BmCBP Catalyzes the Acetylation of BmApoLp-II Protein and Regulates Its Stability in Silkworm, Bombyx mori

SIMPLE SUMMARY: Bombyx mori is an important economic insect and a model organism of Lepidoptera. Its hemolymph contains rich nutrient storage proteins, which participate in material transportation, immune regulation, and other physiological functions. Additionally, a large number of proteins in hemolymph can be acetylated. Apolipophorin-II is a kind of nutrition storage protein that can bind lipid substances. In the article, we confirm that the Bombyx mori acetyltransferase cyclic adenosine monophosphate response element binding protein (CREB) binding protein (CBP) can interact with the apolipophorin-II protein. Therefore, CBP protein, as an acetyltransferase, can catalyze the acetylation of apolipophorin-II protein and thus affect the stability of apolipophorin-II protein. Acetyltransferase CBP can affect the growth and development of insects. In general, the research on nutrition storage protein and CBP protein can develop a new direction for biological control and pest resistance in the future. ABSTRACT: Acetylation is an important and reversible post-translational modification (PTM) of protein, which is involved in many cellular physiological processes. In previous studies, lots of nutrient storage proteins were found to be highly acetylated in silkworms, and acetylation can improve the stability of these proteins. However, the related acetyltransferase was not involved. In the present work, a Bombyx mori nutrient storage protein, apolipophorin II (BmApoLp-II), was further confirmed to be acetylated, and the acetylation could improve its protein expression. Furthermore, RNAi and Co-IP showed that the acetyltransferase BmCBP was found to catalyze the acetylation modification of BmApoLp-II, and thus affect its protein expression. Meanwhile, it was proved that acetylation could improve the stability of the BmApoLp-II protein by completing its ubiquitination. These results lay a foundation for further study on the mechanism of regulating nutrition storage and hydrolysis utilization of storage proteins by BmCBP and the acetylation in the silkworm Bombyx mori.