Acta Pharmacologica Sinica 2008 January; 29 (1): 135-142; doi: 10.1111/j.1745-7254.2008.00753.x

Acta Pharmacologica Sinica 2008 January; 29 (1): 135-142; doi: 10.1111/j.1745-7254.2008.00753.x

Original Article

Phosphorylation of β-actin by protein kinase C-delta in camptothecin analog-induced leukemic cell apoptosis¹

Shuang WANG^2,3,4, Ying ZHENG³, Yun YU³, Li XIA³, Guo-qiang CHEN³, Yong-zong YANG^2,4,5, Li-shun WANG^3,5

²Department of Pathophysiology, Xiangya Medical College, Central South University, Changsha 410078, China;³Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of National Ministry of Education, Shanghai Jiao-Tong University School of Medicine (SJTU-SM), Shanghai 200025, China;⁴Institute of Cardiovascular Disease, University of South China, Hengyang 421001, China

Aim: 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 β-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 β-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, β-actin on the basic-end spot was restored, indicating increased phosphorylation of β-actin during NSC606985-induced apoptosis. Moreover, the polymerization of actin also decreased after NSC606985 treatment. The increased β-actin phosphorylation and decreased actin polymerization was antagonized by pre-treatment of rottlerin, a specific protein kinase C-delta (PKCδ) inhibitor.

Conclusion: All these results indicate that β-actin was phosphorylated during apoptosis induction, which was mediated by activated PKCδ.

Keywords: leukemia; apoptosis; proteomics; β-actin;phosphorylation; PKCδ

¹This work was supported in part by grants from Ministry of Science and Technology (No 2002CB512806, No 2006CB910104, 2006AA02Z105), National Natural Science Foundation of China (30600261, 30500215,30500216), Shanghai Science and Technology Commission (05JC14032, 07QA14041).
⁵ Correspondence to Dr Li-shun WANG or Prof Yong-zong YANG Phn/Fax 86-21-6415-4900.
E-mail jywangls@shsmu.edu.cn (Li-shun WANG)
E-mail yzyanghy@163.com (Yong-zong YANG)

Received 2007-09-21 Accepted 2007-10-12

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