Regulation and Role of CREB in Cellular Genotoxic Response to Xenobiotics

描述（由申请人提供）：CREB （cAMP-response element binding）转录因子是一种刺激诱导的磷酸化蛋白，参与许多细胞信号通路。CREB和CREB相互作用蛋白的功能障碍和失调导致人类疾病，如癌症和神经变性。CREB似乎在各种组织的细胞防御和存活中起关键作用；然而，CREB参与细胞存活的机制以及CREB功能失调导致这些人类疾病的原因尚不完全清楚。CREB Ser-133位点的磷酸化是主要的翻译后修饰，可增强CREB对受体偶联刺激的活性。然而，CREB Ser-133磷酸化的状态并不总是与CREB转录功能相关，这表明CREB Ser-133磷酸化的另一个事件似乎以刺激特异性的方式参与CREB调控。本研究项目可能为这些未解决的问题提供证据和关键答案，因为我们最近发现HIPK2（同源域相互作用蛋白激酶2），一种基因毒性应激反应激酶，通过磷酸化一个新的丝氨酸位点（Ser-271）而不是Ser-133来激活CREB，从而激活CREB的转录功能。我们将验证我们的假设，即HIPK2是CREB转录因子的新调节剂，通过磷酸化这个新的CREB位点，诱导基因毒性和氧化应激条件下的细胞存活程序。在体外和体内模型中，我们将重点研究HIPK2磷酸化CREB激活其转录功能的分子机制以及下游事件，包括靶基因的表达和细胞对遗传毒性应激的易感性。这项研究的科学影响将是广泛而重要的，因为CREB调节基本的细胞事件，如细胞生长、分化、代谢和免疫反应。因此，成功完成这一提案所揭示的新的CREB调控将增强我们对与CREB活动密切相关的各种生理和疾病条件的理解。

DESCRIPTION (provided by applicant): The CREB (cAMP-response element binding) transcription factor is a stimulus-induced phospho-protein that is involved in numerous cell signaling pathways. Dysfunction and deregulation of CREB and CREB- interacting proteins cause human diseases such as cancer and neurodegeneration. CREB appears to play a key role in cell defense and survival in various tissues; however, the mechanisms through which CREB is involved in cell survival and the reason why deregulation of CREB function causes these human diseases remain incompletely understood. CREB phosphorylation at Ser-133 is the major posttranslational modification that enhances CREB activity in response to receptor-coupled stimuli. However, the status of CREB Ser-133 phosphorylation was not always correlated with CREB transcription function, suggesting that another event along with CREB Ser-133 phosphorylation seems to be involved in CREB regulation in a stimulus-specific manner. This research project may provide evidence and a critical answer to these unsolved problems because we recently found that HIPK2 (homeodomain interacting protein kinase 2), a genotoxic stress responsive kinase, activates CREB via phosphorylation of a new serine site (Ser-271) but not Ser-133, resulting in activation of CREB transcription function. We will test our hypothesis that HIPK2 is a new regulator of the CREB transcription factor via phosphorylation of this new CREB site that induces a cell survival program in genotoxic and oxidative stress conditions. The proposed experiments will focus on characterization of molecular mechanism through which CREB phosphorylation by HIPK2 activates its transcription function as well as downstream events including expression of target genes and cellular susceptibility to genotoxic stress in in vitro and in vivo models. The scientific impact of this research will be broad and significant because CREB regulates essential cellular events such as cell growth, differentiation, metabolism, and immune response. Therefore the unveiled new CREB regulation from successful completion of this proposal will enhance our understanding in various physiological and disease conditions closely associated with the CREB activity. PUBLIC HEALTH RELEVANCE: Genotoxic and oxidative stress induced by environmental and manmade chemicals are associated with human disease including cancer and neurodegeneration (such as Alzheimer and Parkinson's diseases), and aging; therefore, research to determine cellular defense mechanisms against the harmful stress is important for our understanding of the pathogenesis, prevention, and/or delay of these diseases. CREB is an essential transcription factor that plays critical roles in cell metabolism, differentiation, survival, and proliferation in various cell types. Indeed, accumulating evidence indicates that dysfunction and deregulation of CREB cause cancer and neuronal cell damage. CREB is involved in cell survival in genotoxic stress conditions; however, in contrast to intensive characterization of CREB in external stimuli that exert long-term effects such as cell differentiation and proliferation, molecular mechanisms behind CREB regulation in detrimental genotoxic and oxidative stress conditions remain largely unknown. This proposal will characterize a novel CREB regulatory pathway and mechanism we recently found, which are different from of a previously known CREB pathway. We anticipate that successful completion of proposed experiments will improve our understanding of how cells elicit CREB-regulated cell survival program against these stress and disease conditions. The impact of this research will be broad and significant in many research areas because the CREB transcription factor regulates numerous cellular functions in various types of tissues. Innovation of this research will include demonstration of a novel CREB signaling pathway and downstream target genes involved in stress response in cellular levels and an animal model.