Lamin B phosphorylation by protein kinase calpha and proteolysis during apoptosis in human leukemia HL60 cells

J Biol Chem. 1998 Apr 10;273(15):8669-74. doi: 10.1074/jbc.273.15.8669.

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.

MeSH terms

  • Amino Acid Sequence
  • Apoptosis* / drug effects
  • Camptothecin / pharmacology
  • Cell Nucleus / metabolism
  • Coumarins / pharmacology
  • Cytosol / metabolism
  • DNA Fragmentation
  • HL-60 Cells / cytology
  • HL-60 Cells / metabolism*
  • Humans
  • Isocoumarins
  • Isoenzymes / metabolism*
  • Kinetics
  • Lamin Type B
  • Lamins
  • Molecular Sequence Data
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / metabolism*
  • Peptide Fragments / chemistry
  • Phosphorylation
  • Protein Kinase C / metabolism*
  • Protein Kinase C-alpha
  • Protein Structure, Secondary
  • Serine Proteinase Inhibitors / pharmacology
  • Time Factors
  • Topoisomerase I Inhibitors
  • Tumor Suppressor Protein p53 / deficiency

Substances

  • Coumarins
  • Isocoumarins
  • Isoenzymes
  • Lamin Type B
  • Lamins
  • Nuclear Proteins
  • Peptide Fragments
  • Serine Proteinase Inhibitors
  • Topoisomerase I Inhibitors
  • Tumor Suppressor Protein p53
  • 3,4-dichloroisocoumarin
  • PRKCA protein, human
  • Protein Kinase C
  • Protein Kinase C-alpha
  • Camptothecin