AN ALL-D AMINO-ACID PEPTIDE MODEL OF ALPHA-1(IV)531-543 FROM TYPE-IV COLLAGEN BINDS THE ALPHA(3)BETA(1) INTEGRIN AND MEDIATES TUMOR-CELL ADHESION, SPREADING, AND MOTILITY

Type IV collagen promotes integrin-mediated cell adhesion, spreading, and motility. Several regions within the triple-helical domain of type IV collagen have been identified as tumor cellular recognition sites, Among these regions, the (alpha 1(IV)531-543 sequence, designated L-H ep-III, promotes integrin-mediated tumor cell adhesion and directly bi nds to the alpha(3) beta(1) integrin [Miles, A. J., et al. (1994) J. B iot. Chem. 269, 30939-30945; Miles, A, J.,, et al, (1995) J. Biol. Che m. 270, 29047-29050]. We have presently compared the activities of the all-D enantiomeric peptide model of alpha 1(IV)531-543, designated D- Hep-III, with L-Hep-III, for promoting the adhesion, spreading, and mo tility of metastatic melanoma and breast carcinoma cells, D-Hep-III wa s found to support melanoma and breast carcinoma cell adhesion, spread ing, and motility in a dose-dependent fashion similar to that of L-Hep -m. The adhesions of melanoma and breast carcinoma cells to both type IV collagen and fibronectin were effectively inhibited by L-Hep-m and D-Hep-III, Melanoma cell invasion of the basement membrane was also in hibited by D-Hep-III, Characterization of the cell surface receptor fo r D-Hep-III was acheived via cell adhesion assays and affinity chromat ography using monoclonal antibodies against integrin subunits, Immunop recipitation analysis following EDTA elution from a D-Hep-III affinity column indicated that D-Hep-III binds to the alpha(3) beta(1) integri n but not to the alpha(2) or alpha(6) integrin subunits, In summary, t hese studies demonstrate that an all-D model of the alpha 1(IV)531-543 sequence mimics the biological activities of the all-L peptide. D-Hep -IU. is the first all-D peptide that has been shown to promote tumor c ell adhesion, spreading, and migration, inhibit tumor cell adhesion an d migration on type IV collagen and invasion of the basement membrane, and bind directly to an integrin. Due to the resistance to proteolysi s, all-D receptor-binding peptides such as D-Hep-III have great potent ial for in vivo studies and as therapeutic agents.