T. Isobe et al., PROPOLYPEPTIDE OF VON-WILLEBRAND-FACTOR IS A NOVEL LIGAND FOR VERY LATE ANTIGEN-4 INTEGRIN, The Journal of biological chemistry, 272(13), 1997, pp. 8447-8453
We have previously reported that propolypeptide of von Willebrand fact
or (pp-vWF) promotes melanoma cell adhesion in a beta 1 integrin-depen
dent manner. In this report, we identified the alpha subunit of the ce
ll adhesion receptor for pp-vWF as alpha 4. Human leukemia cell lines
that express alpha 4 beta 1 integrin (very late antigen-4, VLA-4), but
not cell lines which lack VLA-4, attached well to pp-vWF substrate an
d these adhesions were completely inhibited by anti-alpha 4 integrin m
onoclonal antibody HP2/1. Adhesion of mouse melanoma expressing alpha
4 integrin was also inhibited by anti-mouse alpha 4 mAb PS/2. Furtherm
ore, transfection of human alpha 4 cDNA into alpha 4(-) Chinese hamste
r ovary cells resulted in an acquisition of adhesive activity to pp-vW
F, indicating that pp-vWF is a ligand for VLA-4 integrin. Using a reco
mbinant fragment of pp-vWF, the cell attachment site was shown to be l
ocated within amino acid residues 376-455 of pp-vWF. A series of synth
etic peptides covering this region were tested for the ability to prom
ote cell attachment and a 15-residue peptide designated T2-15 (DCQDHSF
SIVIETVQ, residues numbered 395-409) promoted VLA-4 dependent cell adh
esion. The peptide was also capable of inhibiting cell adhesion to pp-
vWF, suggesting that this sequence represents the cell attachment site
, By affinity chromatography using peptide T2-15-Sepharose, it was fou
nd that alpha 4 beta 1 integrin complex from extracts of surface iodin
ated B16 cells specifically bound to the peptide. These results strong
ly suggest that pp-vWF is a novel physiological ligand for VLA-4.