A novel PIP₂ binding of ?PKC and its contribution to the neurite induction ability

Protein kinase C-F (epsilon PKC) induces neurite outgrowth in neuroblastoma cells but molecular mechanism of the epsilon PKC-induced neurite outgrowth is not fully understood. Therefore, we investigated the ability of phosphatidylinositol 4,5-bis-phosphate (PIP2) binding of epsilon PKC and its correlation with the neurite extension. We found that full length epsilon PKC bound to PIP2 in a 12-o-tetradecanoylphorbol-13-acetate dependent manner, while the regulatory domain of epsilon PKC (epsilon RD) bound to PIP2 without any stimulation. To identify the PIP2 binding region, we made mutants lacking several regions from epsilon RD, and examined their PIP2 binding activity. The mutants lacking variable region 1 (V1) bound to PIP2 stronger than intact epsilon RD, while the mutants lacking pseudo-substrate or common region 1 (C1) lost the binding. The PIP2 binding ability of the V3-deleted mutant was weakened. Those PIP2 bindings of epsilon PKC, epsilon RD and the mutants well correlated to their neurite induction ability. In addition, a chimera of pleckstrin homology domain of phospholipase C delta and the V3 region of epsilon PKC revealed that PIP2 binding domain and the V3 region are sufficient for the neurite induction, and a first 16 amino acids in the V3 region was important for neurite extension. In conclusion, epsilon PKC directly binds to PIP2 mainly through pse udo-su bst rate and common region 1, contributing to the neurite induction activity.