Department of Cell and Developmental Biology, Centre de Regulacio Genomica, 08003 Barcelona, Spain.
Dev Cell. 2011 May 17;20(5):652-62. doi: 10.1016/j.devcel.2011.03.014.
Actin-severing proteins ADF/cofilin are required for the sorting of secretory cargo at the trans-Golgi network (TGN) in mammalian cells. How do these cytoplasmic proteins interact with the cargoes in the lumen of the TGN? Put simply, how are these two sets of proteins connected across the TGN membrane? Mass spectrometry of cofilin1 immunoprecipitated from HeLa cells revealed the presence of actin and the Ca(2+) ATPase SPCA1. Moreover, cofilin1 was localized to the TGN and bound to SPCA1 via dynamic actin. SPCA1 knockdown, like ADF/cofilin1 knockdown, inhibited Ca(2+) uptake into the TGN and caused missorting of secretory cargo. These defects were rescued by the overexpression of the TGN-localized SPCA1. We propose that ADF/cofilin-dependent severing of actin filaments exposes and promotes the activation of SPCA1, which pumps Ca(2+) into the lumen of the TGN for the sorting of the class of secretory cargo that binds Ca(2+).
在哺乳细胞中，肌动蛋白解聚蛋白 ADF/cofilin 对于跨高尔基网络（TGN）中分泌货物的分拣是必需的。这些细胞质蛋白如何与 TGN 管腔中的货物相互作用？简单地说，这两组蛋白质如何在 TGN 膜上连接？从 HeLa 细胞中免疫沉淀的 cofilin1 的质谱分析揭示了肌动蛋白和 Ca(2+)ATPase SPCA1 的存在。此外，cofilin1 定位于 TGN 并通过动态肌动蛋白与 SPCA1 结合。SPCA1 的敲低，与 ADF/cofilin1 的敲低一样，抑制了 Ca(2+)进入 TGN 的摄取，并导致分泌货物的错误分拣。这些缺陷可以通过过表达定位于 TGN 的 SPCA1 来挽救。我们提出，ADF/cofilin 依赖性肌动蛋白丝的切断暴露并促进 SPCA1 的激活，SPCA1 将 Ca(2+)泵入 TGN 的管腔，用于分拣与 Ca(2+)结合的一类分泌货物。
