Activation of the phosphatidylinositol 3-kinase Vps34 by a G protein alpha subunit at the endosome

Cell. 2006 Jul 14;126(1):191-203. doi: 10.1016/j.cell.2006.04.045.

Abstract

In the yeast Saccharomyces cerevisiae, the G protein beta gamma subunits are essential for pheromone signaling. The Galpha subunit Gpa1 can also promote signaling, but the effectors in this pathway are not well characterized. To identify candidate Gpa1 effectors, we expressed the constitutively active Gpa1(Q323L) mutant in each of nearly 5000 gene-deletion strains and measured mating-specific responses. Our analysis reveals a requirement for both the catalytic (Vps34) and regulatory (Vps15) subunits of the sole phosphatidylinositol 3-kinase in yeast. We demonstrate that Gpa1 is present at endosomes, where it interacts directly with both Vps34 and Vps15 and stimulates increased production of phosphatidylinositol 3-phosphate. Notably, Vps15 binds to GDP-bound Gpa1 and is predicted to have a seven-WD repeat structure similar to that of known G protein beta subunits. These findings reveal two new components of the pheromone signaling pathway. More remarkably, these proteins appear to comprise a preformed effector-G beta subunit assembly and function at the endosome rather than at the plasma membrane.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites / physiology
  • Endosomal Sorting Complexes Required for Transport
  • Endosomes / enzymology*
  • Endosomes / genetics
  • Enzyme Activation / physiology*
  • GTP-Binding Protein alpha Subunits / genetics
  • GTP-Binding Protein alpha Subunits / metabolism*
  • Guanosine Diphosphate / metabolism
  • Mutation / physiology
  • Pheromones / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphatidylinositol Phosphates / biosynthesis
  • Protein Binding / physiology
  • Protein Serine-Threonine Kinases / chemistry
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Protein Structure, Tertiary / physiology
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins
  • Signal Transduction / physiology
  • Up-Regulation / physiology
  • Vacuolar Sorting Protein VPS15

Substances

  • Endosomal Sorting Complexes Required for Transport
  • GTP-Binding Protein alpha Subunits
  • Pheromones
  • Phosphatidylinositol Phosphates
  • Saccharomyces cerevisiae Proteins
  • Guanosine Diphosphate
  • Protein Serine-Threonine Kinases
  • VPS15 protein, S cerevisiae
  • Vacuolar Sorting Protein VPS15