Abstracts (complete list) - Wissenschaft Online

Simon Frank, Leif Sander, Stephan Bischoff, Axel Lorentz
SNARE proteins in mature primary human mast cells
Rationale: Mediator release of mast cells is a key process in allergic reactions. The
events facilitating the fusion of granule and plasma membrane in the course of mast cell
degranulation are not clear. SNARE (Soluble NSF Attachment Protein Receptors)
proteins have been demonstrated to be involved in fusion of opposing membrane layers
during exocytosis. Here, we analyzed expression of SNARE isoforms in human mast
cells and which of them might be crucial for mast cell degranulation. Methods: Human
mast cells were isolated and purified from surgical specimen of intestinal mucosa, using
enzymatic digestion and MACS-technique. SNARE-protein expression was demonstrated
employing RT-PCR and Western blot. Interaction of SNAREs was analyzed by
immunofluorescence and immunoprecipitation. Results: Mature primary human mast
cells express the tSNAREs (=target SNAREs) Stx-1B, Stx-2, Stx-3, Stx-4 and SNAP-23,
but not SNAP-25, and the vSNAREs (=vesicular SNAREs) VAMP-3, VAMP-7, and VAMP-
8. VAMP-2, which has been demonstrated to play a key role in eosinophil exocytosis,
was only expressed at very low levels. SNAP-23 formed complexes with VAMP-7 and
Syntaxin-4. Fluorescence microscopy revealed translocation of both VAMP-7 and VAMP-
8 to the plasma membrane upon stimulation of the cells using 10-6 M iono/PMA.
Conclusion: Human mast cells express a specific pattern of SNARE isoforms which are
able to form stable complexes. SNAREs might play a major role in human mast cell
exocytosis; inhibition of which could represent a novel therapeutical approach in
treatment of allergic disorders.