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Affinity and kinetic analysis of the molecular interaction of ICAM-1 and leukocyte function-associated antigen-1
1New Product Research Laboratories III, Daiichi Pharmaceutical Co., Tokyo, Japan.
Insights
The interaction between ICAM-1 and leukocyte function-associated antigen-1 (LFA-1) demonstrates high affinity and slow dissociation. This molecular interaction may explain firm adhesion in cellular events.
Area of Science:
- Immunology
- Molecular Biology
- Cell Adhesion
Background:
- Leukocyte function-associated antigen-1 (LFA-1) is a beta2 integrin.
- Intercellular Adhesion Molecule-1 (ICAM-1) is an Ig superfamily member.
- LFA-1/ICAM-1 interaction is crucial for T cell activation and leukocyte migration.
Purpose of the Study:
- To investigate the molecular kinetics of the ICAM-1/LFA-1 interaction.
- To characterize the binding affinity and dissociation rates at a molecular level.
Main Methods:
- Surface Plasmon Resonance (SPR) technology was employed.
- A soluble form of LFA-1 (sLFA-1) was produced and analyzed.
- Kinetic analysis was performed using a chimeric ICAM-1 (D1D2-IgG) fusion protein.
Main Results:
- Monomeric sLFA-1 bound to D1D2-IgG with a dissociation constant (Kd) of 500 nM.
- The dissociation rate constant (k(diss)) was determined to be 0.1 s(-1).
- Monomeric membrane-bound LFA-1 exhibited similar binding kinetics.
Conclusions:
- The monovalent ICAM-1/LFA-1 interaction exhibits high affinity and a slow dissociation rate.
- These kinetic properties suggest a mechanism for firm cellular adhesion.
- Findings provide molecular insights into immune cell trafficking and activation.
Abstract:
LFA-1 is a member of the beta2 integrin family, and interacts with ICAM-1, a member of the Ig superfamily containing five Ig-like domains. Interaction of LFA-1 with ICAM-1 is important in a number of cellular events, including Ag-specific T cell activation and leukocyte transendothelial migration, which are known to be typically transient and highly regulated. In this study, we have used surface plasmon resonance technology to study the ICAM-1/LFA-1 interaction at the molecular level. A soluble form of LFA-1 (sLFA-1), normally expressed as two noncovalently associated membrane-bound subunits, has been produced, and its interaction with ICAM-1 has been examined. The kinetic analysis of a monomeric sLFA-1 binding to the first two domains of ICAM-1 expressed as a chimeric IgG fusion protein (D1D2-IgG) revealed that sLFA-1 was bound to the D1D2-IgG chimera with a Kd of 500 nM and dissociated with a k(diss) of 0.1 s(-1). Monomeric membrane-bound LFA-1 purified from plasma membranes showed a similar kinetic to sLFA-1. These results suggest that the monovalent interaction between ICAM-1 and LFA-1 has a primarily high affinity and a slow dissociation rate constant as compared with other adhesion molecules, suggesting a potential mechanism for firm adhesion.