Human endothelial-cell specific molecule-1 binds directly to the integrin CD11a/CD18 (LFA-1) and blocks binding to...

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Intercellular Adhesion Molecules (ICAMs) are ligands for Leukocyte Function-associated Antigen-1 (LFA-1), crucial for immune and inflammatory responses.
• Endothelial cell specific molecule-1 (ESM-1) is an inflammatory cytokine-induced proteoglycan secreted by endothelial cells.

Purpose of the Study:

• To investigate the direct binding of ESM-1 to LFA-1.
• To elucidate the functional consequences of ESM-1 and LFA-1 interaction on immune cell adhesion.

Main Methods:

• Surface plasmon resonance (Biacore) to assess ESM-1 and LFA-1 binding kinetics.
• Co-immunoprecipitation assays to confirm direct ESM-1 and LFA-1 interaction.
• Inhibition assays using Jurkat cells to evaluate ESM-1's effect on ICAM-1 binding.

Main Results:

• ESM-1 directly binds to LFA-1 on human lymphocytes, monocytes, and Jurkat cells in a divalent ion-dependent manner.
• ESM-1 demonstrated high-affinity binding to LFA-1 (K(d) = 18.7 nM) and inhibited ICAM-1 binding in a dose-dependent manner.
• ESM-1 and ICAM-1 appear to bind LFA-1 at distinct sites near, but not within, the CD11a I domain.

Conclusions:

• ESM-1 directly interacts with LFA-1, modulating its binding to ICAM-1.
• ESM-1 may play a regulatory role in LFA-1/ICAM-1 pathway, influencing leukocyte recruitment and adhesion in inflammatory conditions.