Residues within a conserved amino acid motif of domains 1 and 4 of VCAM-1 are required for binding to VLA-4.
Vascular cell adhesion molecule 1 (VCAM-1), a member of the Ig superfamily originally identified on activated endothelium, binds to the integrin very late antigen-4 (VLA-4), also known as alpha 4 beta 1 or CD49d/CD29, to support cell-cell adhesion. Studies based on cell adhesion to two alternatively spliced forms of VCAM-1 or to chimeric molecules generated from them and intercellular adhesion molecule-1 (ICAM-1) have demonstrated two VLA-4 binding sites on the predominate form of VCAM-1. Here, we studied VLA-4-dependent adhesion of the lymphoid tumor cell line Ramos to cells expressing wild type and mutant forms of VCAM-1. Results based on domain deletion mutants demonstrated the existence and independence of two VLA-4-binding sites located in the first and fourth domains of VCAM-1. Results based on amino acid substitution mutants demonstrated that residues within a linear sequence of six amino acids found in both domain 1 and 4 were required for VLA-4 binding to either domain. Five of these amino acids represent a conserved motif also found in ICAM domains. We propose that integrin binding to these Ig-like domains depends on residues within this conserved motif. Specificity of integrin binding to Ig-like domains may be regulated by a set of nonconserved residues distinct from the conserved motif.
Vonderheide
R H
RH
Center for Blood Research, Dana-Farber Cancer Institute, Boston, Massachusetts.
Tedder
T F
TF
Springer
T A
TA
Staunton
D E
DE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D006801:Humans; D018799:Intercellular Adhesion Molecule-1; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D016029:Receptors, Very Late Antigen / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D019010:Vascular Cell Adhesion Molecule-1
D015815:Cell Adhesion Molecules; D017931:DNA Primers; D016029:Receptors, Very Late Antigen; D011993:Recombinant Fusion Proteins; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1