Histone deacetylases (HDACs) are important for global gene expression and contribute to numerous physiological events. Deacetylase Rpd3 in yeast and its conserved homolog HDAC1 in mammals oppositely regulate autophagy; however, how Rpd3/HDAC1 is regulated to mediate autophagy remains unclear. Here, we showed autophagy occurrence in silkworm (Bombyx mori) required BmRpd3, wherein steroid hormone 20-hydroxyecdysone (20E) signaling regulated its protein level and nuclear localization negatively. Inhibition of MTOR led to dephosphorylation and nucleo-cytoplasmic translocation of BmRpd3/HsHDAC1. Besides, cholesterol, 20E, and 27-hydroxycholesterol could all induce massive dephosphorylation and cytoplasmic localization of BmRpd3/HsHDAC1, and thus autophagy by affecting MTORC1 activity. In addition, three phosphorylation sites (Ser392, Ser421, and Ser423) identified in BmRpd3 were conserved in HsHDAC1. Single or triple phosphorylation-site mutation attenuated the phosphorylation levels of BmRpd3/HsHDAC1, leading to their cytoplasmic localization and autophagy activation. In general, cholesterol derivatives, especially hydroxylated cholesterol, caused dephosphorylation and nucleo-cytoplasmic shuttling of BmRpd3/HsHDAC1 through inhibition of MTOR signaling to facilitate autophagy in B. mori and mammals. These findings improve our understandings of BmRpd3/HsHDAC1-mediated autophagy induced by cholesterol derivatives and shed light on their potential as a therapeutic target for neurodegenerative diseases and autophagy-related studies.Abbreviations: 20E: 20-hydroxyecdysone; 27-OH: 27-hydroxycholesterol; ACTB: actin beta; AMPK: AMP-activated protein kinase; Atg: autophagy-related; BmSqstm1: Bombyx sequestosome 1; CQ: chloroquine; HDAC: histone deacetylase; LMNB: Lamin B1; MTOR: mechanistic target of rapamycin kinase; PE: phosphatidylethanolamine; SQSTM1/p62: sequestosome 1; TUBA1A: tubulin alpha 1a.

中文翻译：

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胆固醇衍生物诱导组蛋白去乙酰化酶 Rpd3/HDAC1 的去磷酸化以上调自噬。

组蛋白去乙酰化酶 (HDAC) 对全局基因表达很重要，并有助于许多生理事件。酵母中的去乙酰化酶 Rpd3 及其在哺乳动物中的保守同源物 HDAC1 反向调节自噬；然而，如何调节 Rpd3/HDAC1 介导自噬仍不清楚。在这里，我们发现家蚕 (Bombyx mori) 需要 BmRpd3 发生自噬，其中类固醇激素 20-羟基蜕皮激素 (20E) 信号传导负面调节其蛋白质水平和核定位。MTOR 的抑制导致 BmRpd3/HsHDAC1 的去磷酸化和核质易位。此外，胆固醇、20E 和 27-羟基胆固醇都可以通过影响 MTORC1 活性来诱导 BmRpd3/HsHDAC1 的大量去磷酸化和细胞质定位，从而导致自噬。此外，三个磷酸化位点（Ser392、Ser421、在 BmRpd3 中鉴定的 Ser423) 在 HsHDAC1 中是保守的。单个或三个磷酸化位点突变减弱了 BmRpd3/HsHDAC1 的磷酸化水平，导致它们的细胞质定位和自噬激活。通常，胆固醇衍生物，尤其是羟基化胆固醇，通过抑制 MTOR 信号传导促进 B. mori 和哺乳动物的自噬，引起 BmRpd3/HsHDAC1 的去磷酸化和核质穿梭。这些发现提高了我们对胆固醇衍生物诱导的 BmRpd3/HsHDAC1 介导的自噬的理解，并阐明了它们作为神经退行性疾病和自噬相关研究的治疗靶点的潜力。缩写：20E：20-羟基蜕皮激素；27-OH：27-羟基胆固醇；ACTB：肌动蛋白β；AMPK：AMP 活化蛋白激酶；Atg：自噬相关；BmSqstm1：家蚕sequestosome 1; CQ：氯喹；HDAC：组蛋白脱乙酰酶；LMNB：Lamin B1；MTOR：雷帕霉素激酶的机制靶点；PE：磷脂酰乙醇胺；SQSTM1/p62：sequestosome 1；TUBA1A：微管蛋白α1a。