The Guanosine-Adenosine Mechanism

鸟苷-腺苷机制

• 批准号: 8669136
• 负责人: EDWIN Kerry JACKSON
• 金额: $ 37.73万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8669136
• 关键词: Adenosine; Biological; Biological Models; Blood Vessels; Blushing; Brain; Cell Surface Receptors; Cell physiology; Cells; Cellular Stress; Cyclic AMP; Cyclic GMP; Data; Enzymes; Evolution; Guanine; Guanosine; Heart; High Pressure Liquid Chromatography; Immune system; Injury; Kidney Diseases; Lung; Measures; Mediating; Metabolism; Physiological; Physiological Processes; Play; Purines; Role; Smooth Muscle Myocytes; Stress; Testing; Tissues; Vasodilation; analog; cell type; extracellular; in vivo; kidney cell; liquid chromatography mass spectrometry; purine; receptor; research study; response; response to injury; uptake

DESCRIPTION (provided by applicant): Adenosine and guanosine are naturally-occurring and structurally similar purines. Moreover, naturally- occurring cyclic analogues of adenosine and guanosine are involved in similar physiological processes (e.g., both cAMP and cGMP mediate vasodilation). Strangely, at first blush it would seem that evolution broke the symmetry between adenosine and guanosine by bestowing cells with adenosine, but not guanosine, receptors. Thus the standard view is that adenosine serves as a physiological regulator of cellular function via activation of its own cell-surface receptors, while guanosine is merely an idle bystander. The purpose of this application is to challenge this received view by proposing that guanosine also plays an important role in cellular physiology, not via its own receptors but rather by engaging a powerful collaborative mechanism involving adenosine. In this regard, we hypothesize that extracellular guanosine is THE major physiological determinant of extracellular levels of adenosine because guanosine blocks the disposition of adenosine from the extracellular compartment allowing greater activation of adenosine cell-surface receptors due to increased extracellular adenosine levels. We refer to this guanosine-adenosine interaction as the GUANOSINE- ADENOSINE MECHANISM. Our pilot experiments strongly suggest that our hypothesis is correct. In preglomerular vascular smooth muscle cells (a model system for microvascular smooth muscle cells) we observe that for any given amount of adenosine added to cells, the extracellular concentrations of adenosine [as measured by high performance liquid chromatography-mass spectrometry (LC-MS/MS)] are more than 10- fold higher when guanosine is also added to the cells. We also find that cellular stress/injury increases extracellular levels of BOTH guanosine and adenosine. Moreover, we find that guanosine PROFOUNDLY augments the biological effects of adenosine in vivo! These findings suggest that extracellular guanosine, by blocking the disposition of extracellular adenosine, is the most important physiological determinant of extracellular levels of adenosine yet discovered. We propose to test the existence of, the mechanism of and the importance of the Guanosine-Adenosine Mechanism with the following six Specific Aims: Aim 1 - To determine the existence of the Guanosine-Adenosine Mechanism in vascular and renal cell types; Aim 2 - To determine whether the Guanosine-Adenosine Mechanism is mediated directly by guanosine or indirectly by conversion of guanosine to guanine; Aim 3 - To determine whether the Guanosine-Adenosine Mechanism involves inhibition by guanosine of enzymes involved in adenosine metabolism; Aim 4 - To determine whether the Guanosine-Adenosine Mechanism involves inhibition by guanosine of transporters involved in adenosine uptake; Aim 5 - To determine whether the Guanosine-Adenosine Mechanism importantly contributes to elevated extracellular levels of adenosine following cellular stress with energy depletion; and Aim 6 - To determine whether the Guanosine-Adenosine Mechanism amplifies the effects of adenosine in vivo.

描述（由申请人提供）：腺苷和鸟嘌呤是天然存在和结构相似的嘌呤。此外，腺苷和鸟嘌呤的自然发生的循环类似物参与了类似的生理过程（例如，CAMP和CGMP介导了血管舒张）。奇怪的是，起初腮红似乎通过用腺苷（而不是鸟苷受体）赋予细胞，从而打破了腺苷和鸟苷之间的对称性。因此，标准视图是腺苷通过激活其自己的细胞表面受体来充当细胞功能的生理调节剂，而鸟氨酸仅仅是闲置的旁观者。该应用程序的目的是通过提出鸟嘌呤在细胞生理学中也起着重要作用来挑战这种收到的观点，而不是通过其自身的受体，而是通过涉及涉及腺苷的强大协作机制。在这方面，我们假设细胞外鸟嘌呤是细胞外腺苷水平的主要生理决定因素，因为鸟苷阻止了腺苷从细胞外室中的处置，从而使腺苷细胞表面受体更大的激活由于增加了细胞外腺苷水平而引起的腺苷细胞表面受体。我们将这种鸟嘌呤 - 腺苷相互作用称为鸟苷 - 腺苷机制。我们的试点实验强烈表明我们的假设是正确的。在肿瘤前血管平滑肌细胞（一种用于微血管平滑肌细胞的模型系统）中，我们观察到，对于添加到细胞中的任何给定数量的腺苷，腺苷的细胞外浓度（通过高性能液相色谱 - 液相色谱 - 质量 - 质量光谱法测量（LC-MS/MS））在Guanosine添加的情况下还要倍增10个细胞。我们还发现细胞应激/损伤会增加鸟苷和腺苷的细胞外水平。此外，我们发现鸟嘌呤可深刻地增强了体内腺苷的生物学作用！这些发现表明，细胞外鸟嘌呤通过阻断细胞外腺苷的处置是最重要的生理决定因素，这些决定因素是尚未发现的腺苷。我们建议以以下六个特定目的来测试鸟嘌呤 - 腺苷机制的存在，机制和重要性：目标1-确定鸟苷 - 腺苷机制在血管和肾细胞类型中的存在；目标2-确定鸟苷 - 腺苷机制是直接由鸟苷直接介导的还是通过将鸟嘌呤转化为鸟嘌呤的。 AIM 3-确定鸟苷 - 腺苷机制是否涉及鸟不能抑制参与腺苷代谢的酶； AIM 4-确定鸟苷 - 腺苷机制是否涉及鸟嘌呤抑制参与腺苷摄取的转运蛋白的抑制作用；目的5-确定鸟苷 - 腺苷机制是否重要地导致细胞外腺苷水平升高随着能量消耗而升高；目标6-确定鸟嘌呤 - 腺苷机制是否会放大体内腺苷的作用。