Department of Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Proc Natl Acad Sci U S A. 2010 Jan 12;107(2):742-7. doi: 10.1073/pnas.0907967107. Epub 2009 Dec 22.
Autophagy is a catabolic pathway that is important for turnover of long-lived proteins and organelles, and has been implicated in cell survival, tumor progression, protection from infection, neurodegeneration, and cell death. Autophagy and caspases are required for type II autophagic cell death of Drosophila larval salivary glands during development, but the mechanisms that regulate these degradation pathways are not understood. We conducted a forward genetic screen for genes that are required for salivary gland cell death, and here we describe the identification of Drosophila dynein light chain 1 (ddlc1) as a gene that is required for type II cell death. Autophagy is attenuated in ddlc1 mutants, but caspases are active in these cells. ddlc1 mutant salivary glands develop large fibrillar protein inclusions that stain positive for amyloid-specific dyes and ubiquitin. Ectopic expression of Atg1 is sufficient to induce autophagy, clear protein inclusions, and rescue degradation of ddlc1 mutant salivary glands. Furthermore, ddlc1 mutant larvae have decreased motility, and mutations in ddlc1 enhance the impairment of motility that is observed in a Drosophila model of neurodegenerative disease. Significantly, this decrease in larval motility is associated with decreased clearance of protein with polyglutamine expansion, the accumulation of p62 in neurons and muscles, and fewer synaptic boutons. These results indicate that DDLC1 is required for protein clearance by autophagy that is associated with autophagic cell death and neurodegeneration.
自噬是一种重要的分解代谢途径，可促进长寿命蛋白质和细胞器的更新，并且与细胞存活、肿瘤进展、抗感染、神经退行性变和细胞死亡有关。自噬和胱天蛋白酶对于果蝇幼虫唾液腺发育过程中的 II 型自噬性细胞死亡是必需的，但是调节这些降解途径的机制尚不清楚。我们进行了正向遗传筛选，以鉴定在唾液腺细胞死亡中必需的基因，在此我们描述了鉴定出果蝇动力蛋白轻链 1 (ddlc1)是 II 型细胞死亡所必需的基因。ddlc1 突变体中的自噬受到抑制，但这些细胞中的胱天蛋白酶是活跃的。ddlc1 突变体的唾液腺会产生大的纤维状蛋白包涵体，这些包涵体对淀粉样蛋白特异性染料和泛素呈阳性染色。Atg1 的异位表达足以诱导自噬、清除蛋白包涵体，并挽救 ddlc1 突变体唾液腺的降解。此外，ddlc1 突变体幼虫的运动能力下降，并且 ddlc1 突变增强了在神经退行性疾病的果蝇模型中观察到的运动能力受损。重要的是，幼虫运动能力的下降与聚谷氨酰胺扩展的蛋白清除减少、神经元和肌肉中 p62 的积累以及突触小泡减少有关。这些结果表明，DDLC1 是与自噬性细胞死亡和神经退行性变相关的自噬蛋白清除所必需的。
