title: Immunohistochemical localization and characterization of a rat Clara cell 26-kDa protein (CC26) with similarities to glutathione peroxidase and phospholipase A2.
abstract: We have purified and partially sequenced a 26-kDa protein isolated from rat lung lavage. Two-dimensional electrophoresis and Western blotting using an antibody we have raised to this protein indicated that CC26 has 3 isoforms with pIs between 4.9 and 5.5 and is neither a component of surfactant nor present in plasma. The first 10 amino acids of the N-terminal of all 3 isoforms were identical. The first 25 amino acids of the N-terminal sequence were identical to a rat acidic calcium-independent phospholipase A2 and one amino acid different from a mouse nonselenium glutathione peroxidase. Light immunohistochemistry showed a strong reaction with the airway hypophase from the trachea down to the terminal bronchioles, but not in the alveolus. Immunohistochemistry at the electron microscopy level showed that CC26 was localized to the dense secretory bodies and endoplasmic reticulum of the Clara cell and secretory granules of tracheal nonciliated serous and goblet cells. Heavily labeled Clara cell dense secretory bodies were observed in the process of being exocytosed. Biochemical and further sequence analysis will be required to determine if this protein is either a nonselenium glutathione peroxidase or a calcium-independent phospholipase A2.
authors.affiliation: Department of Human Physiology, School of Medicine, Flinders University of South Australia, Bedford Park, Australia.
authors.forename: J H
authors.initials: JH
authors.lastname: Power
authors.forename: T E
authors.initials: TE
authors.lastname: Nicholas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001980:Bronchi / Q000737:chemistry* / Q000166:cytology; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology*; D002846:Chromatography, Affinity; D015180:Electrophoresis, Gel, Two-Dimensional; D005979:Glutathione Peroxidase / Q000032:analysis*; D054522:Group VI Phospholipases A2; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010741:Phospholipases A / Q000032:analysis*; D054467:Phospholipases A2; D011506:Proteins / Q000032:analysis* / Q000276:immunology / Q000302:isolation & purification; D011650:Pulmonary Alveoli / Q000737:chemistry* / Q000166:cytology; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D017386:Sequence Homology, Amino Acid; D014598:Uteroglobin
chemical_list: D011506:Proteins; C556389:SCGB1A1 protein, human; C556390:Scgb1a1 protein, mouse; C556391:Scgb1a1 protein, rat; D014598:Uteroglobin; D005979:Glutathione Peroxidase; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; D054467:Phospholipases A2; C516476:Pla2g6 protein, mouse