Interaction of ICAM‐1 with β2‐integrin CD11c/CD18: Characterization of a peptide ligand that mimics a putative binding site on domain D4 of ICAM‐1

C Frick, A Odermatt, K Zen, KJ Mandell… - European journal of …, 2005 - Wiley Online Library
C Frick, A Odermatt, K Zen, KJ Mandell, H Edens, R Portmann, L Mazzucchelli, DL Jaye
European journal of immunology, 2005Wiley Online Library
The integrin CD11c/CD18 plays a role in leukocyte and cell matrix adhesion and is highly
expressed in certain hematopoietic malignancies. To better characterize ligand binding
properties, we panned random peptide phage‐display libraries over purified CD11c/CD18.
We identified a phage expressing the circular peptide C‐GRWSGWPADL‐C. C‐
GRWSGWPADL‐C phage bound specifically to CD11c/CD18 expressing monocytes but not
CD11c/CD18 negative lymphocytes and showed 5× 103‐fold higher binding to purified …
Abstract
The integrin CD11c/CD18 plays a role in leukocyte and cell matrix adhesion and is highly expressed in certain hematopoietic malignancies. To better characterize ligand binding properties, we panned random peptide phage‐display libraries over purified CD11c/CD18. We identified a phage expressing the circular peptide C‐GRWSGWPADL‐C. C‐GRWSGWPADL‐C phage bound specifically to CD11c/CD18 expressing monocytes but not CD11c/CD18 negative lymphocytes and showed 5 × 103‐fold higher binding to purified CD11c/CD18 than control phage, without binding to CD11b/CD18. Peptide sequence analysis revealed a similar sequence in domain D5 of ICAM‐1 and an alternative, phase‐shifted motif in domain D4. Surface plasmon resonance experiments demonstrated direct interaction of ICAM‐1 and CD11c/CD18. A soluble fusion protein containing the extracellular domain of ICAM‐1 abolished C‐GRWSGWPADL‐C phage binding to CD11c/CD18. Moreover, synthetic monomeric circular peptide C‐GRWSGWPADL‐C bound specifically to CD11c/CD18 and inhibited ICAM‐1 binding. Its rather low binding affinity and inability to displace pentavalent C‐GRWSGWPADL‐C phage from CD11c/CD18 suggests that a multimeric display of the selected peptide is essential for high affinity binding. Using ICAM‐1 deletion constructs, we showed that domain D4 is required for interaction with CD11c/CD18, suggesting that C‐GRWSGWPADL‐C phage binds specifically to CD11c/CD18 by structurally mimicking the interaction site on D4 of ICAM‐1.
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