P-TEFb激酶复合体在常染色体显性多囊肾病发生发展中的作用及其机制研究

Autosomal dominant polycystic kidney disease(ADPKD) is the most common monogenic kidney disease. The molecular mechanisms responsible for the development of ADPKD are not well understood and no curative treatment is available. Dysregulation of renal tubular epithelial cell proliferation and differentiation is the major cause of cystogenesis. P-TEFb kinase complex acts as a master regulator of the balance of cell proliferation and differentiation, and plays key roles in determining the cell fate. Our preliminary data showed that the subunits of P-TEFb are overexpressed and the kinase activity of P-TEFb is increased in cyst-lining epithelial cells in Pkd1-/- mouse kidneys. Inhibition of P-TEFb kinase activity greatly retards disease progression and improves renal function in PKD mouse model. cAMP-regulated mechanisms are fundamental to cyst formation and disease progression. We found that cAMP promotes the interaction between CREB and P-TEFb. We also found that P-TEFb dose-dependently enhances CREB transcriptional activity. Collectively, these data suggest that P-TEFb may play roles in ADPKD. The future work will focus on investigating the following key issues: the molecular mechanisms underlying the regulation of CREB transactivation by P-TEFb; the regulation of phosphorylation and kinase activity of P-TEFb by PKA; the therapeutic treatment targeting P-TEFb and CREB in ADPKD. These studies may help us understand the crosstalk between P-TEFb and cAMP signaling pathway, elucidate the roles of P-TEFb and cAMP pathway in the progression of ADPKD, allow us to design more effective therapeutic strategies for ADPKD treatment.

常染色体显性多囊肾病是发病率最高的遗传性肾病，发病机制仍不清楚，尚无有效治疗方法。细胞增殖和分化功能的异常是疾病发生发展的决定因素。P-TEFb激酶是调控细胞增殖和分化、决定细胞命运的关键蛋白复合体。我们发现P-TEFb在多囊肾病的小鼠模型中高表达、酶活性增加，抑制其激酶活性显著减缓囊肿形成并改善肾功能。cAMP通路的异常活化在多囊肾病的进展中起着核心作用，但具体的分子机制仍有待阐明。我们发现P-TEFb可以和cAMP下游核心转录因子CREB相互作用并增强CREB转录活性。拟进行的工作将研究P-TEFb调控CREB转录活性的分子机制；cAMP信号对P-TEFb蛋白复合体的组装及其激酶活性的影响；药物靶向P-TEFb和CREB对疾病进程的影响。此研究将有助于我们更好地理解P-TEFb和cAMP信号通路间的相互作用，二者在多囊肾病发生发展中的作用和机制，从而为发现新的药物作用靶点提供理论基础。

常染色体显性多囊肾病（ADPKD）是最常见的遗传性肾脏疾病，在疾病进展过程中，多条信号通路发生异常，其中起主导作用的是cAMP信号通路的异常活化，但cAMP异常活化后导致疾病进展的具体机制仍有待阐明。cAMP信号活化后激活PKA，活化的PKA通过磷酸化下游靶分子从而实现细胞对cAMP信号的响应。我们的研究发现，PKA可以磷酸化HEXIM1蛋白第158位的丝氨酸（S158）。HEXIM1与7SK snRNP组成HEXIM1-7SK snRNP复合体，其主要的作用是与正性转录延伸因子P-TEFb结合，进而抑制P-TEFb的活性。由于cAMP-PKA通路的异常活化，HEXIM1的S158位点磷酸化和P-TEFb激酶活性在ADPKD小鼠模型和患者组织中显著升高。联合RNA-seq和ChIP-seq分析，我们发现活化的P-TEFb通过促进转录延伸，上调囊肿发生相关基因表达，加速疾病进展；抑制P-TEFb激酶可以显著延缓ADPKD疾病进程。以上工作是本基金所解决的核心科学问题，这一工作解析了在ADPKD疾病发生发展中P-TEFb与cAMP信号通路的交互作用，有助于更好地理解P-TEFb激酶复合体如何响应外界信号，进而活化并促进转录延伸、调控基因表达的分子机制，相关论文本项目负责人以主要通讯作者身份发表于Science Advances杂志。除此之外，本基金还支持了多项相关研究，相关论文本项目负责人均以独立通讯或者主要通讯作者身份发表于Science Translational Medicine（封面文章）（基金第一标注），Nature Metabolism（基金第二标注），Journal of the American Society of Nephrology（基金第一标注），Nucleic Acids Research（基金第四标注）等高影响力杂志上。

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