Sun Chang, Wei Dongmei, Pan Yumeng, Xiao Xiaoyi, Wang Fei
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Biological Science Research Center, Southwest University, Chongqing, China.
Insect Sci. 2023 Apr;30(2):365-374. doi: 10.1111/1744-7917.13109. Epub 2022 Sep 13.
Autophagy plays an important role in tissue remodeling during insect development. The interplay between autophagy-related (ATG) proteins and caspases regulates the autophagic activity of ATGs, thereby modulating the process of autophagy. Our previous study characterized BmCaspase-8-like (BmCasp8L) as a caspase suppressor that inhibits apoptosis and immune signaling by suppressing the activation of death-related ced-3/Nedd2-like caspase (DREDD), a caspase-8 homolog in silkworm. In this study, we explored the regulatory role of BmCasp8L in autophagy. We found that the expression of Bmcasp8l increased from the late spinning stage to the pupa stage in the posterior silk gland (PSG), correlating with the expression patterns of Bmatg8 and Bmatg6. RNA interference-mediated downregulation of BmCasp8L expression significantly decreased starvation-induced autophagic influx as determined by the levels of BmATG8-phosphatidylethanolamine and the percentage of cells displaying punctate enhanced green fluorescent protein-BmATG8. Conversely, the overexpression of BmCasp8L significantly increased autophagic influx. We also found that BmCasp8L underwent autophagic degradation induced by starvation and that it was colocalized with BmATG8. Lastly, we demonstrated that BmDREDD attenuated autophagy and BmCasp8L suppressed BmDREDD-mediated cleavage of BmATG6. Taken together, our results demonstrated that BmCasp8L is a novel proautophagic molecule which suppresses BmDREDD-mediated cleavage of BmATG6 and is a target for autophagy.
自噬在昆虫发育过程中的组织重塑中发挥着重要作用。自噬相关（ATG）蛋白与半胱天冬酶之间的相互作用调节ATG的自噬活性，从而调控自噬过程。我们之前的研究将家蚕类半胱天冬酶-8（BmCasp8L）鉴定为一种半胱天冬酶抑制因子，它通过抑制家蚕中与死亡相关的ced-3/Nedd2样半胱天冬酶（DREDD，一种半胱天冬酶-8同源物）的激活来抑制细胞凋亡和免疫信号传导。在本研究中，我们探究了BmCasp8L在自噬中的调控作用。我们发现，在后部丝腺（PSG）中，Bmcasp8l的表达从吐丝后期到蛹期增加，这与Bmatg8和Bmatg6的表达模式相关。RNA干扰介导的BmCasp8L表达下调显著降低了饥饿诱导的自噬流入，这是通过BmATG8-磷脂酰乙醇胺水平和显示点状增强绿色荧光蛋白-BmATG8的细胞百分比来确定的。相反，BmCasp8L的过表达显著增加了自噬流入。我们还发现BmCasp8L经历了饥饿诱导的自噬降解，并且它与BmATG8共定位。最后，我们证明BmDREDD减弱自噬，而BmCasp8L抑制BmDREDD介导的BmATG6的切割。综上所述，我们的结果表明BmCasp8L是一种新型的促自噬分子，它抑制BmDREDD介导的BmATG6的切割，并且是自噬的一个靶点。
