Botulinum neurotoxin F, a VAMP-specific endopeptidase, inhibits Ca2+-stimulated GH secretion from rat pituitary cells

Botulinum neurotoxin F (BoNTx F) is a zinc-dependent endopeptidase that causes proteolytic cleavage of the Vesicle protein VAMP (vesicle-associated membrane protein). VAMP is an important component of the molecular machinery regulating docking and fusion of secretory vesicles with the target membrane. We have investigated presence of VAMP protein in cultured rat anterior pituitary cells. Confocal laser microscopy revealed presence of VAMP-like immunoreactivity in secretory granules of GH-containing cultured rat anterior pituitary cells. Using BoNTx F, we have investigated whether VAMP is involved in growth hormone (GH) secretion. Treatment of streptolysin-O permeabilized GH-secreting cells with BoNTx F (2.0 and 20 nM) significantly inhibited Ca2+-induced GH release. The results show that the secretory granules of rat anterior pituitary cells contain VAMP protein and suggest that VAMP is of importance in regulating Ca2+-mediated GH secretion. (C) 1997 Elsevier Science B.V.