TETANUS TOXIN LIGHT-CHAIN CLEAVES A VESICLE-ASSOCIATED MEMBRANE-PROTEIN (VAMP) ISOFORM-2 IN RAT PANCREATIC ZYMOGEN GRANULES AND INHIBITS ENZYME-SECRETION

Citation
Hy. Gaisano et al., TETANUS TOXIN LIGHT-CHAIN CLEAVES A VESICLE-ASSOCIATED MEMBRANE-PROTEIN (VAMP) ISOFORM-2 IN RAT PANCREATIC ZYMOGEN GRANULES AND INHIBITS ENZYME-SECRETION, The Journal of biological chemistry, 269(25), 1994, pp. 17062-17066
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
ISSN journal
0021-9258
Volume
269
Issue
25
Year of publication
1994
Pages
17062 - 17066
Database
ISI
SICI code
0021-9258(1994)269:25<17062:TTLCAV>2.0.ZU;2-X
Abstract
Pancreatic acinar cells, a model cell type for the study of exocytosis in non-excitable cells, were used here to test the hypothesis that mo lecular mechanisms regulating exocytosis from neuronal and neuroendocr ine cells may also be utilized in exocrine cells. Using specific antis era raised against vesicle-associated membrane protein (VAMP) isoforms 1 and 2, we have identified VAMP-2, but not VAMP-1, immunoreactive pr oteins on rat pancreatic acinar cell secretory (zymogen) granules. Thi s 18-kDa protein co-migrated with rat brain synaptic vesicle VAMP-2. T etanus toxin (TeTx) light chain caused complete cleavage of this prote in, which was prevented by the addition of EDTA. This toxin also inhib ited in a dose-dependent manner Ca2+-stimulated enzyme secretion by up to similar to 30% in streptolysin O-permeabilized acini. This effect of TeTx on secretion was prevented by the zinc endopeptidase inhibitor captopril or by boiling the toxin. Incomplete inhibition of secretion by TeTx may suggest that TeTx-insensitive or VAMP-2-independent mecha nisms also regulate exocytosis. In support, TeTx light chain was witho ut effect on Rab3AL, (effector domain peptide of Rab3)-mediated potent iation of Ca2+-stimulated secretion. These results indicate that a TeT x-sensitive VAMP-2-like protein on zymogen granules participates in Ca 2+-regulated pancreatic enzyme secretion and that undefined Rab3AL-act ivated mechanisms may act independently to regulate exocytosis.