Fimia Gian Maria, Stoykova Anastassia, Romagnoli Alessandra, Giunta Luigi, Di Bartolomeo Sabrina, Nardacci Roberta, Corazzari Marco, Fuoco Claudia, Ucar Ahmet, Schwartz Peter, Gruss Peter, Piacentini Mauro, Chowdhury Kamal, Cecconi Francesco
National Institute for Infectious Diseases, IRCCS L. Spallanzani, 00149 Rome, Italy.
Nature. 2007 Jun 28;447(7148):1121-5. doi: 10.1038/nature05925. Epub 2007 Jun 24.
Autophagy is a self-degradative process involved both in basal turnover of cellular components and in response to nutrient starvation or organelle damage in a wide range of eukaryotes. During autophagy, portions of the cytoplasm are sequestered by double-membraned vesicles called autophagosomes, and are degraded after fusion with lysosomes for subsequent recycling. In vertebrates, this process acts as a pro-survival or pro-death mechanism in different physiological and pathological conditions, such as neurodegeneration and cancer; however, the roles of autophagy during embryonic development are still largely uncharacterized. Beclin1 (Becn1; coiled-coil, myosin-like BCL2-interacting protein) is a principal regulator in autophagosome formation, and its deficiency results in early embryonic lethality. Here we show that Ambra1 (activating molecule in Beclin1-regulated autophagy), a large, previously unknown protein bearing a WD40 domain at its amino terminus, regulates autophagy and has a crucial role in embryogenesis. We found that Ambra1 is a positive regulator of the Becn1-dependent programme of autophagy, as revealed by its overexpression and by RNA interference experiments in vitro. Notably, Ambra1 functional deficiency in mouse embryos leads to severe neural tube defects associated with autophagy impairment, accumulation of ubiquitinated proteins, unbalanced cell proliferation and excessive apoptotic cell death. In addition to identifying a new and essential element regulating the autophagy programme, our results provide in vivo evidence supporting the existence of a complex interplay between autophagy, cell growth and cell death required for neural development in mammals.
自噬是一种自我降解过程，参与多种真核生物细胞成分的基础更新以及对营养饥饿或细胞器损伤的应答。在自噬过程中，部分细胞质被称为自噬体的双膜囊泡隔离，并在与溶酶体融合后被降解以便后续循环利用。在脊椎动物中，这一过程在不同生理和病理状况（如神经退行性变和癌症）下发挥促生存或促死亡机制的作用；然而，自噬在胚胎发育过程中的作用仍很大程度上未被阐明。Beclin1（Becn1；卷曲螺旋、肌球蛋白样BCL2相互作用蛋白）是自噬体形成的主要调节因子，其缺失会导致胚胎早期致死。在此我们表明，Ambra1（Beclin1调控的自噬中的激活分子），一种在其氨基末端带有WD40结构域的大型未知蛋白，调节自噬并在胚胎发生中起关键作用。我们发现，Ambra1是Becn1依赖性自噬程序的正向调节因子，体外过表达和RNA干扰实验揭示了这一点。值得注意的是，小鼠胚胎中Ambra1功能缺陷会导致与自噬受损、泛素化蛋白积累、细胞增殖失衡和过度凋亡性细胞死亡相关的严重神经管缺陷。除了鉴定出调节自噬程序的一个新的必需元件外，我们的结果还提供了体内证据，支持哺乳动物神经发育所需的自噬、细胞生长和细胞死亡之间存在复杂相互作用。
