Chen Z, Lash L H
Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan, USA.
J Pharmacol Exp Ther. 1998 May;285(2):608-18.
The role of organic anion transporters in the mitochondrial uptake of glutathione (GSH) was investigated by assessing competition with substrates or inhibition with inhibitors of specific carriers and modulation of mitochondrial energetics. Potential artifacts in the transport methodology, including contamination of matrix space with extramitochondrial fluid, changes in matrix volume during incubations, efflux of transported GSH during sample processing, induction of the membrane permeability transition, contamination of the mitochondrial preparation with plasma membranes and GSH degradation, were corrected or eliminated. Substrates (i.e., malate, succinate) and an inhibitor (i.e., butylmalonate) of the dicarboxylate carrier, an inhibitor (i.e., phenylsuccinate) of the 2-oxoglutarate carrier, and glutamate produced significant inhibition of GSH uptake whereas substrates and inhibitors of the mono- and tricarboxylate carriers were generally without effect. Phosphoenolpyruvate, which is a substrate for the tricarboxylate carrier, inhibited GSH uptake, but this was due to induction of the membrane permeability transition and not to competition for uptake. Although glutamate inhibited GSH uptake, the converse did not occur. GSH uptake was pH-independent and aspartate had no effect, which suggest that the glutamate and glutamate-aspartate carriers are not involved in GSH uptake but that the glutamyl residue of GSH may be important in its transport. GSH uptake was dependent on phosphate and ATP generation. Hence, we conclude that both the dicarboxylate and 2-oxoglutarate carriers of the inner membrane can catalyze uptake of GSH into the matrix. The function of an additional, novel transporter cannot be excluded at present. This is the first study to define the function of mitochondrial anion carriers in GSH transport.
通过评估与底物的竞争、特定载体抑制剂的抑制作用以及线粒体能量学的调节，研究了有机阴离子转运体在线粒体摄取谷胱甘肽（GSH）中的作用。对转运方法中可能存在的假象进行了校正或消除，这些假象包括线粒体外液污染基质空间、孵育过程中基质体积的变化、样品处理过程中转运的GSH外流、膜通透性转变的诱导、质膜污染线粒体制剂以及GSH降解。二羧酸载体的底物（即苹果酸、琥珀酸）和抑制剂（即丁基丙二酸）、2-氧代戊二酸载体的抑制剂（即苯基琥珀酸）以及谷氨酸对GSH摄取有显著抑制作用，而单羧酸和三羧酸载体的底物和抑制剂通常无作用。作为三羧酸载体底物的磷酸烯醇丙酮酸抑制了GSH摄取，但这是由于诱导了膜通透性转变，而非摄取竞争。虽然谷氨酸抑制了GSH摄取，但反之则未发生。GSH摄取不依赖于pH，天冬氨酸无作用，这表明谷氨酸和谷氨酸-天冬氨酸载体不参与GSH摄取，但GSH的谷氨酰残基在其转运中可能很重要。GSH摄取依赖于磷酸盐和ATP生成。因此，我们得出结论，内膜的二羧酸和2-氧代戊二酸载体均可催化GSH摄取到基质中。目前不能排除存在另一种新型转运体的可能性。这是第一项确定线粒体阴离子载体在GSH转运中功能的研究。
