The classical secretion of soluble proteins and transport of integral membrane proteins to the cell surface require transit into and through the endoplasmic reticulum and the Golgi apparatus. Signal peptides or transmembrane domains target proteins for translocation into the lumen or insertion into the membrane of the endoplasmic reticulum, respectively. Here we discuss two mechanisms of unconventional protein targeting to plasma membranes, i.e., transport processes that are active in the absence of a functional Golgi system. We first focus on integral membrane proteins that are inserted into the endoplasmic reticulum but that, however, are transported to plasma membranes in a Golgi-independent manner. We then discuss soluble secretory proteins that are secreted from cells without any involvement of the endoplasmic reticulum and the Golgi apparatus.

中文翻译：

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蛋白质转运到真核细胞细胞表面的非常规机制。

可溶性蛋白的经典分泌和整合膜蛋白向细胞表面的转运需要转移进入并穿过内质网和高尔基体。信号肽或跨膜结构域分别靶向蛋白质，以分别转运至内腔或内质网的膜中。在这里，我们讨论了非常规蛋白质靶向质膜的两种机制，即在没有功能性高尔基体系统的情况下活跃的转运过程。我们首先关注插入到内质网中的完整膜蛋白，但是这些蛋白以高尔基体独立的方式转运到质膜。