Rivero Vanessa, Saiz María Laura, Torralba Daniel, López-Larrea Carlos, Suarez-Alvarez Beatriz, DeDiego Marta L
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049 Madrid, Spain.
Translational Immunology, Health Research Institute of the Principality of Asturias (ISPA), 33011 Oviedo, Spain.
Viruses. 2025 Aug 20;17(8):1141. doi: 10.3390/v17081141.
CD9 protein belongs to a family of proteins called tetraspanins, so named for their four-transmembrane-spanning architectures. These proteins are located in domains in the plasmatic membrane, called tetraspanin-enriched microdomains (TEMs). Several proteases and cellular receptors for virus entry cluster into TEMs, suggesting that TEMs are preferred virus entry portals. Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein mediates virus attachment and entry into cells by binding to human angiotensin-converting enzyme 2 (ACE-2). In addition, the secretory, type-I membrane-bound SARS-CoV-2 S protein is synthesized as a precursor (proS) that undergoes posttranslational cleavages by host cell proteases, such as furin and TMPRSS2. Moreover, it has been shown that neuropilin-1 (NRP1), which is known to bind furin-cleaved substrates, potentiates SARS-CoV-2 infectivity. Our results indicate that CD9 facilitates SARS-CoV-2 infection. In addition, we show how knocking out CD9 leads to a decrease in the expression of NRP1, a protein that improves SARS-CoV-2 infection. Furthermore, we show that CD9 colocalizes with ACE-2, NRP1, furin, and TMPRSS2 at the plasma membrane; that the absence of CD9 decreases the expression of these proteins on the plasma membrane CD9-enriched microdomains, and that CD9 interacts with ACE2. In conclusion, our data suggest that CD9 facilitates SARS-CoV-2 infection and that CD9 brings together different host proteins involved in SARS-CoV-2 attachment and entry into host cells, such as ACE2, NRP1, furin, and TMPRSS2. Importantly, the fact that a blocking antibody targeting CD9 can effectively reduce SARS-CoV-2 titers highlights not only the mechanistic role of CD9 in viral entry but also offers translational potential, suggesting that tetraspanin-targeting antibodies could be developed as therapeutic agents against SARS-CoV-2 and possibly other coronaviruses, with meaningful implications for clinical intervention.
CD9蛋白属于一类称为四跨膜蛋白的蛋白质家族，因其具有四个跨膜结构域而得名。这些蛋白质位于质膜中的结构域，称为富含四跨膜蛋白的微结构域（TEMs）。几种用于病毒进入的蛋白酶和细胞受体聚集在TEMs中，这表明TEMs是病毒进入的首选门户。严重急性呼吸综合征冠状病毒2（SARS-CoV-2）刺突（S）蛋白通过与人血管紧张素转换酶2（ACE-2）结合来介导病毒附着和进入细胞。此外，分泌型的I型膜结合SARS-CoV-2 S蛋白以前体（proS）形式合成，该前体在宿主细胞蛋白酶（如弗林蛋白酶和跨膜丝氨酸蛋白酶2（TMPRSS2））的作用下进行翻译后切割。此外，已经表明，已知与弗林蛋白酶切割底物结合的神经纤毛蛋白-1（NRP1）可增强SARS-CoV-2的感染性。我们的结果表明，CD9促进SARS-CoV-2感染。此外，我们展示了敲除CD9如何导致NRP1表达的降低，NRP1是一种可改善SARS-CoV-2感染的蛋白质。此外，我们表明CD9在质膜上与ACE-2、NRP1、弗林蛋白酶和TMPRSS2共定位；CD9的缺失会降低这些蛋白质在富含CD9的质膜微结构域上的表达，并且CD9与ACE2相互作用。总之，我们的数据表明CD9促进SARS-CoV-2感染，并且CD9将参与SARS-CoV-2附着和进入宿主细胞的不同宿主蛋白聚集在一起，如ACE2、NRP1、弗林蛋白酶和TMPRSS2。重要的是，靶向CD9的阻断抗体能够有效降低SARS-CoV-2滴度这一事实不仅突出了CD9在病毒进入中的机制作用，还具有转化潜力，表明靶向四跨膜蛋白的抗体可被开发为针对SARS-CoV-2以及可能针对其他冠状病毒的治疗药物，对临床干预具有重要意义。
