Rudolph Jochen M, Eickel Nina, Haller Claudia, Schindler Michael, Fackler Oliver T
Department of Virology, University of Heidelberg, INF 324, 69120 Heidelberg, Germany.
J Virol. 2009 Nov;83(22):11528-39. doi: 10.1128/JVI.01423-09. Epub 2009 Sep 2.
Nef, an important pathogenicity factor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV), elevates virus replication in vivo. Among other activities, Nef affects T-cell receptor (TCR) signaling via several mechanisms. For HIV-1 Nef these include alteration of the organization and function of the immunological synapse (IS) such as relocalization of the Lck kinase, as well as early inhibition of TCR/CD3 complex (TCR-CD3)-mediated actin rearrangements and tyrosine phosphorylation. Although most SIV and HIV-2 Nef alleles (group 2) potently downregulate cell surface TCR-CD3, this activity was lost in the viral lineage that gave rise to HIV-1 and its SIV counterparts (group 1). To address the contribution of TCR-CD3 downregulation to Nef effects on TCR signal initiation, we compared the activities of 18 group 1 and group 2 Nef proteins, as well as SIV Nef mutants with defects in TCR-CD3 downmodulation. We found that alteration of Lck's subcellular localization is largely conserved and occurs independently of actin remodeling inhibition or TCR-CD3 downregulation. Surprisingly, Nef proteins of both groups also strongly reduced TCR-induced actin remodeling and tyrosine phosphorylation on TCR-stimulatory surfaces and TCR-CD3 downmodulation competence by group 2 Nef proteins only slightly elevated these effects. Furthermore, Nef proteins from HIV-1 and SIV reduced conjugation between infected primary human T lymphocytes and Raji B cells and potently prevented F-actin polarization at the IS independently of their ability to downmodulate TCR-CD3. These results establish alterations of early TCR signaling events at the IS, including F-actin remodeling and relocalization of Lck, as evolutionary conserved activities of highly divergent lentiviral Nef proteins.
Nef是人类免疫缺陷病毒（HIV）和猿猴免疫缺陷病毒（SIV）的一种重要致病因子，可提高体内病毒复制水平。在其他活动中，Nef通过多种机制影响T细胞受体（TCR）信号传导。对于HIV-1 Nef而言，这些机制包括改变免疫突触（IS）的组织和功能，如Lck激酶的重新定位，以及早期抑制TCR/CD3复合物（TCR-CD3）介导的肌动蛋白重排和酪氨酸磷酸化。尽管大多数SIV和HIV-2 Nef等位基因（第2组）能有效下调细胞表面TCR-CD3，但在产生HIV-1及其SIV对应物的病毒谱系（第1组）中，这种活性丧失了。为了研究TCR-CD3下调对Nef影响TCR信号起始的作用，我们比较了18种第1组和第2组Nef蛋白以及TCR-CD3下调存在缺陷的SIV Nef突变体的活性。我们发现，Lck亚细胞定位的改变在很大程度上是保守的，并且独立于肌动蛋白重塑抑制或TCR-CD3下调而发生。令人惊讶的是，两组Nef蛋白也都强烈降低了TCR刺激表面上TCR诱导的肌动蛋白重塑和酪氨酸磷酸化，并且只有第2组Nef蛋白的TCR-CD3下调能力略微提高了这些效应。此外，HIV-1和SIV的Nef蛋白减少了感染的原代人T淋巴细胞与Raji B细胞之间的结合，并有效地阻止了IS处F-肌动蛋白极化，而这与其下调TCR-CD3的能力无关。这些结果表明，IS处早期TCR信号事件的改变，包括F-肌动蛋白重塑和Lck的重新定位，是高度分化的慢病毒Nef蛋白的进化保守活性。
