Quaranta Maria Giovanna, Mattioli Benedetta, Spadaro Francesca, Straface Elisabetta, Giordani Luciana, Ramoni Carlo, Malorni Walter, Viora Marina
Department of Immunology, Istituto Superiore di Sanità Viale Regina Elena, 299 00161 Rome, Italy.
FASEB J. 2003 Nov;17(14):2025-36. doi: 10.1096/fj.03-0272com.
The accessory HIV-1 Nef protein plays a key role in AIDS pathogenesis. We recently demonstrated that exogenous Nef triggers phenotypic and functional differentiation of immature dendritic cells (DCs). Here we investigated whether the Nef-induced DC differentiation occurs with morphological remodeling and have focused on the interference of Nef in the signaling pathways that regulates DC maturation. We found that exogenous Nef enters immature DCs, promoting their functional and morphological differentiation. Specifically, Nef promotes interleukin (IL) -12 release, which closely fits with nuclear factor (NF) -kappaB activation. Nef induces rearrangement of actin microfilaments, leading to uropod and ruffle formation. Moreover, Nef increases the capacity of DCs to form clusters with allogeneic CD4+ T cells, improving immunological synapse formation. Searching for molecules involved in Nef-triggered signaling pathways driving the DC maturation, we found that Nef targets Vav and promotes its tyrosine phosphorylation, associated with its nucleus-to-cytoplasm redistribution. This has a direct effect on Vav guanine nucleotide exchange factor activity for the small GTPase Rac1. We hypothesize that targeting Vav, Nef modulates both early signaling events (such as cytoskeletal rearrangement) and delayed responses (such as transcriptional regulation), promoting DC differentiation. Our results highlight how Nef may enhance T lymphocyte activation, thus fostering virus dissemination, manipulating the DC arm of the immune response.
HIV-1辅助蛋白Nef在艾滋病发病机制中起关键作用。我们最近证明，外源性Nef可触发未成熟树突状细胞（DCs）的表型和功能分化。在此，我们研究了Nef诱导的DC分化是否伴随着形态重塑，并着重关注Nef对调节DC成熟的信号通路的干扰。我们发现外源性Nef进入未成熟DCs，促进其功能和形态分化。具体而言，Nef促进白细胞介素（IL）-12释放，这与核因子（NF）-κB激活密切相关。Nef诱导肌动蛋白微丝重排，导致尾足和褶皱形成。此外，Nef增强DCs与同种异体CD4+T细胞形成簇的能力，改善免疫突触形成。在寻找参与Nef触发的驱动DC成熟的信号通路的分子时，我们发现Nef靶向Vav并促进其酪氨酸磷酸化，这与其从细胞核到细胞质的重新分布有关。这对小GTP酶Rac1的Vav鸟嘌呤核苷酸交换因子活性有直接影响。我们假设，通过靶向Vav，Nef调节早期信号事件（如细胞骨架重排）和延迟反应（如转录调控），促进DC分化。我们的结果突出了Nef如何增强T淋巴细胞激活，从而促进病毒传播，操纵免疫反应的DC分支。
