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

• Published in: The Journal of biological chemistry p. 107955
• Main Authors: Wang, Xiaoyu, Rusinova, Radda, Gregorio, G. Glenn, Boudker, Olga
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 02-11-2024
• Subjects: arachidonic acid (AA) (ARA); docosahexaenoic acid (DHA); fatty acid; free fatty acid; glutamate; glutamate transporter; membrane bilayer; membrane permeation; membrane transport; membrane transporter; polyunsaturated fatty acid (PUFA); arachidonic acid (AA) (ARA); glutamate transporter; docosahexaenoic acid (DHA); free fatty acid; polyunsaturated fatty acid (PUFA); membrane bilayer; membrane transporter; fatty acid; membrane transport; membrane permeation; glutamate
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1016/j.jbc.2024.107955

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.