title: Proliferation arrest and induction of CDK inhibitors p21 and p27 by depleting the calcium store in cultured C6 glioma cells.
abstract: C6 glioma - Ca2+ depletion - proliferation arrest morphology change - CDK inhibitor In this study, we investigated the role of the intracellular calcium store in modulating the cellular proliferation and the expression of cell cycle regulatory proteins in cultured C6 glioma cells. By means of microspectrofluorimetry and Ca(2+)-sensitive indicator fura-2, we found that the intracellular Ca2+ pump inhibitors, thapsigargin (TG) irreversibly and 2,5-ditert-butyl-hydroquinone (DBHQ) reversibly depleted the Ca(2+)-store accompanied with the induction of G0/G1 arrest, an increase in glial fibrillary acidic protein (GFAP) expression and morphological changes from a round flat shape to a differentiated spindle-shaped cell. The machinery underlying these changes induced by Ca(2+)-store depletion was investigated. The results indicated that Ca(2+)-store depletion caused an increased expression of p21 and p27 proteins (cyclin-dependent kinase inhibitors), with unchanged mutant p53 protein of C6 cells but reduced amounts of the cell cycle regulators: cyclin-dependent kinase 2 (CDK2), cdc2, cyclin C, cyclin D1, cyclin D3 and proliferating cell nuclear antigen (PCNA) in a time-dependent manner. These findings indicate a new function of the endoplasmic reticulum (ER) Ca2+ store in regulating cellular proliferation rate through altering the expression of p21 and p27 proteins. Moreover, cellular differentiation as revealed by spindle-shaped morphology and induced GFAP expression were also modulated by the ER Ca2+ store. The implication of this finding is that the abnormal growth of cancer cells such as C6 glioma cells may be derived from a signalling of the ER which can be manipulated by depleting the Ca2+ store.
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Chen
authors.forename: J K
authors.initials: JK
authors.lastname: Lin
authors.forename: S Y
authors.initials: SY
authors.lastname: Lin-Shiau
mesh_terms: D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D019938:Cyclin D1 / Q000378:metabolism; D056743:Cyclin D3; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005910:Glioma / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D008840:Microfilament Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C534696:CCND3 protein, human; C493956:CDKN1A protein, human; C534697:Ccnd3 protein, mouse; D056743:Cyclin D3; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D005904:Glial Fibrillary Acidic Protein; D006873:Hydroquinones; D008840:Microfilament Proteins; D009124:Muscle Proteins; C058992:Tagln protein, mouse; D016159:Tumor Suppressor Protein p53; D019938:Cyclin D1; C019359:2,5-di-tert-butylhydroquinone; D019284:Thapsigargin; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D000252:Calcium-Transporting ATPases