脯氨酸羟化酶3调控c-Jun的作用与机制研究

The prolyl hydroxylase 3 (PHD3) hydroxylates the proline residue of hypoxia-inducible factor alpha (HIFα) in the presence of oxygen, leading to HIFα ubiquitination and proteasomal degradation. Besides HIFa, PHD3 has other substrates. Recent studies have shown that PHD3 are involved in cancers. However, the exact role of PHD3 and the molecular mechanism underlain remain largely unknown. C-Jun is an important component of transcription factor AP-1 that plays a critical role in cell proliferation. We found previously that the expression of PHD3 was downregulated in human colon cancer, which was associated with tumor grades, suggesting that PHD3 is a potential suppressor of colon cancer. Recently, we found that PHD3 binds c-Jun and inhibits c-Jun phosphorylation. PHD3 suppresses AP-1 activity and colon cancer cell proliferation. We hypothesize that PHD3 may regulate colon cancer cell proliferation through c-Jun. In this project we will further investigate the role and mechanism of PHD3 in regulating c-Jun phosphorylation. Our aim is to understand the function of PHD3 in the development of colon cancer, to uncover the molecular mechanism underlain, and to find valuable targets that might be used for colon cancer therapy in the future.

脯氨酸羟化酶3(PHD3)可以羟基化低氧诱导因子alpha(HIFa)，导致HIFa降解。除HIFa外，PHD3还可以作用于其它蛋白，具有HIFa非依赖功的能。近来研究发现PHD3在肿瘤生长过程中发挥作用，但具体作用和机制还不清楚。c-Jun是转录因子AP-1中的重要部分，参与调节细胞生长等过程。前期，我们发现PHD3在结肠癌中低表达并与肿瘤的级别密切相关，提示PHD3可能是结肠癌的抑制因子。近来，我们发现PHD3结合c-Jun并降低其磷酸化水平，抑制了AP-1的转录活性和结肠癌细胞的生长。这些结果提示PHD3可能通过调控c-Jun在肿瘤细胞生长过程中发挥作用。本项目将深入研究PHD3调控c-Jun磷酸化的作用和分子机制，并利用肠上皮细胞PHD3特异敲除小鼠研究该基因的作用。这一工作将有助于深入了解PHD3在肿瘤中的作用及机制，为今后疾病的防治提供实验依据。

脯氨酸羟化酶3(PHD3)具有羟基化修饰低氧诱导因子alpha(HIFa)，导致HIFa降解的作用。除HIFa外，PHD3还可以靶向作用于其它蛋白，具有HIFa非依赖功的能。研究表明PHD3具有抑制肿瘤生长的作用，但具体作用和机制还不清楚。我们前期研究发现PHD3具有调控转录因子AP-1活性的作用。同时，我们发现PHD3可以结合AP-1中的关键蛋白c-Jun并降低c-Jun磷酸化水平，抑制了AP-1的转录活性和结肠癌细胞的生长。这些结果提示PHD3可能通过调控c-Jun在肿瘤细胞生长过程中发挥作用。本项目在基金的支持下，深入研究了PHD3调控c-Jun磷酸化的作用和分子机制，并利用肠上皮细胞PHD3特异敲除小鼠研究该基因的作用。研究工作取得以下发现：（1）PHD3抑制c-Jun磷酸化；（2）PHD3脯氨酸羟基化酶活力为调节c-Jun磷酸化所必需；（3）内源性PHD3与c-Jun相互作用研究；（4）PHD3羟基化修饰c-Jun的Proline244位点，导致c-Jun无法与其上游激酶JNK结合，其磷酸化因此受到抑制；（5）PHD3具有抑制肿瘤细胞生长的作用，肠上皮细胞PHD3敲除小鼠研究表明，PHD3缺失促进肠癌的发生。这些结果表明：PHD3是一肠癌抑制因子，可通过羟基化c-Jun抑制AP1活力发挥抑制肠癌细胞的作用。这一工作将有助于深入了解PHD3在肿瘤中的作用及机制，为今后疾病的防治提供实验依据。