Activation of mitogen-activated protein kinase and NF-κB pathways by a Kaposi's sarcoma-associated herpesvirus K15 membrane protein
Activation of mitogen-activated protein kinase and NF-κB pathways by a Kaposi's sarcoma-associated herpesvirus K15 membrane protein
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DOI：
10.1128/jvi.77.17.9346-9358.2003
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发表时间：
2003-09-01
影响因子：
5.4
通讯作者：
Schulz, TF
中科院分区：
文献类型：
--
作者：
Brinkmann, MM;Glenn, M;Schulz, TF
卡波西肉瘤相关疱疹病毒（也称为人类疱疹病毒8）的K15基因由8个可变剪接外显子组成，并已被预测编码具有可变数量的跨膜区和一个共同的C-末端胞质结构域的膜蛋白，该结构域具有SH 2和SH 3结构域以及肿瘤坏死因子受体相关因子的推定结合位点。这些特征使人联想到EB病毒的潜伏膜蛋白LMP-1和LMP 2A，以及更远的相关γ（2）-疱疹病毒疱疹病毒松鼠猴和疱疹病毒ateles的STP、Tip和Tio蛋白。这些病毒膜蛋白可以激活许多细胞内信号通路。因此，我们研究了不同的K15编码的蛋白质启动细胞内信号的能力。我们发现，一个45 kDa的K15蛋白来自所有8个K15外显子，并含有12个预测的跨膜结构域，除了细胞质结构域激活Ras/丝裂原活化蛋白激酶（MAPK）和NF-κ B途径，以及（更弱）的c-Jun N-末端激酶/SAPK途径。MAPK和NF-κ B通路的激活需要在推定的SH 2结合位点（YEEVL）内的酪氨酸残基481的磷酸化。该基序被酪氨酸激酶Src、Lck、Yes、Hck和Fyn磷酸化。含有YEEVL基序的区域与肿瘤坏死因子受体相关因子2（TRAF-2）相互作用，并且显性负性TRAF-2突变体抑制K15介导的Ras/MAPK通路的活化，表明TRAF-2参与这些信号通路的起始。相反，几个较小的K15蛋白亚型激活这些途径只有微弱的。然而，所有测试的K15亚型都定位于脂筏中，这表明掺入脂筏不足以启动信号传导。K15的其他区域，可能位于外显子2至5，因此可能有助于激活这些途径。这些发现表明，45-kDa K15蛋白参与与LMP 1、LMP 2A、STP、Tip和Tio类似的途径，但结合了LMP 1和LMP 2A或STP和Tip之间分离的功能特征。
The K15 gene of Kaposi's sarcoma-associated herpesvirus (also known as human herpesvirus 8) consists of eight alternatively spliced exons and has been predicted to encode membrane proteins with a variable number of transmembrane regions and a common C-terminal cytoplasmic domain with putative binding sites for SH2 and SH3 domains, as well as for tumor necrosis factor receptor-associated factors. These features are reminiscent of the latent membrane proteins LMP-1 and LMP2A of Epstein-Barr virus and, more distantly, of the STP, Tip, and Tio proteins of the related gamma(2)-herpesviruses herpesvirus saimiri and herpesvirus ateles. These viral membrane proteins can activate a number of intracellular signaling pathways. We have therefore examined the abilities of different K15-encoded proteins to initiate intracellular signaling. We found that a 45-kDa K15 protein derived from all eight K15 exons and containing 12 predicted transmembrane domains in addition to the cytoplasmic domain activated the Ras/mitogen-activated protein kinase (MAPK) and NF-kappaB pathways, as well as (more weakly) the c-Jun N-terminal kinase/SAPK pathway. Activation of the MAPK and NF-kappaB pathways required phosphorylation of tyrosine residue 481 within a putative SH2-binding site (YEEVL). This motif was phosphorylated by the tyrosine kinases Src, Lck, Yes, Hck, and Fyn. The region containing the YEEVL motif interacted with tumor necrosis factor receptor-associated factor 2 (TRAF-2), and a dominant negative TRAF-2 mutant inhibited the K15-mediated activation of the Ras/MAPK pathway, suggesting the involvement of TRAF-2 in the initiation of these signaling routes. In contrast, several smaller K15 protein isoforms activated these pathways only weakly. All of the K15 isoforms tested were, however, localized in lipid rafts, suggesting that incorporation into lipid rafts is not sufficient to initiate signaling. Additional regions of K15, located presumably in exons 2 to 5, may therefore contribute to the activation of these pathways. These findings illustrate that the 45-kDa K15 protein engages pathways similar to LMP1, LMP2A, STP, Tip, and Tio but combines functional features that are separated between LMP1 and LMP2A or STP and Tip.