Coleman David R, Ren Zhiyong, Mandal Pijus K, Cameron Arlin G, Dyer Garrett A, Muranjan Seema, Campbell Martin, Chen Xiaomin, McMurray John S
Department of Neuro-Oncology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
J Med Chem. 2005 Oct 20;48(21):6661-70. doi: 10.1021/jm050513m.
Signal transducer and activator of transcription 3 (Stat3) is a cytosolic transcription factor that relates signals from the cell membrane directly to the nucleus where it, in complex with other proteins, initiates the transcription of antiapoptotic and cell cycling genes, e.g., Bcl-x(L) and cyclin D1. In normal cells Stat3 transduces signals from cytokines such as IL-6 and growth factors such as the epidermal growth factor. Stat3 is constitutively activated in a number of human tumors. Antisense and dominant negative gene delivery result in apoptosis and reduced cell growth, thus this protein is an attractive target for anticancer drug design. As part of our research on the design of Src homology 2 (SH2) directed peptidomimetic inhibitors of Stat3, in this paper we describe structure-activity relationship studies that provide information on the nature of peptide-protein interactions of a high-affinity phosphopeptide inhibitor of Stat3 dimerization and DNA binding, Ac-Tyr(PO3H2)-Leu-Pro-Gln-Thr-Val-NH2, peptide 1. There is a hydrophobic surface on the SH2 domain that can accommodate lipophilic groups on the N-terminus. Of the amino acids tested, leucine provided the highest affinity at pY+1 and its main chain NH is involved with a hydrogen bond with Stat3, presumably Ser636. cis-3,4-Methanoproline is optimal as a backbone constraint at pY+2. The side chain amide protons of Gln are required for high-affinity interactions. The C-terminal dipeptide, Thr-Val, can be replaced with groups ranging in size from methyl to benzyl. We synthesized a phosphopeptide incorporating groups that provided increases in affinity at each position. Thus, hydrocinnamoyl-Tyr(PO3H2)-Leu-cis-3,4-methanoPro-Gln-NHBn, 50, was the highest affinity peptide, exhibiting an IC50 of 125 nM versus 290 nM for peptide 1 in a fluorescence polarization assay.
信号转导及转录激活因子3（Stat3）是一种胞质转录因子，它将来自细胞膜的信号直接传递至细胞核，在细胞核中它与其他蛋白质形成复合物，启动抗凋亡和细胞周期基因（如Bcl-x(L)和细胞周期蛋白D1）的转录。在正常细胞中，Stat3转导来自细胞因子（如IL-6）和生长因子（如表皮生长因子）的信号。Stat3在多种人类肿瘤中持续激活。反义基因和显性负性基因传递可导致细胞凋亡并减少细胞生长，因此该蛋白是抗癌药物设计的一个有吸引力的靶点。作为我们对Src同源2（SH2）导向的Stat3拟肽抑制剂设计研究的一部分，本文描述了构效关系研究，这些研究提供了关于Stat3二聚化和DNA结合的高亲和力磷酸肽抑制剂Ac-Tyr(PO3H2)-Leu-Pro-Gln-Thr-Val-NH2（肽1）的肽-蛋白质相互作用性质的信息。SH2结构域上有一个疏水表面，可容纳N端的亲脂基团。在所测试的氨基酸中，亮氨酸在pY+1处提供了最高亲和力，其主链NH与Stat3（可能是Ser636）形成氢键。顺式-3,4-甲桥脯氨酸作为pY+2处的主链约束是最佳的。Gln的侧链酰胺质子是高亲和力相互作用所必需的。C端二肽Thr-Val可被大小从甲基到苄基不等的基团取代。我们合成了一种磷酸肽，其在每个位置引入的基团都提高了亲和力。因此，氢化肉桂酰-Tyr(PO3H2)-Leu-顺式-3,4-甲桥脯氨酸-Gln-NHBn（50）是亲和力最高的肽，在荧光偏振测定中，其IC50为125 nM，而肽1的IC50为290 nM。
