Physiology/cell biology of pancreatic acinar mitochondrial vitamin B1 uptake

胰腺腺泡线粒体维生素 B1 摄取的生理学/细胞生物学

• 批准号: 9004590
• 负责人: HAMID M SAID
• 金额: $ 39.08万
• 依托单位: SOUTHERN CALIFORNIA INST FOR RES/EDUC
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-01 至 2019-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9004590
• 关键词: Acinar Cell; Acute; Address; Affect; Alcohols; Amino Acids; Bioinformatics; Blood Circulation; Cell membrane; Cell physiology; Cells; Cellular biology; Chronic; Clinical; Cytoplasm; Endocrine; Energy Metabolism; Event; Exocrine pancreas; Exposure to; Failure; Funding; Genes; Genetic Transcription; Goals; Health; Human; Impairment; Investigation; Knockout Mice; Lead; Light; Maintenance; Mediating; Mitochondria; Molecular; Mutation; Nucleic Acid Regulatory Sequences; Organ; Organelles; Oxidation-Reduction; Oxidative Stress; Pancreas; Physiology; Play; Process; Production; Proteins; Regulation; Regulatory Element; Regulatory Pathway; Research; Role; Signal Transduction; Structure; Structure-Activity Relationship; System; Testing; Thiamine; Thiamine Deficiency; Thiamine Pyrophosphate; Time; Transgenic Mice; Up-Regulation; Vitamins; Work; alcohol exposure; base; cell type; cigarette smoking; feeding; information processing; mouse model; novel; programs; promoter; trafficking; uptake

DESCRIPTION (provided by applicant): Vitamin B1 (thiamin) is indispensable for normal function/health of pancreatic cells due to its critical role in oxidative energy metabolism, ATP production, and in maintaining normal cellular redox state. Low intracellular level of thiamin leads to acute energy failure and oxidative stress; it is also known to lead to impairment in the function of mitochondria. At the organ level, the pancreas contains high levels of thiamin, and deficiency of this vitamin leads to impairment in its functions. The pancreas cannot synthesis thiamin endogenously, and thus, must obtain the vitamin from circulation. The overall goal of this research program has been focused on developing a comprehensive understanding of the molecular mechanisms involved in thiamin entry into pancreatic acinar cells and the subsequent transport (compartmentalization) of its major metabolite thiamin pyrophosphate (TPP; which represent ~ 85-90% of total cellular thiamin and which is generated exclusively in the cytoplasm) into mitochondria (an organelle that contains and utilizes ~ 90% of cellular thiamin), how these process are regulated, and how they are affected by exposure to common external factors that are known to adversely affect normal pancreatic physiology/health. Studies during the previous funding period have focused exclusively on thiamin transport into pancreatic cells across cell membrane. Our focus in the current proposal is on transport of TPP into mitochondria of pancreatic acinar cells with special emphasis on how the process is being regulated at the transcriptional and post-transcriptional levels, how the involved mitochondrial TPP transporter (MTPPT; product of the SLC25A19 gene) is targeted to mitochondria, and which structural features of MTPPT are important for its function. We also aim at investigating the effect of chronic exposure to alcohol and to specific components of cigarette smoke (CS) (external factors known to adversely affect pancreatic health) on the uptake process. Thus, in new preliminary studies, we have cloned the 5'-regulatory region of the SLC25A19 gene, determined the minimal promoter needed for basal activity, and identified a number of putative cis- regulatory elements that may be needed for its activity. We also obtained evidence to show that the pancreatic acinar mitochondrial TPP uptake process is up-regulated in thiamin deficiency via transcriptional mechanism(s), that the process is also under possible regulation by specific intracellular regulatory pathway(s). Furthermore, information was obtained on how MTPPT is targeted to mitochondria. Moreover evidence were obtained to show that chronic exposure of pancreatic acinar cells to alcohol and to specific components of CS leads to a significant inhibition in pancreatic acinar mitochondrial TPP uptake process, and that the effect is mediated at the level of SLC25A19 transcription. Based on these preliminary findings, our working hypothesis in this proposal is that the pancreatic acinar mitochondrial TPP uptake process is a regulated event, that this regulation occurs at both transcriptional and post-transcriptional levels, that unique sequence(s) dictated targeting of MTPPT to mitochondria, and that chronic exposure of pancreatic acinar cells to alcohol and to specific components of CS impairs TPP uptake. Three specific aims are proposed to test this hypothesis. Results of these investigations are expected to provide valuable information regarding physiology/cell biology of an important pancreatic acinar mitochondrial uptake process, information that may also be applicable to other mitochondrial uptake systems. Furthermore, the results are of pathophysiological relevance as they may shed light onto the consequences of exposure of pancreatic acinar cells to common external factors that adversely affect pancreatic health, on mitochondrial physiology.

