Function and Regulation of the Phosphorylation-Specific Prolyl lsomerase Pin 1

描述（申请人提供）：脯氨酸定向磷酸化（pSer/Thr-Pro）是细胞中的主要信号传导机制。虽然这些磷酸化事件已被提出来调节蛋白质的功能，诱导构象变化，很少知道的性质，意义和调节这种构象变化，直到最近。我们鉴定了一种独特的酶，Pin 1，异构化特定的pSer/Thr-Pro键在某些蛋白质提出了一种新的信号传导机制，Pin 1催化调节其底物的构象后磷酸化，以控制蛋白质的功能。最近的研究表明，这种Pin 1催化的构象变化可以对多种细胞过程中的许多关键蛋白产生深远的影响。重要的是，Pin 1失调有助于某些病理条件，特别是癌症和阿尔茨海默病。在乳腺癌中，我们已经证明Pin 1是一个E2 F靶基因，对于调节多个上游致癌信号通路和协调一些下游细胞周期事件（如中心体复制）至关重要。此外，Pin 1敲除可防止某些癌基因诱导乳腺癌，而Pin 1过表达可导致中心体扩增、非整倍体和乳腺癌。因此，Pin 1在肿瘤发生中起关键作用，是潜在的抗癌靶点。然而，主要的挑战包括是否以及如何控制Pin 1的功能，以及Pin 1在生长调节中的其他新功能。我们发表的和初步的结果表明，Pin 1受到多种翻译后修饰，包括抑制性磷酸化，乙酰化和甲基化，Pin 1可能被磷酸化的激酶，这是一个已知的肿瘤抑制。因此，目的1将确定Pin 1磷酸化和其他新的翻译后修饰在调节细胞增殖和转化过程中Pin 1功能的意义，并确定负责Pin 1修饰的酶。此外，我们的初步研究发现，Pin 1结合并增加Pin 2/TRF 1的周转，这也是在Pin 1的相同遗传筛选中鉴定的，并且对有丝分裂调控很重要。鉴于TRF 1是一种负调控端粒延长的端粒蛋白，目的2将阐明Pin 1在调节TRF 1在正常和癌细胞端粒维持和有丝分裂进程中的功能中的新作用和机制。这些研究将有助于理解磷酸化后调节在肿瘤发生中的作用，并可能具有新的治疗意义。用通俗的语言来说，我们已经发现了一种对癌症发展至关重要的新酶Pin 1，并将继续研究Pin 1在癌症发展过程中的功能和调控，并希望找到新的药物靶点。

DESCRIPTION (provided by applicant): Proline-directed phosphorylation (pSer/Thr-Pro) is a major signaling mechanism in the cell. Although these phosphorylation events had been long proposed to regulate protein function by inducing conformational changes, little was known about the nature, significance and regulation of such conformational changes until recently. Our identification of a unique enzyme, Pin1 that isomerizes specific pSer/Thr-Pro bonds in certain proteins suggested a new signaling mechanism, whereby Pin1 catalytically regulates the conformation of its substrates after phosphorylation to control protein function. Recent studies have shown that such Pin1- catalyzed conformational changes can have profound effects on many key proteins in diverse cellular processes. Importantly, Pin1 deregulation contributes to some pathological conditions, notably cancer and Alzheimer's disease. In breast cancer, we have shown that Pin1 is an E2F target gene that is critical for the regulation of multiple upstream oncogenic signal pathways, and for the coordination of some downstream cell cycle events such as centrosome duplication. Moreover, Pin1 knockout prevents certain oncogenes from inducing breast cancer, whereas Pin1 overexpression causes centrosome amplification, aneuploidy and breast cancer. Thus, Pin1 plays a critical role in oncogenesis and is a potential anticancer target. However, the major challenges include whether and how to control Pin1 function and what are other novel functions for Pin1 in growth regulation. Our published and preliminary results suggest that Pin1 is subject to multiple post- translational modifications, including inhibitory phosphorylation, acetylation and methylation, and that Pin1 might be phosphorylated by a kinase that is a known tumor suppressor. Therefore, Aim 1 will be to determine the significance of Pin1 phosphorylation and other novel post-translational modifications in regulating Pin1 function during cell proliferation and transformation, and to identify enzymes responsible for Pin1 modifications. Moreover, our preliminary studies uncovered that Pin1 bound to and increased turnover of Pin2/TRF1, which was also identified in the same genetic screen for Pin1 and is important for mitotic regulation. Given that TRF1 is a telomeric protein negatively regulating telomere elongation, Aim 2 will be to elucidate the novel role and mechanisms of Pin1 in regulating TRF1 function in telomere maintenance and mitotic progression in normal and cancer cells. These studies should help understand the role of post- phosphorylation regulation in oncogenesis and might have novel therapeutic implications. In lay language, we have identified a new enzyme called Pin1 critical for cancer development and will continue to investigate the function and regulation of Pin1 during cancer development and hope to identify new drug targets.