Mechanism and ultrasensitivity in Hedgehog signaling revealed by Patched1 disease mutations.
Mechanism and ultrasensitivity in Hedgehog signaling revealed by Patched1 disease mutations.
复制标题
Patched1 疾病突变揭示的 Hedgehog 信号传导机制和超敏感性。
DOI：
10.1073/pnas.2006800118
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发表时间：
2021
影响因子：
11.1
通讯作者：
Salic,Adrian
中科院分区：
文献类型：
--
作者：
Petrov,Kostadin;deAlmeidaMagalhaes,Taciani;Salic,Adrian
刺猬信号是动物胚胎发生的基础，其失调会导致癌症和出生缺陷。当Hedgehog配体抑制Patched1膜受体，缓解Patched1对gpcr样蛋白Smoothened的抑制时，该通路被触发。虽然功能缺失的Patched1突变如何导致过度活跃的Hedgehog信号传导和癌症是清楚的，但其他的Patched1突变如何抑制信号传导仍是未知的。在这里，我们对Patched1进行了定量的单细胞功能分析，结合数学模型，表明Patched1在超灵敏的状态下抑制Smoothened酶。基于这一分析，我们提出Patched1在纤毛中起作用，通过去除与细胞外富含半胱氨酸的结构域结合的胆固醇来催化平滑失活。与前脑畸形相关的Patched1突变体通过三种机制抑制信号传导：对Hedgehog配体的亲和力降低，催化活性升高，或对Smoothened底物的亲和力升高。我们的研究结果阐明了Patched1的神秘机制，并解释了Patched1突变如何导致出生缺陷。
Hedgehog signaling is fundamental in animal embryogenesis, and its dysregulation causes cancer and birth defects. The pathway is triggered when the Hedgehog ligand inhibits the Patched1 membrane receptor, relieving repression that Patched1 exerts on the GPCR-like protein Smoothened. While it is clear how loss-of-function Patched1 mutations cause hyperactive Hedgehog signaling and cancer, how other Patched1 mutations inhibit signaling remains unknown. Here, we develop quantitative single-cell functional assays for Patched1, which, together with mathematical modeling, indicate that Patched1 inhibits Smoothened enzymatically, operating in an ultrasensitive regime. Based on this analysis, we propose that Patched1 functions in cilia, catalyzing Smoothened deactivation by removing cholesterol bound to its extracellular, cysteine-rich domain. Patched1 mutants associated with holoprosencephaly dampen signaling by three mechanisms: reduced affinity for Hedgehog ligand, elevated catalytic activity, or elevated affinity for the Smoothened substrate. Our results clarify the enigmatic mechanism of Patched1 and explain how Patched1 mutations lead to birth defects.