Regulation of annexin I by proteolysis in rat alveolar epithelial type II cells.
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.
Liu
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Institute For Environmental Medicine, University of Pennsylvania, School of Medicine, Philadelphia 19104, USA.
Fisher
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Zimmerman
U J
UJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017305:Annexin A1 / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D015151:Immunoblotting; D008081:Liposomes / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013726:Terbutaline / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D017305:Annexin A1; D008081:Liposomes; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D005341:Fibrinolysin; D002402:Cathepsin D; D013726:Terbutaline; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium