Ligand-specific binding forces of LFA-1 and Mac-1 in neutrophil adhesion and crawling

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• Polymorphonuclear leukocyte (PMN) recruitment is vital for immune responses.
• Lymphocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1) are key adhesion molecules involved in PMN recruitment.
• The precise mechanisms of ligand-specific binding and their functional consequences remain incompletely understood.

Purpose of the Study:

• To compare the dynamic force spectra of various LFA-1/Mac-1-ligand bonds.
• To investigate the functional roles of these bonds in mediating PMN recruitment under shear flow.
• To elucidate the molecular mechanisms underlying PMN adhesion and migration.

Main Methods:

• Single-molecule atomic force microscopy (AFM) was used to measure dynamic force spectra of LFA-1/Mac-1-ligand bonds.
• In vitro shear flow assays were employed to test the function of these bonds in PMN recruitment.
• Analysis of bond rupture forces, lifetimes, and their impact on PMN adhesion, spreading, and polarization.

Main Results:

• Distinct bond rupture forces and lifetimes were observed for different LFA-1/Mac-1 ligands, indicating diverse regulatory roles.
• LFA-1 primarily mediates PMN adhesion to ICAM-1 and ICAM-2, while Mac-1 binds to RAGE, JAM-A, and JAM-C.
• Mac-1 appears more effective in inducing outside-in signaling and PMN spreading/polarization.
• LFA-1-ICAM-1 and LFA-1/Mac-1-JAM-C bonds enhance PMN crawling under high shear stress due to their mechanical strength.

Conclusions:

• The study provides novel insights into the molecular mechanisms of β2 integrin ligands in PMN recruitment.
• Differential binding properties of LFA-1 and Mac-1 to their ligands dictate distinct roles in PMN adhesion and migration.
• Understanding these specific molecular interactions is crucial for developing targeted therapies for inflammatory diseases.