Department of Oncological Sciences, Department of Biochemistry, and Department of Bioengineering, University of Utah School of Medicine, Salt Lake City, UT, USA.
Washington University School of Medicine, St. Louis, MO, USA.
Nat Struct Mol Biol. 2022 Oct;29(10):990-999. doi: 10.1038/s41594-022-00838-z. Epub 2022 Oct 6.
The Hedgehog (Hh) cascade is central to development, tissue homeostasis and cancer. A pivotal step in Hh signal transduction is the activation of glioma-associated (GLI) transcription factors by the atypical G protein-coupled receptor (GPCR) SMOOTHENED (SMO). How SMO activates GLI remains unclear. Here we show that SMO uses a decoy substrate sequence to physically block the active site of the cAMP-dependent protein kinase (PKA) catalytic subunit (PKA-C) and extinguish its enzymatic activity. As a result, GLI is released from phosphorylation-induced inhibition. Using a combination of in vitro, cellular and organismal models, we demonstrate that interfering with SMO-PKA pseudosubstrate interactions prevents Hh signal transduction. The mechanism uncovered echoes one used by the Wnt cascade, revealing an unexpected similarity in how these two essential developmental and cancer pathways signal intracellularly. More broadly, our findings define a mode of GPCR-PKA communication that may be harnessed by a range of membrane receptors and kinases.
刺猬 (Hh) 级联反应是发育、组织稳态和癌症的核心。Hh 信号转导中的关键步骤是通过非典型 G 蛋白偶联受体 (GPCR) SMOOTHENED (SMO) 激活神经胶质瘤相关 (GLI) 转录因子。SMO 如何激活 GLI 尚不清楚。在这里，我们表明 SMO 使用诱饵底物序列来物理阻断环腺苷酸依赖性蛋白激酶 (PKA) 催化亚基 (PKA-C) 的活性位点并使其酶活性熄灭。结果，GLI 从磷酸化诱导的抑制中释放出来。我们使用体外、细胞和生物模型的组合证明，干扰 SMO-PKA 伪底物相互作用可阻止 Hh 信号转导。所揭示的机制与 Wnt 级联反应所使用的机制相呼应，揭示了这两个重要的发育和癌症途径在细胞内信号传递方面的惊人相似性。更广泛地说，我们的发现定义了一种 GPCR-PKA 通讯模式，可能被一系列膜受体和激酶利用。
