Abstract: |
MEKK2 is a serine/threonine kinase that functions as a MAPKinase kinase kinase (MAP3K) to regulate activation of MAP kinases. We recently have demonstrated that ablation of MEKK2 expression in invasive breast tumor cells dramatically inhibits xenograft metastasis, but the mechanism by which MEKK2 influences metastasis-related tumor cell function is unknown. In this study, we investigate MEKK2 function and demonstrate that silencing MEKK2 expression in breast tumor cell significantly enhances cell spread area and focal adhesion stability while reducing cell migration. We show that cell attachment to the matrix proteins fibronectin or Matrigel induces MEKK2 activation and localization to focal adhesions. Further, we reveal that MEKK2 ablation enhances focal adhesion size and frequency, thereby linking MEKK2 function to focal adhesion stability. Finally, we show that MEKK2 knockdown inhibits fibronectin-induced ERK5 signaling and FAK autophosphorylation. Taken together, our results strongly support a role for MEKK2 as a regulator of signaling that modulates breast tumor cell spread area and migration through control of focal adhesion stability. |