Department of Chemistry, University of Washington, Seattle, United States.
Elife. 2023 Aug 7;12:e85444. doi: 10.7554/eLife.85444.
Multiple signaling pathways regulate the kinase GSK3β by inhibitory phosphorylation at Ser9, which then occupies the GSK3β priming pocket and blocks substrate binding. Since this mechanism should affect GSK3β activity toward all primed substrates, it is unclear why Ser9 phosphorylation does not affect other GSK3β-dependent pathways, such as Wnt signaling. We used biochemical reconstitution and cell culture assays to evaluate how Wnt-associated GSK3β is insulated from cross-activation by other signals. We found that the Wnt-specific scaffold protein Axin allosterically protects GSK3β from phosphorylation at Ser9 by upstream kinases, which prevents accumulation of pS9-GSK3β in the Axin•GSK3β complex. Scaffold proteins that protect bound proteins from alternative pathway reactions could provide a general mechanism to insulate signaling pathways from improper crosstalk.
多种信号通路通过丝氨酸 9 位的抑制性磷酸化来调节激酶 GSK3β，磷酸化后占据 GSK3β 的预激活口袋并阻止底物结合。由于这种机制应该影响 GSK3β 对所有预激活底物的活性，因此尚不清楚为什么丝氨酸 9 位的磷酸化不会影响其他依赖于 GSK3β 的途径，如 Wnt 信号通路。我们使用生化重构和细胞培养实验来评估 Wnt 相关的 GSK3β 如何免受其他信号的交叉激活。我们发现，Wnt 特异性支架蛋白 Axin 通过变构方式保护 GSK3β 免受上游激酶的 Ser9 磷酸化，从而防止 pS9-GSK3β 在 Axin•GSK3β 复合物中的积累。保护结合蛋白免受替代途径反应的支架蛋白可能为隔离信号通路免受不当串扰提供一种通用机制。
