Molecular Genetic basis of neural selection by cell death during development and pathological condition

程序性细胞死亡和神经变性发生在大脑中。为了阐明神经细胞死亡的机制，包括神经变性，我们开发了一种新的筛选基因参与神经细胞死亡与神经变性，涉及过表达的个别基因在整个果蝇基因组（GS筛选）。作为筛选约5000个果蝇品系的结果，我们鉴定并表征了endd2基因，其编码位于内质网中的果蝇的Sec61 α（DSec61 α）的直系同源物，作为神经细胞死亡和退化途径的新组分。然后，我们进行了一个显性修饰筛选的收割机识别神经细胞死亡相关基因使用一组缺陷株，覆盖超过70%的果蝇基因组。在该筛选中，我们将DmIKK ε鉴定为Reaper诱导的细胞死亡途径中的候选组分。DmIKK ε在GS筛选中也被确定为神经细胞死亡促进基因的候选基因。生化研究表明DmIKK ε通过直接磷酸化促进果蝇IAP（DIAP 1）的降解。DmIKK ε的失活导致DIAP 1积累而不影响发育性细胞死亡。DmIKK ε是一种DIAP 1降解激酶，其调节DIAP 1的内源性水平，DIAP 1进而通过体内半胱天冬酶的非凋亡功能调节神经细胞命运。

Programmed cell death and neurodegeneration occur in the brain. To elucidate the mechanisms of neural cell death including neurodegeneration, we developed a novel screen for genes involved in the neuronal cell death associated with neurodegeneration, involving the overexpression of individual genes throughout much of the Drosophila genome (GS screening). As a result of the screen of approximately 5000 fly strains, we identified and characterized the endd2 gene, which encodes the Drosophila ortholog of Sec61α (DSec61α) located in endoplasmic reticulum, as a new component of the neural cell death and degeneration pathways. We then performed a dominant-modifier screen of reaper for identification of neural-cell death related genes using a set of deficiency strains that cover more than 70% of the Drosophila genome. In this screening, we identified DmIKKε as a candidate component in the pathway of Reaper-induced cell death. DmIKKε was also identified as a candidate gene of neural cell death promoting gene in GS screening. Biochemical studies indicated that DmIKKε that promotes degradation of Drosophila IAP (DIAP 1) through direct phosphorylation. Inactivation of DmIKKε causes DIAP 1 accumulation without affecting developmental cell death. DmIKKε is a DIAP 1-degrading kinase that regulates endogenous levels of DIAP 1, which in turn regulates neural cell fate through non-apoptotic functions of caspases in vivo.