The Proto-oncogene Crk-II Enhances Apoptosis by a Ras-Dependent, Raf-1/MAP Kinase-Independent Pathway

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 29...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 1997-05, Vol.234 (3), p.616-620
Main Authors: Parrizas, Marcelina, Blakesley, Vicky A., Beitner-Johnson, Dana, Roith, Derek Le
Format: Article
Language:English
Subjects:
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
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Summary: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.
ISSN:0006-291X
1090-2104
DOI:10.1006/bbrc.1997.6641