title: A novel surfactant protein C L55F mutation associated with interstitial lung disease alters subcellular localization of proSP-C in A549 cells.
abstract: BACKGROUND
  Heterozygous mutations of SFTPC, the gene-encoding surfactant protein C (SP-C), result in interstitial lung disease (ILD). However, characterization of mutations located in the mature domain of precursor SP-C (proSP-C) is limited. This study examined the molecular pathogenesis of such a mutation of ILD.
  
  
  METHODS
  We employed sequencing of SFTPC and established A549 cells stably expressing several proSP-C mutants. Histopathology and transmission electron microscopy (TEM) of lung tissue from a pediatric patient with ILD were assessed. Effects of mutant proSP-C were evaluated by western blotting, immunofluorescence, and TEM.
  
  
  RESULTS
  Sequencing of SFTPC revealed a novel heterozygous mutation, c.163C>T (L55F). In lung tissue, abnormal localization of proSP-C was observed by immunohistochemistry, and small and dense lamellar bodies (LBs) in type II alveolar epithelial cells (AECs) were detected by TEM. TEM of A549 cells stably expressing proSP-C(L55F) displayed abnormal cytoplasmic organelles. ProSP-C(L55F) exhibited a band pattern similar to that of proSP-C(WT) for processed intermediates. Immunofluorescence studies demonstrated that proSP-C(L55F) partially colocalized in CD63-positive cytoplasmic vesicles of A549 cells, which was in contrast to proSP-C(WT).
  
  
  CONCLUSIONS
  We detected a novel c.163C>T mutation located in the mature domain of SFTPC associated with ILD that altered the subcellular localization of proSP-C in A549 cells.
authors.affiliation: Department of Pediatrics, Shinshu University School of Medicine, Nagano, Japan.
authors.forename: Tingting
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, Nagano, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sano
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, Nagano, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Ogiwara
authors.affiliation: Department of Pediatrics, Shinshu University School of Medicine, Nagano, Japan.
authors.forename: Norimoto
authors.initials: N
authors.lastname: Kobayashi
mesh_terms: D056809:Alveolar Epithelial Cells / Q000737:chemistry / Q000648:ultrastructure*; D019943:Amino Acid Substitution; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000737:chemistry; D005091:Exons / Q000235:genetics; D005260:Female; D006579:Heterozygote; D006801:Humans; D007223:Infant; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D016040:Lung Transplantation; D008247:Lysosomes / Q000737:chemistry; D008854:Microscopy, Electron; D020125:Mutation, Missense; D017354:Point Mutation; D011498:Protein Precursors / Q000032:analysis; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011649:Pulmonary Alveolar Proteinosis / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D011650:Pulmonary Alveoli / Q000473:pathology; D037721:Pulmonary Surfactant-Associated Protein C / Q000032:analysis / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D011859:Radiography; D011994:Recombinant Proteins / Q000032:analysis; D017422:Sequence Analysis, DNA; D013347:Subcellular Fractions / Q000737:chemistry; D014162:Transfection
chemical_list: D011498:Protein Precursors; D037721:Pulmonary Surfactant-Associated Protein C; D011994:Recombinant Proteins; C489679:SFTPC protein, human