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Regulation of tetrahydrobiopterin and monoamine transport by cyclic GMP

环 GMP 对四氢生物蝶呤和单胺转运的调节

基本信息

批准号：
14571774
负责人：
NAKANISHI Nobuo
金额：
$ 2.24万
依托单位：
Meikai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

项目摘要

We found that the vesicular monoamine transport activity of neuronal cell line, PC12, was stimulated by cyclic GMP (cGMP) while it was inhibited by cyclic AMP (cAMP). We also found that both cGMP and cAMP down-regulated the transport of tetrahydrobiopterin (BH4), a cofactor for nitric oxide synthase and for aromatic amino acid hydroxylases, through plasma membranes of various cells. In this works, we examined the mechanisms of BH4 transport and the effects of cGMP on the BH4 transport and on the vesicular monoamine transport.1.BH4 transport : Outward flow of endogenous BH4 to extracellular fluid and inward flow of exogenous BH4 into the cells were mediated by different transport systems. Three pathways were found to be present for BH4 outward flow : 1)a pathway by transporter belonged to ion gradient-dependent toxin-extruding antiporter (TEXAN) family. This type of BH4 transporter was down-regulated by cGMP. 2)a pathway which was sensitive to osmotic pressure and involved a membrane protein belonged to aquaporin family for BH4 transport. This pathway was therefore regulated by Na+-K+-ATPase and ion transporters for K+ and Cl- ions. 3)a pathway mediated by a member of ABC transporter family such as multi-drug resistant protein (MDR).On the other hand, BH4 transporter which is responsible for exogenous BH4 uptake into cytoplasm was specifically present in intestinal epithelial cells and in kidney. This type of BH4 transport activity was also detected in erythrocytes.2.Vesicular monoamine transport : Vesicular monoamine transport was up-regulated by cGMP in a dose-dependent manner. Phosphorylation of the vesicular monoamine transporter (VMAT) molecules by cGMP was not detected. cGMP seemed to affect the targeting of VMAT molecules to the vesicular membranes. Studies is in progress to search proteins which might be involved in the VMAT targeting to the secretory vesicle membranes as a mediater of cGMP effect.

我们发现，神经元细胞系PC 12的囊泡单胺转运活性被环磷酸鸟苷（cGMP）激活，而被环磷酸腺苷（cAMP）抑制。我们还发现，cGMP和cAMP下调四氢生物蝶呤（BH 4），一氧化氮合酶和芳香族氨基酸羟化酶的辅因子，通过质膜的各种细胞的运输。本研究探讨了BH_4的转运机制以及cGMP对BH_4转运和囊泡单胺转运的影响。1.BH_4转运：内源性BH_4向细胞外液的外流和外源性BH_4向细胞内的内流是由不同的转运系统介导的。BH_4的外流存在三条途径：1）离子梯度依赖的毒素挤压反向转运蛋白（TEXAN）家族转运蛋白途径;这种类型的BH 4转运蛋白被cGMP下调。2）渗透压敏感的BH_4转运途径，该途径涉及水通道蛋白家族的膜蛋白。因此，这一途径受到Na+-K+-ATP酶和K+和Cl-离子转运蛋白的调节。（3）由ABC转运蛋白家族成员如多药耐药蛋白（MDR）介导的途径，而BH_4转运蛋白则特异性地存在于肠上皮细胞和肾脏中，负责外源性BH_4进入细胞质。2.囊泡单胺转运：cGMP以剂量依赖方式上调囊泡单胺转运。未检测到cGMP对囊泡单胺转运蛋白（VMAT）分子的磷酸化。cGMP似乎影响VMAT分子靶向囊泡膜。研究正在进行中，以寻找可能参与VMAT靶向分泌囊泡膜作为cGMP效应的介导物的蛋白质。