Department of Brain Function, Division of Stress Adaptation and Protection, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi, 464-8601, Japan; Department of Molecular Pharmacokinetics, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 464-8601, Japan.
Institute for Advanced Sciences, Toagosei Co., Ltd., Tsukuba, Ibaraki, 300-2611, Japan.
Biochem Biophys Res Commun. 2021 Jun 30;560:21-26. doi: 10.1016/j.bbrc.2021.04.073. Epub 2021 May 5.
Signal peptides (SPs) consist of short peptide sequences present at the N-terminal of newly synthesizing proteins and act as a zip code for the translocation of the proteins to the endoplasmic reticulum (ER). It was thought that the SPs are intracellularly degraded after translocation to the ER; however, recent studies showed cleaved SPs have diverse roles for controlling cell functions in auto- and/or intercellular manners. In addition, it still remains obscure how SP fragments translocate away from the site where they are produced. Extracellular vesicles (EV) are important for intercellular communication and can transport functional molecules to specific cells. In this study, we show that SPs are involved in EV from T-REx AspALP cells that were transfected with a human APP SP-inducible expression vector. There was no difference in the average particle size or particle concentration of EV collected from T-REx AspALP cells and T-REx Mock cells. When the SP content in the EV was examined by mass spectrometry, the C-terminal fragment of APP SP was identified in the exosomes (SEV) of T-REx AspALP cells. In our preparation of SEV fractions, no ER-specific proteins were detected; therefore, SPs may be included in SEV but not in the debris of degraded ER. This is the first indication that SPs are secreted from cells via EV.
信号肽（SPs）由新合成蛋白质的 N 端的短肽序列组成，充当蛋白质向内质网（ER）易位的邮政编码。人们认为 SP 在易位到 ER 后在细胞内降解；然而，最近的研究表明，切割的 SP 以自动和/或细胞间方式控制细胞功能具有多种作用。此外，SP 片段如何从产生它们的位置转移出去仍然不清楚。细胞外囊泡（EV）对于细胞间通讯很重要，并且可以将功能分子运输到特定的细胞。在这项研究中，我们表明，转染了人 APP SP 诱导表达载体的 T-REx AspALP 细胞中的 EV 涉及 SP。从 T-REx AspALP 细胞和 T-REx Mock 细胞收集的 EV 的平均颗粒大小或颗粒浓度没有差异。当通过质谱法检查 EV 中的 SP 含量时，在 T-REx AspALP 细胞的外泌体（SEV）中鉴定出 APP SP 的 C 端片段。在我们的 SEV 级分制备中，未检测到 ER 特异性蛋白；因此，SPs 可能包含在 SEV 中，但不包含降解的 ER 碎片中。这是 SP 通过 EV 从细胞中分泌的第一个迹象。
