Monomeric 14-3-3 protein is sufficient to modulate the activity of the Drosophila Slowpoke calcium-dependent potassium channel

Abstract

Drosophila 14-3-3ζ (D14.3.3ζ) modulates the activity of the Slowpoke calcium-dependent potassium channel (dSlo) by interacting with the dSlo binding protein, Slob. We show here that D14-3-3ζ forms dimers in vitro. Site-directed mutations in its putative dimerization interface result in a dimerization-deficient form of D14-33ζ. Both the wild-type and dimerization-deficient forms of D14-3-3ζ bind to Slob with similar affinity and form complexes with dSlo. When dSlo and Slob are expressed in mammalian cells, the dSlo channel activity is similarly modulated by co-expression of either the wild-type or the dimerization-deficient form of D14-3-3ζ. In addition, dSlo is still modulated by wild-type D14-3-3ζ in the presence of a 14-3-3 mutant, which does not itself bind to Slob but forms heterodimers with the wild-type 14-3-3. These data, taken together, suggest that monomeric D14-3-3ζ is capable of modulating dSlo channel activity in this regulatory complex.