FUNCTIONS OF APOLIPOPROTEINS IN CANCER APOPTOSIS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。癌细胞在程序性细胞死亡（PCD）的遗传和生化途径中经常存在缺陷。Bcl-2家族成员在哺乳动物细胞凋亡和自噬两种类型的PCD调控中起关键作用。很明显，Bcl-2家族中仅具有BH3结构域的成员通过蛋白-蛋白相互作用调节Bcl-2家族成员的二聚和低聚，从而诱导细胞凋亡。然而，仅BH3结构域蛋白在自噬细胞死亡中的作用尚未得到充分探讨。人类基因组计划的完成以及各种公共数据库和序列分析算法的可用性使我们能够利用生物信息学数据挖掘方法鉴定两种新的bh3蛋白，载脂蛋白L6 （ApoL6）和ApoL1。先前我们发现，野生型ApoL6过表达诱导DLD-1细胞线粒体介导的凋亡，其特征是线粒体释放细胞色素c和Smac/DIABLO以及激活caspase 9，而ApoL6 BH3结构域缺失等位基因则没有。令人惊讶的是，我们最近的研究结果表明，ApoL1 （ApoL6的密切相关蛋白）诱导癌细胞自噬而非凋亡，其特征是LC3的激活和易位，以及空泡/自噬体的形成。自噬抑制剂阻断apol1诱导的细胞死亡。据我们所知，这是细胞内过量产生载脂蛋白（ApoL1）的第一个例子，该载脂蛋白仅具有bh3结构域，可诱导自噬细胞死亡。此外，为了探索ApoL1和ApoL6的基因组结构和功能基序，我们继续使用生物计算策略分析ApoL1和ApoL6的外显子-内含子边界（DNA），转录变体（RNA），蛋白质异构体和蛋白质基序/结构域。此外，我们扩大了该项目，研究了ApoL2和ApoL3的基因组结构和功能基序，这两个ApoLs成员可能在癌细胞死亡中发挥重要作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cancer cells frequently possess defects in the genetic and biochemical pathways of programmed cell death (PCD). Members of the Bcl-2 family play pivotal roles regulating two types of PCD in mammals: apoptosis and autophagy. It is evident that the BH3 domain-only members of the Bcl-2 family regulate di- and or oligo-merization of the Bcl-2 family members through protein-protein interaction and therefore induce apoptosis. However, the role of the BH3 domain-only proteins in autophagic cell death has not been fully explored. The completion of the Human Genome Project and the availability of various public databases and sequence analysis algorithms allowed us to utilize the bioinformatic data-mining approach to identify two novel BH3-only proteins, apolipoprotein L6 (ApoL6) and ApoL1. Previously we showed that overexpression of wild-type ApoL6 induced mitochondria-mediated apoptosis in DLD-1 cells as characterized by release of cytochrome c and Smac/DIABLO from mitochondria and activation of caspase 9, whereas ApoL6 BH3 domain deletion allele did not. Surprisingly, our recent results showed that ApoL1, a closely related protein of ApoL6, induced autophagic, rather than apoptotic, cell death in cancer cells as characterized by activation and translocation of LC3, and formation of vacuoles/autophagosomes. Inhibitors of autophagy block ApoL1-induced cell death. To our knowledge, this is the first example that intracellular overproduction of an apolipoprotein (ApoL1), which possesses a BH3-only domain, induces autophagic cell death. In addition, to explore genomic structure and functional motifs of ApoL1 and ApoL6, we have continued using biocomputing strategy to analyze exon-intron boundaries (DNA), transcript variants (RNA), protein isoforms and protein motifs/domains of ApoL1 and ApoL6. Furthermore, we have expanded this project to study the genomic structure and functional motifs of ApoL2 and ApoL3, two other members of ApoLs, which could potentially play important roles in cancer cell death.