Protein kinase Cα can undergo membrane localization via an alternative phosphatidylinositol 4,5-bisphosphate-dependent pathway

Protein kinase Cα (PKCα) activation is known to be dependent on the metabolic product of phosphatidylinositol 4,5-bisphosphate (PIP2) by phospholipase C (PLC). Here we report that fibroblasts may have an additional PIP2-dependent mechanism for membrane localization of PKCα. We observed PKCα membrane localization in both wild type and PLCγ1 −/− mouse embryonic fibroblasts. Treatment of cells with a specific PLC inhibitor U73122 resulted in increased PIP2 levels and enhanced membrane localization of PKCα. PKCα levels in the membrane fraction decreased following incubation with PLCγ, but increased following treatment with U73122 or addition of exogenous PIP2 in vitro. In addition, PKCα interacted with PIP2-conjugate bead and mixed micelles containing PIP2. Finally, we found that PIP2 is involved in syndecan-4-mediated membrane localization of PKCα. Taken together, these data suggest that PIP2 might contribute to directly regulating the membrane localization of PKCα.