Kloc Malgorzata, Uosef Ahmed, Kubiak Jacek Z, Ghobrial Rafik M
Houston Methodist Research Institute, Houston, TX 77030, USA.
Department of Surgery, Houston Methodist Hospital, Houston, TX 77030, USA.
Biology (Basel). 2021 Mar 19;10(3):238. doi: 10.3390/biology10030238.
Human placenta formation relies on the interaction between fused trophoblast cells of the embryo with uterine endometrium. The fusion between trophoblast cells, first into cytotrophoblast and then into syncytiotrophoblast, is facilitated by the fusogenic protein syncytin. Syncytin derives from an envelope glycoprotein (ENV) of retroviral origin. In exogenous retroviruses, the envelope glycoproteins coded by genes allow fusion of the viral envelope with the host cell membrane and entry of the virus into a host cell. During mammalian evolution, the genes have been repeatedly, and independently, captured by various mammalian species to facilitate the formation of the placenta. Such a shift in the function of a gene, or a trait, for a different purpose during evolution is called an exaptation (co-option). We discuss the structure and origin of the placenta, the fusogenic and non-fusogenic functions of syncytin, and the mechanism of cell fusion. We also comment on an alleged danger of the COVID-19 vaccine based on the presupposed similarity between syncytin and the SARS-CoV-2 spike protein.
人类胎盘的形成依赖于胚胎中融合的滋养层细胞与子宫内膜之间的相互作用。滋养层细胞之间的融合，首先形成细胞滋养层，然后形成合体滋养层，这一过程由融合蛋白合体素促进。合体素源自逆转录病毒的包膜糖蛋白（ENV）。在外源逆转录病毒中，由基因编码的包膜糖蛋白使病毒包膜与宿主细胞膜融合，并使病毒进入宿主细胞。在哺乳动物进化过程中，这些基因被各种哺乳动物物种反复且独立地捕获，以促进胎盘的形成。在进化过程中，一个基因或性状为了不同目的而发生功能转变，这种现象被称为扩展适应（功能借用）。我们讨论了胎盘的结构和起源、合体素的融合和非融合功能以及细胞融合的机制。我们还基于合体素与严重急性呼吸综合征冠状病毒2（SARS-CoV-2）刺突蛋白之间假定的相似性，对2019冠状病毒病（COVID-19）疫苗所谓的危险性进行了评论。
