Vol.:(0123456789) 1 3 Molecular and Cellular Biochemistry https://doi.org/10.1007/s11010-019-03513-y Acetylation of BmAtg8 inhibits starvation-induced autophagy initiation Shengjie Xue 1,2  · Fuxiang Mao 1,2  · Dongbing Hu 1,2  · Huihui Yan 1,2  · Jihai Lei 1,2  · Enoch Obeng 1,2  · Yuefan Zhou 1,2  · Yanping Quan 1,2  · Wei Yu 1,2 Received: 24 October 2018 / Accepted: 23 February 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Silkworm (Bombyx mori) is not only a model organism for scientifc studies, but also a commercial insect for agricultural pro- duction. BmAtg8 (a B. mori homolog of yeast Atg8) plays crucial roles in macroautophagy (hereafter referred to autophagy), which is helpful for silkworm metamorphosis. Relevant mechanism about BmAtg8 currently remains ambiguous. Based on our previous acetylome of B. mori after BmNPV infection, we focused on that acetylation of BmAtg8 K13 was changed upon virus challenge. Subsequently, anti-BmAtg8 antibody was generated, and EBSS-induced BmN cellular autophagy model was established. Next, by constructing acetylation-mimic K13Q or deacetylation-mimic K13R mutant BmAtg8, we further examined that K13 of BmAtg8 was acetylated after BmNPV infection and chose 3 h as an appropriate point after EBSS treatment for autophagy initiation. Furthermore, acetylation of BmAtg8 K13 signifcantly reduced BmAtg8-PE formation in the presence of EBSS, thereby interfering autophagy initiation. Interestingly, acetylated K13 of BmAtg8 contributed to weaken interaction with Atg7, which may infuence BmAtg8-PE conjugation. Eventually, acetylation of BmAtg8 K13 is critical for attenuating cell rescue through impaired autophagy initiation. Taken together, our data support an acetylated molecular function for BmAtg8 during starvation-induced autophagy, and provide insights into the modulating mechanisms that potentially reveal the LC3 (a mammalian homolog of Atg8) function in mammal. Keywords BmAtg8 · Acetylation · Starvation · Autophagy · Cell death Introduction Silkworm (Bombyx mori) is not only a Lepidopteran insect with great economic value by producing silk, but also a model organism with biological significance for scien- tifc researches [1]. Macroautophagy (hereafter referred to autophagy) is a self-digestion process for recycling impaired macromolecules and damaged organelles to replenish energy and building blocks [2–4]. Importantly, autophagy also plays essentially physiological roles in silkworm metamorphosis via degeneration of silk glands and guts, as well as restruc- turing fat bodies [5–7]. BmAtg8 (a homolog of yeast Atg8 or mammalian LC3) is a core element of autophagy initiation and assembles other autophagy-related proteins to accomplish the elon- gation of autophagosomal membranes [8–11]. In mam- malian, LC3 and GABARAP family are homologs of yeast Atg8, whereas they have diferent physiological activities in autophagy [12, 13]. In Drosophila, two Atg8 orthologs, Atg8a and Atg8b, show high sequence similarity and are localized in autophagy vesicles, whereas only Atg8a is nec- essary for autophagosome formation [14]. Interestingly, a single Atg8 homolog, B. mori Atg8 (BmAtg8), is highly homologous to other insect Atg8 orthologs [15]. Atg8 is a ubiquitin-like protein that mediates protein lipidation with phosphatidylethanolamine (PE) by E1-like enzyme Atg7 and E2-like protein Atg3 [8]. BmAtg8-PE is only localized in membranes and lipidation of the BmAtg8 is required for p62 body associated with autophagic degradation [16, 17]. Based Shengjie Xue and Fuxiang Mao contributed equally to this work. * Wei Yu mikkyu@163.com 1 Institute of Biochemistry, College of Life Sciences, Zhejiang Sci-Tech University, Xiasha High-Tech Zone No. 2 Road, Hangzhou 310018, Zhejiang, People’s Republic of China 2 Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, Hangzhou 310018, Zhejiang, People’s Republic of China