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Proteolysis of Synaptobrevin, Syntaxin, and Snap‐25 in Alveolar Epithelial Type II Cells
Author(s) -
Zimmerman UnJin P.,
Malek Syeda K.,
Liu Lin,
Li Hong Lan
Publication year - 1999
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/713803537
Subject(s) - calpain , synaptobrevin , syntaxin , syntaxin 3 , secretion , proteolysis , microbiology and biotechnology , chemistry , western blot , biochemistry , exocytosis , biology , membrane , synaptic vesicle , vesicle , enzyme , gene
Synaptobrevin‐2, syntaxin‐1, and SNAP‐25 were identified in rat alveolar epithelial type II cells by Western blot analysis. Synaptobrevin‐2 was localized in the lamellar bodies, and syntaxin‐1 and SNAP‐25 were found in 0.4% Nonidet P40‐soluble and ‐insoluble fractions, respectively, of the type II cells. When the isolated type II cells were stimulated for secretion with calcium ionophore A23187 or with phorbol 12‐myristate 13‐acetate, these proteins were found to have been proteolyzed. Preincubation of cells with calpain inhibitor II (N‐acetylleucylleucylmethionine), however, prevented the proteolysis. Treatment of the cell lysate with exogenous calpain resulted in a time‐dependent decrease of these proteins. The data suggest that synaptobrevin, syntaxin, and SNAP‐25 are subject to proteolytic modification by activated calpain in intact type II cells stimulated for secretion.