Presence of a Putative Vesicular Inositol 1,4,5-Trisphosphate-Sensitive Nucleoplasmic Ca2+ Store

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• 作者：Yang Hoon Huh ; Seong Kwon Huh ; Sei Yoon Chu ; Hee Seok Kweon ; and Seung Hyun Yoo
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：February 7, 2006
• 年：2006
• 卷：45
• 期：5
• 页码：1362 - 1373
• 全文大小：1047K
• 年卷期：v.45,no.5(February 7, 2006)
• ISSN：1520-4995

文摘

The inositol 1,4,5-trisphosphate receptors (IP₃Rs) are widely localized in both the heterochromatin and euchromatin regions. We found recently the presence of nucleoplasmic complexes that arecomposed of phospholipids, IP₃R/Ca²⁺ channels, and Ca²⁺ storage protein chromogranin B (CGB). Closeexamination and 3D image reconstruction of these complexes revealed numerous vesicular structureswith an average diameter of ~50 nm that are primarily interspersed between the heterochromatins. IP₃rapidly released Ca²⁺ from these structures, but other inositol phosphates, inositol 1,4-bisphosphate, inositol1,3,4-trisphosphate, and inositol 1,3,4,5-tetrakisphosphate, failed to release Ca²⁺. Addition of heparin orIP₃R antibody blocked the IP₃-induced Ca²⁺ releases, indicating the release of Ca²⁺ through the IP₃R/Ca²⁺ channels. Given the presence of the IP₃R/Ca²⁺ channels and Ca²⁺ storage protein CGB in thesevesicular structures, we postulate that these vesicles are the IP₃-sensitive nucleoplasmic Ca²⁺ stores.Abundance of the vesicular Ca²⁺ stores between the heterochromatins appeared to imply critical rolesthese vesicular Ca²⁺ stores play in controlling the Ca²⁺ concentrations of the chromosomes.