Design of SMAC Peptidomimetics and Nonpeptidic Mimetics

描述（由申请人提供）：最近发现Smac/DIABLO是一种从线粒体释放的有效促凋亡蛋白。Smac通过结合X-连接的IAP（XIAP）的BIR 3结构域和其他IAP蛋白并从该位点置换胱天蛋白酶-9而作为凋亡蛋白抑制剂（IAP）的内源性拮抗剂发挥作用。Smac与XIAP的BIR 3结构域复合物的高分辨率三维结构表明，它们之间的相互作用仅由其N端的四个Smac残基和XIAP BIR 3结构域中的小但定义明确的结合沟介导，这适合于设计小分子抑制剂。最近的几项研究表明，与载体肽连接用于细胞内递送的短Smac肽（4-8个残基）通过直接靶向IAP蛋白在体外和体内有效克服癌细胞的凋亡抗性，同时对正常组织或动物没有毒性。因此，结合至XIAP中的BIR 3结构域（其中Smac和半胱天冬酶-9结合）的Smac模拟物可具有巨大的治疗潜力，以通过克服由IAP蛋白过表达介导的癌细胞的凋亡抗性而被开发为全新类别的抗癌药物。在这个项目中，我们提出设计，合成和表征高效的Smac肽模拟物和非肽模拟物，通过以下具体目的，这些肽模拟物具有比Smac肽更好的细胞渗透性： 目标1.（一）. Smac肽模拟物和非肽模拟物的基于结构的设计基于Smac与XIAP BIR 3复合的已公开的高分辨率实验结构。（B）。通过X射线晶体学确定几种最有效的Smac模拟物的高分辨率结构。 目标2.化学合成在目标1中设计的这些Smac模拟物。目标3。（一）.通过基于荧光偏振的方法确定这些Smac模拟物与XIAP的BIR 3结构域的结合亲和力;（B）。通过NMR方法对最有效的Smac模拟物与X1 AP BIR 3蛋白的结合的结论性确认。目标4。研究最有效的Smac模拟物的活性、特异性和分子作用机制。 设计高效和细胞可渗透的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代表了我们通过靶向由IAP蛋白介导的癌细胞中的耐药性来开发新型抗癌药物的长期目标的第一步，但这是必不可少的一步。

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.