Griciuc Ana, Aron Liviu, Piccoli Giovanni, Ueffing Marius
Department of Protein Science, Helmholtz Zentrum Muenchen-German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany.
Biochim Biophys Acta. 2010 Mar;1803(3):424-34. doi: 10.1016/j.bbamcr.2010.01.008. Epub 2010 Jan 25.
Dominant mutations in the visual pigment Rhodopsin (Rh) cause retinitis pigmentosa (RP) characterized by progressive blindness and retinal degeneration. The most common Rh mutation, Rh(P23H) forms aggregates in the endoplasmic reticulum (ER) and impairs the proteasome; however, the mechanisms linking Rh aggregate formation to proteasome dysfunction and photoreceptor cell loss remain unclear. Using mammalian cell cultures, we provide the first evidence that misfolded Rh(P23H) is a substrate of the ERAD effector VCP, an ATP-dependent chaperone that extracts misfolded proteins from the ER and escorts them for proteasomal degradation. VCP co-localizes with misfolded Rh(P23H) in retinal cells and requires functional N-terminal and D1 ATPase domains to form a complex with Rh(P23H) aggregates. Furthermore, VCP uses its D2 ATPase activity to promote Rh(P23H) aggregate retrotranslocation and proteasomal delivery. Our results raise the possibility that modulation of VCP and ERAD activity might have potential therapeutic significance for RP.
视色素视紫红质（Rh）中的显性突变会导致色素性视网膜炎（RP），其特征为进行性失明和视网膜变性。最常见的Rh突变Rh（P23H）在内质网（ER）中形成聚集体并损害蛋白酶体；然而，将Rh聚集体形成与蛋白酶体功能障碍和光感受器细胞丢失联系起来的机制仍不清楚。利用哺乳动物细胞培养，我们首次提供证据表明错误折叠的Rh（P23H）是ERAD效应蛋白VCP的底物，VCP是一种ATP依赖性伴侣蛋白，可从内质网中提取错误折叠的蛋白质并将它们护送至蛋白酶体进行降解。VCP在视网膜细胞中与错误折叠的Rh（P23H）共定位，并且需要功能性的N末端和D1 ATP酶结构域才能与Rh（P23H）聚集体形成复合物。此外，VCP利用其D2 ATP酶活性促进Rh（P23H）聚集体的逆向转运和蛋白酶体递送。我们的结果提出了一种可能性，即调节VCP和ERAD活性可能对RP具有潜在的治疗意义。
