人巨细胞病毒(HCMV)US12基因家族通过调节病毒的细胞嗜性及其对宿主先天免疫反应的逃避来促进病毒与宿主的相互作用。US21,10个US12基因之一(US12-US21),是捕获的包含细胞跨膜BAX抑制剂基序的基因的后代。它编码7TMD内质网(ER)驻留的病毒传播蛋白(pUS21),能够降低ER存储的Ca2含量,which,反过来,保护细胞免受凋亡。由于Ca2+稳态的调节影响广泛的细胞反应,包括细胞运动性,我们研究了pUS21是否也可能干扰Ca2+信号传导的这种细胞生物学结果。的确,US21基因的缺失损害了HCMV感染细胞的迁移能力,而US21蛋白的表达刺激细胞迁移和粘附,以及局灶性粘附(FA)动力学,在某种程度上取决于其操纵ERCa2+含量的能力。机制研究表明,pUS21介导的细胞迁移涉及钙蛋白酶2的激活,因为它的抑制作用阻止了viroporin对细胞运动的影响。相应地,pUS21表达刺激了储存操作的Ca2进入(SOCE)机制,该机制可以通过促进Ca2进入来确定钙蛋白酶2的激活。此外,观察到pUS21与钙蛋白酶2底物talin-1相互作用,和FA复合物的关键蛋白质成分。这种相互作用的功能结果被talin-1敲低证实,这废除了pUS21介导的细胞迁移增加。一起,这些结果表明,在HCMV感染的情况下,US21编码的病毒蛋白是细胞粘附和迁移的病毒调节因子.重要性人巨细胞病毒(HCMV)是一种机会性病原体,其成功部分归功于捕获,重复,和调节细胞基因以产生现代病毒蛋白,这些蛋白通过干扰许多细胞生化和生理途径来促进宿主的感染和持久性。US21病毒蛋白提供了这种进化策略的一个例子:它是细胞衍生的钙通道,其操纵细胞内钙稳态以赋予HCMV复制的边缘。这里,我们报道了US21蛋白通过其钙通道活性机制作为细胞迁移和粘附的病毒调节因子的新功能的特征.HCMV多功能调节蛋白的表征,与US21一样,支持更好地理解病毒的发病机制,并可能为设计利用其功能的新抗病毒策略开辟道路。
The human cytomegalovirus (HCMV) US12 gene family contributes to virus-host interactions by regulating the virus\' cell tropism and its evasion of host innate immune responses. US21, one of the 10 US12 genes (US12-US21), is a descendant of a captured cellular transmembrane BAX inhibitor motif-containing gene. It encodes a 7TMD endoplasmic reticulum (ER)-resident
viroporin (pUS21) capable of reducing the Ca2+ content of ER stores, which, in turn, protects cells against apoptosis. Since regulation of Ca2+ homeostasis affects a broad range of cellular responses, including cell motility, we investigated whether pUS21 might also interfere with this cytobiological consequence of Ca2+ signaling. Indeed, deletion of the US21 gene impaired the ability of HCMV-infected cells to migrate, whereas expression of US21 protein stimulated cell migration and adhesion, as well as focal adhesion (FA) dynamics, in a way that depended on its ability to manipulate ER Ca2+ content. Mechanistic studies revealed pUS21-mediated cell migration to involve calpain 2 activation since its inhibition prevented the
viroporin\'s effects on cell motility. Pertinently, pUS21 expression stimulated a store-operated Ca2+ entry (SOCE) mechanism that may determine the activation of calpain 2 by promoting Ca2+ entry. Furthermore, pUS21 was observed to interact with talin-1, a calpain 2 substrate, and crucial protein component of FA complexes. A functional consequence of this interaction was confirmed by talin-1 knockdown, which abrogated the pUS21-mediated increase in cell migration. Together, these results indicate the US21-encoded
viroporin to be a viral regulator of cell adhesion and migration in the context of HCMV infection. IMPORTANCE Human cytomegalovirus (HCMV) is an opportunistic pathogen that owes part of its success to the capture, duplication, and tuning of cellular genes to generate modern viral proteins which promote infection and persistence in the host by interfering with many cell biochemical and physiological pathways. The US21 viral protein provides an example of this evolutionary strategy: it is a cellular-derived calcium channel that manipulates intracellular calcium homeostasis to confer edges to HCMV replication. Here, we report on the characterization of a novel function of the US21 protein as a viral regulator of cell migration and adhesion through mechanisms involving its calcium channel activity. Characterization of HCMV multifunctional regulatory proteins, like US21, supports the better understanding of viral pathogenesis and may open avenues for the design of new antiviral strategies that exploit their functions.