说明(申请人提供)：维生素B1(硫胺素)对胰腺细胞的正常功能/健康是不可或缺的，因为它在氧化能量代谢、ATP产生和维持正常细胞氧化还原状态方面起着关键作用。细胞内硫胺素水平低会导致急性能量衰竭和氧化应激；它还会导致线粒体功能受损。在器官水平上，胰腺含有高水平的硫胺素，这种维生素的缺乏会导致其功能受损。胰腺不能内源性合成硫胺素，因此，必须从循环中获取维生素。这项研究计划的总体目标是全面了解硫胺素进入胰腺腺泡细胞及其主要代谢物硫胺素焦磷酸(TPP；占细胞总硫胺素的85-90%，仅在细胞质中产生)到线粒体(一种含有和利用~90%细胞硫胺素的细胞器)的分子机制，这些过程是如何调节的，以及暴露于已知对正常胰腺生理/健康不利的常见外部因素如何影响这些过程。在之前的资助期间，研究主要集中在硫胺素跨细胞膜进入胰腺细胞的转运。在目前的方案中，我们的重点是TPP到胰腺腺泡细胞线粒体的转运，特别强调这个过程是如何在转录和转录后水平上被调控的，涉及的线粒体TPP转运体(MTPPT；SLC25A19基因的产物)是如何靶向线粒体的，以及MTPPT的哪些结构特征对其功能是重要的。我们还旨在调查长期接触酒精和香烟烟雾(CS)的特定成分(已知对胰腺健康产生不利影响的外部因素)对摄取过程的影响。因此，在新的初步研究中，我们克隆了SLC25A19基因的5‘-调节区，确定了基本活性所需的最小启动子，并确定了其活性可能需要的一些假定的顺式调节元件。我们还获得了证据表明，硫胺素缺乏症患者胰腺腺泡线粒体TPP摄取过程通过转录机制上调(S)，该过程也可能受到特定细胞内调节途径的调节(S)。此外，还获得了关于MTPPT如何靶向线粒体的信息。此外，有证据表明，胰腺腺泡细胞长期接触酒精和CS的特定成分会导致胰腺腺泡线粒体TPP摄取过程受到显著抑制，这种作用是在SLC25A19转录水平上介导的。基于这些初步发现，我们的工作假设是，胰腺腺泡线粒体TPP摄取过程是一个受调控的事件，这种调节发生在转录和转录后水平，独特的序列(S)决定了MTPPT靶向线粒体，胰腺腺泡细胞长期暴露于酒精和CS的特定成分会损害TPP摄取。为了检验这一假说，本文提出了三个具体目标。这些研究结果有望为重要的胰腺腺泡线粒体摄取过程的生理学/细胞生物学提供有价值的信息，这些信息也可能适用于其他线粒体摄取系统。此外，这些结果具有病理生理学意义，因为它们可能揭示胰腺腺泡细胞暴露于对胰腺健康产生不利影响的常见外部因素对线粒体生理学的影响。