in platelets prelabelled with [3H]glycerol and ['2P]phosphate, changes in labelling of the inositol phospholipids paralleled the changes in amount. The ADP-induced changes in phosphatidic acid (PtdOH) at 10 s were unaffected by RGDS; this finding supported previous reports that phospholipase C was not the cause of the early decreases in PtdInsP, and PtdinsP. These results indicate that the early decreases in PtdInsP, and PtdInsP at 10 s are dependent on fibrinogen binding to the platelets and occur after fibrinogen binding which is activated by ADP stimulation. It is proposed that the fibrinogen-dependent changes in PtdInsP, and PtdInsP inay have a feedback role augmenting platelet aggregation or other responses of platelets that might occur after fibrinogen binding, possibly due to effects on actin polymerisation.The receptor for fibrinogen on platelets, the glycoprotein IIbAIIa complex (integrin al&, [l]), has been shown to undergo conformational change in activated platelets to expose the fibrinogen binding site [2-41. In addition, evidence is now accumulating that the binding of fibrinogen to the glycoprotein IIb/IIIa complex (GPIIbDIIa) may cause changes in the complex which affect internal processes in the platelet. An early report to this effect by Isenberg et al. [ 5 ] showed that clustering of GPIIb/IIIa complexes in ADP-stimulated platelets required binding of fibrinogen and did not involve cross-linking by fibrinogen. In a subsequent study, Isenberg et al.[6] demonstrated stimulation of actinomysin-dependent clustering of GPIIb/IIIa in the surface-connected canalicular system of otherwise unstimulated platelets caused by addition of antibodies to GPIIb (Tab) and GPIIIa (AP3). There have been other reports in which monoclonal antibodies to GPIIbAIIa have been shown to cause platelet aggregation [7-91. Since in these cases aggregation was shown to be fibrinogen-dependent, aggregation is not due to platelet cross-linking by the antibodies and demonstration that aggregation was inhibitable by agents (such as prostaglandin E,) which block internal signal transduction pathways indicated that the confornational change in fibrinogen receptors was not only directly induced by antibody binding to GPIIb

show abstract

Dynamic measurements of the platelet membrane glycoprotein IIb-IIIa receptor for fibrinogen by flow cytometry. I. Methodology, theory and results for two distinct activators

Cited by 60 publications

References 24 publications

A potential role for α-actinin in inside-out αIIbβ3 signaling

A potential role for α-actinin in inside-out αIIbβ3 signaling

A Model Incorporating Some of the Mechanical and Biochemical Factors Underlying Clot Formation and Dissolution in Flowing Blood

ADP‐stimulated fibrinogen binding is necessary for some of the inositol phospholipid changes found in ADP‐stimulated platelets

Contact Info

Product

Resources

About