Human endothelial-cell specific molecule-1 binds directly to the integrin CD11a/CD18 (LFA-1) and blocks binding to intercellular adhesion molecule-1.
ICAMs are ligands for LFA-1, a major integrin of mononuclear cells involved in the immune and inflammatory processes. We previously showed that endothelial cell specific molecule-1 (ESM-1) is a proteoglycan secreted by endothelial cells under the control of inflammatory cytokines. Here, we demonstrate that ESM-1 binds directly to LFA-1 onto the cell surface of human blood lymphocytes, monocytes, and Jurkat cells. The binding of ESM-1 was equally dependent on Ca(2+), Mg(2+), or Mn(2+) divalent ions, which are specific, saturable, and sensitive to temperature. An anti-CD11a mAb or PMA induced a transient increase in binding, peaking 5 min after activation. Direct binding of ESM-1 to LFA-1 integrin was demonstrated by specific coimmunoprecipitation by CD11a and CD18 mAbs. A cell-free system using a Biacore biosensor confirmed that ESM-1 and LFA-1 dynamically interacted in real time with high affinity (K(d) = 18.7 nM). ESM-1 consistently inhibited the specific binding of soluble ICAM-1 to Jurkat cells in a dose-dependent manner. These results suggest that ESM-1 and ICAM-1 interact with LFA-1 on binding sites very close to but distinct from the I domain of CD11a. Through this mechanism, ESM-1 could be implicated in the regulation of the LFA-1/ICAM-1 pathway and may therefore influence both the recruitment of circulating lymphocytes to inflammatory sites and LFA-1-dependent leukocyte adhesion and activation.
Béchard
D
D
Institut National de la Santé et de la Recherche Médicale Unité 416, Institut Pasteur de Lille, France.
Scherpereel
A
A
Hammad
H
H
Gentina
T
T
Tsicopoulos
A
A
Aumercier
M
M
Pestel
J
J
Dessaint
J P
JP
Tonnel
A B
AB
Lassalle
P
P
D015374:Biosensing Techniques; D018821:CD18 Antigens / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002474:Cell-Free System; D003199:Computer Systems; D004730:Endothelium, Vascular / Q000502:physiology*; D006801:Humans; D007249:Inflammation; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D019169:Jurkat Cells / Q000378:metabolism; D008213:Lymphocyte Activation / Q000502:physiology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D009363:Neoplasm Proteins; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism* / Q000494:pharmacology; D011509:Proteoglycans; D013696:Temperature; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D018821:CD18 Antigens; C101134:ESM1 protein, human; D016169:Lymphocyte Function-Associated Antigen-1; D009363:Neoplasm Proteins; D011506:Proteins; D011509:Proteoglycans; D018799:Intercellular Adhesion Molecule-1; D013755:Tetradecanoylphorbol Acetate