High-Affinity Bent β₂-Integrin Molecules in Arresting Neutrophils Face Each Other through Binding to ICAMs In cis

Area of Science:

• Cellular Biology
• Immunology
• Biophysics

Background:

• Leukocyte adhesion is crucial for immune response and relies on β₂-integrin activation.
• Resting integrins are in a bent-closed conformation (E^-H^-), unable to bind ligands.
• Activated integrins (E⁺H⁺) bind intercellular adhesion molecules (ICAMs) on opposing cells (trans) or the same cell (cis).

Purpose of the Study:

• To investigate the spatial patterning of activated integrins on primary human neutrophils.
• To map the high-resolution cell surface localization of activated integrins during neutrophil arrest.
• To elucidate the mechanism behind the spatial organization of activated integrins.

Main Methods:

• Super-resolution microscopy (Super-STORM) was combined with molecular modeling.
• Precise localization of activated integrin molecules on primary human neutrophils was achieved.
• Experiments involved blocking integrin binding to ICAMs in cis.

Main Results:

• Activated E^-H⁺ integrins form oriented nanoclusters facing each other during neutrophil arrest.
• This face-to-face orientation suggests a non-random molecular pattern.
• Blocking integrin binding to ICAMs in cis significantly disrupted this orientation.

Conclusions:

• Activated β₂-integrins form specific nanocluster patterns on neutrophils during arrest.
• The spatial organization of integrins is critical for effective leukocyte adhesion.
• Integrin binding to ICAMs in cis plays a role in establishing this oriented pattern.