The proto-oncogene Crk-II enhances apoptosis by a Ras-dependent, Raf-1/MAP kinase-independent pathway

Biochem Biophys Res Commun. 1997 May 29;234(3):616-20. doi: 10.1006/bbrc.1997.6641.


Human embryonic kidney 293 cells and 293 cells overexpressing different amounts of the adaptor protein Crk-II (ranging from 3- to 10-fold higher levels than the parental cell line) were examined for their ability to undergo apoptosis when maintained in control and serum-free (SF) medium. Parental 293 cells undergo apoptosis only when deprived of serum for prolonged periods of time (24-48 h). On the other hand, 293 cells overexpressing different levels of Crk-II present detectable levels of apoptosis as measured by DNA fragmentation when grown in control medium, with a marked increase when they are deprived of serum for 12-48 h. To determine the pathways involved in Crk-II-induced apoptosis, Crk-II overexpressing cells were transiently transfected with a dominant-negative Ras construct (N17-Ras). Compared to cells transfected with control vectors, the cells overexpressing N17-Ras presented lower levels of apoptosis when maintained in SF-medium. On the other hand, transient transfection of a dominant-negative Raf-1 construct (K375W-Raf-1) did not decrease apoptosis; slightly increasing DNA fragmentation levels were seen. Similar results were obtained when the cells were incubated in the presence of a MEK1 inhibitor. The results presented here suggest that overexpression of Crk-II induces apoptosis via a Ras-dependent, Raf-1/MEK1/ERK-independent pathway.

MeSH terms

  • Apoptosis / genetics*
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Line
  • Culture Media, Serum-Free
  • Genes, Dominant
  • Humans
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-crk
  • Proto-Oncogene Proteins c-raf


  • Culture Media, Serum-Free
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-crk
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Calcium-Calmodulin-Dependent Protein Kinases