Regulation of Protein
Kinase C in A-549 Cells by Phorbol Ester
CHEN Jun-Song, CHAI Min-Qiang, SONG Jian-Guo*
( State Key Laboratory of Molecular Biology, Shanghai Institute of
Biochemistry, Shanghai Institutes for Biological Sciences, the Chinese Academy
of Sciences, Shanghai 200031, China )
Abstract Protein
kinase C, a family of serine-threonine protein kinases, mediates a variety of
intracellular signaling events. Here, the regulatory effect of phorbol
12-myristate 13-acetate(PMA)on the several PKC isozymes in the human lung
carcinoma cells A-549 was studied. The expression of PKC-α、PKC-βII、PKC-γ、PKC-δ and PKC-εin A-549 cells
was examined. No detectable PKC-ζ was observed. Short-term treatment of cells
with PMA led to the translocation of these PKC isozymes, to different extent,
from cytosol to cell membrane. Whereas, prolonged treatment of cells with PMA
pronouncedly reduced the levels of PKC-α、PKC-γ、PKC-δ and PKC-ε, but the
intracellular level of PKC-βII was not affected. Furthermore, PMA was observed
to have differential effects on the down-regulation of PKC isozymes located in
the cytosol and of those located in the membrane. Prolonged PMA treatment
caused extensive decrease in the levels of cytosolic PKC-δ and PKC-γ, and
depleted cytosolic PKC-α and PKC-βII. However, the amount levels of membrane
PKC-α、PKC-βII、PKC-γ、PKC-δ isozymes were not
decreased. In contrast, PKC-ε in both cytosol and membrane fraction was
obviously down-regulated by prolonged PMA treatment. This study provided novel
evidence on the PMA-mediated activation and down-regulation of different PKC
isozymes, which might be helpful in deepening our understanding on the roles of
PKC activation and the alterations of their intracellular levels in processes
of chemical carcinogenesis.
Key words protein kinase C；PMA；translocation；Western blotting；A-549
*Corresponding author：Tel,86-21-64317660；Fax,86-21-64317660；e-mail,[email protected]