NOVEL PSI-S-CH2 PEPTIDE-BOND REPLACEMENT AND ITS UTILIZATION IN THE SYNTHESIS OF NONPEPTIDIC SURROGATES OF THE LEU-ASP-VAL SEQUENCE THAT EXHIBIT SPECIFIC INHIBITORY ACTIVITIES ON CD4(-CELL BINDING TO FIBRONECTIN() T)

The Leu-Asp-Val-(LDV)-containing amino acid sequence, derived from the alternatively spliced first connecting segment region of fibronectin (FN), was shown to be recognized primarily by the alpha(4) beta(1)-int egrin receptor expressed on the surface of various cell types. This ad hesion epitope may therefore inhibit integrin-mediated cell interactio ns with the extracellular matrix glycoprotein, including adhesion, mig ration, activation and differentiation. To probe the structural requir ements for LDV recognition by integrins and examine the feasibility of inhibition of LDV-dependent cell-FN interactions, we have designed an d constructed a novel psi-S-CH2 peptide bond surrogate that was employ ed in the formation of LDV surrogates. The synthesis of the psi-S-CH2 surrogates reported herein is based on Michael addition of 4-methylpen tane thiol to an itaconic acid diester to form an S-CH2 bond. We have found that the LDV surrogates comprises of 4-methylpentanoate-Asp-i-bu tyl amide and hyl-3-(2-methylpropylaminocarbonyl)-5-thianonanoic acid interfered with CD4(+) human T-cell adhesion to FN in vitro, with an E D(50) of 280 mu g/mL. A control structural mimetic of the Leu-Glu-Val (LEV) peptide did not interfere with the T-cell-FN interaction. The sp ecificity of the reaction was substantiated by the finding that the LD V mimetics did not interfere with T-cell adhesion to laminin, another major cell-adhesive glycoprotein of the extracellular matrix. That the nonpeptidic mimetics of LDV interfered markedly with T-cell-FN adhesi ve interactions indicate that the peptide bond and the amine and carbo xyl end groups of the tripeptide makes only a minor contribution to th e integrin binding affinity. Thus, consistent with our recent report o n the production of Arg-Gly-Asp surrogates, we suggest that these cons tructs could provide novel insights into the fundamental mechanisms of integrin-ligand interactions, and serve as competitive antagonists of conceivable therapeutic value. (C) Munksgaard 1994.