Nuclear-cytoplasmic communication is not limited to nuclear pores, with both proteins and RNA using alternative routes between these compartments. We previously characterized cytoplasmic capes (large invaginations of the nuclear envelope in Drosophila), which are enriched for the membrane-bound EGF receptor ligand mSpitz, endosome-related organelles and ubiquitylated proteins. Closely associated with capes are groups of perinuclear vesicles resembling those seen at sites of RNP export via a budding mechanism. Here, we demonstrate that mSpitz delivery to capes requires passage through the endosomal system. We also show that capes are closely associated with sites of non-canonical RNP export as well as the dFrizzled2 receptor C terminal fragment, a core component of this export pathway. Video microscopy of glands in intact larvae indicates that cytoplasmic capes are stable structures that persist for at least 90 minutes without conspicuous growth. We further show that capes appear with the growth of the salivary gland rather than its developmental stage. Finally, we show that the large F-actin binding protein β_H-spectrin, which modulates endosomal trafficking, as well as its partner β_H-spectrin are required for cape formation. Cytoplasmic capes therefore represent a subspecialization of the nuclear envelope where endosomal trafficking and RNP export are closely associated.

中文翻译：

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果蝇EGFR配体mSpitz通过内体系统传递至核膜上非典型RNA出口的位点的细胞质岬。

核质之间的通讯不限于核孔，蛋白质和RNA都使用这些区室之间的替代途径。我们以前表征细胞质的披风（果蝇的核被膜大片内陷），富含膜结合的EGF受体配体mSpitz，内体相关的细胞器和泛素化的蛋白质。与海角密切相关的是一组核周囊泡，类似于在RNP出口部位通过一种萌芽的机制。在这里，我们证明mSpitz传递到海角需要通过内体系统。我们还显示，海角与非规范RNP出口以及dFrizzled2受体C末端片段（此出口途径的核心组成部分）紧密相关。完整幼体中腺的视频显微镜检查表明，胞浆角是稳定的结构，可以持续至少90分钟而不会明显生长。我们进一步表明，海角随唾液腺的生长而不是其发育阶段出现。最后，我们表明，大F-肌动蛋白β结合蛋白_{^ h} -spectrin，其调节内体运输，以及它的β伙伴_{^ h}-血影蛋白是形成海角所必需的。因此，胞质角代表核包膜的一个亚专业化，其中内体运输和RNP出口密切相关。