Arg-Tyr-Asp (RYD) and Arg-Cys-Asp (RCD) motifs in dendroaspin promote selective inhibition of beta(1) and beta(3) integrins

Arg-Gly-Asp (RGD) is a unique minimal integrin-binding sequence that is fou nd within several glycoprotein ligands. This sequence has also been found i n snake-venom anti-platelet proteins, including the disintegrins and dendro aspin, a natural variant of short-chain neurotoxins isolated from the venom of Dendroaspis jamesonii. In the present study, the motifs RYD and RCD wer e introduced into the dendroaspin scaffold to replace RGD. Both motifs in d endroaspin caused inhibition of ADP-induced platelet aggregation with IC50 values of 200 and 300 nM respectively, similar to that of the wild-type RGD motif (170 nM). In comparison with wild-type dendroaspin, both RYD- and RC D-containing dendroaspins were more selective in the inhibition of the adhe sion of K562 cells to laminin rather than to fibrinogen and fibronectin, ev en though they were 10-30-fold less potent at inhibiting K562 cell (contain ing alpha (5)/beta (1) integrin) adhesion to laminin compared with wild-typ e. Interestingly, the RYD motif produced a similar IC,, value to the RGD mo tif at inhibiting A375-SM cell (beta (3) integrin) adhesion to collagen, wh ereas the RCD motif was approx. 2-6-fold less potent compared with either R GD or RYD. These findings show that the selectivity of dendroaspin binding to beta (1) and beta (3) integrins can be modulated by the introduction of alternative cell recognition sequences.