Protein kinase C remains functionally active during TPA induced neuronal differentiation of SH-SY5Y human neuroblastoma cells.
SH-SY5Y human neuroblastoma cells can be induced to differentiate into a neuronal phenotype by treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). In other cell systems, TPA treatment frequently leads to down-regulation of protein kinase C (PKC). However, we now report that TPA-treated and non-treated SH-SY5Y cells express PKC-alpha, but not PKC-beta and PKC-gamma, mRNA. Furthermore, only a slight down-regulation of the PKC-alpha protein could be seen during prolonged treatment with 16 nM TPA, the concentration giving optimal differentiation. In contrast, a higher concentration of TPA (1.6 microM) results in a poor neuronal differentiation and a complete down-regulation of PKC-alpha. PKC-alpha was rapidly translocated to the particulate fraction and remained membrane bound for at least 4 days during treatment with 16 nM TPA. In such cells a sustained increased level of the phosphorylated form of a 80,000 Dalton PKC-substrate was found. In addition to this sustained augmented phosphorylation, administration of fresh TPA at day 4 caused a small but reproducible further increased level of phosphorylated substrate. When the PKC activity was measured by the histone phosphorylation assay a substantial fraction of the initial enzyme activity could still be detected after 4 days of TPA treatment. Taken together, the data demonstrate that PKC remains functionally active during TPA induced differentiation of SH-SY5Y cells, which may suggest a continuous role for the enzyme during the differentiation process.
Parrow
V
V
Department of Pathology, University Hospital, Uppsala, Sweden.
Nånberg
E
E
Heikkilä
J
J
Hammerling
U
U
Påhlman
S
S
D015152:Blotting, Northern; D002454:Cell Differentiation; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate