Medical Research Council Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Anatomy and Developmental Biology Department, University College London, London, United Kingdom.
PLoS One. 2012;7(2):e31488. doi: 10.1371/journal.pone.0031488. Epub 2012 Feb 8.
Apoptosis, a genetically programmed cell death, allows for homeostasis and tissue remodelling during development of all multi-cellular organisms. Phagocytes swiftly recognize, engulf and digest apoptotic cells. Yet, to date the molecular mechanisms underlying this phagocytic process are still poorly understood. To delineate the molecular mechanisms of apoptotic cell clearance in Drosophila, we have carried out a deficiency screen and have identified three overlapping phagocytosis-defective mutants, which all delete the fly homologue of the ced-12 gene, known as Dmel\ced12. As anticipated, we have found that Dmel\ced-12 is required for apoptotic cell clearance, as for its C. elegans and mammalian homologues, ced-12 and elmo, respectively. However, the loss of Dmel\ced-12 did not solely account for the phenotypes of all three deficiencies, as zygotic mutations and germ line clones of Dmel\ced-12 exhibited weaker phenotypes. Using a nearby genetically interacting deficiency, we have found that the polycystic kidney disease 2 gene, pkd2, which encodes a member of the TRPP channel family, is also required for phagocytosis of apoptotic cells, thereby demonstrating a novel role for PKD2 in this process. We have also observed genetic interactions between pkd2, simu, drpr, rya-r44F, and retinophilin (rtp), also known as undertaker (uta), a gene encoding a MORN-repeat containing molecule, which we have recently found to be implicated in calcium homeostasis during phagocytosis. However, we have not found any genetic interaction between Dmel\ced-12 and simu. Based on these genetic interactions and recent reports demonstrating a role for the mammalian pkd-2 gene product in ER calcium release during store-operated calcium entry, we propose that PKD2 functions in the DRPR/RTP pathway to regulate calcium homeostasis during this process. Similarly to its C. elegans homologue, Dmel\Ced-12 appears to function in a genetically distinct pathway.
细胞凋亡是一种基因程序性细胞死亡，允许所有多细胞生物在发育过程中保持体内平衡和组织重塑。吞噬细胞能够迅速识别、吞噬和消化凋亡细胞。然而，迄今为止，吞噬细胞吞噬凋亡细胞的分子机制仍知之甚少。为了阐明果蝇中凋亡细胞清除的分子机制，我们进行了缺失筛选，并鉴定了三个重叠的吞噬缺陷突变体，它们都缺失了 fly 同源物 ced-12 基因，称为 Dmel\ced12。正如预期的那样，我们发现 Dmel\ced-12 对于凋亡细胞的清除是必需的，就像它的 C. elegans 和哺乳动物同源物 ced-12 和 elmo 一样。然而，Dmel\ced-12 的缺失并不能完全解释这三个缺陷的表型，因为 zygotic 突变和 Dmel\ced-12 的生殖系克隆表现出较弱的表型。使用附近的遗传相互作用缺陷，我们发现多囊肾病 2 基因 pkd2，它编码 TRPP 通道家族的成员，也需要吞噬凋亡细胞，从而证明 PKD2 在这个过程中有一个新的作用。我们还观察到 pkd2、simu、drpr、rya-r44F 和 retinophilin (rtp)之间的遗传相互作用，也称为 undertaker (uta)，这是一个编码含有 MORN 重复的分子的基因，我们最近发现它在吞噬过程中参与钙稳态。然而，我们没有发现 Dmel\ced-12 和 simu 之间有任何遗传相互作用。基于这些遗传相互作用和最近的报告，证明了哺乳动物 pkd-2 基因产物在储存操作钙进入期间内质网钙释放中的作用，我们提出 PKD2 在 DRPR/RTP 途径中发挥作用，以调节该过程中的钙稳态。类似于它的 C. elegans 同源物，Dmel\Ced-12 似乎在一个遗传上不同的途径中发挥作用。
