The Stress-Sensing TORC2 Complex Activates Yeast AGC-Family Protein Kinase Ypk1 at Multiple Novel Sites.

Yeast (Saccharomyces cerevisiae) target of rapamycin (TOR) complex 2 (TORC2) is a multi-subunit plasma membrane-associated protein kinase and vital growth regulator. Its essential functions are exerted via phosphorylation and stimulation of downstream protein kinase Ypk1 (and its paralog Ypk2). Ypk1 phosphorylates multiple substrates to regulate plasma membrane lipid and protein ...
composition. Ypk1 function requires phosphorylation of Thr504 in its activation loop by eisosome-associated Pkh1 (and its paralog Pkh2). For cell survival under certain stresses, however, Ypk1 activity requires further stimulation by TORC2-mediated phosphorylation at C-terminal sites, dubbed the "turn" (Ser644) and "hydrophobic" (Thr662) motifs. Here we show that four additional C-terminal sites are phosphorylated in a TORC2-dependent manner, collectively defining a minimal consensus. We found that the newly identified sites are as important for Ypk1 activity, stability, and biological function as Ser644 and Thr662. Ala substitutions at the four new sites abrogated the ability of Ypk1 to rescue the phenotypes of Ypk1 deficiency, whereas Glu substitutions had no ill effect. Combining the Ala substitutions with an N-terminal mutation (D242A), which has been demonstrated to bypass the need for TORC2-mediated phosphorylation, restored the ability to complement a Ypk1-deficient cell. These findings provide new insights about the molecular basis for TORC2-dependent activation of Ypk1.
Mesh Terms:
Amino Acid Substitution, Enzyme Stability, Gene Expression Regulation, Fungal, Mechanistic Target of Rapamycin Complex 2, Phosphorylation, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Serine, Stress, Physiological, Threonine
Genetics
Date: Dec. 01, 2016
Download Curated Data For This Publication
208846
Switch View:
  • Interactions 3