DEREGULATION OF CELLULAR IKB KINASES BY HTLV1 TAX

人类T细胞白血病病毒1型（HTLV 1）是成人T细胞白血病的病原体，这是一种活化的CD 4 + T淋巴细胞的侵袭性且通常无法治愈的恶性肿瘤。 由HTLV 1编码的Tax癌蛋白有效地诱导转录因子NF-κ B的组成性核表达，NF-κ B在正常生长信号转导期间表现出快速但短暂的生物活性模式。 虽然先前的研究表明，这种病毒/宿主相互作用是HTLV 1介导的细胞转化的关键，但Tax对宿主NF-κ B通路作用的病理机制仍不清楚。 申请人的实验室最近发现，HTLV 1 Tax通过涉及位点特异性磷酸化、泛素化和NF-κ B的细胞质抑制剂IkappaB α降解的顺序过程触发NF-κ B诱导。 为了启动这种IkappaB α靶向功能，Tax结合并持续激活多蛋白IkappaB激酶复合物（IKK）。 与此形成鲜明对比的是，诱导NF-κ B的促炎细胞因子刺激短暂而非持续的IKK反应。 这项资助申请的中心假设是Tax介导的IKK激活是导致IkappaB α分解和HTLV 1感染的T细胞中NF-κ B的不适当组成性核输入的关键酶检查点。 因此，提出了一个高度综合的研究计划，以阐明HTLV 1的确切机制。 Tax激活IKK催化活性的持续功能表达。 为了实现这一总体目标，将使用免疫学、生物化学和遗传学方法的组合来确定（i）HTLV 1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，和（iii）细胞蛋白激酶和磷酸酶在Tax指导的IKK激活中的功能作用。 这项拟议的调查将描绘不仅税收物理上的多蛋白IKK信号转导装置的冲击，但也在分子水平上的病理病毒/宿主相互作用的整个功能架构。 反过来，确定Tax/IKK轴中这些重要的缺失环节将导致开发HTLV 1相关疾病治疗控制的创新策略。

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.