The PDZ-binding domain of syndecan-2 inhibits LFA-1 high-affinity conformation

Syndecans are cell membrane proteoglycans that can modulate the activity and dynamics of some growth factor receptors and integrins. Here, we show the down-regulation of integrin lymphocyte function-associated antigen-1 (LFA-1) and inhibition of adhesion of Jurkat T cells transfected with syndecan-2. The PDZ-binding domain in the cytoplasmic region of syndecan-2 was necessary to block the LFA-1 high-affinity conformation, and to reduce cellular adhesion. A second cytoplasmic motif comprising tyrosines 179 and 191, and serines 187 and 188 contributed also to reduce LFA-1 function and cellular adhesion. Inhibition of the LFA-1 high-affinity conformation by syndecan-2 was independent of the expression of the talin head domain and RhoA, Rac1 and Cdc42 GTPases. These results demonstrate the importance of PDZ-binding domain of syndecan-2 for controlling LFA-1 affinity and cell adhesion.