Zimmerman U J, Malek S K, Liu L, Li H L
Institute for Environmental Medicine, University of Pennsylvania Medical Center, Philadelphia 19104-6068, USA.
IUBMB Life. 1999 Oct;48(4):453-8. doi: 10.1080/713803537.
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.
通过蛋白质印迹分析在大鼠II型肺泡上皮细胞中鉴定出突触小泡蛋白-2、 syntaxin-1和SNAP-25。突触小泡蛋白-2定位于板层小体中，而syntaxin-1和SNAP-25分别存在于II型细胞0.4%的非离子型去污剂P40可溶性和不溶性组分中。当分离的II型细胞用钙离子载体A23187或佛波醇12-肉豆蔻酸酯13-乙酸酯刺激分泌时，发现这些蛋白质已被蛋白酶解。然而，用钙蛋白酶抑制剂II（N-乙酰亮氨酰亮氨酰甲硫氨酸）对细胞进行预孵育可防止蛋白酶解。用外源性钙蛋白酶处理细胞裂解物导致这些蛋白质随时间减少。数据表明，在受刺激分泌的完整II型细胞中，突触小泡蛋白、syntaxin和SNAP-25会受到活化钙蛋白酶的蛋白水解修饰。
