KU Leuven, Department of Cellular and Molecular Medicine, Laboratory of Chemical Biology, Herestraat 49 Box 802, 3000 Leuven, Belgium.
KU Leuven, Department of Cellular and Molecular Medicine, Laboratory of Cell Death Research and Therapy, Herestraat 49 Box 802, 3000 Leuven, Belgium.
ACS Chem Biol. 2020 Dec 18;15(12):3106-3111. doi: 10.1021/acschembio.0c00802. Epub 2020 Dec 8.
Inositol-requiring enzyme 1α (IRE1α) is one of three endoplasmic reticulum stress sensors. Upon activation of its kinase domain, IRE1α splices the mRNA substrate XBP1, which activates the unfolded protein response. IRE1α has emerged as a therapeutic target as its hyperactivation is implicated in various diseases. Kinase inhibiting RNase attenuator 6 (KIRA6) is an allosteric IRE1α inhibitor targeting the ATP binding pocket, resulting in effective blockage of the IRE1α-XBP1 pathway in mouse models of diabetes and pain. However, recent studies indicate that KIRA6 is not as selective as initially thought. Here, we developed a photoaffinity-based KIRA6 probe to reveal its selectivity. Surprisingly, the majority of off-targets that we identified were not protein kinases but mostly nucleotide-binding proteins. Furthermore, we found that the promiscuous off-target profile of KIRA6 is not cell-line-dependent. Overall, this study calls for caution when KIRA6 is used in IRE1α-targeted studies and illustrates the power of kinase photoaffinity probes.
肌醇需求酶 1α（IRE1α）是三种内质网应激传感器之一。其激酶结构域被激活后，IRE1α 可剪接 XBP1 mRNA 底物，从而激活未折叠蛋白反应。IRE1α 已成为一种治疗靶点，因为其过度激活与多种疾病有关。激酶抑制核糖核酸酶衰减因子 6（KIRA6）是一种变构 IRE1α 抑制剂，靶向 ATP 结合口袋，从而在糖尿病和疼痛的小鼠模型中有效阻断 IRE1α-XBP1 通路。然而，最近的研究表明，KIRA6 并不像最初想象的那样具有选择性。在这里，我们开发了一种基于光亲和性的 KIRA6 探针来揭示其选择性。令人惊讶的是，我们鉴定的大多数非靶点不是蛋白激酶，而是大多数核苷酸结合蛋白。此外，我们发现 KIRA6 的混杂非靶点谱不依赖于细胞系。总的来说，这项研究呼吁在 IRE1α 靶向研究中使用 KIRA6 时要谨慎，并说明了激酶光亲和探针的威力。
