Dibutyryl-cAMP (dbcAMP) up-regulates astrocytic chloride-dependent L-[3H]glutamate transport and expression of both system xc- subunits
Dibutyryl-cAMP (dbcAMP) up-regulates astrocytic chloride-dependent L-[3H]glutamate transport and expression of both system xc- subunits
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DOI：
10.1046/j.1471-4159.2001.00385.x
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发表时间：
2001-07-01
影响因子：
4.7
通讯作者：
Robinson, MB
中科院分区：
文献类型：
--
作者：
Gochenauer, GE;Robinson, MB
最近的研究表明，N-6，2 ' -O-二丁酰腺苷3 '：5 '环一磷酸（dbcAMP）可增加培养的星形胶质细胞中Na+依赖性谷氨酸转运蛋白的特定亚型的表达。我们的小组还发现，用dbcAMP处理星形胶质细胞数天增加了L-[H-3]谷氨酸盐的Na+非依赖性积累。在这项研究中，这个Na+-独立的积累的特性进行了表征，并通过dbcAMP上调这一过程的机制进行了研究。这种积累在没有Cl-的情况下显著减少，并且还被几种阴离子交换抑制剂抑制，包括4，4 ' -二异硫氰酸基芪-2，2' -二磺酸、4，4 ' -二硝基芪-2，2' -二磺酸和4-乙酰氨基-4 ' -异硫氰酸基芪-2，2' -二磺酸，表明这种活性是由Cl-依赖性转运蛋白介导的。此外，该活性被微摩尔浓度的另一种Cl-依赖性（Na+非依赖性）转运活性的几种抑制剂抑制，通常称为系统x（c）（-）（L-胱氨酸、L-α-氨基己二酸、L-高半胱氨酸、使君子酸、β-N-草酰-l-α，β-二氨基丙酸、鹅膏蕈氨酸）。这种活性被竞争性抑制的几个苯甘氨酸衍生物以前表征为代谢型谷氨酸受体激活的抑制剂。比较dbcAMP处理和未处理星形胶质细胞的Na+-非依赖性、Cl-依赖性L-[H-3]谷氨酸摄取活性的浓度依赖性。用dbcAMP治疗增加了6倍，但没有影响的Km值的V-max的Cl-依赖的运输活动。系统x（c）（-）需要两个亚基xCT和4F 2 hc/CD 98来重建功能活性。我们发现，dbcAMP导致xCT mRNA水平增加两倍，4F 2 hc/CD 98蛋白水平增加七倍。这项研究表明，dbcAMP上调星形胶质细胞中Cl-依赖的L-[H-3]谷氨酸转运活性，并表明这种作用与系统x（c）（-）两个亚基的表达增加有关。由于这种活性被认为是重要的谷胱甘肽的合成和保护氧化损伤，了解系统x（c）（-）的调节可能会提供替代方法来限制这种形式的损伤。
Recent studies have shown that N-6,2 ' -O-dibutyryladenosine 3 ' :5 ' cyclic monophosphate (dbcAMP) increases the expression of specific subtypes of Na+-dependent glutamate transporters in cultured astrocytes. Our group also found that treatment of astrocytes with dbcAMP for several days increases the Na+-independent accumulation of L-[H-3]glutamate. In this study, the properties of this Na+-independent accumulation were characterized, and the mechanism by which dbcAMP up-regulates this process was investigated. This accumulation was markedly reduced in the absence of Cl- and was also inhibited by several anion-exchange inhibitors, including 4,4 ' -diisothiocyanatostilbene-2,2 ' -disulfonic acid, 4,4 ' -dinitrostilbene-2,2 ' -disulfonic acid and 4-acetamido-4 ' -isothiocyanatostilbene-2,2 ' -disulfonic acid, suggesting that this activity is mediated by a Cl--dependent transporter. In addition, this activity was inhibited by micromolar concentrations of several inhibitors of another Cl--dependent (Na+-independent) transport activity frequently referred to as system x(c)(-) (L-cystine, L-alpha -aminoadipate, L-homocysteate, quisqualate, beta -N-oxalyl-l-alpha,beta -diaminopropionate, ibotenate). This activity was competitively inhibited by several phenylglycine derivatives previously characterized as inhibitors of metabotropic glutamate receptor activation. The concentration-dependence for Na+-independent, Cl--dependent L-[H-3]glutamate uptake activity was compared for dbcAMP-treated and untreated astrocytes. Treatment with dbcAMP increased the V-max of this Cl--dependent transport activity by sixfold but had no effect on the K-m value. System x(c)(-) requires two subunits, xCT and 4F2hc/CD98, to reconstitute functional activity. We found that dbcAMP caused a twofold increase in the levels of xCT mRNA and a sevenfold increase in the levels of 4F2hc/CD98 protein. This study indicates that dbcAMP up-regulates Cl--dependent L-[H-3]glutamate transport activity in astrocytes and suggests that this effect is related to increased expression of both subunits of system x(c)(-). Because this activity is thought to be important for the synthesis of glutathione and protection from oxidant injury, understanding the regulation of system x(c)(-) may provide alternate approaches to limit this form of injury.