Dual role of IL-16 in dysregulated growth of CTCL cells

描述（由申请人提供）：与Sezary综合征相关的T细胞数量增加可能是过度增殖以及细胞凋亡减少的结果。然而，导致这些影响的机制尚不清楚。我们以前报道过IL-16是一种参与调节T细胞生长的双功能蛋白。分泌（成熟）部分已被归类为感受态因子，其通过与CD 4的细胞外缔合来调节T细胞生长，促进CD 25表达并从G 0期过渡到G1期。最近已经在T细胞的细胞核中检测到前片段（pro-IL-16），其中它通过调节Skp-2转录来影响增殖。Pro-IL-16作为支架蛋白发挥作用，其与辅因子GABP 1和HDAC-3相互作用以抑制Skp 2转录，因此间接调节与T细胞增殖相关的主要细胞周期蛋白激酶抑制剂之一p27 kip 1的降解。我们的初步数据现在表明，在CTCL患者的T细胞中，存在细胞内IL-16原的初始再分布，其特征在于细胞核中的优先损失。这种损失可归因于PDZ 1结构域中的突变，与核伴侣蛋白HSC 70结合的损失相关。细胞核IL-16原的丢失似乎还与观察到的在I-III期成熟IL-16分泌的增加相结合，因为细胞内储存被耗尽。此外，IL-16的产生总体上逐渐减少，这可能与启动子超甲基化有关。因此，我们假设CTCL的发作与IL-16启动子的高甲基化相关，导致蛋白质产生的进行性减少。此外，pro-IL-16的PDZ 1突变导致HSC 70结合丧失，显著降低核表达或功能，同时增加成熟蛋白的分泌。分泌的IL-16与表面表达的CD 4相互作用以进一步诱导恶性细胞中的细胞周期进展。在这些研究中，我们提出研究甲基化对IL-16启动子以及编码区内的影响;描述阻止pro-IL-16核转位的机制，并建立野生型pro-IL-16表达后Sezary T细胞的细胞效应;最后确定分泌的IL-16对T细胞增殖和T调节细胞的潜在扩增的作用。 公共卫生相关性：我们已经表明，细胞核pro-IL-16的功能是调节T细胞在细胞周期内的进展，并且在Sezary T细胞中，pro-IL-16已经失去了易位到细胞核中的能力，从而使细胞过度增殖。在这些研究中，我们建议识别参与调节IL-16原核转位的机制;表达的野生型IL-16原调节恶性T细胞过度增殖的能力;并研究分泌的IL-16诱导肿瘤抑制基因表达丧失和过度增殖的作用。这些研究的完成不仅将确定Sezary T细胞生长失调的机制，还将阐明潜在治疗方法的新方法。

DESCRIPTION (provided by applicant): The increase in T cell numbers associated with Sezary Syndrome likely occurs as a result of hyperproliferation as well as decreased apoptosis. The mechanisms involved resulting in these effects however are not clearly understood. We have previously reported that IL-16 is a bi-functional protein involved in regulation of T cell growth. The secreted (mature) portion has been classified as a competence factor that regulates T cell growth through extracellular association with CD4, promoting CD25 expression and transition from the G0 phase to G1. The pro-piece (pro-IL-16) has been recently detected in the nucleus of T cells where it affects proliferation through the regulation of Skp-2 transcription. Pro-IL-16 functions as a scaffold protein which interacts with co- factors GABP1 and HDAC-3 to suppress Skp2 transcription, therefore indirectly regulating degradation of one of the major cyclin kinase inhibitors associated with T cell proliferation, p27kip1. Our preliminary data now indicates that in T cells from CTCL patients there is an initial redistribution of intracellular pro-IL-16 characterized by preferential loss in the nucleus. This loss can be attributable to mutations in the PDZ1 domain, correlating to loss of binding by the nuclear chaperone protein HSC70. The loss of nuclear pro-IL-16 also appears to be combined with an observed increase in secretion of mature IL-16 in stages I-III as intracellular stores become depleted. In addition, there is an overall progressive reduction in the production of IL-16 that may be associated with promoter hypermethylation. It is our hypothesis therefore that the onset of CTCL is associated with hypermethylation of the IL-16 promoter resulting in a progressive reduction in protein production. In addition, mutations in PDZ1 of pro-IL-16 results in loss of HSC70 binding, significantly reducing nuclear expression or function, while increasing secretion of mature protein. Secreted IL-16 interacts with surface expressed CD4 to further induce cell cycle progression in the malignant cells. In these studies we propose to investigate the effects of methylation on the IL-16 promoter as well as within the coding region; to delineate the mechanism by which pro-IL-16 is prevented from nuclear translocation and establish cellular effects of Sezary T cells following expression of wild type pro-IL-16; and finally to determine the role of secreted IL-16 on T cell proliferation and potential expansion of T regulatory cells. PUBLIC HEALTH RELEVANCE: We have shown that nuclear pro-IL-16 functions to regulate T cell progression within the cell cycle and that in Sezary T cells pro-IL-16 has lost the ability to translocate into the nucleus rendering the cells hyperproliferative. In these studies we propose to identity the mechanisms involved in regulating nuclear translocation of pro-IL-16; the ability of expressed wild type pro-IL-16 to regulate hyperproliferation in malignant T cells; and to investigate the role of secreted IL-16 to induce loss of tumor suppressor expression with resultant hyperproliferation. Completion of these studies will not only identify a mechanism for dysregulated growth in Sezary T cells but will elucidate a novel approach to potential therapeutics.