GABA and pancreatic β-cells: Colocalization of glutamic acid decarboxylase (GAD) and GABA with synaptic-like microvesicles suggests their role in GABA storage and secretion

A. Reetz, M. Solimena, M. Matteoli, F. Folli, K. Takei, P. De Camilli

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307 Scopus citations


GABA, a major inhibitory neurotransmitter of the brain, is also present at high concentration in pancreatic islets. Current evidence suggests that within islets GABA is secreted from β-cells and regulates the function of mantle cells (α- and δ-cells). In the nervous system GABA is stored in, and secreted from, synaptic vesicles. The mechanism of GABA secretion from β-cells remains to be elucidated. Recently the existence of synaptic-like microvesicles has been demonstrated in some peptide-secreting endocrine cells. The function of these vesicles is so far unknown. The proposed paracrine action of GABA in pancreatic islets makes β-cells a useful model system to explore the possibility that synaptic-like microvesicles, like synaptic vesicles, are involved in the storage and release of non-peptide neurotransmitters. We report here the presence of synaptic-like microvesicles in β-cells and in β-cell lines. Some β-cells in culture were found to extend neurite-like processes. When these were present, synaptic-like microvesicles were particularly concentrated in their distal portions. The GABA synthesizing enzyme, glutamic acid decarboxylase (GAD), was found to be localized around synaptic-like microvesicles. This was similar to the localization of GAD around synaptic vesicles in GABA-secreting neurons. GABA immunoreactivity was found to be concentrated in regions of β-cells which were enriched in synaptic-like microvesicles. These findings suggest that in β-cells synaptic-like microvesicles are storage organelles for GABA and support the hypothesis that storage of non-peptide signal molecules destined for secretion might be a general feature of synaptic-like microvesicles of endocrine cells.

Original languageEnglish (US)
Pages (from-to)1275-1284
Number of pages10
JournalEMBO Journal
Issue number5
StatePublished - May 8 1991



  • GABA
  • diabetes
  • glutamic acid decarboxylase
  • synaptic vesicle
  • β-cell

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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