Presence of a putative vesicular inositol 1,4,5-trisphosphate-sensitive nucleoplasmic Ca2+ store.
The inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are widely localized in both the heterochromatin and euchromatin regions. We found recently the presence of nucleoplasmic complexes that are composed of phospholipids, IP(3)R/Ca(2+) channels, and Ca(2+) storage protein chromogranin B (CGB). Close examination and 3D image reconstruction of these complexes revealed numerous vesicular structures with an average diameter of approximately 50 nm that are primarily interspersed between the heterochromatins. IP(3) rapidly released Ca(2+) from these structures, but other inositol phosphates, inositol 1,4-bisphosphate, inositol 1,3,4-trisphosphate, and inositol 1,3,4,5-tetrakisphosphate, failed to release Ca(2+). Addition of heparin or IP(3)R antibody blocked the IP(3)-induced Ca(2+) releases, indicating the release of Ca(2+) through the IP(3)R/Ca(2+) channels. Given the presence of the IP(3)R/Ca(2+) channels and Ca(2+) storage protein CGB in these vesicular structures, we postulate that these vesicles are the IP(3)-sensitive nucleoplasmic Ca(2+) stores. Abundance of the vesicular Ca(2+) stores between the heterochromatins appeared to imply critical roles these vesicular Ca(2+) stores play in controlling the Ca(2+) concentrations of the chromosomes.
Huh
Yang Hoon
YH
National Creative Research Initiative Center for Secretory Granule Research and Department of Biochemistry, Inha University College of Medicine, Jung Gu, Incheon 400-712, Korea.
Huh
Seong Kwon
SK
Chu
Sei Yoon
SY
Kweon
Hee Seok
HS
Yoo
Seung Hyun
SH
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D019439:Chromaffin Cells / Q000378:metabolism; D002864:Chromogranins / Q000378:metabolism; D006046:Gold / Q000737:chemistry; D021621:Imaging, Three-Dimensional / Q000379:methods; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D046529:Microscopy, Electron, Transmission; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D013997:Time Factors
D015220:Calcium Channels; D002864:Chromogranins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D046912:Multiprotein Complexes; D019269:Phosphatidylinositol 4,5-Diphosphate; D010743:Phospholipids; D018160:Receptors, Cytoplasmic and Nuclear; D006046:Gold; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium