title: Regulation of annexin I by proteolysis in rat alveolar epithelial type II cells.
abstract: 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.
authors.affiliation: Institute For Environmental Medicine, University of Pennsylvania, School of Medicine, Philadelphia 19104, USA.
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: A B
authors.initials: AB
authors.lastname: Fisher
authors.forename: U J
authors.initials: UJ
authors.lastname: Zimmerman
mesh_terms: 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
chemical_list: D017305:Annexin A1; D008081:Liposomes; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D005341:Fibrinolysin; D002402:Cathepsin D; D013726:Terbutaline; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium