Syntaxins are major components of vesicle trafficking and their pattern of expression depends on the cell type. Using
reverse transcriptase-polymerase chain reaction (RT-PCR), cloning, and sequencing techniques, we have found that human neutrophils and neutrophil-differentiated HL-60 cells co-express
syntaxins 1A, 3, 4, 5, 6, 7, 9, 11, and 16. These genes are also expressed in human peripheral blood lymphocytes and SH-SY5Y
neuroblastoma cells, which, unlike neutrophils, also expressed
syntaxin 10. We have identified two
isoforms of
syntaxin 3.
Syntaxin 3A, similar to the previously reported
syntaxin 3, and the novel
isoform syntaxin 3B, which is identical to
syntaxin 3A but lacks 37
amino acid residues at the carboxy-terminal region.
Syntaxin 1 was mainly located to neutrophil granule membranes by confocal microscopy and by immunoblotting of subcellular fractions. These data indicate that
syntaxin 1 cannot be considered specific to neural tissues. The level of expression of
syntaxins 3, 4, 6, and 11 was increased during neutrophil differentiation of HL-60 cells, whereas that of
syntaxins 1A, 5, 9, and 16 was unchanged.
Syntaxin 7 was not expressed in undifferentiated HL-60 cells, but its expression was induced on neutrophil differentiation. The expression of several
syntaxin genes in human neutrophils could be related to the high secretory capacity of these cells as well as to the presence of different cytoplasmic granules with distinct exocytic capabilities.