Role of PIN1 in tissue renewal

我们的研究计划的长期目标是提供全面的调节机制，说明细胞增殖，分化和死亡的时间和空间协调需要保持组织稳态。***磷酸化是细胞中最常见的翻译后修饰。通过调节蛋白的表达、定位和活性，磷酸化在多种细胞过程如增殖、分化和死亡中起着核心作用。虽然激酶和磷酸酶在将环境信号转化为及时反应的过程中发挥了关键作用，但磷酸化后调节机制现在被认为发挥了同样重要的作用。在这方面，肽基脯氨酸顺式/反式异构酶（PPIase） PIN1是独一无二的，因为它是唯一识别磷酸化蛋白的PPIase。一些PIN1底物已经被确定，其作用范围包括调节蛋白质稳定性、磷酸化、相互作用、定位、酶和转录活性。因此，PIN1在磷酸化后调节机制中发挥着独特的作用。***肠上皮是研究组织更新动态的最佳模型。事实上，增殖细胞被限制在隐窝中，子细胞最终在G0/G1被阻止，同时在向隐窝顶部迁移的过程中开始分化程序。因此，分化的细胞大部分被划分为绒毛。这个组织系统是高度动态的，肠上皮每3-5天更新一次。***首次研究Pin1在快速自我更新肠道中的作用是一个独特的机会，可以为细胞如何协调增殖、分化和死亡以保持组织稳态提供新的工具细胞和分子线索（短期目标）。***提出两个具体目的：***1)通过多种模型分析PIN1缺失对肠上皮自我更新能力的影响。***2)首次采用定量蛋白质组学方法对PIN1相互作用伙伴和调节蛋白进行系统分析，鉴定PIN1相互作用伙伴和调节蛋白。总之，通过分析PIN1耗竭对组织内稳态的影响，剖析PIN1在特定细胞过程（增殖、分化、死亡）中的贡献，并揭示PIN1相关靶点，我们独特的研究计划将推进我们对磷酸化蛋白脯氨酸异构化在组织内稳态和再生中的贡献的认识。此外，通过利用不同的模型来概括导致功能组织的不同步骤，我们的结果可能反映出一个更动态、更完整和更相关的背景，这将有助于组织工程师优化组织再生条件。********

The long-term objective of our research program is to provide comprehensive regulatory mechanisms accounting for the temporal and spatial orchestration of cell proliferation, differentiation and death needed to preserve tissue homeostasis. ***Phosphorylation is the most common post-translational modifications in cells. By modulating protein expression, localization and activity, phosphorylation plays a central role in orchestrating diverse cellular processes such as proliferation, differentiation and death. Although kinases and phosphatases performed a key role in converting an environmental cue into a timely response, post-phosphorylation regulatory mechanisms are now believe to play an as important task. In this regard, the peptidyl-prolyl cis/trans isomerase (PPIase) PIN1 is unique given that it is the only PPIase that recognizes phosphorylated proteins. Some PIN1 substrates have been identified and the spectrum of effects ranged from regulation of protein stability, phosphorylation, interaction, localization, enzymatic and transcriptional activity. Hence, PIN1 represents a unique player in post-phosphorylation regulatory mechanisms. ***The intestinal epithelium is an optimal model to study the dynamic of tissue renewal. Indeed, proliferative cells are restricted to crypts with daughter cells eventually being arrested in G0/G1 while beginning a differentiation program during their migration towards the top of the crypts. Differentiated cells are therefore mostly compartmentalized to the villi. This organized system is highly dynamic and the intestinal epithelium is renewed every 3-5 days. ***Studying for the first time the role of Pin1 in the rapid self-renewing intestine is a unique opportunity to provide novel instrumental cellular and molecular cues as to how cells orchestrate proliferation, differentiation and death to preserve tissue homeostasis (short-term objective).***Two specific aims are proposed:***1) To analyze the impact of PIN1 loss on self-renewal capacity of the intestinal epithelium by using diverse models. ***2) To identify PIN1 interacting partners and regulated proteins by performing the first systematic analysis of PIN1 interacting partners and regulated proteins by quantitative proteomics.***Altogether, by analyzing the impact of PIN1 depletion on tissue homeostasis, dissecting PIN1 contribution in specific cellular processes (proliferation, differentiation, death) and exposing PIN1 relevant targets, our unique research program will advance our knowledge on the contribution of prolyl isomerization of phospho-proteins in tissue homeostasis and regeneration. Also, by exploiting diverse models that recapitulate the different steps leading to a functional tissue, our results may reflect a more dynamic, integrated and relevant context that will assist tissue engineers in optimizing tissue regeneration conditions.********