Kim Young-Il, Ryu Taewoo, Lee Judong, Heo Young-Shin, Ahnn Joohong, Lee Seung-Jae, Yoo OokJoon
Bio Medical Research Center, Department of Biological Science, KAIST, 373-1, 305-701, Daejeon, Korea.
BMC Cell Biol. 2010 Jan 25;11:9. doi: 10.1186/1471-2121-11-9.
Caspases are cysteine proteases with essential functions in the apoptotic pathway; their proteolytic activity toward various substrates is associated with the morphological changes of cells. Recent reports have described non-apoptotic functions of caspases, including autophagy. In this report, we searched for novel modifiers of the phenotype of Dcp-1 gain-of-function (GF) animals by screening promoter element- inserted Drosophila melanogaster lines (EP lines).
We screened approximately 15,000 EP lines and identified 72 Dcp-1-interacting genes that were classified into 10 groups based on their functions and pathways: 4 apoptosis signaling genes, 10 autophagy genes, 5 insulin/IGF and TOR signaling pathway genes, 6 MAP kinase and JNK signaling pathway genes, 4 ecdysone signaling genes, 6 ubiquitination genes, 11 various developmental signaling genes, 12 transcription factors, 3 translation factors, and 11 other unclassified genes including 5 functionally undefined genes. Among them, insulin/IGF and TOR signaling pathway, MAP kinase and JNK signaling pathway, and ecdysone signaling are known to be involved in autophagy. Together with the identification of autophagy genes, the results of our screen suggest that autophagy counteracts Dcp-1-induced apoptosis. Consistent with this idea, we show that expression of eGFP-Atg5 rescued the eye phenotype caused by Dcp-1 GF. Paradoxically, we found that over-expression of full-length Dcp-1 induced autophagy, as Atg8b-GFP, an indicator of autophagy, was increased in the eye imaginal discs and in the S2 cell line. Taken together, these data suggest that autophagy suppresses Dcp-1-mediated apoptotic cell death, whereas Dcp-1 positively regulates autophagy, possibly through feedback regulation.
We identified a number of Dcp-1 modifiers that genetically interact with Dcp-1-induced cell death. Our results showing that Dcp-1 and autophagy-related genes influence each other will aid future investigations of the complicated relationships between apoptosis and autophagy.
半胱天冬酶是在凋亡途径中具有重要功能的半胱氨酸蛋白酶；它们对各种底物的蛋白水解活性与细胞的形态变化相关。最近的报道描述了半胱天冬酶的非凋亡功能，包括自噬。在本报告中，我们通过筛选插入启动子元件的黑腹果蝇品系（EP品系）来寻找Dcp-1功能获得型（GF）动物表型的新型修饰因子。
我们筛选了约15,000个EP品系，鉴定出72个与Dcp-1相互作用的基因，这些基因根据其功能和途径分为10组：4个凋亡信号基因、10个自噬基因、5个胰岛素/胰岛素样生长因子和TOR信号通路基因、6个丝裂原活化蛋白激酶和JNK信号通路基因、4个蜕皮激素信号基因、6个泛素化基因、11个各种发育信号基因、12个转录因子、3个翻译因子以及11个其他未分类基因，包括5个功能未明的基因。其中，胰岛素/胰岛素样生长因子和TOR信号通路、丝裂原活化蛋白激酶和JNK信号通路以及蜕皮激素信号通路已知与自噬有关。连同自噬基因的鉴定，我们的筛选结果表明自噬可抵消Dcp-1诱导的凋亡。与此观点一致，我们表明eGFP-Atg5的表达挽救了由Dcp-1 GF引起的眼表型。矛盾的是，我们发现全长Dcp-１的过表达诱导了自噬，因为自噬指标Atg8b-GFP在眼成虫盘和S2细胞系中增加。综上所述，这些数据表明自噬抑制Dcp-1介导的凋亡细胞死亡，而Dcp-1可能通过反馈调节正向调节自噬。
我们鉴定出许多与Dcp-1诱导的细胞死亡发生遗传相互作用的Dcp-1修饰因子。我们的结果表明Dcp-1和自噬相关基因相互影响，这将有助于未来对凋亡与自噬之间复杂关系的研究。
