Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA.
Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA.
Sci Rep. 2021 Oct 14;11(1):20398. doi: 10.1038/s41598-021-99893-7.
SARS-CoV-2 infection depends on binding its spike (S) protein to angiotensin-converting enzyme 2 (ACE2). The S protein expresses an RGD motif, suggesting that integrins may be co-receptors. Here, we UV-inactivated SARS-CoV-2 and fluorescently labeled the envelope membrane with octadecyl rhodamine B (R18) to explore the role of integrin activation in mediating cell entry and productive infection. We used flow cytometry and confocal microscopy to show that SARS-CoV-2 particles engage basal-state integrins. Furthermore, we demonstrate that Mn, which induces integrin extension, enhances cell entry of SARS-CoV-2. We also show that one class of integrin antagonist, which binds to the αI MIDAS site and stabilizes the inactive, closed conformation, selectively inhibits the engagement of SARS-CoV-2 with basal state integrins, but is ineffective against Mn-activated integrins. RGD-integrin antagonists inhibited SARS-CoV-2 binding regardless of integrin activation status. Integrins transmit signals bidirectionally: 'inside-out' signaling primes the ligand-binding function of integrins via a talin-dependent mechanism, and 'outside-in' signaling occurs downstream of integrin binding to macromolecular ligands. Outside-in signaling is mediated by Gα. Using cell-permeable peptide inhibitors of talin and Gα binding to the cytoplasmic tail of an integrin's β subunit, we demonstrate that talin-mediated signaling is essential for productive infection.
SARS-CoV-2 感染依赖于其刺突(S)蛋白与血管紧张素转化酶 2(ACE2)的结合。S 蛋白表达 RGD 基序,表明整合素可能是共受体。在这里,我们用紫外线灭活 SARS-CoV-2,并使用十八烷基罗丹明 B(R18)对包膜进行荧光标记,以探索整合素激活在介导细胞进入和有效感染中的作用。我们使用流式细胞术和共聚焦显微镜表明,SARS-CoV-2 颗粒与基础状态的整合素结合。此外,我们证明 Mn 诱导整合素延伸,增强 SARS-CoV-2 的细胞进入。我们还表明,一类整合素拮抗剂,与αI MIDAS 位点结合并稳定无活性的封闭构象,选择性抑制 SARS-CoV-2 与基础状态整合素的结合,但对 Mn 激活的整合素无效。RGD 整合素拮抗剂抑制 SARS-CoV-2 结合,无论整合素激活状态如何。整合素双向传递信号:“内-外”信号通过依赖于 talin 的机制激活整合素的配体结合功能,而“外-内”信号发生在整合素与大分子配体结合的下游。外-内信号由 Gα 介导。使用细胞通透性肽抑制剂 talin 和 Gα 与整合素β亚基胞质尾部的结合,我们证明了 talin 介导的信号对于有效感染是必不可少的。