Role of vesicle-associated membrane protein 2 in exocytosis of glucagon-like peptide-1 from the murine intestinal L cell

Diabetologia. 2014 Apr;57(4):809-18. doi: 10.1007/s00125-013-3143-2. Epub 2013 Dec 20.


Aims/hypothesis: Glucagon-like peptide-1 (GLP-1), secreted by the enteroendocrine L cell, is an incretin hormone that potently stimulates insulin secretion. Although signalling pathways promoting GLP-1 release are well characterised, the mechanisms by which GLP-1-containing granules fuse to the L cell membrane are unknown. As soluble NSF attachment proteins (SNAREs) are known to mediate granule-membrane fusion, the role of vesicle-associated membrane proteins (VAMPs) in GLP-1 exocytosis was examined.

Methods: SNARE expression was determined in murine GLUTag L cells by RT-PCR and immunoblot and in primary murine L cells by immunofluorescence. Co-immunoprecipitation was used to examine SNARE interactions, while tetanus toxin (TetX)-mediated cleavage of VAMP was used with a GLP-1 secretion assay and total internal reflection fluorescence microscopy to determine the role of VAMP2 in exocytosis.

Results: VAMP2 was expressed in murine L cells and localised to secretory granules in GLUTag cells. VAMP1/3 and the core membrane proteins syntaxin1a and synaptosomal-associated protein 25 kDa (SNAP25) were also detected. TetX cleaved VAMPs in GLUTag cells. However, only VAMP2 interacted with syntaxin1a, as did SNAP25 and Munc18-1. TetX treatment of GLUTag cells prevented glucose-dependent insulinotrophic peptide- and oleic-acid-stimulated GLP-1 secretion (p < 0.05-0.01), as well as K(+)-stimulated single-cell exocytosis (p < 0.05-0.001), while TetX-resistant VAMP2 expression rescued GLP-1 secretion (p < 0.01-0.001).

Conclusions/interpretation: Together, these findings indicate an essential role for VAMP2 in GLP-1 exocytosis from the GLUTag L cell in response to a variety of established secretagogues. An improved understanding of the mechanisms governing the release of GLP-1 may lead to new therapeutic approaches to enhance the levels of this incretin hormone in patients with type 2 diabetes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Enteroendocrine Cells / metabolism*
  • Exocytosis / genetics
  • Exocytosis / physiology*
  • Glucagon-Like Peptide 1 / genetics
  • Glucagon-Like Peptide 1 / metabolism*
  • Mice
  • Vesicle-Associated Membrane Protein 2 / genetics
  • Vesicle-Associated Membrane Protein 2 / metabolism*


  • Vesicle-Associated Membrane Protein 2
  • Glucagon-Like Peptide 1