CYCLIC RGD PEPTIDE INHIBITS ALPHA-4-BETA-1 INTERACTION WITH CONNECTING SEGMENT-1 AND VASCULAR CELL-ADHESION MOLECULE

The integrin supergene family includes receptors for a variety of extr acellular matrix as well as cell surface proteins. Integrin alpha 4 ha s been shown to play an important role in leukocyte adhesion and extra vasation during immune and inflammatory reactions. One recognition seq uence known to interact with alpha 4 is the Leu-Asp-Val (LDV) site con tained in the connecting segment 1 region of fibronectin. Here we pres ent evidence that shows that a conformationally restricted RGD-contain ing peptide is a potent inhibitor of cell adhesion mediated by alpha 4 beta 1, a receptor not convincingly documented to interact with RGD p eptides. This peptide, 1-adamantaneacetyl-Cys- Gly-Arg-Gly-Asp-Ser-Pro -Cys (disulfide bridge between residues 1-8), blocks Jurkat cell adhes ion to connecting segment 1-containing peptides as well as cell adhesi on to cytokine activated endothelial cells. Adhesion of Jurkat cells t o either vascular cell adhesion molecule-expressing cells or recombina nt vascular cell adhesion molecule-coated plates was likewise inhibite d by this peptide. Furthermore, alpha 4 beta 1 can bind directly to a cyclic RGD peptide immobilized to Sepharose. Integrins, alpha 5 beta 1 , alpha v beta 3, alpha IIb/beta IIIa, alpha 2 beta 1, alpha v beta 5, alpha v beta 6, and alpha 3 beta 1, have been shown to recognize the Arg-Gly-Asp (RGD) sequence present in a variety of extracellular matri x proteins, and our data support the addition of alpha 4 beta 1 to thi s group. Further studies using molecular modeling of such cyclic RGD p eptides could help in the design of more potent peptides or nonpeptide mimetics that could effectively block alpha 4-mediated activity and h ave potential application in a number of inflammatory diseases.