Effects of fatty acids on translocation of the γ- and ∊-subspecies of protein kinase C (PKC) in living cells were investigated using their proteins fused with green fluorescent protein (GFP). γ-PKC-GFP and ∊-PKC-GFP predominated in the cytoplasm, but only a small amount of γ-PKC-GFP was found in the nucleus. Except at a high concentration of linoleic acid, all the fatty acids examined induced the translocation of γ-PKC-GFP from the cytoplasm to the plasma membrane within 30 s with a return to the cytoplasm in 3 min, but they had no effect on γ-PKC-GFP in the nucleus. Arachidonic and linoleic acids induced slow translocation of ∊-PKC-GFP from the cytoplasm to the perinuclear region, whereas the other fatty acids (except for palmitic acid) induced rapid translocation to the plasma membrane. The target site of the slower translocation of ∊-PKC-GFP by arachidonic acid was identified as the Golgi network. The critical concentration of fatty acid that induced translocation varied among the 11 fatty acids tested. In general, a higher concentration was required to induce the translocation of ∊-PKC-GFP than that of γ-PKC-GFP, the exceptions being tridecanoic acid, linoleic acid, and arachidonic acid. Furthermore, arachidonic acid and the diacylglycerol analogue (DiC8) had synergistic effects on the translocation of γ-PKC-GFP. Simultaneous application of arachidonic acid (25 μM) and DiC8 (10 μM) elicited a slow, irreversible translocation of γ-PKC-GFP from the cytoplasm to the plasma membrane after rapid, reversible translocation, but a single application of arachidonic acid or DiC8 at the same concentration induced no translocation.
These findings confirm the involvement of fatty acids in the translocation of γ- and ∊-PKC, and they also indicate that each subspecies has a specific targeting mechanism that depends on the extracellular signals and that a combination of intracellular activators alters the target site of PKCs.