DEREGULATION OF CELLULAR IKB KINASES BY HTLV1 TAX

HTLV1 税对细胞 IKB 激酶的放松管制

• 批准号: 6514112
• 负责人: DEAN BALLARD
• 金额: $ 37.91万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2004-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6514112
• 关键词: DNA binding protein; binding sites; biological signal transduction; cytokine; enzyme activity; enzyme complex; enzyme structure; gene induction /repression; helper T lymphocyte; host organism interaction; human T cell lymphotropic virus type 1; immunoprecipitation; inhibitor /antagonist; molecular assembly /self assembly; molecular cloning; nuclear factor kappa beta; oncoproteins; phosphoprotein phosphatase; phosphorylation; protein binding; protein kinase; protein protein interaction; virus protein

Human T-cell leukemia virus type 1 (HTLV1) is the etiologic agent of adult T-cell leukemia, an aggressive and often untreatable malignancy of activated CD4+ T lymphocytes. The Tax oncoprotein encoded by HTLV1 potently induces the constitutive nuclear expression of transcription factor NF-kappaB, which exhibits a rapid but transient pattern of biologic activity during normal growth-signal transduction. Although prior investigations have indicated that this viral/host interaction is pivotal for HTLV1-mediated cellular transformation, the pathologic mechanism of Tax action on the host NF-kappaB pathway remains unclear. The applicant's laboratory has recently discovered that HTLV1 Tax triggers NF-kappaB induction via a sequential process involving site-specific phosphorylation, ubiquitination, and degradation of IkappaBalpha, a cytoplasmic inhibitor of NF-kappaB. To initiate this IkappaBalpha targeting function, Tax binds to and persistently activates a multiprotein IkappaB kinase complex (IKK). In sharp contrast, pro-inflammatory cytokines that induce NF-kappaB stimulate a transient rather than persistent IKK response. The central hypothesis of this grant application is that Tax-directed IKK activation is the crucial enzymatic checkpoint leading to IkappaBalpha breakdown and the inappropriate constitutive nuclear import of NF-kappaB in HTLV1-infected T cells. Accordingly, a highly-integrated research program is proposed to elucidate the precise mechanism by which HTLV1. Tax activates the persistent functional expression of IKK catalytic activity. To achieve this overall objective, a combination of immunological, biochemical, and genetic approaches will be used to determine (i) the stability, size distribution, and subunit composition of Tax/IKK complexes in HTLV1-infected T cells, (ii) the molecular mechanism responsible for the formation of these pathologic Tax/IKK complexes, and (iii) the functional role of cellular protein kinases and phosphatases in Tax-directed IKK activation. This proposed investigation will delineate not only how Tax impinges physically on the multiprotein IKK signal transduction apparatus but also the entire functional architecture of this pathologic viral/host interaction at the molecular level. In turn, identification of these important missing links in the Tax/IKK axis will lead to the development of innovative strategies for the therapeutic control of HTLV1-associated diseases.

人类T细胞白血病病毒1型（HTLV1）是成人T细胞白血病的病因，这是一种活化CD4+ T淋巴细胞的侵袭性且通常无法治疗的恶性肿瘤。HTLV1编码的taxoncoprotein能诱导转录因子NF-kappaB的组成核表达，在正常生长信号转导过程中表现出快速而短暂的生物活性模式。尽管先前的研究表明，这种病毒/宿主相互作用对于htlv1介导的细胞转化至关重要，但Tax作用于宿主NF-kappaB通路的病理机制尚不清楚。申请人的实验室最近发现HTLV1 Tax通过一系列过程触发NF-kappaB诱导，包括位点特异性磷酸化、泛素化和ikappabα （NF-kappaB的细胞质抑制剂）的降解。为了启动IkappaBalpha靶向功能，Tax结合并持续激活多蛋白ikapabb激酶复合物（IKK）。与之形成鲜明对比的是，诱导NF-kappaB的促炎细胞因子刺激的是短暂而非持续的IKK反应。这项资助申请的中心假设是，在htlv1感染的T细胞中，税收导向的IKK激活是导致IkappaBalpha分解和NF-kappaB不适当的组成核输入的关键酶检查点。因此，提出了一个高度集成的研究方案来阐明HTLV1的精确机制。Tax激活IKK催化活性的持续功能性表达。为了实现这一总体目标，将使用免疫学、生化和遗传学方法的结合来确定(i) htlv1感染的T细胞中Tax/IKK复合物的稳定性、大小分布和亚基组成，（ii）负责形成这些病理性Tax/IKK复合物的分子机制，以及（iii）细胞蛋白激酶和磷酸酶在税收导向的IKK激活中的功能作用。这项拟议的研究不仅将描述Tax如何在物理上影响多蛋白IKK信号转导装置，而且还将在分子水平上描述这种病理性病毒/宿主相互作用的整个功能结构。反过来，确定Tax/IKK轴中这些重要的缺失环节将导致htlv1相关疾病治疗控制的创新策略的发展。