The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, China.
Insect Mol Biol. 2012 Oct;21(5):521-34. doi: 10.1111/j.1365-2583.2012.01157.x. Epub 2012 Aug 9.
Insect haemocytes are known to participate in innate immunity via the phagocytosis of pathogens. However, the function of haemocytes in tissue remodelling is less understood. We report here that haemocytes play roles in fat body degradation by expressing a cysteine proteinase cathepsin L in the lepidopteran Helicoverpa armigera. During metamorphosis, haemocytes undergo morphological changes by increasing their cell size and transforming their granulocytes into macrogranulocytes. The population of haemocytes also changes with increased number of granulocytes and decreased plasmatocytes. The expression level of cathepsin L in haemocytes, mainly in granulocytes and plasmatocytes, increases. The steroid hormone 20-hydroxyecdysone is able to promote the transformation of granulocytes into macrogranulocytes, and up-regulate the expression level of cathepsin L. The knock-down of the cathepsin L gene by RNA interference in haemocytes in vitro results in deficient granulocytes transforming into macrogranulocytes. Haemocytes are able to enter the decomposed fat body during metamorphosis. The over-expression of the proteinase domain C1A of cathepsin L results in cell apoptosis. Haemocytes, especially macrogranulocytes, undergo apoptosis and cathepsin L is released into haemolymph and the fat body during metamorphosis for fat body decomposition and degradation. These results suggest that cathepsin L is related to the transformation of granulocytes to macrogranulocytes to enter the fat body, and induce haemocyte apoptosis for further tissue degradation.
昆虫血细胞被认为通过吞噬病原体参与先天免疫。然而，血细胞在组织重塑中的功能知之甚少。我们在这里报道，在鳞翅目昆虫棉铃虫中，血细胞通过表达半胱氨酸蛋白酶组织蛋白酶 L 参与脂肪体降解。在变态期间，血细胞通过增加细胞大小并将其粒细胞转化为大颗粒细胞来经历形态变化。血细胞的种群也随着粒细胞数量的增加和浆细胞数量的减少而变化。血细胞中组织蛋白酶 L 的表达水平增加，主要在粒细胞和浆细胞中。类固醇激素 20-羟基蜕皮酮能够促进粒细胞转化为大颗粒细胞，并上调组织蛋白酶 L 的表达水平。在体外通过 RNA 干扰敲低血细胞中的组织蛋白酶 L 基因导致粒细胞缺乏转化为大颗粒细胞。在变态期间，血细胞能够进入分解的脂肪体。蛋白酶结构域 C1A 的过表达导致细胞凋亡。在变态期间，血细胞，特别是大颗粒细胞，发生细胞凋亡，组织蛋白酶 L 释放到血淋巴和脂肪体中，用于脂肪体分解和降解。这些结果表明，组织蛋白酶 L 与粒细胞向大颗粒细胞的转化有关，以进入脂肪体，并诱导血细胞凋亡以进一步进行组织降解。
