期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：5
页码：2975-2980
DOI：10.1073/pnas.0536590100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Nuclear calcium (Ca2+) regulates a number of important cellular processes, including gene transcription, growth, and apoptosis. However, it is unclear whether Ca2+ signaling is regulated differently in the nucleus and cytosol. To investigate this possibility, we examined subcellular mechanisms of Ca2+ release in the HepG2 liver cell line. The type II isoform of the inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) was expressed to a similar extent in the endoplasmic reticulum and nucleus, whereas the type III InsP3R was concentrated in the endoplasmic reticulum, and the type I isoform was not expressed. Ca2+ signals induced by low InsP3 concentrations started earlier or were larger in the nucleus than in the cytosol, indicating higher sensitivity of nuclear Ca2+ stores for InsP3. Nuclear InsP3R channels were active at lower InsP3 concentrations than InsP3R from cytosol. Enriched expression of type II InsP3R in the nucleus results in greater sensitivity of the nucleus to InsP3, thus providing a mechanism for independent regulation of Ca2+-dependent processes in this cellular compartment.
