The growth-promoting activity of the Bad protein in chicken embryo fibroblasts requires binding to protein 14-3-3.
Phosphorylation of the Bad protein is a key regulatory event in the prevention of apoptosis by survival factors. Phosphorylated Bad binds to the cytosolic 14-3-3 protein and is sequestered from the apoptotic machinery of the mitochondrial membrane. To examine the role of Bad in cell growth and apoptosis in primary cultures, we produced stable Bad transfectants of chicken embryo fibroblasts (CEF). As expected, serum starvation of Bad transfectants promoted apoptosis. However, Bad-transfected CEF maintained in media with a high serum concentration were capable of anchorage-independent growth and grew to a higher saturation density than control CEF transfected with the empty vector. High dilutions of the infectious retroviral vector RCAS expressing Bad led to the formation of multilayered cell foci. The growth-promoting effects of Bad were dependent on the serine 136 phosphorylation site and correlated directly with binding of Bad to 14-3-3. These results suggest that phosphorylated Bad promotes cell growth and in oncogenic transformation may contribute to the neoplastic phenotype of the cell.
Maslyar
D J
DJ
Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, BCC239 La Jolla, California, USA.
Aoki
M
M
Vogt
P K
PK
D048948:14-3-3 Proteins; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology*; D002455:Cell Division; D002642:Chick Embryo; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D008928:Mitochondria / Q000378:metabolism; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D013997:Time Factors; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*; D051025:bcl-Associated Death Protein
D048948:14-3-3 Proteins; D002352:Carrier Proteins; D016895:Culture Media, Serum-Free; D051025:bcl-Associated Death Protein; D014446:Tyrosine 3-Monooxygenase; D019869:Phosphatidylinositol 3-Kinases; D019908:Proto-Oncogene Proteins c-raf