Identification of an active sequence within the first immunoglobulin domain of intercellular cell adhesion molecule-1 (ICAM-1) that interacts with fibrinogen.

Monocytic cells bind fibrinogen (fg) through integrin alphaMbeta2. fg-bound monocytic cells demonstrate an enhanced adhesion to endothelial cells, which is dependent on intercellular adhesion molecule-1 (ICAM-1). Our studies differentiate fg interactions with stimulated and resting endothelial cells, which are ICAM-1 dependent and independent, respectively. This report documents a direct interaction between fg and intact ICAM-1 and with a two-Ig domain form of ICAM-1. A small region within the first Ig domain of ICAM-1, ICAM-1-(8-21) (KVILPRGGSVLVTC), was identified to interact with fg in a specific and selective manner. ICAM-1-(8-21) bound to plasmin-derived fg fragments X, D100, and D80 but not to fragment E. Consistent with this finding, fg gamma-chain peptide, fg-gamma-117-133, blocked fg interaction with ICAM-1-(8-2 1. ICAM-1-(8-21) peptide and antibodies directed against ICAM-1-(8-21) also blocked the adhesion and binding of ICAM-1-bearing Raji cells with fg. ICAM-1-(8-21) and fg-gamma-117-133 are likely to be one of the contact pairs mediating fg-ICAM-1 interactions.