CK2-dependent phosphorylation of Progesterone Receptors mediates proliferative si

说明(申请人提供)：黄体酮是一种卵巢类固醇激素，对乳房发育至关重要。孕激素受体(PR)主要以两种共表达的形式存在，即PR-A和PR-B。来自基因敲除小鼠的研究表明，PR-B在乳腺腺泡形成过程中是增殖信号所必需的。相比之下，PR-A是子宫发育所必需的，而孕酮可以抑制细胞增殖。关于PR组织和异构体特异性转录的调控，人们知之甚少。异构体特异性有丝分裂(乳腺中的PR-B)和抑制/分化(子宫中的PR-A)是如何产生的 取得了什么成效？PR-A和PR-B通常在同一组织中共表达，仅表达一种PR亚型的细胞很少，除非在乳腺癌中正常的1：1比例经常改变。选择性PR异构体抑制(阻断促增殖作用 PR-B在保留PR-A的保护或抗增殖作用的同时，将代表着乳腺癌预防和/或治疗方面的重大进展。公关是高度翻译后修饰的。磷酸化，主要是在PR-B N-末端丝氨酸残基上，显著改变受体的稳定性、定位、转录活性和启动子选择性。我们的初步数据表明，在乳腺癌细胞中PR-B特异性增殖作用的基础是依赖于CK2的PR-B Ser81的选择性磷酸化，通过一个独特的蛋白质相互作用结构域，公共对接(CD)结构域，该结构域仅在PR-B中发现，而在PR-A中不存在。PR-B Ser81的磷酸化调节一组高度特异的增殖和促生存基因，包括已知的调节乳腺干细胞隔间的特定PR调节基因，如WNT1和STAT5A。此外，我们的数据表明，STAT5A可能是一个“先锋因子”，一个早期的基因组结合伙伴，招募/指导磷酸-Ser81-PR-B特异的基因调控。这项研究计划的目标是确定通过CD结构域与PR-B相互作用的蛋白质如何调节Ser81上PR-B的直接磷酸化，从而在对乳腺癌细胞增殖、促进生存和干细胞舱扩张重要的基因上调控PR-B异构体特异的转录事件。 假设：PR和STAT5共同调节特定的一组磷酸化-PR-B靶基因(通过CD结构域依赖的MKP3和CK2的招募，随后是CK2介导的PR-B Ser81的磷酸化)，调控乳腺癌细胞的增殖和促进生存，部分是通过调节乳腺干细胞室；选定的基因在缺乏配体的情况下由磷酸化-PR-B调节。依赖于CK2的PR-B的激活可能加速乳腺癌的发展和/或推动早期乳腺癌的进展。

DESCRIPTION (provided by applicant): Progesterone is an ovarian steroid hormone essential for breast development. The progesterone receptor (PR) exists primarily in two co-expressed isoforms, PR-A and PR-B. Studies from knockout-mice have shown that PR-B is required for proliferative signaling during mammary gland alveologenesis. In contrast, PR-A is required for uterine development, where progesterone inhibits proliferation. Very little is understood regarding regulation of PR tissue- and isoform-specific transcription. How are isoform-specific mitogenic (PR-B in the breast) and inhibitory/differentiative (PR-A in the uterus) effects achieved? PR-A and PR-B are most often co-expressed in the same tissues, and cells that express only a single PR isoform are rare, except in breast cancer where the normal 1:1 ratio is frequently altered. Selective PR isoform inhibition (blocking pro-proliferative effects of PR-B while preserving the protective or anti-proliferative effects of PR-A) would represent significant progress in breast cancer prevention and/or treatment. PR is highly post-translationally modified. Phosphorylation, primarily on PR-B N-terminal serine residues, significantly alters receptor stability, localization, transcriptional activity and promoter selectvity. Our preliminary data suggest that the basis for PR-B-specific proliferative actions in breast cancer cells involves ck2-dependent selective phosphorylation of PR-B Ser81 via a unique protein interaction domain, the common docking (CD) domain, found exclusively in PR-B but not PR-A. Phosphorylation of PR-B Ser81 regulates a highly specific subset of proliferative and pro-survival genes, including selected PR-regulated genes known to modulate the mammary stem cell compartment, such as Wnt1 and STAT5A. Additionally, our data suggest that STAT5A may serve as a "pioneer factor", an early genomic binding partner that recruits/directs phospho-Ser81-PR-B-specific gene regulation. The goal of this research proposal is to determine how proteins that interact with PR-B via the CD domain regulate direct phosphorylation of PR-B on Ser81, thereby dictating PR-B isoform-specific transcriptional events at genes important for breast cancer cell proliferation, pro-survival, and expansion of the stem cell compartment. Hypothesis: PR and STAT5 co-regulate a specific subset of phospho-PR-B target genes (through CD domain- dependent recruitment of MKP3 and ck2, followed by ck2-mediated phosphorylation of PR-B Ser81) that regulate breast cancer cell proliferation and pro-survival, in part via modulation of the mammary stem cell compartment; selected genes are regulated by phospho-PR-B in the absence of ligand. ck2-dependent activation of PR-B may accelerate mammary tumor development and/or drive early breast cancer progression.