FREE FATTY ACIDS INHIBIT AN ION-COUPLED MEMBRANE TRANSPORTER BY DISSIPATING THE ION GRADIENT.

IF 4 2区 生物学 Q2 BIOCHEMISTRY & MOLECULAR BIOLOGY
Xiaoyu Wang, Radda Rusinova, G Glenn Gregorio, Olga Boudker
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Abstract

Glutamate is the main excitatory transmitter in the mammalian central nervous system; glutamate transporters keep the synaptic glutamate concentrations at bay for normal brain function. Arachidonic acid (AA), docosahexaenoic acid (DHA), and other unsaturated fatty acids modulate glutamate transporters in cell- and tissue slices-based studies. Here, we investigated their effect and mechanism using a purified archaeal glutamate transporter homolog reconstituted into the lipid membranes. AA, DHA, and related fatty acids irreversibly inhibited the sodium-dependent concentrative substrate uptake into lipid vesicles within the physiologically relevant concentration range. In contrast, AA did not inhibit amino acid exchange across the membrane. The length and unsaturation of the aliphatic tail affect inhibition, and the free carboxylic headgroup is necessary. The inhibition potency did not correlate with the fatty acid effects on the bilayer deformation energies. AA does not affect the conformational dynamics of the protein, suggesting it does not inhibit structural transitions necessary for transport. Single-transporter and membrane voltage assays showed that AA and related fatty acids mediate cation leak, dissipating the driving sodium gradient. Thus, such fatty acids can act as cation ionophores, suggesting a general modulatory mechanism of membrane channels and ion-coupled transporters.

游离脂肪酸通过消除离子梯度来抑制离子耦合膜转运体。
谷氨酸是哺乳动物中枢神经系统中的主要兴奋性递质;谷氨酸转运体可控制突触谷氨酸的浓度,从而保证大脑的正常功能。在基于细胞和组织切片的研究中,花生四烯酸(AA)、二十二碳六烯酸(DHA)和其他不饱和脂肪酸可调节谷氨酸转运体。在这里,我们使用重组到脂膜中的纯化古生谷氨酸转运体同源物研究了它们的作用和机制。在生理相关浓度范围内,AA、DHA 和相关脂肪酸不可逆地抑制了钠依赖性浓缩底物摄入脂质囊泡。相比之下,AA 并不抑制氨基酸跨膜交换。脂肪族尾部的长度和不饱和度会影响抑制作用,而游离的羧基头基则是必要的。抑制效力与脂肪酸对双分子层变形能的影响无关。AA 不会影响蛋白质的构象动力学,这表明它不会抑制运输所需的结构转换。单转运体和膜电压测定显示,AA 和相关脂肪酸介导阳离子泄漏,消散驱动钠梯度。因此,这类脂肪酸可以充当阳离子离子促进剂,暗示了膜通道和离子耦合转运体的一般调节机制。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Biological Chemistry
Journal of Biological Chemistry Biochemistry, Genetics and Molecular Biology-Biochemistry
自引率
4.20%
发文量
1233
期刊介绍: The Journal of Biological Chemistry welcomes high-quality science that seeks to elucidate the molecular and cellular basis of biological processes. Papers published in JBC can therefore fall under the umbrellas of not only biological chemistry, chemical biology, or biochemistry, but also allied disciplines such as biophysics, systems biology, RNA biology, immunology, microbiology, neurobiology, epigenetics, computational biology, ’omics, and many more. The outcome of our focus on papers that contribute novel and important mechanistic insights, rather than on a particular topic area, is that JBC is truly a melting pot for scientists across disciplines. In addition, JBC welcomes papers that describe methods that will help scientists push their biochemical inquiries forward and resources that will be of use to the research community.
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