Role of Lipocalin 24p3 in Apoptosis and Leukemia

程序性细胞死亡，即细胞凋亡，是正常生理学的一个重要方面，也是细胞凋亡的发生和发展的一个重要方面。 癌症的治疗。某些凋亡途径是转录调节的;在这些情况下，凋亡是转录调节的。 由编码促凋亡蛋白的基因的转录激活诱导。本申请集中 24 p3/24 p3 R转录调节的促凋亡途径，我们的实验室发现， 在过去的几年里一直在学习。我们最初确定24 p3是一个基因， 白细胞介素3（IL-3）的去嘌呤诱导凋亡后的转录刺激 依赖细胞24 p3是一种分泌的脂质运载蛋白，我们发现当加入到一种 各种淋巴细胞。这些和其他结果揭示了一个模型，其中IL-3剥夺激活24 p3 转录，导致24 p3的合成和分泌，24 p3通过一个细胞因子诱导细胞凋亡。 自分泌/旁分泌途径。我们分离了24 p3细胞表面受体（24 p3 R），发现24 p3 通过一种新的途径诱导细胞凋亡，最终导致细胞内铁水平的降低。的 细胞内铁的减少诱导促凋亡蛋白Bim的表达，导致细胞凋亡。 细胞内铁传递阻断Bim的诱导并抑制由于24 p3添加或IL-3引起的凋亡 剥夺在本申请中，我们提出了实验来研究24 p3/24 p3 R促凋亡蛋白的作用。 使用细胞系、患者样品和动物模型在正常生理学和骨髓增生性疾病中的 模型细胞内铁减少诱导细胞凋亡的基础尚不清楚。我们将 继续表征由24 p3和铁螯合剂诱导的凋亡途径。表达谱 和RNA干扰将用于识别转录激活的基因参与24 p3-和铁 螯合剂介导的凋亡。我们的初步结果提示24 p3/24 p3 R通路可能在 糖皮质激素介导的细胞凋亡和糖皮质激素抵抗，我们将继续研究。我们 已经发现BCR-ABL癌蛋白通过以下方式抵消24 p3/24 p3 R促凋亡途径： 24 p3和24 p3 R的表达失调。这些结果揭示了一个新的和意想不到的方面， BCR-ABL促进细胞存活的机制。我们将继续分析其普遍性 研究了24 p3和24 p3 R基因转录调控异常的基础。我们得到了24 p3 纯合敲除小鼠，其将用于研究24 p3/24 p3 R促凋亡基因的贡献。 BCR/ABL诱导的骨髓增生性疾病的途径。

Programmed cell death, apoptosis, is a critical aspect of normal physiology as well as the genesis and treatment of cancer. Certain apoptotic pathways are transcriptionally regulated; in these cases, apoptosis is induced by the transcriptional activation of genes encoding proapoptotic proteins. This application focuses on the 24p3/24p3R transcriptionally-regulated proapoptotic pathway that our laboratory discovered and has been studying for the past several years. We originally identified 24p3 as the gene undergoing maximum transcriptional stimulation following induction of apoptosis by cytokine-deprivation of interleukin 3 (IL-3) dependent cells. 24p3 is a secreted lipocalin, which we have found induces apoptosis when added to a variety of lymphoid cells. These and other results revealed a model in which IL-3deprivation activates 24p3 transcription, leading to synthesis and secretion of 24p3, which induces apoptosis through an autocrine/paracrine pathway. We have isolated the 24p3 cell surface receptor (24p3R) and found that 24p3 induces apoptosis through a novel pathway culminating in a decrease in intracellular iron levels. The decrease in intracellular iron induces expression of the proapoptotic protein Bim, resulting in apoptosis. Intracellular iron delivery blocks induction of Bim and suppresses apoptosis due to 24p3 addition or IL-3 deprivation. In this application we propose experiments to study the role of the 24p3/24p3R proapoptotic pathway in normal physiology and myeloproliferative disease using cell lines, patient samples and animal models. The basis by which decreased intracellular iron induces apoptosis is not well understood. We will continue to characterize the apoptotic pathway induced by 24p3 and by iron chelators. Expression profiling and RNA interference will be used to identify transcriptionally activated genes involved in 24p3- and iron chelator-mediated apoptosis. Our preliminary results suggest a possible role for the 24p3/24p3R pathway in glucocorticoid-mediated apoptosis and glucocorticoid-resistance, which we will continue to investigate. We have found that the BCR-ABL oncoprotein counteracts the 24p3/24p3R proapoptotic pathway by misregulating expression of 24p3 and 24p3R. These results reveal a new and unanticipated aspect of the mechanism by which BCR-ABL promotes cell survival. We will continue to analyze the generality of this result and study the basis by which 24p3 and 24p3R transcription is misregulated. We have derived 24p3 homozygous knockout mice, which will be used to study the contribution of the 24p3/24p3R proapoptotic pathway to BCR/ABL-induced myeloproliferative disease.