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Role of the yeast Plasma membrane H+-ATPase in TORC1 control

par Guarini, Nadia Pia
Président du jury Vanhamme, Luc
Promoteur André, Bruno
Publication Non publié, 2024-05-28

Thèse de doctorat

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Résumé :

Plasma membrane H+-ATPases are highly conserved in yeast, other fungi and plants. Their main role is to establish the H+ gradient at the plasma membrane (PM) to maintain the cytosolic pH close to neutral values and fuel the uptake of nutrients through secondary active transport systems. In both plants and yeast, PM H+-ATPases have also been described to promote activation of TORC1, the rapamycin-sensitive kinase complex controlling cell growth. This for instance occurs in yeast upon H+ influx coupled to amino acid uptake. Fungal and plant PM H+-ATPases are self-inhibited by their carboxyterminal tails unless this domain is phosphorylated at specific residues. In the yeast PM H+-ATPase (Pma1), the self-inhibitory action of the carboxyterminal tail is neutralized when the adjacent S911 and T912 are phosphorylated, but the kinase(s) and phosphatase(s) controlling their phosphorylation remain unknown.In this thesis work, with the objective of understanding the molecular events taking place at Pma1`s level upon H+ influx and triggering the signaling cascade towards TORC1, we show that the largely redundant Ptk1 and Ptk2 kinases are responsible for phosphorylating S911-T912 at the carboxyterminal tail of Pma1. We also show that the carboxyterminal tail of Pma1 is not essential to initial TORC1 activation induced by H+-coupled amino acid uptake. However, if not properly phosphorylated by Ptk1 and Ptk2 kinases, the carboxyterminal tail of Pma1 can interfere with TORC1 activation. Additionally, we provide evidence that activated TORC1 exerts negative feedback control on Pma1 by reducing phosphorylation of its carboxyterminal tail.Overall, our results shed important new light on phosphoregulation of the yeast Pma1 H+-ATPase and on its interconnections with TORC1.