MARK3
MARK3, historically named C-TAK1, is a microtubule affinity-regulating kinase that phosphorylates numerous 14-3-3-binding sites to control protein localization and activity. Characterized substrates include the phosphatase Cdc25C, whose MARK3 phosphorylation creates a docking site for 14-3-3 proteins, and the kinase scaffold KSR1, which is held inactive in the cytoplasm until Ras pathway input overrides this restraint. MARK3 also phosphorylates class IIa histone deacetylases, linking polarity and metabolic signals to gene expression, and it phosphorylates tau-family microtubule-associated proteins like its paralogs. Activated by LKB1, MARK3 has further been implicated in hepatic metabolism and liver tumorigenesis, adding parenchymal functions to its canonical cytoskeletal repertoire.
