Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany.
J Cell Sci. 2012 Apr 15;125(Pt 8):1958-69. doi: 10.1242/jcs.096727. Epub 2012 Feb 28.
Co-translational transport of polypeptides into the endoplasmic reticulum (ER) involves the Sec61 channel and additional components such as the ER lumenal Hsp70 BiP and its membrane-resident co-chaperone Sec63p in yeast. We investigated whether silencing the SEC61A1 gene in human cells affects co- and post-translational transport of presecretory proteins into the ER and post-translational membrane integration of tail-anchored proteins. Although silencing the SEC61A1 gene in HeLa cells inhibited co- and post-translational transport of signal-peptide-containing precursor proteins into the ER of semi-permeabilized cells, silencing the SEC61A1 gene did not affect transport of various types of tail-anchored protein. Furthermore, we demonstrated, with a similar knockdown approach, a precursor-specific involvement of mammalian Sec63 in the initial phase of co-translational protein transport into the ER. By contrast, silencing the SEC62 gene inhibited only post-translational transport of a signal-peptide-containing precursor protein.
多肽共翻译进入内质网（ER）的过程涉及 Sec61 通道和其他成分，如酵母中内质网腔热休克蛋白 70（Hsp70）BiP 和其膜驻留伴侣 Sec63p。我们研究了在人细胞中沉默 SEC61A1 基因是否会影响前分泌蛋白的共翻译和翻译后进入 ER 以及尾部锚定蛋白的翻译后膜整合。尽管在 HeLa 细胞中沉默 SEC61A1 基因抑制了含有信号肽的前体蛋白进入半透化细胞 ER 的共翻译和翻译后运输，但沉默 SEC61A1 基因并不影响各种类型的尾部锚定蛋白的运输。此外，我们通过类似的敲低方法证明了哺乳动物 Sec63 在翻译起始阶段参与了共翻译蛋白向 ER 的初始运输。相比之下，沉默 SEC62 基因仅抑制了含有信号肽的前体蛋白的翻译后运输。
