Resolving two-dimensional kinetics of the integrin αIIbβ3-fibrinogen interactions using binding-unbinding correlation...

Area of Science:

• Biophysics
• Molecular Biology
• Cellular Biology

Background:

• Platelet aggregation and hemostasis rely on fibrinogen binding to integrin αIIbβ3.
• Understanding the kinetics of this interaction is crucial for hemostasis and thrombosis research.
• Integrin conformation and ligand binding are dynamic processes influenced by external factors.

Purpose of the Study:

• To characterize the two-dimensional kinetics of fibrinogen-integrin αIIbβ3 interactions using a novel method.
• To investigate the influence of integrin activation and force on binding kinetics and affinity.
• To provide quantitative single-molecule insights into fibrinogen-mediated platelet adhesion dynamics.

Main Methods:

• Binding-unbinding correlation spectroscopy (BUCS) combining optical trapping with force clamp measurements.
• Probing force-free association and forced dissociation of individual surface-attached fibrinogen and αIIbβ3 molecules.
• Quantifying binding probability dependence on interaction time and force.

Main Results:

• Fibrinogen-reactive αIIbβ3 exists in at least two states with distinct on-rates, off-rates, and affinities.
• The integrin activator Mn(2+) alters on-rates and affinities but not off-rates.
• Interaction strength is time-dependent, with increasing high-affinity state fraction and conformational transitions upon activation.

Conclusions:

• The study provides quantitative two-dimensional kinetic rates for αIIbβ3-fibrinogen interactions at the single-molecule level.
• Direct evidence for time- and force-dependent changes in αIIbβ3 conformation and ligand binding activity is presented.
• Findings elucidate the dynamics of fibrinogen-mediated platelet adhesion and aggregation.