McJilton Meagan A, Van Sikes C, Wescott Ginger G, Wu Daqing, Foreman Tonia L, Gregory Christopher W, Weidner Douglas A, Harris Ford O, Morgan Lasater A, Mohler James L, Terrian David M
Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA.
Oncogene. 2003 Sep 11;22(39):7958-68. doi: 10.1038/sj.onc.1206795.
Prostatic glandular epithelial cells express protein kinase Cepsilon (PKCepsilon ), an oncoprotein that coordinately disrupts the reactivation of the tumor suppressor Rb, derepressess transcriptional elongation of the c-myc oncogene, and propagates survival signals in LNCaP cells. Since the activation of such a program may contribute to the progression of human prostate cancer, a proteomic analysis was performed to gain a more global perspective on the signaling network that PKCepsilon might be capable of engaging in prostate cancer cells. Using CWR22 xenografts, we identified at least 18 different structural, signaling, and stress-related proteins that associated with PKCepsilon, including an interaction with the proapoptotic protein Bax that was novel to recurrent CWR22 tumors. An investigation into the biological significance of the PKCepsilon association with Bax provided the first evidence of an inverse relationship between endogenous levels of PKCepsilon and susceptibility of prostate cancer cells to the apoptotic effects of phorbol esters. Western blot and antisense experiments demonstrated that CWR-R1 cells expressed moderate levels of PKCepsilon and relied on this protein to survive in the presence of phorbol esters, while the apoptosis normally induced by phorbol esters in PKCepsilon -deficient LNCaP cells was dependent on the presence of Bax. Forced expression of PKCepsilon in LNCaP cells was sufficient to confer a significant resistance to phorbol esters and this resistance was associated with an inhibition of phorbol ester-induced Bax conformational rearrangements that are important for Bax oligomerization, mitochondrial integration, and cytochrome c release. Considered in their entirety, our data suggest that an association of PKCepsilon with Bax may neutralize apoptotic signals propagated through a mitochondrial death-signaling pathway.
前列腺腺上皮细胞表达蛋白激酶Cε（PKCε），这是一种癌蛋白，它协同破坏肿瘤抑制因子Rb的重新激活，解除对c - myc癌基因转录延伸的抑制，并在LNCaP细胞中传递存活信号。由于这种程序的激活可能有助于人类前列腺癌的进展，因此进行了蛋白质组学分析，以更全面地了解PKCε可能在前列腺癌细胞中参与的信号网络。使用CWR22异种移植瘤，我们鉴定出至少18种与PKCε相关的不同结构、信号和应激相关蛋白，包括与促凋亡蛋白Bax的相互作用，这在复发性CWR22肿瘤中是新发现的。对PKCε与Bax关联的生物学意义的研究首次提供了证据，表明PKCε的内源性水平与前列腺癌细胞对佛波酯凋亡作用的敏感性之间存在反比关系。蛋白质印迹和反义实验表明，CWR - R1细胞表达中等水平的PKCε，并依赖这种蛋白在佛波酯存在的情况下存活，而PKCε缺陷的LNCaP细胞中通常由佛波酯诱导的凋亡依赖于Bax的存在。在LNCaP细胞中强制表达PKCε足以赋予对佛波酯的显著抗性，并且这种抗性与抑制佛波酯诱导的Bax构象重排有关，而这种重排对于Bax寡聚化、线粒体整合和细胞色素c释放很重要。综合考虑，我们的数据表明PKCε与Bax的关联可能中和通过线粒体死亡信号通路传播的凋亡信号。
