Proteolysis of synaptobrevin, syntaxin, and SNAP-25 in alveolar epithelial type II cells.
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.
Zimmerman
U J
UJ
Institute for Environmental Medicine, University of Pennsylvania Medical Center, Philadelphia 19104-6068, USA. unjin@mail.med.upenn.edu
Malek
S K
SK
Liu
L
L
Li
H L
HL
D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism*; D015153:Blotting, Western; D000001:Calcimycin / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006023:Glycoproteins / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000378:metabolism; D050683:R-SNARE Proteins; D051381:Rats; D012636:Secretory Rate / Q000187:drug effects; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000954:Antigens, Surface; D006023:Glycoproteins; D007476:Ionophores; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010713:Phosphatidylcholines; D011663:Pulmonary Surfactants; D050683:R-SNARE Proteins; C494210:Snap25 protein, rat; C494213:Stx1a protein, rat; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; C039304:calpain inhibitors; D000001:Calcimycin; D002154:Calpain; D013755:Tetradecanoylphorbol Acetate