Munc18c phosphorylation by the insulin receptor links cell signaling directly to SNARE exocytosis

Jenna L Jewell, Eunjin Oh, Latha Ramalingam, Michael A Kalwat, Vincent S Tagliabracci, Lixuan Tackett, Jeffrey S Elmendorf, Debbie C Thurmond

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


How the Sec1/Munc18-syntaxin complex might transition to form the SNARE core complex remains unclear. Toward this, Munc18c tyrosine phosphorylation has been correlated with its dissociation from syntaxin 4. Using 3T3-L1 adipocytes subjected to small interfering ribonucleic acid reduction of Munc18c as a model of impaired insulin-stimulated GLUT4 vesicle exocytosis, we found that coordinate expression of Munc18c-wild type or select phosphomimetic Munc18c mutants, but not phosphodefective mutants, restored GLUT4 vesicle exocytosis, suggesting a requirement for Munc18c tyrosine phosphorylation at Tyr219 and Tyr521. Surprisingly, the insulin receptor (IR) tyrosine kinase was found to target Munc18c at Tyr521 in vitro, rapidly binding and phosphorylating endogenous Munc18c within adipocytes and skeletal muscle. IR, but not phosphatidylinositol 3-kinase, activation was required. Altogether, we identify IR as the first known tyrosine kinase for Munc18c as part of a new insulin-signaling step in GLUT4 vesicle exocytosis, exemplifying a new model for the coordination of SNARE assembly and vesicle mobilization events in response to a single extracellular stimulus.

Original languageEnglish (US)
Pages (from-to)185-99
Number of pages15
JournalJournal of Cell Biology
Issue number1
StatePublished - Apr 4 2011


  • Animals
  • Caenorhabditis elegans
  • Drosophila
  • Exocytosis
  • Humans
  • Mice
  • Models, Molecular
  • Munc18 Proteins/metabolism
  • Phosphorylation
  • Receptor, Insulin/metabolism
  • SNARE Proteins/metabolism
  • Saccharomyces cerevisiae
  • Signal Transduction


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