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t-SNARE dephosphorylation promotes SNARE assembly and exocytosis in yeast.

The role of protein phosphorylation in secretion is not well understood. Here we show that yeast lacking the Snc1,2 v-SNAREs, or bearing a temperature-sensitive mutation in the Sso2 t-SNARE, are rescued at restrictive conditions by the addition of ceramide precursors and analogs to the growth medium. Rescue results from dephosphorylation of the Sso t-SNAREs by a ceramide-activated type 2A protein phosphatase (Sit4) involved in cell cycle control. Sso t-SNARE dephosphorylation correlated with its assembly into complexes with the Sec9 t-SNARE, both in vitro and in vivo, and with an increase in protein trafficking and secretion in cells. SNARE complexes isolated under these conditions contained only Sso and Sec9, suggesting that a t-t-SNARE fusion complex is sufficient to confer exocytosis. Mutation of a single PKA site (Ser79 to Ala79) in Sso1 resulted in a decrease in phosphorylation and was sufficient to confer growth to snc cells at restrictive conditions. Thus, modulation of t-SNARE phosphorylation regulates SNARE complex assembly and membrane fusion in vivo.

Pubmed ID: 11157748


  • Marash M
  • Gerst JE


The EMBO journal

Publication Data

February 1, 2001

Associated Grants


Mesh Terms

  • Exocytosis
  • Fungal Proteins
  • Membrane Fusion
  • Membrane Proteins
  • Models, Biological
  • Mutagenesis, Site-Directed
  • Mutation
  • Phosphoprotein Phosphatases
  • Phosphorylation
  • Qa-SNARE Proteins
  • SNARE Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sphingosine
  • Temperature
  • Vesicular Transport Proteins