Regulation of both apoptosis and cell survival by the v-Src oncoprotein.
A number of oncogenes alter the regulation of the cell cycle and cell death, contributing to the altered growth of tumours. Expression of the v-Src oncoprotein in Rat-1 fibroblasts prevented cell cycle exit in response to growth factor withdrawal. Here we investigated whether survival of v-Src transformed cells in low serum is dependent on v-Src activity. We used a temperature sensitive v-Src to study the effect inactivating v-Src on transformed cells growing under low serum conditions. We found when we switched off v-Src the cells died by apoptosis characterised by activation of caspases and the stress-activated kinases, JNK (Jun N-terminal kinase) and p38 MAP (mitogen activated protein) kinase. We were able to prevent cell death by addition of serum or overexpression of Bcl-2. Thus v-Src transformed Rat-1 cells can be protected from apoptosis by serum, v-Src, or Bcl-2. We investigated how v-Src protects from apoptosis under these conditions. Amongst other effects, v-Src activates two kinases which have been shown to protect cells from apoptosis, phosphatidylinositol 3-kinase (PI3-K) and extracellular signal-regulated kinase (ERK1/2). We found that switching off v-Src led to a decrease in the activity of both PI3-K and ERK1/2, however, we found that adding a specific inhibitor of PI3-K (LY294002) to v-Src transformed Rat-1 cells grown in low serum induced apoptosis while a specific ERK kinase (MEK1) inhibitor (PD98059) had no effect. This suggests that v-Src protects from apoptosis under low serum conditions by activating PI3-K.
The Beatson Institute for Cancer Research, Glasgow, G61 1BD, UK. d.johnson@beatson.gla.ac.uk
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D
Johnson
M
M
Agochiya
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K
Samejima
W
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Earnshaw
M
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Frame
J
J
Wyke
D000818:Animals; D017209:Apoptosis; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology; D002460:Cell Line; D002461:Cell Line, Transformed; D002470:Cell Survival; D003470:Culture Media; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D012710:Serum Albumin, Bovine; D048051:p38 Mitogen-Activated Protein Kinases
D061945:Caspase Inhibitors; D003470:Culture Media; D019253:Proto-Oncogene Proteins c-bcl-2; D012710:Serum Albumin, Bovine; D015688:Oncogene Protein pp60(v-src); D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases