| Abstract |
Effects of fatty acids on translocation of the gamma- and epsilon-subspecies of protein kinase C (PKC) in living cells were investigated using their proteins fused with green fluorescent protein (GFP). gamma-PKC-GFP and epsilon-PKC-GFP predominated in the cytoplasm, but only a small amount of gamma-PKC-GFP was found in the nucleus. Except at a high concentration of linoleic acid, all the fatty acids examined induced the translocation of gamma-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 gamma-PKC-GFP in the nucleus. Arachidonic and linoleic acids induced slow translocation of epsilon-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 epsilon-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 epsilon-PKC-GFP than that of gamma-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 gamma-PKC-GFP. Simultaneous application of arachidonic acid (25 MicroM) and DiC8 (10 microM) elicited a slow, irreversible translocation of gamma-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 gamma- and epsilon-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.
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