Shear-dependent tether formation during platelet translocation on von Willebrand factor

Area of Science:

• Hematology
• Biophysics
• Cell Biology

Background:

• Platelet adhesion and aggregation are crucial for vascular injury repair.
• The initial interaction involves the glycoprotein Ib/V/IX (GP Ib) receptor complex binding to von Willebrand factor (VWF).
• Under flow conditions, this interaction mediates a characteristic stop-start platelet translocation on VWF.

Purpose of the Study:

• To investigate the formation and dynamics of membrane tethers during platelet translocation on immobilized VWF.
• To determine the role of the VWF-GP Ib interaction in inducing membrane tether formation.
• To elucidate the contribution of membrane tethers to the stop-start dynamics of platelet translocation under flow.

Main Methods:

• High-resolution imaging of platelets translocating on immobilized VWF under flow.
• Perfusion experiments using blocking antibodies against integrin alpha(IIb)beta(3) and isolated VWF A1 domains.
• Analysis of shear-dependent tether elongation, frequency, and growth rates.
• Assessment of the effects of cytochalasin D and intracellular calcium chelation on tether dynamics.

Main Results:

• Platelets form dynamic membrane tethers (0.91–47.90 µm) during translocation on VWF.
• VWF-GP Ib interaction is sufficient for tether formation, independent of platelet activation.
• Tether elongation is shear-dependent, with rates and dimensions varying significantly.
• Actin polymerization and intracellular calcium influence tether growth, lifetime, and dimensions.

Conclusions:

• Membrane tether formation is a key mechanism regulating the stop-start translocation of platelets on VWF.
• This phenomenon plays a significant role in the dynamics of platelet-VWF interactions under physiological flow conditions.
• Understanding tether dynamics may offer insights into hemostasis and thrombosis.