Abstract: Objective To examine the impact of c-jun on thapsigargin-induced mouse fibroblasts survival and its mechanism. Methods Thapsigargin, pCMV-CnA and pSRα-HA-c-jun were used to treat c-jun-/- and c-jun Re mouse fibroblasts. Cell viability was evaluated with trypan blue dye exclusion. Calcineurin assays were performed according to the manufacturers instructions. c-jun, p-c-jun, JNK, p-JNK, Adapt78 and α-tubulin were analyzed with immunoblotting. Results TG treatment led to strong JNK activation and phosphorylation of c-jun in c-jun Re cells. We observed a higher level of calcineurin activity in c-jun-/- cells compared with c-jun Re cells(P<0.05). TG treatment resulted in significantly increased calcineurin activity in c-jun-/- cells but not in c-jun Re cells. Exogenous expression of calcineurin via pCMV-CnA caused increased Adapt78 expression in both c-jun-/- and c-jun Re cells, although TG treatment induced Adapt78 expression only in c-jun Re cells. Adapt78 expression induced by pCMV-CnA in c-jun-/- cells was associated with protection against TG-induced cell death. Overexpression of exogenous c-jun in c-jun-/- cells caused both an autophosphorylation of c-jun in the target cells and exogenous expression of c-jun recovered thapsigargin-induced Adapt78 up-regulation and inhibited TG-induced cell death. Conclusion The change of c-jun gene expression level can affect TG-induced mouse cell survival rate. The changes of calcineurin and Adapt78 protein expression are related to the 山 东 大 学 学 报 (医 学 版)54卷2期 -张洁,等.原癌基因c-jun对毒胡萝卜素内酯处理的小鼠胚胎成纤维细胞生存率的影响 \=-alteration of c-jun gene expression. The increased c-jun gene expression results in enhanced expression of Adapt78 protein, thus weakens the calcineurin activity and produces protective mechanism against TG-induced cell death.

Key words: Calcineurin, Adapt78 protein, Cell survival rate, c-jun gene