Dataset Information

The human platelet antigen-1b (Pro33) variant of ?IIb?3 allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state.

ABSTRACT: Integrins are heterodimeric cell-adhesion receptors comprising ? and ? subunits that transmit signals allosterically in both directions across the membrane by binding to intra- and extracellular components. The human platelet antigen-1 (HPA-1) polymorphism in ?IIb?3 arises from a Leu ? Pro exchange at residue 33 in the genu of the ?3 subunit, resulting in Leu33 (HPA-1a) or Pro33 (HPA-1b) isoforms. Although clinical investigations have provided conflicting results, some studies have suggested that Pro33 platelets exhibit increased thrombogenicity. Under flow-dynamic conditions, the Pro33 variant displays prothrombotic properties, characterized by increased platelet adhesion, aggregate/thrombus formation, and outside-in signaling. However, the molecular events underlying this prothrombotic phenotype have remained elusive. As residue 33 is located >80 Å away from extracellular binding sites or transmembrane domains, we hypothesized that the Leu ? Pro exchange allosterically shifts the dynamic conformational equilibrium of ?IIb?3 toward an active state. Multiple microsecond-long, all-atom molecular dynamics simulations of the ectodomain of the Leu33 and Pro33 isoforms provided evidence that the Leu ? Pro exchange weakens interdomain interactions at the genu and alters the structural dynamics of the integrin to a more unbent and splayed state. Using FRET analysis of fluorescent proteins fused with ?IIb?3 in transfected HEK293 cells, we found that the Pro33 variant in its resting state displays a lower energy transfer than the Leu33 isoform. This finding indicated a larger spatial separation of the cytoplasmic tails in the Pro33 variant. Together, our results indicate that the Leu ? Pro exchange allosterically shifts the dynamic conformational equilibrium of ?IIb?3 to a structural state closer to the active one, promoting the fully active state and fostering the prothrombotic phenotype of Pro33 platelets.

SUBMITTER: Pagani G

PROVIDER: S-EPMC5880125 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The human platelet antigen-1b (Pro33) variant of αIIbβ3 allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state.

Pagani Giulia G Pereira Joana P V JPV Stoldt Volker R VR Beck Andreas A Scharf Rüdiger E RE Gohlke Holger H

The Journal of biological chemistry 20180209 13

Integrins are heterodimeric cell-adhesion receptors comprising α and β subunits that transmit signals allosterically in both directions across the membrane by binding to intra- and extracellular components. The human platelet antigen-1 (HPA-1) polymorphism in αIIbβ3 arises from a Leu → Pro exchange at residue 33 in the genu of the β3 subunit, resulting in Leu33 (HPA-1a) or Pro33 (HPA-1b) isoforms. Although clinical investigations have provid ...[more]

PMID: 29462793

Similar Datasets

Project description:BackgroundThe prevalence of cardiovascular diseases (CVDs) is increasing at a high rate, and the available treatment options, sometimes, have complications which necessitates the need to develop safer and efficacious approaches. Ethnomedicinal applications reportedly reduce CVD risk. Ulmus parvifolia Jacq. (Ulmaceae) commonly known as Chinese Elm or Lacebark Elm, is native to China, Japan, and Korea. It exhibits anti-inflammatory, antiviral, and anticancer properties, but its anti-platelet properties have not yet been elucidated.PurposeTo investigate the pharmacological anti-platelet and anti-thrombotic effects of U. parvifolia bark extract.Study design and methodsHuman and rat washed platelets were prepared; light transmission aggregometry and scanning electron microscopy was performed to assess platelet aggregation and the change in platelet shape, respectively. Intracellular calcium mobilization, ATP release, and thromboxane-B2 production were also measured. Integrin αIIbβ3 activation was analyzed in terms of fibrinogen binding, fibronectin adhesion, and clot retraction. The expression of MAPK, Src, and PI3K/Akt pathway proteins was examined. Cyclic nucleotide signaling pathway was evaluated via cAMP elevation and VASP phosphorylation. Anti-thrombotic activity of the extract was evaluated in vivo using an arteriovenous shunt rat model, whereas its effect on hemostasis in mice was assessed via bleeding time assay.ResultsU. parvifolia extract significantly inhibited human and rat platelet aggregation in a dose-dependent manner along with inhibition of calcium mobilization, dense granule secretion, and TxB2 production. Integrin αIIbβ3 mediated inside-out and outside-in signaling events, as evidenced by the inhibition of fibrinogen binding, fibronectin adhesion, and clot retraction. The extract significantly reduced phosphorylation of Src, MAPK (ERK, JNK, and p38MAPK), and PI3K/Akt pathway proteins. Cyclic-AMP levels were elevated in U. parvifolia-treated platelets, while PKAαβγ and VASPser157 phosphorylation was enhanced. U. parvifolia reduced thrombus weight in rats and moderately increased bleeding time in mice.ConclusionU. parvifolia modulates platelet responses and inhibit thrombus formation by regulating integrin αIIbβ3 mediated inside-out and outside-in signaling events and cAMP signaling pathway.

Dataset Information

The human platelet antigen-1b (Pro33) variant of ?IIb?3 allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state.

Publications

The human platelet antigen-1b (Pro<sup>33</sup>) variant of α<sub>IIb</sub>β<sub>3</sub> allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets