Microcystin-LR promotes proliferation by activating Akt/S6K1 pathway and disordering apoptosis and cell cycle associated proteins phosphorylation in HL7702 cells.
Our previous studies had shown that MC-LR inhibited PP2A activity and hyperphosphorylated PP2A substrates at 24 h exposure in HL7702 cells. Although the cytoskeleton was rearranged, the cellular effects were not observed. The purpose of the present study with HL7702 cell exposed to MC-LR for 1-72 h was to further uncover the adverse effects of MC-LR comprehensively. The results showed that there were no obvious difference in apoptosis rate and cell-cycle distribution but the cell proliferation was changed since 36 h exposure while the uptake of MC-LR and its binding to PP2A/C kept unchanged since 1h exposure. PP2A activity had not manifested continued decline compare to 24h exposure and PP2A regulator α4 was found to release its associated PP2A/C since 1h exposure. The increasing of p-Akt-T308, p-Akt-S473, p-S6K1, p-S6, and p-4E-BP1 since 1h MC-LR exposure indicated that Akt/S6K1 cascade had been activated as early as 1h MC-LR treatment. And, PI3K/Akt inhibitor (LY294002) blocked MC-LR-induced Akt/S6K1 activation and proliferation. Besides, MC-LR also led to hyperphosphorylation of c-Myc, c-Jun, Bcl-2 and Bad and activation of Cdk1. Our study indicated that MC-LR exposure promoted HL7702 cell proliferation and the main mechanism was the activation of Akt/S6K1 cascade. Meanwhile, hyperphosphorylation of Bcl-2, Bad, c-Myc and c-Jun might also be involved. And, the inhibition of PP2A was the major reason for these molecular changes.
Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China.
Jinghui
J
Liu
Toxicology Program in the Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195, USA.
Hao
H
Wang
Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China.
Beilei
B
Wang
Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China.
Tao
T
Chen
Zhejiang Center for Disease Control and Prevention, Hangzhou 310051, China.
Xiaofeng
X
Wang
Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China.
Pu
P
Huang
Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China. Electronic address: xulihong@zju.edu.cn.
Lihong
L
Xu
Department of Biosystem Engineering, College of Biosystem Engineering and Food Science, Zhejiang University, Hangzhou 310058, China. Electronic address: zlguo@zju.edu.cn.
Zonglou
Z
Guo
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D006801:Humans; D008387:Marine Toxins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D052998:Microcystins / Q000633:toxicity*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics* / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D008387:Marine Toxins; D008565:Membrane Proteins; D052998:Microcystins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D054648:Protein Phosphatase 2; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C087000:EIF4EBP1 protein, human; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; C057862:cyanoginosin LR
Akt/S6K1; Microcystin-LR; PP2A; Proliferation; α4