Dissociation of Bimolecular αIIbβ3-Fibrinogen Complex under a Constant Tensile Force

Litvinov, Rustem I.; Barsegov, Valeri; Schissler, Andrew J; Fisher, Andrew R.; Bennett, Joel S.; Weisel, John W.; Shuman, Henry

doi:10.1016/j.bpj.2010.11.019

Cited by 62 publications

(65 citation statements)

References 49 publications

(60 reference statements)

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“…Another important parameter of a binding interaction is the transition state distance ( ), which can be interpreted as the distance of molecular separation at which the bond fails. Of note, the transition state distance for the KKO-PF4 and RTO-PF4 unbinding was ϳ0.55-0.6 nm, which is relatively long compared with brittle bonds, such as the A:a knob-hole bonds in fibrin (19) or the platelet integrin ␣IIb␤3-fibrinogen complexes (35). This parameter may result from the larger size and multimeric nature of the PF4-Ab complexes and reflect their elongation and/or other mechanically induced structural transitions preceding forced dissociation from the binding sites.…”

Section: Discussionmentioning

confidence: 99%

Distinct Specificity and Single-molecule Kinetics Characterize the Interaction of Pathogenic and Non-pathogenic Antibodies against Platelet Factor 4-Heparin Complexes with Platelet Factor 4

Litvinov¹,

Yarovoi

Rauova

et al. 2013

Journal of Biological Chemistry

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Background: Heparin-treated patients often develop antibodies, but only a subset cause heparin-induced thrombocytopenia. Results: In a single-molecule assay, a pathogenic monoclonal antibody bound more strongly to cross-linked platelet factor 4 than a non-pathogenic antibody. Conclusion: Oligomerization of platelet factor 4 may enhance binding of pathogenic antibodies. Significance: A molecular basis for specificity of pathogenic antibodies in heparin-induced thrombocytopenia is provided.

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Section: Discussionmentioning

confidence: 99%

Distinct Specificity and Single-molecule Kinetics Characterize the Interaction of Pathogenic and Non-pathogenic Antibodies against Platelet Factor 4-Heparin Complexes with Platelet Factor 4

Litvinov¹,

Yarovoi

Rauova

et al. 2013

Journal of Biological Chemistry

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“…a bond that strengthens when force is applied; see Box 2) in which maximum lifetimes occur at forces of 10-30 pN (Kong et al, 2009). Such catch bond behavior has not been observed for aIIb3 (Litvinov et al, 2011) or avb3 integrin. This could explain the much higher resistance to force of fibronectin-a5b1-integrin bonds compared with those of fibronectin-avb3-integrin bonds although the latter are required for force sensing.…”

Section: Molecular Motorsmentioning

confidence: 98%

Finding the weakest link – exploring integrin-mediated mechanical molecular pathways

Roca‐Cusachs

Iskratsch

Sheetz

2012

Journal of Cell Science

227

222

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SummaryFrom the extracellular matrix to the cytoskeleton, a network of molecular links connects cells to their environment. Molecules in this network transmit and detect mechanical forces, which subsequently determine cell behavior and fate. Here, we reconstruct the mechanical pathway followed by these forces. From matrix proteins to actin through integrins and adaptor proteins, we review how forces affect the lifetime of bonds and stretch or alter the conformation of proteins, and how these mechanical changes are converted into biochemical signals in mechanotransduction events. We evaluate which of the proteins in the network can participate in mechanotransduction and which are simply responsible for transmitting forces in a dynamic network. Besides their individual properties, we also analyze how the mechanical responses of a protein are determined by their serial connections from the matrix to actin, their parallel connections in integrin clusters and by the rate at which force is applied to them. All these define mechanical molecular pathways in cells, which are emerging as key regulators of cell function alongside better studied biochemical pathways.

