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J Biol Chem, Vol. 273, Issue 32, 20046-20051, August 7, 1998
From the ¶ Endocrine Laboratory, Royal Victoria Hospital,
Montreal, Quebec H3A 1A1, We have used a sensitive bioassay of
calcium-mediated volume changes in mammalian absorptive intestinal
epithelial cells to screen extracts of the skin of the amphibian
Xenopus laevis for the presence of factors affecting ion
transport. A 66-residue peptide, purified using reversed-phase high
performance liquid chromatography techniques, caused isotonic volume
reduction of guinea pig jejunal villus cells in suspension. This volume
reduction required extracellular Ca2+ and was prevented by
the dihydropyridine-sensitive Ca2+ channel blocker
niguldipine. Structural analysis demonstrated the presence of eight
cysteines and a primary structure homologous to that of the
neurotoxin/cytotoxin family found in the venom of certain poisonous
snakes. The structure of the peptide was identical to that of xenoxin-1
purified from dorsal gland secretions of X. laevis (Kolbe,
M., Huber A., Cordier, P., Rasmussen, U., Bouchon, B., Jaquinod, M.,
Blasak, R., Detot, E., and Kreil, G. (1993) J. Biol.
Chem. 268, 16458-16464). Xenoxin-1 (10 nM) caused volume changes that required extracellular Ca2+ and were
comparable in magnitude and direction to changes caused by BayK-8644
(100 nM), a dihydropyridine-sensitive Ca2+
channel agonist. The initial rate of dihydropyridine-sensitive 45Ca2+ influx was substantially increased by
xenoxin-1. Staurosporine (10 nM) prevented volume changes
caused by ATP (250 µM) but had no effect on volume
changes caused by BayK-8644 or xenoxin-1. We conclude that xenoxin-1
directly activated dihydropyridine-sensitive Ca2+ channels
in villus cells and that a mammalian homologue to xenoxin-1 may
exist.
Isolation of a Member of the Neurotoxin/Cytotoxin Peptide Family
from Xenopus laevis Skin Which Activates
Dihydropyridine-sensitive Ca2+ Channels in Mammalian
Epithelial Cells
,
,
Gastroenterology Division,
Department of Pediatrics, Montreal Childrens Hospital Research
Institute, and Faculty of Medicine, McGill University, Montreal,
Quebec H3H 1P3, Canada
Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc.
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