Roles of PLC-gamma2 and PKCalpha in TPA-induced apoptosis of gastric cancer cells.
OBJECTIVE
To investigate the roles of PLCgamma2 and PKCalpha in TPA-induced apoptosis of gastric cancer cells.


METHODS
Human gastric cancer cell line MGC80-3 was used. Protein expression levels of PLCgamma2 and PKCalpha were detected by Western blot. Protein localization of PLCgamma2 and PKCalpha was shown by immunofluorescence analysis under laser-scanning confocal microscope. Apoptotic morphology was observed by DAPI fluorescence staining, and apoptotic index was counted among 1,000 cells randomly.


RESULTS
Treatment of gastric cancer cells MGC80-3 with TPA not only up-regulated expression of PLC-gamma2 protein, but also induced PLC-gamma2 translocation from the cytoplasm to the nucleus. However, this process was not directly associated with apoptosis induction. Further investigation showed that PKCalpha translocation from the cytoplasm to the nucleus was correlated with initiation of apoptosis. To explore the inevitable linkage between PLC-gamma2 and PKCalpha during apoptosis induction, PLC inhibitor U73122 was used to block PLC-gamma2 translocation, in which neither stimulating PKCalpha translocation nor inducing apoptosis occurred in MGC80-3 cells. However, when U73122-treated cells were exposed to TPA, not only PLC-gamma2, but also PKCalpha was redistributed. On the other hand, when cells were treated with PKC inhibitor alone, PLC-gamma2 protein was still located in the cytoplasm. However, redistribution of PLC-gamma2 protein occurred in the presence of TPA, no matter whether PKC inhibitor existed or not.


CONCLUSIONS
PLC-gamma2 translocation is critical in transmitting TPA signal to its downstream molecule PKCalpha. As an effector, PKCalpha directly promotes apoptosis of MGC80-3 cells. Therefore, protein translocation of PLCgamma2 and PKCalpha is critical event in the process of apoptosis induction.
Zhang
Bing
B
Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, Fujian Province, China.
Wu
Qiao
Q
Ye
Xiao-Feng
XF
Liu
Su
S
Lin
Xiao-Feng
XF
Chen
Mu-Chuan
MC
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002273:Carcinogens / Q000494:pharmacology; D045744:Cell Line, Tumor / Q000166:cytology / Q000201:enzymology; D006801:Humans; D051966:Phospholipase C gamma; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D015398:Signal Transduction / Q000502:physiology; D013274:Stomach Neoplasms; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism*
D002273:Carcinogens; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D013755:Tetradecanoylphorbol Acetate