Bcl-2 does not require Raf kinase activity for its death-protective function

Biochem J. 1997 May 15;324 ( Pt 1)(Pt 1):75-83. doi: 10.1042/bj3240075.

Abstract

It has been widely accepted that the oncogene product bcl-2 protects mammalian cells from programmed cell death (apoptosis). The molecules and signalling pathways upon which bcl-2 acts are, however, still ill-defined. Recently, bcl-2 was shown to interact with c-raf-1 in vitro. Furthermore, an active form of c-raf-1 delayed apoptosis induced by trophic factor deprivation and enhanced the death-suppressive function of bcl-2 when co-expressed. This has led to the hypothesis that bcl-2 communicates cell-death protection via a raf-dependent signal transduction pathway. Here we show, by various immunological and biochemical methods, that bcl-2 does not stably associate with c-raf-1 in cellular extracts prepared from fibroblasts before or after treatment with agents that induce apoptosis. Unexpectedly, bcl-2 function is entirely maintained, if not improved, when raf-dependent signalling is experimentally abrogated. In fact, bcl-2 allows the stable overexpression of a kinase-defective dominant-negative raf mutant that usually interferes with cell viability and/or proliferation. Our results indicate that bcl-2 does not require c-raf-1 kinase activity and an associated mitogen-activated protein kinase signalling pathway for its survival function. This property may be exploited to dissect cellular events that are dependent or independent of c-raf-1 kinase activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis*
  • Brefeldin A
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cell Division
  • Cell Survival
  • Cells, Cultured
  • Chloramphenicol O-Acetyltransferase / biosynthesis
  • Cloning, Molecular
  • Cyclic AMP / pharmacology
  • Cyclopentanes / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Fibroblasts
  • Humans
  • Kinetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Proto-Oncogene Proteins c-raf
  • Rats
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction
  • Staurosporine / pharmacology
  • Transfection

Substances

  • Cyclopentanes
  • Enzyme Inhibitors
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Recombinant Fusion Proteins
  • Brefeldin A
  • Cyclic AMP
  • Chloramphenicol O-Acetyltransferase
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Staurosporine