An enhanced expression of the immediate early gene, Egr-1, is associated with neuronal apoptosis in culture.
Cultured cerebellar granule cells grown in medium containing 10 mM K+ (K10) underwent apoptosis after four to five days in vitro, unless they were rescued by the addition of insulin-like growth factor-I. The few GABAergic neurons present in the cultures were more resistant to apoptotic degeneration, as indicated by double fluorescent staining with the chromatin dye Hoechst 33258 and with glutamate decarboxylase-67 antibodies. As compared with sister cultures grown in 25 mM K+, K10 cultures showed an increased expression of the Egr-1 protein and a reduced expression of the Fos protein. The increase in Egr-1 was more substantial in granule cells than in GABAergic neurons, and was not observed in K10 cultures chronically exposed to insulin-like growth factor-I. To examine the temporal relationship between the increase in Egr-1 and the development of programmed cell death, we induced apoptosis in K25 cultures at six days in vitro by replacing their medium with serum-free K10 medium. A substantial, but transient, increase in Egr- expression was observed in granule cells 6 h after switching the medium, a time that preceded the appearance of the phenotypical markers of apoptotic death. An early reduction in the Fos protein was observed after switching the medium from K25 into serum-free K10, but also after switching the medium into serum-free K25, a condition which was not associated with the development of apoptosis nor with the increase in Egr-1. We suggest that a transient induction of Egr-1 contributes to the chain of events leading to the execution phase of neuronal apoptosis in culture.
Catania
M V
MV
I.B.F.S.N.C.-C.N.R., Catania, Italy.
Copani
A
A
Calogero
A
A
Ragonese
G I
GI
Condorelli
D F
DF
Nicoletti
F
F
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D003470:Culture Media / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D051766:Early Growth Response Protein 1; D015870:Gene Expression / Q000502:physiology*; D017781:Genes, Immediate-Early / Q000235:genetics*; D017874:Immediate-Early Proteins; D009474:Neurons / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D003470:Culture Media; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D016760:Proto-Oncogene Proteins c-fos; D014157:Transcription Factors