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.

The CWI pathway is activated through high hydrostatic pressure, enhancing glycerol efflux via the aquaglyceroporin Fps1 inSaccharomyces cerevisiae

“…Our previous studies have shown that defects in TRP1, TAT2 , TORC1-EGOC, or poorly characterized genes such as EHG1/MAY24 cause severe high-pressure sensitivity (Abe & Horikoshi, 2000, Abe & Minegishi, 2008, Kurosaka et al, 2019, Uemura et al, 2020). On the contrary, the defects in the CWI pathway and Fps1 shown in this study caused relatively mild sensitivity to high-pressure.…”

“…Incubation of yeast cells at 25 MPa for 5 h resulted in the upregulation of the DAN/TIR family mannoprotein genes, which are known to be induced under hypoxic conditions and at low temperatures (Abe, 2007b). Target of rapamycin complex 1 (TORC1), an evolutionarily conserved serine/threonine kinase in eukaryotes, was activated by a pressure of 25 MPa (Uemura et al, 2020). We demonstrated that TORC1 plays a critical role in maintaining an appropriate glutamine level under high pressure by downregulating the de novo synthesis of glutamine (Uemura et al, 2020).…”

“…Target of rapamycin complex 1 (TORC1), an evolutionarily conserved serine/threonine kinase in eukaryotes, was activated by a pressure of 25 MPa (Uemura et al , 2020). We demonstrated that TORC1 plays a critical role in maintaining an appropriate glutamine level under high pressure by downregulating the de novo synthesis of glutamine (Uemura et al , 2020). Such evidence indicates that high-pressure stress induces diverse changes in intracellular processes and that cells survive by adaptively coping with each change.…”

Molecular Responses to High Hydrostatic Pressure in Eukaryotes: Genetic Insights from Studies on Saccharomyces cerevisiae

“…However, when the cells are starved or exposed to lethal stresses, TORC1 signaling is repressed, which leads to the downregulation of protein synthesis and effectively arrests cell growth [ 81 , 82 , 83 , 84 ]. A pressure of 25 MPa stimulated TORC1 to promote the phosphorylation of a downstream effector protein such as Sch9 [ 85 ]. This stimulation depends on the intracellular glutamine sensor protein, Pib2.…”

“…Mutants with deleted EGOC complex have an aberrant increase in glutamine levels. Therefore, the EGOC–TORC1 complex plays a critical role in maintaining an appropriate glutamine level under high pressure by downregulating the de novo synthesis of glutamine [ 85 ]. Although the mechanism by which high pressure causes glutamate accumulation is unclear, these findings provide a unique framework for understanding metabolic adaptation to high pressure.…”