14-3-3 Proteins directly regulate Ca²⁺/calmodulin-dependent protein kinase kinase α through phosphorylation-dependent multisite binding

Ca²⁺/calmodulin-dependent protein kinase kinase α (CaMKKα) plays critical roles in the modulation of neuronal cell survival as well as many other cellular activities. Here we show that 14-3-3 proteins directly regulate CaMKKα when the enzyme is phosphorylated by protein kinase A on either Ser74 or Ser475. Mutational analysis revealed that these two serines are both functional: the CaMKKα mutant with a mutation at either of these residues, but not the double mutant, was inhibited significantly by 14-3-3. The mode of regulation described herein differs the recently described mode of 14-3-3 regulation of CaMKKα.