An integrin αIIbβ3 intermediate affinity state mediates biomechanical platelet aggregation

Abstract

Integrins are membrane receptors mediating cell adhesion and mechanosensing. The structure-function relationship of integrins remains incompletely understood, despite the extensive studies due to its importance to basic cell biology and translational medicine. Using fluorescence dual biomembrane force probe, microfluidics and cone-and-plate rheometry, we applied precisely-controlled mechanical stimulations to platelets and identified an intermediate state of integrin α IIb β 3 , which is characterized by an ectodomain conformation, ligand affinity and bond lifetimes that are all intermediate between the well-known inactive and active states. This intermediate state is induced by ligand engagement of GPIbα via a mechano-signaling pathway and potentiates the outside-in mechano-signaling of α IIb β 3 for further transition to the active state during integrin mechanical affinity maturation. Our work reveals distinct α IIb β 3 state transitions in response to biomechanical and biochemical stimuli, and identifies a role for the α IIb β 3 intermediate state in promoting biomechanical platelet aggregation.

Platelets exploit fibrillar adhesions to assemble fibronectin matrix revealing new force-regulated thrombus remodeling mechanisms

“…We for the first time derive a threshold of ~1 nN per cell-substrate adhesion to activate αIIbβ3 integrins to form 3D fibrils ( Figure 4). The ECM proteins from the vessel wall and the thrombus thus essentially instruct the platelets to adopt distinct phenotypes of medium and high contractility, respectively, probably serving different functions as guided by different levels of mechanosensitive integrin signaling (Strohmeyer et al 2017;Chen et al 2019). This mechanism in platelets is, probably due to their small size and the high abundance of αIIbβ3 integrins, different from fibroblasts.…”

Quantifying single‐platelet biomechanics: An outsider’s guide to biophysical methods and recent advances

“…6 Single-cell biophysical techniques and their sensitivity have enabled quantification and unveiling of previously unknown relationships and fundamental paradigms in platelet biology and their underlying biomechanical principles with a resolution up to single-molecule level. [7][8][9][10] However, many of these single-cell techniques are still limited in their ability to scale to measure a suitably large number of individual cells and independent samples. 11 In this review, we focus on biophysical methods suitable to assess and quantify biomechanical characteristics such as elastic modulus, stiffness (or deformability), forces generated during adhesion, and spreading and contraction of single platelets in health and disease states.…”

“…Given the extent of cell‐to‐cell variations, rare subpopulations, and intrinsic fluctuations within biological systems, bulk population‐level experiments often conceal and average out vital causal relationships underlying the biological phenomena . Single‐cell biophysical techniques and their sensitivity have enabled quantification and unveiling of previously unknown relationships and fundamental paradigms in platelet biology and their underlying biomechanical principles with a resolution up to single‐molecule level . However, many of these single‐cell techniques are still limited in their ability to scale to measure a suitably large number of individual cells and independent samples .…”

Illustrated State‐of‐the‐Art Capsules of the ISTH 2019 Congress in Melbourne, Australia

“…24 Using a stenosed microfluidic model, we demonstrated that the biomechanical platelet aggregation is mainly supported by integrin αIIbβ3 with an extended-closed (EC) conformation (A). 25 We also developed a dual biomembrane force probe to visualize integrin biomechanical activation on a living platelet. 26 We found that, upon mechano-signaling of GPIb, αIIbβ3 adopts the EC conformation and possesses affinity and bond lifetime that are intermediate between the well-characterized active and resting states.…”