Cryo-EM structures of full-length integrin αIIbβ3 in native lipids

Area of Science:

• Biochemistry
• Structural Biology
• Cell Biology

Background:

• Platelet integrin αIIbβ3 mediates thrombosis and hemostasis.
• αIIbβ3 activation involves conformational changes and bidirectional signaling.
• Current anti-αIIbβ3 drugs can impair hemostatic function.

Purpose of the Study:

• To determine the near-atomic resolution cryo-EM structures of full-length αIIbβ3.
• To elucidate the structural basis of αIIbβ3 activation and inhibition by eptifibatide.

Main Methods:

• Cryo-electron microscopy (cryo-EM) of full-length αIIbβ3.
• Analysis of apo and eptifibatide-bound states in native cell-membrane nanoparticles.

Main Results:

• The apo integrin adopts a bent inactive state with separated transmembrane helices.
• The ligand-binding site is accessible in the apo state, challenging previous models.
• Eptifibatide binding induces dramatic conformational changes in αIIbβ3.

Conclusions:

• Structural insights into the inactive and drug-bound states of αIIbβ3.
• Findings challenge existing models of ligand-binding site accessibility.
• Results may inform the development of safer anti-platelet therapeutics.