Translational Control by elF2 Kinase during ER Stress

描述(申请人提供)：细胞应激，如错误折叠的蛋白质在内质网中堆积(内质网应激)，营养缺乏，紫外线照射和氧化损伤，诱导旨在减轻细胞损伤的基因表达程序。应激基因表达的一个重要因素是磷酸化真核细胞起始因子-2(EIF2)的蛋白激酶家族。EIF2的磷酸化降低了该翻译因子的活性，导致了对一般蛋白质合成的调节，并诱导了对应激修复至关重要的mRNAs的翻译。这项建议的重点是eIF2激酶，PEK(PERK，EIF2AK3)，它在响应内质网应激时被激活。EIF2的PEK磷酸化通过激活多个转录因子，包括ATF4和NF-KB，直接表达参与应激修复或凋亡的基因，从而提高细胞在内质网应激中的生存能力。异常的内质网应激反应与一系列人类疾病有关，包括糖尿病、骨骼和肝脏疾病，以及循环和神经病理。这项建议阐述了调控内质网应激相关基因表达的机制及其在疾病中的作用。我们提出了四个具体目标。目的1研究内质网应激下PEK对基因特异性翻译的调控作用。我们将确定翻译重新启动或替代翻译机制对PEK反应途径中调节蛋白的合成是否重要。目的2研究eIF2磷酸化在调节核因子-KB活性中的作用。我们将描述PEK在内质网应激过程中激活NF-KB的分子机制，并将其与替代的NF-KB调控过程进行比较。目的3确定eIF2磷酸化在抗癌药物细胞保护中的作用。为此，我们将探索eIF2激酶和P53应激途径之间的联系，并确定eIF2磷酸化是否与抗癌药物耐药有关。目的4.确定在人类群体中发现的PEK突变的功能后果。我们将利用哺乳动物培养的细胞来表征来自WRS患者的PEK错义变化或多态的功能后果。总之，解决这些目标将增加我们对细胞适应环境压力的过程及其在人类疾病中的影响的理解。

DESCRIPTION (provided by applicant): Cellular stresses such as accumulation of misfolded protein in the endoplasmic reticulum (ER stress), nutrient deprivation, UV irradiation, and oxidative damage induce a program of gene expression designed to alleviate cellular injury. An important contributor to stress gene expression is a family of protein kinases that phosphorylate eukaryotic initiation factor -2 (eIF2). Phosphorylation of eIF2 reduces the activity of this translation factor, leading to regulation of general protein synthesis and induced translation of mRNAs important for stress remediation. This proposal focuses on the eIF2 kinase, PEK (PERK, EIF2AK3), that is activated in response ER stress. PEK phosphorylation of eIF2 enhances cell viability in response to ER stress via activation of multiple transcription factors, including ATF4 and NF-KB, that direct expression of genes involved in stress remediation or apoptosis. An aberrant ER stress response is associated with a range of human diseases, including diabetes, bone and liver disorders, and circulatory and neurological pathologies. This proposal addresses the mechanisms regulating the program of stress-related gene expression in response to ER stress, and its role in disease. We propose four specific aims. Aim 1 Characterize PEK control of gene-specific translation in response to ER stress. We will determine whether translation reinitiation or alternative translation mechanisms are important for synthesis of regulatory proteins in the PEK response pathway. Aim 2 Characterize the role of eIF2 phosphorylation in the regulation of NF-KB activity. We will characterize the molecular mechanisms by which PEK activates NF-KB during ER stress and compare it to alternative NF-KB regulatory processes. Aim 3 Determine the role of eIF2 phosphorylation in cytoprotection against anti-cancer drugs. In this aim, we will explore the link between the eIF2 kinase and p53 stress pathways, and determine whether eIF2 phosphorylation contributes to resistance to anti-cancer drugs. Aim 4. Determine the functional consequences of PEK mutations identified in the human population. We will characterize the functional consequence of PEK missense changes derived from WRS patients or polymorphisms using mammalian cultured cells. Together, addressing these aims will increase our understanding of the process of cellular adaptation to environmental stresses and its impact in human disease.