Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
J Virol. 2014 May;88(10):5559-77. doi: 10.1128/JVI.03099-13. Epub 2014 Mar 5.
Epstein-Barr virus (EBV) attachment to human CD21 on the B-cell surface initiates infection. Whether CD21 is a simple tether or conveys vital information to the cell interior for production of host factors that promote infection of primary B cells is controversial, as the cytoplasmic fragment of CD21 is short, though highly conserved. The ubiquity of CD21 on normal B cells, the diversity of this population, and the well-known resistance of primary B cells to gene transfer technologies have all impeded resolution of this question. To uncover the role(s) of the CD21 cytoplasmic domain during infection initiation, the full-length receptor (CD21=CR), a mutant lacking the entire cytoplasmic tail (CT), and a control vector (NEO) were stably expressed in two pre-B-cell lines that lack endogenous receptor. Genome-wide transcriptional analysis demonstrated that stable CD21 surface expression alone (either CR or CT) produced multiple independent changes in gene expression, though both dramatically decreased class I melanoma-associated antigen (MAGE) family RNAs and upregulated genes associated with B-cell differentiation (e.g., C2TA, HLA-II, IL21R, MIC2, CD48, and PTPRCAP/CD45-associated protein). Temporal analysis spanning 72 h revealed that not only CR- but also CT-expressing lines initiated latency. In spite of this, the number and spectrum of transcripts altered in CR- compared with CT-bearing lines at 1 h after infection further diverged. Differential modulation of immediate early cellular transcripts (e.g., c-Jun and multiple histones), both novel and previously linked to CD21-initiated signaling, as well as distinct results from pathway analyses support a separate role for the cytoplasmic domain in initiation of intracellular signals.
Membrane proteins that mediate virus attachment tether virus particles to the cell surface, initiating infection. In addition, upon virus interaction such proteins may transmit signals to the interior of the cell that support subsequent steps in the infection process. Here we show that expression of the Epstein-Barr virus B-cell attachment receptor, CD21, in B cells that lack this receptor results in significant changes in gene expression, both before and rapidly following EBV-CD21 interaction. These changes translate into major signaling pathway alterations that are predicted to support stable infection.
Epstein-Barr 病毒（EBV）附着在 B 细胞表面的人 CD21 上，从而引发感染。CD21 是简单的系绳，还是向细胞内部传递重要信息，以产生促进原发性 B 细胞感染的宿主因子，这是有争议的，因为 CD21 的细胞质片段很短，尽管高度保守。正常 B 细胞上 CD21 的普遍性、该群体的多样性，以及原发性 B 细胞对基因转移技术的明显抗性，都阻碍了这个问题的解决。为了揭示 CD21 细胞质结构域在感染起始过程中的作用，全长受体（CD21=CR）、缺乏整个细胞质尾巴（CT）的突变体和对照载体（NEO）在两种缺乏内源性受体的前 B 细胞系中稳定表达。全基因组转录分析表明，稳定表达 CD21 表面表达（无论是 CR 还是 CT）都会导致基因表达的多个独立变化，尽管这两种情况都大大降低了 I 类黑色素瘤相关抗原（MAGE）家族 RNA 的表达，并上调了与 B 细胞分化相关的基因（例如，C2TA、HLA-II、IL21R、MIC2、CD48 和 PTPRCAP/CD45 相关蛋白）。跨越 72 小时的时间分析表明，不仅 CR-，而且 CT 表达的细胞系也开始潜伏。尽管如此，与感染后 1 小时的 CT 相比，CR 表达的细胞系中改变的转录本的数量和范围进一步分化。瞬时早期细胞转录物（如 c-Jun 和多种组蛋白）的差异调节，既新颖又与 CD21 启动的信号有关，以及通路分析的不同结果都支持细胞质结构域在启动细胞内信号中的独立作用。
介导病毒附着的膜蛋白将病毒颗粒系绳到细胞表面，从而引发感染。此外，在病毒相互作用后，此类蛋白可能向细胞内部传递信号，支持感染过程的后续步骤。在这里，我们表明，在缺乏这种受体的 B 细胞中表达 Epstein-Barr 病毒 B 细胞附着受体 CD21，会导致 EBV-CD21 相互作用之前和之后迅速发生基因表达的显著变化。这些变化转化为主要的信号通路改变，预计将支持稳定的感染。
