The Role of Calcium in Cadmium Induced Metallothionein Gene Expression

• Main Authors: Ya-Chuan Liu, 劉雅娟
• Other Authors: Lih-Yuan Lin, Ph.D.
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/86363954710801171327

碩士 === 國立清華大學 === 生命科學系 === 90 === Abstract Metallothioneins (MTs) are small molecular-weight proteins that could be induced by heavy metals. MTs are involved in the metal detoxification. In our study, we observed that cadmium (Cd) induced MT mRNA expression and increased the cytosolic calcium (Ca2+) in GH3 cells. By using chemicals increasing intracellular Ca2+ content, such as A23187, ionomycin or thapsgargin, and intracellular Ca2+ chelator, PBAPTA-AM, we found that Cd-induced MT mRNA was affected by intracellular Ca2+ concentration. We also observed that H7, a non-specific PKC inhibitor, abrogated MT mRNA induction after Cd treatment. However using specific inhibitors of various PKC isoforms, only PKCδ inhibitor, rottlerin reduced MT gene expression. The PKCδ activity increased after Cd treatment. Rottlerin not only inhibited Cd-induced MT mRNA, but also attenuated the accumulation of intracellular Cd. We also found that calmodulin antagonist, W7 decreased the Cd-induced MT mRNA. When using the inhibitor KN93 to further investigate the effect of Ca2+/calmodulin dependent protein kinaseⅡ on MT gene expression, we found that KN93 partially inhibited MT gene expression. After GH3 exposed to Cd, CaMKⅡ activity increased and reached the highest level within 3 minutes. We conclude that Cd-induced MT gene expression is through the increase of cytosolic Ca2+, and activation of PKCδ and CaMKⅡ.