Differential effects of glucocorticoid on expression of surfactant proteins in a human lung adenocarcinoma cell line.
Synthesis of pulmonary surfactant-associated glycoproteins of Mr 28,000-36,000 (SP-A) and Mr 42,000-46,000 (proSP-B) has been identified in a continuous cell line derived from a human lung adenocarcinoma. SP-A was detected by immunoblot analysis, ELISA assay and by [35S]methionine labelling of the cells. SP-A was secreted into the media as an endoglycosidase F sensitive glycoprotein which co-migrated with the isoforms of SP-A identified in human lavage fluid by 2D-IEF-SDS-PAGE. Hybridization of cellular RNA with SP-A-specific cDNA identified an abundant 2.2 kb mRNA species, identical to that observed in human lung. SP-A RNA and protein content were markedly inhibited by dexamethasone in a dose-dependent fashion. Under identical culture conditions, synthesis of a distinct surfactant protein, SP-B, was markedly stimulated by the glucocorticoid. The SP-B precursor was secreted into the media as heterogeneous Mr 42,000-46,000 protein, pI 4.6-5.1, and was sensitive to endoglycosidase F. Synthesis of proSP-B was enhanced by the glucocorticoid in a dose-dependent fashion and was associated with increased SP-B mRNA of 2.0 kb detected by Northern blot analysis. The cell line secreted proSP-B as Mr 42,000-46,000 glycosylated protein and did not process the precursor to the Mr 7000-8000 surfactant peptide. In summary, a human adenocarcinoma cell line has been identified which synthesizes and secretes two surfactant-associated proteins, SP-A and proSP-B. Glucocorticoid enhanced SP-B but inhibited SP-A expression in this cell line. The identification of a continuous cell line secreting surfactant proteins may be useful in the study of synthesis and secretion of these important proteins and for production of the proteins for clinical uses.
O'Reilly
M A
MA
University of Cincinnati College of Medicine, Department of Pediatrics, OH 45267-0541.
Gazdar
A F
AF
Morris
R E
RE
Whitsett
J A
JA
D000230:Adenocarcinoma / Q000378:metabolism* / Q000648:ultrastructure; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms / Q000378:metabolism* / Q000648:ultrastructure; D011498:Protein Precursors / Q000096:biosynthesis; D011663:Pulmonary Surfactants / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012334:RNA, Neoplasm / Q000302:isolation & purification
D011498:Protein Precursors; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D003907:Dexamethasone