title: Role of nuclear chromogranin B in inositol 1,4,5-trisphosphate-mediated nuclear Ca2+ mobilization.
abstract: Recently, secretory granule Ca(2+) storage protein chromogranin B (CGB) was shown to be present in the nucleoplasm proper in a complex structure that consists of the inositol 1,4,5-trisphosphate receptor (IP(3)R)/Ca(2+) channels and the phospholipids. Further, the amounts of IP(3)Rs present in the nucleus of bovine chromaffin cells were shown to be comparable to that of the endoplasmic reticulum. Therefore, we investigated here the potential contribution of nuclear CGB on the IP(3)-dependent Ca(2+) mobilization in the nucleus, using both neuroendocrine PC12 and nonneuroendocrine NIH3T3 cells. Chromogranin A (CGA) expression in the NIH3T3 cells, which do not contain intrinsic chromogranins, increased the IP(3)-induced Ca(2+) releases in the nucleus by 45%, while CGB expression in the same cells increased the IP(3)-induced Ca(2+) releases in the nucleus by 80%. Microinjection of IP(3) into the nucleus of CGB-expressing NIH3T3 cells increased the IP(3)-dependent nuclear Ca(2+) mobilization approximately 3-fold, whereas in CGA-expressing cells it remained the same as that of control cells. In contrast, inhibition of CGA expression in PC12 cells by siRNA treatment decreased the IP(3)-induced Ca(2+) releases in the nucleus by 17%, while inhibition of CGB expression decreased the IP(3)-induced Ca(2+) releases in the nucleus by 55%. Microinjection of IP(3) into the nucleus of siCGB-treated PC12 cells decreased the IP(3)-dependent nuclear Ca(2+) mobilization by approximately 75%, whereas in siCGA-treated cells it remained the same as that of control cells. Given the presence of CGB in the nucleus, these results further highlight the critical contribution of nuclear CGB in the IP(3)-induced Ca(2+) release in the nucleus.
authors.affiliation: National Creative Research Initiative Center for Secretory Granule Research and Department of Biochemistry, Inha University College of Medicine, Jung Gu, Incheon 400-712, Korea.
authors.forename: Yang Hoon
authors.initials: YH
authors.lastname: Huh
authors.forename: Sei Yoon
authors.initials: SY
authors.lastname: Chu
authors.forename: Seon Young
authors.initials: SY
authors.lastname: Park
authors.forename: Seong Kwon
authors.initials: SK
authors.lastname: Huh
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Yoo
mesh_terms: D000255:Adenosine Triphosphate / Q000819:agonists / Q000378:metabolism; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism*; D053379:Chromogranin A; D053378:Chromogranin B; D002864:Chromogranins / Q000378:metabolism / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008845:Microinjections; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D041681:NIH 3T3 Cells; D016716:PC12 Cells; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D053379:Chromogranin A; D053378:Chromogranin B; D002864:Chromogranins; D011994:Recombinant Proteins; C506137:chromogranin B, mouse; C506140:chromogranin B, rat; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate