Role of MEKK2 Phosphorylation at Threonine 263 on SMYD3-Mediated Methylation of Lysine 260

MEKK2 is a protein serine/threonine-kinase involved in the activation of many MAP-kinase signalling pathways. In a previous study, SMYD3-mediated methylation at K260 of MEKK2 was demonstrated to promote aberrant input downstream of oncogenic Ras-signaling, promoting Ras-driven PDAC and LAC progression. Our lab has previously characterized the role of MEKK2 phosphorylation at T283 and has recently discovered a novel second phosphorylation site at T263. We show that together, these sites form the bipartite binding group for 14-3-3 adapter proteins. This study focuses on characterizing T263 and T283 as regulatory phosphosites in K260 methylation and implicates 14-3-3 as a promoting factor in facilitating SMYD3-mediated methylation at K260. Our findings provide a potential mechanism of MEKK2 oncogenic function, whereby 14-3-3 preserves phosphorylation at T263 and T283, together promoting K260 methylation and MEKK2 activation. Our study characterizes T263 and T283 of MEKK2 and 14-3-3 phosphoadapter proteins as potential therapeutic targets in PDAC and LAC.