Institut National de la Santé et de la Recherche Médicale, INSERM UMR-S 940, Institut Universitaire d'Hématologie, Université Paris VII, Paris, France.
J Biol Chem. 2011 May 27;286(21):18583-92. doi: 10.1074/jbc.M111.222257. Epub 2011 Mar 30.
Ca(2+) signaling plays an important role in B cell survival and activation and is dependent on Ca(2+) trapped in the endoplasmic reticulum (ER) and on extracellular Ca(2+). Epstein-Barr virus (EBV) can immortalize B cells and contributes to lymphomagenesis. Previously, we showed that the ER Ca(2+) content of Burkitt lymphoma cell lines was increased following infection with immortalization-competent virus expressing the full set of EBV latency genes (B95-8). In contrast, infection with an immortalization-deficient virus (P3HR-1) not expressing LMP-1 is without effect. LMP-1 protein expression was sufficient to increase the ER Ca(2+) content and to increase the cytosolic Ca(2+) concentration (Ca(2+)). In this follow-up study, we showed that the resting Ca(2+) of P3HR-1-infected cells was decreased, implying that EBV not only modified the ER homeostasis but also affected the cytosolic Ca(2+) homeostasis. Furthermore, even if the store-operated calcium entry (SOCE) of these cells was normal, the Ca(2+) increase after thapsigargin + CaCl(2) stimulation was blunted. In contrast, the resting Ca(2+) of B95-8 infected cells was not changed, even if their SOCE was increased significantly. When expressed alone, LMP-1 induced an increase of the SOCE amplitude and the expression of the protein allowing this influx, Orai1, showing the effect of EBV on SOCE of B cells are mediated by LMP-1. However, other hitherto unidentified EBV processes, unmasked in P3HR-1 infected cells, counteract this LMP-1-dependent increase of SOCE amplitude to impair a general and potentially toxic increase of Ca(2+). Thus, EBV infection modifies the cellular Ca(2+) homeostasis by acting on the ER and plasma membrane transporters.
钙离子信号在 B 细胞的存活和激活中起着重要作用，依赖于内质网（ER）中被困的 Ca2+和细胞外 Ca2+。EB 病毒（EBV）可以使 B 细胞永生化，并有助于淋巴瘤的发生。以前，我们发现感染表达全套 EBV 潜伏基因的永生化能力病毒（B95-8）的 Burkitt 淋巴瘤细胞系的 ER Ca2+含量增加。相比之下，感染不表达 LMP-1 的永生化缺陷病毒（P3HR-1）则没有效果。LMP-1 蛋白的表达足以增加 ER Ca2+含量并增加细胞浆 Ca2+浓度([Ca2+]（cyt）)。在这项后续研究中，我们发现 P3HR-1 感染细胞的静息[Ca2+]（cyt）减少，这意味着 EBV 不仅改变了 ER 内环境平衡，还影响了细胞浆 Ca2+内环境平衡。此外，即使这些细胞的储存操作钙内流（SOCE）正常，用 thapsigargin+CaCl2 刺激后 [Ca2+]（cyt）的增加也会受到抑制。相比之下，感染 B95-8 的细胞的静息[Ca2+]（cyt）没有改变，即使它们的 SOCE 显著增加。单独表达时，LMP-1 会增加 SOCE 幅度和允许这种内流的蛋白质 Orai1 的表达，表明 EBV 对 B 细胞 SOCE 的影响是由 LMP-1 介导的。然而，在 P3HR-1 感染的细胞中，其他尚未确定的 EBV 过程被揭示出来，这些过程会抵消这种依赖于 LMP-1 的 SOCE 幅度的增加，从而阻止 [Ca2+]（i）的普遍和潜在毒性增加。因此，EBV 感染通过作用于内质网和质膜转运体来改变细胞内 Ca2+内环境平衡。
