Subcellular localization of diacylglycerol-responsive protein kinase C isoforms in HeLa cells

초록

Subcellular localization of protein kinase often plays an important role in determining its activity and specificity. Protein kinase C (PKC), a family of multi-gene protein kinases has long been known to translocate to the particular cellular components in response to DAG or its analog phorbol esters. We used C-terminal green fluorescent protein (GFP) fusion PKC isoforms to visualize the subcellular distribution of individual PKC isoforms. After transient transfection of classical and novel PKC-GFP expression vectors in the cervical cancer HeLa cells, intracellular localization of overexpressed proteins was monitored by fluorescence microscopy. In unstimulated HeLa cells, with a few exceptions all PKC isoforms were found to be distributed throughout the cytoplasm. PKCθ was mostly localized to the Golgi, and PKCγ, PKCδ and PKCη showed cytoplasmic distribution with a Golgi localization. DAG analog TPA induced translocation of PKC-GFP generally to the plasma membrane. PKCα, PKCη and PKCθ were also localized to the Golgi in response to TPA. Only PKCδ found to be associated with the nuclear membrane after transient TPA treatment. These results suggest that specific PKC isoforms localize to different intracellular sites and exhibit distinct biological effects.