Design of SMAC Peptidomimetics and Nonpeptidic Mimetics

描述(申请人提供)：Smac/Diablo是最近被发现的一种从线粒体释放的强有力的促凋亡蛋白。Smac通过结合X连锁LAP(XIAP)的BIR3结构域和其他LAP蛋白的BIR3结构域来发挥内源性拮抗凋亡蛋白抑制物(LAP)的作用，并取代该位点的caspase-9。Smac与XIAP的BIR3结构域的高分辨三维结构表明，它们之间的相互作用仅由其N端的4个Smac残基和XIAP BIR3结构域上的一个小而明确的结合槽所介导，这适合于设计小分子抑制剂。最近的一些研究表明，短的Smac多肽(4-8个残基)捆绑在载体多肽上进行细胞内递送，通过靶向LAP蛋白，有效地克服了体内外癌细胞的凋亡抵抗，同时对正常组织和动物没有毒性。因此，与Smac和caspase-9结合的XlAP中的BIR3结构域结合的Smac模拟物可能通过克服LAP蛋白过表达介导的癌细胞的凋亡抵抗而被开发为一类全新的抗癌药物。在这个项目中，我们建议设计、合成和表征高效的Smac多肽模拟物和非多肽模拟物，通过以下具体目标大大改善Smac多肽的细胞渗透性： 目标1.(A)基于已发表的Smac与XlAP BIR3络合物的高分辨率实验结构的Smac多肽模拟物和非多肽模拟物的结构设计。(B)。用X射线结晶学测定几种最有效的Smac模拟物的高分辨结构。 目标2.目标1.目标3.(A)中设计的Smac模拟物的化学合成用基于荧光偏振的方法测定这些Smac模拟物与XIAP的BIR3结构域的结合亲和力；用核磁共振方法确证了最有效的Smac模拟物与XlAP BIR3蛋白的结合。目的4.研究最有效的Smac模拟物的活性、特异性和分子作用机制。 设计高效性和细胞渗透性的SMAC模拟物是一个新的令人兴奋的研究领域。我们目前提出的研究是朝着我们的长期目标迈出的第一步，但也是必不可少的一步，我们的长期目标是通过靶向LAP蛋白介导的癌细胞凋亡抵抗来开发新型抗癌药物。

DESCRIPTION (provided by applicant): Smac/DIABLO was recently discovered as a potent pro-apoptotic protein released from mitochondria. Smac functions as an endogenous antagonist for the Inhibitors of Apoptosis Proteins (lAPs) by binding to the BIR3 domain of X-linked lAP (XIAP) and other lAP proteins and displace caspase-9 from this site. High resolution 3D structures of Smac in complex with the BIR3 domain of XIAP showed that the interaction between them is mediated by only four Smac residues at its N-terminus and a small but well-defined binding groove in the XIAP BIR3 domain, which is suitable for designing small molecule inhibitors. Several recent studies have shown that short Smac peptides (4-8 residues) tethered to a carrier peptide for intra-cellular delivery are effective to overcome apoptosis-resistance of cancer cells in vitro and in vivo by directing targeting lAP proteins, while having no toxicity to normal tissues or to animals. Hence, Smac mimetics that bind to the BIR3 domain in XlAP where Smac and caspase-9 bind may have great therapeutic potential to be developed as an entirely new class of anticancer drugs through overcoming apoptosis-resistance of cancer cells as mediated by lAP protein overexpression. In this project, we propose to design, synthesize and characterize highly potent Smac peptido-mimetics and nonpeptidic mimetics with much improved cell permeability over Smac peptides through the following Specific Aims: Aim 1. (a). Structure-based design of Smac peptido-mimetics and nonpeptidic mimetics based upon the published high-resolution experimental structures of Smac in complex with XlAP BIR3. (b). Determination of high-resolution structures of several most potent Smac mimetics through X-ray crystallography. Aim 2. Chemical synthesis of these Smac mimetics designed in Aim 1. Aim 3. (a). Determination of the binding affinities of these Smac mimetics to the BIR3 domain of XIAP by the fluorescence polarization-based method; (b). Conclusive confirmation of the binding of the most potent Smac mimetics to the XlAP BIR3 protein by NMR methods. Aim 4. Investigation of the activity, specificity and molecular mechanisms of action of the most potent Smac mimetics. Designing highly potent and cell-permeable Smac mimetics is a new and exciting area of research. Our current proposed research represents the first but an essential step toward our long-term goal of developing a novel anticancer drug through targeting apoptosis-resistance in cancer cells mediated by lAP proteins.