Dual topologies of proteins at the ER membrane are known for a variety of proteins allowing the same protein to exert different functions according to the topology adopted. A dual topology of the co-chaperone ERdj4, which resides in the endoplasmic reticulum (ER), was proposed recently, a thesis that we found to align all published data and existing controversies into one whole picture. The aim of this review is to reassess all primary data available in the literature on ER-resident Hsp40 co-chaperones with respect to their topology. After careful and critical analyses of all experimental data published so far, we identified, next to ERdj4, two other co-chaperones, ERdj3 and ERdj6, that also display features of a dual topology at the ER membrane. We assume that during cellular stress subpools of some ER-resident J protein can alter their topology so that these proteins can exert different functions in order to adapt to cellular stress.

内质网膜上蛋白质的双重拓扑结构已知用于多种蛋白质，允许相同蛋白质根据采用的拓扑结构发挥不同的功能。最近提出了一种位于内质网 (ER) 中的共伴侣 ERdj4 的双重拓扑结构，我们发现该论文将所有已发表的数据和现有的争议整合为一个整体。本综述的目的是重新评估文献中关于内质网驻留 Hsp40 共伴侣的拓扑结构的所有主要数据。在对迄今为止发表的所有实验数据进行仔细和批判性分析后，我们在 ERdj4 旁边确定了另外两个共同伴侣，ERdj3 和 ERdj6，它们也显示出 ER 膜的双重拓扑特征。