Differential stimulation of PKC phosphorylation of potassium channels by ZIP1 and ZIP2.

Targeting of protein modification enzymes is a key biochemical step to achieve specific and effective posttranslational modifications. Two alternatively spliced ZIP1 and ZIP2 proteins are described, which bind to both Kvbeta2 subunits of potassium channel and protein kinase C (PKC) zeta, thereby acting as a physical link in the assembly of PKCzeta-ZIP-potassium channel complexes. ZIP1 and ZIP2 differentially stimulate phosphorylation of Kvbeta2 by PKCzeta. They also interact to form heteromultimers, which allows for a hybrid stimulatory activity to PKCzeta. Finally, ZIP1 and ZIP2 coexist in the same cell type and are elevated differentially by neurotrophic factors. These results provide a mechanism for specificity and regulation of PKCzeta-targeted phosphorylation.