Mechanically Regulated Outside-In Activation of an I-Domain-Containing Integrin

Area of Science:

• Molecular biology
• Biophysics
• Cellular adhesion mechanisms

Background:

• Integrins are transmembrane proteins mediating cell adhesion and mechanotransduction via allostery.
• The precise allosteric pathway in I-domain-containing integrins is not fully understood.
• Investigating integrin αXβ2 activation is essential for understanding cellular responses.

Purpose of the Study:

• To elucidate the conformational dynamics of integrin αXβ2 during outside-in activation.
• To investigate the sequential binding of external and internal ligands and its effect on allosteric transmission.
• To clarify the internal allosteric pathways governing integrin function.

Main Methods:

• Utilized molecular dynamics simulations to model integrin αXβ2.
• Analyzed conformational changes upon binding of external and internal ligands.
• Compared the effects of different ligand binding orders on integrin activation.

Main Results:

• Internal ligand binding is a prerequisite for allosteric transmission from α- to β-subunits.
• A specific opening of the αI domain and α7-helix unfolding facilitates stable intersubunit transmission.
• Reverse ligand binding order leads to an unstable Hybrid domain swingout, hindering activation.

Conclusions:

• The sequence of ligand binding significantly impacts integrin activation pathways.
• Molecular dynamics simulations provide insights into the complex allosteric mechanisms of I-domain-containing integrins.
• Understanding these pathways is vital for deciphering cellular adhesion and mechanotransduction.