Heparin modulates the conformation and signaling of platelet integrin αIIbβ3.

Introduction: The glycosaminoglycan heparin has been shown to bind to platelet integrin αIIbβ3 and induce platelet activation and aggregation, although the relationship between binding and activation is unclear. We analyzed the interaction of heparin and αIIbβ3 in detail, to obtain a better understanding of the mechanism by which heparin acts on platelets.

Methods: We assessed conformational changes in αIIbβ3 by flow cytometry of platelets exposed to unfractionated heparin.

Heparin modulates integrin-mediated cellular adhesion: specificity of interactions with alpha and beta integrin subunits.

Heparin is known to influence the growth, proliferation, and migration of vascular cells, but the precise mechanisms are unknown. We previously demonstrated that unfractionated heparin (UH) binds to the platelet integrin alpha(IIb)beta(3), and enhances ligand binding. To help define the specificity and site(s) of heparin-integrin interactions, we employed the erythroleukemic K562 cell line, transfected to express specific integrins (alpha(v)beta(3), alpha(v)beta(5), and alpha(IIb)beta(3)).

Novel vascular endothelial growth factor binding domains of fibronectin enhance vascular endothelial growth factor biological activity.

Interactions between integrins and growth factor receptors play a critical role in the development and healing of the vasculature. This study mapped two binding domains on fibronectin (FN) that modulate the activity of the angiogenic factor, vascular endothelial growth factor (VEGF). Using solid-phase assays and surface plasmon resonance analysis, we identified two novel VEGF binding domains within the N- and C-terminus of the FN molecule.