Trafficking of green fluorescent protein-tagged SNARE proteins in HSY cells

Taishin Takuma, Toshiya Arakawa, Miki Okayama, Itaru Mizoguchi, Akihiko Tanimura, Yoshifumi Tajima

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12 Citations (Scopus)


SNARE proteins are widely accepted to be involved in the docking and fusion process of intracellular vesicle trafficking. VAMP-2, syntaxin-4, and SNAP-23 are plausible candidate SNARE proteins for non-neuronal exocytosis. Thus, we examined the localization, protein-protein interaction, and intracellular trafficking of these proteins by expressing them as green fluorescent protein (GFP)- and FLAG-tagged fusion proteins in various cells, including HSY cells, a human parotid epithelial cell line. GFP-VAMP-2 was expressed strongly in the Golgi area and weakly on the plasma membrane. Although GFP-SNAP-23 seemed to be expressed universally in the cytosol, the GFP signal was clearly seen on the plasma membrane, when soluble GFP-SNAP-23 was removed by treatment with saponin. GFP-syntaxin-4 was undetectable on the plasma membrane but was strongly expressed on unidentified unusually large vesicles. GFP-syntaxin-4 without its transmembrane domain was still incompletely soluble and observed as aggregates. When syntaxin-4 and munc18c were coexpressed, syntaxin-4 was translocated at least in part to the plasma membrane. The protein-protein interaction between syntaxin-4 and VAMP-2 with their transmembrane domains was markedly inhibited on coexpression of munc18c. These results suggest that munc18c plays an important role in the trafficking of syntaxin-4 to its proper destination by preventing premature interactions with other proteins, including SNARE proteins.

Original languageEnglish
Pages (from-to)729-735
Number of pages7
JournalJournal of Biochemistry
Issue number5
Publication statusPublished - 2002 Nov 1


  • Green fluorescent protein
  • Munc18c
  • SNAP-23
  • Syntaxin-4
  • VAMP-2


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