A dynamically regulated 14-3-3, slob, and slowpoke potassium channel complex in Drosophila presynaptic nerve terminals

Slob is a novel protein that binds to the carboxy-terminal domain of the Dr osophila Slowpoke (dSlo) calcium-dependent potassium (K-Ca) channel. A yeas t two-hybrid screen with Slob as bait identifies the zeta isoform of 14-3-3 as a Slob-binding protein. Coimmunoprecipitation experiments from Drosophi la heads and transfected cells confirm that 14-3-3 interacts with dSlo via Slob. All three proteins are colocalized presynaptically at Drosophila neur omuscular junctions. Two serine residues in Slob are required for 14-3-3 bi nding, and the binding is dynamically regulated in Drosophila by calcium/ca lmodulin-dependent kinase II (CaMKII) phosphorylation. 14-3-3 coexpression dramatically alters dSlo channel properties when wild-type Slob is present but not when a double serine mutant Slob that is incapable of binding 14-3- 3 is present. The results provide evidence for a dSlo/Slob/14-3-3 regulator y protein complex.