Hu Jia-Huan, Cheng Xiao-Yu, Li Jin-Xin, Xue Bin, Tian Jiang-Hai, Hu Jing-Sheng, Li Bing
School of Basic Medicine and Biological Sciences, Soochow University, Suzhou, Jiangsu, P.R. China.
National Engineering Laboratory for Modern Silk, Soochow University, Suzhou, Jiangsu, P.R. China.
Arch Insect Biochem Physiol. 2018 May;98(1):e21450. doi: 10.1002/arch.21450. Epub 2018 Feb 5.
Bombyx mori is an economic insect of the Lepidoptera. Its posterior silk gland (PSG) is an important organ for fibroin synthesis. In order to study the occurrence of apoptosis in PSG and the role of PI3K/Akt signaling pathway during spinning period, changes in morphology of silk gland, expressions of fibroin components Fib-H, Fib-L and P25 and Akt, TOR2, P70S6K and S6 in PI3K/Akt pathway, expressions of apoptosis related genes caspase-3, caspase-9 and activity of caspase-3 were explored. The results showed that the morphology of silk gland dramatically degenerated; transcription of Fib-H, Fib-L, and P25 gradually declined with time; and Fib-L protein level reduced by 0.6-fold at 72 h. Moreover, the transcription levels of Akt, TOR2, P70S6K, and S6 also decreased by 0.3-, 0.8-, 0.7-, and 0.1-fold, respectively, indicating that the downregulation of PI3K/Akt signaling pathway could lead to reduction in fibroin synthesis. In addition, the transcription levels of caspase-3 and caspase-9 increased by 1.3- and 3.6-fold, respectively, and the enzyme activity of caspase-3 grew at a maximum of 1.6-fold. The results showed the occurrence of apoptosis in PSG during spinning period. In conclusion, the present study indicated that both the decline in fibroin components and the increase in apoptosis-related genes were regulated by PI3K/Akt signaling pathway during spinning period, which shed new light on the functions of PI3K/Akt signaling pathway.
家蚕是鳞翅目的一种经济昆虫。其后部丝腺（PSG）是合成丝心蛋白的重要器官。为了研究吐丝期PSG中细胞凋亡的发生情况以及PI3K/Akt信号通路的作用，探讨了丝腺形态的变化、丝心蛋白组分Fib-H、Fib-L和P25以及PI3K/Akt通路中Akt、TOR2、P70S6K和S6的表达情况，以及凋亡相关基因caspase-3、caspase-9的表达和caspase-3的活性。结果表明，丝腺形态显著退化；Fib-H、Fib-L和P25的转录随时间逐渐下降；Fib-L蛋白水平在72小时时降低了0.6倍。此外，Akt、TOR2、P70S6K和S6的转录水平分别下降了0.3倍、0.8倍、0.7倍和0.1倍，表明PI3K/Akt信号通路的下调可能导致丝心蛋白合成减少。此外，caspase-3和caspase-9的转录水平分别增加了1.3倍和3.6倍，caspase-3的酶活性最高增长了1.6倍。结果表明吐丝期PSG中发生了细胞凋亡。综上所述，本研究表明吐丝期丝心蛋白组分的下降和凋亡相关基因的增加均受PI3K/Akt信号通路调控，这为PI3K/Akt信号通路的功能提供了新的线索。
