Department of Developmental and Cell Biology, University of California, Irvine, CA, USA.
Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA, USA.
Life Sci Alliance. 2022 Jul 13;5(11). doi: 10.26508/lsa.202101353. Print 2022 Nov.
Crosstalk between the Hedgehog and MAPK signaling pathways occurs in several types of cancer and contributes to clinical resistance to Hedgehog pathway inhibitors. Here we show that MAP kinase-mediated phosphorylation weakens the binding of the GLI1 transcription factor to its negative regulator SUFU. ERK2 phosphorylates GLI1 on three evolutionarily conserved target sites (S102, S116, and S130) located near the high-affinity binding site for SUFU; these phosphorylations cooperate to weaken the affinity of GLI1-SUFU binding by over 25-fold. Phosphorylation of any one, or even any two, of the three sites does not result in the level of SUFU release seen when all three sites are phosphorylated. Tumor-derived mutations in R100 and S105, residues bordering S102, also diminish SUFU binding, collectively defining a novel evolutionarily conserved SUFU affinity-modulating region. In cultured mammalian cells, GLI1 variants containing phosphomimetic substitutions of S102, S116, and S130 displayed an increased ability to drive transcription. We conclude that multisite phosphorylation of GLI1 by ERK2 or other MAP kinases weakens GLI1-SUFU binding, thereby facilitating GLI1 activation and contributing to both physiological and pathological crosstalk.
Hedgehog 和 MAPK 信号通路之间的串扰发生在几种类型的癌症中，并导致对 Hedgehog 通路抑制剂的临床耐药。在这里，我们表明 MAP 激酶介导的磷酸化会削弱 GLI1 转录因子与其负调节剂 SUFU 的结合。ERK2 在三个进化上保守的靶位（位于与 SUFU 高亲和力结合位点附近的 S102、S116 和 S130）上磷酸化 GLI1；这些磷酸化协同作用使 GLI1-SUFU 结合的亲和力降低超过 25 倍。磷酸化任何一个或甚至两个三个位点都不会导致当所有三个位点都被磷酸化时看到的 SUFU 释放水平。边界为 S102 的 R100 和 S105 残基的肿瘤衍生突变也会降低 SUFU 结合，共同定义了一个新的进化上保守的 SUFU 亲和力调节区。在培养的哺乳动物细胞中，含有 S102、S116 和 S130 磷酸模拟取代的 GLI1 变体显示出增强的驱动转录的能力。我们得出结论，ERK2 或其他 MAP 激酶对 GLI1 的多位点磷酸化削弱了 GLI1-SUFU 的结合，从而促进了 GLI1 的激活，并导致生理和病理串扰。
