Department of General Biology, Universidade Federal de Viçosa, 36570-000, Viçosa, Brazil.
Departament of Entomology, Universidade Federal de Viçosa, 36570-000, Viçosa, Brazil.
Sci Rep. 2019 Nov 11;9(1):16441. doi: 10.1038/s41598-019-52789-z.
Vitellogenin is the main yolk precursor protein in insect oocytes. It is synthesized in the fat body and released into the hemolymph. To reach the oocyte surface, vitellogenin must cross a single layer of follicular epithelium cells. The transport of vitellogenin across the follicular epithelium has been suggested to occur through the enlarged intercellular spaces (patency) by a paracellular route or by endocytosis by follicular cells and release onto oocyte surface in a transcelluar route. In this study, we investigated whether vitellogenin transport in the meroistic telotrophic ovary of Podisus nigrispinus (Hemiptera) occurs via a paracellular or transcellular route. Light and transmission electron microscopies showed that short cell-cell contacts with well-developed occluding septate junctions were present in follicular cells with patency. Immunofluorescence microscopy revealed the presence of vitellogenin receptors in the plasma membrane and of vitellogenin in the cytoplasm of follicular cells. Data suggest that cell-cell contacts serve as a barrier to large vitellogenin molecules and that this protein is transported via a transcellular route of receptor-mediated endocytosis.
卵黄蛋白原是昆虫卵母细胞中主要的卵黄前体蛋白。它在脂肪体中合成，并释放到血淋巴中。为了到达卵母细胞表面，卵黄蛋白原必须穿过单层滤泡上皮细胞。有人提出，卵黄蛋白原通过细胞旁途径或通过滤泡细胞的内吞作用和在细胞间途径中释放到卵母细胞表面，穿过滤泡上皮细胞的运输是通过扩大的细胞间空间（通透性）发生的。在这项研究中，我们研究了黑肩绿盲蝽（半翅目）的裂体增殖卵巢中的卵黄蛋白原运输是否通过细胞旁途径或细胞内途径发生。光镜和透射电镜显示，通透性滤泡细胞中的短细胞-细胞接触具有发达的封闭性有丝分裂连接。免疫荧光显微镜显示，卵黄蛋白原受体存在于滤泡细胞的质膜中，而卵黄蛋白原存在于细胞质中。数据表明，细胞-细胞接触作为大卵黄蛋白原分子的屏障，并且该蛋白质通过受体介导的内吞作用的细胞内途径运输。
