Proteolytic cleavage of protein kinase Cmu upon induction of apoptosis in U937 cells

FEBS Lett. 1999 Dec 3;462(3):442-6. doi: 10.1016/s0014-5793(99)01577-x.


Treatment of U937 cells with various apoptosis-inducing agents, such as TNFalpha and beta-D-arabinofuranosylcytosine (ara-C) alone or in combination with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), bryostatin 1 or cycloheximide, causes proteolytic cleavage of protein kinase Cmu (PKCmu) between the regulatory and catalytic domain, generating a 62 kDa catalytic fragment of the kinase. The formation of this fragment is effectively suppressed by the caspase-3 inhibitor Z-DEVD-FMK. In accordance with these in vivo data, treatment of recombinant PKCmu with caspase-3 in vitro results also in the generation of a 62 kDa fragment (p62). Treatment of several aspartic acid to alanine mutants of PKCmu with caspase-3 resulted in an unexpected finding. PKCmu is not cleaved at one of the typical cleavage sites containing the motif DXXD but at the atypical site CQND378/S379. The respective fragment (amino acids 379-912) was expressed in bacteria as a GST fusion protein (GST-p62) and partially purified. In contrast to the intact kinase, the fragment does not respond to the activating cofactors TPA and phosphatidylserine and is thus unable to phosphorylate substrates effectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Bryostatins
  • Caspase 3
  • Caspases / metabolism*
  • Cell-Free System
  • Cycloheximide / pharmacology
  • Cytarabine / pharmacology
  • Fructose-Bisphosphate Aldolase / metabolism
  • Humans
  • Lactones / pharmacology
  • Macrolides
  • Oligopeptides / pharmacology
  • Protein Kinase C / metabolism*
  • Recombinant Proteins / metabolism
  • Time Factors
  • Tumor Necrosis Factor-alpha / pharmacology
  • U937 Cells


  • Bryostatins
  • Lactones
  • Macrolides
  • Oligopeptides
  • Recombinant Proteins
  • Tumor Necrosis Factor-alpha
  • benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone
  • Cytarabine
  • bryostatin 1
  • Cycloheximide
  • protein kinase D
  • Protein Kinase C
  • CASP3 protein, human
  • Caspase 3
  • Caspases
  • Fructose-Bisphosphate Aldolase