Analysis of the roles of phosphatidylinositol-4,5- bis phosphate and individual subunits in assembly, localization, and function of Saccharomyces cerevisiae target of rapamycin complex 2

Mol Biol Cell. 2019 Jun 1;30(12):1555-1574. doi: 10.1091/mbc.E18-10-0682. Epub 2019 Apr 10.

Abstract

Eukaryotic cell survival requires maintenance of plasma membrane (PM) homeostasis in response to environmental insults and changes in lipid metabolism. In yeast, a key regulator of PM homeostasis is target of rapamycin (TOR) complex 2 (TORC2), a multiprotein complex containing the evolutionarily conserved TOR protein kinase isoform Tor2. PM localization is essential for TORC2 function. One core TORC2 subunit (Avo1) and two TORC2--associated regulators (Slm1 and Slm2) contain pleckstrin homology (PH) domains that exhibit specificity for binding phosphatidylinositol-4,5-bisphosphate (PtdIns4,5P2). To investigate the roles of PtdIns4,5P2 and constituent subunits of TORC2, we used auxin-inducible degradation to systematically eliminate these factors and then examined localization, association, and function of the remaining TORC2 components. We found that PtdIns4,5P2 depletion significantly reduced TORC2 activity, yet did not prevent PM localization or disassembly of TORC2. Moreover, truncated Avo1 (lacking its C-terminal PH domain) was still recruited to the PM and supported growth. Even when all three PH-containing proteins were absent, the remaining TORC2 subunits were PM-bound. Revealingly, Avo3 localized to the PM independent of both Avo1 and Tor2, whereas both Tor2 and Avo1 required Avo3 for their PM anchoring. Our findings provide new mechanistic information about TORC2 and pinpoint Avo3 as pivotal for TORC2 PM localization and assembly in vivo.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Armadillo Domain Proteins / chemistry
  • Armadillo Domain Proteins / metabolism
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism
  • Cell Membrane / metabolism
  • Mechanistic Target of Rapamycin Complex 2 / metabolism*
  • Phosphatidylinositol 4,5-Diphosphate / metabolism*
  • Protein Domains
  • Protein Subunits / metabolism*
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism

Substances

  • Armadillo Domain Proteins
  • Avo1 protein, S cerevisiae
  • Carrier Proteins
  • Phosphatidylinositol 4,5-Diphosphate
  • Protein Subunits
  • Saccharomyces cerevisiae Proteins
  • TSC11 protein, S cerevisiae
  • Mechanistic Target of Rapamycin Complex 2