Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA.
Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA.
Cell Rep. 2021 Oct 19;37(3):109840. doi: 10.1016/j.celrep.2021.109840.
Nearly one-third of proteins are initially targeted to the endoplasmic reticulum (ER) membrane, where they are correctly folded and then delivered to their final cellular destinations. To prevent the accumulation of misfolded membrane proteins, ER-associated degradation (ERAD) moves these clients from the ER membrane to the cytosol, a process known as retrotranslocation. Our recent work in Saccharomyces cerevisiae reveals a derlin rhomboid pseudoprotease, Dfm1, is involved in the retrotranslocation of ubiquitinated ERAD membrane substrates. In this study, we identify conserved residues of Dfm1 that are critical for retrotranslocation. We find several retrotranslocation-deficient Loop 1 mutants that display impaired binding to membrane substrates. Furthermore, Dfm1 possesses lipid thinning function to facilitate in the removal of ER membrane substrates, and this feature is conserved in its human homolog, Derlin-1, further implicating that derlin-mediated retrotranslocation is a well-conserved process.
近三分之一的蛋白质最初被靶向内质网（ER）膜，在那里它们被正确折叠，然后被运送到它们最终的细胞目的地。为了防止错误折叠的膜蛋白的积累，内质网相关降解（ERAD）将这些客户从 ER 膜转移到细胞质中，这个过程称为逆向转运。我们最近在酿酒酵母中的工作表明，一种 derlin 菱形假蛋白酶 Dfm1 参与了泛素化 ERAD 膜底物的逆向转运。在这项研究中，我们确定了 Dfm1 的保守残基，这些残基对逆向转运至关重要。我们发现了几个 Loop 1 突变体，这些突变体在与膜底物的结合方面存在缺陷。此外，Dfm1 具有脂质变薄的功能，有助于去除 ER 膜底物，并且这个特征在其人类同源物 Derlin-1 中是保守的，这进一步表明 derlin 介导的逆向转运是一个高度保守的过程。
