The optimal activation of cAMP-responsive element binding protein (CREB), similar to the full activation of T lymphocytes, requires the stimulation of both CD3 and CD28, Using a reporter system to detect interaction of CREB and CREB-binding protein (CBP), in this study we found that CREB binds to CBP only by engagement of both CD3 and CD28, CD3/CD28-promoted CREB-CBP interaction was dependent on p38 mitogen-activated protein kinase (MAPK) and calcium/calmodulin-dependent protein kinase (CaMK) IV in addition to the previously identified extracellular signal-regulated kinase pathway, Extracellular signal-regulated kinase, CaMKIV, and p38 MAPK were also the kinases involved in CREB Ser(133) phosphorylation induced by CD3/CD28, A reconstitution experiment illustrated that optimum CREB-CBP interaction and CREB trans-activation were attained when these three kinase pathways were simultaneously activated in T cells, Our results demonstrate that coordinated activation of different kinases leads to full activation of CREB. Notably, CD28 ligation activated p38 MAPK and CaMKIV, the kinases stimulated by CD3 engagement, suggesting that CD28 acts by increasing the activation extent of p38 MAPK and CaMKIV, These results support the model of a minimum activation threshold for CREB-CBP interaction that can be reached only when both CD3 and CD28 are stimulated.
