title: Lamin B phosphorylation by protein kinase calpha and proteolysis during apoptosis in human leukemia HL60 cells.
abstract: Protein phosphorylation plays an important role in signal transduction, but its involvement in apoptosis still remains unclear. In this report, the p53-null human leukemia HL60 cells were used to investigate phosphorylation and degradation of lamin B during apoptosis. We found that lamin B was phosphorylated within 1 h after addition of the DNA topoisomerase I inhibitor, camptothecin, and that lamin B phosphorylation preceded lamin B degradation and DNA fragmentation. Using a cell-free system we also found that cytosol from camptothecin-treated cells induced lamin B phosphorylation and degradation in isolated nuclei from untreated HL60 cells. Lamin B phosphorylation was prevented by the protein kinase C (PKC) inhibitor 7-hydroxystaurosporine (UCN-01) but not by the Cdc2 inhibitor, flavopiridol. Phosphorylation of lamin B was inhibited by immunodepletion of PKCalpha from activated cytosol and was restored by addition of purified PKCalpha. PKCalpha activity also increased rapidly as lamin B was phosphorylated after initiation of the apoptotic response in HL60 cells. These data suggest that lamin B is phosphorylated by PKCalpha and proteolyzed before DNA fragmentation in HL60 cells undergoing apoptosis.
authors.affiliation: Laboratory of Molecular Pharmacology, Division of Basic Sciences, NCI, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
authors.forename: T
authors.initials: T
authors.lastname: Shimizu
authors.forename: C X
authors.initials: CX
authors.lastname: Cao
authors.forename: R G
authors.initials: RG
authors.lastname: Shao
authors.forename: Y
authors.initials: Y
authors.lastname: Pommier
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D003374:Coumarins / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D018922:HL-60 Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D049934:Isocoumarins; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D034921:Lamin Type B; D034882:Lamins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D017433:Protein Structure, Secondary; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013997:Time Factors; D059004:Topoisomerase I Inhibitors; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency
chemical_list: D003374:Coumarins; D049934:Isocoumarins; D007527:Isoenzymes; D034921:Lamin Type B; D034882:Lamins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D015842:Serine Proteinase Inhibitors; D059004:Topoisomerase I Inhibitors; D016159:Tumor Suppressor Protein p53; C046235:3,4-dichloroisocoumarin; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D002166:Camptothecin