Rebamipide and Derivatives are Potent, Selective Inhibitors of Histidine Phosphatase Activity of the Suppressor of T Cell Receptor Signaling Proteins

The suppressor of T cell receptor signaling (Sts) proteins
are
negative regulators of immune signaling. Genetic inactivation of these
proteins leads to significant resistance to infection. From a 590,000
compound high-throughput screen, we identified the 2-(1H)-quinolinone derivative, rebamipide, as a putative inhibitor of
Sts phosphatase activity. Rebamipide, and a small library of derivatives,
are competitive, selective inhibitors of Sts-1 with IC50 values from low to submicromolar. SAR analysis indicates that the
quinolinone, the acid, and the amide moieties are all essential for
activity. A crystal structure confirmed the SAR and reveals key interactions
between this class of compound and the protein. Although rebamipide
has poor cell permeability, we demonstrated that a liposomal preparation
can inactivate the phosphatase activity of Sts-1 in cells. These studies
demonstrate that Sts-1 enzyme activity can be pharmacologically inactivated
and provide foundational tools and insights for the development of
immune-enhancing therapies that target the Sts proteins.

T细胞受体信号抑制蛋白（Sts）家族蛋白充当免疫信号通路的负调控因子。该蛋白家族的遗传失活可导致宿主对感染的显著抵抗力。通过从590,000种化合物中进行的高通量筛选，我们鉴定出2-(1H)-喹啉酮衍生物，雷巴米普德，作为Sts磷酸酶活性的潜在抑制剂。雷巴米普德及其小规模的衍生物库被证明是Sts-1的竞争性、选择性抑制剂，其IC50值介于低至亚微摩尔之间。结构-活性关系（SAR）分析表明，喹啉酮、酸性基团和酰胺基团对于活性至关重要。晶体结构分析验证了SAR，并揭示了此类化合物与蛋白质之间的关键相互作用。尽管雷巴米普德具有较差的细胞渗透性，但我们证明了脂质体制剂能够使Sts-1在细胞中失活其磷酸酶活性。这些研究证明了Sts-1酶活性可以通过药理学手段被抑制，并为开发针对Sts蛋白的免疫增强疗法提供了基础工具和见解。