Tip60 Phosphorylation at Ser 99 Is Essential for Autophagy Induction in Bombyx mori

Abstract

Tip60, a key histone acetyltransferase of the MYST family and member of the nuclear multimeric protein complex (NuA4), regulates the activity and stability of proteins involved in the cell cycle, DNA damage responses, autophagy, etc. However, the function and regulatory mechanism of Tip60 homolog in Bombyx mori are not elucidated. In the present study, Bombyx Tip60 (BmTip60) was functionally identified. Developmental profiles showed that the protein levels and nuclear localization of BmTip60 peaked in fat body during the larval–pupal metamorphosis when autophagy was intensive; simultaneously, the BmTip60 protein migrated to form an upper band as detected by Western blot. Interestingly, the upper band of BmTip60 was reduced by λ-phosphatase treatment, indicating that it was a phosphorylated form of BmTip60. Results showed that BmTip60 was promoted by starvation but not 20-hydroxyecdysone treatment. Transcription factor AMP-activated protein kinase (AMPK) affected by starvation was pivotal for BmTip60 protein migration. In addition, one mammalian phosphorylation site was identified in BmTip60 at Ser99, the constitutive-activation mutation of Ser99 to Asp99 but not its inactive mutation to Ala99 significantly upregulated autophagy, showing the critical role of phosphorylation at Ser99 for BmTip60-mediated autophagy. In conclusion, the starvation-AMPK axis promotes BmTip60 in B. mori, which was requisite for autophagy induction. These results reveal a regulatory mechanism of histone acetyltransferase Tip60 homologs by phosphorylation in insects, and sheds light on further related studies of acetylation regulation.

Lactate‐induced protein lactylation: A bridge between epigenetics and metabolic reprogramming in cancer

“…The level of histone acetylation is positively correlated with the level of acetyl‐CoA, and as we have already described, metabolite concentrations closely affect protein modification levels, which also occur in many other metabolite substrate phenomena 87–89 . A variety of HATs have been identified, including three main families, which are p300/CBP, GNAT (Gcn5‐related N‐acetyltransferase) and MYST family 90–93 . The removal of acetyl groups (erasers) relies on lysine deacetylase, which balances the activity of HATs, including two families, histone deacetylases (HDACs) and sirtuins, 94,95 inhibition of which has been found to result in a worse prognosis 96 .…”

“… 87 , 88 , 89 A variety of HATs have been identified, including three main families, which are p300/CBP, GNAT (Gcn5‐related N‐acetyltransferase) and MYST family. 90 , 91 , 92 , 93 The removal of acetyl groups (erasers) relies on lysine deacetylase, which balances the activity of HATs, including two families, histone deacetylases (HDACs) and sirtuins, 94 , 95 inhibition of which has been found to result in a worse prognosis. 96 The acetyl group attached to the specific residue of the histone can neutralize the positive charge it carries and increase its hydrophobicity, thereby reducing the affinity of the histone with DNA, loosening the chromatin, making the DNA in it more accessible for transcriptional factor, thus promoting gene expression.…”

Protein modification regulated autophagy in Bombyx mori and Drosophila melanogaster

“…Starvation-induced AMPK activation leads to the phosphorylation of Tip60 at Ser99, which is essential for autophagy induction in B. mori. This mechanism is conserved in lepidopterans and mammals but may not be in other insects (Wu et al, 2020). 20E plays a crucial role in promoting programmed cell death (PCD) by modulating PGK1, a key glycolytic enzyme (Matsui et al, 2012).…”

Correction: Wu, W., et al. Tip60 Phosphorylation at Ser 99 Is Essential for Autophagy Induction in Bombyx mori. Int. J. Mol. Sci. 2020, 21, 6893

“…The author wishes to make the following correction to this paper [ 1 ]. Due to an error involving the immunofluorescent staining for BmAtg8 after starvation treatment in Figure 4E, it should be replaced with the correct new figure ( Figure 1 ).…”