School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, China.
Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhenjiang, China.
Insect Mol Biol. 2020 Feb;29(1):66-76. doi: 10.1111/imb.12610. Epub 2019 Jul 30.
Storage proteins are haemolymph-specific proteins in insects, mainly synthesized in the fat body, released into the haemolymph, and then selectively reabsorbed by the fat body before pupation. These storage proteins play an important role in insect metamorphosis and egg development. Some of these storage proteins are responsive to pathogen infection and can even suppress pathogen multiplication. However, the mechanisms of the physiological, biochemical and immune-responsive functions of storage proteins remain unclear. In this study, the expression patterns of Bombyx mori storage protein 1 (BmSP1) during the larval stage were analysed. Then, BmSP1 protein fused with enhanced green fluorescent protein (EGFP) was successfully expressed in a B. mori baculovirus vector expression system. Quantitative real-time PCR showed that the expression level of BmSP1 increased with the advance of instars and reached the highest level in the fifth instar, especially in the fat body. Recombinant BmSP1 expressed in silkworm larvae inhibited haemolymph melanization. Then, proteins that interact with BmSP1 were identified with EGFP used as an antigenic determinant by co-immunoprecipitation. A 30 kDa low molecular weight lipoprotein PBMHP-6 precursor (BmLP6) was shown to interact with BmSP1. Yeast two-hybrid experiments confirmed the interaction between BmSP1 and BmLP6. The results obtained in this study will be helpful for further study of the functions of BmSP1 and BmLP6 in the regulatory network of silkworm development and innate immunity.
贮藏蛋白是昆虫血淋巴中的特异性蛋白，主要在脂肪体中合成，释放到血淋巴中，然后在化蛹前被脂肪体选择性地再吸收。这些贮藏蛋白在昆虫变态和卵发育中起着重要作用。其中一些贮藏蛋白对病原体感染有反应，甚至可以抑制病原体的繁殖。然而，贮藏蛋白的生理、生化和免疫反应功能的机制尚不清楚。本研究分析了家蚕贮藏蛋白 1（BmSP1）在幼虫期的表达模式。然后，成功地在家蚕杆状病毒载体表达系统中表达了与增强型绿色荧光蛋白（EGFP）融合的 BmSP1 蛋白。实时定量 PCR 显示，BmSP1 的表达水平随龄期的增加而增加，在第五龄期达到最高水平，特别是在脂肪体中。在蚕幼虫中表达的重组 BmSP1 抑制血淋巴黑化。然后，通过共免疫沉淀，使用 EGFP 作为抗原决定簇鉴定与 BmSP1 相互作用的蛋白质。结果表明，一种 30kDa 低分子量脂蛋白 PBMHP-6 前体（BmLP6）与 BmSP1 相互作用。酵母双杂交实验证实了 BmSP1 和 BmLP6 之间的相互作用。本研究的结果将有助于进一步研究 BmSP1 和 BmLP6 在蚕发育和先天免疫调控网络中的功能。
