Phosphorylation of beta-actin by protein kinase C-delta in camptothecin analog-induced leukemic cell apoptosis.
OBJECTIVE
This study was conducted to reveal new proteins involved in acute myeloid leukemia (AML) cell apoptosis.


METHODS
Using camptothecin analog NSC606985- induced leukemic U937 cell apoptosis as a model, this study performed a differential proteomic analysis during apoptosis induction. The significantly modulated protein was underwent further investigation in the apoptotic process.


RESULTS
We found that beta-actin protein presented two different spots on the two-dimensional electrophoresis (2-DE) map, which shared similar molecular weight and different pI. Those two spots demonstrated contrary changes (disappeared on the basic-end and increased on the acid-end spot) during apoptosis induction, although the total level of beta-actin kept constant. This observation was further confirmed by immunoblot analysis on 2-DE gel. When NSC606985-treated cell lysate was incubated with alkaline phosphotase, beta-actin on the basic-end spot was restored, indicating increased phosphorylation of beta-actin during NSC606985- induced apoptosis. Moreover, the polymerization of actin also decreased after NSC606985 treatment. The increased beta-actin phosphorylation and decreased actin polymerization was antagonized by pre-treatment of rottlerin, a specific protein kinase C-delta (PKC delta) inhibitor.


CONCLUSIONS
All these results indicate that beta-actin was phosphorylated during apoptosis induction, which was mediated by activated PKC delta.
Wang
Shuang
S
Department of Pathophysiology, Xiangya Medical College, Central South University, Changsha, China.
Zheng
Ying
Y
Yu
Yun
Y
Xia
Li
L
Chen
Guo-qiang
GQ
Yang
Yong-zong
YZ
Wang
Li-shun
LS
D000199:Actins / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism*; D020298:U937 Cells
D000199:Actins; D000972:Antineoplastic Agents, Phytogenic; D051745:Protein Kinase C-delta; D002166:Camptothecin