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和细胞凋亡减少的结果。然而，导致这些影响的机制尚不清楚。我们之前报道过IL-16是一种参与T细胞生长调节的双功能蛋白。分泌（成熟）部分被归类为一种能力因子，通过细胞外与CD4的关联调节T细胞生长，促进CD25的表达并从G0期过渡到G1期。前体片段（pro-IL-16）最近在T细胞的细胞核中被检测到，它通过调节Skp-2的转录影响增殖。Pro-IL-16作为一种支架蛋白，与辅助因子GABP1和HDAC-3相互作用，抑制Skp2的转录，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p27kip1的降解。我们现在的初步数据表明，在CTCL患者的T细胞中，细胞内pro-IL-16的初始重新分配以细胞核中的优先损失为特征。这种缺失可归因于PDZ1结构域的突变，与核伴侣蛋白HSC70的结合缺失有关。核前IL-16的损失似乎也与观察到的成熟IL-16分泌在I-III期随着细胞内储存的耗尽而增加有关。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，我们的假设是，CTCL的发病与IL-16启动子的超甲基化有关，导致蛋白质产生的逐渐减少。此外，pro-IL-16的PDZ1突变导致HSC70结合缺失，细胞核表达或功能显著降低，成熟蛋白分泌增加。分泌的IL-16与表面表达的CD4相互作用，进一步诱导恶性细胞的细胞周期进程。在这些研究中，我们建议研究甲基化对IL-16启动子以及编码区内的影响；描述阻止前il -16核易位的机制，并建立野生型前il -16表达后seary T细胞的细胞效应；最后确定分泌IL-16对T细胞增殖和T调节性细胞潜在扩增的作用。公共卫生相关性：我们已经证明核前il -16在细胞周期内调节T细胞的进展，并且在Sezary T细胞中，前il -16失去了转运到细胞核中的能力，导致细胞过度增殖。在这些研究中，我们建议确定参与调节前il -16核转运的机制；表达野生型pro-IL-16调控恶性T细胞过度增殖的能力；并探讨分泌的IL-16在诱导肿瘤抑制因子表达缺失并导致过度增生中的作用。这些研究的完成不仅将确定seary T细胞生长失调的机制，而且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.