Exp Mol Med.  2008 Aug;40(4):435-444. 10.3858/emm.2008.40.4.435.

Repeated electroconvulsive seizure induces c-Myc down-regulation and Bad inactivation in the rat frontal cortex

• Jeon WJ
• Kim SH
• Seo MS
• Kim Y
• Kang UG
• Juhnn YS
• Kim YS

• KMID: 1094123
• DOI: http://doi.org/10.3858/emm.2008.40.4.435

Abstract

Repeated electroconvulsive seizure (ECS), a model for electroconvulsive therapy (ECT), exerts neuroprotective and proliferative effects in the brain. This trophic action of ECS requires inhibition of apoptotic activity, in addition to activation of survival signals. c-Myc plays an important role in apoptosis of neurons, in cooperation with the Bcl-2 family proteins, and its activity and stability are regulated by phosphorylation and ubiquitination. We examined c-Myc and related proteins responsible for apoptosis after repeated ECS. In the rat frontal cortex, repeated ECS for 10 days reduced the total amount of c-Myc, while increasing phosphorylation of c-Myc at Thr58, which reportedly induces degradation of c-Myc. As expected, ubiquitination of both phosphorylated and total c-Myc increased after 10 days ECS, suggesting that ECS may reduce c-Myc protein level via ubiquitination-proteasomal degradation. Bcl-2 family proteins, caspase, and poly(ADP-ribose) polymerase (PARP) were investigated to determine the consequence of down-regulating c-Myc. Protein levels of Bcl-2, Bcl-X(L), Bax, and Bad showed no change, and cleavage of caspase-3 and PARP were not induced. However, phosphorylation of Bad at Ser-155 and binding of Bad to 14-3-3 increased without binding to Bcl-X(L) after repeated ECS, implying that repeated ECS sequesters apoptotic Bad and frees pro-survival Bcl-X(L). Taken together, c-Myc down-regulation via ubiquitination-proteasomal degradation and Bad inactivation by binding to 14-3-3 may be anti-apoptotic mechanisms elicited by repeated ECS in the rat frontal cortex. This finding further supports the trophic effect of ECS blocking apoptosis as a possible therapeutic effect of ECT.

Keyword

apoptosis; bcl-2-associated X protein; electroconvulsive therapy; nerve growth factors; proto-oncogene proteins c-bcl-2; proto-oncogene proteins c-myc; ubiquitination

MeSH Terms

14-3-3 Proteins/metabolism
Animals
Down-Regulation
Electroconvulsive Therapy/*adverse effects
Frontal Lobe/*metabolism
Male
Models, Biological
Neurons/metabolism
Periodicity
Phosphorylation
Protein Binding
Protein Processing, Post-Translational
Proto-Oncogene Proteins c-bcl-2/metabolism
Proto-Oncogene Proteins c-myc/*metabolism
Rats
Rats, Sprague-Dawley
Seizures/etiology/*metabolism
Tumor Cells, Cultured
Ubiquitination
bcl-Associated Death Protein/antagonists & inhibitors/*metabolism