CELL-ADHESION MECHANISMS - MODELING USING DERIVATIZED BEADS AND SEA-URCHIN CELL SYSTEMS

Agarose beads derivatized with amino acids, peptides, carbohydrates an d lectins were used to systematically determine what types of molecule s, isolated from all others, can make adhesive bonds strong enough to hold cell-like beads together. The results indicated that strong adhes ion occurred when at least one of the two members of certain bead pair s was derivatized with molecules that were dimers or trimers but not m onomers. Also, beads derivatized with phosphorylated amino acids, but not their non-phosphorylated counterparts, adhered to beads derivatize d with positively charged peptides. Adhesion was sensitive to ionic st rength and pH of the medium. It was proposed that adhesion occurred be tween the phosphate groups of the phosphoamino acids and amino and gua nidinium groups of the peptides. Cooperative bonding can explain the s tability of the adhesion observed in this system. Information gained f rom the bead modeling work was used to design experiments to examine t he role of phosphorylated molecules in modulating adhesion in sea urch in systems. Phosphoamino acids inhibited sperm-egg interaction, but no t reaggregation of blastula cells. Inhibitors of alkaline phosphatase, however, did inhibit reaggregation. The results suggest that cell sur face phosphorylated molecules may modulate cellular adhesiveness, in s ome systems promoting, while in others inhibiting adhesion.