Amino acid homeostatic control by TORC1 in Saccharomyces cerevisiae under high hydrostatic pressure

Abstract

Mechanical stresses including high hydrostatic pressure elicit diverse physiological effects on organisms. Gtr1/Gtr2 and Ego1/Ego3, central regulators of the TOR complex 1 (TORC1) nutrient signaling pathway, are required for the growth of Saccharomyces cerevisiae cells under high pressure. Here, we showed that a pressure of 25 MPa stimulates TORC1 to promote phosphorylation of Sch9, which depends on the EGO complex (EGOC) and Pib2. Incubation of cells at this pressure aberrantly increased the glutamine and alanine levels in the ego1Δ, gtr1Δ, tor1Δ, and pib2Δ mutants, whereas the polysome profiles were unaffected. Moreover, we found that glutamine levels were reduced by combined deletions of EGO1, GTR1, TOR1, and PIB2 with GLN3. These results suggested that high pressure leads to the intracellular accumulation of amino acids. Subsequently, Pib2 loaded with glutamine stimulates the EGOC–TORC1 complex to inactivate Gln3, downregulating glutamine synthesis. Our findings illustrated the regulatory circuit that maintained the intracellular amino acid homeostasis and suggested the critical roles the EGOC–TORC1 and Pib2–TORC1 complexes played in the growth of yeast under high hydrostatic pressure.