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“…From many previous experiments with other proteins, [30][31][32][33][34] we know that the immobilization protocol is robust and highly reproducible in terms of surface density and reactivity of proteins. To maximize single-molecule interactions while decreasing the likelihood of multiple interactions, the surface densities of reacting proteins were deliberately decreased so that the fraction of specific interactions between antibody and PF4 was ϳ 10% of bead-pedestal contacts or less (see supplemental Methods for details).…”

Section: Binding Of Kko and Rto To Pf4: Optical Trap-based Force Specmentioning

confidence: 99%

Dynamic antibody-binding properties in the pathogenesis of HIT

Sachais¹,

Litvinov

Yarovoi³

et al. 2012

Blood

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Rapid laboratory assessment of heparininduced thrombocytopenia (HIT) is important for disease recognition and management. The utility of contemporary immunoassays to detect antiplatelet factor 4 (PF4)/heparin antibodies is hindered by detection of antibodies unassociated with disease. To begin to distinguish properties of pathogenic anti-PF4/heparin antibodies, we compared isotype-matched monoclonal antibodies that bind to different epitopes: KKO causes thrombocytopenia in an in vivo model of HIT, whereas RTO does not. KKO binding to PF4 and heparin is specifically inhibited by human HIT antibodies that activate platelets, whereas inhibition of RTO binding is not differentially affected. Heparin increased the avidity of KKO binding to PF4 without affecting RTO, but it did not increase total binding or binding to nontetrameric PF4 K50E . Single-molecule forced unbinding demonstrated KKO was 8-fold more reactive toward PF4 tetramers and formed stronger complexes than RTO, but not to PF4 K50E dimers. KKO, but not RTO, promoted oligomerization of PF4 but not PF4 K50E . This study reveals differences in the properties of anti-PF4 antibodies that cause thrombocytopenia not revealed by ELISA that correlate with oligomerization of PF4 and sustained high-avidity interactions that may simulate transient antibody-antigen interactions in vivo. These differences suggest the potential importance of epitope specificity in the pathogenesis of HIT. (Blood. 2012;120(5): 1137-1142) IntroductionHeparin-induced thrombocytopenia (HIT) is a thrombotic complication of heparin therapy mediated by antibodies to complexes between platelet factor 4 (PF4) and heparin or glycosaminoglycans (GAGs). [1][2][3] However, antibodies to PF4/heparin are detected by ELISA far more frequently than antibodies that activate platelets or than clinical disease. [4][5][6] For example, anti-PF4/heparin antibodies are detected in 25% to 60% of patients who receive unfractionated heparin after cardiopulmonary bypass surgery and a high proportion of hospitalized patients in other medical settings, 4,7-9 an incidence that far exceeds the prevalence of HIT. 1,10 The reason why only a fraction of patients with anti-PF4 antibodies detected by ELISA develop HIT is unclear and is only partially explained by antibody titer and IgG isotype. 5,9,[11][12][13][14] One clue to the differences in the pathogenic potential of anti-PF4/heparin antibodies may begin with the finding that heparin and PF4 form complexes of diverse size that depend on the molar ratio of the reactants. [15][16][17] HIT antibodies and the HIT-like monoclonal antibody KKO bind and activate platelets and monocytes and promote thrombosis in an animal model over a narrow molar ratio of reactants. 18,19 At these molar ratios, ultralarge complexes (ULCs) form in solution between heparin and multiple PF4 tetramers capable of binding multiple antibody molecules 16 that in the case of platelets may lead to sustained engagement of FcR␥IIA, which initiates aggregation. [20][21][22] Molecular replacement stud...

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Dissociation of Bimolecular αIIbβ3-Fibrinogen Complex under a Constant Tensile Force

Cited by 62 publications

References 49 publications

Distinct Specificity and Single-molecule Kinetics Characterize the Interaction of Pathogenic and Non-pathogenic Antibodies against Platelet Factor 4-Heparin Complexes with Platelet Factor 4

Distinct Specificity and Single-molecule Kinetics Characterize the Interaction of Pathogenic and Non-pathogenic Antibodies against Platelet Factor 4-Heparin Complexes with Platelet Factor 4

Finding the weakest link – exploring integrin-mediated mechanical molecular pathways

Dynamic antibody-binding properties in the pathogenesis of HIT

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