Liu L, Fisher A B, Zimmerman U J
Institute For Environmental Medicine, University of Pennsylvania, School of Medicine, Philadelphia 19104, USA.
Biochem Mol Biol Int. 1995 Jun;36(2):373-81.
Limited proteolysis of annexin I occurs endogenously in intact rat lung alveolar epithelial type II cells as revealed by immunoblot analysis. Proteolysis increases in the presence of phorbol 12-myristate 13-acetate (PMA), terbutaline, or ATP, agents that enhance secretion of lung surfactant from type II cells. Calpain, a calcium-dependent neutral protease, was activated in stimulated type II cells and cleaved purified annexin I at the N-terminus minus 26 amino acids. Liposome aggregation activity of truncated annexin I showed ten-fold increase in calcium sensitivity compared to the native form. The results suggest that proteolytic modification may be a regulatory mechanism for annexin I to mediate the secretory processes of alveolar type II cells at physiological calcium concentrations.
免疫印迹分析显示，膜联蛋白I在完整的大鼠肺II型肺泡上皮细胞中会发生内源性有限蛋白水解。在佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）、特布他林或ATP存在的情况下，蛋白水解作用增强，这些物质可促进II型细胞肺表面活性物质的分泌。钙蛋白酶是一种钙依赖性中性蛋白酶，在受刺激的II型细胞中被激活，并在膜联蛋白I的N端减去26个氨基酸处将其切割。与天然形式相比，截短的膜联蛋白I的脂质体聚集活性在钙敏感性上提高了10倍。结果表明，蛋白水解修饰可能是膜联蛋白I在生理钙浓度下介导II型肺泡细胞分泌过程的一种调节机制。
