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XB-ART-54784
Plant Cell 2018 May 01;305:1147-1164. doi: 10.1105/tpc.17.00864.
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Aluminum-Activated Malate Transporters Can Facilitate GABA Transport.

Ramesh SA , Kamran M , Sullivan W , Chirkova L , Okamoto M , Degryse F , McLaughlin M , Gilliham M , Tyerman SD .


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Plant aluminum-activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals, leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires a specific amino acid motif in ALMTs that shares similarity with a GABA binding site in mammalian GABAA receptors. Here, we explore why TaALMT1 activation leads to a negative correlation between malate efflux and endogenous GABA concentrations ([GABA]i) in both wheat (Triticum aestivum) root tips and in heterologous expression systems. We show that TaALMT1 activation reduces [GABA]i because TaALMT1 facilitates GABA efflux but GABA does not complex Al3+ TaALMT1 also leads to GABA transport into cells, demonstrated by a yeast complementation assay and via 14C-GABA uptake into TaALMT1-expressing Xenopus laevis oocytes; this was found to be a general feature of all ALMTs we examined. Mutation of the GABA motif (TaALMT1F213C) prevented both GABA influx and efflux, and resulted in no correlation between malate efflux and [GABA]i We conclude that ALMTs are likely to act as both GABA and anion transporters in planta. GABA and malate appear to interact with ALMTs in a complex manner to regulate each other's transport, suggestive of a role for ALMTs in communicating metabolic status.

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Species referenced: Xenopus laevis
Genes referenced: gabarap

References [+] :
Albrecht, Aluminum chloride stimulates NACl-dependent release of taurine and ?-aminobutyric acid in rat cortical astrocytes. 1991, Pubmed