Molecular Cardiology Research Laboratories, Texas Heart Institute, Houston, TX, United States.
Department of Biology and Chemistry, University of Houston, Houston, TX, United States.
Front Immunol. 2021 Jan 8;11:575085. doi: 10.3389/fimmu.2020.575085. eCollection 2020.
Leukocyte inflammatory responses require integrin cell-adhesion molecule signaling through spleen tyrosine kinase (Syk), a non-receptor kinase that binds directly to integrin β-chain cytoplasmic domains. Here, we developed a high-throughput screen to identify small molecule inhibitors of the Syk-integrin cytoplasmic domain interactions. Screening small molecule compound libraries identified the β-lactam antibiotics cefsulodin and ceftazidime, which inhibited integrin β-subunit cytoplasmic domain binding to the tandem SH2 domains of Syk (IC range, 1.02-4.9 µM). Modeling suggested antagonist binding to Syk outside the pITAM binding site. Ceftazidime inhibited integrin signaling Syk, including inhibition of adhesion-dependent upregulation of interleukin-1β and monocyte chemoattractant protein-1, but did not inhibit ITAM-dependent phosphorylation of Syk mediated by FcγRI signaling. Our results demonstrate a novel means to target Syk independent of its kinase and pITAM binding sites such that integrin signaling this kinase is abrogated but ITAM-dependent signaling remains intact. As integrin signaling through Syk is essential for leukocyte activation, this may represent a novel approach to target inflammation.
白细胞炎症反应需要整合素细胞粘附分子信号通过脾酪氨酸激酶（Syk），一种直接结合整合素β链细胞质结构域的非受体激酶。在这里，我们开发了一种高通量筛选方法来识别 Syk-整合素细胞质结构域相互作用的小分子抑制剂。筛选小分子化合物文库鉴定出β-内酰胺抗生素头孢噻肟和头孢他啶，它们抑制整合素β亚基细胞质结构域与 Syk 的串联 SH2 结构域结合（IC 范围，1.02-4.9µM）。建模表明拮抗剂结合在 pITAM 结合位点之外的 Syk 上。头孢他啶抑制整合素信号转导 Syk，包括抑制黏附依赖性白细胞介素-1β和单核细胞趋化蛋白-1的上调，但不抑制 FcγRI 信号介导的 ITAM 依赖性 Syk 磷酸化。我们的结果表明了一种靶向 Syk 的新方法，该方法不依赖其激酶和 pITAM 结合位点，从而阻断该激酶的整合素信号转导，但保留 ITAM 依赖性信号转导。由于 Syk 通过整合素信号转导对于白细胞的激活至关重要，这可能代表了一种靶向炎症的新方法。
