Live cell fluorescence imaging of T cell MEKK2: Redistribution and activation in response to antigen stimulation of the T cell receptor

T cell activation requires engagement of the T cell receptor (TCR) at the i nterface of conjugates formed with antigen-presenting cells, TCR engagement is accompanied by a redistribution of specific signaling molecules to the cytoplasmic region of the TCR complex. In this study, immunocytochemistry a nd live cell fluorescence imaging demonstrate that T cell MEK kinase 2 (MEK K2) is translocated to the T cell/antigen-presenting cell interface in resp onse to antigen activation. MEKK2 translocation occurs more rapidly as the antigen concentration is increased. Biochemical activation of MEKK2 follows TCR stimulation, and expression of a dominant-negative MEKK2 inhibits TCR- mediated conjugate stabilization and ERK and p38 MAP kinase phosphorylation . Live cell fluorescence imaging thus enables characterization of signal tr ansducers that are dynamically translocated following TCR engagement.