Expression of a human surfactant protein C mutation associated with interstitial lung disease disrupts lung development in transgenic mice.
Surfactant Protein C (SP-C) is a secreted transmembrane protein that is exclusively expressed by alveolar type II epithelial cells of the lung. SP-C associates with surfactant lipids to reduce surface tension within the alveolus, maintaining lung volume at end expiration. Mutations in the gene encoding SP-C (SFTPC) have recently been linked to chronic lung disease in children and adults. The goal of this study was to determine whether a disease-linked mutation in SFTPC causes lung disease in transgenic mice. The SFTPC mutation, designated g.1728 G --> A, results in the deletion of exon4, generating a truncated form of SP-C (SP-C(Deltaexon4)). cDNA encoding SP-C(Deltaexon4) was constitutively expressed in type II epithelial cells of transgenic mice. Viable F0 transgene-positive mice were not generated after two separate rounds of pronuclear injections. Histological analysis of lung tissue harvested from embryonic day 17.5 F0 transgene-positive fetuses revealed that SP-C(Deltaexon4) caused a dose-dependent disruption in branching morphogenesis of the lung associated with epithelial cell cytotoxicity. Transient expression of SP-C(Deltaexon4) in isolated type II epithelial cells or HEK293 cells resulted in incomplete processing of the mutant proprotein, a dose-dependent increase in BiP transcription, trapping of the proprotein in the endoplasmic reticulum, and rapid degradation via a proteasome-dependent pathway. Taken together, these data suggest that the g.1728 G --> A mutation causes misfolding of the SP-C proprotein with subsequent induction of the unfolded protein response and endoplasmic reticulum-associated degradation pathways ultimately resulting in disrupted lung morphogenesis.
Bridges
James P
JP
Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
Wert
Susan E
SE
Nogee
Lawrence M
LM
Weaver
Timothy E
TE
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005091:Exons; D017353:Gene Deletion; D006360:Heat-Shock Proteins; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D050356:Lipid Metabolism; D008156:Luciferases / Q000378:metabolism; D008168:Lung / Q000254:growth & development* / Q000473:pathology; D008171:Lung Diseases / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D018832:Molecular Chaperones / Q000235:genetics; D009154:Mutation; D010455:Peptides / Q000235:genetics* / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D017510:Protein Folding; D021381:Protein Transport; D037721:Pulmonary Surfactant-Associated Protein C; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D019076:Transgenes
D002352:Carrier Proteins; D018076:DNA, Complementary; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D036341:Intercellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D010455:Peptides; D037721:Pulmonary Surfactant-Associated Protein C; C489679:SFTPC protein, human; C489680:Sftpc protein, mouse; D004247:DNA; D008156:Luciferases