Trophic support promotes survival of bcl-x-deficient telencephalic cells in vitro.
Survival of immature neurons is regulated by Bcl-xL, as targeted disruption of bcl-x significantly increases cell death in vivo and in vitro. Death of cultured bcl-x-deficient and wild-type telencephalic cells can be prevented by fetal calf serum or chemically-defined medium (ITS), suggesting trophic factors in these media potentiate survival through a pathway independent of Bcl-xL. Addition of trophic factors to basal medium revealed that insulin and insulin-like growth factors (IGFs), but not other trophic factors, reduced apoptosis of wild-type and bcl-x-deficient telencephalic cells. Antibodies raised against IGF-I receptors and wortmannin both attenuated the effects of IGF-I, indicating survival was mediated by IGF-I receptors and phosphatidylinositol 3'-kinase signaling, whereas effects of ITS were only partially reduced by these agents. The survival promoting effects of ITS were reduced in cells lacking both bcl-x and bcl-2, indicating Bcl-2 plays a supportive role to Bcl-xL in maintaining telencephalic cell survival. Furthermore, the ratio of expression of the pro-apoptotic bax gene to the anti-apoptotic bcl-2 gene was reduced in bcl-x-deficient cultures grown in ITS, suggesting that the interaction between these bcl-2 family members may, in part, regulate a Bcl-xL independent survival pathway. Finally, the pro-apoptotic bad gene does not appear to play a role in these interactions as targeted disruption of bad did not alter apoptosis in telencephalic cultures.
Shindler
K S
KS
Department of Pathology, Washington. University School of Medicine, St Louis, Missouri 63110, USA.
Yunker
A M
AM
Cahn
R
R
Zha
J
J
Korsmeyer
S J
SJ
Roth
K A
KA
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D003470:Culture Media; D016895:Culture Media, Serum-Free; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017526:Receptor, IGF Type 1 / Q000276:immunology / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013687:Telencephalon / Q000166:cytology* / Q000502:physiology; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
D000906:Antibodies; C494819:BAD protein, human; C494811:BCL2L1 protein, human; C494820:Bad protein, mouse; C494812:Bcl2l1 protein, mouse; D002352:Carrier Proteins; D003470:Culture Media; D016895:Culture Media, Serum-Free; D006133:Growth Substances; D007328:Insulin; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1