Regulation of Coenzyme A Levels by Pantothenate Kinase

描述(由申请人提供)：长期目标是确定控制细胞内辅酶A浓度的机制，并了解这一调节系统的生理意义。辅酶A是一种必需的酰基载体，由从维生素泛酸酯(PAN)开始的一系列普遍反应产生。PAN是一种丰富的维生素，在正常的生理环境下，其含量远远超过支持CoA生物合成所需的数量。对CoA水平的精细控制对于支持中间代谢的生理调节非常重要，不仅因为CoA及其硫酸酯是能量生成途径中的关键辅助因子，而且它们还通过变构控制关键代谢控制点的碳通量。很明显，PAK的细胞活性调节辅酶A的生物合成，有两种机制控制这一参数。首先，CoA及其硫代酯对Pank的反馈抑制在特定的Pank表达水平上建立了细胞CoA浓度的上限。第二，通过改变Pank基因的表达来调节稳态CoA水平。细胞内CoA水平随着激素、饮食和药物的变化而波动，在代谢紊乱中也是失调的。有多个Pank基因表现出组织特异性表达，人类PANK2基因突变导致遗传性神经病的发现突显了特定同工酶表达的重要性。我们假设CoA水平的变化是改变脂肪酸利用和储存之间平衡的先决条件，Pank同工酶的表达对于功能性过氧化物酶的增殖和脂肪酸氧化是必要的。CoA的生物合成一直是一个被忽视的研究领域，但我们最近对Pank基因、cDNA和蛋白质的鉴定和初步鉴定为分子解剖这些基因产物对控制哺乳动物中间代谢的重要性打开了大门。该研究计划围绕两个目标组织：1)确定Pank同工酶的特征并确定调节其活性的生化机制；2)确定导致Pank基因表达改变的机制以及控制CoA水平的代谢重要性。这项研究将通过明确特定的Pank同工酶调节CoA的重要性，有助于理解全球代谢控制和人类疾病。

DESCRIPTION (provided by applicant): The long-term goal is to define the mechanisms that control the intracellular concentration of CoA and understand the physiological significance of this regulatory system. CoA is an essential acyl group carrier, and is produced by a universal series of reactions starting from the vitamin pantothenate (Pan). Pan is an abundant vitamin and under normal physiological circumstances is present in significant excess over the amounts needed to support CoA biosynthesis. Fine control over CoA levels is important to support physiological adjustments in intermediary metabolism not only because CoA and its thioesters are key cofactors in energy generating pathways, but they also allosterically control carbon flux at key metabolic control points. It is clear that the cellular activity of Pan kinase (PanK) regulates CoA biosynthesis and there are two mechanisms that govern this parameter. First, feedback inhibition of PanK by CoA and its thioesters establishes the upper limit for the cellular CoA concentration at a specific level of PanK expression. Second, the steady state CoA level is adjusted by altering PanK gene expression. The intracellular CoA levels fluctuate in response to hormones, diet, and drugs, and are also dysregulated in metabolic disorders. There are multiple PanK genes that exhibit tissue specific expression, and the importance of specific isozyme expression is underscored by the finding that mutations in the human PANK2 gene are responsible for a hereditary neuropathy. We hypothesize that changes in CoA levels are a prerequisite for altering the balance between fatty acid utilization and storage, and that elevation of PanK isozyme expression is necessary for functional peroxisome proliferation and fatty acid oxidation. CoA biosynthesis has been a neglected research area, but our recent identification and preliminary characterization of the PanK genes, cDNAs and proteins open the door to the molecular dissection of the importance of these gene products to the control of mammalian intermediary metabolism. The Research Plan is organized around two aims: 1) To characterize the PanK isozymes and define the biochemical mechanisms that regulate their activity; and 2) To define the mechanisms that lead to altered PanK gene expression and the metabolic importance of controlling CoA levels. This research will contribute to the understanding of global metabolic control and human disease by defining the importance of CoA regulation by specific PanK isozymes.