In insects the reserve proteins are stored in the oocytes into endocytic-originated vesicles named yolk organelles. VPS38/UVRAG and ATG14 are the variant regulatory subunits of two class-III ATG6/Beclin1 PI3K complexes that regulate the recruitment of the endocytic (complex II) and autophagic (complex I) machineries. In a previous work from our group, we found that the silencing of ATG6/Beclin1 resulted in the formation of yolk-deficient oocytes due to defects in the endocytosis of the yolk proteins. Because ATG6/Beclin1 is present in the two above-described PI3K complexes, we could not identify the contributions of each complex to the yolk defective phenotypes. To address this, here we investigated the role of the variant subunits VPS38/UVRAG (complex II, endocytosis) and ATG14 (complex I, autophagy) in the biogenesis of the yolk organelles in the insect vector of Chagas Disease Rhodnius prolixus. Interestingly, the silencing of both genes phenocopied the silencing of ATG6/Beclin1, generating 1) accumulation of yolk proteins in the hemolymph; 2) white, smaller, and yolk-deficient oocytes; 3) abnormal yolk organelles in the oocyte cortex; and 4) unviable F1 embryos. However, we found that the similar phenotypes were the result of a specific cross-silencing effect among the PI3K subunits where the silencing of VPS38/UVRAG and ATG6/Beclin1 resulted in the specific silencing of each other, whereas the silencing of ATG14 triggered the silencing of all three PI3K components. Because the silencing of VPS38/UVRAG and ATG6/Beclin1 reproduced the yolk-deficiency phenotypes without the cross silencing of ATG14, we concluded that the VPS38/UVRAG PI3K complex II was the major contributor to the previously observed phenotypes in silenced insects. Altogether, we found that class-III ATG6/Beclin1 PI3K complex II (VPS38/UVRAG) is essential for the yolk endocytosis and that the subunits of both complexes are under an unknown transcriptional regulatory system.

中文翻译：

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VPS38/UVRAG 和 ATG14 是 ATG6/Beclin1-PI3K 复合物的变异调节亚基，对于卵黄细胞器的生物发生至关重要，并且在载体 Rhodnius prolixus 的卵母细胞中受到转录调控。

在昆虫中，储备蛋白储存在卵母细胞中，形成内吞产生的囊泡，称为卵黄细胞器。VPS38/UVRAG 和 ATG14 是两个 III 类 ATG6/Beclin1 PI3K 复合物的变异调节亚基，它们调节内吞（复合物 II）和自噬（复合物 I）机器的募集。在我们小组之前的一项工作中，我们发现 ATG6/Beclin1 的沉默导致由于蛋黄蛋白内吞作用缺陷而导致形成缺乏蛋黄的卵母细胞。由于 ATG6/Beclin1 存在于上述两种 PI3K 复合物中，我们无法确定每个复合物对蛋黄缺陷表型的贡献。为了解决这个问题，我们在这里研究了变异亚基 VPS38/UVRAG（复合物 II，内吞作用）和 ATG14（复合物 I，自噬）在恰加斯病 Rhodnius prolixus 昆虫载体中卵黄细胞器的生物发生中。有趣的是，这两个基因的沉默表型复制了 ATG6/Beclin1 的沉默，产生了 1) 血淋巴中卵黄蛋白的积累；2) 白色的、较小的、缺乏卵黄的卵母细胞；3）卵母细胞皮层卵黄细胞器异常；和 4) 不能存活的 F1 胚胎。然而，我们发现相似的表型是 PI3K 亚基之间特定交叉沉默效应的结果，其中 VPS38/UVRAG 和 ATG6/Beclin1 的沉默导致彼此的特定沉默，而 ATG14 的沉默触发了沉默所有三个 PI3K 组件。因为 VPS38/UVRAG 和 ATG6/Beclin1 的沉默复制了蛋黄缺乏表型，而没有 ATG14 的交叉沉默，我们得出结论，VPS38/UVRAG PI3K 复合物 II 是先前观察到的沉默昆虫表型的主要贡献者。总之，我们发现 III 类 ATG6/Beclin1 PI3K 复合物 II（VPS38/UVRAG）对于蛋黄内吞作用是必不可少的，并且两种复合物的亚基都处于未知的转录调控系统之下。