F Barr

Publications (2)0 Total impact

• Article: Localization of a candidate surfactant convertase to type II cells, macrophages, and surfactant subfractions.

  H Clark, L Allen, E Collins, F Barr, L Dobbs, G Putz, J Goerke, S Hawgood
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  ABSTRACT: Pulmonary surfactant exists in the alveolus in several distinct subtypes that differ in their morphology, composition, and surface activity. Experiments by others have implicated a serine hydrolase in the production of the inactive small vesicular subtype of surfactant (N. J. Gross and R. M. Schultz. Biochim. Biophys. Acta 1044: 222-230, 1990). Our laboratory recently identified this enzyme in the rat as the serine carboxylesterase ES-2 [F. Barr, H. Clark, and S. Hawgood. Am. J. Physiol. 274 (Lung Cell. Mol. Physiol. 18): L404-L410, 1998]. In the present study, we determined the cellular sites of expression of ES-2 in rat lung using a digoxygenin-labeled ES-2 riboprobe. ES-2 mRNA was localized to type II cells and alveolar macrophages but not to Clara cells. Using a specific ES-2 antibody, we determined the protein distribution of ES-2 in the lung by immunohistochemistry, and it was found to be consistent with the sites of mRNA expression. Most of the ES-2 in rat bronchoalveolar lavage is in the surfactant-depleted supernatant, but ES-2 was also consistently localized to the small vesicular surfactant subfraction presumed to form as a consequence of conversion activity. These results are consistent with a role for endogenous lung ES-2 in surfactant metabolism.
  The American journal of physiology 04/1999; 276(3 Pt 1):L452-8.
• Article: Identification of a putative surfactant convertase in rat lung as a secreted serine carboxylesterase.

  F Barr, H Clark, S Hawgood
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  ABSTRACT: In the alveolar lumen, pulmonary surfactant converts from the contents of secreted lamellar bodies to tubular myelin to apoprotein-depleted vesicles during respiration. Using an in vitro system, researchers have reported that the conversion of tubular myelin to vesicles is blocked by inhibitors of serine hydrolase activity and have tentatively ascribed "convertase" activity to a diisopropyl fluorophosphate (DFP)-binding protein in mouse bronchoalveolar lavage (BAL). We purified and sequenced the homologous enzyme from rat BAL fluid. Amino acid sequence from the amino terminus and an internal cyanogen bromide peptide of the purified rat DFP-binding protein perfectly match the sequence of the carboxylesterase ES-2. Although ES-2 was initially cloned from liver, we found a 1.8-kilobase mRNA for ES-2 in decreasing relative abundance in rat liver, kidney, and lung but not in heart or spleen. Although further studies are required to establish the identity between "convertase" and ES-2 or a homologous member of the carboxylesterase family, our results raise the possibility that a protein with esterase/lipase activity plays a role in extracellular surfactant metabolism.
  The American journal of physiology 03/1998; 274(3 Pt 1):L404-10.