Regulation of tissue transglutaminase by prolonged increase of intracellular Ca2+, but not by initial peak of transient Ca2+ increase |
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Authors: | Yoo Je-Ok Yi Sun-Ju Choi Hyun Jung Kim Woo Jin Kim Young-Myeong Han Jeong-A Ha Kwon-Soo |
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Institution: | Department of Molecular and Cellular Biochemistry, Kangwon National University College of Medicine, Chunchon, Republic of Korea. |
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Abstract: | Tissue transglutaminase (tTGase) is a member of calcium-dependent transamidation enzyme family, but a detailed regulation mechanism of tTGase by intracellular Ca(2+) is not clearly understood. Arachidonic acid (AA) and maitotoxin (MTX) activated tTGase in a dose- and time-dependent manner. Transfection of tTGase siRNA largely inhibited tTGase expression and tTGase activation by MTX. AA induced an initial increase of intracellular Ca(2+) followed by a prolonged increase. Removal of extracellular Ca(2+) with EGTA blocked the prolonged Ca(2+) increase in response to AA, although the initial Ca(2+) increase remained. In contrast, EGTA completely blocked the increase of intracellular Ca(2+) by MTX. The activation of tTGase by AA or MTX was significantly inhibited by EGTA. Moreover, EGTA prevented the prolonged increase of intracellular Ca(2+) and tTGase activation by lysophosphatidic acid, but had no effect on the initial Ca(2+) increase. These results suggested that tTGase is regulated by the prolonged increase of intracellular Ca(2+) originated from Ca(2+) influx, rather than by the initial peak of transient Ca(2+) increase. |
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Keywords: | Tissue transglutaminase Intracellular Ca2+ Arachidonic acid Maitotoxin Lysophosphatidic acid |
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