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KMID : 0613820060160040598
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Journal of Life Science
2006 Volume.16 No. 4 p.598 ~ p.604
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Regulation of Cyclin D3 by Calpain Protease in Human Breast Carcinoma MDA-MB-231 Cells
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Choi Byung-Tae
Kim Kun-Do
Choi Yung-Hyun
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Abstract
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The Ca²?-activated neutral protease calpain induced proteolysis has been suggested to play a role in certain cell growth regulatory proteins. Cyclin proteolysis is essential for cell cycle progression. D-type cyclins, which form an assembly with cyclin-dependent kinases (cdk4 and cdk6), are synthesized earlier in G1 of the cell cycle and seem to be induced in response to external signals that promote entry into the cell cycle. Here we show that cyclin D3 protein levels are regulated at the posttranscriptional level by calpain protease. Treatment of human breast carcinoma MDA-MB-231 cells with lovastatin and actinomycin D resulted in a loss of cyclin D3 protein that was completely reversible by the peptide aldehyde calpain inhibitor, LLnL. The specific inhibitor of the 26S proteasome, lactacystin, the lysosome inhibitors, ammonium chloride and chloroquine, and the serine protease inhibitor, phenylmethylsulfonylfluoride (PMSF), did not block the degradation of cyclin D3 by lovastatin and actinomycin D. Results of in vitro degradation of cyclin D3 by purified calpain showed that cyclin D3 protein is degraded in a Ca²?-dependent manner, and the half-life of cyclin D3 protein was dramatically increased in LLnL treated cells. These data suggested that cyclin D3 protein is regulated by the Ca²?-activated protease calpain.
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KEYWORD
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Cyclin D3, proteolysis, calpain
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