Dataset Information

Structure-guided design of a high-affinity platelet integrin ?IIb?3 receptor antagonist that disrupts Mg²? binding to the MIDAS.

ABSTRACT: An integrin found on platelets, ?(IIb)?(3) mediates platelet aggregation, and ?(IIb)?(3) antagonists are effective antithrombotic agents in the clinic. Ligands bind to integrins in part by coordinating a magnesium ion (Mg(2+)) located in the ? subunit metal ion-dependent adhesion site (MIDAS). Drugs patterned on the integrin ligand sequence Arg-Gly-Asp have a basic moiety that binds the ?(IIb) subunit and a carboxyl group that coordinates the MIDAS Mg(2+) in the ?(3) subunits. They induce conformational changes in the ?(3) subunit that may have negative consequences such as exposing previously hidden epitopes and inducing the active conformation of the receptor. We recently reported an inhibitor of ?(IIb)?(3) (RUC-1) that binds exclusively to the ?(IIb) subunit; here, we report the structure-based design and synthesis of RUC-2, a RUC-1 derivative with a ~100-fold higher affinity. RUC-2 does not induce major conformational changes in ?(3) as judged by monoclonal antibody binding, light scattering, gel chromatography, electron microscopy, and a receptor priming assay. X-ray crystallography of the RUC-2-?(IIb)?(3) headpiece complex in 1 mM calcium ion (Ca(2+))/5 mM Mg(2+) at 2.6 Å revealed that RUC-2 binds to ?(IIb) the way RUC-1 does, but in addition, it binds to the ?(3) MIDAS residue glutamic acid 220, thus displacing Mg(2+) from the MIDAS. When the Mg(2+) concentration was increased to 20 mM, however, Mg(2+) was identified in the MIDAS and RUC-2 was absent. RUC-2's ability to inhibit ligand binding and platelet aggregation was diminished by increasing the Mg(2+) concentration. Thus, RUC-2 inhibits ligand binding by a mechanism different from that of all other ?(IIb)?(3) antagonists and may offer advantages as a therapeutic agent.

SUBMITTER: Zhu J

PROVIDER: S-EPMC3390238 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Structure-guided design of a high-affinity platelet integrin αIIbβ3 receptor antagonist that disrupts Mg²⁺ binding to the MIDAS.

Zhu Jieqing J Choi Won-Seok WS McCoy Joshua G JG Negri Ana A Zhu Jianghai J Naini Sarasija S Li Jihong J Shen Min M Huang Wenwei W Bougie Daniel D Rasmussen Mark M Aster Richard R Thomas Craig J CJ Filizola Marta M Springer Timothy A TA Coller Barry S BS

Science translational medicine 20120301 125

An integrin found on platelets, α(IIb)β(3) mediates platelet aggregation, and α(IIb)β(3) antagonists are effective antithrombotic agents in the clinic. Ligands bind to integrins in part by coordinating a magnesium ion (Mg(2+)) located in the β subunit metal ion-dependent adhesion site (MIDAS). Drugs patterned on the integrin ligand sequence Arg-Gly-Asp have a basic moiety that binds the α(IIb) subunit and a carboxyl group that coordinates the MIDAS Mg(2+) in the β(3) subunits. They induce confor ...[more]

PMID: 22422993

Similar Datasets

Project description:Essentials peroxisome proliferator-activated receptor γ (PPARγ) agonists inhibit platelet function. PPARγ agonists negatively regulate outside-in signaling via integrin αIIbβ3. PPARγ agonists disrupt the interaction of Gα13 with integrin β3. This is attributed to an upregulation of protein kinase A activity.SummaryBackground Agonists for the peroxisome proliferator-activated receptor (PPARγ) have been shown to have inhibitory effects on platelet activity following stimulation by GPVI and GPCR agonists. Objectives Profound effects on thrombus formation led us to suspect a role for PPARγ agonists in the regulation of integrin αIIbβ3 mediated signaling. Both GPVI and GPCR signaling pathways lead to αIIbβ3 activation, and signaling through αIIbβ3 plays a critical role in platelet function and normal hemostasis. Methods The effects of PPARγ agonists on the regulation of αIIbβ3 outside-in signaling was determined by monitoring the ability of platelets to adhere and spread on fibrinogen and undergo clot retraction. Effects on signaling components downstream of αIIbβ3 activation were also determined following adhesion to fibrinogen by Western blotting. Results Treatment of platelets with PPARγ agonists inhibited platelet adhesion and spreading on fibrinogen and diminished clot retraction. A reduction in phosphorylation of several components of αIIbβ3 signaling, including the integrin β3 subunit, Syk, PLCγ2, focal adhesion kinase (FAK) and Akt, was also observed as a result of reduced interaction of the integrin β3 subunit with Gα13. Studies of VASP phosphorylation revealed that this was because of an increase in PKA activity following treatment with PPARγ receptor agonists. Conclusions This study provides further evidence for antiplatelet actions of PPARγ agonists, identifies a negative regulatory role for PPARγ agonists in the control of integrin αIIbβ3 outside-in signaling, and provides a molecular basis by which the PPARγ agonists negatively regulate platelet activation and thrombus formation.

Dataset Information

Structure-guided design of a high-affinity platelet integrin ?IIb?3 receptor antagonist that disrupts Mg²? binding to the MIDAS.

Publications

Structure-guided design of a high-affinity platelet integrin αIIbβ3 receptor antagonist that disrupts Mg²⁺ binding to the MIDAS.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets