Studying the ERK phosphorylation of the BCAT protein

人支链氨基转移酶的胞质和线粒体亚型（hBCATc和hBCATm， 分别）催化支链氨基酸（BCAA）转氨成它们各自的α-酮基 酸和谷氨酸。此外，我们最近发现hBCAT被典型的有丝分裂原磷酸化， 活化蛋白激酶（MAPK）家族成员，细胞外调节激酶1/2（ERK 1/2）。我们的研究 研究小组已经展示了ERK 1/2蛋白在体外和乳腺癌细胞中与hBCATc相互作用的直接证据。 更具体地说，我们在乳腺癌细胞中发现了BCAT 1（编码hBCATc的基因）的过表达， 导致ERK 1/2活化/磷酸化水平降低，我们的体外实验表明， 活化/磷酸化的ERK 1/2磷酸化hBCAT c，受hBCAT的氧化还原中心调节。在一起， 这些观察结果的生理学意义对于更好地理解细胞和 hBCATc如何与ERK 1/2相互作用的分子机制。在这个建议中，我们将重点放在蛋白质- ERK 1/2介导的hBCATc磷酸化的蛋白质相互作用。根据初步研究，我们 假设氧化还原中心通过ERK 1/2调节hBCATc的磷酸化， 蛋白质在细胞中发挥额外的功能作用，hBCAT的氧化还原中心在细胞中发挥重要作用。 hBCAT和ERK 1/2之间的蛋白质-蛋白质相互作用。我们假设hBCAT与 被各种激酶磷酸化，这导致hBCAT的构象变化，可能赋予 具有新功能的p-hBCAT。在拟议的项目中，我们将研究磷酸化的调节作用， hBCAT通过ERK 1/2使用互补的生物化学和生物物理策略，包括动力学分析， 质谱和X射线晶体学。同样，ERK 1/2的氧化还原调节也是一个有待研究的主题。 在这个项目中开发的。总之，这些实验预计将提供一个全面的基础， 理解ERK 1/2对BCAT的氧化还原调节磷酸化的机制， 磷酸化对hBCAT的影响。此外，这些研究将建立一个工作流程，以检查各种 hBCAT-激酶相互作用，帮助我们进一步研究磷酸化介导的构象变化， 这将有助于我们更好地了解细胞内的功能性后果 hBCAT的磷酸化。该项目将首次提供对分子生物学的独特见解， hBCAT-ERK 1/2相互作用的氧化还原调节机制，这将从根本上告知其 在乳腺癌和阿尔茨海默病等疾病中的作用。

The cytosolic and mitochondrial isoforms of human branched chain aminotransferase (hBCATc and hBCATm, respectively) catalyze the transamination of the branched chain amino acids (BCAA) to their respective α-keto acids and glutamate. In addition, we recently found that hBCAT is phosphorylated by the canonical mitogen- activated protein kinase (MAPK) family member, extracellular regulated kinase 1/2 (ERK1/2). Our research team has shown direct evidence that ERK1/2 protein interacts with hBCATc in vitro and in breast cancer cells. More specifically, we found in breast cancer cells the overexpression of BCAT1 (gene encoding hBCATc) resulted in decreased levels of ERK1/2 activation/phosphorylation, and our in vitro experiments showed activated/phosphorylated ERK1/2 phosphorylates hBCATc regulated by the redox center of hBCAT. Together, the physiological implications of these observations are considerable to better understand the cellular and molecular mechanisms of how hBCATc interacts with ERK1/2. In this proposal we will focus on the protein- protein interaction of ERK1/2-mediated phosphorylation of the hBCATc. Based on preliminary studies, we hypothesize that the redox center regulated phosphorylation of hBCATc by ERK1/2 signals this metabolic protein to play additional functional roles in the cell, with the redox center of hBCAT playing an important role in protein-protein interactions between hBCAT and ERK1/2. We hypothesize that hBCAT is differentially phosphorylated by various kinases, which causes a conformational change of hBCAT that potentially confers p-hBCAT with new functions. In the proposed project, we will study the regulatory effects of phosphorylation of hBCAT by ERK1/2 using complementary biochemical and biophysical strategies, including kinetics analysis, mass spectrometry and X-ray crystallography. Likewise, redox regulation of ERK1/2 is also a theme to be developed in this project. Together, these experiments are expected to provide a comprehensive basis for understanding the mechanism of the redox-regulated phosphorylation of BCAT by ERK1/2, and the structural effects of phosphorylation on hBCAT. Moreover, these studies will establish a workflow to examine various hBCAT-kinase interactions and help us further study the phosphorylation-mediated conformational changes of hBCAT by other kinases that will help us to better understand the functional consequences of intracellular phosphorylation of hBCAT. This project will provide for the first-time unique insights into the molecular mechanisms underlying the redox regulation of hBCAT-ERK1/2 interactions, which will fundamentally inform its role in disease conditions such as breast cancer and Alzheimer’s disease.