Phosphoinositide 3 kinase mediates toll-like receptor 4-induced activation of NF-κB in endothelial cells
Phosphoinositide 3 kinase mediates toll-like receptor 4-induced activation of NF-κB in endothelial cells
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DOI：
10.1128/iai.71.8.4414-4420.2003
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发表时间：
2003-08-01
影响因子：
3.1
通讯作者：
Harlan, JM
中科院分区：
文献类型：
--
作者：
Li, XW;Tupper, JC;Harlan, JM
革兰氏阴性菌的许多促炎作用是由细菌脂多糖(LPS)与宿主细胞上表达的Toll样受体4(TLR4)相互作用引起的。TLR4信号导致了核因子-kappaB的激活和许多参与炎症反应的基因的转录。在这项研究中，我们研究了TLR4信号在人微血管内皮细胞中激活核因子-kappaB的信号通路。AKT是磷脂酰肌醇3激酶(PI3-K)的主要下游靶点，而PI3-K的激活是Akt磷酸化的必要条件和充分条件。因此，Akt激酶的激活被用作PI3-激酶活性的衡量标准。在稳定的转染系统中，髓系分化因子88(MyD88)和白介素1(IL-1)受体相关激酶1(IRAK-1)的显性-负性突变体(分别为MyD88-TIR和IRAK-DD)可阻断内毒素和IL-1β诱导的Akt激酶活性。与MyD88同源的MyD88适配子样蛋白(Mal)的显性负突变(Mal-P/H)不能抑制内毒素或IL-1β诱导的Akt活性。此外，p85的显性负性突变体(p85-dN)可抑制由内毒素和IL-1β诱导的NF-kappaB荧光素酶活性、IL-6的产生和IkappaBalpha的降解，但不能抑制肿瘤坏死因子α的刺激作用。Akt的显性负性突变体部分抑制了内毒素和IL-1β诱导的NF-kappaB荧光素酶活性。然而，表达结构性激活的Akt不能诱导NF-kappaB荧光素酶活性。这些发现表明，TLR4和IL-1R诱导的PI3-激酶活性是由接头蛋白MyD88和IRAK-I介导的，而不是MAL。此外，这些研究表明，PI3-激酶是导致内皮细胞核因子-kappaB激活的内毒素和IL-1β信号的重要介质，Akt是TLR4激活核因子-kappaB的必要条件，但不是充分条件。
Many of the proinflammatory effects of gram-negative bacteria are elicited by the interaction of bacterial lipopolysaccharide (LPS) with Toll-like receptor 4 (TLR4) expressed on host cells. TLR4 signaling leads to activation of NF-kappaB and transcription of many genes involved in the inflammatory response. In this study, we examined the signaling pathways involved in NF-kappaB activation by TLR4 signaling in human microvascular endothelial cells. Akt is a major downstream target of phosphoinositide 3 kinase (PI3-kinase), and PI3-kinase activation is necessary and sufficient for Akt phosphorylation. Consequently, Akt kinase activation was used as a measure of PI3-kinase activity. In a stable transfection system, dominant-negative mutants of myeloid differentiation factor 88 (MyD88) and interleukin-1 (IL-1) receptor-associated kinase 1 (IRAK-1) (MyD88-TIR and IRAK-DD, respectively) blocked Akt kinase activity in response to LPS and IL-1beta. A dominant-negative mutant (Mal-P/H) of MyD88 adapter-like protein (Mal), a protein with homology to MyD88, failed to inhibit LPS- or IL-1beta-induced Akt activity. Moreover, a dominant-negative mutant of p85 (p85-DN) inhibited the NF-kappaB luciferase activity, IL-6 production, and IkappaBalpha degradation elicited by LPS and IL-1beta but not that stimulated by tumor necrosis factor alpha. The dominant-negative mutant of Akt partially inhibited the NF-kappaB luciferase activity evoked by LPS and IL-1beta. However, expression of a constitutively activated Akt failed to induce NF-kappaB luciferase activity. These findings indicate that TLR4- and IL-1R-induced PI3-kinase activity is mediated by the adapter proteins MyD88 and IRAK-I but not Mal. Further, these studies suggest that PI3-kinase is an important mediator of LPS and IL-1beta signaling leading to NF-kappaB activation in endothelial cells and that Akt is necessary but not sufficient for NF-kappaB activation by TLR4.