Role of Lipocalin 24p3 in Apoptosis and Leukemia

细胞程序性死亡，即细胞凋亡，是正常生理的一个重要方面，也是细胞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控的；在这些情况下，细胞凋亡是 由编码促凋亡蛋白的基因转录激活而诱导的。此应用程序侧重于 关于我们实验室发现的24p3/24p3R转录调控的促凋亡途径 在过去的几年里我一直在学习。我们最初确定24p3是经历最大 去细胞因子白介素3诱导细胞凋亡后的转录刺激 从属细胞。24p3是一种分泌型的Lipocalin，我们发现当它与 各种淋巴样细胞。这些和其他结果揭示了一种模型，在该模型中，剥夺IL-3激活24p3 转录，导致24p3的合成和分泌，从而通过 自分泌/旁分泌途径。我们分离了24p3细胞表面受体(24p3R)，发现24p3 通过一种新的途径诱导细胞凋亡，最终导致细胞内铁水平下降。这个 细胞内铁的减少会诱导促凋亡蛋白Bim的表达，从而导致细胞凋亡。 细胞内铁传递阻断BIM的诱导并抑制24p3添加或IL-3引起的细胞凋亡 剥夺。在这一应用中，我们提出了实验来研究24p3/24p3R促凋亡的作用 利用细胞系、患者样本和动物研究正常生理和骨髓增殖性疾病的途径 模特们。细胞内铁减少诱导细胞凋亡的基础尚不清楚。我们会 继续研究24p3和铁络合剂诱导的细胞凋亡途径。表达特征分析 RNA干扰将被用来识别24p3-和铁相关的转录激活基因 螯合剂介导的细胞凋亡。我们的初步结果提示24p3/24p3R通路可能在 糖皮质激素介导的细胞凋亡和糖皮质激素耐药，我们将继续研究。我们 已经发现BCR-ABL癌蛋白通过以下方式中和24p3/24p3R促凋亡途径 24p3和24p3R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。我们将继续分析这方面的一般性 结果研究了24p3和24p3R转录失控的基础。我们已经推导出24p3 纯合子基因敲除小鼠，将用于研究24p3/24p3R促凋亡的作用 Bcr/abl诱导的骨髓增殖性疾病的途径。

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.