A novel consensus motif in fibronectin mediates dipeptidyl peptidase IV adhesion and metastasis.

Lung endothelial dipeptidyl peptidase IV (DPPIV/CD26) is a vascular address for cancer cells decorated with cell-surface polymeric fibronectin (poly-FN). Here, we identified the DPPIV-binding sites in FN and examined the effect of binding site peptides on DPPIV/poly-FN adhesion and metastasis. Using proteolytic fragments and maltose-binding protein fusion proteins that together span full-length FN, we found DPPIV-binding sites in type III repeats 13, 14, and 15 (FNIII13, -14, and -15, respectively). DPPIV binding was mediated by the consensus motif T(I/L)TGLX(P/R)G(T/V)X and was confirmed by swapping this motif in FNIII13, -14, and -15 with the corresponding region in FNIII12, which did not bind DPPIV. DPPIV binding was lost in swapped FNIII13, -14, and -15 and gained in swapped FNIII12 (FNIII12(14)). Peptides containing the DPPIV-binding domain of FNIII14 blocked DPPIV/poly-FN adhesion and impeded pulmonary metastasis. This study adds to the classes of cell-surface adhesion receptors for FN and will help in the further characterization of the functional implications of the DPPIV/poly-FN adhesion in metastasis and possibly in cell-mediated immunity involving DPPIV-expressing lymphocytes.