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The signaling lipid phosphatidylinositol-3,5-bisphosphate targets plant CLC-a anion/H+exchange activity

By Armando Carpaneto, Anna Boccaccio, Laura Lagostena, Eleonora Di Zanni and Joachim Scholz-Starke

Abstract

Phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2) is a low-abundance signaling lipid associated with endo-lysosomal and vacuolar membranes in eukaryotic cells. Recent studies on Arabidopsis indicated a critical role of PI(3,5)P2in vacuolar acidification and morphology during ABA-induced stomatal closure, but the molecular targets in plant cells remained unknown. By using patch-clamp recordings on Arabidopsis vacuoles, we show here that PI(3,5)P2does not affect the activity of vacuolar H+-pyrophosphatase or vacuolar H+-ATPase. Instead, PI(3,5)P2at low nanomolar concentrations inhibited an inwardly rectifying conductance, which appeared upon vacuolar acidification elicited by prolonged H+pumping activity. We provide evidence that this novel conductance is mediated by chloride channel a (CLC-a), a member of the anion/H+exchanger family formerly implicated in stomatal movements in Arabidopsis. H+-dependent currents were absent in clc-a knock-out vacuoles, and canonical CLC-a-dependent nitrate/H+antiport was inhibited by low concentrations of PI(3,5)P2. Finally, using the pH indicator probe BCECF, we show that CLC-a inhibition contributes to vacuolar acidification. These data provide a mechanistic explanation for the essential role of PI(3,5)P2and advance our knowledge about the regulation of vacuolar ion transport

Topics: patch-clamp, phosphoinositide, proton antiport, vacuolar acidification, Anions, Arabidopsis, Arabidopsis Proteins, Biological Transport, Chloride Channels, Hydrogen-Ion Concentration, Ion Transport, Lysosomes, Phosphatidylinositol Phosphates, Vacuolar Proton-Translocating ATPases, Vacuoles, Signal Transduction, Biochemistry, Molecular Biology, Genetics
Publisher: 'EMBO'
Year: 2017
DOI identifier: 10.15252/embr.201643814
OAI identifier: oai:iris.unige.it:11567/929472
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