Integrin-associated proteins as potential therapeutic targets.

Integrins are adhesion receptors important for hematopoiesis, leukocyte trafficking, and formation of immunological synapses; hence, they may provide targets for therapeutic intervention in leukocyte-driven pathologies. Blocking integrin-ligand binding is one strategy for inhibiting integrins; however, a complete loss of integrin function can lead to mechanism-based toxicities. Because integrin alpha and beta subunits interact with a variety of other proteins to receive and transmit cellular signals, targeting these integrin-associated proteins may utilize alternative sites for intervention that lead to therapies with fewer side effects. This review summarizes integrin-associated proteins in leukocytes and focuses on four of these proteins with perceived therapeutic potential. Specific mutations in the alpha4 integrin cytoplasmic tail block or enforce binding to paxillin and thus modulate integrin signaling required for efficient cell migration. Similarly, the association of RAPL(NORE1B) with beta2 integrins may participate in adhesive and migratory events in leukocytes. The beta integrin cytoplasmic tail-binding protein talin is critical for increasing the affinity of integrins (activation), and blockade of talin binding can prevent leukocyte arrest on the endothelium. Finally, the membrane protein CD98 mediates beta1 and beta3 integrin signaling and may be involved in leukocyte functions. Identification of biologically important interactions of integrins and signaling proteins can thus pave the way to new strategies for manipulating leukocyte functions.