Recruitment of PKC-Beta to Lipid Rafts Mediates Apoptosis-Resistance in Chronic Lymphocytic Leukemia Expressing Zap-70.
Recruitment of PKC-Beta to Lipid Rafts Mediates Apoptosis-Resistance in Chronic Lymphocytic Leukemia Expressing Zap-70.
复制标题
PKC-Beta 募集至脂筏介导表达 Zap-70 的慢性淋巴细胞白血病的细胞凋亡抗性。
DOI：
10.1182/blood.v114.22.2354.2354
复制
发表时间：
2009
期刊：
影响因子：
20.3
通讯作者：
C. M. Z. Büschenfelde
中科院分区：
文献类型：
--
作者：
I. Ringshausen;M. Wagner;G. Lutzny;M. Oelsner;Y. Feuerstacke;T. Decker;C. Bogner;C. Peschel;C. M. Z. Büschenfelde
摘要 2354
海报板 II-331
CLL 的发病机制中存在程序性细胞死亡（细胞凋亡）的缺陷。大约十年前，人们发现 CLL 患者可分为惰性白血病病程患者和患有更具侵袭性疾病的患者，通常需要频繁化疗并最终发展为化疗难治性状态。后一组患者异常表达 T 细胞相关蛋白 ZAP-70。本研究的目的是确定这两个 CLL 亚组发病机制的分子差异。为了研究细胞凋亡程序的差异，我们使用了来自未经治疗的 ZAP-70 阴性和阳性患者的原代 CLL 细胞。在这里，我们表明，仅在患有侵袭性疾病变异的患者中，ZAP-70 的表达增强了与 B 细胞受体 (BCR) 相关的信号，并将蛋白激酶 C-β (PKC-β) 招募到脂筏结构域中。随后，PKC-β 被激活并从质膜穿梭至线粒体。通过使用免疫共沉淀实验和 PKC-β 特异性小分子抑制剂，我们发现抗凋亡蛋白 Bcl-2 及其拮抗 BH3 蛋白 Bim 是 PKC-β 的推定底物。 PKC-β 介导的 Bcl-2 磷酸化通过增加其隔离更多促凋亡 Bim 的能力来增强其抗凋亡功能。此外，PKC-β 对 Bim 的磷酸化导致其蛋白酶体降解。因此，高水平的磷酸化 Bcl-2 和低水平的 Bim 是 ZAP-70 阳性、侵袭性 CLL 的标志。重要的是，在抑制细胞凋亡方面，Bcl-2 的转录后修饰似乎超过了 Bcl-2 的绝对表达。我们证明这些细胞受到强有力的保护，免受化疗引起的细胞毒性应激。我们的数据表明，PKC-β 的组成型激活直接参与 ZAP-70 阳性 CLL 的细胞凋亡缺陷。我们最终证明，靶向 PKC-β 是治疗 CLL 患者的一种有吸引力的方法。 Enzastaurin 是一种 PKC-β 特异性抑制剂，目前正在针对癌症患者进行 I/II 期临床试验。我们的数据表明，该化合物在 CLL 细胞中具有高度活性，并增强标准化疗药物的细胞毒性作用。我们的研究结果证明，PKC-β 的组成型激活通过改变凋亡调节蛋白 Bcl-2 和 Bim 的功能，直接参与侵袭性 CLL 的发病机制。这些变化使细胞在疾病的侵袭性下处于更抗凋亡的状态。使用 Enzastaurin 等小分子抑制剂靶向 PKC-β 可能会提供一种控制甚至治愈 CLL 的新治疗策略。
披露：没有需要声明的相关利益冲突。
Abstract 2354
Poster Board II-331
A defect in the programmed cell death, apoptosis, is implemented in the pathogenesis of CLL. About ten years ago, it became evident that patients with CLL can be divided into those with an indolent course of the leukaemia and those which suffer from a more aggressive disease, typically requiring frequent chemotherapy and ultimately develop a chemotherapy-refractory state. The latter group of patients aberrantly express the T-cell associated protein ZAP-70. The object of this study was to identify the molecular differences underlying the pathogenesis of these two CLL subgroups. To study differences in the apoptotic program we used primary CLL cells derived from untreated ZAP-70 negative and positive patients. Here we show that the expression of ZAP-70 enhances the signals associated with the B-cell receptor (BCR) and recruits protein kinase C-beta (PKC-beta) into lipid raft domains only in patients with an aggressive variant of the disease. Subsequently, PKC-beta is activated and shuttles from the plasma membrane into the mitochondria. By using co-immunoprecipitation experiments and PKC-beta specific small molecule inhibitors we unravel that the anti-apoptotic protein Bcl-2 and its antagonistic BH3-protein Bim are putative substrates for PKC-beta. PKC-beta mediated phosphorylation of Bcl-2 augments its anti-apoptotic function by increasing its ability to sequester more pro-apoptotic Bim. In addition, the phosphorylation of Bim by PKC-beta leads to its proteasomal degradation. Therefore, high levels of phospho-Bcl-2 and low levels of Bim are a hallmark of ZAP-70 positive, aggressive CLL. Importantly, posttranscriptional modifications of Bcl-2 seem to outweigh the absolute expression of Bcl-2 with respect to the suppression of apoptosis. We demonstrate that these cells are strongly protected from chemotherapy-induced cytotoxic stress. Our data indicate that the constitutive activation of PKC-beta is directly involved in the apoptotic defect in ZAP-70 positive CLL. We finally show that targeting PKC-beta is an attractive approach to the treatment of CLL patients. Enzastaurin is a PKC-beta specific inhibitor and currently tested in clinical phase I/II trials for cancer patients. Our data demonstrate that this compound is highly active in CLL cells and augments the cytotoxic effects of standard chemotherapeutic drugs. Our results provide evidence that the constitutive activation of PKC-beta is directly implicated in the pathogenesis of aggressive CLL by altering the function of the apoptosis-regulating proteins Bcl-2 and Bim. These changes confer cells to a more anti-apoptotic state with aggressiveness of the disease. Targeting PKC-beta with small-molecule inhibitors like Enzastaurin might offer a new therapeutic strategy to control or even cure CLL.
Disclosures: No relevant conflicts of interest to declare.