University of Glasgow, UK.
Cell Signal. 2010 May;22(5):737-48. doi: 10.1016/j.cellsig.2009.12.009. Epub 2010 Jan 11.
Organismal stress responses to oxidative stress are relevant to ageing and disease and involve key cell-/tissue-specific signal transduction mechanisms. Using Drosophila, an established in vivo model for stress studies, we show that cell-specific inositol phosphate signalling specifically via inositol 1,4,5 trisphosphate 3-kinase (InsP(3) 3-K, IP(3)K), negatively regulates organismal responses to oxidative stress. We demonstrate that the Drosophila Malpighian tubule (equivalent to vertebrate kidney and liver) is a key epithelial sensor for organismal oxidative stress responses: precise targeting of either gain-of-function constructs of Drosophila IP(3)Ks (IP(3)K-1 and IP(3)K-2), or loss-of-function (RNAi) constructs to only one cell type in tubule reversibly modulates survival of stress-challenged adult flies. In vivo, targeted IP(3)K-1 directly increases H(2)O(2) production, pro-apoptotic caspase-9 activity and mitochondrial membrane potential. The mitochondrial calcium load in tubule principal cells-assessed by luminescent and fluorescent genetically-encoded mitochondrial calcium reporters-is significantly increased by IP(3)K-1 under oxidative stress conditions, leading to apoptosis. The Drosophila orthologues of human apoptotic bcl-2 genes include debcl and buffy. Oxidative stress challenge does not modulate gene expression of either debcl or buffy in tubules; and altered debcl expression does not influence survival rates under oxidative stress challenge. Finally, targeted over-expression of either debcl or buffy to tubule principal cells does not impact on tubule caspase-9 activity. Thus, IP(3)K-1 modulates epithelial cell apoptosis without involvement of bcl-2-type proteins.
生物体对氧化应激的应激反应与衰老和疾病有关，涉及关键的细胞/组织特异性信号转导机制。我们利用果蝇作为应激研究的成熟体内模型，表明细胞特异性肌醇磷酸盐信号转导，特别是通过肌醇 1,4,5 三磷酸 3-激酶（InsP（3）3-K，IP（3）K），负调控生物体对氧化应激的反应。我们证明果蝇的马氏管（相当于脊椎动物的肾脏和肝脏）是生物体氧化应激反应的关键上皮传感器：果蝇 IP（3）K（IP（3）K-1 和 IP（3）K-2）的功能获得构建体或失活构建体（RNAi）仅靶向马氏管中的一种细胞类型，可可逆地调节应激挑战成年果蝇的存活率。在体内，靶向 IP（3）K-1 直接增加 H（2）O（2）的产生、促凋亡半胱氨酸蛋白酶-9 活性和线粒体膜电位。马氏管主细胞中的线粒体钙负荷-通过发光和荧光遗传编码线粒体钙报告器评估-在氧化应激条件下被 IP（3）K-1 显著增加，导致细胞凋亡。人类凋亡 bcl-2 基因的果蝇同源物包括 debcl 和 buffy。氧化应激挑战不会调节 debcl 或 buffy 在马氏管中的基因表达；并且 debcl 表达的改变不会影响氧化应激挑战下的存活率。最后，靶向过表达 debcl 或 buffy 到马氏管主细胞不会影响马氏管 caspase-9 活性。因此，IP（3）K-1 调节上皮细胞凋亡而不涉及 bcl-2 型蛋白。
