Institute of Organic Chemistry , Leipzig University , Johannisallee 29 , 04103 Leipzig , Germany.
Center for Structural Biology , Vanderbilt University , 465 21st Avenue South, BIOSCI/MRBIII , Nashville , Tennessee 37221 , United States.
ACS Chem Biol. 2019 Apr 19;14(4):796-805. doi: 10.1021/acschembio.9b00137. Epub 2019 Mar 18.
STAT family proteins are important mediators of cell signaling and represent therapeutic targets for the treatment of human diseases. Most STAT inhibitors target the protein-protein interaction domain, the SH2 domain, but specificity for a single STAT protein is often limited. Recently, we developed catechol bisphosphates as the first inhibitors of STAT5b demonstrated to exhibit a high degree of selectivity over the close homologue STAT5a. Here, we show that the amino acid in position 566 of the linker domain, not the SH2 domain, is the main determinant of specificity. Arg566 in wild-type STAT5b favors tight binding of catechol bisphosphates, while Trp566 in wild-type STAT5a does not. Amino acid 566 also determines the affinity for a tyrosine-phosphorylated peptide derived from the EPO receptor for STAT5a and STAT5b, demonstrating the functional relevance of the STAT5 linker domain for the adjacent SH2 domain. These results provide the first demonstration that a residue in the linker domain can determine the affinity of nonpeptidic small-molecule inhibitors for the SH2 domain of STAT proteins. We propose targeting the interface between the SH2 domain and linker domain as a novel design approach for the development of potent and selective STAT inhibitors. In addition, our data suggest that the linker domain could contribute to the enigmatically divergent biological functions of the two STAT5 proteins.
STAT 家族蛋白是细胞信号转导的重要介质，是治疗人类疾病的治疗靶点。大多数 STAT 抑制剂针对的是蛋白-蛋白相互作用域，即 SH2 结构域，但对单一 STAT 蛋白的特异性往往有限。最近，我们开发了儿茶酚双磷酸酯作为第一个被证明对密切同源的 STAT5a 具有高度选择性的 STAT5b 抑制剂。在这里，我们表明，连接域中位置 566 的氨基酸，而不是 SH2 结构域，是决定特异性的主要因素。野生型 STAT5b 中的 Arg566 有利于儿茶酚双磷酸酯的紧密结合，而野生型 STAT5a 中的 Trp566 则不然。氨基酸 566 还决定了与来自 EPO 受体的 STAT5a 和 STAT5b 的酪氨酸磷酸化肽的亲和力，证明了 STAT5 连接域对于相邻 SH2 结构域的功能相关性。这些结果首次证明，连接域中的一个残基可以决定非肽小分子抑制剂与 STAT 蛋白的 SH2 结构域的亲和力。我们提出将 SH2 结构域和连接域之间的界面作为开发有效且选择性 STAT 抑制剂的新设计方法。此外，我们的数据表明，连接域可能有助于两种 STAT5 蛋白奇特的生物学功能的分歧。
