Conversion of CD95 (Fas) Type II into Type I signaling by sub-lethal doses of cycloheximide

Exp Cell Res. 2008 Feb 1;314(3):554-63. doi: 10.1016/j.yexcr.2007.11.003. Epub 2007 Nov 17.

Abstract

CD95 (Fas/Apo-1)-mediated apoptosis was shown to occur through two distinct pathways. One involves a direct activation of caspase-3 by large amounts of caspase-8 generated at the DISC (Type I cells). The other is related to the cleavage of Bid by low concentration of caspase-8, leading to the release of cytochrome c from mitochondria and the activation of caspase-3 by the cytochrome c/APAF-1/caspase-9 apoptosome (Type II cells). It is also known that the protein synthesis inhibitor cycloheximide (CHX) sensitizes Type I cells to CD95-mediated apoptosis, but it remains contradictory whether this effect also occurs in Type II cells. Here, we show that sub-lethal doses of CHX render both Type I and Type II cells sensitive to the apoptogenic effect of anti-CD95 antibodies but not to chemotherapeutic drugs. Moreover, Bcl-2-positive Type II cells become strongly sensitive to CD95-mediated apoptosis by the addition of CHX to the cell culture. This is not the result of a restraint of the anti-apoptotic effect of Bcl-2 at the mitochondrial level since CHX-treated Type II cells still retain their resistance to chemotherapeutic drugs. Therefore, CHX treatment is granting the CD95-mediated pathway the ability to bypass the mitochondria requirement to apoptosis, much alike to what is observed in Type I cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies / pharmacology
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Apoptosis Regulatory Proteins / antagonists & inhibitors
  • Apoptosis Regulatory Proteins / metabolism*
  • BH3 Interacting Domain Death Agonist Protein / drug effects
  • BH3 Interacting Domain Death Agonist Protein / metabolism
  • Caspases / drug effects
  • Caspases / metabolism
  • Cycloheximide / pharmacology
  • Cytochromes c / drug effects
  • Cytochromes c / metabolism
  • Dose-Response Relationship, Drug
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / physiology
  • Drug Synergism
  • HL-60 Cells
  • Humans
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Protein Synthesis Inhibitors / pharmacology
  • Proto-Oncogene Proteins c-bcl-2 / drug effects
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • fas Receptor / antagonists & inhibitors
  • fas Receptor / metabolism*

Substances

  • Antibodies
  • Antineoplastic Agents
  • Apoptosis Regulatory Proteins
  • BH3 Interacting Domain Death Agonist Protein
  • BID protein, human
  • Protein Synthesis Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • fas Receptor
  • Cytochromes c
  • Cycloheximide
  • Caspases