T-cells are activated by a combination of protein-tyrosine kinases and adaptor proteins which create multi-protein complexes (1,2). Adaptor proteins such as adhesion and degranulation-promoting adapter protein (ADAP) and SKAP1 (aka SKAP55; Src kinase-associated phosphoprotein of 55 KDa) can regulate the adhesion and motility of T-cells to integrins(3-7). SKAP1(8) has an unique coiled-coil-like N terminus, a PH domain and a C terminal src-homology 3 (SH3) domain which can bind to ADAP which itself has an SH3-like domain that binds to SKAP1(4), stabilizes SLP-76 micro-clusters and couples the TCR to the activation of LFA-1(7,9-12). SKAP1 also regulates Rap1–GTP-interacting adapter molecule (RapL)-Rap1 binding induced by antigen-receptor ligation(13-15). SKAP1 dimer formation has been shown by imaging studies to stabilize SLP-76 micro-clusters and facilitate adhesion (19). Its ability to form dimers does not interfere with its binding to RapL (16). Lastly, it can act as a kind of scaffold in binding to Polo-like kinase 1 (PLK1), an interaction needed for the optimal cell cycling of T-cells (17).
By contrast, glycogen synthase kinase 3 (GSK-3) is a serine/threonine kinase that is active in resting T-cells and is inactivated upon T-cell activation (18,19). Isoforms of GSK-3 α and β differ are differentially regulated in their N- and C-terminal sequences. It’s phosphorylation and inactivation is induced with TCR ligation GSK-3 (20-22), while expression of active GSK-3β (GSK-3βA9) inhibits the proliferation of T-cells (20). Protein kinase B (PKB/AKT) and its downstream target GSK-3 in T-cells appears to operate independently of guanine nucleotide exchange factor VAV-1 (21). In CD4+ T-cells, GSK-3 promotes the exit of nuclear factor of activated T-cells (NFAT) (23,24). Clinical trials using GSK-3 inhibitors have been undertaken in the treatment of type II diabetes and various neurological disorders (19,25,26). Recently, we reported that the inactivation of GSK-3α/β specifically down-regulates PD-1 expression for enhanced CTL function and clearance of infections by Murid herpes virus-4 and LCMV Cl 13 (27). Further, GSK-3 inactivation was as effective as anti-PD-1 blockade in the regression of melanoma and lymphoma tumors (28,29).
In this study, we show that GSK-3 can regulate T-cell motility. The inhibitor of GSK-3, SB415286 reduced T-cell motility in terms of the measurement of motility, distance displacement and length of distance travelled, and as a consequence reduced the number of cell contracts with other cells. These data indicate show that the inhibition of GSK-3 can influence the motility of T-cells and interactions with other cells.